Transplantation of human neural stem cells protect against ischemia in a preventive mode via hypoxia-inducible factor-1alpha stabilization in the host brain

Abstract

Hypoxia-inducible factor-1 (HIF-1) plays important roles in the prevention of cerebral ischemia. Deferoxamine (DFX), an iron chelator stabilizes the HIF-1alpha and activates target genes involved in compensation for ischemia. In this study, we are to investigate whether HIF-1alpha can be stabilized in human neural stem cells (NSCs) by DFX, and pre-transplantation of NSCs with HIF-1alpha stabilization can induce prolonged ischemic tolerance. In the DFX-treated NSCs, the HIF-1alpha protein expression was increased about 100-fold time-dependently, and subsequent transcriptional activation (VEGF, BDNF and CXCR4) was also observed. To test an ability to induce ischemic prevention in vivo, DFX-treated NSCs or naive NSCs were transplanted in the striatum of adult rats. Seven days following the transplantation, focal cerebral ischemia was done. Infarct volumes were reduced in both NSCs-transplanted groups, compared with ischemia-only, but more reduced in DFX-treated NSCs group. The protective effects of NSCs were ablated when HIF-1alpha was silenced. HIF-1alpha protein levels were increased in both NSCs-transplanted groups, but more increased in DFX-treated NSCs group. RT-PCR analysis manifested a downregulation of mRNA expression of TNF-alpha, IL-6 and MMP-9 in both NSCs groups, but further decrease in DFX-treated NSCs group. These findings provide evidence that HIF-1alpha stabilization in human NSCs can be achieved effectively by DFX, and HIF-1alpha-stabilized NSCs protect against ischemia in a preventive mode.