Monkey Model Research Articles

Stem cell transplantation extends the reproductive life span of naturally aging cynomolgus monkeys

The ovary is crucial for female reproduction and health, as it generates oocytes and secretes sex hormones. Transplantation of mesenchymal stem cells (MSCs) has been shown to alleviate pathological ovarian aging. However, it is unclear whether MSCs could benefit the naturally aging ovary. In this study, we first examined the dynamics of ovarian reserve of Chinese women during perimenopause. Using a naturally aging cynomolgus monkey (Macaca fascicularis) model, we found that transplanting human embryonic stem cells-derived MSC-like cells, which we called M cells, into the aging ovaries significantly decreased ovarian fibrosis and DNA damage, enhanced secretion of sex hormones and improved fertility. Encouragingly, a healthy baby monkey was born after M-cell transplantation. Moreover, single-cell RNA sequencing analysis and in vitro functional validation suggested that apoptosis, oxidative damage, inflammation, and fibrosis were mitigated in granulosa cells and stromal cells following M-cell transplantation. Altogether, these findings demonstrate the beneficial effects of M-cell transplantation on aging ovaries and expand our understanding of the molecular mechanisms underlying ovarian aging and stem cell-based alleviation of this process.

Evidence for interacting but decoupled controls of decisions and movements in nonhuman primates.

Many recent studies indicate that control of decisions and actions is integrated during interactive behavior. Among these, several carried out in humans and monkeys conclude that there is a coregulation of choices and movements. Another perspective, based on human data only, proposes a decoupled control of decision duration and movement speed, allowing, for instance, trading decision duration for movement duration when time pressure increases. Crucially, it is not currently known whether this ability to flexibly dissociate decision duration from movement speed is specific to humans, whether it can vary depending on the context in which a task is performed, and whether it is stable over time. These are important questions to address, especially to rely on monkey electrophysiology to infer the neural mechanisms of decision-action coordination in humans. To do so, we trained two macaque monkeys in a perceptual decision-making task and analyzed data collected over multiple behavioral sessions. Our findings reveal a strong and complex relationship between decision duration and movement vigor. Decision duration and action duration can covary but also "compensate" each other. Such integrated but decoupled control of decisions and actions aligns with recent studies in humans, validating the monkey model in electrophysiology as a means of inferring neural mechanisms in humans. Crucially, we demonstrate for the first time that this control can evolve with experience, in an adapted manner. Together, the present findings contribute to deepening our understanding of the integrated control of decisions and actions during interactive behavior.NEW & NOTEWORTHY The mechanism by which the integrated control of decisions and actions occurs, coupled or interactive but decoupled, is debated. In the present study, we show in monkeys that decisions and actions influence each other in a decoupled way. For the first time, we also demonstrate that this control can evolve depending the subject's experience, allowing the trade of movement time for decision time and limiting the temporal discounting of reward value.

Translational Insights From Cell Type Variation Across Amygdala Subnuclei in Rhesus Monkeys and Humans.

Theories of amygdala function are central to our understanding of psychiatric and neurodevelopmental disorders. However, limited knowledge of the molecular and cellular composition of the amygdala impedes translational research aimed at developing new treatments and interventions. The aim of this study was to characterize and compare the composition of amygdala cells to help bridge the gap between preclinical models and human psychiatric and neurodevelopmental disorders. Tissue was dissected from multiple amygdala subnuclei in both humans (N=3, male) and rhesus macaques (N=3, male). Single-nucleus RNA sequencing was performed to characterize the transcriptomes of individual nuclei. The results reveal substantial heterogeneity between regions, even when restricted to inhibitory or excitatory neurons. Consistent with previous work, the data highlight the complexities of individual marker genes for uniquely targeting specific cell types. Cross-species analyses suggest that the rhesus monkey model is well-suited to understanding the human amygdala, but also identify limitations. For example, a cell cluster in the ventral lateral nucleus of the amygdala (vLa) is enriched in humans relative to rhesus macaques. Additionally, the data describe specific cell clusters with relative enrichment of disorder-related genes. These analyses point to the human-enriched vLa cell cluster as relevant to autism spectrum disorder, potentially highlighting a vulnerability to neurodevelopmental disorders that has emerged in recent primate evolution. Further, a cluster of cells expressing markers for intercalated cells is enriched for genes reported in human genome-wide association studies of neuroticism, anxiety disorders, and depressive disorders. Together, these findings shed light on the composition of the amygdala and identify specific cell types that can be prioritized in basic science research to better understand human psychopathology and guide the development of potential treatments.

