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The demand for treatment strategies for damaged musculoskeletal tissue is continuously growing, especially with the increasing number of older people with degenerative diseases of the skeletal system such as osteoarthritis (OA). Because depletion of multipotent cells has been implicated in degenerative joint diseases, cell-based therapies have been proposed for tissue regeneration, especially for cartilage repair. The aim of the present study is to focus on the possibility of deriving and expanding multipotential mesenchymal stem cells (MSCs) from bone marrow samples of patients with OA by characterizing MSCs at the single cell level.

Single-cell clonal cultures were established in 96-well plates by limiting dilution of bone marrow stromal cells (BMSCs) from three patients with OA. Fourteen clones were established for subsequent characterization. There was a wide variation in cell doubling times, with the time taken to reach 20 population doublings ranging from 37 days to more than 100 days. The clones were grouped into fast-growing and slow-growing clones. All except one of the fast-growing stem cell clones were tripotential. However, the slow-growing clones showed limited differentiation potential and morphological changes associated with cellular senescence with extended duration in culture. Flow cytometric analysis indicated a strong need to investigate for novel cell-surface characteristic markers of BMSCs because there was no obvious difference in the expression of the selected characteristic BMSC cell surface markers CD29, CD44, CD90, CD105, and CD166 between fast-growing and slow-growing clones. This study has demonstrated the existence of a fast-growing multipotential MSC population from bone marrow samples of patients with OA. Therefore, despite a supposedly smaller stem cell compartment in these patients, we demonstrate here that they can still yield a potentially therapeutically useful source of syngeneic MSCs.