Knee osteoarthritis pain following medial meniscectomy in the nonhuman primate

Evaluation of brain activation related to resting pain using functional magnetic resonance imaging in cynomolgus macaques undergoing knee surgery

Purpose

Functional magnetic resonance imaging (fMRI) visualizes hemodynamic responses associated with brain and spinal cord activation. Various types of pain have been objectively assessed using fMRI as considerable brain activations. This study aimed to develop a pain model in cynomolgus macaques undergoing knee surgery and confirm brain activation due to resting pain after knee surgery.

Methods

An osteochondral graft surgery on the femoral condyle in the unilateral knee was performed on four cynomolgus macaques (Macaca fascicularis). Resting pain was evaluated as changes in brain fMRI findings with a 3.0-T MRI scanner preoperatively, postoperatively, and after postoperative administration of morphine. In the fMRI analysis, Z-values >1.96 were considered statistically significant.

Results

Brain activation without stimulation after surgery in the cingulate cortex (3.09) and insular cortex (3.06) on the opposite side of the surgery was significantly greater than that before surgery (1.05 and 1.03, respectively) according to fMRI. After the administration of morphine, activation due to resting pain decreased in the cingulate cortex (1.38) and insular cortex (1.21).

Conclusion

Osteochondral graft surgery on the femoral condyle can lead to postoperative resting pain. fMRI can reveal activation in pain-related brain areas and evaluate resting pain due to knee surgery.

The common marmoset as a translational model of age-related osteoarthritis

Age-related osteoarthritis (OA) is a degenerative joint disease characterized by pathological changes in nearly every intra- and peri-articular tissue that contributes to disability in older adults. Studying the etiology of age-related OA in humans is difficult due to an unpredictable onset and insidious nature. A barrier in developing OA modifying therapies is the lack of translational models that replicate human joint anatomy and age-related OA progression. The purpose of this study was to determine whether the common marmoset is a faithful model of human age-related knee OA. Semi-quantitative microCT scoring revealed greater radiographic OA in geriatric versus adult marmosets, and the age-related increase in OA prevalence was similar between marmosets and humans. Quantitative assessments indicate greater medial tibial cortical and trabecular bone thickness and heterogeneity in geriatric versus adult marmosets which is consistent with an age-related increase in focal subchondral bone sclerosis. Additionally, marmosets displayed an age-associated increase in synovitis and calcification of the meniscus and patella. Histological OA pathology in the medial tibial plateau was greater in geriatric versus adult marmosets driven by articular cartilage damage, proteoglycan loss, and altered chondrocyte cellularity. The age-associated increase in medial tibial cartilage OA pathology and meniscal calcification was greater in female versus male geriatric marmosets. Overall, marmosets largely replicate human OA as evident by similar 1) cartilage and skeletal morphology, 2) age-related progression in OA pathology, and 3) sex differences in OA pathology with increasing age. Collectively, these data suggest that the common marmoset is a highly translatable model of the naturally occurring, age-related OA seen in humans.

Investigating subtle changes in facial expression to assess acute pain in Japanese macaques

Changes in facial expression provide cues for assessing emotional states in mammals and may provide non-verbal signals of pain. This study uses geometric morphometrics (GMM) to explore the facial shape variation in female Japanese macaques who underwent experimental laparotomy. Face image samples were collected from video footage of fourteen macaques before surgery and 1, 3, and 7 days after the procedure. Image samples in the pre-surgical condition were considered pain-free, and facial expressions emerging after surgery were investigated as potential indicators of pain. Landmarks for shape analysis were selected based on the underlying facial musculature and their corresponding facial action units and then annotated in 324 pre-surgical and 750 post-surgical images. The expression of pain is likely to vary between individuals. Tightly closed eyelids or squeezed eyes and lip tension were the most commonly observed facial changes on day 1 after surgery (p < 0.01974). A good overall inter-rater reliability [ICC = 0.99 (95% CI 0.75-1.0)] was observed with the method. The study emphasizes the importance of individualized assessment and provides a better understanding of facial cues to pain for captive macaque care.