Monkey model of DMD.

Monkey model of DMD.

Pelvic Floor Muscle Anatomy and its Contribution to Penile Erection in Olive Baboons.

Despite the number of studies on the contribution of pelvic floor muscles (PFM) to the penile erection process, their significance is still underestimated. The goal of this study was to investigate the role of PFM in the erection process in non-human primates. First, we performed an anatomical study of the penile structures in 12 baboon cadavers. Next, we created chronic electrophysiological models of normal erectile function in 25 olive baboons. We implanted electrodes on the cavernous nerves to control penile blood filling and placed other electrodes on the pudendal nerve to stimulate the ischiocavernosus muscles (ICM) contractions after sufficient blood filling, thus simulating both vascular and muscular phases of penile erection. We controlled the intracavernous pressure (ICP) during nerve stimulations and further performed a mathematical analysis of the collected data. We described the main pro-erectile muscle anatomy and its relationship with penile structures in monkeys. During neurostimulation studies, we showed the key role of ICM in achieving full penile rigidity with suprasystolic ICP up to 120-300 mm Hg. We also developed a math model for calculating the pro-erectile muscle's contraction force with high accuracy. In this study, we demonstrated the crucial role of PFM in the penile erection process using the monkey model, supporting the previous studies' data. We consider these results essential for a better, more complex understanding of the penile erection process and the participating structures in each stage. This is essential for further improving and designing novel erectile dysfunction diagnostics and treatment techniques.

Deficiency of parkin causes neurodegeneration and accumulation of pathological α-synuclein in monkey models.

Parkinson's disease (PD) is characterized by age-dependent neurodegeneration and the accumulation of toxic phosphorylated α-synuclein (pS129-α-syn). The mechanisms underlying these crucial pathological changes remain unclear. Mutations in parkin RBR E3 ubiquitin protein ligase (PARK2), the gene encoding parkin that is phosphorylated by PTEN-induced putative kinase 1 (PINK1) to participate in mitophagy, cause early onset PD. However, current parkin-KO mouse and pig models do not exhibit neurodegeneration. In the current study, we utilized CRISPR/Cas9 technology to establish parkin-deficient monkey models at different ages. We found that parkin deficiency leads to substantia nigra neurodegeneration in adult monkey brains and that parkin phosphorylation decreases with aging, primarily due to increased insolubility of parkin. Phosphorylated parkin is important for neuroprotection and the reduction of pS129-α-syn. Consistently, overexpression of WT parkin, but not a mutant form that cannot be phosphorylated by PINK1, reduced the accumulation of pS129-α-syn. These findings identify parkin phosphorylation as a key factor in PD pathogenesis and suggest it as a promising target for therapeutic interventions.

Modeling the pre-symptomatic stage of hemi-parkinsonian state in animals (rodents and monkeys)

The behavioral and functional states preceding the onset specific parkinsonian symptoms were studied at an early (pre-symptomatic) stage of hemi-parkinsonian syndrome development in rodents and monkeys. The pre-symptomatic stage of the hemi-parkinsonian syndrome was determined in rodents (mice and rats) treated by chronic administration of low doses of rotenone toxin. The consecutive steps of neuropathological traits development in rodents included the cognitive impairment at the 1st-2nd week of exposure to rotenone, minor movement disorders at the 3st-4nd week before the onset of severe motor dysfunction as well as some biochemical indicators. The latencies and amplitudes of visually guided saccades (VGS) while conditioned instrumental task performing were studied in nonhuman primates (Macaca mulatta) chronically treated with low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The elongation of VGS latencies and the decline of their accuracy were revealed with development of MPTP-induces syndrome but conditioned instrumental performance was not affected. The negative behavioral effects manifested in animals at the pre-symptomatic stage of toxins induced disease both in the rotenone model in rodents and in MPTP model in monkeys suggesting them as early markers of a hemi-parkinsonian syndrome.

