Mechanomics: an emerging field between biology and biomechanics

Abstract

Cells sense various in vivo mechanical stimuli, which initiate downstream signaling to mechanical forces. While a body of evidences is presented on the impact of limited mechanical regulators in past decades, the mechanisms how biomechanical responses globally affect cell function need to be addressed. Complexity and diversity of in vivo mechanical clues present distinct patterns of shear flow, tensile stretch, or mechanical compression with various parametric combination of its magnitude, duration, or frequency. Thus, it is required to understand, from the viewpoint of mechanobiology, what mechanical features of cells are, why mechanical properties are different among distinct cell types, and how forces are transduced to downstream biochemical signals. Meanwhile, those in vitro isolated mechanical stimuli are usually coupled together in vivo, suggesting that the different factors that are in effect individually could be canceled out or orchestrated with each other. Evidently, omics analysis, a powerful tool in the field of system biology, is advantageous to combine with mechanobiology and then to map the full-set of mechanically sensitive proteins and transcripts encoded by its genome. This new emerging field, namely mechanomics, makes it possible to elucidate the global responses under systematically-varied mechanical stimuli. This review discusses the current advances in the related fields of mechanomics and elaborates how cells sense external forces and activate the biological responses.

Protein Cell 2014, 5(7):518531DOI 10.1007/s13238-014-0057-9 Protein& Cell

REVIEW

Mechanomics: an emerging eld between biology and biomechanics

Jiawen Wang, Dongyuan L, Debin Mao, Mian Long&

Center for Biomechanics and Bioengineering and Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China& Correspondence: [email protected] (M. Long)

Received January 6, 2014 Accepted March 10, 2014

Protein&Cell

ABSTRACT

Cells sense various in vivo mechanical stimuli, which initiate downstream signaling to mechanical forces. While a body of evidences is presented on the impact of limited mechanical regulators in past decades, the mechanisms how biomechanical responses globally affect cell function need to be addressed. Complexity and diversity of in vivo mechanical clues present distinct patterns of shear ow, tensile stretch, or mechanical compression with various parametric combination of its magnitude, duration, or frequency. Thus, it is required to understand, from the viewpoint of mechanobiology, what mechanical features of cells are, why mechanical properties are different among distinct cell types, and how forces are transduced to downstream biochemical signals. Meanwhile, those in vitro isolated mechanical stimuli are usually coupled together in vivo, suggesting that the different factors that are in effect individually could be canceled out or orchestrated with each other. Evidently, omics analysis, a powerful tool in the eld of system biology, is advantageous to combine with mechanobiology and then to map the full-set of mechanically sensitive proteins and transcripts encoded by its genome. This new emerging eld, namely mechanomics, makes it possible to elucidate the global responses under systematically-varied mechanical stimuli. This review discusses the current advances in the related elds of mechanomics and elaborates how cells sense external forces and activate the biological responses.

KEYWORDS mechanomics, mechanobiology, proteomics, transcriptomics

INTRODUCTION

Mechanical stimuli are crucial to many biological processes at organ, tissue, cell, and molecule levels. Shear ow, tensile stretch, and mechanical compression are most typical in vivo mechanical stimuli, which are in action alone or synergistically with other mechanical and even biochemical factors (Wang, 2006; Cohen and Chen, 2008). For example, endothelial cells are subjected to blood shear ow and orientated towards the ow direction (Silkworth and Stehbens, 1975), extracellular matrices (ECMs) are stretched to mediate the outside-in signaling (Wright et al., 1997), and cartilage tissue is compressed to initiate interstitial uid pressurization (Soltz and Ateshian, 2000). A body of cues is known about how these mechanical stimuli affect cell morphology, proliferation, and differentiation. Evidently, it is difcult to elucidate what really happen at cellular and molecular levels if only a single type of mechanical stimuli or one set ofmechanical parameters ata given stimulus is used.

Homeostatic imbalances are main driving forces to initiate physiological changes, in which various stimuli are monitored closely by receptors and sensors at different sites. Most of mechanoreceptors often react to shear ow, tensile stretch, or mechanical compression. When multiple mechanical stimuli or parameters are pooled together, part(s) of those molecular events presented in individual stimuli tests might be reserved constantly, fostered cooperatively, or canceled out each other, since the cross-talks existing in the mechanically sensitive genes and proteins would exert null, synergistic, or opposite effects. Thus, global mapping of activated genes and proteins that are responsible to the specic mechanical stimuli is required to conduct from the viewpoint of omics. In this review, cellular and molecular responses to mechanical stimuli were discussed, and the new conceptual terminology of mechanomics referred to

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn

Mechanomics between biology and biomechanics REVIEW

A

B

Cell 1

Cell 2

Cell 3

High

Low

F

Cell 5

Cell 8

Cell 10

Cell 6

Cell 4

Cell 7

Cell 3

Cell 2

Cell 1

Cell 9

High

Low

F1

F2

F3

Figure 1. Schematic of cellular responses to mechanical stimuli in one-to-more (A) or more-to-one pattern (B). Each row of the heatmap represents different genes, of which the abundance is indicated by top-right color key, and each column of the heatmap denotes distinct cells (A) and different mechanical forces (B).

Protein&Cell

F10 F8 F7 F4 F5 F6 F3 F1 F9 F2

transcriptomics and proteomics combined with systematically-varied mechanical stimuli was proposed.

MECHANOBIOLOGY AND TRANSCRIPTOMICS/ PROTEOMICS

Mechanobiology is an interdisciplinary eld at the interface of mechanics and biology that emerges over last two decades (Wang et al., 2008). It focuses on elucidating the mechanisms how external forces or changes in cell or tissue mechanical environment contribute to development, physiology, and disease of an organism. A major challenge in this eld is to elucidate the molecular mechanisms of mechanotransduction, by which cells sense and respond to bio-mechanical signals and convert them into biochemical signals (Katsumi et al., 2004; Long et al., 2011; Dado et al., 2012). Numerous mechanoreceptors, such as ECM molecules, transmembrane proteins, cytoskeleton, nuclei, and lipid bilayer, are mechanically sensitive and then initiate inside-out or outside-in mechanotransduction for cells (Janmey and McCulloch, 2007). A single type of mechanical stimuli in vitro often provokes cells sensing and responding to external forces via multiple molecular events (Fig. 1A). By contrast, multiple types of mechanical stimuli are present around a cell or cells in vivo and act on the cell(s) synergistically (Fig. 1B). It is also noticed that the physiological stimuli are usually dynamic rather than static, which highly depends

on the magnitude, frequency, and duration of mechanical forces.

On the other hand, omics is the most striking tool to globally map the cellular and molecular responses to various biochemical and biomechanical stimuli. It aims, from the viewpoint of system biology, at the characterization and quantication of pooled biological molecules that transmit external signals to alter the structure, function, and dynamics of an organism or organisms. Integration of existing approaches in biomechanics and high-throughput transcriptomics/proteomics enables us to prole cell phenotype under complicated mechanical stimuli and to elucidate the mechanisms in cell type-specic mechanobiology (Davies et al., 2005). Current efforts mainly focus on understanding the transcriptomics/proteomics on the pattern or parametric dependence of one specic type or on the combined types in respective pattern or parameter sets. Here we discuss the combination of these two elds along typical mechanical clues where the detailed parameters are summarized in Table 1 for clarity.

Mechanical modeling of a cell

Cells sense their mechanical environment, which, in turn, regulates their functions. Various theoretical models are proposed to understand mechanical regulation of cell functions, which provide differential mathematical solutions. At subcellular level, most models are attempting to predict the force or stress distribution of cytoskeletal network and mimic the remodeling of mechanically sensitive cytoskeletal proteins (Ingber, 1997; Li, 2008; Geiger et al., 2009). At cellular level, a cell is usually modeled as an encapsulated lipid membrane containing stress-supported structures to support its deformation, adhesion, and spreading (Evans and Yeung, 1989; Stamenovic and Ingber, 2002; Murrell et al., 2011). At tissue level, mathematically models are developed to predict the dynamics of tumor growth (Chaplain et al., 2006) and osteogenic differentiation (Carter et al., 1998) under mechanical stimuli. These models also help to elucidate the mechanisms how cells resist shape distortion and maintain their structural stability and how they convert mechanical signals into biochemical responses. Regardless of their advantages in theoretical prediction, these models are still required to compare with the relevant experimental measurements.

