Chondrocyte metabolism and matrix nano-electromechanics: The response to cartilage tissue shear deformation

Jin, Moonsoo.   Massachusetts Institute of Technology ProQuest Dissertations Publishing,  2002. 0804045.

Abstract (summary)

In this study, the electromechanical properties of cartilage have been studied by measuring equilibrium and dynamic shear stiffness as a function of the ionic concentration of bath solution. Measured shear properties were dependent on ionic concentration; the shear modulus increased and the phase angle between stress and strain decreased with decreasing ionic concentration. Theoretical models were developed to interpret the experimental results: (1) the glycosaminoglycans (GAGs) were modeled as cylindrical rods (a unit cell model) with the geometry based on the experimental measurement; (2) GAGs were embedded within collagen network which supports the repulsive forces between GAGs; (3) macroscopic shear deformation was reflected on the randomly oriented unit cell; and (4) the Poisson-Boltzmann equation was used to calculate the change in the free energy and the shear modulus as a function of ionic concentration and shear deformation. The reasonable comparison between experimental results and theoretical calculations suggests that the microstructural rearrangement of GAGs during shear deformation is an important determinant in the shear stiffness of cartilage.

In vivo compression of cartilage influences chondrocyte biosynthesis through mechanical deformation, fluid flow, and concomitant electrical and physicochemical changes. In vitro systems utilizing one or a combination of biophysical forces which chondrocytes are exposed to during compressive deformation in vivo have shown the complexity of biophysical environment, which potentially could alter chondrocyte biosynthesis. In this study, we have hypothesized that (1) shear deformation on poroelastic tissue like cartilage does not induce pressure gradient and relative interstitial fluid motion and (2) cell-matrix deformation produced by tissue shear deformation, with little or no accompanying fluid flow, can regulate cartilage metabolism. For this purpose, we have developed an incubator-housed tissue loading apparatus that can mimic the shear deformation in vivo on cartilage explants ex vivo. The effects of tissue shear (0.5–6% shear strain with frequencies between 0.01–1.0 Hz) on cartilage metabolism were evaluated across multiple pathways including phosphorylated ERK1/2 level, mRNA levels of aggrecan protein core and type II collagen, and matrix synthesis assessed by the proline and sulfate radiolabel incorporation and quantitative autoradiography. The synthesis of total protein (mostly collagen) and proteoglycan in response to shear deformation was significantly increased over static control by ∼50% and ∼25%, respectively. This increased matrix production was accompanied by the increases in mRNA levels of collagen and, less significantly, aggrecan core protein, which may be related, in part, to stimulated ERK1/2 pathways. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) (Abstract shortened by UMI.)

Indexing (details)

Mechanical engineering;
Biomedical research;
0548: Mechanical engineering
0541: Biomedical engineering
0786: Biophysics
Identifier / keyword
Applied sciences; Biological sciences; Cartilage; Chondrocyte; Nanoelectromechanical; Shear deformation
Chondrocyte metabolism and matrix nano-electromechanics: The response to cartilage tissue shear deformation
Jin, Moonsoo
Number of pages
Degree date
School code
DAI-B 63/07, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Grodzinsky, Alan J.
Massachusetts Institute of Technology
University location
United States -- Massachusetts
Source type
Dissertation or Thesis
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL