Treatment of spinal cord injury with biomaterials and stem cell therapy in non-human primates and humans

Spinal cord injury results in the loss of sensory,motor,and autonomic functions,which almost always produces permanent physical disability.Thus,in the search for more effective treatments than those already applied for years,which are not entirely efficient,researches have been able to demonstrate the potential of biological strategies using biomaterials to tissue manufacturing through bioengineering and stem cell therapy as a neuroregenerative approach,seeking to promote neuronal recovery after spinal cord injury.Each of these strategies has been developed and meticulously evaluated in several animal models with the aim of analyzing the potential of interventions for neuronal repair and,consequently,boosting functional recovery.Although the majority of experimental research has been conducted in rodents,there is increasing recognition of the importance,and need,of evaluating the safety and efficacy of these interventions in non-human primates before moving to clinical trials involving therapies potentially promising in humans.This article is a literature review from databases(PubMed,Science Direct,Elsevier,Scielo,Redalyc,Cochrane,and NCBI)from 10 years ago to date,using keywords(spinal cord injury,cell therapy,non-human primates,humans,and bioengineering in spinal cord injury).From 110 retrieved articles,after two selection rounds based on inclusion and exclusion criteria,21 articles were analyzed.Thus,this review arises from the need to recognize the experimental therapeutic advances applied in non-human primates and even humans,aimed at deepening these strategies and identifying the advantages and influence of the results on extrapolation for clinical applicability in humans.

Advances in spinal cord injury:insights from non-human primates

Spinal cord injury results in significant sensorimotor deficits,currently,there is no curative treatment for the symptoms induced by spinal cord injury.Basic and pre-clinical research on spinal cord injury relies on the development and characterization of appropriate animal models.These models should replicate the symptoms observed in human,allowing for the exploration of functional deficits and investigation into various aspects of physiopathology of spinal cord injury.Non-human primates,due to their close phylogenetic association with humans,share more neuroanatomical,genetic,and physiological similarities with humans than rodents.Therefore,the responses to spinal cord injury in nonhuman primates most likely resemble the responses to traumatism in humans.In this review,we will discuss nonhuman primate models of spinal cord injury,focusing on in vivo assessments,including behavioral tests,magnetic resonance imaging,and electrical activity recordings,as well as ex vivo histological analyses.Additionally,we will present therapeutic strategies developed in non-human primates and discuss the unique specificities of non-human primate models of spinal cord injury.

Optical-neural Stimulation in Non-human Primates:Modulating Brain Function and Behavior

Optical-neural stimulation,which encompasses cutting-edge techniques such as optogenetics and infrared neurostimulation,employs distinct mechanisms to modulate brain function and behavior.These advanced neuromodulation techniques offer accurate manipulation of targeted areas,even selectively modulating specific neurons,in the brain.This makes it possible to investigate the cause-and-effect connections between neural activity and behavior,allowing for a better comprehension of the intricate brain dynamics towards complex environments.Non-human primates serve as an essential animal model for investigating these complex functions in brain research,bridging the gap between the basic research and clinical applications.One of the earliest optical studies utilizing optogenetic neuromodulation in monkeys was conducted in 2009.Since then,the optical-neural stimulations have been effectively applied in non-human primates.This review summarises recent research that employed optogenetics or infrared neurostimulation techniques to regulate brain function and behavior in non-human primates.The current state of optical-neural stimulations discussed here demonstrates their efficacy in advancing the understanding of brain systems.Nevertheless,there are still challenges that need to be addressed before they can fully achieve their potential.

Defects and asymmetries in the visual pathway of non-human primates with natural strabismus and amblyopia

