Isolation and characterization of synovial mesenchymal stem cells

Synovial membrane and synovial fluid represent a good source of mesenchymal stem cells. They have been regarded as a promising therapeutic tool for musculoskeletal regeneration. Synovium-derived mesenchymal stem cells have higher expression of CD44 and better chondrogenic potential in vitro than mesenchymal stem cells from other tissues. In this study we compared mesenchymal stem cells from synovium and synovial fluid on the base of morphological, immunophenotype and differentiation features. A heterogeneous population of cells with different morphology was obtained after isolation and 4-day cultivation. The mesenchymal stem cell immunophenotype was confirmed by positive expression of CD105, CD90, and CD44 by flow cytometry and cells were negative for CD45. CD105+ cells were selected by immunomagnetic separation after 2-4 weeks of cultivation. The percentage of CD105+ cells in the mesenchymal stem cell population from synovia was between 40-50 % before immunomagnetic separation and increased to 95 % following the immunomagnetic separation. Von Kossa, Alcian blue and Oil Red O staining was used to assess the differentiation potential of synovial mesenchymal stem cells. Long-term cultivation did not affect the morphology and immunophenotype of synovial mesenchymal stem cells. Our results confirmed that immunomagnetic separation based on CD 105 antigen is a suitable method to enrich the subpopulation of CD105+ synovial mesenchymal stem cells.