The temporomandibular joint (TMJ) undergoes degenerative changes among patients who suffer from arthritis, and yet the pathogenesis of TMJ osteoarthritis and rheumatoid arthritis is poorly understood. We hypothesized that sustained inflammation in the TMJ induces structural abnormalities, and accordingly characterized the disc and synovium in a novel model with double injections of complete Freund's adjuvant (CFA), using behavioral, morphological, cellular, and molecular assessments. Thirty-five days following double CFA injections in seven-week-old female Sprague-Dawley rats, the disc in the CFA-induced inflammation group demonstrated multiple degenerative changes, including marked thickening, opacity, and deformation. The discs in the CFA group further showed significantly greater wet and net weights, and elevated collagen, aggrecan, and total glycosaminoglycan contents. The synovium in the CFA-induced inflammation group showed marked infiltration of mononucleated cells and accumulated sub-synovial adipose tissue. Both the disc and synovium had significantly higher iNOS and IL-1β mRNA expression than controls (saline injections). These findings are consistent with our hypothesis that sustained TMJ inflammation, even within the presently observed 35 days, may be a predisposing factor for structural abnormalities. Insight into TMJ inflammation and degeneration is anticipated to improve our understanding of the pathogenesis of TMJ arthritis and help design clinically relevant strategies for tissue engineering.

Osteoarthritis (OA) is one form of degenerative joint disease characterized by progressive loss of articular cartilage, decreased function and is frequently accompanied by chronic pain. Given the success of arthroplasty as a treatment for late-stage OA, there is considerable interest in developing therapies pertaining to the management of pain associated with OA as well as therapies designed to slow or reverse the progression of the disease. To this end, establishment of relevant animal models that are amenable to testing novel therapies is of considerable value to the scientific community. Here, we describe a model of OA-related pain in which progressive joint destruction is induced by injection of monosodium iodoacetate into the articular space of the knee of the rat. Further, we describe three different methods to measure pain-related behaviors in this model: hind limb weight bearing, primary mechanical hyperalgesia, and hind limb grip strength.

OBJECTIVE Osteoarthritis (OA) pain mechanisms are poorly understood. We used the monosodium iodoacetate (MIA) model of knee OA to characterize changes in excitability during the course of OA in different classes of mechanosensitive afferents projecting to joint-associated tissues, and examine whether these afferent responses and pain behavior are correlated. METHODS Rats were injected intra-articularly with MIA (1mg in 50 μl). Hind-limb weight bearing was studied 3 (MIA3) and 14 (MIA14) days after MIA, followed by deep anesthesia and teased-nerve-fiber recordings. Spontaneous activity (SA) and mechanically evoked responses of A- and C-mechanosensitive fibers (AM and CM respectively, probably nociceptive) innervating tissues associated with the ipsilateral knee joint were examined. RESULTS MIA3 and MIA14 rats exhibited reduced ipsilateral weight bearing. SA (>0.02 impulses/s) occurred in ∼50% of CMs from MIA rats vs 0% in normals. SA firing rates in CMs were significantly higher than normal; decreased weight bearing was correlated with increased CM SA rates. Neither percentages of AMs with SA (20%) nor their firing rates (0-0.01 impulses/s) significantly increased after MIA. In contrast, in MIA rats AMs, but not CMs, exhibited decreased mechanical thresholds and increased firing rates in response to suprathreshold mechanical stimulation. CONCLUSIONS These findings of increased SA firing rate in CMs but not AMs and increased mechanical sensitivity of AMs, but not CMs, have not previously been reported. These are two distinct important physiological mechanisms that may underpin spontaneous pain (CMs) and stimulus-evoked pain (AMs) in OA. Our data contribute to a mechanism-based understanding of OA pain.