Single type of mechanical stimuli

Current works on mechanobiology and mechanotransduction are mainly focused on understanding how the cells sense and respond to a single type of mechanical stimuli and what the functional molecules are only on the basis of a few protein effectors.

Shear ow

Cellular responses to shear ow that mimics the physiological blood or interstitial ow are extensively investigated

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn 519

REVIEW Jiawen Wang et al.

StimuliTypesPatternParametersActingcells/tissuesRelatedmoleculesReferences

ActinPoratetal.(2011)

Lietal.(2005)

Wardetal.(2007)

Karjalainenetal.

(2003)

ShearowIsolatedLaminar/steady1020dyne/cm2 , 324hECsIntegrins,Flk-1,GPCRs,

PECAM-1

12dyne/cm2 ,24hECsTie2,Flk-1,MMP1Chenetal.(2001)

515dyne/cm2 ,24hECsPDGF-BB,TGF-1,LaminAQietal.(2011)

15dyne/cm2 , 06hECsPKA,PECAM-1,VEGFR2Wangetal.(2009)

12dyne/cm2 , 424hECs,SMCsICAM-1Heydarkhan-Hagvall

etal.(2006)

3dyne/cm2 ,6hMSCsAnnexin,GAPDHYietal.(2010)

1236dyne/cm2 ,40minMyelomaARH-77

cells

Oscillatory10dyne/cm2 ,1Hz,1hMSCsRunx2,Sox9,PPARArnsdorfetal.(2009)

12dyne/cm2 ,1Hz,1hOsteoblastsPGE2Maloneetal.(2007)

550dyne/cm2 ,0.52Hz,1

4 h

OsteocytesCOX-2,RANKL,OPGLietal.(2012)

Protein&Cell

Pulsating0.41.0dyne/cm2 ,5Hz,1hOsteocytesNOTanetal.(2007)

CombinedTurbulentw/laminarECsDNAsynthesisDaviesetal.(1986)

ECsVCAM-1,HSP70Brooksetal.(2002)

w/equibiaxialstretchFibroblastsFibronectinStewardetal.(2011)

w/cycliccompressionMSCsGlycosaminoglycan,Col-IISchattietal.(2011)

TensilestretchIsolatedUniaxial20%,26daysFibroblastsEGFLetal.(2013)

2%3%,0.1Hz,48hCartilageIGF-IBonassaretal.

(2001)

10%,0.1Hz,1hTenocytesCol-I/II,MMP-14,Wnt5AJiangetal.(2011)

3%9%,0.5Hz,3daysMSCsRunx2Shietal.(2011)

5%,1Hz,24hMSCsBGH3,CNN3Kurpinskietal.(2009)

Intermittent3%5%,0.5Hz,2h/day,

28days

MSCsSialoprotein-2,

Biaxial20%,1Hz,2448hSMCsMAPKRichardetal.(2007)

010%,0.3Hz,1hSMCsCyr61Tamuraetal.(2001)

15%,0.3Hz,124hSMCsCyr61,VEGF-A,MMP-1Yangetal.(2008)

2%,0.2Hz,7daysESCsRunx2,Sox9Lietal.(2013a)

8%,1Hz,2hChondrocyteseEF1D,ERKPilttietal.(2008)

Equiaxial6%14%,9daysACLPro-MMP-2Zhouetal.(2005)

3%12%,1Hz,224hAstrocytesTGF-,p53,ANXA4Rogersetal.(2012)

CombinedUniaxialw/equiaxialSMCsRacKatsumietal.(2002)

w/hydrostaticpressureChondrosarcoma

cells

Osteocalcin,Osterix

PDGF-B,Integrin,

MMP-3,TGF-

Table1.Summariesofmechanotransductionundertypicalmechanicalstimuli

520 The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn

Mechanomics between biology and biomechanics REVIEW

Osteonectin,Fibronectin,c-junSironenetal.(2002)

MMP-3,MMP-13,14-3-3Priametal.(2013)

HSP70,KNAT1,EF1-aKimbroughetal.

(2004)

Reorientation90,30minArabidopsisGAPDH,P450Moseykoetal.(2002)

Herranzetal.(2012)

StimuliTypesPatternParametersActingcells/tissuesRelatedmoleculesReferences

IsolatedStatic30MPa,6hChondrocytesHSP70Kaarnirantaetal.

(2003)

30MPa,024hChondrocytesDAP3,PTZ-17,H-NUC,HSP70Sironenetal.(2000)

30MPa,6hChondrosarcoma

cells

Cyclic530MPa,00.5Hz,20hChondrocytesProteoglycanLammietal.(1994)

1.67MPa,1Hz,24hOsteoblasts/

20N,2HzBonesRaf1,PDCD8Lietal.(2011)

Intermittent8kPa,0.33Hz,4h/day,

7days

MPCsProteoglycan,CollagenAngeleetal.(2004)

30min/day,5daysMalevolunteersfMLP,TNF-,CD62LFeuereckeretal.

(2013)

Reorientation5daysOsteoblastsActin,VimentinLietal.(2010)

Reorientation135,060minArabidopsisroot

apex

Rotation12rpm,2472hLymphoblastoidcellsmiR-150,miR-34a,EGR2,ETS1Mangalaetal.(2011)

Diamagnetic

levitation

5daysMSCsRunx2,3-tubulin,Actin,VimentinLietal.(2013c)

Pits,Grooves1421daysMSCsMAPK,FGF,PDGFDalbyetal.(2008)

Biggsetal.(2008)

Xuetal.(2008)

5 102 g,122daysDrosophilaP450-6a8,HSP70,Peroxiredoxin

2540

Hydroxyapatite24daysOsteoblastsMyosin-9,Filamin-B,Vimentin,

Colin-1

Osteocytes

Grooves24hFibroblastsEEF1D,IDH3,UCHL1,PCNAMcNamaraetal.

(2012)

Magneticbead0.5mT,1Hz,6hMyoblastsGalectin-1,AnnexinIII,RhoGDIGrossietal.(2011)

Protein&Cell

ACL,anteriorcruciateligament;EC,endothelialcell;MPC,mesenchymalprogenitorcell;MSC,mesenchymalstemcell;SMC,smoothmusclecell.

MicrogravitystimulationHead-down-tiltbed

test

Topography/stiffness/sizePillar,Groove,PA

gel

Table1continued

Mechanical

compression

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn 521

REVIEW Jiawen Wang et al.

(Liang et al., 2008; Cui et al., 2011; Fu et al., 2011a; Kang et al., 2012). Exposure of live cells to shear ow induces remarkable changes in cell morphology, adhesion, and spreading (Yang et al., 2009; Zhan et al., 2012). For example, endothelial cells (ECs) display adaptive remodeling in response to shear stress, under which surface mechano-sensors of integrins, Flk-1, ion channels, GPCRs, and PECAM-1 are involved in sensing shear stress (Li et al., 2005; Barakat and Lieu, 2003). Steady ow enforces myeloma cells to form actin-rich but microtubule-lacking protrusions in a stress-dependent pattern (Porat et al., 2011). Osteocytes subjected to pulsating ow appear to be more responsive than osteoblasts or periosteal broblast osteocytes in inhibiting osteoclast formation and resorption via NO-dependent pathways (Tan et al., 2007). Shear-induced transportation of circulating tumor cells to the target site is the prerequisite for organ-specic metastasis under blood ow (Wirtz et al., 2011) and tumor cell invasion is usually promoted by interstitial uid affecting their interactions with stromal cells (Shieh et al., 2011).

Transcriptomic analysis is growing up in cell mechanobiology studies under uid ow in the past decades. A specic pattern or parameter setting of shear ow initiates the expression of multiple genes in various biological processes. For instance, gene expression prole of ECs subjected to laminar or steady ow proposes the signicant modulation of the genes involved in cell proliferation, ECM/cytoskeleton remodeling, angiogenesis, or in inammatory cytokines, stress response proteins, and signaling molecules (Chen et al., 2001). Oscillatory ow up-regulates the transcription factor expression (Runx2, Sox9, and PPAR) and induces osteogenic differentiation via RhoA and its effector protein ROCK II for the fate determination of mesenchymal stem cells (MSCs) (Arnsdorf et al., 2009). Meanwhile, different patterns or parameter settings of shear ow promote the distinct transcriptomic alternations since distinct gene pro-les and resultant phenotypes of ECs are observed between low-shear disturbed ow and high-shear laminar ow to identify >100 new genes (Brooks et al., 2002). Moreover, the physiological conditions or biochemical microenvironments that cells reside should be taken into account under blood ow. One example is that the monoculture of ECs up-regulates ICAM-1 expression but the co-culture of ECs and SMCs down-regulates ICAM-1 expression under laminar ow (Heydarkhan-Hagvall et al., 2006). TNF--induced gene expression is distinct from that induced by disturbed ow, implying that the downstream effect of disturbed ow is not mediated as same as the signaling pathways that activate NF-B (Brooks et al., 2002).

