Intra-articular injection of collagenase induced experimental osteoarthritis of the lumbar facet joint in rats

Re-thinking osteoarthritis pathogenesis: what can we learn (and what do we need to unlearn) from mouse models about the mechanisms involved in disease development

Efforts to develop effective disease-modifying drugs to treat osteoarthritis have so far proved unsuccessful with a number of promising drug candidates from pre-clinical studies failing to show efficacy in clinical trials. It is therefore timely to re-evaluate our current understanding of osteoarthritis pathogenesis and the similarities and differences in disease development between commonly used pre-clinical mouse models and human patients. There is substantial heterogeneity between patients presenting with osteoarthritis and mounting evidence that the pathways involved in osteoarthritis (e.g. Wnt signalling) differ between patient sub-groups. There is also emerging evidence that the pathways involved in osteoarthritis differ between the STR/ort mouse model (the most extensively studied mouse model of spontaneously occurring osteoarthritis) and injury-induced osteoarthritis mouse models. For instance, while canonical Wnt signalling is upregulated in the synovium and cartilage at an early stage of disease in injury-induced osteoarthritis mouse models, this does not appear to be the case in the STR/ort mouse. Such findings may prove insightful for understanding the heterogeneity in mechanisms involved in osteoarthritis pathogenesis in human disease. However, it is important to recognise that there are differences between mice and humans in osteoarthritis pathogenesis. A much more extensive array of pathological changes are evident in osteoarthritic joints in individual mice with osteoarthritis compared to individual patients. There are also specified differences in the pathways involved in disease development. For instance, although increased TGF-β signalling is implicated in osteoarthritis development in both mouse models of osteoarthritis and human disease, in mice, this is mainly mediated through TGF-β3 whereas in humans, it is through TGF-β1. Studies in other tissues have shown TGF-β1 is more potent than TGF-β3 in inducing the switch to SMAD1/5 signalling that occurs in osteoarthritic cartilage and that TGF-β1 and TGF-β3 have opposing effects on fibrosis. It is therefore possible that the relative contribution of TGF-β signalling to joint pathology in osteoarthritis differs between murine models and humans. Understanding the similarities and differences in osteoarthritis pathogenesis between mouse models and humans is critical for understanding the translational potential of findings from pre-clinical studies.

Establishment of a bipedal rat model of lumbar facet joint osteoarthritis using intraarticular injection of urinary plasminogen activator

Background

Previous studies have demonstrated that by injecting uPA into the lumbar facet joints (LFJ) of normal rats, a rat LFJOA animal model can be successfully established. However, there is no evidence that intraarticular injection of uPA can induce or much serious osteoarthritis in bipedal rats, which biomechanics is much more similar to human than normal rats. To investigate whether intraarticular injection of urinary plasminogen activator (uPA) can induce LFJOA and low back pain symptoms in bipedal rats.

Methods

An experimental study on the construction of a modified animal model of lumbar facet joints osteoarthritis (LFJOA) which biomechanics is similar to human. Sprague–Dawley rats were treated with intraarticular injection of uPA in the L5–L6 facet joints (uPA group, n = 15) or saline (saline group, n = 15). The forelimbs of both two group rats were amputated. Mechanical and thermal hyperalgesia in the ipsilateral hind paws were evaluated using von Frey hairs and a thermoalgesia instrument, respectively. Toluidine blue staining, hematoxylin–eosin staining, and immunohistochemical examination of the LFJ was performed.

Results

The saline group rats have not demonstrated significant osteoarthritis in rats LFJ after surgery. The uPA group has not been induced significantly higher mechanical and thermal hyperalgesia in comparison with the saline group. But intraarticular injection of uPA in biped rats induced significantly stronger articular cartilage damage, synovitis, and proliferation of synovial cells in the LFJ. Inflammatory factors such as iNOS, IL-1β, and TNF-a were more significantly expressed in bipedal rat injected with uPA (p < 0.05).

Conclusions

Intraarticular injection of uPA can induce LFJOA in bipedal rats, while upright posture does not induce osteoarthritis in rats LFJ in the short term.

Intra-articular MMP-1 in the spinal facet joint induces sustained pain and neuronal dysregulation in the DRG and spinal cord, and alters ligament kinematics under tensile loading

Chronic joint pain is a major healthcare challenge with a staggering socioeconomic burden. Pain from synovial joints is mediated by the innervated collagenous capsular ligament that surrounds the joint and encodes nociceptive signals. The interstitial collagenase MMP-1 is elevated in painful joint pathologies and has many roles in collagen regulation and signal transduction. Yet, the role of MMP-1 in mediating nociception in painful joints remains poorly understood. The goal of this study was to determine whether exogenous intra-articular MMP-1 induces pain in the spinal facet joint and to investigate effects of MMP-1 on mediating the capsular ligament’s collagen network, biomechanical response, and neuronal regulation. Intra-articular MMP-1 was administered into the cervical C6/C7 facet joints of rats. Mechanical hyperalgesia quantified behavioral sensitivity before, and for 28 days after, injection. On day 28, joint tissue structure was assessed using histology. Multiscale ligament kinematics were defined under tensile loading along with microstructural changes in the collagen network. The amount of degraded collagen in ligaments was quantified and substance P expression assayed in neural tissue since it is a regulatory of nociceptive signaling. Intra-articular MMP-1 induces behavioral sensitivity that is sustained for 28 days (p < 0.01), absent any significant effects on the structure of joint tissues. Yet, there are changes in the ligament’s biomechanical and microstructural behavior under load. Ligaments from joints injected with MMP-1 exhibit greater displacement at yield (p = 0.04) and a step-like increase in the number of anomalous reorganization events of the collagen fibers during loading (p ≤ 0.02). Collagen hybridizing peptide, a metric of damaged collagen, is positively correlated with the spread of collagen fibers in the unloaded state after MMP-1 (p = 0.01) and that correlation is maintained throughout the sub-failure regime (p ≤ 0.03). MMP-1 injection increases substance P expression in dorsal root ganglia (p < 0.01) and spinal cord (p < 0.01) neurons. These findings suggest that MMP-1 is a likely mediator of neuronal signaling in joint pain and that MMP-1 presence in the joint space may predispose the capsular ligament to altered responses to loading. MMP-1-mediated pathways may be relevant targets for treating degenerative joint pain in cases with subtle or no evidence of structural degeneration.

