Spontaneous differentiation of murine bone marrow-derived mesenchymal stem cells into adipocytes without malignant transformation after long-term culture.

Some observations have suggested that extensive culture of adult stem cells can lead to malignant transformation. Therefore, it has become commonplace to use stem cells undergoing little or no in vitro culture to circumvent this presumptive limitation. Recently, a detailed study documented that malignant transformation of adult neural stem cells can be avoided under suitable culture conditions. Here, we report the first demonstration that murine bone marrow-derived mesenchymal stem cells (bMSCs) were propagated in vitro for up to 50 passages without any transformation sign under suitable conditions. However, it must be noted that although the long-term cultured bMSCs were comparable with short-term cultured bMSCs in proliferation, migration and invasion, they lost their pluripotent potential. The long-term cultured bMSCs could only differentiate into adipocytes but not into osteocytes or chondrocytes. In conclusion, murine bMSCs can be propagated in vitro for up to 50 passages with no malignant transformation sign under suitable conditions, but how to sustain their pluripotent potential requires further investigation. 2009 S. Karger AG, Basel.