Characterization of two populations of mesenchymal progenitor cells in umbilical cord blood

Umbilical cord blood (UCB) is a valuable source for hematopoietic progenitor cell therapy. Moreover, it contains another subset of non-hematopoietic population referred to as mesenchymal progenitor cells (MPCs), which can be ex vivo expanded and differentiated into osteoblasts, chondrocytes and adipocytes. In this study, we successfully isolated the clonogenic MPCs from UCB by limiting dilution method. These cells exhibited two different morphologic phenotypes, including flattened fibroblasts (majority) and spindle-shaped fibroblasts (minority). Both types of MPCs shared similar cell surface markers except CD90 and had similar osteogenic and chondrogenic potentials. However, the spindle-shaped clones possessed the positive CD90 expression and showed a greater tendency in adipogenesis, while the flattened clones were CD90 negative cells and showed a lower tendency in adipogenesis. The high number of flattened MPCs might be linked to the less sensitivity of UCB-derived MPCs in adipogenic differentiation.