Transplanted Neural Precursors Enhance Host Brain-Derived Myelin Regeneration

In multiple sclerosis lesions resident oligodendrocyte progenitor cells (OPCs) are present, but fail to remyelinate. In the current study we examined whether neural precursor cell (NPC) transplantation can facilitate host brain-derived remyelination. We used the chronic cuprizone-induced demyelination model in aged mice, in which slow remyelination follows cuprizone removal. NPCs were transplanted to the lateral ventricles (intracerebroventricular) of cuprizone-induced demyelinated brains. In this experimental setup, transplanted cells remained mostly in the periventricular area in an undifferentiated state. The extent of demyelination, remyelination, and proliferation of host brain regenerative cell population were examined at 1 week posttransplantation in the splenium of the corpus callosum, which was devoid of any transplanted cells. Transplantation of NPCs, but not of control, human embryonic kidney cells, significantly enhanced remyelination compared with sham-operated mice. Remyelination was performed exclusively by host brain OPCs. The proregenerative effect of transplanted NPCs was related to an increase in the proliferation of host brain OPCs. To examine the mechanism that underlies the proregenerative effect of NPCs in vitro, we used an NPC-OPC coculture system. These experiments indicated that NPCs induced the proliferation of OPCs and facilitated their differentiation into mature oligodendrocytes. The mitogenic effect of NPCs was mediated by platelet-derived growth factor-AA and fibroblast growth factor-2. In conclusion, NPC transplantation enhances host-derived myelin regeneration following chronic demyelination. This trophic effect may stimulate resident OPCs to overcome the remyelination failure in multiple sclerosis.