While much progresses have been achieved in transcriptomic analysis under shear ow, a few works are also done in proteomic proling of cells under shear stress. Under steady ow, 10 and 3 proteins are found to be up- and down-regulated for hMSCs, respectively, in which annexin A2 and GAPDH are substantially increased (Yi et al., 2010).

Besides, cells can also sense shear stress and convert it into secretary signals, as seen in 43 differential proteins found from low shear-induced rat thoracic aorta in which two secretary molecules of PDGF-BB and TGF-1 are critical in vascular remodeling (Qi et al., 2011). Again, the combination of biochemical factors with biomechanical stress is critical, since high glucose alone signicantly modulates shear-induced mechanosensing complexes and protein phosphorylation pathways of endothelium while both laminar shear and high glucose together enhance HSPs and protein ubiquitination of bovine ECs (Wang et al., 2009).

Tensile stretch

Mechanical stretch usually induces signicant changes in cellular responses and tissue remodeling at molecular and cellular levels (Tamura et al., 2001; Zhou et al., 2005; Richard et al., 2007). Static stretch induces asymmetric migration of keratinocytes cocultured with broblasts in a wound repairing model (L et al., 2013). Tendon broblasts sense cyclic stretch in the dose- and time-dependent patterns and induce protein productions (Col-I, TGF-1, COX, PGE2, and LTB4) (Wang, 2006). Equi-biaxial stretch promotes higher pro-MMP-2 production and its active form in anterior cruciate ligament than those in medial collateral ligament broblasts but no difference in post-translational modication is observed in between (Zhou et al., 2005). Transient increase of cysteine-rich protein 61 (Cyr61) mRNA is observed for fetal bovine bladder smooth muscle cells (SMCs) subjected to cyclic biaxial stretch, which is correlated with intracellular signaling (PKC, PI3K, and Rho kinase) (Tamura et al., 2001). Moreover, ion channels could serve as candidate mechanosensors, since cyclic stretch is able to trigger the gadolinium-sensitive stretch-activated ion channels, inducing a rapid Ca2+ inux, and then play a

crucial role in mechanotransduction of fetal rat lung cells (Liu et al., 1994) with specied structural alterations and gating dynamics (Martinac, 2004).

Gene expression is globally mapped under physiologically-mimicking stretch and a number of mammalian and plant genes reacting to mechanical stretch are identied. Different mechanosensitive genes are dened for the metabolism of chondrosarcoma cells exposed to continuous cyclic stretch (Karjalainen et al., 2003) or for the biochemically-induced osteogenesis and bone nodule formation of human ESCs exposed to intermittent cyclic stretch (Li et al., 2013a). In addition to obtaining a candidate list of the differential genes, integrative knowledge of proteins encoded by mechanosensitive genes and of their interactions with putative partners uncovers the programming of genes functionally involved in paracrine signaling of angiogenesis for bladder SMCs subjected to cyclic stretch (Yang et al., 2008). Nowadays, it is also able to prole plant transcriptomes and compare the genes of interest under mechanical stretch. The rst expression sequence tags of tension wood are

Protein&Cell

522 The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn

Mechanomics between biology and biomechanics REVIEW

produced from Populus tremula P. tremuloides tension wood cDNA library (Sterky et al., 2004) and four different cDNA libraries are then constructed from both tensile and opposite wood of bent poplars to identify the highly expressed genes from analyzing the tags in the libraries (Dejardin et al., 2004).

Differential proteins under mechanical stretch are also proled, especially for those events undetectable in transcriptomic analysis. Cyclic biaxial stretch initiates multiple phosphorylations associated with the newly-identied mechanosensitive proteins in chondrosarcoma cells (Piltti et al., 2008) and promotes 194 and 177 differential proteins related to ECM production, intracellular signaling, cytoskeletal remodeling, and inammatory response from tenocytes cultured on polyglycolic acid long bers, respectively (Jiang et al., 2011). Cyclic equiaxial stretch uncovers a few consistent major proteins (TGF-1, TNF, CASP3, and p53) to hub at the center of the interacting network with the newly-proled proteins of interest (BAG5, NO66, and eIF-5A) in activated lamina cribrosa cells (Rogers et al., 2012), recapitulating the importance of MAPK and TGF- signaling pathways in mechanotransduction. Biomechanical and biochemical regulations are also coupled together in stretch-induced proteins, as seen that the TGF-1-activated up-regulation of 31 integrin and uniaxial stretch-induced increase of calponin 3 protein are different from the synergistic up-regulation of calponin 1 gene for human MSCs (Kurpinski et al., 2009). In plant, 5 and 12 proteins are specied in the differentiating tissue of tension-induced wood in Eucalyptus camaldulensis L. (Baba et al., 2000) and in the tensile wood of Eucalyptus gunnii associated with growth strain (Plomion et al., 2003), respectively. Although the available data for plants is much less than those for mammals, such the mechanically-induced proteomic analysis broadens the mechanotransductive extents in plant sciences.

Mechanical compression

Cells are able to sense and respond to internal or external compression. Articular cartilage is a hydrated soft tissue for bearing diarthrodial joints and therefore serves as the main target in compression-induced mechanotransduction. Continuous hydrostatic pressure induces stress-associated transcription factors in primary and immortalized chondrocytes, presumably resulting from the stabilization but not the synthesis of HSP70 mRNA (Kaarniranta et al., 2003). Both dynamic compression and insulin-like growth factor I (IGF-I) regulate, via distinct activating pathways, the metabolic activity of articular chondrocytes in a way that dynamic compression accelerates the biosynthetic response to IGF-I and increases transport of IGF-I into the articular cartilage matrix (Bonassar et al., 2001). Tumor is another typical target mainly due to its uncontrolled growth in a conned space. Tumor cells often experience mechanical compressive stress that

stimulates adhesion and migration by a subset of leader cells (Tse et al., 2012) whereas tibial compression inhibits the growth and osteolysis of secondary breast tumors (Lynch et al., 2013). These studies provide cues for the potential signaling pathways in response to mechanical compression by these mechanosensitive effectors.

Differential gene expression under mechanical compression is one of key issues in chondrocyte mechanotransduction. Chondrosarcoma cells are more likely sensitive to continuous pressure with several induced genes than cyclic and static pressure with few gene changes under different compression regimens and parameters (Sironen et al., 2000). Not only the hydrostatic pressure regulates the gene expression but it also manipulates the mRNA stability of chondrosarcoma cells, since such immediate-early genes as c-jun, jun-B, and c-myc become up-regulated but destabilized under pressure treatment (Sironen et al., 2002).

Proteomic studies of mechanical compression are applied to understand how different proteins are orchestrated to respond. Proteomic analysis between normal and fatigue axial compressive loads for ulna yields 42 differential proteins encoded by 21 genes that produce an interaction subnetwork for differentially expressed proteins (mainly for Raf1 and PDCD8) (Li et al., 2011). Co-culture of osteoblastsosteocytes exposed to cyclic compression induces the protein release of MMP-3 and -13, inhibits the mRNA expression of Col-II and aggrecan, and promotes 14-3-3 as a new soluble mediator between subchondral bone and cartilage in osteoarthritis, implying the interactive communications among different types of bone cells (Priam et al., 2013). Moreover, cyclic compression also induces differential productions of typical proteins (aggrecan, Col-I/II, and proteoglycan) for bone marrow-derived mesenchymal progenitor cells (Angele et al., 2004).

Other mechanical stimuli

There are numerous other mechanical stimuli existing in physiology. Combination of both transcriptomic/proteomic analyses and mechanical loading is also important in those mechanical stimuli. Here are two examples.

