Cross-species neural grafting in a rat model of Parkinson's disease.

Abstract

Previous studies1–7 have shown that intracerebral implants of embryonic mesencephalic dopamine (DA) neurones, grafted between individuals of the same inbred rat strain, can reverse some of the functional deficits caused by damage to the nigrostriatal DA pathway. These observations have raised the possibility that the intracerebral neural grafting technique may eventually find a clinical application in the treatment of neurodegenerative disorders, particularly Parkinson's disease. One obvious obstacle to any such attempts is the immunological rejection mechanisms associated with allogeneic or xenogeneic grafting. Thus, neural tissue (sensory and sympathetic ganglia), transplanted across immunological barriers to sites outside the central nervous system (CNS), are known to be rejected8,9. The brain has, however, been described as an immunologically ‘privileged’ site, partly perhaps because of its protective blood–brain barrier10–12. This may be the case for grafts of embryonic tissue, in particular. Thus, Zalewski et al.13 have reported rejection of allografts of adult ganglionic neurones transplanted o the spinal cord, while Low et al.14 found prolonged survival of embryonic brain tissue in the hippocampal region, grafted between rats of different strains. We report here long-lasting functional cross-species transplantation of mesencephalic DA neurones, taken from mouse embryos, to the dopaminergically denervated neostriatum of adult recipient rats.