Roy A.E. Bakay - US grants

The objective of this research project is to determine if adrenal chromaffin tissue can be successfully transplanted in primates to improve fixed neurologic dysfunction. The MPTP-induced Parkinson- like syndrome is an excellent model to test transplantation in nonhuman primates. Preliminary studies have demonstrated potential for correcting the Parkinson-like movement abnormalities using adrenal medullary tissue in the rhesus monkey (Macaca mulatta). The behavioral performance of chromaffin-grafted monkeys will be compared to non-operated and surgical controls that will receive the same operation but without placement of a graft. The goal is first to determine if grafting of chromaffin tissue to the head of the caudate by a transcortical intraventricular approach can produce statistically significant improvement in parkinson-like behavior. Once this is evaluated, then multiple aspects of the grafting technique will be explored (i.e., purity of the tissue separation, quantity of the graft, etc.) Behavioral assessment of motor function will be performed by clinical examination, computerized image analysis of spontaneous home cage activity and drug-induced rotation, and performance of learned forelimb tasks. Each animal will be tested prior to administration of MPTP, after stabilization of the Parkinson-like state, and following treatment, thus allowing each animal to serve as its own control. Anatomical assessment will allow comparison of treatment with control groups by quantification of loss of dopaminergic cells in the substantia nigra by immunocytologic staining for tyrosine hydroxylase. Graft cell survival will be evaluated by chromaffin and modified Giemsa staining as well as by tyrosine hydroxylase, dopamine-B- hydroxylase, and chromagranin A immunocytochemical reaction. Biochemical assessment will be performed by serial measurements of dopamine metabolites in the CSF and by measurement of levels of dopamine, dopamine metabolites, and tyrosine hydroxylase activity in the striatum post-mortem. If the neurologic deficits can be successfully improved in animals with this Parkinson-like syndrome, the implications are extremely important not only for the potential treatment of parkinsonism but also for any disease having a neurochemical deficiency responsible for a fixed neurologic deficit.

[unreadable] DESCRIPTION (provided by applicant): Stem cells offer tremendous promise for the future of transplantation. We propose examining embryonic stem cells (ESC) in monkey allografts. We will compare dopaminergic enriched ESC to fetal mesencephalic (FM) neurons in their ability to survive, innervate, and restore lost function in the best animal model of PD, the MPTP treated monkey. The primate is essential for this study to test the hypothesis that replacement strategy must completely reinnervate the very large volume of the monkey striatum. Recently clinical trials have indicated that dopaminergic (DAergic) replacement with FM neurons can cause severe debilitating dyskinesia. It is then imperative to have a clear understanding of how a DAergic enriched ESC replacement strategy affects I-dopa-induced dyskinesia (LID). In this regard, we will also compare the effects of FM transplants and DAergic enriched ESC upon the dyskinesia profile of MPTP monkeys. The potential to induce or diminish dyskinesia will be tested with the best model of dyskinesia (primate LID model). The key problem of parkinsonian transplantation with fetal or stem cells grafts is the incomplete reinnervation of host striatum. Like the FM transplant patients, focal areas of relative hyperdopaminergic activity should render these monkeys highly susceptible to LIDs. Thus to optimize reinnervation and functional recovery while minimizing the potential for dyskinesia, we will also treat DAergic enriched ESC with glial cell line-derived neurotrophic factor (GDNF) delivered via a lentiviral vector. The lenti-viral vector is critical to this hypothesis because of the proven ability to transfect the entire striatum and act not as a point source but as a volume source to stimulate reinnervation. Intraparenchymal GDNF released diffusely throughout the entire striatum should act as a developmental cue for these immature cells to extend DAergic processes throughout the striatum as well as provide neuronal rescue for dopaminergic neurons in the pars compacta of the substantia nigra. Sufficient subjects and multiple controls are included to insure proper interpretation of the data. The present series of experiments serves to provide the essential preclinical data needed to help determine the utility of nonhuman dopaminergic enriched stem cells. [unreadable] [unreadable]