Spontaneous Facet Joint Osteoarthritis in NFAT1-Mutant Mice: Age-Dependent Histopathologic Characteristics and Molecular Mechanisms

BACKGROUND

Facet joint (FJ) osteoarthritis (FJOA) is a widely prevalent spinal disorder but its pathogenesis remains unclear, largely due to the difficulties in conducting longitudinal human studies and lack of spontaneous-FJOA animal models for mechanistic investigations. This study aimed to investigate whether spontaneous FJOA occurs in mice bearing mutant NFAT1 (nuclear factor of activated T cells 1) transcription factor.

METHODS

The lumbar FJs of 50 NFAT1-mutant mice and of 50 wild-type control mice, of both sexes, were examined by histopathology, quantitative gene expression analysis, semiquantitative immunohistochemistry, and a novel FJOA scoring system for semiquantitative assessment of the histopathologic changes at 2, 6, 12, and 18 months of age. Age-dependent and tissue-specific histopathologic and gene or protein expression changes were analyzed statistically.

RESULTS

FJs in NFAT1-mutant mice displayed significantly increased expression of specific catabolic genes (p < 0.05) and proteins (p < 0.001) in cartilage and synovium as early as 2 months of age, followed by early osteoarthritic structural changes such as articular surface fissuring and chondro-osteophyte formation at 6 months. More severe cartilage lesions, osteophytes, subchondral bone changes, synovitis, and tissue-specific molecular alterations in FJs of NFAT1-mutant mice were observed at 12 and 18 months. Osteoarthritic structural changes were not detected in FJs of wild-type mice at any ages, although age-related cartilage degeneration was observed at 18 months. The novel FJOA scoring system had high intraobserver and interobserver reproducibility (correlation coefficients: r > 0.97). Whole-joint FJOA scoring showed significantly higher OA scores in FJs of NFAT1-mutant mice compared with wild-type mice at all time points (p = 0.0033 at 2 months, p = 0.0001 at 6 months, p < 0.0001 at 12 and 18 months).

CONCLUSIONS

This study has identified the NFAT1-mutant mouse as a novel animal model of spontaneous FJOA with age-dependent and slowly progressing osteoarthritic features, developed the first FJOA scoring system, and elucidated the molecular mechanisms of NFAT1 mutation-induced FJOA.

CLINICAL RELEVANCE

This murine FJOA model resembles the features of human FJOA and may provide new insights into the pathogenesis of and therapeutic strategies for FJOA in humans.

Upregulation of P2Y12 inhibits chondrocyte apoptosis in lumbar osteoarthritis through the PI3K/AKT signaling pathway

Lumbar facet osteoarthritis (FJOA) is a major cause of severe lower back pain and disability worldwide. However, the mechanism underlying cartilage degeneration in FJOA remains unclear. The purpose of this study was to investigate the regulation and mechanism of P2Y12 on chondrocyte apoptosis in FJOA. The experimental rats were randomly divided into non-operation (n = 20) and operation groups (n = 20). In the operation group, Sodium iodoacetate (MIA, Sigma, 200 mg/mL) was injected into the right L4/5 facet process using a blunt nanoneedle 26 (WPI, Sarasota, FL, USA) under the control of an injection pump. The final injection volume was 5µL and the injection rate was 2µL/min. The facet joint was removed four weeks after surgery. After the operation, samples were stored at -80 °C until further use, whereby the right facet joints in each group were tested. Hematoxylin and eosin (HE) and iron-red solid green staining were used to observe the degeneration of articular chondrocytes in rats. Immunohistochemistry and western blotting were used to observe the expressions of P2Y12, Matrix metalloproteinase 13 (MMP13), Collagen II (COL2), and other cartilage degeneration and apoptosis-related genes. Co-localization of P2Y12-cleaved caspase-3 in the apoptosis model was detected by dual-standard immunofluorescence staining. Apoptosis was also detected by flow cytometry and TUNEL assay.P2Y12 is highly expressed in OA cartilage tissue, and inhibits IL-1β -induced chondrocyte apoptosis through PI3K/AKT signaling pathway, thus playing a certain protective role on cartilage.

Frailty and pain, human studies and animal models

The hypothesis that pain can predispose to frailty development has been recently investigated in several clinical studies suggesting that frailty and pain may share some mechanisms. Both pain and frailty represent important clinical and social problems and both lack a successful treatment. This circumstance is mainly due to the absence of in-depth knowledge of their pathological mechanisms. Evidence of shared pathways between frailty and pain are preliminary. Indeed, many clinical studies are observational and the impact of pain treatment, and relative pain-relief, on frailty onset and progression has never been investigated. Furthermore, preclinical research on this topic has yet to be performed. Specific researches on the pain-frailty relation are needed. In this narrative review, we will attempt to point out the most relevant findings present in both clinical and preclinical literature on the topic, with particular attention to genetics, epigenetics and inflammation, in order to underline the existing gaps and the potential future interventional strategies. The use of pain and frailty animal models discussed in this review might contribute to research in this area.

