Echocardiographic evaluation of cardiac function in cynomolgus monkeys over a wide age range

Various cardiovascular diseases can be detected and diagnosed using echocardiography. The demand for cardiovascular system research using nonhuman primates is increasing, but echocardiographic references for nonhuman primates are limited. This report describes the first comparison of echocardiographic reference values in 247 normal cynomolgus monkeys (135 females, 112 males) over a wide age range. Echocardiography, electrocardiography, blood pressure and chest X-ray images were acquired under immobilization with intramuscular ketamine hydrochloride, then cardiac structure, function, and flow velocity were assessed. Cardiac hormone levels were also tested. We found that cardiac structures positively correlated with weight, that the size of these structures stabilized after reaching maturity and that cardiac output increased according to heart size. In contrast, fractional shortening of the left ventricle, ejection fraction and flow velocity showed no significant correlations with weight or age, and age and E wave correlated negatively. These findings appear sufficiently similar to those in humans to suggest that cynomolgus monkeys can serve as a suitable model of human cardiac disease. Our data should also prove useful for surveying cardiac dysfunction in monkeys.

Cerebrospinal Fluid Characterization in Cynomolgus Monkeys, Beagle Dogs, and Göttingen Minipigs

Intrathecal administration is an important route for drug delivery, and in pharmacology and toxicology studies, cerebrospinal fluid (CSF) collection and analysis is required for evaluating blood–brain barrier penetration and central nervous system exposure. The characteristics of CSF in commonly used nonrodent models are lacking. The purpose of this study is to evaluate and provide some insights into normal cellular and biochemical composition of CSF as well as diffusion potential following intrathecal injection across several nonrodent species. Cerebrospinal fluid samples were collected from the cerebellomedullary cistern of beagle dogs, cynomolgus monkeys, and Göttingen minipigs and analyzed for clinical chemistry and cytological evaluation. Diffusion into the intrathecal space following intrathecal injection was assessed following administration of a contrast agent using fluoroscopy. The predominant cell types identified in CSF samples were lymphocytes and monocytoid cells; however, lymphocytes were represented in a higher percentage in dogs and monkeys as opposed to monocytoid cells in minipigs. Clinical chemistry parameters in CSF revealed higher Cl⁻ concentrations than plasma, but lower K⁺, Ca²⁺, phosphorus, glucose, creatinine, and total protein levels consistent across all 3 species. Diffusion rates following intrathecal injection of iodixanol showed some variability with dogs, showing the greatest diffusion distance; however, the longest diffusion time through the intervertebral space, followed by monkeys and minipigs. Minimal diffusion was observed in minipigs, which could have been attributed to anatomical spinal constraints that have been previously identified in this species.

Atypical presentation and pathogenesis of a macaque lymphocryptoviral-associated B-cell lymphoma in a cynomolgus monkey

We report the unique pathogenesis and presentation of a rapidly progressive B-cell lymphoma in a 3-year-old female cynomolgus monkey on day 50 of a 13-week toxicity study. Clinical pathology evaluation revealed a marked leukocytosis with bicytopenia. A serum protein electrophoresis was consistent with monoclonal gammopathy. The architecture of the lymph node, spleen, and thymus were variably effaced by neoplastic cells, which also infiltrated other tissues. Immunohistochemistry of the affected tissues confirmed a predominant population of CD20+, CD79a+, CD3-, CD68-, and CD34-neoplastic cells. The full data best support a diagnosis of Stage V lymphoma. Nextgen sequencing and negative prestudy serology results suggested a recent infection by macaque lymphocryptovirus (mLCV) with a unique transcriptional profile comparable with a rarely observed direct LCV infection model. This infection model might be associated with a temporary lack of an LCV antigen-specific cytotoxic T-cell adaptive immune response. Consistent with the established mechanisms of LCV-related lymphoproliferation, MYC and BCL2L11 gene expression were increased and decreased, respectively. While there was no overt immunosuppression, immunophenotyping revealed the index animal had a relatively low NK cell count, which further decreased by >50% on day 24 of the study. In addition to the temporary lack of adaptive immunity, the low NK cell counts were suggestive of an impaired innate immunity to control the virally-transformed cells and the subsequent unchecked lymphoproliferation. To our knowledge, this is the first report of a Stage V lymphoma with a unique pathogenesis in an otherwise immunocompetent cynomolgus monkey.

Domesticated cynomolgus monkey embryonic stem cells allow the generation of neonatal interspecies chimeric pigs

Blastocyst complementation by pluripotent stem cell (PSC) injection is believed to be the most promising method to generate xenogeneic organs. However, ethical issues prevent the study of human chimeras in the late embryonic stage of development. Primate embryonic stem cells (ESCs), which have similar pluripotency to human ESCs, are a good model for studying interspecies chimerism and organ generation. However, whether primate ESCs can be used in xenogenous grafts remains unclear. In this study, we evaluated the chimeric ability of cynomolgus monkey (Macaca fascicularis) ESCs (cmESCs) in pigs, which are excellent hosts because of their many similarities to humans. We report an optimized culture medium that enhanced the anti-apoptotic ability of cmESCs and improved the development of chimeric embryos, in which domesticated cmESCs (D-ESCs) injected into pig blastocysts differentiated into cells of all three germ layers. In addition, we obtained two neonatal interspecies chimeras, in which we observed tissue-specific D-ESC differentiation. Taken together, the results demonstrate the capability of D-ESCs to integrate and differentiate into functional cells in a porcine model, with a chimeric ratio of 0.001–0.0001 in different neonate tissues. We believe this work will facilitate future developments in xenogeneic organogenesis, bringing us one step closer to producing tissue-specific functional cells and organs in a large animal model through interspecies blastocyst complementation.

In Vitro Induction of Human Embryonic Stem Cells into the Midbrain Dopaminergic Neurons and Transplantation in Cynomolgus Monkey

A simple, rapid, efficient, and specialized culture system was successfully developed in this study to induce human embryonic stem cells into dopaminergic neurons in vitro. It only took 5 days to generate quickly and directly a large number of homogeneous neural stem cell (NSC) spheres by the introduction of small molecules LDN (inhibitor of BMP [bone morphogenetic protein] pathway that inhibits BMP type I receptors ALK₂ and ALK₃), SB431542 (inhibitor of TGF-β/Activin/Dodal pathway that inhibits ALK₄, ALK₅, and ALK₇), CHIR99021 (inhibitors of GSK-3 [glycogen synthase kinase 3]), and basic fibroblast growth factor (bFGF). The dopaminergic neurons were successfully induced at day 25 (tyrosine hydroxylase [TH] expressed) and at day 32 (TH highly expressed) with high purity (TH/Tuj1: 84.14% and 93.15%, respectively) by the addition of FGF8 (fibroblast growth factor 8), sonic hedgehog (SHH), and Purmorphamine after the generation of NSC at day 5. And, the dopaminergic neurons induced by this system successfully survived and integrated into the striatum of cynomolgus monkey brain after transplantation, which verified the efficiency of the induction system developed in this study, suggesting the potential clinical application in cell therapy for neurological diseases.

Visualising reactive oxygen species in live mammals and revealing of ROS-related system

Of all the aerobic respiration by-products, cytotoxic superoxide derived from mitochondrial-leaked electrons, is the only one known to be disposed of intracellularly. Is this fate the only destiny for mitochondrial-leaked electrons? When Cynomolgus monkeys were injected intravenously with reactive oxygen species (ROS) indicators, the connective tissues of dura mater, facial fascia, pericardium, linea alba, dorsa fascia and other body parts, emitted specific and intense fluorescent signals. Moreover, the fluorescent signals along the linea alba of SD rats, did not result from the local presence of ROS but from the interaction of ROS indicators with electrons flowing through this tissue. Furthermore, the electrons travelling along the linea alba of mice were revealed to originate from mitochondria. These data suggest that mitochondrial-leaked electrons may be transported extracellularly to a hitherto undescribed system of connective tissues, which is pervasively networked, electrically conductive and metabolically related.