OBJECTIVE To investigate the relationship between inflammatory responses of the temporomandibular joint (TMJ) and the metacarpophalangeal (MCP) joint in clinically normal horses. ANIMALS 7 mature horses. PROCEDURES In each horse, 1 TMJ and 1 MCP joint were injected with lipopolysaccharide (LPS; 0.0025 μg). The contralateral TMJ and MCP joint were injected with saline (0.9% NaCl) solution. Synovial fluid samples were collected from all 4 joints over 24 hours after injection. Concentrations of interleukin-6, tumor necrosis factor-α, transforming growth factor-β, and total protein were measured via immunoassay. Horses were assessed for clinical signs of joint inflammation at each time point. RESULTS Concentrations of interleukin-6 were not significantly different between LPS-injected MCP joints and TMJs at any time point. Transforming growth factor-β concentrations were significantly increased in MCP joints, compared with concentrations in TMJs, at 12 and 24 hours after injection. Tumor necrosis factor-α concentrations were significantly higher in LPS-injected TMJs than in LPS-injected MCP joints at 1 and 6 hours after injection. Total protein concentration did not differ significantly between LPS-injected MCP joints and TMJs. Injection of LPS induced clinical inflammation at all time points; additionally, 2 MCP joints (but no TMJs) had an inflammatory response to injection of saline solution. CONCLUSIONS AND CLINICAL RELEVANCE The inflammatory response to LPS appeared to be attenuated more quickly in TMJs than in MCP joints of horses. The difference in response suggested that a lack of clinical osteoarthritis in the TMJ of horses could be attributable to a difference in cytokine response.

Studies to elucidate the pathophysiology of osteoarthrosis have been hampered by the lack of a rapid, reproducible animal model that mimics the histopathology and symptoms associated with the disease. The aim of this study is to evaluate the radiological, histological and histomorphometrical findings of four different concentrations of sodium iodoacetate (MIA) to create osteoarthrosis by using an arthrocentesis technique on rabbit temporomandibular joint (TMJ). 12 New Zealand white male rabbits received an injection of MIA (50 μl dose of 1.5, 2, 2.5, 3mg/ml concentrations) to a single joint of each group by arthrocentesis. Computed tomography (CT) images were obtained pre- and post-injections at 2, 4 and 6 weeks. Early osteoarthritic changes in the rabbit TMJ were found histologically at 4 weeks and with a 3mg/ml concentration of MIA. The mean subchondral bone volume depended on the concentration of MIA and was 62±2.6%, 63±4.1%, 42±3.6% and 38±3.8%, respectively. A minor abnormality was found on CT in six joints at the 4-week follow up. MIA injection and arthrocentesis offer a rapid and minimally invasive method of reproducing histologically osteoarthrotic lesions in the rabbit TMJ.

The proinflammatory and catabolic cytokine IL-1β has been implicated in the pathogenesis of osteoarthritis (OA) by mediating synovial inflammation and cartilage degeneration. Although synovial macrophages are suggested to be the source of IL-1β, the mechanism remains unclear. Ectopic deposition of hydroxyapatite (HA) crystals in joints is closely associated with OA and other arthropathies, but the precise role of HA in arthritis pathogenesis has not been clearly demonstrated. Here we show that HA crystals of a particular size and shape can stimulate robust secretion of proinflammatory cytokines IL-1β and IL-18 from murine macrophages in a NLRP3 inflammasome-dependent manner. HA-induced inflammasome activation is dependent on potassium efflux, generation of reactive oxygen species (ROS), and lysosomal damage, but independent of cell death. Mice lacking the inflammasome components are protected against HA-induced neutrophilic inflammation in the air-pouch model of synovitis, and they show decreased joint pathology accompanying spontaneous HA deposition in the ank-deficient mouse model of arthritis. Moreover, calcium crystal positive synovial fluids from some OA patients exhibited inflammasome-stimulatory activity in vitro. These results demonstrate that the NLRP3 inflammasome mediates the pathological effect of HA crystals in vitro and in vivo and suggest a critical role for the inflammasome in the pathogenesis of OA.

Animal models are useful to evaluate pharmacological therapies to alleviate joint pain. The present study characterized central neuropeptides modulation in the monoiodoacetate (MIA) rat model. Animals receiving a single 3mg MIA injection were euthanized at 3, 7, 14, 21 and 28 days post injection. Spinal cords were analyzed by liquid chromatography ion trap mass spectrometry. Up-regulations of the calcitonin gene-related peptide and substance P were observed starting on days 7 and 28 respectively, whereas big dynorphin(₁₋₃₂) content decreased significantly on day 14 in comparison to control animals (P<0.05). Preclinical drug evaluations using this model should be conducted between 7 and 21 days post injection when the lesions resemble most to human osteoarthritis.

