Bone marrow-derived cells have been postulated as a source of multipotent mesenchymal stem cells (MSC). However, the whole fraction of MSC remains heterogene-ous and the expansion of primitive subset of these cells is still not well established. Here, we optimized the protocol for propagating the low-adherent subfraction of MSC which results in long-term expansion of population characterized by CD45^-CD14⁺CD34⁺ phenotype along with expression of common MSC markers. We established that the expanded MSC are capable of differentiating into endothelial cells highly expressing angiogenic markers and exhibiting functional properties of endothelium. Moreover, we found these cells to be multipotent and capable of giving rise into cells from neuronal lineages. Interestingly, the expanded MSC form characteristic cellular spheres in vitro indicating primitive features of these cells. In sum, we isolated the novel multipotent subpopulation of CD45^-CD14⁺CD34⁺ bone marrow-derived cells that could be maintained in long-term culture without losing this potential.

Keywords: bone marrow, differentiation, endothelium, expansion, mesenchymal stem cells