Comparative study of human and cynomolgus T-cell depletion with rabbit anti-thymocyte globulin (rATG) treatment-for dose adjustment in a non-human primate kidney transplantation model

Rabbit-antithymocyte globulin (rATG) is commonly used in kidney transplantation (KT) as an induction agent and is also commonly used in non-human primate (NHP) KT models. However, the optimal dose has not been reported. In this study, we evaluated which cumulative dose of rATG was most appropriate for transplantation in NHPs. Cynomolgus monkeys were treated with intravenous 5 mg/kg rATG (Thymoglobulin^®, Genzyme Ltd., UK) twice, on days 0 and 2 (a total of 10 mg/kg, n=2), or 4 times, on days 0, 1, 2, and 3 (a total of 20 mg/kg, n=6). In addition, we performed allo-KT in cynomolgus monkeys (n=4) with a cumulative 20 mg/kg dose of rATG with optimized dosing for induction therapy. We further compared immune cells, including naïve, central memory, and effector memory T cells, in reconstituted distributions in human KT patients (n=22). The kinetics of lymphocytes showed a rapid decrease at day 1 that was maintained for 2 weeks in the 20 mg/kg rATG group, while lymphocyte depletion was not maintained for more than 1 week in the 10 mg/kg rATG group. During the early period of rATG treatment in the NHP-KT model, the frequency of total T cells in the 20 mg/kg group showed a pattern of depletion similar with that of KT patients treated with rATG (1.5 mg/kg, 3 days). However, the pattern of reconstituted T cell subpopulations was different, as the number of effector memory cells rebounded in the NHP-KT model. These data indicate that lymphocyte-depletion induced by rATG was influenced by cumulative dose, and that an rATG dose of 20 mg/kg is suitable for induction therapy in renal transplantation in cynomolgus monkeys compared to human KT.

Cyclophosphamide and fludarabine monophosphate dose optimization for the non-myeloablative condition in non-human primates to induce transient mixed chimerism via bone marrow transplantation

Bone marrow preconditioning using cyclophosphamide (CP) is generally used for bone marrow transplantation (BMT). However, because of CP's hepatotoxicity and nephrotoxicity, additional fludarabine (FDR) administration and a reduced dose of CP are used for reduced-intensity preconditioning. Recently, preclinical studies using non-human primates (NHPs) were performed to induce immune tolerance after solid organ transplantation by conducting BMT simultaneously. However, dose optimization of CP and FDR for BMT preconditioning in cynomolgus monkeys has not been conducted. Therefore, the objective of this study was to evaluate the efficacy and tolerability of induction protocols using different doses of CP and FDR. Our results showed that relatively low-dose CP (30 mg/kg×2) combined with additional high-dose FDR (60 mg/m²×4) was associated with sufficient suppression in periphery as well as in bone marrow compared with high-dose CP (60 mg/kg×2) combined with low-dose FDR (30 mg/m²×4) and did not show hepatic or renal toxicity. CD34⁺ stem cells were also well suppressed with both doses. Therefore, we concluded that the combination of 60 mg/kg of CP with 240 mg/m² of FDR can be used effectively and safely for non-myeloablative preconditioning for BMT in cynomolgus monkeys.

PKPD Assessment of the Anti-CD20 Antibody Obinutuzumab in Cynomolgus Monkey is Feasible Despite Marked Anti-Drug Antibody Response in This Species

The pharmacokinetics (PK) of the anti-CD20 monoclonal antibody obinutuzumab was assessed after single intravenous dosing to cynomolgus monkeys. In addition, the pharmacokinetic-pharmacodynamic (PKPD) relationship for B-cell depletion was characterized. The PKPD model was used to estimate the B-cell repopulation during the recovery phase of chronic toxicology studies, thereby supporting the study design, in particular planning the recovery phase duration. Marked immunogenicity against obinutuzumab was observed approximately 10 days after single dose, leading to an up to ∼30-fold increase in obinutuzumab clearance in the affected monkeys. Despite this accelerated clearance, the PK could be characterized, either by disregarding the clearance in noncompartmental PK analysis or by capturing it explicitly as an additional time-dependent clearance process in compartmental modeling. This latter step was crucial to model the PKPD of B-cells as an indirect response to obinutuzumab exposure, showing that-without immune response-the limiting factor is obinutuzumab elimination with concentrations below 0.02 μg/mL required for initiation of B-cell recovery. Overall, the results demonstrate that despite a marked anti-drug antibody response in the nonclinical animal species, the PK and PKPD of obinutuzumab could be characterized successfully by appropriately addressing the immune-modulated clearance pathway in data analysis and modeling.

A Sensitive and Selective Immunoassay for the Quantitation of Serum Latent Myostatin after In Vivo Administration of SRK-015, a Selective Inhibitor of Myostatin Activation

Myostatin, a member of the transforming growth factor β (TGFβ) superfamily, is a key regulator of skeletal muscle mass and a therapeutic target for muscle wasting diseases. We developed a human monoclonal antibody, SRK-015, that selectively binds to and inhibits proteolytic processing of myostatin precursors, thereby preventing growth factor release from the latent complex. As a consequence of antibody binding, latent myostatin accumulates in the circulation of animals treated with SRK-015 or closely related antibodies, suggesting that quantitation of latent myostatin in serum may serve as a biomarker for target engagement. To accurately measure SRK-015 target engagement, we developed a sensitive plate-based electrochemiluminescent immunoassay to quantitate latent myostatin in serum samples. The assay selectively recognizes latent myostatin without cross-reactivity to promyostatin, mature myostatin, or closely related members of the TGFβ superfamily. To enable use of the assay in samples from animals dosed with SRK-015, we incorporated a low-pH step that dissociates SRK-015 from latent myostatin, improving drug tolerance of the assay. The assay meets inter- and intra-assay accuracy and precision acceptance criteria, and it has a lower limit of quantitation (LLOQ) of 10 ng/mL. We then tested serum samples from a pharmacology study in cynomolgus monkeys treated with SRK-015. Serum latent myostatin increases after treatment with SRK-015, reaches a dose-dependent plateau approximately 20 days after dosing, and trends back toward baseline after cessation of antibody dosing. Taken together, these data suggest that this assay can be used to accurately measure levels of the primary circulating form of myostatin in population-based or pharmacodynamic studies.

Establishment of a new formula for QT interval correction using a large colony of cynomolgus monkeys

The demand for monkeys for medical research is increasing, because their ionic mechanism of repolarization is similar to that of humans. The QT interval is the distance between the Q wave and T wave, but this interval is affected by heart rate. Therefore, QT correction methods are commonly used in clinical settings. However, an accurate correction formula for the QT interval in cynomolgus monkeys has not been reported. We assessed snapshot electrocardiograms (ECGs) of 353 ketamine-immobilized monkeys, including aged animals, and contrived a new formula for the corrected QT interval (QTc) as a marker of QT interval prolongation in cynomolgus monkeys. Values for QTc were calculated using the formula [QTc] = [QT] / [RR]ⁿ, along with several other formulas commonly used to calculate QTc. We found that the optimal exponent of the QT interval corrected for heart rate, n, was 0.576. The mean value of QTc in healthy monkeys determined using the new formula was 373 ± 31 mm, and there were no significant differences between the sexes. Other ECG parameters were not significantly different between the sexes and there were no age-related effects on QTc. Prolongation of QTc to over 405 ms, as calculated by the new formula, was observed in 50 monkeys with underlying diseases. Additionally, all monkeys with QTc above 440 ms by the new formula had some underlying disease. The results resemble those in humans, suggesting that the new QTc formula could be useful for diagnosis of QT interval prolongation in cynomolgus monkeys.

Persistence of Gut Microbiota Dysbiosis and Chronic Systemic Inflammation After Cerebral Infarction in Cynomolgus Monkeys

Background: The bidirectional interaction between the gut and brain after stroke through the immune-mediated pathway has been studied. However, the long-term effects of gut microbiota and systemic immune homeostasis after cerebral ischemia remain unclear. We examined long-term changes in the gut microbiota and systemic inflammatory cytokines after cerebral infarction in cynomolgus monkeys.

Methods: Twelve monkeys underwent successful distal M1 segment of the left middle cerebral artery occlusion (MCAO) and were randomly and equally assigned to the MCAO-1.5 m, MCAO-6 m, and MCAO-12 m groups, which were sacrificed 1.5, 6, and 12 months after cerebral infarction induction, respectively. Four monkeys that underwent a sham operation were sacrificed 12 months later. The gut microbiota and short-chain fatty acids (SCFAs) were analyzed by 16S rDNA sequencing and gas chromatography mass spectrometry, respectively. Histological examinations of the transverse colon were performed. Plasma D-lactate, zonulin, lipopolysaccharide (LPS), tumor necrosis factor (TNF-α), interferon (IFN)-γ, and interleukin (IL)-6 were detected by immunoassay kits.

Results: The levels of the Bacteroidetes phylum and Prevotella genus were significantly increased, while the Firmicutes phylum as well as the Faecalibacterium, Oscillospira, and Lactobacillus genera were decreased after cerebral infarction. Gut-originating SCFAs were significantly decreased 6 and 12 months after cerebral infarction (P < 0.05). We observed intestinal mucosal damage, evaluated by Chiu's score. Plasma D-lactate, zonulin, LPS, TNF-α, IFN-γ, and IL-6 were significantly increased after cerebral infarction (P < 0.05). Additionally, the increases in plasma LPS, TNF-α, IFN-γ, and IL-6 after cerebral infarction coincided with overgrowth of the Bacteroidetes phylum (P < 0.001).

