Aim: To investigate the possibility of chondrogenic differentiation and cartilage repair of synovial fluid cells of osteoarthritis (OA) knee.
Methods: Synovial fluids from 26 patients with OA knee were aspirated from each knee joint and cultured in vitro. The morphology of cultured synovial fluid cells, cell proliferation rate, the phenotype, and chondrogenic differentiation were analyzed in in vitro. Also, human autologous synovial fluid cells were transplanted to OA cartilage, and the cells were traced in ex vivo.
Results: In 19 of 26 materials, the cells proliferated satisfactorily. The cell proliferation in six materials was very slow and one material contaminated. Culture-expanded synovial fluid cells had a fibroblastic morphology and the phenotype was negative for CD10, CD14, and CD45, and positive for CD13, CD44, and CD105. Pellet culture of synovial fluid cells showed chondrogenic differentiation. In the ex vivo study, autologous transplanted synovial fluid cells were observed in repaired or enhanced regenerative cartilage areas and showed a tendency to infiltrate the original degenerative cartilage of OA.
Conclusions: This study proved the possibility of chondrogenic differentiation of synovial fluid cells of OA knee joints despite the pathologic environment within a diseased joint. Synovial fluid cells were actually heterogeneous cells but they showed chondrogenic differentiation, similar to that of bone marrow-derived mesenchymal progenitor cells (BMMPCs). The Ex vivo study suggested that synovial fluid cells had a tendency to adhere to OA degenerative cartilage in humans.