Solanum xanthocarpum fruit extract promotes chondrocyte proliferation in vitro and protects cartilage damage in collagenase induced osteoarthritic rats (article reference number: JEP 114028)

ETHNOPHARMACOLOGICAL RELEVANCE

Osteoarthritis (OA), a degenerative joint disease, is characterized by cartilage erosion and matrix degradation. Solanum xanthocarpum Schrad. & Wendl. fruits (SXF) and leaves have long been used as folk remedy in the treatment of pain in rheumatism.

AIM OF THE STUDY

This study was aimed to investigate the phytochemical components and protective benefits of SXF on in vitro chondrocytes proliferation, and in vivo suppression of collagenase-induced OA.

MATERIALS AND METHODS

Phytochemical components in ethanolic SXF extract were evaluated using gas chromatography-mass spectrometry (GC-MS). Effect of SXF on in vitro cell proliferation of primary chondrocytes was determined by cell proliferation assay and cell cycle analysis by flow cytometry. OA was induced in the right knees of rats through intra-articular injection of collagenase type-II. To evaluate in vivo preventive function of SXF, body weight, blood ALP, histopathological changes in the knee joint, proteoglycan, and collagen content were determined. The mRNA expression of COL-2, MMP-3 and COX-2 genes through qRT-PCR was studied. Antioxidant activities, total phenolics and flavonoid contents of SXF were also examined.

RESULTS

GC-MS analysis revealed that SXF constitutes 28 phytochemicals including flavonoids (3-methoxy apigenin, quercetin, luteolin), tannin (quinic acid), terpenes (oleanolic acid, lupeol, psi.psi carotene), phytosterols (campesterol, stigmasterol, β-sitosterol), and ascorbic acid. In vitro studies demonstrated that SXF enhanced the cell proliferation in a dose-dependent manner and has no cytotoxic effect on primary chondrocytes. In vivo study suggests that SXF protects the cartilage destruction induced by collagenase. The histological study revealed that SXF restored the synthesis of collagen and proteoglycan, vital factors for cartilage restoration, and reduced the arthritic score. An up-regulation in COL-2 expression and suppression of MMP-3 and COX-2 were detected by qRT-PCR analysis. Thus, in vivo study suggests the protective effects of SXF on cartilage destruction induced by collagenase.

CONCLUSIONS

Our results imply that SXF benefits and ameliorates OA by enhancing the chondrocytes proliferation and preventing the articular cartilage damage through the restoration of their structural molecules, arthritic score reduction, suppression of MMP-3 and COX-2 expression level and up regulation of COL-2 genes expression. These results suggest that SXF could be a promising alternative treatment candidate for osteoarthritis.

Antiosteoarthritic effect of Punica granatum L. peel extract on collagenase induced osteoarthritis rat by modulation of COL-2, MMP-3, and COX-2 expression

Osteoarthritis (OA) is a chronic degenerative and musculoskeletal disorder. The toxicity associated with nonsteroidal antiinflammatory drugs (NSAIDs) limits its use in the management of OA. To ameliorate these toxicities, natural antioxidants can be used as substitutes for the management of OA. Therefore, this study is aimed to investigate the prophylactic mechanisms of Punica granatum L. peel (PGP) in collagenase-induced OA rat compared with indomethacin. OA was induced in female Sprague Dawley rats by intraarticular injection of collagenase type-II and treated with PGP (250 and 500 mg/kg body wt) and a positive control (PC) indomethacin (3 mg/kg body wt). The results demonstrated that PGP reduced the collagenase induced OA as compared with indomethacin treated group through reducing blood ALP (P < .001) and significantly (P < .001) inhibited cartilage erosion as indicated in histological slides with retention of collagen and proteoglycan content. Quantitative real-time PCR analysis revealed the considerable (P < .05) upregulation in the expression of COL-2 gene and downregulation of MMP-3 and COX-2 genes in the PGP treated group. The high phenolic content (633 ± 1.16 mg/GAE) and flavonoid content (420.3 ± 2.14 mg/RE) contribute to the strong antioxidant activity with IC50 value (320 ± 2.2 μg/mL) of DPPH free radical scavenging activity. These results need further validation in clinical studies and thus, PGP could be developed as a preventive drug treatment for OA.

Intra-articular collagenase in the spinal facet joint induces pain, DRG neuron dysregulation and increased MMP-1 absent evidence of joint destruction

Degeneration is a hallmark of painful joint disease and is mediated by many proteases that degrade joint tissues, including collagenases. We hypothesized that purified bacterial collagenase would initiate nociceptive cascades in the joint by degrading the capsular ligament's matrix and activating innervating pain fibers. Intra-articular collagenase in the rat facet joint was investigated for its effects on behavioral sensitivity, joint degeneration, and nociceptive pathways in the peripheral and central nervous systems. In parallel, a co-culture collagen gel model of the ligament was used to evaluate effects of collagenase on microscale changes to the collagen fibers and embedded neurons. Collagenase induced sensitivity within one day, lasting for 3 weeks (p < 0.001) but did not alter ligament structure, cartilage health, or chondrocyte homeostasis. Yet, nociceptive mediators were increased in the periphery (substance P, pERK, and MMP-1; p ≤ 0.039) and spinal cord (substance P and MMP-1; p ≤ 0.041). The collagen loss (p = 0.008) induced by exposing co-cultures to collagenase was accompanied by altered neuronal activity (p = 0.002) and elevated neuronal MMP-1 (p < 0.001), suggesting microscale collagen degradation mediates sensitivity in vivo. The induction of sustained sensitivity and nociception without joint damage may explain the clinical disconnect in which symptomatic joint pain patients present without radiographic evidence of joint destruction.