Strabismus and amblyopia are common ophthalmologic developmental diseases caused by abnormal visual experiences. However, the underlying pathogenesis and visual defects are still not fully understood. Most studies have used experimental interference to establish diseaseassociated animal models, while ignoring the natural pathophysiological mechanisms. This study was designed to investigate whether natural strabismus and amblyopia are associated with abnormal neurological defects. We screened one natural strabismic monkey(Macaca fascicularis) and one natural amblyopic monkey from hundreds of monkeys, and retrospectively analyzed one human strabismus case. Neuroimaging, behavioral,neurophysiological, neurostructural, and genovariation features were systematically evaluated using magnetic resonance imaging(MRI), behavioral tasks, flash visual evoked potentials(FVEP),electroretinogram(ERG), optical coherence tomography(OCT), and whole-genome sequencing(WGS), respectively. Results showed that the strabismic patient and natural strabismic and amblyopic monkeys exhibited similar abnormal asymmetries in brain structure, i.e., ipsilateral impaired right hemisphere. Visual behavior, visual function, retinal structure, and fundus of the monkeys were impaired. Aberrant asymmetry in binocular visual function and structure between the strabismic and amblyopic monkeys was closely related, with greater impairment of the left visual pathway.Several similar known mutant genes for strabismus and amblyopia were also identified. In conclusion,natural strabismus and amblyopia are accompanied by abnormal asymmetries of the visual system,especially visual neurophysiological and neurostructural defects. Our results suggest that future therapeutic and mechanistic studies should consider defects and asymmetries throughout the entire visual system.

Application of the genome editing tool CRISPR/Cas9 in non-human primates

In the past three years, RNA-guided Cas9 nuclease from the microbial clustered regularly interspaced short palindromic repeats （CRISPR） adaptive immune system has been used to facilitate efficient genome editing in many model and non-model animals. However, its application in nonhuman primates is still at the early stage, though in view of the similarities in anatomy, physiology, behavior and genetics, closely related nonhuman primates serve as optimal models for human biology and disease studies. In this review, we summarize the current proceedings of gene editing using CRISPR/Cas9 in nonhuman primates.

Future of liver transplantation: Non-human primates for patient-specific organs from induced pluripotent stem cells

Strategies to fill the huge gap in supply versus demand of human organs include bioartificial organs, growing humanized organs in animals, cell therapy, and implantable bioengineered constructs. Reproducing the complex relations between different cell types, generation of adequate vasculature, and immunological complications are road blocks in generation of bioengineered organs, while immunological complications limit the use of humanized organs produced in animals. Recent developments in induced pluripotent stem cell (iPSC) biology offer a possibility of generating human, patient-specific organs in non-human primates (NHP) using patient-derived iPSC and NHP-derived iPSC lacking the critical developmental genes for the organ of interest complementing a NHP tetraploid embryo. The organ derived in this way will have the same human leukocyte antigen (HLA) profile as the patient. This approach can be curative in genetic disorders as this offers the possibility of gene manipulation and correction of the patient's genome at the iPSC stage before tetraploid complementation. The process of generation of patient-specific organs such as the liver in this way has the great advantage of making use of the natural signaling cascades in the natural milieu probably resulting in organs of great quality for transplantation. However, the inexorable scientific developments in this direction involve several social issues and hence we need to educate and prepare society in advance to accept the revolutionary consequences, good, bad and ugly.

Soybean Hull and Its Effect on Atherosclerosis in Non-Human Primates (Macaca fascicularis)

Twenty five monkeys were used in this experiment. They were divided into 5 groups with 5 animals as the replicates in each group and were adapted for two weeks to the environment before the data were collected. The animals were subjected to 5 experimental diets, i.e. T1 (Basal diet); T2 (Basal diet + palm oil); T3 (Basal diet + palm oil + soybean hull); T4 (Basal diet + cholesterol) and T5 (Basal diet + cholesterol + soybean hull). The diets were given for a period of 8 months and water were given ad lib. Blood serum was taken before and during the experiment. The cholesterol, triglycerides, LDL and HDL were measured using the spectrophotometric method. At the end of the experiment thorax surgery was performed on the animals under general anesthesia. The aorta was removed surgicalIy for histopathological observation stained with hematoxylin and eosine.The results showed that the soybean hull decreased the serum cholesterol level in the groups given palm oil (T2 vs T3) and the groups given cholesterol (T4 vs T5) i.e.: 163.4 vs 124.7 mg/dl and 359 vs 288.5 mg/dl respectively. The soybean hull did not significantly affect the serum triglyceride nor the LDL level when palm oil was given in the diet, but it significantly decreased the two parameters where cholesterol was given in the diet (102.5 vs 98.6 mg/dl triglyceride) and (231 .9 vs 183 mg/dl LDL). The soybean hull did not seem to affect the HDL level.Histopathological observation of the aorta indicated that given T1, T2, T3, T4 and T5 caused 45%, 41 .67%, 31.25%, 86.25% and 53.38% lesion (Atheroma arteriale) resPectively.It was concluded that the soybean hull given in the diet has the ability to prevent the development of atherosclerosis in the aorta of the experimental animals

Meeting report:the 4^(th) symposium on animal models of non-human primates in Kunming,Yunnan,China

From 2 to 4 November, 2016, the 4th Symposium on Animal Models of Non-Human Primates （NHP） was held in Kunming, Yunnan, China. This meeting was organized by the Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences （CAS） ＆ Yunnan Province Kunming Primate Research Center （KPRC）, Zoological Research, and Kunming Institute of Zoology （KIZ）, CAS.

