Content area
Full text
Received Nov 16, 2017; Revised Jan 31, 2018; Accepted Feb 15, 2018
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Mesenchymal stem cells (MSCs) can be found in almost all tissues in the human body. They, being multipotent, can differentiate into multiple mature cell types like osteocytes, chondrocytes, or adipocytes under certain physiological or experimental conditions. Besides, they are able to replenish simultaneously the stem cell pool through self-renewal [1]. These features make them potential elements of cell-based therapies of the musculoskeletal system, for example, in case of osteoarthritis [2, 3], osteonecrosis [4], or other bone and cartilage injuries. The isolation method of this cell type is well described; therefore, it is an everyday process to extract MSCs from bone marrow, and a similar cell population can be obtained from adipose tissue, umbilical cord blood, or skeletal muscle [5–8]. As a drawback, during expansion in culture, animal sera like fetal calf serum (FCS) must be included as a supplement; otherwise, the cells stop proliferating. Bovine serum has economical, ethical, and scientific disadvantages such as immunogenicity, contaminations with prions and other pathogens, and the cost and ethical issues surrounding slaughtering calves just for their serum. These problems render animal serum a serious bottleneck of clinical applications [9–11]. However, it is unavoidable to supplement cell cultures with serum-specific growth factors, and other, still-unidentified factors of the serum as MSCs cannot survive in the absence of such components. Thus, human blood-derived additives like human serum albumin (HSA) [12] or platelet releasates such as platelet-rich plasma (PRP) are considered as efficient alternatives to replace FCS [13, 14]. The scientific rationale behind platelet-rich products is that thrombocytes provide a diverse growth factor supply such as platelet-derived growth factors (PDGFs), transforming growth factor beta-1 (TGFβ-1) or vascular endothelial growth factor (VEGF), coagulation factors, serotonin, mitogens, and adhesion factors like fibronectin, fibrin, or vitronectin to support healing [15]. On the one hand, these molecules play a role in the proliferation and differentiation of expanded cells in vitro or during the early phases after implantation into the host. Besides, these same factors are crucial in the...