ASTROCYTES PROMOTE OR IMPAIR THE SURVIVAL AND FUNCTION OF EMBRYONIC VENTRAL MESENCEPHALON COGRAFTS - EFFECTS OF ASTROCYTE AGE AND EXPRESSION OF RECOMBINANT BRAIN-DERIVED NEUROTROPHIC FACTOR

Intrastriatal grafting of dopamine-rich embryonic ventral mesencephalo n (VM) is a potential therapeutic treatment for Parkinson's disease. H owever, it has been suggested that the efficacy of this procedure migh t be improved by enhancing the survival and/or degree of neurite outgr owth by the grafted VM, since these parameters are currently suboptima l. In the present study, we tested the ability of astrocytes retrovira lly transduced to produce recombinant brain-derived neurotrophic facto r (BDNF) to enhance the survival and/or function of embryonic VM in th e unilateral 6-hydroxydopamine (6-ORDA) lesioned rat, a well-character ized rodent model of Parkinson's disease. In culture, primary astrocyt es derived from Postnatal Day 0 (P0) rat striatum and transduced with the BDNF vector increased the survival of Embryonic Day 15 (E15) dopam inergic VM neurons by approximately threefold and reduced the loss of dopaminergic neurons following 6-OHDA treatment by approximately 20%. The cultured astrocytes were then mixed 1:1 with freshly dissociated E 15 VM and co-grafted into the dopamine-denervated striatum. Unexpected ly, the control nontransduced astrocytes reduced the survival of dopam inergic neurons by 60% and restricted the pattern of neurite outgrowth by the co-grafted VM, compared to grafts of VM alone at 7 weeks postg rafting. These effects were paralleled by an attenuated rate and degre e of behavioral recovery. The detrimental effects of the control astro cytes were partially reversed when the astrocytes were transduced to e xpress BDNF, although dopaminergic neuron survival was still reduced b y 30% compared to that within VM-only grafts. To begin to assess wheth er the detrimental effects of the astrocytes were related to the matur ational state of the cultured astrocytes, astrocytes were obtained fro m E18 striatum and maintained in short-term culture (9 days vs several weeks for P0 cultures) prior to co-grafting with VM. Interestingly, t he younger astrocytes did not reduce graft survival and allowed for be tter graft integration. These results suggest that primary astrocytes maintained in long-term culture are detrimental to embryonic neural gr afts, an effect that is not completely overcome by expression of recom binant BDNF, and that astrocyte age may be an important consideration in the use of these cells as CNS gene delivery vehicles. (C) 1997 Acad emic Press.