An accelerated Parkinson’s disease monkey model using AAV-α-synuclein plus poly(ADP-ribose)

The etiology of Parkinson's disease (PD) remains elusive, and the limited availability of suitable animal models hampers research on pathogenesis and drug development. We report the development of a cynomolgus monkey model of PD that combines adeno-associated virus (AAV)-mediated overexpression of α-synuclein into the substantia nigra with an injection of poly(ADP-ribose) (PAR) into the striatum. Our results show that pathological processes were accelerated, including dopaminergic neuron degeneration, Lewy body aggregation, and hallmarks of inflammation in microglia and astrocytes. Behavioral phenotypes, dopamine transporter imaging, and transcriptomic profiling further demonstrate consistencies between the model and patients with PD. This model can help to determine the mechanisms underlying PD impacted by α-synuclein and PAR and aid in the accelerated development of therapeutic strategies for PD.

Mucus-inspired lubricative antibacterial coating to reduce airway complications in an intubation cynomolgus monkey model

Endotracheal intubation-related complications are common in clinical, and there are currently no effective strategies to address these matters. Inspired by the biological characteristics of human airway mucus (HAM), an artificial airway mucus (ARM) coating is straightforwardly constructed by combining carboxymethyl chitosan with methyl cellulose. The ARM coating exhibited excellent lubricity (coefficient of friction (CoF) = 0.05) and hydrophilicity (water contact angle (WCA) = 21.3°), and was capable of coating both the internal and external surfaces of the endotracheal tube (ETT). In vitro experiments demonstrated that the ARM coating not only showed good broad-spectrum antibacterial activity, but also significantly reduced nonspecific protein adhesion. Through an in vivo intubation cynomolgus monkey model, ARM-coated ETT potently mitigated airway injury and inflammation, and was highly potential to prevent bacterial infection and catheter blockage. This work offers a promising avenue for the development of airway-friendly invasive devices.

Evaluation of A Non-Nucleoside Inhibitor of the RSV RNA-Dependent RNA Polymerase in Translatable Animals Models

Respiratory Syncytial Virus (RSV) causes severe respiratory infections and concomitant disease resulting in significant morbidity and mortality in infants, elderly, and immunocompromised adults. Vaccines, monoclonal antibodies, and small molecule antivirals are now either available, or in development, to prevent and treat RSV infections. Although, rodent and non-rodent preclinical animal models have been used to evaluate these emerging agents there is still a need to improve our understanding of the pharmacokinetic (PK)-pharmacodynamic (PD) relationships, within and between animal models to enable better design of human challenge studies and clinical trials. Herein, we report a PKPD evaluation of MRK-1, a novel small molecule non-nucleoside inhibitor of the RSV L polymerase protein, in the semi-permissive cotton rat and African green monkey models of RSV infection. These studies demonstrate a strong relationship between in vitro activity, in vivo drug exposure, and pharmacodynamic efficacy as well as revealing limitations of the cotton rat RSV model. Additionally, we report unexpected horizontal transmission of human RSV between co-housed African green monkeys, as well as a lack of drug specific resistant mutant generation. Taken together these studies further our understanding of these semi-permissive animal models and offer the potential for expansion of their preclinical utility in evaluating novel RSV therapeutic agents.

Therapeutic efficacy and in vivo distribution of human umbilical cord-derived mesenchymal stem cell spheroids transplanted via B-Ultrasound-guided percutaneous portal vein puncture in rhesus monkey models of liver fibrosis

BackgroundLiver fibrosis can progress to end-stage cirrhosis and liver cancer. Mesenchymal stem cells (MSCs) were considered the most promising therapeutic strategy, but most of the MSCs injected intravenously traditionally are trapped in the lungs, rapidly reducing their survival ability. MSC spheroids cultured in 3D have shown higher tolerance to fluid shear stress and better survival than dissociated MSCs. Simulating the route of orthotopic liver transplantation, transplanting MSC spheroids into the liver via hepatic portal vein may impact superior therapeutic effects.MethodsIn the present study, human umbilical cord-derived MSC spheroids (hUC-MSCsp) were transplanted into rhesus monkey models of liver fibrosis via B-ultrasound-guided percutaneous portal vein puncture with minimized body invasion. The therapeutic effect is evaluated through hematology, ultrasound, and pathology. To study the effect of hUC-MSCsp on gene expression in rhesus monkeys with liver injury, transcriptome sequencing analysis was performed on the livers of rhesus monkeys. The distribution of transplanted hUC-MSCsp was traced with RNA scope technology.ResultsWe found that hUC-MSCsp significantly restored liver function, including ALT, AST, ALB, GLOB and bilirubin. hUC-MSCsp also significantly reduced liver collagen deposition and inflammatory infiltration, and promote dismission of liver ascites. Subsequently, the therapeutic effects were further validated in TGF-β1/Smad pathway by global transcription profile. The distribution of transplanted hUC-MSCsp were also tracked, and we found that hUC-MSCsp distributed in the liver in a sphere status at 1 h after transplantation. After 16 days, the hUC-MSCsp were dispersed into dissociated cells that were predominantly distributed in the spleen, and a significant number of dissociated cells were still present in the liver.ConclusionsThis study reveals the distributions of transplanted hUC-MSCsp after liver portal vein transplantation, and provides a novel approach and new insights into the molecular events of potential molecular events underlying the treatment of liver fibrosis with hUC-MSCsp.