BACKGROUND Conventional treatments for the articular diseases are often effective for symptom relief, but can also cause significant side effects and do not slow the progression of the disease. Several natural substances have been shown to be effective at relieving the symptoms of osteoarthritis (OA), and preliminary evidence suggests that some of these compounds may exert a favorable influence on the course of the disease. The objective of this study was to investigate the anti-inflammatory/chondroprotective potential of a Herbal and amino acid mixture containing extract of the Uncaria tomentosa, Boswellia spp., Lepidium meyenii and L-Leucine on the IL-1β-induced production of nitric oxide (NO), glycosaminoglycan (GAG), matrix metalloproteinases (MMPs), aggrecan (ACAN) and type II collagen (COL2A1) in human OA chondrocytes and OA cartilage explants. METHODS Primary OA chondrocytes or OA cartilage explants were pretreated with Herbal-Leucine mixture (HLM, 1-10 μg/ml) and then stimulated with IL-1β (5 ng/ml). Effect of HLM on IL-1β-induced gene expression of iNOS, MMP-9, MMP-13, ACAN and COL2A1 was verified by real time-PCR. Estimation of NO and GAG release in culture supernatant was done using commercially available kits. RESULTS HLM tested in these in vitro studies was found to be an effective anti-inflammatory agent, as evidenced by strong inhibition of iNOS, MMP-9 and MMP-13 expression and NO production in IL-1β-stimulated OA chondrocytes (p < 0.05). Supporting these gene expression results, IL-1β-induced cartilage matrix breakdown, as evidenced by GAG release from cartilage explants, was also significantly blocked (p < 0.05). Moreover, in the presence of herbal-Leucine mixture (HLM) up-regulation of ACAN and COL2A1 expression in IL-1β-stimulated OA chondrocytes was also noted (p < 0.05). The inhibitory effects of HLM were mediated by inhibiting the activation of nuclear factor (NF)-kB in human OA chondrocytes in presence of IL-1β. CONCLUSION Our data suggests that HLM could be chondroprotective and anti-inflammatory agent in arthritis, switching chondrocyte gene expression from catabolic direction towards anabolic and regenerative, and consequently this approach may be potentially useful as a new adjunct therapeutic/preventive agent for OA or injury recovery.

Osteoarthritis (OA) is an age-related joint disease that is characterized by degeneration of articular cartilage and chronic pain. Oxidative stress is considered one of the pathophysiological factors in the progression of OA. We investigated the effects of grape seed proanthocyanidin extract (GSPE), which is an antioxidant, on monosodium iodoacetate (MIA)-induced arthritis of the knee joint of rat, which is an animal model of human OA. GSPE (100 mg/kg or 300 mg/kg) or saline was given orally three times per week for 4 weeks after the MIA injection. Pain was measured using the paw withdrawal latency (PWL), the paw withdrawal threshold (PWT) and the hind limb weight bearing ability. Joint damage was assessed using histological and microscopic analysis and microcomputerized tomography. Matrix metalloproteinase-13 (MMP13) and nitrotyrosine were detected using immunohistochemistry. Administration of GSPE to the MIA-treated rats significantly increased the PWL and PWT and this resulted in recovery of hind paw weight distribution (P < 0.05). GSPE reduced the loss of chondrocytes and proteoglycan, the production of MMP13, nitrotyrosine and IL-1β and the formation of osteophytes, and it reduced the number of subchondral bone fractures in the MIA-treated rats. These results indicate that GSPE is antinociceptive and it is protective against joint damage in the MIA-treated rat model of OA. GSPE could open up novel avenues for the treatment of OA.

