Identification of MSCs in vitro. Identification of BM-MSC in vitro. (A) The fluorescent activated cell sorting analysis showed that the adherent cells were positive for the well-defined MSC surface markers including CD29, CD44, and CD99, while negative for CD34. CD34 precluded the origination of hematopoietic progenitors. (B) MSCs extracted from the mouse bone marrow presented the fibroblastic shape with dark centers as well as transparent peripheries by the observation of phase contract invert microscopy (scale bar = 50 uM).