Aprepitant Inhibits JNK and p38/MAPK to Attenuate Inflammation and Suppresses Inflammatory Pain

Substance P contributes to the pathogenesis of pain by acting on NK-1R, specialized sensory neurons that detect noxious stimuli. Aprepitant, an antagonist of NK-1R, is widely used to treat chemotherapy-induced nausea and vomiting. In this study, we used LPS-stimulated BV-2 microglia cell line and animal models of inflammatory pain to explore the analgesic effect of aprepitant on inflammatory pain and its underlying mechanism. The excitability of DRG neurons were measured using whole-cell patch-clamp recordings. The behavioral tests were measured and the morphological changes on inflamed paw sections were determined by HE staining. Changes in the expressions of cytokine were measured by using real-time quantitative PCR analysis and ELISA method. Immunofluorescence and western blotting were used to detect the microglia activation and MAPK. Aprepitant treatment significantly inhibited the excitability of DRG neurons. The pain behavior and the paw tissues inflammatory damage were significantly relived after the administration of aprepitant compared to formalin group. Aprepitant significantly suppressed the activation of microglia, phosphorylation of JNK and p38 MAPK, as well as the mRNA and protein expressions of MCP-1, TNF-α, IL-6, and IL-1β, in vivo and in vitro. The LPS-induced over-translocation into nucleus of NF-κBp65 was down-regulated following aprepitant treatment in BV-2 cells. The present study suggests that aprepitant attenuates inflammatory pain in mice via suppressing the phosphorylation of JNK and p38, and inhibiting the NF-κB signaling pathway.

Comparison of high-resolution magnetic resonance imaging and micro-computed tomography arthrography for in-vivo assessment of cartilage in non-human primate models

Background

Non-human primate (NHP) could be an interesting model for osteoarthritis (OA) longitudinal studies but standard medical imaging protocols are not able to acquire sufficiently high-resolution images to depict the thinner cartilage (compared to human) in an in vivo context. The aim of this study was thus to develop and validate the acquisition protocols for knee joint examination of NHP using magnetic resonance imaging (MRI) at 1.5 T and X-ray micro-computed tomography arthrography (µCTA).

Methods

The first phase of the study focused on developing dedicated in vivo HR-MRI and µCTA protocols for simultaneous acquisitions of both knee joints on NHP. For MR, a dedicated two-channel receiver array coil and acquisition sequence were developed on a 1.5 T Siemens Sonata system and tuned to respect safety issues and reasonable examination time. For µCTA, an experimental setup was devised so as to fulfill similar requirements. The two imaging protocols were used during a longitudinal study so as to confirm that repeated injections of loxaglic acid (contrast agent used for µCTA) didn't induce any bias in cartilage assessment and to compare segmentation results from the two modalities. Lateral and medial cartilage tibial plateaus were assessed using a common image processing protocol leading to a 3D estimation of the cartilage thickness.

Results

From HR-MRI and µCTA images, thickness distributions were extracted allowing for proper evaluation of knee cartilage thickness of the primates. Results obtained in vivo indicated that the µCTA protocol did not induce any bias in the measured cartilage parameters and moreover, segmentation results obtained from the two imaging modalities were consistent.

Conclusions

MR and µCTA are valuable imaging tools for the morphological evaluation of cartilage in NHP models which in turn can be used for OA studies.

Extending the MaqFACS to measure facial movement in Japanese macaques (Macaca fuscata) reveals a wide repertoire potential

Facial expressions are complex and subtle signals, central for communication and emotion in social mammals. Traditionally, facial expressions have been classified as a whole, disregarding small but relevant differences in displays. Even with the same morphological configuration different information can be conveyed depending on the species. Due to a hardwired processing of faces in the human brain, humans are quick to attribute emotion, but have difficulty in registering facial movement units. The well-known human FACS (Facial Action Coding System) is the gold standard for objectively measuring facial expressions, and can be adapted through anatomical investigation and functional homologies for cross-species systematic comparisons. Here we aimed at developing a FACS for Japanese macaques, following established FACS methodology: first, we considered the species' muscular facial plan; second, we ascertained functional homologies with other primate species; and finally, we categorised each independent facial movement into Action Units (AUs). Due to similarities in the rhesus and Japanese macaques' facial musculature, the MaqFACS (previously developed for rhesus macaques) was used as a basis to extend the FACS tool to Japanese macaques, while highlighting the morphological and appearance changes differences between the two species. We documented 19 AUs, 15 Action Descriptors (ADs) and 3 Ear Action Units (EAUs) in Japanese macaques, with all movements of MaqFACS found in Japanese macaques. New movements were also observed, indicating a slightly larger repertoire than in rhesus or Barbary macaques. Our work reported here of the MaqFACS extension for Japanese macaques, when used together with the MaqFACS, comprises a valuable objective tool for the systematic and standardised analysis of facial expressions in Japanese macaques. The MaqFACS extension for Japanese macaques will now allow the investigation of the evolution of communication and emotion in primates, as well as contribute to improving the welfare of individuals, particularly in captivity and laboratory settings.

