Year 2

The team has been highly productive during the first two years of work on this award. A major goal of the project is to evaluate the efficacy of neural progenitor cell transplantation to promote remyelination following virus induced central nervous system damage. With intracranial infection by the virus mouse hepatitis virus (MHV), mice develop paralysis due to immune mediated destruction of cells that generate myelin. Using protocols developed in the Loring laboratory, neural precursor cells (NPC) were derived from the human embryonic stem cell line H9. Mice developing paralysis due to intracranial infection with MHV were subject to intraspinal transplantation of these NPC, resulting in significant clinical recovery beginning at 2-3 weeks following transplant. This clinical effect of NPC transplantation remained out to six months, suggesting that these NPC are effective for long-term repair following demyelination. Despite this striking recovery, these human ES cell derived NPC were rapidly rejected. Several protocols for the generation of NPC for transplantation have been characterized, with the greatest clinical impact observed for NPC cultures bearing a high level of expression of TGF beta I and TGF beta II. These findings support the hypothesis that transplanted NPC reprogram the immune system within the central nervous system (CNS), leading to the activation of endogenous NPC and other repair mechanisms. Thus, it may not be necessary to induce complete immune suppression in order to promote remyelination and CNS repair following NPC transplantation for demyelinating diseases such as multiple sclerosis. In addition, the group is currently assessing the impact of NPCs in experimental autoimmune encephalomyelitis (EAE), an autoimmune model of MS. Initial results suggest that NPCs also reduce the severity of disease in this model, and studies are underway to determine the mechanism(s) by which NPCs promote clinical recovery during EAE.