Murine mesenchymal stem cell isolated and expanded in low and high density culture system: surface antigen expression and osteogenic culture mineralization.

Marrow culture from mice has been reported to be overgrown by non-mesenchymal cells. In almost all protocols for isolation of murine mesenchymal stem cells (MSCs), high density culture systems have been employed. Since MSCs are colonogenic cells, the initiating cell seeding density may have significant impact on their cultures. This subject was explored in this study. For this purpose, the bone marrow cells from NMRI mice were plated at 2.5 x 10(6) cells/cm(2) and upon confluency were reseeded as either low density (50 cells/cm(2)) or high density (8 x 10(4) cells/cm(2)) cultures. The cells were expanded through an additional subculture and the passage 2 cells as a product of two culture systems were statistically compared with respect to their surface antigen profiles and osteogenic culture mineralization. While low density culture grew with multiple colony formation, there were no distinct colonies in high density cultures. In contrast to high density cultures, passage 2 cells from low density system possessed typical homogenous fibroblastic morphology. Some cells from high density system but not the low density cultures expressed hematopoietic and endothelial cell markers including CD135, CD34, CD31, and Vcam surface antigens. Furthermore, osteogenic cultures from low density system displayed significantly more mineralization than those from high density system. Taken together, it seems that low density culture system resulted in more purified MSC culture than its counterpart as high density culture system.