| Summary: | Mesenchymal stem cells isolated from rats are frequently used for tissue engineering research. However, considerable differences have been identified between rat mesenchymal stem cells and those derived from humans, and no defined panel of markers currently exists for the isolation of these cells. The aim of this study was to examine the effects of cell sorting for CD29 + /CD90 + cells from rat adipose and bone marrow tissues on their differentiation and expression of stem cell–associated genes. Flow cytometry showed 66% and 78% CD29 + /CD90 + positivity within passage 1 of adipose and bone marrow cultures, respectively. CD29 + /CD90 + cells showed a reduction in both osteogenic and adipogenic differentiation when compared with unsorted cells, as determined by alizarin red and Oil Red-O staining, respectively. These findings could not entirely be explained by fluorescence-activated cell sorting–induced cell injury as sort recovery was only modestly affected in adipose-derived cells. Maintaining cells in fluorescence-activated cell sorting buffer did not affect adipose-derived cell viability, but a significant (p < 0.05) reduction was found in bone marrow–derived cell viability. Additionally, CD29 + /CD90 + selection was associated with a significant decrease in the expression of Lin28, Sox2, Nanog and CD73 in adipose-derived cell cultures, whereas differences in stem cell–associated gene expression were not observed in sorted bone marrow–derived cell cultures. In summary, this study demonstrated that fluorescence-activated cell sorting had differential effects on adipose-derived cells and bone marrow–derived cells, and both CD29 + /CD90 + cells displayed a significantly reduced capacity for osteogenic/adipogenic differentiation. In conclusion, we identify that maintaining heterogeneity within the mesenchymal stem cell population may be important for optimal differentiation.
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