Activated T cells induce oligodendrocyte progenitor cells proliferation by releasing VEGF-A

Abstract

Neuroinflammatory diseases are characterized by infiltration of lymphocytes into the CNS, followed by demyelination and axonal degeneration. Evidence suggests that inflammatory factors released from activated T-cells induce neurotoxicity and impair function of neural stem cells. However, the effect of activated T-cells on the function of oligodendrocyte progenitor cells (OPCs) is uncertain, partly due to the difficulty in obtaining adult human oligodendrocytes. In this study, we used iNSCs to obtain OPCs and determined the effect of inflammatory factors on OPCs. Neural stem cells were induced from adult peripheral CD34 + cells by transduction using Sendai virus encoding transcription factor constructs of sox2, oct3/4, c-myc and klf4 and incubation in neural stem cell medium. The resulting cells were differentiated into OPCs and then exposed to supernatants from activated T-cells. Cell proliferation was determined by EdU incorporation assay and CellQuanti-Blue assay. Cell cycle progression was studied by transfecting OPCs with Fluorescence Ubiquitination Cell Cycle Indicator (FUCCI). VEGF-A and its receptors were studied by RT-PCR and western-blot assay. We found that supernatants from activated T cells increased OPC proliferation by regulating cell cycle progression. While VEGF-A expression was increased in T cells after activation, immunodepletion of VEGF-A from activated T cell supernatants significantly attenuated activated T cells induced OPC proliferation. Furthermore, we found that VEGF receptor 2 (VEGF-R2) was expressed on OPC and specific inhibition of VEGF-R2 with siRNA or inhibitor also attenuated activated T cell supernatants induced OPC proliferation. The effects of T cells and VEGF-A on OPC proliferation were also confirmed in primary human fetal OPC cultures. These results indicate that OPCs generated from CD34-derived neural stem cells behave similarly as primary OPCs in response to treatment by activated T cells and could be used to study the physiological functions and pathogenesis of OPCs, providing a specific advantage especially by using patient specific blood samples. Further, using this model we found that VEGF-A released from activated T cells could enhance OPC proliferation through activating VEGF-R2, indicating a complicated role for VEGF-A in T-cell mediated neuroinflammatory disorders.