Age-Related Features of the Function of the Hypothalamic-Pituitary-Thyroid (HPT) Axis in Nonhuman Primates under Constant Lighting.

We studied the features of the functioning of the hypothalamic-pituitary-thyroid (HPT) axis under conditions of constant (4 weeks) lighting (LED lamps intended for office and residential premise) on a translational model of young adult and old female rhesus monkeys, in particular taking into account their behavior. Constant lightning had no significant effect on the levels of thyroid-stimulating hormone, thyroxine, and triiodothyronine under basal conditions in all animals, regardless of age and behavioral characteristics, but induced a decrease in thyroid function under conditions of its activation with thyrotropin-releasing hormone, mainly in old animals.

The Tree Shrew Model of Parkinson Disease: A Cost-Effective Alternative to Nonhuman Primate Models

The surge in demand for experimental monkeys has led to a rapid increase in their costs. Consequently, there is a growing need for a cost-effective model of Parkinson disease (PD) that exhibits all core clinical and pathologic phenotypes. Evolutionarily, tree shrews (Tupaia belangeri) are closer to primates in comparison with rodents and could be an ideal species for modeling PD. To develop a tree shrew PD model, we used the 1-methyl-4-phenylpyridinium (MPP+), a metabolite derived from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, to induce lesions in dopaminergic neurons of the unilateral substantia nigra. The induced tree shrew model consistently exhibited and maintained all classic clinical manifestations of PD for a 5-month period. The symptoms included bradykinesia, rest tremor, and postural instability, and ∼50% individuals showed apomorphine-induced rotations, a classic phenotype of unilateral PD models. All these are closely resembled the ones observed in PD monkeys. Meanwhile, this model was also sensitive to L-dopa treatment in a dose-dependent manner, which suggested that the motor deficits are dopamine dependent. Immunostaining showed a significant loss of dopaminergic neurons (∼95%) in the lesioned substantia nigra, which is a crucial PD pathological marker. Moreover, a control group of nigral saline injection did not show any motor deficits and pathological changes. Cytomorphologic analysis revealed that the size of nigral dopaminergic neurons in tree shrews is much bigger than that of rodents and is close to that of macaques. The morphologic similarity may be an important structural basis for the manifestation of the highly similar phenotypes between monkey and tree shrew PD models. Collectively, in this study, we have successfully developed a PD model in a small animal species that faithfully recapitulated the classic clinical symptoms and key pathological indicators of PD monkeys, providing a novel and low-cost avenue for evaluation of PD treatments and underlying mechanisms.

Profound cellular defects attribute to muscular pathogenesis in the rhesus monkey model of Duchenne muscular dystrophy

Profound cellular defects attribute to muscular pathogenesis in the rhesus monkey model of Duchenne muscular dystrophy

Abstract P440: Discovery of clinical candidate GSC002219, a highly selective oral CYP11B2 inhibitor for hypertension