Conclusion: Cerebral infarction induces persistent host gut microbiota dysbiosis, intestinal mucosal damage, and chronic systemic inflammation in cynomolgus monkeys.

Therapeutic effect of transplanted umbilical cord mesenchymal stem cells in a cynomolgus monkey model of multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease affecting 2.5 million young people worldwide because of its immune-mediated pathological mechanisms. Recent studies have shown that stem cell transplantation is a new potential therapy for MS. There has been renewed interest in cell therapy to improve quality of life for MS patients. In this study, the experimental autoimmune encephalomyelitis (EAE) model, which is the most commonly model to mimic MS, was successfully established in cynomolgus monkeys. To evaluate the therapeutic effect of human umbilical cord mesenchymal stem cells (UCMSCs) on MS, we intravenously transplanted UCMSCs into cynomolgus monkeys with EAE. Our results showed that UCMSC transplantation significantly ameliorated the clinical symptoms of MS. Magnetic resonance imaging and clinical signs indicated that demyelination was obviously decreased after UCMSCs therapy. Moreover, the present study showed that the mechanisms, involved in the effects of UCMSCs on MS, included their immunomodulatory functions to regulate cytokine secretion and affect functional differentiation of the T cell lineage.

The Impact of Pre-existing Immunity on the Non-clinical Pharmacodynamics of AAV5-Based Gene Therapy

Adeno-associated virus (AAV)-based vectors are widely used for gene therapy, but the effect of pre-existing antibodies resulting from exposure to wild-type AAV is unclear. In addition, other poorly defined plasma factors could inhibit AAV vector transduction where antibodies are not detected. To better define the relationship between various forms of pre-existing AAV immunity and gene transfer, we studied valoctocogene roxaparvovec (BMN 270) in cynomolgus monkeys with varying pre-dose levels of neutralizing anti-AAV antibodies and non-antibody transduction inhibitors. BMN 270 is an AAV5-based vector for treating hemophilia A that encodes human B domain-deleted factor VIII (FVIII-SQ). After infusion of BMN 270 (6.0 × 10¹³ vg/kg) into animals with pre-existing anti-AAV5 antibodies, there was a mean decrease in maximal FVIII-SQ plasma concentration (C_max) and AUC of 74.8% and 66.9%, respectively, compared with non-immune control animals, and vector genomes in the liver were reduced. In contrast, animals with only non-antibody transduction inhibitors showed FVIII-SQ plasma concentrations and liver vector copies comparable with those of controls. These results demonstrate that animals without AAV5 antibodies are likely responders to AAV5 gene therapy, regardless of other inhibiting plasma factors. The biological threshold for tolerable AAV5 antibody levels varied between individual animals and should be evaluated further in clinical studies.

Toxicologic Pathology Forum*: Opinion on Sexual Maturity and Fertility Assessment in Long-tailed Macaques ( Macaca fascicularis) in Nonclinical Safety Studies

If nonhuman primates represent the only relevant species for nonclinical safety evaluation of biotechnology-derived products, male and female fertility effects can be assessed in repeat dose toxicity studies given that sexually mature monkeys are used. This opinion piece provides recommendations for determining sexual maturity and when/how fertility assessments should be conducted in the cynomolgus monkey. Male sexual maturity should be proven by presence of sperm in a semen sample, female sexual maturity by at least two consecutive menstrual bleedings. As per regulatory guidance, default parameters for an indirect assessment of fertility in both sexes are reproductive organ weight and histopathology. Beyond default parameters, daily vaginal swabs are recommended for females, and for males, it is recommended to include blood collections (for potential analysis of reproductive hormones), testis volume sonography, and collection of frozen testis samples at necropsy. Only if there is a cause for concern, blood collection for potential reproductive hormone analysis should be conducted in females and semen analysis in males. In principle, adverse reproductive effects can be detected within 4 weeks of test article administration, depending on study design and reproductive end point chosen. Therefore, there are options for addressing reproductive toxicity aspects with studies of less than 3 months dosing duration. *This is an opinion article submitted to the Toxicologic Pathology Forum. It represents the views of the authors. It does not constitute an official position of the Society of Toxicologic Pathology, British Society of Toxicological Pathology, or European Society of Toxicologic Pathology, and the views expressed might not reflect the best practices recommended by these Societies. This article should not be construed to represent the policies, positions, or opinions of their respective organizations, employers, or regulatory agencies.

Comparison of gene expression in cynomolgus monkeys with preclinical type II diabetes induced by different high energy diets

BACKGROUND

Cynomolgus disease models that are similar to the preclinical stage of human type 2 diabetes mellitus (T2DM) were established by feeding middle-aged cynomolgus monkeys different high energy diets to study the differential expression of diabetes-related genes.

METHODS

A total of 36 male monkeys were randomly divided into four groups and fed human diets with high sugar, high fat, double high sugar and fat, and a normal diet. The preclinical diabetes phase was determined by monitoring the metabolic characteristic indices and the results of oral glucose tolerance tests (OGTT). The mRNA expression of 45 diabetes-related genes in peripheral blood leukocytes was analyzed using real-time PCR.

RESULTS

A total of 22, 25, and 21 genes were significantly up-regulated (P < 0.05) and 5, 7, and 5 genes were significantly down-regulated (P < 0.05) in the above three induced groups, respectively, compared with the control group. Of the 45 tested genes, the expression profiles of 21 genes were consistent. Most of the expression levels in the double high sugar-and-fat individuals were slightly lower than those in the high glucose and high fat groups, although the expression patterns of the three groups were essentially similar.

CONCLUSION

The different high energy diets all induced diabetes and shared some phenotypic properties with human T2DM. Most of the expression patterns of the related genes were identical. The gene expression profiles could be used as references for the study of early diagnostic indicators and T2DM pathogenesis.

Paromomycin sulfate is an effective treatment for balantidiasis in captive cynomolgus monkeys

There are few effective antimicrobial agents against Balantidium coli infection. The effect of paromomycin sulfate (PS) against B. coli was confirmed in this study of 596 captive cynomolgus monkeys. In several trials, the minimum dose and duration of oral administration of PS were 25 mg/day for 5 + 5 days, with a 2-day withdrawal interval. To facilitate daily PS administration, pumpkin cakes supplemented with PS were made, which not only resulted in precise effects but also increased the efficiency of preparation and administration of PS by the animal care staff. No cysts or trophozoites were detected at 14 or 16 days after the last treatments. There were no obvious differences in blood and biochemical parameters between before and after administration of PS. These results indicate that PS is effective for elimination of B. coli without hematological side effects. These data could contribute to the control of microbiological pathogens during veterinary care and colony management in primate facilities.

Variability of Spleen and Mesenteric Lymph Node in Control Cynomolgus Monkeys ( Macaca fascicularis) from Nonclinical Safety Studies: A Retrospective Assessment

We assessed the variability of spleen and mesenteric lymph node (MLN) microscopic observations and the correlations of these observations with other study data from 478 control cynomolgus monkeys from 53 routine nonclinical safety studies. Spleen weight parameters (absolute and relative to body or brain weights) were highly variable both within a control group on an individual study (up to 5.11-fold) and among animals with the same light microscopic observation. Grades for microscopic observations were also highly variable. The most frequent microscopic observations for spleen were changes in the size and number of germinal centers (58%), acidophilic (hyaline) material in lymphoid follicles (52%), and compound lymphoid follicles (20%). The most frequent microscopic observations in the MLN were eosinophil infiltrates (90%), changes in size and number of germinal centers (42%), and brown pigment (21%). The only meaningful relationships ( r² > 0.3) were positive correlations between reticuloendothelial hyperplasia and malarial pigment in the spleen and between each of these observations and spleen weight parameters. We conclude that determination of test article-related effects on the immune system in routine monkey toxicology studies requires careful consideration and a weight-of-evidence approach due to the low numbers of animals/group, the inherent variability in spleen and MLN parameters, and the infrequent correlation among immune system-related end points.

Choroid changes in vortex vein-occluded monkeys

AIM

To determine acute and chronic choroidal vascular changes after vortex vein occlusion in monkeys.

METHODS

One or two temporal vortex veins were occluded in 8 cynomolgus monkeys. Fluorescein angiography (FA), indocyanine green angiogram (ICGA), and enhanced-depth imaging optical coherence tomography (EDI-OCT) were performed preoperatively and at 1d, 1, 4, 8 and 12wk after occlusion. EDI-OCT images were binarized to calculate the choroid vascular index (CVI).

RESULTS

ICGA showed delayed filling of choroidal arteries in occluded quadrants in eyes with two occluded temporal vortex veins within 1wk. The thickness of the superotemporal choroid increased 1d and 4wk after occlusion, the thickness of the superonasal and inferonasal choroid increased 12wk after occlusion, and the CVI of the superonasal quadrant increased 8wk after occlusion in eyes with 2 occluded vortex veins.

