Nerve Growth Factor-Responsive Neuronal Progenitors From Human Umbilical Cord Blood.

Nerve growth factor (NGF) is a well characterized neurotrophin required for the survival and differentiation of a variety of cell types in the peripheral and central nervous system. Over the last decade, many studies have demonstrated the physiological role of NGF in proliferation, differentiation and activation of different hematopoietic cells. Hematopoietic progenitors from bone marrow, umbilical cord blood and peripheral blood were found to be responsive to the actions of NGF. Furthermore, bone marrow stromal cells produce and respond to NGF during different steps of normal hematopoiesis.

In this study, we describe a population of collagen-adherent, CD49a/b (á1/2 integrin receptors) and nestin-positive human umbilical cord blood derived progenitors. The identity of these cells was established as positive for the mesenchymal markers: CD13, CD29, CD44, CD49a,b, CD49e, CD73, CD105 and vimentin and negative for the hematopoietic markers: CD34, CD49c, CD49d, CD62e, CD62p, CD106, CD117, CD133, CD235a, HLA-DRB4 and HAS1, using Affimatrix™ human DNA chip technology, immunomagnetic sorting and Western blotting approaches. The NGF- receptor, TrkA, was found to be expressed upon isolation of these progenitors, but was gradually down-regulated upon 14 days growth in culture, as measured by mRNA, protein expression and binding properties. However, continuous presense of NGF in the culture media preserved the TrkA receptors expression. The pan-neurotrophin NGF receptor p75NTR, belonging to the TNF family of cell-death receptors, was not detected in the progenitors at any time. The effect of NGF on the cord blood progenitors global gene expression indicated highly increased expression of 170 genes, 24 and 20% of which were related to neuronal proliferation (NEK1, cyclin B1, EGR4, LGN, GATA6) or differentiation (AP2, Neurogenic differentiation factor 2, lamin B1, Ca(2+)-activated Cl- channel, Kv channel, GABA-A alpha 5 receptor, D2 dopamine receptor, neuropeptides precursor), respectively and strong reduction in the expression of 58 genes, 35% of which were hematopoiesis-related (CD7, T cell receptor alpha, interleukin 21 receptor, natural killer cell transcript 4, HLA-G, complement component1, defensin alpha1). Furthermore, upon treatment with NGF, the progenitors expressed a neuronal-like phenotype as evaluated by measurements of long neurite outgrowths and various developmental neuronal markers expression (MAP-2, NeuN neurofillament-160, beta-tubulin III, neuron specific enolase). These findings strongly suggest NGF-induced reprogramming of the cord blood derived progenitors towards neuronal differentiation commitment. The progenitors were also found to confer ∼35% neuroprotection to neurons exposed to an ischemic damage by a “bystander” effect mechanism, which includes the increased autocrine secretion of NGF and activation of TrkA receptors in the insulted neurons.

These results suggest an important role for NGF in regulating human umbilical cord blood neuronal progenitor's growth and reprogramming towards neuronal differentiation. In view of the broad spectrum of possible uses of cord blood in transplantations, we may also suggest that human umbilical cord blood and/or derived NGF-responsive progenitors may serve as a useful source of neuronal cells for cell therapy of neuropathological disorders.

No relevant conflicts of interest to declare.