Development of a novel rat model of lumbar facet joint osteoarthritis induced by persistent compressive injury

The aim of the present study was to develop a novel animal model of lumbar facet joint osteoarthritis induced by persistent compressive injury. An intraspinal compression spring was randomly implanted into either the L4/5 or the L5/6 spinal segments of 40 Sprague Dawley (SD) rats to induce compression. Sham-operations were used in the other segment of the same rats as the control levels. The animals were sacrificed at 7, 14, 28, 42 and 56 days after surgery, prior to the radiological confirmation of the spring location. Degeneration of the lumbar facet joints was evaluated by macroscopic observation in addition to histological and immunohistological analyses. The results of this present study revealed the absence of spring dislocation during the entire observation period. Macroscopic and Osteoarthritis Research Society International scores of the compression levels were found to be higher in the compression levels compared with those noted in the control levels (P<0.05). In addition, interleukin-1β and tumor necrosis factor-α expression in the compression levels were increased over time compared with those recorded in the control levels. In conclusion, persistent compressive injury may induce degeneration of the lumbar facet joint. This novel animal model could serve as a useful tool for further studies into the mechanisms of action and potential treatment of lumbar facet joint osteoarthritis.

Comparison of early-stage changes of osteoarthritis in cartilage and subchondral bone between two different rat models

Osteoarthritis (OA) is a chronic degenerative joint disease and the major cause of joint pain and disability in the elderly. It is mainly characterized by articular cartilage degradation and subchondral bone remodeling. There are two main types of OA: natural occurring OA and secondary OA, mainly associated with aging and trauma, respectively. In this study, we established two OA models in rat knee joints to simulate the two types of OA, using the type II collagenase injection (CI) and anterior cruciate ligament transection (ACLT), respectively. After intervention for 2-6 weeks, cartilage and subchondral bone changes were detected in histological staining, immunochemistry, and micro-CT. Results showed that both models with typical pathology changes of OA were successfully induced, while the development and severity of OA process in the models were different. In ACLT rats, the cartilage damage was milder, lasted for a shorter time, and subchondral bone reconstruction occurred earlier, compared with the changes in CI rats. The cartilage damage was secondary to subchondral bone change in ACLT rats, while subchondral bone change was secondary to cartilage degeneration in CI rats. In conclusion, the interaction between cartilage and subchondral bone is different between the natural-occurring and secondary OA models. These two models not only suggest potential different mechanisms of the two types of OA, but also provide new directions for OA treatment and prevention.

Can Collagenase Be Used in the Treatment of Adhesive Capsulitis?

BACKGROUND

The objective of this study was to evaluate the efficacy of subacromial injections of collagenase and corticosteroid in rats with experimentally induced adhesive capsulitis.

METHOD

Thirty adult Wistar albino male rats were distributed into 3 groups of 10 rats each after stabilization of their shoulders for 3 weeks: the first group received a single dose of 0.002 mg (0.25 mL) subacromial collagenase; the second group received a single dose of 1.60 mg (0.25 mL) subacromial steroid, and the third group received a single dose of 0.25 mL subacromial saline solution. One week later, we investigated shoulder range of motions, collagen content of the shoulder, and joint cartilage structure.

RESULTS

There was no statistically significant difference in the cartilage damage between the groups (p > 0.05). Fibrosis measurements were significantly lower in the collagenase group than in the steroid and saline groups. There was no significant difference in fibrosis between the steroid and saline groups (p > 0.05). Abduction measurements were significantly higher in the collagenase group than in the steroid and saline groups (p < 0.001). No significant difference in the abduction measurements was observed between the saline and steroid groups (p > 0.05).

CONCLUSION

We observed that subacromial injections of collagenase Clostridium histolyticum effectively treated adhesive capsulitis. The results suggest that this treatment could be considered for use in patients with an intact rotator cuff.

Unilateral Osteotomy of Lumbar Facet Joint Induces a Mouse Model of Lumbar Facet Joint Osteoarthritis

STUDY DESIGN

The lumbar facet joint (LFJ) osteoarthritis (OA) model that highly mimics the clinical conditions was established and evaluated.

OBJECTIVE

Here, we innovatively constructed and evaluated the aberrant mechanical loading-related LFJ OA model.

SUMMARY OF BACKGROUND DATA

LFJ is the only true synovial joint in a functional spinal unit in mammals. The LFJ osteoarthritis is considered to contribute 15% to 45% of low back pain. The establish of animal models highly mimicking the clinical conditions is a useful tool for the investigation of LFJ OA. However, the previously established animal models damaged the LFJ structure directly, which did not demonstrate the effect of aberrant mechanical loading on the development of LFJ osteoarthritis.

METHODS

In the present study, an animal model for LFJ degeneration was established by the unilateral osteotomy of LFJ (OLFJ) in L4/5 unit to induce the spine instability. Then, the change of contralateral LFJ was evaluated by morphological and molecular biological techniques.

RESULTS

We showed that the OLFJ induced instability accelerated the cartilage degeneration of the contralateral LFJ. Importantly, the SRμCT elucidated that the three-dimensional structure of the subchondral bone changed in contralateral LFJ, indicated as the abnormity of bone volume/total volume ratio (BV/TV), trabecular pattern factor (Tb. Pf), and the trabecular thickness (Tb. Th). Immunostaining further demonstrated the uncoupled osteoclastic bone resorption, and bone formation in the subchondral bone of contralateral LFJ, indicated as increased activity of osteoclast, osteoblast, and Type H vessels.

CONCLUSION

We develop a novel LFJ OA model demonstrating the effect of abnormal mechanical instability on the degeneration of LFJ. This LFJ degeneration model that highly mimics the clinical conditions is a valuable tool to investigate the LFJ osteoarthritis.

LEVEL OF EVIDENCE

N/A.