Gravitational alterations in space are crucial for astronauts bone loss and immune suppression under micro-gravity, which highly depends on the direct and indirect effects of gravitational changes on the relevant cells observed from space missions or ground-based studies (Zayzafoon et al., 2005; Sun et al., 2008; Li et al., 2010; Feuerecker et al., 2013). While gravity-sensitive genes and proteins are occasionally found to be either up-regulated or down-regulated, there is still lack of systematic studies on gene expression and protein production for various types of cells exposed to different microgravity levels (Nichols et al., 2006). The pioneering works of whole-genome analysis on gravitropic stimulation are performed to delineate the

Protein&Cell

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn 523

REVIEW Jiawen Wang et al.

transcriptional response mechanisms of plant growth, where Arabidopsis seedlings and root apices in response to clinostat (90 reorientation) and transient gravitropic reorientation (135 reorientation) at different time points (260 min) reveal the induction of complex gene expression patterns as a consequence of the fast and transient transcriptional networks and the gravity-induced genes (Moseyko et al., 2002; Kimbrough et al., 2004). Later, the expression prole of microRNAs and genes of human lymphoblastoid cells on simulation of microgravity effect is conducted after being exposed to a rotating wall bioreactor, in which miR-150, miR-34a, miR-423-5p, miR-22, miR-141, miR-618, and miR-222 are found to change signicantly (Mangala et al., 2011). Diamagnetic levitation simulation veries the delay in the development of Drosophila melanogaster from embryo to adult and the signicant changes in the transcriptional prole of immune-, stress-, and temperature-related genes (i.e., HSPs) (Herranz et al., 2012), implying the gravity-dependent organism development.

There is an increasing evidence that cells respond to the topographical substrate with physiologically-mimicking stiffness in morphology, proliferation, and differentiation (Li et al., 2013c), suggesting that mechanical features of substrate also play a role in mechanobiology and alter cell transcriptomics/proteomics. Genetic prole of hMSCs presents the promotion of the topography-induced bone formation on nanoscale pitted surface and raised islands (Dalby et al., 2008) and yields a similar expression of p38 MAPK molecule on two width-varied microgrooves but a differential regulation of increased PDGF and integrin expressions and of enhanced VEGF signaling on either microgroove (Biggs et al., 2008). Quantitative proteomics on different topographies uncovers 21 differential proteins related to cell cyto-skeleton, metabolism, signaling, and growth identied for osteoblasts placed on planar and carbon nanotube reinforced hydroxyapatite surface (Xu et al., 2008). Further studies integrate the transcriptomics and proteomics analyses to provide the consistent data for transcripts and proteins of broblasts on grooved substrate in regulating chromatin remodeling (e.g., HMGA1) and DNA synthesis (e.g., PCNA) (McNamara et al., 2012). Additionally, ECM/cell stiffness is an intrinsic mechanical stimulus that can also regulate cell phenotype. As compared to those dispersed cells, periosteal cells residing in stiffness-varied regions yield the differential genes and the related proteins in regulating ECMs, suggesting a negative correlation between stiffness and differentiation (Horimizu et al., 2013). Mechanosensor-based targeting of membrane stiffness provokes 13 proteins involved in the differentiation of embryonic muscle cells, including galectin-1, annexin III, RhoGD I, and FAK phosphorylation (Grossi et al., 2011). Evidently, ECM/cell topography and stiffness are associated with transcriptomic/ proteomic changes in signaling pathways and cellular functions, as well as in metastatic potential of tumor cells (Pozo

et al., 2007; Swaminathan et al., 2011; Huang and Ingber, 2005).

Combined mechanical stimuli

Physiologically, the different types of mechanical stimuli or the variety of mechanical patterns or parameters on the same mechanical stimulus are usually coupled together to modulate the cellular and molecular events. Multiple genes and protein effectors are mediated to respond to the acting stimuli or parameters.

Differential regulation of patterns or parameters on single type of stimuli

Increasing evidences indicate that cells respond to mechanical stimuli in a pattern-dependent manner. For example, laminar shear induces EC alignment along the ow direction without initiating cell proliferation whereas turbulent shear stimulates endothelial DNA synthesis in the absence of cell alignment (Davies et al., 1986). Exposure of broblasts to oscillatory ow does not promote the development of F-actin stress bers while the actin polymerization and actin stress ber formation are fostered under steady ow (Malone et al., 2007). Meanwhile, equi-biaxial stretch inhibits lamellipodia formation via deactivation of Rac signaling whereas uniaxial stretch suppresses lamellipodia along lengthened sides but increases at adjacent ends (Katsumi et al., 2002). Cyclic pressure enhances the aggrecan mRNA expression while static pressure reduces the aggrecan level in primary chondrocytes (Lammi et al., 1994). Moreover, cells respond to mechanical stimuli in a parameter-dependent manner at a given pattern of specic type. Under oscillatory ow, COX-2, RANKL, and OPG mRNA expressions in osteocytes are sensitive to the combination of peak shear stress (0.5, 1, 2, and 5 Pa), oscillatory frequency (0.5, 1, and 2 Hz), and action duration (1, 2, and 4 h) (Li et al., 2012). Continuous tension at 3%9% strain for 10 days inhibits MSC differentiation while intermittent tension in minutes or hours per day promotes MSC differentiation via Runx2 expression and MAPK signaling (Ward et al., 2007; Shi et al., 2011). These data illustrates that cellular responses are highly sensitive to the patterns and/or parameters of mechanical stimuli that are imposed.

Combinatory impacts of different types of stimuli

Cells usually undergo in vivo distinct types of mechanical loads that are inextricably coupled and are put into effect synergistically. For example, biomechanical tests of torsion-tension of cadaveric femurs reveals the simultaneous, coupled impacts of mechanical torsion and tension (Zdero et al., 2011). Tensile strain amplication from tissue to cellular level in bone is induced by uid drag forces on bone cells (You et al., 2001), implying the cross-talk between tensile stretch and shear ow. When an equi-biaxial tension and a steady

Protein&Cell

524 The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn

Mechanomics between biology and biomechanics REVIEW

ow are applied separately to broblasts in the presence or absence of RhoA inhibitor, the mechanical stimuli regulate bronectin reorganization and recruitment in different ways (Steward et al., 2011). Obviously, one type of mechanical load alone is unlikely sufcient to generate the required mechanotransductive signaling events for a specic function phenotype. An example to echo this point is the combinatory regulations of surface shear (25 oscillation at 1 Hz) and cyclic axial compression (0.4 mm amplitude or 10%20% strain at 1 Hz) for chondrogenic differentiation of hBMSCs. Here the combination enables to mediate chondrogenic gene expression and sulphated glycosaminoglycan and Col-II deposit but either alone does not work (Schatti et al., 2011). Moreover, chondrosarcoma cells yield a less profound effect on the gene expression prole under hydrostatic pressure (continuous and 0.5 Hz cyclic pressure at 5 MPa) than that under cyclic stretch (8% strain at 0.5 Hz) (Karjalainen et al., 2003).

To date, cell mechanotransduction has attracted much attentions to understand, from both theoretical and experimental aspects, the mechanisms how a cell adapts the mechanical stimuli and how the mechanical microenvironments are remodeled. The progress in combining mechanobiology with omics approaches also demonstrates that omics analysis is efcient in screening mechanosensitive genes or proteins in various mechanical stimuli (Fig. 2).

PROGRESSES AND PERSPECTIVE OF MECHANOMICS

Omics approaches, such as transcriptomics and proteomics, are powerful system-level tools that can be applied not only in biology and medicine but also in mechanobiology. However, no system-level omics denition is proposed to summarize the roles of mechanical forces in biological processes, i.e., mechanome. Mapping the mechanome of cells furthers the understandings of mechanosensation and mechanotransduction. Brief discussion is conducted here since only few papers are currently published on this special topic.

Concept of mechanomics

The denition of mechanome is originated for globally elucidating the functions of mechanical forces existing in vivo at cellular and molecular scales (Lang, 2007; Song et al., 2012, 2013). It is then extended to describe the events in tissue, organ, or even whole organism, aiming to understand ultimately the roles of mechanical stress from nano- and micro- to macro-scopic viewpoints (Song et al., 2012). It is necessary to collect the information of mechanical force distribution at different levels, and map the cross-talks between mechanical forces and biological functions. This turns out to a new eld, mechanomics. The term mechanomics was rst proposed for

combining the nuclear magnetic resonance technique with bioinformatics strategies to characterize the protein-ligand interactions across large families of proteins (Sem et al., 2001). Evidently, such denition is distinct with what we discuss here. Regardless of this, the term can be borrowed for describing the mechanically-induced events at multiple levels. Fig. 2 demonstrates the conceptual owchart of this emerging eld. It seeks to understand the fundamental mechanical or physical processes that are common to biological function and to study how forces are transmitted and transduced to regulate biological responses. A similar term of physicomics was also proposed to deal with physical parameters such as pressure, temperature, electromagnetic elds etc. that are involved in cell, tissue, or physiology (van Loon, 2009). To date, quite a few works from the viewpoint of mechanomics are found on transcriptomic and proteomic analyses for the combined mechanical stimuli. Mapping the global responses is critical since multiple mechanical stimuli are associated with the multiple cellular and molecular events (Fig. 2).

