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.

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.

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.

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.

Taking central nervous system regenerative therapies to the clinic: curing rodents versus nonhuman primates versus humans

The central nervous system is known to have limited regenerative capacity.Not only does this halt the human body’s reparative processes after central nervous system lesions,but it also impedes the establishment of effective and safe therapeutic options for such patients.Despite the high prevalence of stroke and spinal cord injury in the general population,these conditions remain incurable and place a heavy burden on patients’families and on society more broadly.Neuroregeneration and neural engineering are diverse biomedical fields that attempt reparative treatments,utilizing stem cells-based strategies,biologically active molecules,nanotechnology,exosomes and highly tunable biodegradable systems(e.g.,certain hydrogels).Although there are studies demonstrating promising preclinical results,safe clinical translation has not yet been accomplished.A key gap in clinical translation is the absence of an ideal animal or ex vivo model that can perfectly simulate the human microenvironment,and also correspond to all the complex pathophysiological and neuroanatomical factors that affect functional outcomes in humans after central nervous system injury.Such an ideal model does not currently exist,but it seems that the nonhuman primate model is uniquely qualified for this role,given its close resemblance to humans.This review considers some regenerative therapies for central nervous system repair that hold promise for future clinical translation.In addition,it attempts to uncover some of the main reasons why clinical translation might fail without the implementation of nonhuman primate models in the research pipeline.

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.

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.

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.

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.

Conserved sequences identify the closest living relatives of primates

Elucidating the closest living relatives of extant primates is essential for fully understanding important biological processes related to the genomic and phenotypic evolution of primates, especially of humans. However, the phylogenetic placement of these primate relatives remains controversial, with three primary hypotheses currently espoused based on morphological and molecular evidence. In the present study, we used two algorithms to analyze differently partitioned genomic datasets consisting of 45.4 Mb of conserved non-coding elements and 393 kb of concatenated coding sequences to test these hypotheses. We assessed different genomic histories and compared with other molecular studies found solid support for colugos being the closest living relatives of primates. Our phylogeny showed Cercopithecinae to have low levels of nucleotide divergence, especially for Papionini, and gibbons to have a high rate of divergence. The MCMCtree comprehensively updated divergence dates of early evolution of Primatomorpha and Primates.

Preliminary analysis of the mitochondrial genome evolutionary pattern in primates

Since the birth of molecular evolutionary analysis,primates have been a central focus of study and mitochondrial DNA is well suited to these endeavors because of its unique features.Surprisingly,to date no comprehensive evaluation of the nucleotide substitution patterns has been conducted on the mitochondrial genome of primates.Here,we analyzed the evolutionary patterns and evaluated selection and recombination in the mitochondrial genomes of 44 Primates species downloaded from GenBank.The results revealed that a strong rate heterogeneity occurred among sites and genes in all comparisons.Likewise,an obvious decline in primate nucleotide diversity was noted in the subunit rRNAs and tRNAs as compared to the protein-coding genes.Within 13 protein-coding genes,the pattern of nonsynonymous divergence was similar to that of overall nucleotide divergence,while synonymous changes differed only for individual genes,indicating that the rate heterogeneity may result from the rate of change at nonsynonymous sites.Codon usage analysis revealed that there was intermediate codon usage bias in primate protein-coding genes,and supported the idea that GC mutation pressure might determine codon usage and that positive selection is not the driving force for the codon usage bias.Neutrality tests using site-specific positive selection from a Bayesian framework indicated no sites were under positive selection for any gene,consistent with near neutrality.Recombination tests based on the pairwise homoplasy test statistic supported complete linkage even for much older divergent primate species.Thus,with the exception of rate heterogeneity among mitochondrial genes,evaluating the validity assumed complete linkage and selective neutrality in primates prior to phylogenetic or phylogeographic analysis seems unnecessary.

Preliminary analysis of the mitochondrial genome evolutionary pattern in primates

Since the birth of molecular evolutionary analysis, primates have been a central focus of study and mitochondrial DNA is well suited to these endeavors because of its unique features. Surprisingly, to date no comprehensive evaluation of the nucleotide substitution patterns has been conducted on the mitochondrial genome of primates. Here, we analyzed the evolutionary patterns and evaluated selection and recombination in the mitochondrial genomes of 44 Primates species downloaded from Genl3ank. The results revealed that a strong rate heterogeneity occurred among sites and genes in all comparisons. Likewise, an obvious decline in primate nucleotide diversity was noted in the subunit rRNAs and tRNAs as compared to the protein-coding genes. Within 13 protein-coding genes, the pattern of nonsynonymous divergence was similar to that of overall nucleotide divergence, while synonymous changes differed only for individual genes, indicating that the rate heterogeneity may result from the rate of change at nonsynonymous sites. Codon usage analysis revealed that there was intermediate codon usage bias in primate protein-coding genes, and supported the idea that GC mutation pressure might determine codon usage and that positive selection is not the driving force for the codon usage bias. Neutrality tests using site-specific positive selection from a Bayesian framework indicated no sites were under positive selection for any gene, consistent with near neutrality. Recombination tests based on the pairwise homoplasy test statistic supported complete linkage even for much older divergent primate species. Thus, with the exception of rate heterogeneity among mitochondrial genes, evaluating the validity assumed complete linkage and selective neutrality in primates prior to phylogenetic or phylogeographic analysis seems unnecessary.