Research progress in molecular epidemiology of Cryptosporidium in non-human primates

Cryptosporidium is an emerging single-cell zoonotic pathogen.By invading human and animal small intestinal epithelial cells,the host produces a variety of clinical symptoms,mainly diarrhea.Spores of Cryptosporidium can be transmitted through water-borne,food-borne,and mutual transmission between hosts,which has important public health significance.Studies have shown that non-human primates can be infected with multiple Cryptosporidium genotypes.Moreover,this species has a high genetic similarity with humans,so it needs to be taken seriously.This article reviews the infection rates,genotypes,and zoonotic risk of Cryptosporidium in non-human primates.

Xenotransplantation of embryonic pig pancreas for treatment of diabetes mellitus in non-human primates

Transplantation therapy for diabetes in humans is limited by the low availability of human donor whole pancreas or islets. Outcomes are complicated by immunosuppressive drug toxicity. Xenotransplantation is a strategy to overcome supply problems. Implantation of tissue obtained early during embryogenesis is a way to reduce transplant immunogenicity. Pig insulin is biologically active in humans. In that regard the pig is an appropriate xenogeneic organ donor. Insulin-producing cells originating from embryonic pig pancreas obtained very early following pancreatic primordium formation [embryonic day 28 (E28)] engraft long-term in rhesus macaques. Endocrine cells originating from embryonic pig pancreas transplanted in host mesentery migrate to mesenteric lymph nodes, engraft, differentiate and improve glucose tolerance in rhesus macaques without the need for immune suppression. Transplantation of embryonic pig pancreas is a novel approach towards beta cell replacement therapy that could be applicable to humans.

Global view on virus infection in non-human primates and implications for public health and wildlife conservation

Viruses can be transmitted from animals to humans(and vice versa)and across animal species.As such,host-virus interactions and transmission have attracted considerable attention.Non-human primates(NHPs),our closest evolutionary relatives,are susceptible to human viruses and certain pathogens are known to circulate between humans and NHPs.Here,we generated global statistics on virus infections in NHPs(VI-NHPs)based on a literature search and public data mining.In total,140 NHP species from 12 families are reported to be infected by 186 DNA and RNA virus species,68.8%of which are also found in humans,indicating high potential for crossing species boundaries.

Molecular identification of hemoplasmas in free ranging non-human primates in Thailand

Objective: To survey hemoplasmas infection in free ranging non-human primates from 8 provinces in Thailand. Methods: DNA from ethylenediaminetetraacetic acid blood of 262 free ranging non-human primates were identified as hemoplasmas using PCR and phylogenetic analysis based on 16 S r RNA and rnp B genes. Results: A total of 148 non-human primates(56.49%) were determined positive for Candidatus Mycoplasma haemomacaque, including 125 Macaca fascicularis and 23 Macaca mulatta. Hemoplasmas can cause anemia in monkey but all positive samples were healthy. The positive rates in male and female non-human primates were not significantly different. Conclusions: Candidatus Mycoplasma infection is prevalent in free ranging Macaca fascicularis and Macaca mulatta in Thailand.

Disease modifying treatment of spinal cord injury with directly reprogrammed neural precursor cells in non-human primates

