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

Innovative care protocol successfully rehabilitates non-human primates after MPTP-induced parkinsonism: Preliminary evidence from a restricted cohort of African Green Monkeys (Chlorocebus sabaeus)

The MPTP-animal model of Parkinson's disease has significantly advanced our understanding of Parkinson's disease and the dopaminergic system, helping to establish disease mechanisms and develop therapeutic targets. The non-human primate (NHP) MPTP model is particularly valuable for replicating core Parkinson's disease motor symptoms, anatomical changes and electrophysiological variations seen in humans. However, MPTP-injection protocols often cause substantial suffering, leading to euthanasia. While some post-MPTP primates recovered spontaneously, purposefully induced recovery was considered unattainable. Our team developed a novel intensive care protocol (NICP) promoting complete recovery from MPTP-induced severe parkinsonism in NHPs. NICP provides therapeutic, nutritional and social support, enabling behavioral recovery and subsequent retirement to a primate sanctuary. This innovation enhances animal welfare and opens new prospects for veterinary care, emphasizing the need to explore recovery mechanisms for other chronic conditions induced for research.

Implication of regional selectivity of dopamine deficits in impaired suppressing of involuntary movements in Parkinson's disease

To improve the initiation and speed of intended action, one of the crucial mechanisms is suppressing unwanted movements that interfere with goal-directed behavior, which is observed relatively aberrant in Parkinson's disease patients. Recent research has highlighted that dopamine deficits in Parkinson's disease predominantly occur in the caudal lateral part of the substantia nigra pars compacta (SNc) in human patients. We previously found two parallel circuits within the basal ganglia, primarily divided into circuits mediated by the rostral medial part and caudal lateral part of the SNc dopamine neurons. We have further discovered that the indirect pathway in caudal basal ganglia circuits, facilitated by the caudal lateral part of the SNc dopamine neurons, plays a critical role in suppressing unnecessary involuntary movements when animals perform voluntary goal-directed actions. We thus explored recent research in humans and non-human primates focusing on the distinct functions and networks of the caudal lateral part of the SNc dopamine neurons to elucidate the mechanisms involved in the impairment of suppressing involuntary movements in Parkinson's disease patients.

Effect of expiratory muscle strength training intervention on the maximum expiratory pressure and quality of life of patients with Parkinson disease

PURPOSE

The purpose of this study was to investigate the effects of 4-weeks expiratory muscle strength training (EMST) on the maximum expiratory pressure (PEmax) and quality of life (QoL) in patients with Parkinson disease (PD).

METHODS

Thirteen outpatients diagnosed with PD participated in this study, and were assigned into either a 5DE training group (5DE group; n = 4; 75% PEmax for 5-d/wk), 3DE training group (3DE group; n = 5; 75% PEmax for 3-d/wk) and control group (3DC group; n = 4; 0% PEmax for 3-d/wk) by matching their Hoehn and Yahr scale, genders, and age. The PEmax and Parkinson disease questionnaire-39 item (PDQ-39) were evaluated pre- and post-intervention.

RESULTS

The posttest PEmax of the 5DE was significantly higher than that of the 3DC (P < 0.05). Moreover, 5DE and 3DE but not 3DC significantly increased PEmax after training. There were no differences in the overall quality of life in PD patients measured by PDQ-39 among three groups, but the 5DE group significantly improved the mobility constructs of PDQ-39 compared with 3DC (P < 0.05).

CONCLUSION

Both 5 d/wk and 3 d/wk of EMST effectively enhance respiratory muscle strength and improve mobility construct measured by PDQ-39 in patients with PD.

Neuroprotective effects of astragaloside IV on Parkinson disease models of mice and primary astrocytes

Parkinson's disease (PD) is characterized by a progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta. Inflammation and neural degeneration are implicated in the pathogenesis of PD. Astragaloside IV (AS-IV) has been verified to attenuate inflammation. The current study aimed to investigate the role of AS-IV in PD and the possible molecular mechanisms. Pole, traction and swim tests were performed to examine the effects of AS-IV on 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-generated behavioral deficiencies in vivo. Meanwhile, as for in vitro experiments, the influence of AS-IV on cell viability was evaluated using the 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay, the effects of AS-IV on 1-methyl-4-phenylpyridnium ion (MPP+)-induced cell viability changes were tested using MTT assays, cell apoptosis rates were assessed using an Annexin-V Fluorescein isothiocyanate kit, and the expression levels of phosphorylated-Jun N-terminal kinase (p-JNK), Bcl-2-associated X protein (Bax)/Bcl-2 and caspase-3 activity were assessed using western blot analysis. Behavioral tests showed that pretreatment of AS-IV significantly alleviated MPTP-generated behavioral deficiencies in vivo. Meanwhile, AS-IV remarkably rescued MPP+-induced cell viability reduction, increase in cell apoptosis rate, and upregulation of p-JNK, Bax/Bcl-2 ratio and caspase-3 activity in vitro. In conclusion, AS-IV may be a promising neuroprotective agent for PD.