Brain Activation in a Cynomolgus Macaque Model of Chymopapain-Induced Discogenic Low Back Pain: A Preliminary Study

Introduction

There is currently a lack of translatable, preclinical models of low back pain (LBP). Chymopapain, a proteolytic enzyme used to treat lumbar intervertebral disc (IVD) herniation, could induce discogenic LBP. The current study developed a behavioral model of discogenic LBP in nonhuman primates. Significant brain activation is observed in clinical LBP. Thus, the current study also sought to define brain activation over time in a macaque with discogenic LBP.

Methods

Responses to pressure applied to the back at L4/L5 were measured in eight adult male Macaca fasciculata using a pressure algometer. The nucleus pulpous of the IVD between L4 and L5 was aspirated and chymopapain (1 mg/mL) was injected under fluoroscopic guidance (n = 2). In two macaques, the nucleus pulpous was only aspirated. Brain activation in response to pressure applied to the lower back was assessed using a 3.0T magnetic resonance imaging scanner in four macaques before and 1, 3, 9, and 14 days after treatment.

Results

The mean (±SD) response pressure before treatment was 1.4 ± 0.1 kg. One day after chymopapain treatment, the response pressure decreased to 0.6 ± 0.05 kg (P < 0.01), suggestive of pressure hypersensitivity. Over time, the pressure thresholds following chymopapain treatment gradually returned to normal. Following aspiration only, the response pressure was 1.4 ± 0.05 kg, which was not significantly different from the uninjured controls. There was activation of the secondary somatosensory cortex and insular cortex one and three days after chymopapain treatment; there was no activation following aspiration only.

Conclusions

Enzymatic treatment of the nucleus pulpous leads to acute LBP and pressure-evoked activation in pain-related brain areas. The current model of discogenic LBP parallels clinical LBP and could be used to further elaborate the mechanism of acute LBP.

Gaps in Understanding Mechanism and Lack of Treatments: Potential Use of a Nonhuman Primate Model of Oxaliplatin-Induced Neuropathic Pain

The antineoplastic agent oxaliplatin induces an acute hypersensitivity evoked by cold that has been suggested to be due to sensitized central and peripheral neurons. Rodent-based preclinical studies have suggested numerous treatments for the alleviation of oxaliplatin-induced neuropathic pain, but few have demonstrated robust clinical efficacy. One issue is that current understanding of the pathophysiology of oxaliplatin-induced neuropathic pain is primarily based on rodent models, which might not entirely recapitulate the clinical pathophysiology. In addition, there is currently no objective physiological marker for pain that could be utilized to objectively indicate treatment efficacy. Nonhuman primates are phylogenetically and neuroanatomically similar to humans; thus, disease mechanism in nonhuman primates could reflect that of clinical oxaliplatin-induced neuropathy. Cold-activated pain-related brain areas in oxaliplatin-treated macaques were attenuated with duloxetine, the only drug that has demonstrated clinical efficacy for chemotherapy-induced neuropathic pain. By contrast, drugs that have not demonstrated clinical efficacy in oxaliplatin-induced neuropathic pain did not reduce brain activation. Thus, a nonhuman primate model could greatly enhance understanding of clinical pathophysiology beyond what has been obtained with rodent models and, furthermore, brain activation could serve as an objective marker of pain and therapeutic efficacy.

Development and characterization of various osteoarthritis models for tissue engineering

Osteoarthritis (OA) is characterized by a progressive loss of articular cartilage, subchondral bone sclerosis and synovial inflammation and is the most common chronic condition worldwide today. However, most treatments have focused on pain relief and OA symptoms. For these reasons, many ongoing studies are currently trying to develop efficient and successful therapies based on its pathology. Animal models that mimic the histopathology and symptoms of OA have a critical role in OA research and make it possible to investigate both secondary osteoarthritic changes due to a precedent event such as traumatic injury and naturally occurring changes for the development of therapeutics which can be tested in preclinical and clinical OA trials. We induced OA in various animal models including rats, rabbits and guinea pigs by chemical, surgical and naturally occurring methods. In particular, the Dunkin-Hartley guinea pig is very attractive as an OA animal model because OA slowly progresses which is similar to human primary OA. Thus, this animal model mimics the pathophysiological process and environment of human primary OA. Besides the spontaneous OA model, anterior cruciate ligament transection (ACLT) with medial meniscectomy and bilateral ovariectomy (OVX) as well as a chemical technique using sodium monoiodoacetate (MIA) were used to induce OA. We found that ACLT in the rat model induced OA changes in the histology and micro-CT image compared to OVX. The osteoarthritic change significantly increased following ACLT surgery in the rabbit model. Furthermore, we identified that OA pathogenic changes occurred in a time-dependent manner in spontaneous Dunkin-Hartley guinea pigs. The MIA injection model is a rapid and minimally invasive method for inducing OA in animal models, whereas the spontaneous OA model has a slow and gradual progression of OA similar to human primary OA. We observed that histological OA change was extraordinarily increased at 9 ½ months in the spontaneous OA model, and thus, the grade was similar with that of the MIA model. Therefore, this study reports on OA pathology using various animal models as well as the spontaneous results naturally occurring in an OA animal model which had developed cartilage lesions and progressive osteoarthritic changes.