BACKGROUND The development of regenerative therapy for human spinal cord injury(SCI)is dramatically restricted by two main challenges:the need for a safe source of functionally active and reproducible neural stem cells and the need of adequate animal models for preclinical testing.Direct reprogramming of somatic cells into neuronal and glial precursors might be a promising solution to the first challenge.The use of non-human primates for preclinical studies exploring new treatment paradigms in SCI results in data with more translational relevance to human SCI.AIM To investigate the safety and efficacy of intraspinal transplantation of directly reprogrammed neural precursor cells(drNPCs).METHODS Seven non-human primates with verified complete thoracic SCI were divided into two groups:drNPC group(n=4)was subjected to intraspinal transplantation of 5 million drNPCs rostral and caudal to the lesion site 2 wk post injury,and lesion control(n=3)was injected identically with the equivalent volume of vehicle.RESULTS Follow-up for 12 wk revealed that animals in the drNPC group demonstrated a significant recovery of the paralyzed hindlimb as well as recovery of somatosensory evoked potential and motor evoked potential of injured pathways.Magnetic resonance diffusion tensor imaging data confirmed the intraspinal transplantation of drNPCs did not adversely affect the morphology of the central nervous system or cerebrospinal fluid circulation.Subsequent immunohistochemical analysis showed that drNPCs maintained SOX2 expression characteristic of multipotency in the transplanted spinal cord for at least 12 wk,migrating to areas of axon growth cones.CONCLUSION Our data demonstrated that drNPC transplantation was safe and contributed to improvement of spinal cord function after acute SCI,based on neurological status assessment and neurophysiological recovery within 12 wk after transplantation.The functional improvement described was not associated with neuronal differentiation of the allogeneic drNPCs.Instead,directed drNPCs migration to the areas of active growth cone formation may provide exosome and paracrine trophic support,thereby further supporting the regeneration processes.

Current state of stem cell research in non-human primates:an overview

The remarkable similarity between non-human primates(NHPs)and humans establishes them as essential models for understanding human biology and diseases,as well as for developing novel therapeutic strategies,thereby providing more comprehensive reference data for clinical treatment.Pluripotent stem cells such as embryonic stem cells and induced pluripotent stem cells provide unprecedented opportunities for cell therapies against intractable diseases and injuries.As continue to harness the potential of these biotechnological therapies,NHPs are increasingly being employed in preclinical trials,serving as a pivotal tool to evaluate the safety and efficacy of these interventions.Here,we review the recent advancements in the fundamental research of stem cells and the progress made in studies involving NHPs.

Genetically modified non-human primate models for research on neurodegenerative diseases

Neurodegenerative diseases(NDs)are a group of debilitating neurological disorders that primarily affect elderly populations and include Alzheimer's disease(AD),Parkinson's disease(PD),Huntington's disease(HD),and amyotrophic lateral sclerosis(ALS).Currently,there are no therapies available that can delay,stop,or reverse the pathological progression of NDs in clinical settings.As the population ages,NDs are imposing a huge burden on public health systems and affected families.Animal models are important tools for preclinical investigations to understand disease pathogenesis and test potential treatments.While numerous rodent models of NDs have been developed to enhance our understanding of disease mechanisms,the limited success of translating findings from animal models to clinical practice suggests that there is still a need to bridge this translation gap.Old World nonhuman primates(NHPs),such as rhesus,cynomolgus,and vervet monkeys,are phylogenetically,physiologically,biochemically,and behaviorally most relevant to humans.This is particularly evident in the similarity of the structure and function of their central nervous systems,rendering such species uniquely valuable for neuroscience research.Recently,the development of several genetically modified NHP models of NDs has successfully recapitulated key pathologies and revealed novel mechanisms.This review focuses on the efficacy of NHPs in modeling NDs and the novel pathological insights gained,as well as the challenges associated with the generation of such models and the complexities involved in their subsequent analysis.

Genetic Approaches for Neural Circuits Dissection in Non-human Primates

Genetic tools,which can be used for the morphology study of specific neurons,pathway-selective connectome mapping,neuronal activity monitoring,and manipulation with a spatiotemporal resolution,have been widely applied to the understanding of complex neural circuit formation,interactions,and functions in rodents.Recently,similar genetic approaches have been tried in non-human primates(NHPs)in neuroscience studies for dissecting the neural circuits involved in sophisticated behaviors and clinical brain disorders,although they are still very preliminary.In this review,we introduce the progress made in the development and application of genetic tools for brain studies on NHPs.We also discuss the advantages and limitations of each approach and provide a perspective for using genetic tools to study the neural circuits of NHPs.