Deep brain stimulation for pain

Deep brain stimulation (DBS) is a neurosurgical intervention whose efficacy, safety, and utility have been shown in the treatment of movement disorders. For the treatment of chronic pain refractory to medical therapies, many prospective case series have been reported, but few have published findings from patients treated during the past decade using current standards of neuroimaging and stimulator technology. We summarize the history, science, selection, assessment, surgery, and personal clinical experience of DBS of the ventral posterior thalamus, periventricular/periaqueductal gray matter, and, latterly, the rostral anterior cingulate cortex (Cg24) in 100 patients treated now at two centers (John Radcliffe Hospital, Oxford, UK, and Hospital de São João, Porto, Portugal) over 12 years. Several experienced centers continue DBS for chronic pain with success in selected patients, in particular those with pain after amputation, brachial plexus injury, stroke, and cephalalgias including anesthesia dolorosa. Other successes include pain after multiple sclerosis and spine injury. Somatotopic coverage during awake surgery is important in our technique, with cingulate DBS considered for whole-body pain or after unsuccessful DBS of other targets. Findings discussed from neuroimaging modalities, invasive neurophysiological insights from local field potential recording, and autonomic assessments may translate into improved patient selection and enhanced efficacy, encouraging larger clinical trials.

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.

Novel monoclonal antibodies recognizing different subsets of lymphocytes from the common marmoset (Callithrix jacchus)

Callithrix jacchus, the common marmoset, is a small new world primate that is considered effective as an experimental animal model for various human diseases. In this study, we generated monoclonal antibodies (mAbs) against common marmoset lymphocytes for immunological studies on the common marmoset. We established five hybridoma clones, 6C9, 10D7, 6F10, 7A4 and 5A1, producing anti-marmoset mAbs against cell surface antigens on marmoset T and/or B lymphocytes. We confirmed that 6C9 and 10D7 antibodies recognized CD45 antigen, and 6F10 antibody recognized CD8 antigen by flow cytometry using marmoset cDNA transfectants. We also tested them for application of immunoprecipitation, Western blot analysis and immunohistochemistry. We found that immunohistochemistry using marmoset spleen sections could be applied with all established mAbs but immunoprecipitation and the Western blot analysis could be applied with 6F10 and 10D7 antibodies but not with the other three mAbs. These results show that these monoclonal antibodies are useful for advancing immunological research on the common marmoset.

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.

Deep-brain stimulation

Deep-brain stimulation (DBS) is a clinical intervention that has provided remarkable therapeutic benefits for otherwise treatment-resistant movement and affective disorders. The resulting direct causal manipulation of both local and distributed brain networks is not only clinically helpful but can also help to provide novel fundamental insights into brain function. In particular, DBS can be used in conjunction with methods such as local field potentials and magnetoencephalography to map the underlying mechanisms of normal and abnormal oscillatory synchronization in the brain. The precise mechanisms of action for DBS remain uncertain but here we present an overview of the clinical efficacy of DBS, its neural mechanisms and potential future applications.

Deep brain stimulation: indications and evidence

Deep brain stimulation is a minimally invasive targeted neurosurgical intervention that enables structures deep in the brain to be stimulated electrically by an implanted pacemaker. It has become the treatment of choice for Parkinson's disease, refractory to, or complicated by, drug therapy. Its efficacy has been demonstrated robustly by randomized, controlled clinical trials, with multiple novel brain targets having been discovered in the last 20 years. Multifarious clinical indications for deep brain stimulation now exist, including dystonia and tremor in movement disorders; depression, obsessive-compulsive disorder and Tourette's syndrome in psychiatry; epilepsy, cluster headache and chronic pain, including pain from stroke, amputation, trigeminal neuralgia and multiple sclerosis. Current research argues for novel indications, including hypertension and orthostatic hypotension. The development, principles, indications and effectiveness of the technique are reviewed here. While deep brain stimulation is a standard and widely accepted treatment for Parkinson's disease after 20 years of experience, in chronic pain it remains restricted to a handful of experienced, specialist centers willing to publish outcomes despite its use for over 50 years. Reasons are reviewed and novel approaches to appraising clinical evidence in functional neurosurgery are suggested.