The primate model of Parkinson's disease: its usefulness, limitations, and importance in directing future studies

Neuroprotective Surgical Strategies in Parkinson's Disease: Role of Preclinical Data

Although there have been many pharmacological agents considered to be neuroprotective therapy in Parkinson's disease (PD) patients, neurosurgical approaches aimed to neuroprotect or restore the degenerative nigrostriatal system have rarely been the focus of in depth reviews. Here, we explore the neuroprotective strategies involving invasive surgical approaches (NSI) using neurotoxic models 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), which have led to clinical trials. We focus on several NSI approaches, namely deep brain stimulation of the subthalamic nucleus, glial neurotrophic derived factor (GDNF) administration and cell grafting methods. Although most of these interventions have produced positive results in preclinical animal models, either from behavioral or histological studies, they have generally failed to pass randomized clinical trials to validate each approach. We argue that NSI are promising approaches for neurorestoration in PD, but preclinical studies should be planned carefully in order not only to detect benefits but also to detect potential adverse effects. Further, clinical trials should be designed to be able to detect and disentangle neuroprotection from symptomatic effects. In summary, our review study evaluates the pertinence of preclinical models to study NSI for PD and how this affects their efficacy when translated into clinical trials.

Computational identification and analysis of neurodegenerative disease associated protein kinases in hominid genomes

Protein kinases play an important role in the incidence of neurodegenerative diseases. However their incidence in non-human primates is found to be very low. Small differences among the genomes might influence the disease susceptibilities. The present study deals with finding the genetic differences of protein kinases in humans and their three closest evolutionary partners chimpanzee, gorilla and orangutan for three neurodegenerative diseases namely, Alzheimer's, Parkinson's and Huntington's diseases. In total 47 human protein kinases associated with three neurodegenerative diseases and their orthologs from other three non-human primates were identified and analyzed for any possible susceptibility factors in humans. Multiple sequence alignment and pairwise sequence alignment revealed that, 18 human protein kinases including DYRK1A, RPS6KB1, and GRK6 contained significant indels and substitutions. Further phosphorylation site analysis revealed that eight kinases including MARK2 and LTK contained sites of phosphorylation exclusive to human genomes which could be particular candidates in determining disease susceptibility between human and non-human primates. Final pathway analysis of these eight kinases and their targets revealed that these kinases could have long range consequences in important signaling pathways which are associated with neurodegenerative diseases.

Pedunculopontine stimulation from primate to patient

Deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) is a novel neurosurgical therapy developed to address symptoms of gait freezing and postural instability in Parkinson's disease and related disorders. Here we summarise our non-human primate investigations of relevance to our surgical targeting of the PPN and relate the primate research to initial clinical experience of PPN DBS.

Gene and cell delivery to the degenerated striatum: status of preclinical efforts in primate models

Significant progress has been achieved in developing restorative neurosurgical strategies for movement disorders on the basis of preclinical gene and cell therapy experiments in primates. Because of the unique similarities between human and primate anatomy and physiology, experiments in primate models are the critical step in translating these innovative neurosurgical treatment concepts into successful human applications. To clarify progress toward this goal, we have examined recent preclinical data regarding the delivery of gene and cell therapy to the lesioned primate striatum. Improved behavioral outcomes after in vivo gene transduction, achieved by brain delivery of adeno-associated vectors, have resulted in the initiation of ongoing clinical trials. Cell transplantation experiments are transitioning from the grafting of fetal tissue, which has met with mixed clinical success, to the grafting of expanded neural stem cells, for which preliminary results in primates are encouraging. Careful attention to the surgical delivery parameters for these agents in primate studies, along with the ability to realistically model imaging and behavioral outcomes in these animals, is essential for optimizing the restoration of function for patients. The authors review data obtained from primate models that form the basis for ongoing clinical trials to consider how new preclinical models should be developed to answer questions that arise from experimental clinical data.