Background: Aldosterone is an important mediator of hypertension and its aberration could contribute to heart and kidney diseases. Aldosterone synthase inhibitors (ASI) attenuate the production of aldosterone directly and have been proposed as an alternative to mineralocorticoid receptor antagonists (MRA) for treatment of resistant hypertension and chronic renal disease. GSC002219 is a potent inhibitor of aldosterone synthase (CYP11B2) with high selectivity over the closely related enzyme CYP11B1. The aim of the study was to evaluate the effect of GSC002219 on aldosterone and blood pressure. Methods: The inhibitory effect of GSC002219 against CYP11B2 and CYP11B1 proteins was assessed in human renal leiomyoblastoma cells expressing recombinant human / cynomolgus CYP11B1or CYP11B2 enzymes, respectively. GSC002219 was further evaluated in Synacthen (ACTH) challenged cynomolgus monkey model for its effects against various related key biomarkers including cortisol, aldosterone and precursors. The effects of GSC002219 on systolic blood pressure (SBP) and diastolic blood pressure (DBP) were evaluated in stroke-prone spontaneously hypertensive rat (SHRSP) model. Results: GSC002219 potently inhibits CYP11B2 with an IC 50 of 27nM, while maintains a >150-fold selectivity over CYP11B1. In ACTH challenged cynomolgus monkey model, single oral doses of GSC002219 at 0.03 mg/kg and 0.1 mg/kg could suppress aldosterone production to 80% and 93%, respectively, comparing to vehicle-treated animals without any effect towards cortisol levels. In the rat SHRSP hypertension model, GSC002219 could effectively lower both SBP and DBP. GSC002219 has an excellent in vitro ADME and toxicology profile as well as a balanced physicochemical property. In 14-day rat and monkey toxicology studies, GSC002219 displayed good tolerance, excellent PK profile and a great safety window (>100 fold). Conclusions: Taken together, GSC002219 is a safe and potent inhibitor of CYP11B2 and efficacious in various disease models of hypertension. GSC002219 is under IND-enabling study and may enter the clinical development early 2025.

Passive Immunotherapy of Cynomolgus Monkeys with Anti-Rotavirus IgY.

Immunoglobulins Y (IgY) purified from egg yolks of hens represents an attractive, cost-effective alternative for the development of new diagnostic and therapeutic platforms. In this study, we evaluated the therapeutic efficacy of rotavirus-specific IgY in a cynomolgus monkey (Macaca fascicularis) model. Animals were experimentally infected with human rotavirus Group A (RVA), the most common cause of severe acute diarrhoea among young children worldwide. Animals were administered human RVA (3.1 × 107 FFU/mL) by oral gavage, challenged with 2.5 mg of anti-RVA IgY orally, and monitored for five days according to clinical, haematological and biochemical parameters; serum electrolyte levels; viral shedding; and histopathological changes. Immunotherapy with anti-RVA IgY had a protective effect against severe rotavirus-induced enteritis in four of the ten treated monkeys, as evidenced by histopathological findings. Although only one animal had diarrhoea, all but one exhibited virus shedding regardless of the treatment.

Non-human primate model of long-COVID identifies immune associates of hyperglycemia

Hyperglycemia, and exacerbation of pre-existing deficits in glucose metabolism, are manifestations of the post-acute sequelae of SARS-CoV-2. Our understanding of metabolic decline after acute COVID-19 remains unclear due to the lack of animal models. Here, we report a non-human primate model of metabolic post-acute sequelae of SARS-CoV-2 using SARS-CoV-2 infected African green monkeys. Using this model, we identify a dysregulated blood chemokine signature during acute COVID-19 that correlates with elevated and persistent hyperglycemia four months post-infection. Hyperglycemia also correlates with liver glycogen levels, but there is no evidence of substantial long-term SARS-CoV-2 replication in the liver and pancreas. Finally, we report a favorable glycemic effect of the SARS-CoV-2 mRNA vaccine, administered on day 4 post-infection. Together, these data suggest that the African green monkey model exhibits important similarities to humans and can be utilized to assess therapeutic candidates to combat COVID-related metabolic defects.

Temporal progression of tau pathology and neuroinflammation in a rhesus monkey model of Alzheimer's disease.

