Comparative Characterization of Canine and Human Mesenchymal Stem Cells Derived from Bone Marrow

Abstract

Bone marrow is a major source of mesenchymal stem cells (MSC), which are used in tissue engineering and other autologous stem cell therapies. Studies designed to use large canine models and translate the results to human practice must take into account the ex vivo and in vitro differences in the bone marrow samples. A set of morphological and physiological markers was used to compare MSC derived from canine and human bone marrow. Despite anticlotting treatment, frequent bone marrow clotting was a problem with canine samples, so we developed a protocol for enzymatic digestion of undesirable clots. We compared colony forming units (CFU) assay, population doubling time (PDT), senescenceassociated β-galactosidase (SA-β-Gal) activity, as well as the ability of cells to differentiate to osteogenic, adipogenic and chondrogenic phenotypes. Urokinase digestion resulted in recovery of MSC: 4-fold more CFU from canine and 1.6-fold more from human samples when compared to untreated samples. Canine MSC were less robust in vitro – they divided actively only for four weeks in culture, while human cells divided for longer than eight weeks. After six weeks in culture, canine MSC underwent 17 population doublings of while human cells reached 26. The percentage of senescent cells increased linearly with time, but with a faster rate in canine MSC. Human and canine MSC underwent differentiation to all lineages; however canine MSC had generally lower differentiation potential. In conclusion, the discrepancy between canine and human cultures must be considered in future MSC-based therapies based on dogs as animal model.