The 3R principle and the use of non-human primates in the study of neurodegenerative diseases: the case of Parkinson's disease

The aim of this paper is to offer an ethical perspective on the use of non-human primates in neurobiological studies, using the Parkinson's disease (PD) as an important case study. We refer, as theoretical framework, to the 3R principle, originally proposed by Russell and Burch [Russell, W.M.S., Burch, R.L., 1959. The Principles of Humane Experimental Technique. Universities Federation for Animal Welfare Wheathampstead, England (reprinted in 1992)]. Then, the use of non-human primates in the study of PD will be discussed in relation to the concepts of Replacement, Reduction, and Refinement. Replacement and Reduction result to be the more problematic concept to be applied, whereas Refinement offers relatively more opportunities of improvement. However, although in some cases the 3R principle shows its applicative limits, its value, as conceptual and inspirational tool remains extremely valuable. It suggests to the researchers a series of questions, both theoretical and methodological, which can have the results of improving the quality of life on the experimental models, the quality of the scientific data, and the public perception from the non-scientist community.

Emerging restorative treatments for Parkinson's disease

Several exciting approaches for restorative therapy in Parkinson's disease have emerged over the past two decades. This review initially describes experimental and clinical data regarding growth factor administration. We focus on glial cell line-derived neurotrophic factor (GDNF), particularly its role in neuroprotection and in regeneration in Parkinson's disease. Thereafter, we discuss the challenges currently facing cell transplantation in Parkinson's disease and briefly consider the possibility to continue testing intrastriatal transplantation of fetal dopaminergic progenitors clinically. We also give a more detailed overview of the developmental biology of dopaminergic neurons and the potential of certain stem cells, i.e. neural and embryonic stem cells, to differentiate into dopaminergic neurons. Finally, we discuss adult neurogenesis as a potential tool for restoring lost dopamine neurons in patients suffering from Parkinson's disease.

Surgical insights into Parkinson's disease

Surgery for Parkinson's disease was popularized in the mid-twentieth century before the advent of effective medical therapies. Early lesioning treatments contributed to our understanding of the functional anatomy of Parkinson's disease. Observations of the limitations and long-term complications of established pharmacological therapies for Parkinson's disease, together with major contributions from animal research to elucidate the roles of the basal ganglia in movement disorders, inspired a recent renaissance in neurosurgical interventions for Parkinson's disease including deep brain stimulation; this continues to yield much neurophysiological information. The development of potentially restorative treatment modalities, such as gene therapy, neural transplantation and nanotechnology, hold much promise for surgery, both therapeutically and in revealing further insights into Parkinson's disease pathophysiology.

Surgical insights into Parkinson's disease

Surgery for Parkinson's disease was popularized in the mid-twentieth century before the advent of effective medical therapies. Early lesioning treatments contributed to our understanding of the functional anatomy of Parkinson's disease. Observations of the limitations and long-term complications of established pharmacological therapies for Parkinson's disease, together with major contributions from animal research to elucidate the roles of the basal ganglia in movement disorders, inspired a recent renaissance in neurosurgical interventions for Parkinson's disease including deep brain stimulation; this continues to yield much neurophysiological information. The development of potentially restorative treatment modalities, such as gene therapy, neural transplantation and nanotechnology, hold much promise for surgery, both therapeutically and in revealing further insights into Parkinson's disease pathophysiology.

Parkinson's disease and primate research: past, present, and future

Scientific research involving non-human primates has contributed towards many advances in medicine and surgery. This review discusses its role in the progress made towards our understanding of Parkinson's disease and its treatment. Established medical treatments like dopamine agonists continue to need primate models to assess their efficacy, safety, and mechanism of action. The recently developed treatment of deep brain stimulation of the subthalamic nucleus required validation in primates before entering the clinic. Controversies surrounding future treatments such as gene therapy show the need for properly evaluated preclinical research using appropriate animal models before progression to clinical trials. Research on primates has played--and continues to play--a crucial part in deepening our understanding of Parkinson's disease, improving current therapies, and developing new treatments that are both safe and effective. In animal research, the "three Rs" of humane technique--reduction, refinement, and replacement--should be adhered to.

Disease model: Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that is primarily characterized by the degeneration of dopaminergic neurons in the nigrostriatal pathway. The pathology of PD is typified by the presence of cytoplasmic inclusions (Lewy bodies) containing alpha-synuclein and ubiquitin. The pathogenesis of PD is not completely understood but environmental and genetic factors are thought to play important roles. To understand the pathophysiology of PD, and to develop novel therapies for improved symptomatic management, it is important to have relevant disease models. In this review, we summarize the available in vivo and in vitro models of PD and discuss their value.