CONCLUSION

Occlusion of two vortex veins leads to hemodynamic and structural changes in choroidal layers in the acute phase, while autoregulation may play the main role in the long term. Occlusion of one vortex vein has little influence on the hemodynamic and structural status of the choroid.

Spontaneous endometriosis in cynomolgus monkeys as a clinically relevant experimental model

STUDY QUESTION

Does spontaneous endometriosis in cynomolgus monkeys have the characteristics required of a good experimental model?

SUMMARY ANSWER

Spontaneous endometriosis in cynomolgus monkeys exhibited similar clinicopathological characteristics to the human disease and was useful as an experimental model.

WHAT IS KNOWN ALREADY

The prevalence of endometriosis in autopsied cynomolgus monkeys (Macaca fascicularis) in a breeding colony was reported to be 28.7% in 1993. The histopathological findings we reported recently showed that components of spontaneous endometriosis were not only endometriotic epithelium and stromal cells (CD10-positive) with hemorrhage and inflammation, but also smooth muscle metaplasia and nerve fibers.

STUDY DESIGN, SIZE, DURATION

During routine medical examinations at a research facility from 2008 to 2012, 614 female cynomolgus monkeys of reproductive age (6-25 years) were screened for endometriosis by the presence of regular menstrual bleeding, serum CA125 levels and palpation of the abdomen. In total, 29 monkeys were selected as subjects for the following study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Of the 29 monkeys selected, 15 were diagnosed with endometriosis by laparoscopy and/or open surgery. The monkeys were monitored by observing their general condition, and eight of these were monitored using laparoscopy and MRI. In addition, to investigate appropriate screening parameters and endometriosis-associated biological parameters in monkeys, we retrospectively examined general laboratory parameters that correlate to the menstrual cycle and disease status.

MAIN RESULTS AND THE ROLE OF CHANCE

The combination of CA125 serum levels (this was a useful marker for chocolate cysts), palpation of the abdomen, and fecal abnormalities was the most efficient screening method for diagnosing monkeys with endometriosis. Each animal could be diagnosed and assigned a disease stage by laparoscopy. While monitoring the disease stage by laparoscopy and/or MRI, disease status in individual monkeys was mainly stable or was progressive for 2-7 months. The detection rate by screening was low (15/614) but age-specific analysis suggests that screening would be more efficient if a colony for an endometriosis model is maintained with 11-20-year olds. As an endometriosis-associated biological parameter, the decrease in food consumption that coincided with menstruation was selected and correlated well (R2 value = 0.8239) with disease status (according to a modified adhesion revised American Fertility Society score).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Peritoneal fluid was not analyzed because a smaller amount is produced in cynomolgus monkeys than in baboons. Although clinical endometriosis-associated pain is evaluated in women using a visual analog scale, pain could not be directly evaluated in this non-human primate model.

WIDER IMPLICATIONS OF THE FINDINGS

Although cynomolgus monkeys are relatively small (2-5 kg) primates, laparoscopy and MRI make it possible to evaluate spontaneous endometriosis in these monkeys and to monitor its development over time. Spontaneous endometriosis in cynomolgus monkeys is a useful model for evaluating disease progress and drug efficacy because they have similar lesions to those in humans, and conventional laboratory methods and parameters for assessment are well established.

STUDY FUNDING/COMPETING INTEREST(S)

No external funds were used for this study. A.N.-K., K.T., H.T., A.K. and M.S. are full-time employees of Chugai Pharmaceutical Co., Ltd. R.K. received a consultancy fee from Chugai Pharmaceutical Co., Ltd. and lecture fees from Chugai Pharmaceuticals, Japan Vaccine Co. Ltd., Merck & Co., Mochida Co. Ltd., Roche Diagnostics, and BD, unrelated to the submitted work. S.N., S.O. and T.S. have nothing to declare.

Efficient Generation of Cynomolgus Monkey Induced Pluripotent Stem Cell-Derived Intestinal Organoids with Pharmacokinetic Functions

In preclinical studies, the cynomolgus monkey (CM) model is frequently used to predict the pharmacokinetics of drugs in the human small intestine, because of its evolutionary closeness to humans. Intestinal organoids that mimic the intestinal tissue have attracted attention in regenerative medicine and drug development. In this study, we generated intestinal organoids from CM induced pluripotent stem (CMiPS) cells and analyzed their pharmacokinetic functions. CMiPS cells were induced into the hindgut; then, the cells were seeded on microfabricated culture vessel plates to form spheroids. The resulting floating spheroids were differentiated into intestinal organoids in a medium containing small-molecule compounds. The mRNA expression of intestinal markers and pharmacokinetic-related genes was markedly increased in the presence of small-molecule compounds. The organoids possessed a polarized epithelium and contained various cells constituting small intestinal tissues. The intestinal organoids formed functional tight junctions and expressed drug transporter proteins. In addition, in the organoids generated, cytochrome P450 3A8 (CYP3A8) activity was inhibited by the specific inhibitor ketoconazole and was induced by rifampicin. Therefore, in the present work, we successfully generated intestinal organoids, with pharmacokinetic functions, from CMiPS cells using small-molecule compounds.

From the Cover: Evaluation of the Effects of Tanezumab, a Monoclonal Antibody Against Nerve Growth Factor, on the Sympathetic Nervous System in Adult Cynomolgus Monkeys (Macaca fascicularis): A Stereologic, Histomorphologic, and Cardiofunctional Assessment

Tanezumab, a humanized monoclonal antibody against nerve growth factor is in development for treatment of chronic pain. Three nonclinical studies assessed effects of clinically relevant and supratherapeutic doses of tanezumab on the sympathetic nervous system (SNS) of adult nonhuman primates. Study 1 evaluated potential effects of subcutaneous (SC) tanezumab (1.2 mg/kg every 8 weeks [Q8W]) on SNS in cynomolgus monkeys for 3 or 6 months and reversibility or persistence of any effects through a nondosing/recovery period. Study 2 evaluated whether neuronal cell death occurs shortly after a single SC tanezumab injection (1.2 mg/kg). Assessments for these two studies included evaluations of superior cervical and cervicothoracic ganglia for neuronal cell death and morphology. Study 3 evaluated effects of SC tanezumab (1.2 mg/kg Q8W and 30 mg/kg/week) over 6 months on sympathetic control of cardiovascular function. Tanezumab exposure was associated with stereologic changes in sympathetic ganglia, including smaller ganglion volume, and smaller average neuron size/area beginning at 2 weeks and reaching maximal levels by 1 month with no further progression through 6 months. These changes were not associated with clinical signs, completely reversed upon tanezumab withdrawal, and were not considered adverse. Tanezumab had no adverse effects on sympathetic control of cardiovascular function. These data support the conclusion that tanezumab administration for up to 6 months has no adverse effects on SNS morphology or function and does not cause neuronal cell death in adult nonhuman primates.

Strong Induction of Cytochrome P450 1A/3A, But not P450 2B, in Cultured Hepatocytes from Common Marmosets and Cynomolgus Monkeys by Typical Human P450 Inducing Agents

BACKGROUND

Common marmosets (Callithrix jacchus) and cynomolgus monkeys (Macaca fascicularis) are used as non-human primate models in preclinical studies for drug development.

OBJECTIVE

The assessment of P450 induction in hepatocytes from marmosets and cynomolgus monkeys was performed using typical P450 inducers.

METHODS

Induction of cytochrome P450 1-4 family enzymes was analyzed in two lots of cultured hepatocytes from common marmosets and cynomolgus monkeys after 24-h treatment with typical human P450 inducing agents by real-time reverse transcription-polymerase chain reaction.

RESULTS

Marmoset P450 3A4 mRNA and P450 2C8/2C19 mRNA in hepatocytes were strongly (>10- fold) and weakly (>2) induced by rifampicin, respectively. Marmoset 1A1 and 1A2 mRNA were induced strongly (>200-fold) by β-naphthoflavone and omeprazole. Marmoset P450 2B6 mRNA was induced (~5-fold) by a constitutive androstane receptor agonist, but not by phenobarbital. Cynomolgus monkey P450 3A4 mRNA and P450 1A1 mRNA in cultured hepatocytes were also induced by rifampicin and omeprazole, respectively, but P450 2B6 mRNA was not induced by phenobarbital.

CONCLUSION

These results indicate that P450 1A/3A induction by typical human P450 inducers in hepatocytes from marmosets and/or cynomolgus monkeys are similar to those of humans (except for P450 2B induction by phenobarbital in humans), suggesting that marmosets and cynomolgus monkeys might be suitable models for evaluating the drug interactions in preclinical studies.