Up-regulation of TRAF2 inhibits chondrocytes apoptosis in lumbar facet joint osteoarthritis

Tumor necrosis factor receptor-associated factor 2 (TRAF2) has been demonstrated that it plays a significant role in cell death receptor signal transduction. The purpose of this study was to investigate the expression of TRAF2 and its possible role in FJOA. We observed an up-regulation of TRAF2 in FJOA by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) compared to normal tissues. In vitro, we used TNF-α to stimulate Human SW1353 chondrosarcoma cells to establish the chondrocytes injury model. Western blot analysis revealed significant expression of TRAF2 and cleaved caspase-3/8 in SW1353 cells. Co-localization of TRAF2/cleaved caspase-3/8 was detected in the cells injury model by double-labeling immunofluorescent staining. We demonstrated a possible anti-apoptotic effect of TRAF2 in chondrocyte apoptosis in FJOA by knockdown of its expression with siRNA. Moreover, TRAF2 knockdown was demonstrated to enhance TNF-α-induced apoptosis by flow cytometry assay. In conclusion, our results show that the up-regulation of TRAF2 may play an important role in the inhibition of chondrocyte apoptosis of FJOA.

Tetrahydrohyperforin prevents articular cartilage degeneration and affects autophagy in rats with osteoarthritis

Osteoarthritis (OA) is a highly prevalent disease, which is associated with extracellular matrix degradation and cell death in articular cartilage. The aim of the present study was to identify whether tetrahydrohyperforin (IDN5706) ameliorates the degeneration of articular cartilage and affects autophagy in OA. The rat model of experimental OA was induced by intra-articular injection of collagenase solution. IDN5706 was administered intragastrically to rats for 6 weeks. Histopathological changes in articular cartilage were examined using hematoxylin and eosin (H&E) and safranin O staining, and Mankin scoring systems. The effect of IDN5706 on autophagy was examined using western blotting. ELISA was performed to detect cartilage inflammation. H&E and safranin O staining, Mankin scores, and electron microscopy indicated that IDN5706 could lessen the degeneration of articular cartilage in OA rats. In addition, western blotting revealed that IDN5706 treatment may activate the suppressed autophagy in OA rats. In conclusion, the present study demonstrated that IDN5706 was able to reduce the severity of experimental OA, alleviate the degeneration of articular cartilage, and affect autophagy in OA model rats.

Salmon Calcitonin Attenuates Degenerative Changes in Cartilage and Subchondral Bone in Lumbar Facet Joint in an Experimental Rat Model

Background

Facet joint degeneration (FJD) is one of the common causes of low back pain (LBP), and estrogen deficiency is one of the triggers for FJD. Calcitonin may possess the potential for treating osteoarthritis, but to date the hormone has not been studied in the treatment of FJD. Therefore, the aim of this study was to investigate the effects of salmon calcitonin (sCT) on FJD induced by estrogen deficiency after ovariectomy (OVX).

Material/Methods

Thirty female Sprague-Dawley rats were randomly assigned to 3 groups: the OVX group received bilateral OVX, the OVX + sCT group received subcutaneous administration of sCT (16 IU/kg/2 days) following bilateral OVX, and the Sham group received sham surgery. All rats were euthanized at 12 weeks post-OVX. Serum COMP level, cartilage degradation, and subchondral bone micro-architecture were evaluated.

Results

sCT relieved cartilage surface lesions, reduced histological score, and significantly increased cartilage thickness. The OVX + sCT group exhibited significantly increased expression of aggrecan, as well as significantly decreased levels of ADAMTS-4, MMP-13, and caspase-3. The results of micro-computed tomography analysis revealed that the OVX + sCT group exhibited higher BMD, BV/TV, and Tb.Th values but a lower Tb.Sp value than that of the OVX group. Serum COMP concentrations were significantly correlated with histological score and cartilage thickness.

Conclusions

sCT can inhibit the progression of FJD in OVX rats, which is attributed to its inhibitory effects on cartilage metabolism imbalance, chondrocyte apoptosis, and subchondral bone remodeling. Serum COMP has diagnostic potential for FJD.

Animal models for studying the etiology and treatment of low back pain

Chronic low back pain is a major cause of disability and health care costs. Effective treatments are inadequate for many patients. Animal models are essential to further understanding of the pain mechanism and testing potential therapies. Currently, a number of preclinical models have been developed attempting to mimic aspects of clinical conditions that contribute to low back pain (LBP). This review focused on describing these animal models and the main behavioral tests for assessing pain in each model. Animal models of LBP can be divided into the following five categories: Discogenic LBP, radicular back pain, facet joint osteoarthritis back pain, muscle-induced LBP, and spontaneous occurring LBP models. These models are important not only for enhancing our knowledge of how LBP is generated, but also for the development of novel therapeutic regimens to treat LBP in patients. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1305-1312, 2018.

The Interface of Mechanics and Nociception in Joint Pathophysiology: Insights From the Facet and Temporomandibular Joints

Chronic joint pain is a widespread problem that frequently occurs with aging and trauma. Pain occurs most often in synovial joints, the body's load bearing joints. The mechanical and molecular mechanisms contributing to synovial joint pain are reviewed using two examples, the cervical spinal facet joints and the temporomandibular joint (TMJ). Although much work has focused on the macroscale mechanics of joints in health and disease, the combined influence of tissue mechanics, molecular processes, and nociception in joint pain has only recently become a focus. Trauma and repeated loading can induce structural and biochemical changes in joints, altering their microenvironment and modifying the biomechanics of their constitutive tissues, which themselves are innervated. Peripheral pain sensors can become activated in response to changes in the joint microenvironment and relay pain signals to the spinal cord and brain where pain is processed and perceived. In some cases, pain circuitry is permanently changed, which may be a potential mechanism for sustained joint pain. However, it is most likely that alterations in both the joint microenvironment and the central nervous system (CNS) contribute to chronic pain. As such, the challenge of treating joint pain and degeneration is temporally and spatially complicated. This review summarizes anatomy, physiology, and pathophysiology of these joints and the sensory pain relays. Pain pathways are postulated to be sensitized by many factors, including degeneration and biochemical priming, with effects on thresholds for mechanical injury and/or dysfunction. Initiators of joint pain are discussed in the context of clinical challenges including the diagnosis and treatment of pain.

