University of Calgary, Department of Cell Biology and Anatomy, Calgary, Alberta, Canada.
Biochem Biophys Res Commun. 2012 Jun 8;422(3):455-61. doi: 10.1016/j.bbrc.2012.05.015. Epub 2012 May 10.
Cartilage is one of few tissues where adult stem/progenitor cells have not been putatively identified. Recent studies have provided strong evidence that a sub-population of mesenchymal progenitor cells (MPCs) derived from the synovial fluid may be able to affect some degree of cartilage repair both in vivo and in vitro/ex vivo, however this does not appear to be the case in patients with arthritis. Previously, it has been found that synovial fluid osmolarity is decreased in patients with osteoarthritis (OA) or Rheumatoid arthritis (RA) and these changes in osmolarity have been linked to changes in chondrocyte gene regulation. However, it is yet unknown if changes in osmolarity regulate the gene expression in synovial fluid MPCs (sfMPCs), and by extension, chondrogenesis of this cell population. In the present study we have collected synovial fluid samples from normal, OA and RA knee joints, quantified the osmolarity of the fluid and modified the culture/differentiation media to span a range of osmolarities (264-375 mOsm). Chondrogenesis was measured with Alcian blue staining of cultures in addition to quantitative PCR (qPCR) using probes to Sox9, ACAN and Col2A1. Overall, sfMPCs from arthritic joints demonstrated decreased chondrogenic potential compared to sfMPCs isolated from normal synovial fluid. Furthermore, the sfMPCs retained increased chondrogenic potential if differentiated under the same osmolarity conditions for which they were initially derived within. In conclusion, it does appear the synovial fluid osmolarity regulates the chondrogenic potential of sfMPCs, however, further study is required to elucidate the mechanism by which the changes in osmolarity are sensed by the cells and regulate chondrogenic gene expression.
软骨是少数几种尚未被认为存在成体/祖细胞的组织之一。最近的研究提供了强有力的证据，表明滑膜液中的亚群间充质祖细胞（MPCs）可能能够在体内和体外/离体的一定程度上影响软骨修复，然而，在关节炎患者中情况并非如此。此前，人们发现骨关节炎（OA）或类风湿关节炎（RA）患者的滑液渗透压降低，这些渗透压的变化与软骨细胞基因调控的变化有关。然而，目前尚不清楚渗透压变化是否调节滑膜液 MPC（sfMPC）的基因表达，以及这种细胞群体的软骨生成。在本研究中，我们从正常、OA 和 RA 膝关节收集滑膜液样本，测量液体的渗透压，并修改培养/分化培养基以涵盖渗透压范围（264-375 mOsm）。通过对培养物进行阿尔辛蓝染色以及使用 Sox9、ACAN 和 Col2A1 探针进行定量 PCR（qPCR）来测量软骨生成。总体而言，与从正常滑膜液中分离的 sfMPC 相比，关节炎关节的 sfMPC 表现出降低的软骨生成潜力。此外，如果 sfMPC 在其最初来源的相同渗透压条件下进行分化，则保留增加的软骨生成潜力。总之，似乎滑膜液渗透压调节 sfMPC 的软骨生成潜力，但需要进一步研究阐明渗透压变化如何被细胞感知并调节软骨生成基因表达的机制。