Persistence of vertebral growth plate cartilage in aged cynomolgus monkeys

Growth plates at each end of vertebral bodies play a pivotal role in longitudinal spinal growth. Epiphyseal closures are formed in adult humans. Although monkeys are frequently employed in bone and disc research, the age of epiphyseal closure has not been well documented. In this study, histological analyses of lumbar vertebral end plates and the surrounding tissue were performed in 11 normal cynomolgus monkeys aged approximately 9 to 15 years, and unclosed growth plate cartilage was detected in all the end plates. The data from this study constitute the first documentation of persistent vertebral growth plate cartilage in cynomolgus monkeys. The persistence of growth plate cartilage in cynomolgus monkeys approximately 15 years of age or younger, which differs from the complete epiphyseal closure exhibited in adult humans, may affect the biomechanical behavior of the spine. This is an important factor to consider in extrapolating the results of spine and intervertebral disc research using cynomolgus monkeys to adult humans.

Histopathologic Characterization of Mifepristone-induced Ovarian Toxicity in Cynomolgus Monkeys

Mifepristone, which is an orally active synthetic steroid with antiprogesterone activity, is known as an ovarian toxicant. Because the available data regarding the histopathologic characteristics of ovarian toxicity in nonhuman primates are limited, the present study was undertaken in order to investigate detailed histopathologic changes accompanying mifepristone-induced ovarian toxicity and its relationship to changes in menstrual cycle and circulating sex steroid hormone. Twenty mg/kg of mifepristone was orally administered daily to 4 cynomolgus monkeys for 2 months. Mifepristone inhibited the cyclic increases in circulating estradiol-17β and progesterone levels with associated absence of menstruation. Histopathologically, the ovary in the treated animals showed follicular phase without changes in the percentage of atretic antral follicles, and reduced endometrial thickness was noted in the uterus. These changes indicated that a certain degree of antral follicle development had been retained in spite of the menstrual cycle having been arrested in mifepristone-treated animals. Our investigation suggested that it is important to perform detailed histopathologic examination of reproductive organs with precise knowledge of the characteristics of each menstrual stage to detect ovarian toxicity in nonhuman primates. Monitoring menstrual signs and circulating sex steroid hormone levels provides additional evidence for the investigation of the mechanism of ovarian toxicity.

Characterization of a PRISTANE-induced lupus-associated model in the non-human primate cynomolgus monkey

BACKGROUND

Lupus is an autoimmune disease with complex syndrome. Rodent models have limitations for recapitulating the spectrum of the disease. A more powerful translational model is desirable.

METHOD

Lupus-associated model in cynomolgus monkeys was induced by two intraperitoneal injections of 2, 6, 10, 14-tetramethylpentadecane (PRISTANE). Lupus-specific biomarkers and manifestations over a 246-day period were observed at multilevel. To visualize and quantify kidney function in real time, contrast-enhanced ultrasound was used.

RESULTS

The indicative biomarkers and manifestations fulfilled major diagnosis criteria according to the "Criteria of Lupus" of the American College of Rheumatology. Significant changes in time-intensity curve parameters were observed, indicating impaired renal function and the method as a feasible, non-invasive diagnostic method in primate model.

CONCLUSIONS

We successfully induced lupus-associated model with systemic lupus syndrome. This primate model can be a valuable translational model for further pathogenesis and symptomology studies and for exploring therapeutic candidates.

Morphological evaluation of retinal ganglion cells expressing the L132C/T159C ChR2 mutant transgene in young adult cynomolgus monkeys

To characterize recombinant AAV2 (rAAV2)-mediated expression of L132C/T159C ChR2 mutant in retinal ganglion cells (RGCs) of young adult cynomolgus monkeys. rAAV2 vectors carrying a fusion construct of the ChR2 mutant and GFP (ChR2-GFP) were delivered to the vitreous chamber by intravitreal injection. Expression patterns of the ChR2 mutant in RGCs were examined by immunohistochemical methods three months after injection. The RNA-binding protein with multiple splicing (RBPMS) was used as an RGC specific marker to differentiate RGCs from other retinal neurons and non-neuronal cells. The numbers of RBPMS+ and GFP+ double-labeled RGCs in the central foveal varied with the eccentricity. The expression peaked within 100 μm from the edge of the foveola and drastically decreased to a single superficial RGC layer approximately 300 μm from the edge. On average, the ratio of the double-labeled RGCs versus RBPMS+ RGCs approached 0.32±0.15 (n=14 fields) at the central foveal region (0.1 to 0.53 mm). We observed that the ratio reached 0.78±0.16 (n=21 fields) at peripheral retinal locations (eccentricity >7 mm). This investigation demonstrates that RBPMS could serve as a valuable RGC specific marker for future investigations in this field.

Distribution of FcRn Across Species and Tissues

The neonatal Fc receptor (FcRn) is a major histocompatibility complex class I type molecule that binds to, transports, and recycles immunoglobulin G (IgG) and albumin, thereby protecting them from lysosomal degradation. Therefore, besides the knowledge of FcRn affinity, FcRn protein expression is critical in understanding the pharmacokinetic behavior of Fc-containing biotherapeutics such as monoclonal antibodies. The goal of this investigation was to achieve for the first time a comparative assessment of FcRn distribution across a variety of tissues and species. FcRn was mapped in about 20 tissues including placenta from human and the most frequently used species in non-clinical safety testing of monoclonal antibodies (mouse, rat, cynomolgus monkey). In addition, the FcRn expression pattern was characterized in two humanized transgenic mouse lines (Tg32 and Tg276) expressing human FcRn under different promoters, and in the severe combined immunodeficient (SCID) mouse. Consecutive sections were stained with specific markers, namely, anti-CD68 for macrophages and anti-von Willebrand Factor for endothelial cells. Overall, the FcRn expression pattern was comparable across species and tissues with consistent expression of FcRn in endothelial cells and interstitial macrophages, Kupffer cells, alveolar macrophages, enterocytes, and choroid plexus epithelium. The human FcRn transgenic mouse Tg276 showed a different and much more widespread staining pattern of FcRn. In addition, immunodeficiency and lack of IgG in SCID mice had no negative effect on FcRn expression compared with wild-type mice.

Establishment of reference values for complete blood count and blood gases in cynomolgus monkeys (Macaca fascicularis)

Cynomolgus monkeys are closely related to humans phylogenetically, and this has resulted in their widespread use as a preclinical model. Hematological data with regard to these monkeys are thus important. Although reference values for blood components and sex hormones have been established for cynomolgus monkeys, those for arterial blood gases have not. The arterial blood gases quickly reflect respiratory and circulatory dynamics, and are thus useful for animal management and safe general anesthesia and surgical operations. Furthermore, since O₂ is transported by RBC, CBC and blood gases are closely related. The present study aimed to establish reference values for arterial blood gases and CBC in cynomolgus monkeys over a wide age range. Blood gases and CBC of arterial blood, collected from 41 female and 21 male anesthetized monkeys, were measured. Age correlated with RBC, HGB and HCT in the CBC. Values differed significantly between males and females in pCO₂, CO₂ concentration, MCV and MCH. The pH of blood was equivalent to that of humans and pCO₂ was more stable, whereas MCV and MCH were lower than those in humans. Erythrocytes were smaller and less pigmented than in other Macaca species. Several relationships between gender and age, and blood gases and CBC were identified in cynomolgus monkeys. In conclusion, these reference values will be useful as markers for veterinary applications and in the care and maintenance of these animals.

Characterization of the Molecular Mechanisms Underlying the Chronic Phase of Stroke in a Cynomolgus Monkey Model of Induced Cerebral Ischemia

Stroke is one of the main causes of mortality and long-term disability worldwide. The pathophysiological mechanisms underlying this disease are not well understood, particularly in the chronic phase after the initial ischemic episode. In this study, a Macaca fascicularis stroke model consisting of two sample groups, as determined by MRI-quantified infarct volumes as a measure of the stroke severity 28 days after the ischemic episode, was evaluated using qualitative and quantitative proteomics analyses. By using multiple online multidimensional liquid chromatography platforms, 8790 nonredundant proteins were identified that condensed to 5223 protein groups at 1% global false discovery rate (FDR). After the application of a conservative criterion (5% local FDR), 4906 protein groups were identified from the analysis of cerebral cortex. Of the 2068 quantified proteins, differential proteomic analyses revealed that 31 and 23 were dysregulated in the elevated- and low-infarct-volume groups, respectively. Neurogenesis, synaptogenesis, and inflammation featured prominently as the cellular processes associated with these dysregulated proteins. Protein interaction network analysis revealed that the dysregulated proteins for inflammation and neurogenesis were highly connected, suggesting potential cross-talk between these processes in modulating the cytoskeletal structure and dynamics in the chronic phase poststroke. Elucidating the long-term consequences of brain tissue injuries from a cellular prospective, as well as the molecular mechanisms that are involved, would provide a basis for the development of new potentially neurorestorative therapies.