Factors that influence outcome in experimental osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is the most common joint disease but an effective pharmacological therapy has not been developed yet. To identify targets for treatment and ways to interfere with OA development and progression both spontaneous and induced OA models are still needed. In this narrative review it is discussed what variables can be identified that lead to variation in OA animal model studies.

DESIGN

Literature was screened (Pubmed) with the following terms; OA animal models in combination with species, age, strain, gender/sex, housing, diet, fighting, circadian rhythm, transgenic. Relevant articles were selected and additional papers were searched for and read for specific subtopics.

RESULTS

Studies with OA models are subject to a multitude of variables, stimuli and conditions that can influence the outcome of an animal experiment. Outcome will depend on amongst others; the model used, species and strain, age, gender, diet, housing conditions, circadian rhythm, timing of intervention, stress levels and activity. Variations in these variables can account for discrepancies between OA model experiments, intervention studies and conclusions.

CONCLUSION

To improve OA animal model research, investigators should be aware of all the stimuli and conditions that can interfere with disease development and disease intervention and take these into account in their study design and execution.

Establishment of a rat model of adjuvant-induced osteoarthritis of the lumbar facet joint

To study the establishment of adjuvant-induced osteoarthritis of the lumbar facet joint in a rat model. Complete Freund's adjuvant (experimental group) and saline (control group) were randomly injected into the right and left side of rat, respectively. The rats were killed, and degeneration of lumbar facet joint was evaluated at macroscopic level and scored based on OARSI scores system. Moreover, Interleukin-1β and tumor necrosis factor-α levels in the synovium were measured. The macroscopic scores and OARSI scores of experimental group were higher than the control group (P < 0.05). The concentration of tumor necrosis factor-α was significantly increased only on 3- and 7-day post-surgery when compared with controls, and interleukin-1β was increased on days 3,7 and 14 post-surgery (P < 0.05). The rat model of adjuvant can induce degeneration of the lumbar facet joint. It can be useful for studies on mechanisms and treatment of lumbar facet joint osteoarthritis.

Establishment of a rat model of lumbar facet joint osteoarthritis using intraarticular injection of urinary plasminogen activator

Lumbar facet joint (LFJ) osteoarthritis (OA) is an important etiology of low back pain. Several animal models of LFJ OA have been established using intraarticular injection of various chemicals. This study aimed to establish a rat model of LFJ OA using urinary plasminogen activator (uPA). Sprague-Dawley rats were treated with intraarticular injection in the L5-L6 facet joints with uPA (OA group, n = 40) or normal saline (vehicle group, n = 40). Mechanical and thermal hyperalgesia in the ipsilateral hind paws were evaluated using von Frey hairs and a thermoalgesia instrument, respectively. Toluidine blue staining, hematoxylin-eosin staining, and immunohistochemical examination of the LFJ was performed. Treatment with uPA induced cartilage damage, synovitis, and proliferation of synovial cells in the fact joints. The OA group showed significantly higher hyperalgesia in the hind paws in comparison with the vehicle group and normal controls (P < 0.05). Expression of IL-1β, TNF-α, and iNOS in the LFJ cartilage in the OA group was significantly increased (P < 0.05). A rat model of LFJ OA was successfully established using intraarticular injection of uPA. This animal model is convenient and shows good resemblance to human OA pathology.

Anti-inflammatory effects of Vitis thunbergii var. taiwaniana on knee damage associated with arthritis

Vitis thunbergii Sieb. et Zucc. var. taiwaniana Lu (VT) is an indigenous plant in Taiwan that is traditionally used for promoting joint health. In this study, we used in vitro primary human chondrocytes (PHCs) and two in vivo animal models to evaluate the anti-inflammatory effects of VT on arthritis. Results showed that the water extract of the stems and roots from VT (VT-SR) was rich in flavones and phenols with 1.1 mg/g of resveratrol, 6.7 mg/g of hopeaphenol, and 5.1 mg/g of (+)-ɛ-viniferin. VT-SR significantly scavenged DPPH radicals and inhibited prostaglandin E2 (PGE2) production in lipopolysaccharide (LPS)-induced PHCs without exhibiting significant cytotoxicity. In in vivo models, the VT-SR (500 mg/kg) significantly decreased serum PGE2 and knee 2-(18)F-fluoro-2-deoxy-D-glucose ((18)F-FDG) levels in LPS-induced acute inflammatory arthritis in rabbits. In addition, dietary supplementation with VT-SR for 28 days significantly alleviated type II collagenase-induced rat osteoarthritis with improvements in weight bearing and range of motion tests. In conclusion, our results suggest that the VT-SR is a good candidate for developing dietary supplements to prevent joint deterioration and inhibit inflammation.

Intra-articular injection of collagenase in the knee of rats as an alternative model to study nociception associated with osteoarthritis

INTRODUCTION

Animal models currently used in osteoarthritis-associated pain research inadequately reproduce the initiating events and structural pathology of human osteoarthritis. Conversely, intra-articular injection of collagenase is a structurally relevant model, as it induces articular degeneration both by digesting collagen from cartilage and by causing articular instability, thereby reproducing some of the main events associated with osteoarthritis onset and development. Here, we evaluated if the intra-articular injection of collagenase can be an alternative model to study nociception associated with osteoarthritis.