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.

Comparative evaluation of acute phase proteins by C-reactive protein(CRP)and serum amyloid A(SAA)in nonhuman primates and feline carnivores

The feasibility of a commercially available assay for C-reactive protein(CRP,CRP for humans:hCRP,and CRP for dogs:vCRP)and a trial reagent of serum amyloid A(SAA,vSAA for animals)were applied to the measurement of acute phase proteins in zoo animals,particularly in nonhuman primates and feline carnivores was evaluate.Results showed that hCRP and vSAA methods were applicable to measure CRP and SAA in Haplorhini.There was a highly signifcant correlation between both parameters with remarkably high correlation coefcient.A higher proportion of Bonnet macaques in Haplorhini,and the linear regression with good correlation between hCRP and vSAA levels were observed.Reference values in healthy Bonnet macaques were hCRP(46.86±30.97 nmol/L)and vSAA(9.06±1.95μg/mL).Although Ring-tailed lemur,which belonging to Strepsirrhini,showed low vSAA concentrations(reference values:1.08±0.47μg/mL),vSAA in patients was apparently elevated.The vCRP and vSAA methods were applicable to measurements of CRP and SAA in feline carnivores for highly signifcant correlation between both parameters.Theses two methods were also been deteded in lions,tigers and cheetahs.vSAA assays can be applied to measure SAA levels in other carnivores and herbivores.In conclusion,vSAA systems have potential utility as diagnostic tools for health screening and prediction in zoo animals.

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.

Habitat Suitability Modeling of Endangered Primates in Nigeria: Integrating Satellite Remote Sensing and Spatial Modeling Techniques

This paper investigates the impacts of forest cover and spatial structure changes on the forest landscape across Afi-Mbe-Okwangwo protected area of Cross River State, Nigeria and its corresponding implication on two endangered primates (Cross River Gorilla and Nigeria-Cameroon Chimpanzee) habitat using satellite remote sensing and modeling techniques. Using remote sensing change detection analysis, the spatial extent and annual rate of deforestation for the study area was determined as 34,620 hectares and 1.5% respectively (from 2000 to 2014). The protected areas with highest annual deforestation rates were Afi Mountain Wildlife Sanctuary (2.6%) and Mbe Mountains (2.2%), both prominent for gorilla and chimpanzee sightings and nests. Further investigations on changes to the forest landscape structure revealed high levels of forest fragmentation across the study area for the 14-year period investigated. As a means of further understanding effects of forest landscapes changes across the study area, a 14-year forward simulation was performed using the Markov model as to determine the spatial extent of futuristic forest cover changes. The results showed that if this current trend of forest cover change continued, 28,121 hectares of forests would be lost to deforestation in 2028 (approximately 16% of the total landmass of the entire study area). Using Maxent modeling, suitable primate habitats were predicted and the total coverage determined as 30,940 hectares (54.4% situated in CRNP—Okwangwo division, 29.4% in AMWS, 14.3% in Mbe Mountains and 1.9% in ARFR). Further analysis revealed 6468 hectares of predicted primate habitat were affected by deforestation in 2014 (21% of the predicted primate habitats). These results indicate that suitable primate habitats (particularly for gorillas and chimpanzees) are under immense pressure from deforestation and forest fragmentation. This paper presents a cost effective and time saving approach for determining suitable primate habitats and understanding the effects of forest transition on primate habitat suitability.

Louis Pierre Gratiolet (1815-1865) and His Contribution to the Study of Cerebral Convolutions in Primates

Louis Pierre Gratiolet (1815-1865) was one of the first modern anatomists to pay attention to cerebral convolutions. Born in Sainte-Foy-la-Grande (Gironde), he moved to Paris in 1834 to study medicine, as well as comparative anatomy under Henri de Blainville (1777-1850). In 1842, he accepted de Blainville’s offer to become his assistant at the Muséum d’histoire naturelle and progressively abandoned medicine for comparative anatomy. He undertook a detailed study of brains of human and nonhuman primates and soon realized that the organizational pattern of cerebral convolutions was so predictable that it could serve as a criterion to classify primate groups. He noted that only the deepest sulci exist in lower primate forms, while the complexity of cortical folding increases markedly in great apes and humans. Gratiolet provided the first cogent description of the lobular organization of primate cerebral hemispheres. He saw the insula as a central lobe around which revolved the frontal, parietal, temporal (temporo-sphenoidal) and occipital lobes. He correctly identified most gyri and sulci on all brain surfaces, introduced the term “plis de passage” for some interconnecting gyri, and provided the first description of the optic radiations. In the early 1860s, Gratiolet fought a highly publicized battle against Paul Broca (1824-1880) on the relationship between brain and intelligence. Gratiolet agreed that the brain was most likely the seat of intelligence, but he considered human cognition far too subtle to have any direct relationship with brain size. He argued that a detailed study of the human brain architecture would be more profitable than Broca’s vain speculations on the relationship between brain weight and intelligence, which he considered a monolithic entity. Despite remarkable scientific achievements and a unique teaching capacity, Gratiolet was unable to secure any academic position until three years before his sudden death in Paris at age 49.