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1.  The Immunological Challenges of Cell Transplantation for the Treatment of Parkinson’s Disease 
Brain Research Bulletin  2012;88(4):320-331.
Dopaminergic cell transplantation is an experimental therapy for Parkinson’s disease (PD). It has many potential theoretical advantages over current treatment strategies such as providing continuous local dopaminergic replenishment, eliminating motor fluctuations and medication-induced dyskinesias, slowing down disease progression or even reversing disease pathology in the host. Recent studies also show that dopaminergic cell transplants provide long-term neuromodulation in the basal ganglia that simulates the combined effects of oral dopaminergic therapy and surgical therapies like deep brain stimulation, the contemporary therapeutic approach to advanced PD. However, dopaminergic cell transplantation in PD as not been optimized and current experimental techniques have many drawbacks. In published experiments to date of attempted dopaminergic grafting in PD, the major challenges are unacceptable graft-induced dyskinesias or failure of such grafts to exceed the benefits afforded by sham surgery. A deleterious host immune response to the transplant has been implicated as a major putative cause for these adverse outcomes. This article focuses on recent advances in understanding the immunology of the transplantation in PD and possible methods to overcome adverse events such that we could translate cell replacement strategies into viable clinical treatments in the future.
PMCID: PMC3376210  PMID: 22521427
dopamine; nigrostriatal degeneration; central nervous system; immunosuppression; stem cells; retinal pigment epithelial cells
2.  The effect of striatal dopaminergic grafts on the neuronal activity in the substantia nigra pars reticulata and subthalamic nucleus in hemiparkinsonian rats 
Brain  2011;134(11):3276-3289.
The electrophysiological correlates of parkinsonism in the basal ganglia have been well studied in patients with Parkinson's disease and animal models. Separately, striatal dopaminergic cell transplantation has shown promise in ameliorating parkinsonian motor symptoms. However, the effect of dopaminergic grafts on basal ganglia electrophysiology has not thoroughly been investigated. In this study, we transplanted murine foetal ventral mesencephalic cells into rats rendered hemiparkinsonian by 6-hydroxydopamine injection. Three months after transplantation, extracellular and local field potential recordings were taken under urethane anaesthesia from the substantia nigra pars reticulata and subthalamic nucleus along with cortical electroencephalograms and were compared to recordings from normal and hemiparkinsonian controls. Recordings from cortical slow-wave activity and global activation states were analysed separately. Rats with histologically confirmed xenografts showed behavioural improvement measured by counting apomorphine-induced rotations and with the extended body axis test. Firing rates in both nuclei were not significantly different between control and grafted groups. However, burst firing patterns in both nuclei in the slow-wave activity state were significantly reduced (P < 0.05) in rats with large surviving grafts, compared to hemiparkinsonian controls. The neuronal firing entropies and oscillations in both nuclei were restored to normal levels in the large-graft group. Electroencephalogram spike-triggered averages also showed normalization in the slow-wave activity state (P < 0.05). These results suggest that local continuous dopaminergic stimulation exerts a normalizing effect on the downstream parkinsonian basal ganglia firing patterns. This novel finding is relevant to future preclinical and clinical investigations of cell transplantation and the development of next-generation therapies for Parkinson's disease that ameliorate pathophysiological neural activity and provide optimal recovery of function.
PMCID: PMC3212711  PMID: 21911417
neural transplantation; Parkinson's disease; substantia nigra pars reticulata; subthalamic nucleus; electrophysiology

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