Neuroprotection by cord blood neural progenitors involves antioxidants, neurotrophic and angiogenic factors

Human umbilical cord blood (HUCB) is a valuable source for cell therapy since it confers neuroprotection in stroke animal models. However, the responsible sub-populations remain to be established and the mechanisms involved are unknown. To explore HUCB neuroprotective properties in a PC12 cell-based ischemic neuronal model, we used an HUCB mononuclear-enriched population of collagen-adherent cells, which can be differentiated in vitro into a neuronal phenotype (HUCBNP). Upon co-culture with insulted-PC12 cells, HUCBNP conferred approximately 30% neuroprotection, as evaluated by decreased lactate dehydrogenase and caspase-3 activities. HUCBNP decreased by 95% the level of free radicals in the insulted-PC12 cells, in correlation with the appearance of antioxidants, as measured by changes in the oxidation-reduction potential of the medium using cyclic-voltammetry. An increased level of nerve growth factor (NGF), vascular endothelial growth factor and basic fibroblast growth factor in the co-culture medium was temporally correlated with a -medium neuroprotection effect, which was partially abolished by heat denaturation. HUCBNP-induced neuroprotection was correlated with changes in gene expression of these neurotrophic factors, while blocked by K252a, an antagonist of the TrkA/NGF receptor. These findings indicate that HUCBNP-induced neuroprotection involves antioxidant(s) and neurotrophic factors, which, by paracrine and/or autocrine interactions between the insulted-PC12 and the HUCBNP cells, conferred neuroprotection.