Experimental primates and non-human primate(NHP) models of human diseases in China: current status and progress

Non-human primates （NHPs） are phylogenetically close to humans, with many similarities in terms of physiology, anatomy, immunology, as well as neurology, all of which make them excellent experimental models for biomedical research. Compared with developed countries in America and Europe, China has relatively rich primate resources and has continually aimed to develop NHPs resources. Currently, China is a leading producer and a major supplier of NHPs on the international market. However, there are some deficiencies in feeding and management that have hampered China＇s growth in NHP research and materials. Nonetheless, China has recently established a number of primate animal models for human diseases and achieved marked scientific progress on infectious diseases, cardiovascular diseases, endocrine diseases, reproductive diseases, neurological diseases, and ophthalmic diseases, etc. Advances in these fields via NHP models will undoubtedly further promote the development of China＇s life sciences and pharmaceutical industry, and enhance China＇s position as a leader in NHP research. This review covers the current status of NHPs in China and other areas, highlighting the latest developments in disease models using NHPs, as well as outlining basic problems and proposing effective to better utilize NHP resources and further foster NHP research in China.

Comparative analysis of primate and pig cells reveals primate-specific PINK1 expression and phosphorylation

PTEN-induced putative kinase 1(PINK1),a mitochondrial kinase that phosphorylates Parkin and other proteins,plays a crucial role in mitophagy and protection against neurodegeneration.Mutations in PINK1 and Parkin can lead to loss of function and early onset Parkinson's disease.However,there is a lack of strong in vivo evidence in rodent models to support the theory that loss of PINK1 affects mitophagy and induces neurodegeneration.Additionally,PINK1 knockout pigs(Sus scrofa)do not appear to exhibit neurodegeneration.In our recent work involving non-human primates,we found that PINK1 is selectively expressed in primate brains,while absent in rodent brains.To extend this to other species,we used multiple antibodies to examine the expression of PINK1 in pig tissues.In contrast to tissues from cynomolgus monkeys(Macaca fascicularis),our data did not convincingly demonstrate detectable PINK1expression in pig tissues.Knockdown of PINK1 in cultured pig cells did not result in altered Parkin and BAD phosphorylation,as observed in cultured monkey cells.A comparison of monkey and pig striatum revealed more PINK1-phosphorylated substrates in the monkey brain.Consistently,PINK1 knockout in pigs did not lead to obvious changes in the phosphorylation of Parkin and BAD.These findings provide new evidence that PINK1expression is specific to primates,underscoring the importance of non-human primates in investigating PINK1function and pathology related to PINK1 deficiency.

The 3rd Symposium on Animal Models of Primates——The Application of Non-Human Primates to Basic Research and Translational Medicine

In order to understand the fundamental questions of the biology of life and to duplicate the pathogenesis of human diseases, animal models using different experimental animals, such as rodents, Drosophila, Caenorhabditis elegans, and zebrafish, have been established and used widely for many decades. The controllability of environmental conditions, the high reproducibility, the ease of scale and the comparability of results, as well as the ability to use different standards for ethical protocols, all make an animal model the ideal tool for carrying out studies on human diseases and the development of novel pharmaceuticals and new therapies （Xue et al., 2014）. An ideal animal model should reflect the complete spectra of a specific human disease, with similar features on the following key issues： （1） genetic basis; （2） anatomy and physiology; （3） pathological response（s） and underlying mechanism（s）; （4） phenotypic endpoints as clinical studies; （5） responsiveness to known drugs with clinical efficacy; and （6） prediction of clinical efficacy （McGonigle and Ruggeri, 2014）.

Cortical Representation of Pain and Touch:Evidence from Combined Functional Neuroimaging and Electrophysiology in Non-human Primates

Human functional MRI studies in acute and various chronic pain conditions have revolutionized how we view pain, and have led to a new theory that complex multi-dimensional pain experience （sensory-discriminative, affective/motivational, and cognitive） is represented by concurrent activity in widely-distributed brain regions （termed a network or pain matrix）. Despite these break- through discoveries, the specific functions proposed for these regions remain elusive, because detailed electrophys- iological characterizations of these regions in the primate brain are lacking. To fill in this knowledge gap, we have studied the cortical areas around the central and lateral sulci of the non-human primate brain with combined submillimeter resolution functional imaging （optical imaging and fMRI） and intracranial electrophysiological recording. In this mini-review, I summarize and present data showing that the cortical circuitry engaged in nociceptive processing is much more complex than previously recognized. Electrophysiological evidence supports the engage- ment of a distinct nociceptive-processing network within SI （i.e., areas 3a, 3b, 1 and 2）, SII, and other areas along the lateral sulcus. Deafferentation caused by spinal cord injury profoundly alters the relationships between fMRI and electrophysiological signals. This finding has significant implications for using fMRI to study chronic pain conditions involving deafferentation in humans.