Osteoarthritis (OA) is a degenerative joint disease that is characterized by joint pain and a progressive loss of articular cartilage. Kaschin-Beck Disease is a form of endemic OA in China whose etiology is unclear, but epidemiological data indicate a possible link to trichothecenes mycotoxin exposure. In vitro, T-2 toxin, a trichothecenes mycotoxin, has been demonstrated to inhibit aggrecan synthesis and promote aggrecanase and pro-inflammatory cytokine production in cultured chondrocytes. To assess the effects of T-2 toxin on articular cartilage in vivo, Wistar rats were fed a diet containing T-2 toxin (100 ng/kg chow) for six and ten months. Following six months of T-2 toxin exposure, histopathological changes in femorotibial cartilage were characterized by chondrocyte degeneration/necrosis and loss, chondrocyte clones, and loss of proteoglycan staining of articular cartilage, sometimes involving the entire thickness of the cartilage in the tibial plateaus and femoral condyles. By ten months, in addition to these changes, there was evidence of cartilage fibration in some rats. In conclusion, T-2 toxin exposure in rats induced degenerative lesions in articular cartilage similar to spontaneous OA, lending support to an etiologic role of mycotoxins in Kaschin-Beck Disease. T-2 toxin-induced degenerative joint disease may be a useful model of metabolic polyarticular OA.

Osteoarthritis (OA) is a chronic pain condition characterized by pain during joint use as well as pain at rest (i.e., ongoing pain). Although injection of monosodium iodoacetate (MIA) into the intra-articular space of the rodent knee is a well established model of OA pain that is characterized by changes in weight bearing and hypersensitivity to tactile and thermal stimuli, it is not known if this procedure elicits ongoing pain. Further, the time-course and possible underlying mechanisms of these components of pain remain poorly understood. In these studies, we demonstrated the presence of ongoing pain in addition to changes in weight bearing and evoked hypersensitivity. Twenty-eight days following MIA injection, spinal clonidine blocked changes in weight bearing and thermal hypersensitivity and produced place preference indicating that MIA induces ongoing and evoked pain. These findings demonstrate the presence of ongoing pain in this model that is present at a late-time point after MIA allowing for mechanistic investigation.

To investigate the impact of an experimental model of osteoarthritis (OA) on spinal nociceptive processing and the role of the inhibitory endocannabinoid system in regulating sensory processing at the spinal level. Experimental OA was induced in rats by intraarticular injection of sodium mono-iodoacetate (MIA), and the development of pain behavior was assessed. Extracellular single-unit recordings of wide dynamic range (WDR) neurons in the dorsal horn were obtained in MIA-treated rats and saline-treated rats. The levels of endocannabinoids and the protein and messenger RNA levels of the main synthetic enzymes for the endocannabinoids (N-acyl phosphatidylethanolamine phospholipase D [NAPE-PLD] and diacylglycerol lipase α [DAGLα]) in the spinal cord were measured. Low-weight (10 gm) mechanically evoked responses of WDR neurons were significantly (P < 0.05) facilitated 28 days after MIA injection compared with the responses in saline-treated rats, and spinal cord levels of anandamide and 2-arachidonoyl glycerol (2-AG) were increased in MIA-treated rats. Protein levels of NAPE-PLD and DAGLα, which synthesize anandamide and 2-AG, respectively, were elevated in the spinal cords of MIA-treated rats. The functional role of endocannabinoids in the spinal cords of MIA-treated rats was increased via activation of cannabinoid 1 (CB(1)) and CB(2) receptors, and blockade of the catabolism of anandamide had significantly greater inhibitory effects in MIA-treated rats compared with control rats. Our findings provide new evidence for altered spinal nociceptive processing indicative of central sensitization and for adaptive changes in the spinal cord endocannabinoid system in an experimental model of OA. The novel control of spinal cord neuronal responses by spinal cord CB(2) receptors suggests that this receptor system may be an important target for the modulation of pain in OA.