Investigation of sleep-wake rhythm in non-human primates without restraint during data collection

To understand sleep mechanisms and develop treatments for sleep disorders, investigations using animal models are essential. The sleep architecture of rodents differs from that of diurnal mammals including humans and non-human primates. Sleep studies have been conducted in non-human primates; however, these sleep assessments were performed on animals placed in a restraint chair connected via the umbilical area to the recording apparatus. To avoid restraints, cables, and other stressful apparatuses and manipulations, telemetry systems have been developed. In the present study, sleep recordings in unrestrained cynomolgus monkeys (Macaca fascicularis) and common marmoset monkeys (Callithrix jacchus) were conducted to characterize normal sleep. For the analysis of sleep-wake rhythms in cynomolgus monkeys, telemetry electroencephalography (EEG), electromyography (EMG), and electrooculography (EOG) signals were used. For the analysis of sleep-wake rhythms in marmosets, telemetry EEG and EOG signals were used. Both monkey species showed monophasic sleep patterns during the dark phase. Although non-rapid eye movement (NREM) deep sleep showed higher levels at the beginning of the dark phase in cynomolgus monkeys, NREM deep sleep rarely occurred during the dark phase in marmosets. Our results indicate that the use of telemetry in non-human primate models is useful for sleep studies, and that the different NREM deep sleep activities between cynomolgus monkeys and common marmoset monkeys are useful to examine sleep functions.

Pattern of novel object exploration in cynomolgus monkey Macaca fascicularis

BACKGROUND

Primates exhibit substantial capacity for behavioral innovation, expanding the diversity of their behavioral repertoires, and benefiting both individual survival and species development in evolution. Novel object exploration is an integral part of behavioral innovation. Thus, qualitative and quantitative analysis of novel object exploration helps to better understand behavioral innovation.

METHODS

To study the pattern of novel object exploration, two different sized balls were sequentially introduced to singly caged cynomolgus monkeys. Two aspects of monkeys' behaviors were analyzed: the types of motor activities in toy playing and whether there is an orderly sequence of such motor activities during novelty exploration.

RESULTS

Four types of behavioral activities (oral contact, gross and fine forelimb motor, and hind limb motor) followed a pattern: first forelimb gross motor and oral contact, followed by forelimb fine motor and hind limb activities. Oral contact appeared to be an important behavior in monkeys' repertoire of novelty exploratory behaviors, both as an early appearing activity, and showing a consistent pattern of high cumulative time for two different novel objects.

CONCLUSIONS

These results provide a profile of novel object exploratory behaviors in cynomolgus monkeys, contributing to a better understanding of this aspect of behavioral innovation.

Adaptations in Basal and Hypothalamic-Pituitary-Adrenal-Activated Deoxycorticosterone Responses Following Ethanol Self-administration in Cynomolgus Monkeys

Acute ethanol activates the hypothalamic-pituitary-adrenal (HPA) axis, while long-term exposure results in a blunted neuroendocrine state, particularly with regards to the primary endpoint, cortisol, the primary glucocorticoid produced in the adrenal cortex. However, it is unknown if this dampened neuroendocrine status also influences other adrenocortical steroids. Plasma concentration of the mineralocorticoid and neuroactive steroid precursor deoxycorticosterone (DOC) is altered by pharmacological challenges of the HPA axis in cynomolgus monkeys. The present study investigated HPA axis regulation of circulating DOC concentration over the course of ethanol (4% w/v) induction and self-administration in non-human primates (Macaca fasciculata, n = 10). Plasma DOC, measured by radioimmunoassay, was compared at baseline (ethanol naïve), during schedule-induced polydipsia, and following 6-months of 22 h/day access to ethanol and water. The schedule induction of ethanol drinking did not alter basal DOC levels but selectively dampened the DOC response to pharmacological challenges aimed at the anterior pituitary (ovine corticotrophin-releasing hormone) and adrenal gland (post-dexamethasone adrenocorticotropin hormone), while pharmacological inhibition of central opioid receptors with naloxone greatly enhanced the DOC response during induction. Following 6 months of ethanol self-administration, basal DOC levels were increased more than twofold, while responses to each of the challenges normalized somewhat but remained significantly different than baseline. These data show that HPA axis modulation of the neuroactive steroid precursor DOC is markedly altered by the schedule induction of ethanol drinking and long-term voluntary ethanol self-administration. The consequences of chronic ethanol consumption on HPA axis regulation of DOC point toward allostatic modification of hypothalamic and adrenal function.

Translational Safety Genetics

The emerging field of translational safety genetics is providing new opportunities to enhance drug discovery and development. Genetic variation in therapeutic drug targets, off-target interactors and relevant drug metabolism/disposition pathways can contribute to diverse drug pharmacologic and toxicologic responses between different animal species, strains and geographic origins. Recent advances in the sequencing of rodent, canine, nonhuman primate, and minipig genomes have dramatically improved the ability to select the most appropriate animal species for preclinical drug toxicity studies based on genotypic characterization of drug targets/pathways and drug metabolism and/or disposition, thus avoiding inconclusive or misleading animal studies, consistent with the principles of the 3Rs (replacement, reduction and refinement). The genetic background of individual animals should also be taken into consideration when interpreting phenotypic outcomes from toxicity studies and susceptibilities to spontaneous safety-relevant background findings.

Identification of MHC Haplotypes Associated with Drug-induced Hypersensitivity Reactions in Cynomolgus Monkeys

Drug-induced hypersensitivity reactions can significantly impact drug development and use. Studies to understand risk factors for drug-induced hypersensitivity reactions have identified genetic association with specific human leukocyte antigen (HLA) alleles. Interestingly, drug-induced hypersensitivity reactions can occur in nonhuman primates; however, association between drug-induced hypersensitivity reactions and major histocompatibility complex (MHC) alleles has not been described. In this study, tissue samples were collected from 62 cynomolgus monkeys from preclinical studies in which 9 animals had evidence of drug-induced hypersensitivity reactions. Microsatellite analysis was used to determine MHC haplotypes for each animal. A total of 7 haplotypes and recombinant MHC haplotypes were observed, with distribution frequency comparable to known MHC I allele frequency in cynomolgus monkeys. Genetic association analysis identified alleles from the M3 haplotype of the MHC I B region (B*011:01, B*075:01, B*079:01, B*070:02, B*098:05, and B*165:01) to be significantly associated (χ² test for trend, p < 0.05) with occurrence of drug-induced hypersensitivity reactions. Sequence similarity from alignment of alleles in the M3 haplotype B region and HLA alleles associated with drug-induced hypersensitivity reactions in humans was 86% to 93%. These data demonstrate that MHC alleles in cynomolgus monkeys are associated with drug-induced hypersensitivity reactions, similar to HLA alleles in humans.

Characteristics of histologically confirmed endometriosis in cynomolgus monkeys

STUDY QUESTION

What are the characteristics of spontaneous endometriosis in cynomolgus monkeys?

SUMMARY ANSWER

Spontaneous endometriosis in cynomolgus monkeys exhibited similar characteristics to the human disease.

WHAT IS KNOWN ALREADY

One previous report described the prevalence and the basic histopathology of spontaneous endometriosis in cynomolgus monkeys.

STUDY DESIGN, SIZE, DURATION

Endometriotic lesions that had been histologically confirmed in 8 female cynomolgus monkeys between 5 and 21 years old were subjected to study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The monkeys died of, or were sacrificed because of, sickness consequent on endometriosis. Specimens were evaluated histopathologically with haematoxylin and eosin staining, iron staining and immunohistochemistry (CD10, CD31, α-SMA and PGP9.5), and by observing them under a microscope.

MAIN RESULTS AND THE ROLE OF CHANCE

Endometriotic and stromal cells (CD10-positive) with haemorrhage and inflammation were observed. Smooth muscle metaplasia and nerve fibres were also noted in the endometriotic lesions. Endometriotic lesions in lymph nodes were incidentally found.

LIMITATIONS AND REASONS FOR CAUTION

Since laparoscopic analysis for monitoring the disease state was not set as a parameter of the current study, time course changes (progression) of the disease were not assessed.

WIDER IMPLICATIONS OF THE FINDINGS

Further investigation of spontaneous endometriosis in cynomolgus monkeys may contribute to better understanding of the disease pathobiology.

STUDY FUNDING/COMPETING INTEREST(S)

No external funds were used for this study. A.N.K., S.M., S.H., T.I., O.K., A.K. and M.S. are full-time employees of Chugai Pharmaceutical Co., Ltd. R.K. received lecture fees from Chugai Pharmaceutical Co., Ltd., unrelated to the submitted work. S.N., S. O., L.Y., K.Y. and T.S. have nothing to declare.

TRIAL REGISTRATION NUMBER

N/A.

