Systematic Analysis of Reportedly Distinct Populations of Multipotent Bone Marrow-Derived Stem Cells Reveals a Lack of Distinction

Adult human bone marrow-derived stem cells, having the ability to differentiate into cells of multiple lineages, have been isolated and propagated by varied protocols, including positive (CD105+)/negative (CD45-GlyA-) selection with immunomagnetic beads, or direct plating into selective culture media. Each substratum-adherent cell population was subjected to a systematic analysis of their cell surface markers and differentiation potential. In the initial stages of culture, each cell population proliferated slowly, reaching confluence in 10-14 days. Adherent cells proliferated at similar rates whether cultured in serum-free medium supplemented with basic fibroblast growth factor, medium containing 2% fetal bovine serum (FBS) supplemented with epidermal growth factor and platelet-derived growth factor, or medium containing 10% FBS alone. Cell surface marker analysis revealed that more than 95% of the cells were positive for CD105/endoglin, a putative mesenchymal stem cell marker, and negative for CD34, CD31...