Increasing dopamine neuron survival during grafting

对啮齿动物和非人灵长类动物的研究表明，高达95%的移植多巴胺（DA）神经元在植入纹状体后的第一周内死亡，这可能是迄今为止研究中临床结果不佳的原因。此外，当细胞植入老年宿主时，移植细胞的不良存活率似乎会被夸大。与移植过程和移植后早期间隔相关的多种损伤可使移植细胞易致死亡，包括机械损伤、缺氧、氧化应激和神经营养因子消退。尽管存在这些问题，确定DA移植物中的细胞死亡机制及其可能的触发因素，为有效的干预提供了途径

Studies in rodents and nonhuman primates suggest that up to 95% of grafted dopamine (DA) neurons die within the first week after implantation into the striatum, a possible contributor to poor clinical outcome in studies to date. In addition, poor survival of grafted cells appears to be exaggerated when cells are implanted into an elderly host. Multiple insults associated with the transplant procedure and early post-graft interval could render grafted cells susceptible to death, including mechanical trauma, hypoxia, oxidative stress, and neurotrophic factor withdrawal. Despite these problems, the identification of cell death mechanisms operating in DA grafts, and their probable triggers, provides access to cogent interventions to limit death of grafted neurons. This project aims to investigate four interventions that may limit death of grafted neurons, optimizing the potential for DA replacement and recovery of function: 1) reducing the apoptosis triggered by dissection and preparation of the tissue for implantation, termed "anoikis", via treatment with the cell adhesion factors L1 antibody and tenascin, and, 2) utilizing treatment with the lazaroid tirilazad mesylate and melatonin to reduce oxidant stress, 3) reducing hypoxia/ischemia by accelerating neovascularization of grafts using treatment with vascular endothelial growth factor (VEGF), 4) stimulating the DA phenotype of grafted cells by exposure to cyclic AMP. All interventions proposed have yielded significant graft augmentation in rodent experiments. In the present application, each intervention will be tested for functional efficacy in young adult MPTP-treated St. Kitts green monkeys. Optimally aged fetal mesencephalic tissue, with varying treatments, will be implanted into the striatum, and quantitative behavioral measurements will assess functional outcome, correlated with histological and biochemical evidence of more extensive grafts. A final experiment will combine treatments proven individually to augment graft function in young adult monkeys, and compare the functional outcome of this combination therapy in young adult and aged MPTP-treated monkeys. Successful methods for augmentation of grafted cell survival and growth may improve transplantation results and be applicable to stem cells or other cell-based therapies for Parkinson's disease.