Neuroblastoma at the trigeminal nerve in a cynomolgus monkey (Macaca fascicularis)

A male cynomolgus monkey (Macaca fascicularis) of 5 years and 11 months of age from the vehicle control group of a 4-week repeated oral dose toxicity study had a spontaneously occurring mass lesion directly attached to the proximal part of the left trigeminal nerve. Histologically, the mass was characterized by a multifocal nodular appearance. Nodular zones showed low to moderate cellularity and were composed of small round cells exhibiting nuclear uniformity. On the other hand, inter-nodular zones were composed of nerve fiber containing septa and closely aggregated highly pleomorphic cells. Immunohistochemically, the small round cells were strongly immunopositive for synaptophysin, neuN, and class III beta-tubulin, while the highly pleomorphic cells were weakly immunopositive for neuN and occasionally immunopositive for class III beta-tubulin and doublecortin, suggesting that the tumor had originated from a neuronal lineage cell. Based on these findings, the mass was diagnosed as a neuroblastoma at the trigeminal nerve.

Accumulation of brown pigment-laden macrophages associated with vascular lesions in the lungs of cynomolgus monkeys(Macaca fascicularis)

Accumulation of macrophages containing brown pigments in the lungs is a well-known spontaneous lesion found in cynomolgus monkey. However, its pathogenesis has not been clearly described. In our survey, brown pigment-laden macrophages were found in the lungs of 4 out of 43 cases. Brown pigments were mostly found in the macrophages of the perivascular interstitium, which proved to be hemosiderin. Some small- to medium-sized vessels that exhibited prominent accumulation of brown pigment-laden macrophages showed degeneration and necrosis of the smooth muscle cells of tunica media. Furthermore, ruptures of the internal and external elastic laminae were seen in some of the vessels. These findings suggested that partial fragmentation of the vascular elastic lamina followed by degeneration and necrosis of the tunica media caused blood leakage leading to the accumulation of hemosiderin-laden macrophages in the perivascular interstitium of the lungs.

Maturity-related Variability of the Thymus in Cynomolgus Monkeys (Macaca fascicularis)

Terminal body weights (TBWs), thymus weight parameters, and thymus morphology were retrospectively evaluated in 453 cynomolgus monkeys assigned to control groups on nonclinical toxicity studies. Morphology of bone, ovary, and testis/epididymis were used to determine maturity status of individual animals. There was no correlation between TBW and thymus weight (absolute and/or relative to TBW or brain weight). Thymus weight parameters and grades of decreased lymphocytes in the thymus were highly variable in immature animals compared to mature animals. There was also high (up to 11-fold) variability of thymus weight parameters within a given control group on the same study (generally 3 or 4 animals per sex). Several parameters evaluated had more pronounced age-related changes in males when compared to females. Our results demonstrate the inherent variability of thymus weight parameters and morphologic observations for cynomolgus monkeys on toxicology studies. Changes in thymus parameters in cynomolgus monkeys are unreliable indicators of immunomodulation or immunotoxicity in the absence of other relevant findings. Therefore, the thymus parameters commonly evaluated in preclinical safety assessments should not be the primary data set used to determine the presence of a direct test article-related effect on the immune system.

Immunohistochemical localization of the calcitonin gene-related peptide binding site in the primate trigeminovascular system using functional antagonist antibodies

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and a neuromodulator implicated in the pathophysiology of migraine. It binds to the extracellular domains of calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein (RAMP) 1 that together form the CGRP receptor. Antagonist antibodies against CGRP and its binding site at the receptor are clinically effective in preventing migraine attacks. The blood-brain barrier penetration of these antagonist antibodies is limited, suggesting that a potential peripheral site of action is sufficient to prevent migraine attacks. To further understand the sites of CGRP-mediated signaling in migraine, we used immunohistochemical staining with recently developed antagonist antibodies specifically recognizing a fusion protein of the extracellular domains of RAMP1 and CLR that comprise the CGRP binding pocket at the CGRP receptor in monkey and man. We confirmed binding of the antagonist antibodies to human vascular smooth muscle cells (VSMCs) of dural meningeal arteries and neurons in the trigeminal ganglion, both of which are likely sites of action for therapeutic antibodies in migraine patients. We further used one of these antibodies for detailed mapping on cynomolgus monkey tissue and found antagonist antibody binding sites at multiple levels in the trigeminovascular system: in the dura mater VSMCs, in neurons and satellite glial cells in the trigeminal ganglion, and in neurons in the spinal trigeminal nucleus caudalis. These data reinforce and clarify our understanding of CGRP receptor localization in a pattern consistent with a role for CGRP receptors in trigeminal sensitization and migraine pathology.

MicroRNA profiles in a monkey testicular injury model induced by testicular hyperthermia

To characterize microRNAs (miRNAs) involved in testicular toxicity in cynomolgus monkeys, miRNA profiles were investigated using next‐generation sequencing (NGS), microarray and reverse transcription‐quantitative real‐time‐PCR (RT‐qPCR) methods. First, to identify organ‐specific miRNAs, we compared the expression levels of miRNAs in the testes to those in representative organs (liver, heart, kidney, lung, spleen and small intestine) obtained from naïve mature male and female monkeys (n = 2/sex) using NGS analysis. Consequently, miR‐34c‐5p, miR‐202‐5p, miR‐449a and miR‐508‐3p were identified to be testicular‐specific miRNAs in cynomolgus monkeys. Next, we investigated miRNA profiles after testicular–hyperthermia (TH) treatment to determine which miRNAs are involved in testicular injury. In this experiment, mature male monkeys were divided into groups with or without TH‐treatment (n = 3/group) by immersion of the testes in a water bath at 43 °C for 30 min for 5 consecutive days. As a result, TH treatment induced testicular injury in all animals, which was characterized by decreased numbers of spermatocytes and spermatids. In a microarray analysis of the testis, 11 up‐regulated (>2.0 fold) and 13 down‐regulated (<0.5 fold) miRNAs were detected compared with those in the control animals. Interestingly, down‐regulated miRNAs included two testicular‐specific miRNAs, miR‐34c‐5p and miR‐449a, indicating their potential use as biomarkers for testicular toxicity. Furthermore, RT‐qPCR analysis revealed decreased expression levels of testicular miR‐34b‐5p and miR‐34c‐5p, which are enriched in meiotic cells, reflecting the decrease in pachytene spermatocytes and spermatids after TH treatment. These results provide valuable insights into the mechanism of testicular toxicity and potential translational biomarkers for testicular toxicity. Copyright © 2016 The Authors. Journal of Applied Toxicology published by John Wiley & Sons Ltd.

In this study, we identified 4 testicular‐specific miRNAs, miR‐34c‐5p, miR‐202‐5p, miR‐449a, and miR‐508‐3p based on next‐generation sequencing of miRNAs from representative organs obtained from naïve mature cynomolgus monkeys. Next, miRNAs were profiled in a model of testicular injury induced by testicular hyperthermia. Microarray and PCR analyses revealed down‐regulation of miR‐34c‐5p in the testis, which is enriched in meiotic cells, reflecting decreased numbers of pachytene spermatocytes and spermatids by the treatment.

Malaria in cynomolgus monkeys used in toxicity studies in Japan

Plasmodium spp. protozoa cause malaria and are known to infect humans and a variety of animal species including macaque monkeys. Here we report both our experience with malaria recrudescence in cynomolgus monkeys (Macaca fascicularis) in a toxicity study and the results of a survey on Plasmodium infection in cynomolgus monkeys imported to Japan for laboratory use. A cynomolgus monkey from the toxicity study presented with severe anemia and Plasmodium protozoa in erythrocytes on a thin blood smear and was subsequently diagnosed with symptomatic malaria. In this animal, congestion and accumulation of hemozoin (malaria pigment) in macrophages were noted in the enlarged and darkly discolored spleen. As a follow-up for the experience, spleen sections from 800 cynomolgus monkeys in toxicity studies conducted between 2003 and 2013 were retrospectively examined for hemozoin deposition as a marker of Plasmodium infection. The origin of the animals included Cambodia, China, Indonesia, and Vietnam. Hemozoin deposition was confirmed in 44% of all examined monkeys. Monkeys from Indonesia showed the highest incidence of hemozoin deposition (approx. 80%). A high prevalence of Plasmodium infection in laboratory monkeys was also confirmed with polymerase chain reaction (PCR) by using Plasmodium genus-specific primers. Although Japan is not a country with endemic malaria, it is important to be aware of the prevalence and potential impact of background infection with Plasmodium spp. and recrudescence of symptomatic malaria in imported laboratory monkeys on pharmaceutical toxicity studies.

