Adipose mesenchymal stem cells protect chondrocytes from degeneration associated with osteoarthritis

Our work aimed at evaluating the role of adipose stem cells (ASC) on chondrocytes from osteoarthritic (OA) patients and identifying the mediators involved. We used primary chondrocytes, ASCs from different sources and bone marrow mesenchymal stromal cells (MSC) from OA donors. ASCs or MSCs were co-cultured with chondrocytes in a minimal medium and using cell culture inserts. Under these conditions, ASCs did not affect the proliferation of chondrocytes but significantly decreased camptothecin-induced apoptosis. Both MSCs and ASCs from different sources allowed chondrocytes in the cocultures maintaining a stable expression of markers specific for a mature phenotype, while expression of hypertrophic and fibrotic markers was decreased. A number of factors known to regulate the chondrocyte phenotype (IL-1β, IL-1RA, TNF-α) and matrix remodeling (TIMP-1 and -2, MMP-1 and -9, TSP-1) were not affected. However, a significant decrease of TGF-β1 secretion by chondrocytes and induction of HGF secretion by ASCs was observed. Addition of a neutralizing anti-HGF antibody reversed the anti-fibrotic effect of ASCs whereas hypertrophic markers were not modulated. In summary, ASCs are an interesting source of stem cells for efficiently reducing hypertrophy and dedifferentiation of chondrocytes, at least partly via the secretion of HGF. This supports the interest of using these cells in therapies for osteo-articular diseases.