Limited progresses in the elds related to mechanomics

Since the term mechanomics is proposed from a distinct viewpoint of drug design (Sem et al., 2001), it has been submerged away from the community of mechanobiology for a while. To date, only a few works are reported along the line described here. One example is that understanding the roles of mechanical forces and machinery (e.g., biological motors and polymerization of lament) opens the window to new strategies for molecular medicine (Wang et al., 2008; Huang et al., 2013). Two more examples are to map the mechanome of live stem cells using both uorescent microbeads and computational uid dynamics (CFD) simulation and to measure local strain elds in situ at the uid-cell interface, which provides mechanistic insights into the roles of mechanical forces in lineage commitment as it unfolds (Wang et al., 2008; Song et al., 2012, 2013). In fact, a body of works, such as those aforementioned, have already adopted the idea or concept of mechanomics to elucidate the cellular and molecular events on different mechanical stimuli even though the term mechanomics is not used explicitly.

Biomechanical and biological approaches appropriate for mechanomics

Biomechanical assays and techniques developed previously are able to be applied in mechanomics. Shear ow, tensile stretch, and mechanical compression are most frequently tested using in-house developed or commercial instruments such as parallel ow chamber, membrane-stretch apparatus, or osmotic/hydrostatic compression device. As indicated in the literatures (van Loon, 2009; Long et al., 2011), parallel or disk ow chamber is used to mimic physiological blood or interstitial ow, uni-, bi-, or equi-axial stretch apparatus is

Protein&Cell

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn 525

REVIEW Jiawen Wang et al.

Mechanical or physical stimuli

Cell

Types, patterns, parameters

Shear flow

n

l o

i

s

s

e

r

p

m

o

c

Tensile

stretch

Microgravity

Others

Soluble factors

Stiffness

Supporting Niche

cell ECM

Topography

Protein&Cell

Planar

Dimension

Topography

Stiff

Soft

Gravity

Stiffness

MECHANOBIOLOGY/ MECHANOCHEMISTRYThe effects of mechanical factors on molecule, cell, and tissue functions.

GENOME/ TRANSCRIPTOME/ PROTEOMEThe entire sets of DNA, RNA, and protein molecules of an organism.

MECHANOMEThe global fuctions of mechanical factors in an organism

Figure 2. Conceptual demonstration of mechanome to illustrate the combination of mechanobiology/mechanochemistry and genome/transcriptome/proteome. Different mechanical stimuli mediate distinct responsive functions at molecule, cell, or tissue level, while the omics techniques map the entire sets of molecular events of an organism. The combined eld helps to uncover globally the mysteries of mechanobiology and mechanochemistry from the viewpoint of omics analyses at different levels.

applied to initiate the substrate or ECM tension, and tubular or spheroidal compression device is employed to represent physiological compression. In addition to these approaches, micropipette suction assay applies forces on the cell or vacuole membrane by deforming them (Huang et al., 2004; Fu et al., 2011b). Optical tweezers utilize an optical gradient to trap and exert forces on refractive microbeads (Zhang et al., 2008; Sun et al., 2009; Li et al., 2013b) and magnetic

tweezers apply twisting forces via a magnetic eld to rmly-attached magnetic microbeads on cell surface (Grossi et al., 2011). Atomic force microscopy enables to quantify rupture force/bond lifetime of protein-protein interactions at single molecule level (L et al., 2006). Besides, microgravity simulators such as clinostat, rotating-wall bioreactor, random positioning machine, or magnetic levitation are considered to stimulate the space microgravity effects for ground-based

526 The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn

Mechanomics between biology and biomechanics REVIEW

species while hypergravity centrifuges are useful tools for mimicking the hypergravity impacts in space life sciences. Micro-patterned or micro-fabricated substrates are assumed to mimic the physiological topography of microenvironment or niche and then applied in mechanobiology studies of cell proliferation and differentiation (Li et al., 2013c). Meanwhile, coupling the typical uorescent assays such as uorescence resonance energy transfer with those mechanical assays also enables to visualize the intracellular in situ events under given mechanical stimuli.

Transcriptomic/proteomic approaches are also critical for the study of mechanomics. Much progress has been made from routine chip-based analysis to the advanced RNA-seq techniques (e.g., SAGE) or from conventional 2-D gel assay to the hi-tech proteomic techniques (e.g., iTRAQ, and LC-MS/MS).

Future perspectives of mechanomics

Mechanomics is a young but fast developing eld. Promising clues are emerging in its related aspects in recent years. The framework is exemplied in Fig. 2 to clarify how all these related elds can be linked together. While there should be lots of works to pursue, several potential issues are proposed from the above discussions.

Biological or physiological signicance yield the top priority in mechanomic studies. It is little known about how mechanical forces appearing in cell or tissue contribute to development, physiology, and diseases. Molecular mechanisms (e.g., mechanosensors) by which cells sense and respond to mechanical signals is the major challenge we are facing, since we are still far away to establish the responsive network under global mechanical stimuli. More biological models should be considered, as the biologists usually do, to broaden the vision of study for biological diversity. Expression proling under pathological mechanical conditions is another hotspot in the mechanobiology of tumor growth (Carey et al., 2012).

Replication of the in vivo mechanical patterns or parameters is also a prior challenge to conne the understanding how mechanomics works for cells. In a living organism, the in vivo mechanical environment is quite complicated and usually coupled with other physical and chemical factors. Thus, it is difcult to replicate the local biomechanical environment that surrounds cells or comprises tissues and is hard to determine the physiological mechanical patterns or parameters. Meanwhile, existing in vitro data for cells exposed to mechanical stimuli are usually compared with those under static culture conditions, which require the careful design of control cases that are expected to subtract reasonably background noises from measured signals. More attentions should also be paid for those stimuli not indicated here (e.g., vibration, sound, touch).

Developing new in vitro assays specic for mechanomics is also an important issue. New hi-tech techniques in related elds provide the opportunities for promoting the mechanomics. On-chip strain sensors developed by micro-

fabrication combined with mechanical tension promise to test small samples and mechanical loading in parallel, to reduce the labor-consumption, and to enhance testing efciency (MacQueen et al., 2012). Micro-fabricated composite material screening array is also able to determine the combined effects of substrate stretch, soluble cues, and matrix proteins on small populations of primary cells, which eventually enable us to prole gene expression from a single cell (Moraes et al., 2013). Meanwhile, the state-of-art techniques in biology direct the analyses of cells in situ or in vivo, or carry out immediately the post mortem to retain the features of the native environment. It is then possible to design appropriate in vitro experiments that critically test the most dominant mechanical characteristics existing in vivo. New hitech techniques of 2nd-generation sequencing or single-cell sequencing could be efcient candidates for mapping the mechanomics of various species (Lawrie et al., 2008).

Large-scale data mining and bioinformatics analysis are indispensable in this eld. To facilitate the integration of database, an open-access and downloadable mechanomics database should be created worldwide, serving as a web-based resource like NCBI that collates quantitative analyses of mechanomics. One key feature of the database is able to map globally the mechanical environment of cells and provide the quantitative information for transcripts and proteins from various sources. Another is the capability of large-scale, elaborated analyses with interactive interface for the users who attempt to mine the existing data or submit newly measured data using various search engines or experimental assays.

CONCLUSIONS

Combination of mechanobiology and transcriptomics/proteomics is an emerging eld for globally understanding the gene expression and protein production in response to multiple types of mechanical stimuli. Evidently, mechanomics is still in its embryonic stage. With the high-throughput analyses in transcriptomics and proteomics and the state-ofart techniques in biomechanics, one expects to dene the required mechanical variables and to provide an integrated prole of signaling events from the viewpoint of mechanome at molecular and cellular levels.

