Investigation of p75 neurotrophin receptor on human dental pulp stem cells (hDPSC)

Abstract

p75 neurotrophin receptor has recently been suggested as a neural stem cell marker in cells of the brain subventricular zone and brain subgranular zone. Human adult dental pulp stem cells (hDPSC) with the ability to differentiate into neural, chondrocyte, osteocyte and adipocyte lineages contain heterogeneous stem cell populations. p75 is prototypically a neutrophin receptor. hDPSC expressing the neural precursor marker nestin are able to differentiate into functionally active neurons in vitro under differentiation protocols, though there is no definitive method established yet. p75 is thus likely to delineate a population of hDPSC that become neural cells. Therefore, this current project aims to characterize p75 expression on hDPSC by immunohistochemistry and flow cytometry (chapter 3); investigate the role of p75 on hDPSC neural potential in vitro (chapter 4); and investigate hDPSC neural differentiation in vitro through neurosphere formation (chapter 5). This current study demonstrated that p75 is a neural stem cell marker in hDPSC cultures and defines a cell population with the potential to give rise to neurons and glial cells. Immunohistochemistry showed that p75+ hDPSC had higher expression of SOX1, SOX2, nestin, CD146 and SOX9 (nucleus) when compared to p75- hDPSC. Neurons generated from p75+ hDPSC exhibited more neuronal-like properties in their morphology, and immunohistochemical expression pattern, in particular with neuronal marker neurofilament medium chain (NFM). This study has also shown that hDPSC are able to differentiate into a neural lineage via neurosphere formation in vitro. The results indicated that p75+ hDPSC are a functional cell population which could mediate the hDPSC neural protection and neural replacement seen in stem cell therapy for stroke brain repair. This study identified a molecular target that could be used to enrich populations through cell sorting. In addition, the hDPSC neurosphere differentiation provides a superior analysis model to investigate the neural potential of hDPSC in vitro.