[Pharmacological profile of a novel nonhuman primate model of knee osteoarthritis]

A number of promising compounds developed in rodent arthritis models lack efficacy in clinical osteoarthritis (OA) pain. To enhance successful translation of preclinical findings, a nonhuman primate (NHP) model of knee OA was developed and characterized using behavioral assessments designed for use in the NHP. A unilateral medial meniscectomy (MMx) was performed and animals underwent an exercise regimen. Decreased ipsilateral knee pressure threshold, pressure "hyperalgesia", and decreased ipsilateral weight bearing, suggestive of pain at rest were observed. The sensitivity of the pain-related behaviors to pharmacological manipulation was evaluated. A single dose of the opioid morphine reduced pain-related behaviors. Likewise, the serotonin-norepinephrine reuptake inhibitor duloxetine reduced pain-related behavior, and efficacy was similar to that of morphine. By contrast, the anticonvulsant pregabalin did not significantly affect pain-related behavior. Repeated dosing with the non-steroidal anti-inflammatory drug (NSAID) diclofenac reduced pain-related behaviors whereas repeated dosing with the NK₁ receptor antagonist aprepitant did not. The drug effects observed in the NHP OA model mirror the efficacy observed clinically.

Traumatic osteoarthritis-induced persistent mechanical hyperalgesia in a rat model of anterior cruciate ligament transection plus a medial meniscectomy

Background

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage degeneration, subchondral bone changes, osteophyte formation, and synovitis. A major symptom is pain that is triggered by peripheral and central changes within the pain pathways. Some surgery-induced joint instability rat models of OA were described to mimic traumatic OA. Several behavioral tests were developed to access OA-induced pain. However, follow-up in most studies usually only occurred for about 4 weeks. Since traumatic OA is a chronic disease which gradually develops after trauma, the pattern of pain might differ between early and late stages after the trauma.

Purpose

To observe the time-dependent development of hypersensitivity after traumatic OA and to determine the best timing and methods to investigate traumatic OA-induced pain.

Methods

Anterior cruciate ligament transection plus medial meniscectomy was used to induce traumatic OA in Sprague-Dawley rats. Traumatic OA-induced pain was evaluated using four different behavioral tests for 15 weeks.

Results

A significant difference in mechanical hypersensitivity developed throughout the observational period. It was worst in the first 3 weeks after the operation, then became less significant after 5 weeks but persisted. There were no differences in thermal hyperalgesia or motor coordination.

Conclusion

Traumatic OA induced mechanical hyperalgesia but did not cause thermal hyperalgesia or influence motor coordination. Furthermore, to investigate chronic pain induced by OA, the observational period should be at least 5 weeks after the intervention. These findings may help in further research and improve our understanding of traumatic OA-induced pain mechanisms.

Antinociceptive effect of clinical analgesics in a nonhuman primate model of knee osteoarthritis

A number of potential analgesic pharmacotherapies developed in preclinical osteoarthritis animal models have failed clinical trials. A possible basis for the lack of translation of preclinical findings to clinical efficacy is the use of a preclinical species that is distinct from that of humans. The current study tested clinical analgesics in a nonhuman primate model of knee osteoarthritis. Following a medial meniscectomy, the animals developed a robust ipsilateral reduction in knee pressure threshold (hyperalgesia) and an ipsilateral reduction in weight bearing (resting pain). The serotonin-noradrenalin reuptake inhibitor duloxetine and opioid morphine increased ipsilateral pressure threshold and weight bearing. By contrast, the anticonvulsant pregabalin did not affect either pressure hyperalgesia or resting pain. The current findings in the nonhuman primate model of osteoarthritis parallel clinical findings, in that duloxetine and opioids are used in the management of osteoarthritis pain whereas pregabalin is not. The current findings also suggest the possible differentiation of pharmacotherapeutics in a nonhuman primate model, of distinguishing potential clinically useful analgesics for the management of osteoarthritic pain from those that are not.