Normal Anatomy, Histology, and Spontaneous Pathology of the Nasal Cavity of the Cynomolgus Monkey (Macaca fascicularis)

The evaluation of inhalation studies in monkeys is often hampered by the scarcity of published information on the relevant nasal anatomy and pathology. We examined nasal cavities of 114 control cynomolgus monkeys from 11 inhalation studies evaluated 2008 to 2013, in order to characterize and document the anatomic features and spontaneous pathology. Compared to other laboratory animals, the cynomolgus monkey has a relatively simple nose with 2 unbranched, dorsoventrally stacked turbinates, large maxillary sinuses, and a nasal septum that continues into the nasopharynx. The vomeronasal organ is absent, but nasopalatine ducts are present. Microscopically, the nasal epithelium is thicker than that in rodents, and the respiratory (RE) and transitional epithelium (TE) rest on a thick basal lamina. Generally, squamous epithelia and TE line the vestibule, RE, the main chamber and nasopharynx, olfactory epithelium, a small caudodorsal region, while TE is observed intermittently along the passages. Relatively high incidences of spontaneous pathology findings, some resembling induced lesions, were observed and included inflammation, luminal exudate, scabs, squamous and respiratory metaplasia or hyperplasia, mucous cell hyperplasia/metaplasia, and olfactory degeneration. Regions of epithelial transition were the most affected. This information is considered helpful in the histopathology evaluation and interpretation of inhalation studies in monkeys.

Autologous iPSC-derived dopamine neuron transplantation in a nonhuman primate Parkinson's disease model

Autologous dopamine (DA) neurons are a new cell source for replacement therapy of Parkinson's disease (PD). In this study, we tested the safety and efficacy of autologous induced pluripotent stem cell (iPSC)-derived DA cells for treatment of a cynomolgus monkey PD model. Monkey bone marrow mesenchymal cells were isolated and induced to iPSCs, followed by differentiation into DA cells using a method with high efficiency. Autologous DA cells were introduced into the brain of a cynomolgus monkey PD model without immunosuppression; three PD monkeys that had received no grafts served as controls. The PD monkey that had received autologous grafts experienced behavioral improvement compared with that of controls. Histological analysis revealed no overgrowth of grafts and a significant number of surviving A9 region-specific graft-derived DA neurons. The study provided a proof-of-principle to employ iPSC-derived autologous DA cells for PD treatment using a nonhuman primate PD model.

Morphologic manifestations of testicular and epididymal toxicity

Histopathologic examination of the testis is the most sensitive means to detect effects on spermatogenesis; however, the complexity of testicular histology, interrelatedness of cell types within the testis, and long duration of spermatogenesis can make assessment of a testicular toxicant challenging. A thorough understanding of the histology and morphologic manifestations of response to injury is critical to successfully identify a testicular effect and to begin to understand the underlying mechanism of action. The basic patterns of response to xenobiotic-induced injury to the testis and epididymis are detailed and discussed.

Utility of finger maze test for learning and memory abilities in infants of cynomolgus monkeys exposed to thiamazole

A new type of learning and memory test using a finger maze was conducted in infant cynomolgus monkeys that were exposed to thiamazole (2 and 3.5 mg/kg per day to pregnant animals orally) during the fetal period (gestational days 120 to 150). We modified Tsuchida's original finger maze test method by reducing the number of trials per day and simplifying the criteria for achievement of training, and we added a long-term memory test. In the memory test, thiamazole-exposed infants required greater time to complete the finger maze test than the control infants although no effect was noted in the training or learning test. The results suggest that an impaired long-term memory could be detected by our modified finger maze test.

Comparative nonclinical assessments of the proposed biosimilar PF-05280586 and rituximab (MabThera®)

Comparative nonclinical studies were conducted with the proposed biosimilar PF-05280586 and rituximab-EU (MabThera®). In side-by-side analyses, peptide maps and complement-dependent cytotoxicity assay results were similar. Sexually-mature cynomolgus monkeys were administered PF-05280586 or rituximab-EU as a single dose of 0, 2, 10, or 20 mg/kg on day 1 and observed for 92 days (single-dose study) or as 5 weekly injections of 0 or 20 mg/kg and necropsied on day 30, the day after the 5th dose, or on day 121 (repeat-dose study). The pharmacokinetic and pharmacodynamic profiles for both molecules were similar. Marked depletion of peripheral blood B cells 4 days after dosing was followed by near or complete repletion (single-dose study) or partial repletion (repeat-dose study). In the single-dose study, anti-drug antibodies (ADA) were detected by day 29 in all animals administered PF-05280586 or rituximab-EU and persisted through day 85, the last day tested. In the repeat-dose study, ADA were detected on day 121 in 50% of animals administered PF-05280586 or rituximab-EU. Both molecules were well tolerated at all doses. In all endpoints evaluated, PF-05280586 exhibited similarity to rituximab-EU.

New method for sperm evaluation by 3-dimensional laser scanning microscopy in different laboratory animal species

Sperm analysis is one of the end points in reproductive toxicology studies. Different methods for quantitative sperm analysis have been described. For qualitative morphological sperm analysis, either such techniques or smears of sperm and histological sperm staging are in use. Any of these methods provides morphological results on a light microscopy level. Laser scanning microscopy is a technique using a focused laser for scanning an object. The Olympus 3D Laser Scanning Microscope LEXT OLS4000 with optional possibilities of differential interference contrast provides a microscopic method for visualizing microasperities, which are far beyond the resolving power of a typical light or laser microscope. This technique was applied to sperm of mice, rats, rabbits, and cynomolgus monkeys at magnifications up to ×17 090. The obtained images are comparable to those of a scanning electron microscope under relatively low-power magnifications. Measurements on sperm parameters were taken by an integrated image analysis software tool. Abnormalities were easily detectable.

Inhibition of CRAC with a human anti-ORAI1 monoclonal antibody inhibits T-cell-derived cytokine production but fails to inhibit a T-cell-dependent antibody response in the cynomolgus monkey

ORAI1 is the pore-forming component of calcium release-activated calcium (CRAC) channels. CRAC channels are the primary route for calcium ion (Ca(2+)) entry into T-cells following antigen stimulation. This Ca(2+) entry induces proliferation and cytokine production through activation of calcineurin and the nuclear factor of activated T-cells (NFAT) transcription factor along with subsequent cytokine-related genes. It was hypothesized that the in vivo inhibition of T-cell function by blocking ORAI1 or calcineurin would lead to similar functional consequences. To test this hypothesis the activity of 2C1.1, a fully human anti-ORAI1 monoclonal antibody, and cyclosporin A (CsA) were tested in vivo for their suppressive effect on T-cell-derived cytokine production and a T-cell-dependent antibody response (TDAR) using sheep red blood cells (SRBC) in cynomolgus monkeys. Despite showing similar inhibition of ex vivo interleukin (IL)-2 production by stimulated T-cells, both molecules exhibited different pharmacologic effects on the SRBC antibody response. CsA blocked the development of SRBC-specific antibodies, while 2C1.1 failed to inhibit the antigen-specific antibody response. These surprising observations suggest that full inhibition of the CRAC channel is required to inhibit a functional immune response, consistent with findings from human patients with loss of function mutations in ORAI1.

Effect of living conditions on biochemical and hematological parameters of the cynomolgus monkey

The cynomolgus monkey (Macaca fascicularis) has been increasingly used in biomedical research. Although living conditions affect behavioral and physiological characteristics in macaques, little data is available on how living conditions influence blood-based parameters in the cynomolgus monkey. We hypothesize that there are significant differences in serum biochemical and hematological parameters in single-caged versus socially housed cynomolgus monkeys, and that age and sex influence the effect of living conditions on these parameters. Sixty single-caged and 60 socially housed cynomolgus monkeys were segregated by age group (juvenile, adult) and sex. The effects of living condition, age, sex, and the interactions between these factors on commonly reported serum biochemical and hematological parameters were analyzed by a three-way analysis of variance (ANOVA). Then, the differences between single-caged and socially housed subjects were tested in each parameter by Student's t-test. Creatinine, glucose, triglyceride, alanine aminotransferase, red blood cell volume distribution width (SD, CV), median fluorescence reticulocyte percentage, white blood cell and basophil counts, and monocyte (count, %) were lower in single-caged subjects. Blood urea nitrogen and globulin were lower in single-caged juveniles and adults, respectively. Red blood cell count, hemoglobin, hematocrit, and neutrophil (count, %) were higher, and reticulocyte and lymphocyte (counts, %) were lower, in single-caged juveniles. Mean corpuscular hemoglobin concentration was higher in single-caged subjects (but more pronounced in adults). Total protein was higher in single-caged juvenile males and lower in single-caged adult females. Alkaline phosphatase was lower in single-caged juvenile females. Mean corpuscular hemoglobin was higher, and high fluorescence reticulocyte percentage was lower, in single-caged adult males. In conclusion, living conditions significantly affect several serum biochemical and hematological parameters in the cynomolgus monkey, and these effects vary by age and sex. As this macaque is commonly housed under different living conditions, these findings should aid researchers in avoiding inaccurate conclusions concerning this species.