Dramatic differences in activity of purines metabolizing ecto-enzymes between mesenchymal stem cells isolated from human umbilical cord blood and umbilical cord tissue.

The high quality human mesenchymal stem cells (MSCs) with remarkable expansion potential in culture are demonstrated to possess multifold clinical applications. However, their isolation and characterization are difficult and sometimes ambiguous. We exploited nucleotide metabolizing ecto-enzymes for more complete characterization of MSCs. Using standard methods of cell culturing and analyses, we detected significant differences in the activity of ecto-nucleotidases on the surface of MSCs isolated from umbilical cord tissue and MSC-like cells derived from umbilical cord blood. Interestingly, the proliferation rate and the immunophenotypic characteristics of mesenchymal stem cells also correspond to the activities of these enzymes. Compared with the CD90-, CD105-, and CD73-deficient and slowly proliferating UCB-MSC-like cells that had relatively higher ecto-NTPDases activity, the CD90-, CD105-, and CD73-positive and rapidly proliferating UC-MSCs rather had ecto-5'-nucleotidase activity and presented neither ecto-nucleotidases nor adenylate kinase activities. In summary, our results demonstrate for the first time that activity of purine nucleotide metabolizing ecto-enzymes differs significantly between mesenchymal stem cells drawn from different neonatal sources, corresponding with a distinct proliferative potential.