ACKNOWLEDGEMENTS

This work was supported by National Basic Research Program (973 Program) (No. 2011CB710904), National Natural Science Foundation (No. 31110103918), Strategic Priority Research Program grants XDA01030102 and XDA04020219, and National High Technology Research and Development Program grant 2011AA020109, and Knowledge Innovation Program grant KJCX2-YW-L08.

ABBREVIATIONS

2-D, two dimensional; ACL, anterior cruciate ligament; EC, endothelial cell; ECM, extracellular matrix; MPC, mesenchymal

Protein&Cell

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn 527

REVIEW Jiawen Wang et al.

progenitor cell; HSP, heat shock protein; IGF-I, insulin-like growth factor I; iTRAQ, isobaric tags for relative and absolute quantication; LC, liquid chromatograph; MS, mass spectrometry; MSC, mesenchymal stem cell; SAGE, serial analysis of gene expression; SMC, smooth muscle cell.

OPEN ACCESS

This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.

REFERENCES

Angele P, Schumann D, Angele M, Kinner B, Englert C, Hente R,

Fuchtmeier B, Nerlich M, Neumann C, Kujat R (2004) Cyclic, mechanical compression enhances chondrogenesis of mesenchymal progenitor cells in tissue engineering scaffolds. Biorheology 41:335346Arnsdorf EJ, Tummala P, Kwon RY, Jacobs CR (2009) Mechanically induced osteogenic differentiationthe role of RhoA, ROCKII and cytoskeletal dynamics. J Cell Sci 122:546553Baba K, Asada T, Hayashi T (2000) Relation between developmental changes on anatomical structure and on protein pattern in differentiating xylem of tension wood. J Wood Sci 46:17 Barakat AI, Lieu DK (2003) Differential responsiveness of vascular endothelial cells to different types of uid mechanical shear stress. Cell Biochem Biophys 38:323343Biggs MJP, Richards RG, McFarlane S, Wilkinson CDW, Oreffo ROC,

Dalby MJ (2008) Adhesion formation of primary human osteo-blasts and the functional response of mesenchymal stem cells to 330 nm deep microgrooves. J R Soc Interface 5:12311242 Bonassar LJ, Grodzinsky AJ, Frank EH, Davila SG, Bhaktav NR,

Trippel SB (2001) The effect of dynamic compression on the response of articular cartilage to insulin-like growth factor-I. J Orthop Res 19:1117Brooks AR, Lelkes PI, Rubanyi GM (2002) Gene expression proling of human aortic endothelial cells exposed to disturbed ow and steady laminar ow. Physiol Genomics 9:2741Carey SP, DAlfonso TM, Shin SJ, Reinhart-King CA (2012)

Mechanobiology of tumor invasion: engineering meets oncology. Crit Rev Oncol Hematol 83:170183Carter DR, Beaupre GS, Giori NJ, Helms JA (1998) Mechanobiology of skeletal regeneration. Clin Orthop 355:S41S55Chaplain MAJ, Graziano L, Preziosi L (2006) Mathematical modelling of the loss of tissue compression responsiveness and its role in solid tumour development. Math Med Biol 23:197229Chen BPC, Li YS, Zhao YH, Chen KD, Li S, Lao JM, Yuan SL, Shyy

JYJ, Chien S (2001) DNA microarray analysis of gene expression in endothelial cells in response to 24-h shear stress. Physiol Genomics 7:5563Cohen DM, Chen CS (2008) Mechanical control of stem cell differentiation. In: Bhatia S, Polak J (eds) StemBook. Harvard Stem Cell Institute, Cambridge, pp 116

Cui YH, Huo B, Sun SJ, Yang F, Gao YX, Pan J, Long M (2011) Fluid dynamics analysis of a novel micropatterned cell bioreactor. Ann Biomed Eng 39:15921605

Dado D, Sagi M, Levenberg S, Zemel A (2012) Mechanical control of stem cell differentiation. Regen Med 7:101116

Dalby MJ, Andar A, Nag A, Affrossman S, Tare R, McFarlane S,

Oreffo ROC (2008) Genomic expression of mesenchymal stem cells to altered nanoscale topographies. J R Soc Interface 5:10551065Davies PF, Remuzzi A, Gordon EJ, Dewey CF, Gimbrone MA (1986)

Turbulent uid shear-stress induces vascular endothelial-cell turnover in vitro. Proc Natl Acad Sci USA 83:21142117 Davies PF, Spaan JA, Krams R (2005) Shear stress biology of the endothelium. Ann Biomed Eng 33:17141718Dejardin A, Leple JC, Lesage-Descauses MC, Costa G, Pilate G

(2004) Expressed sequence tags from poplar wood tissuesa comparative analysis from multiple libraries. Plant Biol 6:5564 Evans E, Yeung A (1989) Apparent viscosity and cortical tension of blood granulocytes determined by micropipet aspiration. Biophys J 56:151160Feuerecker M, Feuerecker B, Matzel S, Long M, Strewe C,

Kaufmann I, Hoerl M, Schelling G, Rehm M, Chouker A (2013) Five days of head-down-tilt bed rest induces noninammatory shedding of L-selectin. J Appl Physiol 115:235242Fu CL, Tong CF, Dong C, Long M (2011a) Modeling of cell aggregation dynamics governed by receptorligand binding under shear ow. Cell Mol Bioeng 4:427441Fu CL, Tong CF, Wang ML, Gao YX, Zhang Y, Lu SQ, Liang SL,

Dong C, Long M (2011b) Determining beta(2)-integrin and intercellular adhesion molecule 1 binding kinetics in tumor cell adhesion to leukocytes and endothelial cells by a gas-driven micropipette assay. J Biol Chem 286:3477734787Geiger B, Spatz JP, Bershadsky AD (2009) Environmental sensing through focal adhesions. Nat Rev Mol Cell Biol 10:2133 Grossi A, Lametsch R, Karlsson AH, Lawson MA (2011) Mechanical stimuli on C2C12 myoblasts affect myoblast differentiation, focal adhesion kinase phosphorylation and galectin-1 expression: a proteomic approach. Cell Biol Int 35:579586Herranz R, Larkin OJ, Dijkstra CE, Hill RJ, Anthony P, Davey MR,

Eaves L, van Loon JJWA, Medina FJ, Marco R (2012) Microgravity simulation by diamagnetic levitation: effects of a strong gradient magnetic eld on the transcriptional prole of Drosophila melanogaster. BMC Genomics 13(1):52 Heydarkhan-Hagvall S, Chien S, Nelander S, Li YC, Yuan SL, Lao

JM, Haga JH, Lian I, Nguyen P, Risberg B et al (2006) DNA microarray study on gene expression proles in co-cultured endothelial and smooth muscle cells in response to 4-and 24-h shear stress. Mol Cell Biochem 281:115Horimizu M, Kawase T, Tanaka T, Okuda K, Nagata M, Burns DM,

Yoshie H (2013) Biomechanical evaluation by AFM of cultured human cell-multilayered periosteal sheets. Micron 48:110 Huang S, Ingber DE (2005) Cell tension, matrix mechanics, and cancer development. Cancer Cell 8:175176Huang J, Chen J, Chesla SE, Yago T, Mehta P, McEver RP, Zhu C,

Long M (2004) Quantifying the effects of molecular orientation and length on two-dimensional receptorligand binding kinetics. J Biol Chem 279:4491544923

Protein&Cell

528 The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn

Mechanomics between biology and biomechanics REVIEW

Huang C, Holfeld J, Schaden W, Orgill D, Ogawa R (2013) Mechano-therapy: revisiting physical therapy and recruiting mechanobiology for a new era in medicine. Trends Mol Med 19:555564

Ingber DE (1997) Tensegrity: the architectural basis of cellular mechanotransduction. Annu Rev Physiol 59:575599

Janmey PA, McCulloch CA (2007) Cell mechanics: integrating cell responses to mechanical stimuli. Annu Rev Biomed Eng 9:134

Jiang YK, Liu HW, Li H, Wang FJ, Cheng K, Zhou GD, Zhang WJ, Ye

ML, Cao YL, Liu W et al (2011) A proteomic analysis of engineered tendon formation under dynamic mechanical loading in vitro. Biomaterials 32:40854095Kaarniranta K, Elo MA, Sironen RK, Karjalainen HM, Helminen HJ,

