Human Cord Blood-Derived CD133(+)/C-Kit(+)/Lin(−) Cells Have Bipotential Ability to Differentiate into Mesenchymal Stem Cells and Outgrowth Endothelial Cells

Recent evidence suggests that mononuclear cells (MNCs) derived from bone marrow and cord blood can differentiate into mesenchymal stem cells (MSCs) or outgrowth endothelial cells (OECs). However, controversy exists as to whether MNCs have the pluripotent capacity to differentiate into MSCs or OECs or are a mixture of cell lineage-determined progenitors of MSCs or OECs. Here, using CD133(+)/C-kit(+)/Lin(−) mononuclear cells (CKL− cells) isolated from human umbilical cord blood using magnetic cell sorting, we characterized the potency of MNC differentiation. We first found that CKL− cells cultured with conditioned medium of OECs or MSCs differentiated into OECs or MSCs and this differentiation was also induced by cell-to-cell contact. When we cultured single CKL− cells on OEC- or MSC-conditioned medium, the cells differentiated morphologically and genetically into OEC- or MSC-like cells, respectively. Moreover, we confirmed that OECs or MSCs differentiated from CKL− cells had the ability to form capillary-like structures in Matrigel and differentiate into osteoblasts, chondrocytes, and adipocytes. Finally, using microarray analysis, we identified specific factors of OECs or MSCs that could potentially be involved in the differentiation fate of CKL− cells. Together, these results suggest that cord blood-derived CKL− cells possess at least bipotential differentiation capacity toward MSCs or OECs.