The understanding of the pathological events in Alzheimer's disease (AD) has advanced dramatically, but the successful translation from rodent models into efficient human therapies is still problematic. To examine how tau pathology can develop in the primate brain, we injected 12 macaques with a dual tau mutation (P301L/S320F) into the entorhinal cortex (ERC). An investigation was performed using high-resolution microscopy, magnetic resonance imaging (MRI), positron emission tomography (PET), and fluid biomarkers to determine the temporal progression of the pathology 3 and 6 months after the injection. Using quantitative microscopy targeting markers for neurodegeneration and neuroinflammation, as well as fluid and imaging biomarkers, we detailed the progression of misfolded tau spreading and the consequential inflammatory response induced by glial cells. By combining the analysis of several in vivo biomarkers with extensive brain microscopy analysis, we described the initial steps of misfolded tau spreading and neuroinflammation in a monkey model highly translatable to AD patients. Dual tau mutation delivery in the entorhinal cortex induces progressive tau pathology in rhesus macaques. Exogenous human 4R-tau coaptates monkey 3R-tau during transneuronal spread, in a prion-like manner. Neuroinflammatory response is coordinated by microglia and astrocytes in response to tau pathology, with microglia targeting early tau pathology, while astrocytes engaged later in the progression, coincident with neuronal death. Monthly collection of CSF and plasma revealed a profile of changes in several AD core biomarkers, reflective of neurodegeneration and neuroinflammation as early as 1 month after injection.

Characterization of a monkey model with experimental retinal damage induced by N-methyl-D-aspartate.

N-methyl-D-aspartate (NMDA)-induced retinal damage has been well studied in rodents, but the detailed mechanisms have not yet been characterized in nonhuman primates. Here, we characterized the retinal degenerative effects of NMDA on rhesus monkeys in vivo. NMDA saline or saline-only control was injected intravitreally to the randomly assigned eyes and contralateral eyes of four rhesus monkeys, respectively. The structural and functional changes of retina were characterized by optical coherence tomography and electroretinography on days 0, 4, 30 and 60 post injection. Both optic discs and macular areas of the NMDA-injected eyes initially presented with a transient retinal thickening, followed by continued retinal thinning. The initial, transient retinal thickening has also been observed in glaucoma patients, but this has not been reported in rodent NMDA models. This initial response was followed by loss of retina ganglion cells (RGCs), which is similar to glaucomatous optic neuropathy and other RGC-related retinal degenerations. The amplitudes of both the photopic negative response and pattern electroretinogram decreased significantly and remained low until the end of the study. Thus, the NMDA monkey model may serve as a more clinically relevant animal model of retinal damage.

Evaluating the effect of injection protocols on intrathecal solute dispersion in non-human primates: an in vitro study using a cynomolgus cerebrospinal fluid system

BackgroundAchieving effective drug delivery to the central nervous system (CNS) remains a challenge for treating neurological disorders. Intrathecal (IT) delivery, which involves direct injection into the cerebrospinal fluid (CSF), presents a promising strategy. Large animal studies are important to assess the safety and efficacy of most drugs and treatments and translate the data to humans. An understanding of the influence of IT injection parameters on solute distribution within the CNS is essential to optimize preclinical research, which would potentially help design human clinical studies.MethodsA three-dimensional (3D) in vitro model of a cynomolgus monkey, based on MRI data, was developed to evaluate the impact of lumbar injection parameters on intrathecal solute dispersion. The parameters evaluated were (a) injection location, (b) bolus volume, (c) flush volume, (d) bolus rate, and (e) flush rate. To simulate the CSF flow within the subarachnoid space (SAS), an idealized CSF flow waveform with both cardiac and respiratory-induced components was input into the model. A solution of fluorescein drug surrogate tracer was administered in the lumbar region of the 3D in vitro model filled with deionized water. After injection of the tracer, the CSF system wide-solute dispersion was imaged using high-resolution cameras every thirty seconds for a duration of three hours. To ensure repeatability each injection protocol was repeated three times. For each protocol, the average spatial–temporal distribution over three hours post-injection, the area under the curve (AUC), and the percent injected dose (%ID) to extra-axial CSF (eaCSF) at three hours were determined.ResultsThe changes to the lumbar injection parameters led to variations in solute distribution along the neuro-axis. Specifically, injection location showed the most impact, enhancing the delivery to the eaCSF up to + 10.5%ID (p = 0.0282) at three hours post-injection. Adding a post-injection flush of 1.5 ml at 1 ml/min increased the solute delivery to the eaCSF by + 6.5%ID (p = 0.0218), while the larger bolus volume resulted in a + 2.3%ID (p = 0.1910) increase. The bolus and flush rates analyzed had minimal, statistically non-significant effects.ConclusionThese results predict the effects of lumbar injection parameters on solute distribution in the intrathecal space in NHPs. Specifically, the choice of injection location, flush, and bolus volume significantly improved solute delivery to eaCSF. The in vitro NHP CSF model and results offer a system to help predict and optimize IT delivery protocols for pre-clinical NHP studies.