Lammi MJ (2003) Stress responses of mammalian cells to high hydrostatic pressure. Biorheology 40:8792Kang YY, Lu SQ, Ren P, Huo B, Long M (2012) Molecular dynamics simulation of shear- and stretch-induced dissociation of P-selectin/PSGL-1 complex. Biophys J 102:112120Karjalainen HM, Sironen RK, Elo MA, Kaarniranta K, Takigawa M,

Helminen HJ, Lammi MJ (2003) Gene expression proles in chondrosarcoma cells subjected to cyclic stretching and hydro-static pressure. A cDNA array study. Biorheology 40:93100 Katsumi A, Milanini J, Kiosses WB, del Pozo MA, Kaunas R, Chien

S, Hahn KM, Schwartz MA (2002) Effects of cell tension on the small GTPase Rac. J Cell Biol 158:153164Katsumi A, Orr AW, Tzima E, Schwartz MA (2004) Integrins in mechanotransduction. J Biol Chem 279:1200112004 Kimbrough JM, Salinas-Mondragon R, Boss WF, Brown CS,

Sederoff HW (2004) The fast and transient transcriptional network of gravity and mechanical stimulation in the Arabidopsis root apex. Plant Physiol 136:27902805Kurpinski K, Chu J, Wang DJ, Li S (2009) Proteomic proling of mesenchymal stem cell responses to mechanical strain and TGF-beta 1. Cell Mol Bioeng 2:606614Lammi MJ, Inkinen R, Parkkinen JJ, Hakkinen T, Jortikka M,

Nelimarkka LO, Jarvelainen HT, Tammi MI (1994) Expression of reduced amounts of structurally altered aggrecan in articular-cartilage chondrocytes exposed to high hydrostatic-pressure. Biochem J 304:723730Lang M (2007) Lighting up the mechanome. Bridge 37:1116 Lawrie CH, Gal S, Dunlop HM, Pushkaran B, Liggins AP, Pulford K,

Banham AH, Pezzella F, Boultwood J, Wainscoat JS et al (2008) Detection of elevated levels of tumour-associated microRNAs in serum of patients with diffuse large B-cell lymphoma. Br J Haematol 141:672675Li T (2008) A mechanics model of microtubule buckling in living cells. J Biomech 41:17221729Li YSJ, Haga JH, Chien S (2005) Molecular basis of the effects of shear stress on vascular endothelial cells. J Biomech 38:1949 1971Li H, Chen JA, Zhang Y, Sun SJ, Tao ZL, Long M (2010) Effects of oriented substrates on cell morphology, the cell cycle, and the cytoskeleton in Ros 17/2.8 cells. Sci Chin Life Sci 53:10851091 Li JL, Zhang F, Chen JY (2011) An integrated proteomics analysis of bone tissues in response to mechanical stimulation. BMC Syst Biol 5:S7

Li J, Rose E, Frances D, Sun Y, You LD (2012) Effect of oscillating uid ow stimulation on osteocyte mRNA expression. J Biomech 45:247251

Li M, Li X, Meikle MC, Islam I, Cao T (2013a) Short periods of cyclic mechanical strain enhance triple-supplement directed osteogenesis and bone nodule formation by human embryonic stem cells in vitro. Tissue Eng Part A 19:21302137

Li N, Mao D, Lu S, Tong C, Zhang Y, Long M (2013b) Distinct binding afnities of Mac-1 and LFA-1 in neutrophil activation. J Immunol 190:43714381

Li Z, Gong YW, Sun SJ, Du Y, Lu DY, Liu XF, Long M (2013c)

Differential regulation of stiffness, topography, and dimension of substrates in rat mesenchymal stem cells. Biomaterials 34:7616 7625Liang S, Fu C, Wagner D, Guo H, Zhan D, Dong C, Long M (2008)

Two-dimensional kinetics of beta(2)-integrin and ICAM-1 bindings between neutrophils and melanoma cells in a shear ow. Am J Physiol 294:C1604C1605Liu MY, Xu J, Tanswell AK, Post M (1994) Inhibition of mechanical strain-induced fetal-rat lung-cell proliferation by gadolinium, a stretch-activated channel blocker. J Cell Physiol 161:501507 Long M, Sato M, Lim CT, Wu JH, Adachi T, Inoue Y (2011) Advances in experiments and modeling in micro- and nano-biomechanics: a mini review. Cell Mol Bioeng 4:327339L SQ, Ye ZY, Zhu C, Long M (2006) Quantifying the effects of contact duration, loading rate, and approach velocity on P-selectinPSGL-1 interactions using AFM. Polymer 47:25392547L DY, Liu XF, Gao YX, Huo B, Kang YY, Chen J, Sun SJ, Chen L,

Luo XD, Long M (2013) Asymmetric migration of human keratinocytes under mechanical stretch and cocultured bro-blasts in a wound repair model. PLoS ONE 8:e74563Lynch ME, Brooks D, Mohanan S, Lee MJ, Polamraju P, Dent K,

Bonassar LJ, van der Meulen MCH, Fischbach C (2013) In vivo tibial compression decreases osteolysis and tumor formation in a human metastatic breast cancer model. J Bone Miner Res 28:23572367MacQueen L, Chebotarev O, Simmons CA, Sun Y (2012) Miniaturized platform with on-chip strain sensors for compression testing of arrayed materials. Lab Chip 12:41784184Malone AMD, Batra NN, Shivaram G, Kwon RY, You LD, Kim CH,

Rodriguez J, Jair K, Jacobs CR (2007) The role of actin cytoskeleton in oscillatory uid ow-induced signaling in MC3T3-E1 osteoblasts. Am J Physiol 292:C1830C1836 Mangala LS, Zhang Y, He Z, Emami K, Ramesh GT, Story M, Rohde

LH, Wu H (2011) Effects of simulated microgravity on expression prole of microRNA in human lymphoblastoid cells. J Biol Chem 286:3248332490Martinac B (2004) Mechanosensitive ion channels: molecules of mechanotransduction. J Cell Sci 117:24492460McNamara LE, Burchmore R, Riehle MO, Herzyk P, Biggs MJ,

Wilkinson CD, Curtis AS, Dalby MJ (2012) The role of microtopography in cellular mechanotransduction. Biomaterials 33:2835 2847Moraes C, Likhitpanichkul M, Lam CJ, Beca BM, Sun Y, Simmons

CA (2013) Microdevice array-based identication of distinct

Protein&Cell

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn 529

REVIEW Jiawen Wang et al.

mechanobiological response proles in layer-specic valve interstitial cells. Integr Biol 5:673680Moseyko N, Zhu T, Chang HS, Wang X, Feldman LJ (2002)

Transcription proling of the early gravitropic response in Arabidopsis using high-density oligonucleotide probe microarrays. Plant Physiol 130:720728Murrell M, Pontani LL, Guevorkian K, Cuvelier D, Nassoy P, Sykes C

(2011) Spreading dynamics of biomimetic actin cortices. Biophys J 100:14001409Nichols HL, Zhang N, Wen XJ (2006) Proteomics and genomics of microgravity. Physiol Genomics 26:163171Piltti J, Hayrinen J, Karjalainen HM, Lammi MJ (2008) Proteomics of chondrocytes with special reference to phosphorylation changes of proteins in stretched human chondrosarcoma cells. Biorheology 45:323335Plomion C, Pionneau C, Bailleres H (2003) Analysis of protein expression along the normal to tension wood gradient in Eucalyptus gunnii. Holzforschung 57:353358Porat Z, Yaron I, Katz BZ, Kam Z, Geiger B (2011) Shear ow-induced formation of tubular cell protrusions in multiple myeloma cells. J Cell Physiol 226:31973207Pozo L, Sanchez-Carrillo JJ, Martinez A, Blanes A, Diaz-Cano SJ

(2007) Differential kinetic features by tumour topography in cutaneous small-cell neuroendocrine (Merkel cell) carcinomas. J Eur Acad Dermatol 21:12201228Priam S, Bougault C, Houard X, Gosset M, Salvat C, Berenbaum F,

Jacques C (2013) Identication of soluble 14-3-3epsilon as a new subchondral bone mediator involved in cartilage degradation in osteoarthritis. Arthritis Rheumatol 65:18311842Qi YX, Jiang J, Jiang XH, Wang XD, Ji SY, Han Y, Long DK, Shen

BR, Yan ZQ, Chien S et al (2011) PDGF-BB and TGF-beta 1 on cross-talk between endothelial and smooth muscle cells in vascular remodeling induced by low shear stress. Proc Natl Acad Sci USA 108:19081913Richard MN, Deniset JF, Kneesh AL, Blackwood D, Pierce GN