METHODS

Osteoarthritis was induced by two intra-articular injections of either 250 U or 500 U of collagenase into the left knee joint of adult male Wistar rats. A six weeks time-course assessment of movement- and loading-induced nociception was performed by the Knee-Bend and CatWalk tests. The effect of morphine, lidocaine and diclofenac on nociceptive behaviour was evaluated in animals injected with 500 U of collagenase. Joint histopathology was scored for both doses throughout time. The expression of transient receptor potential vanilloid 1 (TRPV1) in ipsilateral dorsal root ganglia (DRG) was evaluated.

RESULTS

An increase in nociceptive behaviour associated with movement and loading of affected joints was observed after intra-articular collagenase injection. With the 500 U dose of collagenase, there was a significant correlation between the behavioural and the histopathological osteoarthritis-like structural changes developed after six weeks. One week after injection of 500 U collagenase, swelling of the injected knee and inflammation of the synovial membrane were also observed, indicating the occurrence of an early inflammatory reaction. Behavioural changes induced by the 500 U dose of collagenase were overall effectively reversed by morphine and lidocaine. Diclofenac was effective one week after injection. TRPV1 expression increased six weeks after 500 U collagenase injection.

CONCLUSION

We conclude that the intra-articular injection of 500 U collagenase in the knee of rats can be an alternative model for the study of nociception associated with osteoarthritis, since it induces significant nociceptive alterations associated with relevant osteoarthritis-like joint structural changes.

Influence of Six Medicinal Herbs on Collagenase-Induced Osteoarthritis in Rats

Medicinal herbs have been effectively used for their anti-inflammatory activity, but their exact role has not yet been documented in scientific literature for the management of Osteoarthritis (OA). Since Sida cordifolia L., Piper longum L., Zingiber officinale Rosc., Ricinus communis L., Vitex negundo L. and Tribulus terrestris L. have been widely used in traditional medicine for their anti-inflammatory activity, to evaluate anti-osteoarthritic activity of these herbs, we used a collagenase type II-induced osteoarthritis (CIOA) rat model. Arthritis was induced in wistar rats by intra-articular injection of collagenase type II. Powders of herbs were given orally for 20 days as a suspension in water (270 mg/kg b. wt.). The effects of the treatment in the rats were monitored by physiological parameters like body weight, knee diameter, paw retraction, paw volume, glycosaminoglycan (GAG) release, radiography and histopathology of knee joint. Selected herbs have significantly prevented body weight loss and knee swelling compared to arthritic control (CIOA). All test groups, including indomethacin (standard drug, 3 mg/kg), significantly reduced paw volume compared to CIOA. GAG release in the serum was significantly lowered in herb treated groups compared to indomethacin. The anterior posterior radiographs of S. cordifolia and P. longum treated groups showed a protective effect against OA. Histopathology revealed protection in the structure of the articular cartilage and in chondrocyte pathology as well as reduced clefting. Treatment with herbs has shown chondroid matrix within normal limits. From the results, we observed that S. cordifolia and P. longum possess potent anti-osteoarthritic activity.

Characterization of a new animal model for evaluation and treatment of back pain due to lumbar facet joint osteoarthritis

OBJECTIVE

Osteoarthritic (OA) degeneration of the lumbar facet joints has been implicated in low back pain. This study was undertaken to investigate the biologic links between cellular and structural alterations within facet joint components and the development of symptomatic chronic back pain.

METHODS

We generated an animal model of facet joint degeneration by intraarticular injection of monosodium iodoacetate (MIA) into facet joints (L3-L4, L4-L5, L5-L6) of Sprague-Dawley rats. Pain sensation due to pressure, which mimics a mechanical stimulus for facet joint injury, was measured using an algometer. Pain response was also assessed in a straight leg raising test. Cartilage alterations were assessed by biochemical evaluation and microfocal computed tomography (micro-CT). Therapeutic modulation of chronic facet joint pain with the use of various pharmacologic agents was investigated.

RESULTS

MIA injection resulted in severely damaged facet joint cartilage, proteoglycan loss, and alterations of subchondral bone structure. Micro-CT analyses suggested that the behavioral hyperalgesia from facet joint degeneration was not associated with foraminal stenosis. The biologic and structural changes in facet joints were closely associated with sustained and robust chronic pain. Morphine and pregabalin markedly alleviated pressure hyperalgesia, while celecoxib (a selective inhibitor of cyclooxygenase 2 [COX-2]) produced moderate antihyperalgesic effects and the effect of ketorolac (an inhibitor of COX-1 and COX-2) was negligible.

CONCLUSION

Our findings demonstrate that MIA injection provides a useful model for the study of OA changes in the facet joint and indicate that facet joint degeneration is a major cause of chronic low back pain. The treatment results suggest that classes of drugs that are widely used to treat OA, such as nonsteroidal antiinflammatory drugs, may have limited efficacy once joint destruction is complete.

