Purpose: There were two aims of the present study. (i) to determine differences in chondrogenic potential between synovial cells located in the transitional zone between the articular cartilage and the synovial membrane and those cells in other locations and (ii) to determine the location of mesenchymal stem cells in the synovium.
Methods: Synovium was obtained from two different locations in 8-week-old male Sprague-Dawley rats. In Group A, the synovium was harvested from the transitional zone between the articular cartilage and the synovial membrane in the femoral condyle. In Group B, the synovium was harvested from an area 5 mm medial to the transitional zone of the femoral condyle. Synovial cells in both groups were isolated and cultured in monolayer culture system and the proliferation of cells in the first passage was compared between Groups A and B. In addition, passage 3 cells were pellet-cultured to induce chondrogenesis for the evaluation of the chondrogenic potential of the synovial cells.
The expression of anti-ATP-binding cassette G-subfamily member 2 (ABCG2), a mesenchymal stem cell marker, was assessed using a real-time polymerase chain reaction in both groups. In a related procedure, both knees of 8-week-old male mice were harvested and cut axially. The synovium in the transitional zone between the cartilage and synovial membrane was examined immunohistochemically by staining with an ABCG2 monoclonal antibody.
Results: The synovial cells in Group A demonstrated greater proliferation potential than those in Group B. Synovial cells derived from Groups A showed greater chondrogenic differentiation potential than those in B with respect to pellet size or the intensity of staining with toluidine blue. ABCG-2 expression was significantly higher in Group A than in Group B and ABCG2-stained cells were more prevalent in the synovium of the transitional zone than in the synovium located in other locations.
Conclusion: The synovium in the transitional zone between the articular cartilage and the synovial membrane contains mesenchymal stem cells and has a greater chondrogenic differentiation potential than synovium located in other sites.