(2007) Mechanical stretching stimulates smooth muscle cell growth, nuclear protein import, and nuclear pore expression through mitogen-activated protein kinase activation. J Biol Chem 282:2308123088Rogers RS, Dharsee M, Ackloo S, Sivak JM, Flanagan JG (2012)

Proteomics analyses of human optic nerve head astrocytes following biomechanical strain. Mol Cell Proteomics 11 (M111):012302Schatti O, Grad S, Goldhahn J, Salzmann G, Li Z, Alini M, Stoddart

MJ (2011) A combination of shear and dynamic compression leads to mechanically induced chondrogenesis of human mesenchymal stem cells. Eur Cells Mater 22:214225Sem DS, Yu L, Coutts SM, Jack R (2001) Object-oriented approach to drug design enabled by NMR SOLVE: rst real-time structural tool for characterizing protein-ligand interactions. J Cell Biochem 84:99105Shi Y, Li HW, Zhang XL, Fu YJ, Huang Y, Lui PPY, Tang TT, Dai KR

(2011) Continuous cyclic mechanical tension inhibited Runx2 expression in mesenchymal stem cells through RhoA-ERK1/2 pathway. J Cell Physiol 226:21592169

Shieh AC, Rozansky HA, Hinz B, Swartz MA (2011) Tumor cell invasion is promoted by interstitial ow-induced matrix priming by stromal broblasts. Cancer Res 71:790800Silkworth JB, Stehbens WE (1975) Shape of endothelial cells in en face preparations of rabbit blood-vessels. Angiology 26:474487 Sironen R, Elo M, Kaarniranta K, Helminen HJ, Lammi MJ (2000)

Transcriptional activation in chondrocytes submitted to hydro-static pressure. Biorheology 37:8593Sironen RK, Karjalainen HM, Torronen K, Elo MA, Kaarniranta K,

Takigawa M, Helminen HJ, Lammi MJ (2002) High pressure effects on cellular expression prole and mRNA stability. A cDNA array analysis. Biorheology 39:111117Soltz MA, Ateshian GA (2000) Interstitial uid pressurization during conned compression cyclical loading of articular cartilage. Ann Biomed Eng 28:150159Song MJ, Brady-Kalnay SM, McBride SH, Phillips-Mason P, Dean D,

Tate MLK (2012) Mapping the mechanome of live stem cells using a novel method to measure local strain elds in situ at the uid-cell interface. PLoS ONE 7:e43601Song MJ, Dean D, Knothe Tate ML (2013) Mechanical modulation of nascent stem cell lineage commitment in tissue engineering scaffolds. Biomaterials 34:57665775Stamenovic D, Ingber DE (2002) Models of cytoskeletal mechanics of adherent cells. Biomech Model Mechanobiol 1:95108 Sterky F, Bhalerao RR, Unneberg P, Segerman B, Nilsson P,

Brunner AM, Charbonnel-Campaa L, Lindvall JJ, Tandre K, Strauss SH et al (2004) A populus EST resource for plant functional genomics. Proc Natl Acad Sci USA 101:1395113956 Steward RL, Cheng CM, Ye JD, Bellin RM, LeDuc PR (2011)

Mechanical stretch and shear ow induced reorganization and recruitment of bronectin in broblasts. Sci Rep 1:147Sun SJ, Gao YX, Shu NJ, Tang ZM, Tao ZL, Long M (2008) A novel counter sheet-ow sandwich cell culture device for mammalian cell growth in space. Microgravity Sci Technol 20:115120Sun GY, Zhang Y, Huo B, Long M (2009) Parametric analysis for monitoring 2D kinetics of receptorligand binding. Cell Mol Bioeng 2:495503Swaminathan V, Mythreye K, OBrien ET, Berchuck A, Blobe GC,

Superne R (2011) Mechanical stiffness grades metastatic potential in patient tumor cells and in cancer cell lines. Cancer Res 71:50755080Tamura I, Rosenbloom J, Macarak E, Chaqour B (2001) Regulation of Cyr61 gene expression by mechanical stretch through multiple signaling pathways. Am J Physiol 281:C1524C1532Tan SD, de Vries TJ, Kuijpers-Jagtman AM, Semeins CM, Elverts V,

Klein-Nulend J (2007) Osteocytes subjected to uid ow inhibit osteoclast formation and bone resorption. Bone 41:745751 Tse JM, Cheng G, Tyrrell JA, Wilcox-Adelman SA, Boucher Y, Jain RK,

Munn LL (2012) Mechanical compression drives cancer cells toward invasive phenotype. Proc Natl Acad Sci USA 109:911916 van Loon JJWA (2009) Mechanomics and physicomics in gravisen-sing. Microgravity Sci Technol 21:159167Wang JHC (2006) Mechanobiology of tendon. J Biomech 39:15631582

Protein&Cell

530 The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn

Mechanomics between biology and biomechanics REVIEW

Wang YX, Shyy JYJ, Chien S (2008) Fluorescence proteins, live-cell imaging, and mechanobiology: seeing is believing. Annu Rev Biomed Eng 10:138

Wang XL, Fu A, Spiro C, Lee HC (2009) Proteomic analysis of vascular endothelial cells-effects of laminar shear stress and high glucose. J Proteomics Bioinform 2:445454

Ward DF, Salasznyk RM, Klees RF, Backiel J, Agius P, Bennett K,

Boskey A, Plopper GE (2007) Mechanical strain enhances extracellular matrix-induced gene focusing and promotes osteogenic differentiation of human mesenchymal stem cells through an extracellular-related kinase-dependent pathway. Stem Cells Dev 16:467479Wirtz D, Konstantopoulos K, Searson PC (2011) The physics of cancer: the role of physical interactions and mechanical forces in metastasis. Nat Rev Cancer 11:512522Wright MO, Nishida K, Bavington C, Godolphin JL, Dunne E,

Walmsley S, Jobanputra P, Nuki G, Salter DM (1997) Hyperpolarisation of cultured human chondrocytes following cyclical pressure-induced strain: evidence of a role for alpha 5 beta 1 integrin as a chondrocyte mechanoreceptor. J Orthop Res 15:742747Xu J, Khor KA, Sui J, Zhang J, Tan TL, Chen WN (2008)

Comparative proteomics prole of osteoblasts cultured on dissimilar hydroxyapatite biomaterials: an iTRAQ-coupled 2-D LCMS/MS analysis. Proteomics 8:42494258Yang R, Amir J, Liu HB, Chaqour B (2008) Mechanical strain activates a program of genes functionally involved in paracrine signaling of angiogenesis. Physiol Genomics 36:114

Yang F, Gao YX, Zhang Y, Chen J, Long M (2009) Developing a microuidic-based system to quantify cell capture efciency. Sci China Ser C 52:173181

Yi W, Sun Y, Wei XF, Gu CH, Dong XC, Kang XJ, Guo SZ, Dou KF

(2010) Proteomic proling of human bone marrow mesenchymal stem cells under shear stress. Mol Cell Biochem 341:916You LD, Cowin SC, Schafer MB, Weinbaum S (2001) A model for strain amplication in the actin cytoskeleton of osteocytes due to uid drag on pericellular matrix. J Biomech 34:13751386 Zayzafoon M, Meyers VE, McDonald JM (2005) Microgravity: the immune response and bone. Immunol Rev 208:267280Zdero R, McConnell AJ, Peskun C, Syed KA, Schemitsch EH (2011)

Biomechanical measurements of torsiontension coupling in human cadaveric femurs. J Biomech Eng 133:014501-1 014501-6Zhan DY, Zhang Y, Long M (2012) Spreading of human neutrophils on an ICAM-1-immobilized substrate under shear ow. Chin Sci Bull 57:769775Zhang Y, Sun GY, Lu SQ, Li N, Long M (2008) Low spring constant regulates P-selectinPSGL-1 bond rupture. Biophys J 95:5439 5448Zhou D, Lee HS, Villarreal F, Teng A, Lu E, Reynolds S, Qin C, Smith

J, Sung KLP (2005) Differential MMP-2 activity of ligament cells under mechanical stretch injury: an in vitro study on human ACL and MCL broblasts. J Orthop Res 23:949957

Protein&Cell

The Author(s) 2014. This article is published with open access at Springerlink.com and journal.hep.com.cn 531