Lumbar facet joint compressive injury induces lasting changes in local structure, nociceptive scores, and inflammatory mediators in a novel rat model

Objective. To develop a novel animal model of persisting lumbar facet joint pain. Methods. Sprague Dawley rats were anaesthetized and the right lumbar (L5/L6) facet joint was exposed and compressed to ~1 mm with modified clamps applied for three minutes; sham-operated and naïve animals were used as control groups. After five days, animals were tested for hind-paw sensitivity using von Frey filaments and axial deep tissue sensitivity by algometer on assigned days up to 28 days. Animals were sacrificed at selected times for histological and biochemical analysis. Results. Histological sections revealed site-specific loss of cartilage in model animals only. Tactile hypersensitivity was observed for the ipsi- and contralateral paws lasting 28 days. The threshold at which deep tissue pressure just elicited vocalization was obtained at three lumbar levels; sensitivity at L1 > L3/4 > L6. Biochemical analyses revealed increases in proinflammatory cytokines, especially TNF-α, IL-1α, and IL-1β. Conclusions. These data suggest that compression of a facet joint induces a novel model of local cartilage loss accompanied by increased sensitivity to mechanical stimuli and by increases in inflammatory mediators. This new model may be useful for studies on mechanisms and treatment of lumbar facet joint pain and osteoarthritis.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the rat

OBJECTIVE

During the development of disease-modifying osteoarthritis (OA) drugs, rat models of OA are frequently used for a first assessment of in vivo efficacy. The most efficacious compound in the rat model may then be tested in a larger animal model before entering human trials. The aim of this study was to describe a histologic scoring system for use in different models of OA in rats that allows standardization and comparison of results obtained by different investigators.

METHODS

The experience of the authors with current scoring systems and the range of lesions observed in rat and human OA studies were considered in recommending this common paradigm for rat histologic scoring. Considerations were made for reproducibility and ease of use for new scorers. Additional scoring paradigms may be employed to further identify specific effects of some disease-modifying drugs.

RESULTS

Although the described scoring system is more complex than the modified Mankin scores, which are recommended for some other species, the reliability study showed that it is easily understood and can be reproducibly used, even by inexperienced scorers.

CONCLUSIONS

The scoring paradigm described here has been found to be sufficiently sensitive to discriminate between treatments and to have high reproducibility. Therefore we recommend its use for evaluation of different rat OA models as well as assessment of disease-modifying effects of treatments in these models.

Intra-articular magnesium sulfate (MgSO4) reduces experimental osteoarthritis and nociception: association with attenuation of N-methyl-D-aspartate (NMDA) receptor subunit 1 phosphorylation and apoptosis in rat chondrocytes

OBJECTIVE

To study the effects of intra-articular injection of magnesium sulfate (MgSO(4)) on the development of osteoarthritis (OA) and to examine concomitant changes in the nociceptive behavior of rats.

METHODS

OA was induced in Wistar rats with intra-articular injection of collagenase (500 U) in the right knee; the left knee was left untreated. In the OA+MgSO(4) group (n=7), the treated knee was injected with 500-microg (0.1-ml) MgSO(4) twice a week for 5 consecutive weeks starting at 1 week after collagenase injection; in the OA group (n=7), the same knee was injected with the same amount of physiological normal saline. In the MgSO(4) group (n=6), naïve rats received only MgSO(4) injections; in the control group (n=6), naïve rats received only physiological normal saline injections. Nociceptive behavior (mechanical allodynia and thermal hyperalgesia) on OA development was measured before and at 1, 2, 4, 6, and 8 weeks after collagenase injection, following which the animals were sacrificed. Gross morphology and histopathology were examined in the femoral condyles, tibial plateau, and synovia. Immunohistochemical analysis was performed to examine the effect of MgSO(4) on N-methyl-D-aspartate (NMDA) receptor subunit 1 phosphorylation (p-NR1) and apoptosis in the articular cartilage chondrocytes.

RESULTS

OA rats receiving intra-articular MgSO(4) injections showed a significantly lower degree of cartilage degeneration than the rats receiving saline injections. MgSO(4) treatment also suppressed synovitis. Mechanical allodynia and thermal hyperalgesia showed significant improvement in the OA+MgSO(4) group as compared to the OA group. Moreover, MgSO(4) attenuated p-NR1 and chondrocyte apoptosis in OA-affected cartilage.

CONCLUSIONS

Our results indicate that local intra-articular administration of MgSO(4) following collagenase injection in an experimental rat OA model (1) modulates chondrocyte metabolism through inhibition of cell NMDA receptor phosphorylation and apoptosis, (2) attenuates the development of OA, and (3) concomitantly reduces nociception.

Degeneration of normal articular cartilage induced by late phase osteoarthritic synovial fluid in beagle dogs

OBJECTIVE

To investigate the pathogenesis of late phase osteoarthritic (OA) synovial fluid (SF) on normal articular cartilage in vivo and provide an understanding of degenerative cartilage extending in OA joint.

METHODS

A random knee, each of 8 beagle dogs, received anterior cruciate ligament transection (ACLT) and was confirmed to have late phase OA degenerative changes at 24 weeks after operation. Thereafter, one random elbow of each canine was injected with autologous late phase OA knee SF. The contralateral elbow was injected with normal saline (NS) of the same volume as SF aspirated from ACLT knee. These two groups of elbows were labeled "SF" and "NS". 8 other beagle dogs were left intact and placed in Group Control. After aseptic arthrocentesis was performed weekly on both elbows for 24 weeks, morphological changes were observed in the cartilage of the elbows, and expressions of 7 biological etiological factors of chondrocytes of the elbows were determined in Group SF, Group NS and Group Control, respectively.

RESULTS

Morphological changes were observed in articular cartilage of the elbows in Group SF. Levels of unit area of collagen type I in the noncalcified, calcified and full zones of articular cartilage of the elbows in Group SF increased significantly. Level of unit area of collagen type III in the calcified zone of articular cartilage of the elbows in Group SF remained unchanged. Meanwhile, expressions of MMP-1 and MMP-3 of chondrocytes of the elbows in Group SF increased significantly. There was almost no difference between articular cartilage in Group NS and Group Control.

CONCLUSION

Based on these results, we conclude that OA degeneration of normal articular cartilage can be independently induced by late phase OA SF. Endogenous OA biological etiological factor may be one of the reasons causing degenerative cartilage extending in OA joint.