Objective: Mesenchymal stem cells from synovium have a greater proliferation and chondrogenic potential than do those from bone marrow, periosteum, fat, and muscle. This study was undertaken to compare fibrous synovium and adipose synovium (components of the synovium with subsynovium) to determine which is a more suitable source for mesenchymal stem cells, especially for cartilage regeneration, and to examine the features of adipose synovium-derived cells, fibrous synovium-derived cells, and subcutaneous fat-derived cells to determine their similarities.
Methods: Human fibrous synovium, adipose synovium, and subcutaneous fat were harvested from 4 young donors and 4 elderly donors. After digestion, the nucleated cells were plated at a density considered proper to expand at a maximum rate without colony-to-colony contact. The surface epitopes, proliferative capacity, cloning efficiency, and chondrogenic, osteogenic, and adipogenic differentiation potentials of the cells were compared.
Results: Fibrous synovium- and adipose synovium-derived cells were higher in STRO-1 and CD106 and lower in CD10 compared with subcutaneous fat-derived cells. Cells derived from fibrous and adipose synovium had higher proliferative potential and colony-forming efficiency compared with subcutaneous fat-derived cells, both in mixed-population and in single-cell-derived cultures. In chondrogenic assays, pellets from fibrous synovium- and adipose synovium-derived cells produced more cartilage matrix than did cell pellets from subcutaneous fat. Osteogenic ability was also higher in fibrous synovium- and adipose synovium-derived cells, whereas adipogenic potential was nearly indistinguishable among the 3 populations. Differentiation potential of the cells was similar between young and elderly donors.
Conclusion: Cells derived from the fibrous synovium and from the adipose synovium demonstrate comparable chondrogenic potential. Adipose synovium-derived cells are more similar to fibrous synovium-derived cells than to subcutaneous fat-derived cells.