Pain is a prominent feature of osteoarthritis (OA). To further understand the primary mechanisms of nociception in OA, we studied the expression of the phenotype markers calcitonin gene-related peptide (CGRP), isolectin B4 (IB4), and neurofilament 200 (NF200) in sensory neurons innervating the OA knee joint in rats. OA was induced in rats by intraarticular injection of 2 mg of mono-iodoacetate (MIA) into the knee. Neurons innervating the joint were identified by retrograde labeling with fluorogold in dorsal root ganglia (DRG) and colocalized with neurochemical markers by immunofluorescence. The total number of DRG cells was determined by stereologic methods in Nissl-stained sections. A 37% decrease in the number of fluorogold-backlabeled cells was observed in rats with OA when compared with control rats, even though no decrease in the total number of cells was observed. However, an increase in the number of medium/large cell bodies and a decrease in the number of the smallest cells were observed, suggesting the occurrence of perikarya hypertrophy. The percentage of CGRP-positive cells increased significantly, predominantly in medium/large cells, suggesting the occurrence of a phenotypic switch. Colocalization of CGRP and NF200 revealed no significant changes in the percentage of double-labeled cells, but an increase in the number of medium/large double-labeled cells was observed. No differences in the expression of either IB4 or NF200 were observed in fluorogold-backlabeled cells. These results indicate that MIA-induced OA causes an up-regulation of CGRP in different subpopulations of primary afferent neurons in DRG due to a phenotypic switch and/or cell hypertrophy which may be functionally relevant in terms of the onset of pain in this pathologic condition.

HASH(0x1e314270)

A rat model of osteoarthritis was used to investigate the effect of pre-treatment with capsaicin on the symptoms of osteoarthritis induced by the injection of monosodium iodoacetate. This model mimics both histopathology and symptoms associated of human osteoarthritis. Injection of monosodium iodoacetate, an inhibitor of glycolysis, into the femorotibial joints of rodents promotes loss of articular trabecular bone and invokes pain symptoms similar to those noted in human osteoarthritis. Twenty rats were divided in two groups either receiving placebo or monosodium iodoacetate. Each group was subdivided in two groups either receiving pre-treatment with capsaicin two weeks before monosodium iodoacetate injection or not, resulting in four groups of five rats each. The impact of a single intra-articular administration of capsaicin (0.5%) on the generation of evoked mechanical pain (hind limb weight bearing, automated von Frey monofilament and RotaRod tests) and bone lesions (micro-CT scan radiographic analyses of bone structure) following monosodium iodoacetate-induced osteoarthritis in rats was determined. Evoked mechanical pain as monitored over a period of 4 weeks after monosodium iodoacetate injection was abolished in capsaicin pre-treated animals and pain values are comparable to those of capsaicin controls. Chronic joint pathological changes such as bone erosion and trabecular damage were significantly reduced by pre-treatment with a single administration of capsaicin. Decrease of bone volume was considerably ameliorated and trabecular connectivity was substantially better in capsaicin pre-treated animals. Capsaicin, an agonist activator of the vanilloid nociceptors (TRPV1), appears to be effective in protecting bone from arthritic damage. The present results support the hypothesis that capsaicin-sensitive sensory neurons contribute to bone lesions in the monosodium iodoacetate-induced osteoarthritis rat model.

In a rabbit model of collagenase-induced osteoarthritis, the additive effects of intra-articular recombinant human growth hormone (GH) administration to hyaluronic acid (HA) were evaluated. After intra-articular collagenase injection, mature New Zealand white rabbits (n=30) were divided into 3 groups. Group 1 (control rabbits) received once weekly intra-articular saline injections for 4 weeks. Group 2 rabbits received 6 mg HA injections, and group 3 rabbits were injected with 6 mg HA and 3 mg recombinant human GH. These injections were initiated 4 weeks after collagenase injections. Lameness was observed for 9 weeks after collagenase injections. Macroscopic and histopathological knee joint findings were also evaluated at the end of 9 weeks after collagenase injections. Although all animals had lameness after collagenase injections, the duration and severity of lameness were significantly shorter and less severe in group 3 than group 1 and 2 (P<0.01). Macroscopic scores showed that femoral condyles of group 3 rabbits received significantly less cartilage damage than those of groups 1 and 2 rabbits (P<0.01). Histopathological score was also the lowest in group 3 (P<0.01). These results suggest that co-injection of intra-articular HA and recombinant human GH is more effective than HA injections alone in an osteoarthritis model.

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In most cases bisphosphonates are the first choice therapy for osteoporosis. We present a case of acute arthritis associated with once-weekly risedronate in a 58-year-old woman with osteoporosis. She developed arthritis 48 hours after the second dose of oral risedronate with elevated serum acute-phase reactants. There was no evidence of rheumatoid arthritis or seronegative arthritis. Her symptoms resolved rapidly with rest, however, recurred after the patient was rechallenged with the same drug 1 week later. Although the mechanism of this potential side effect remains speculative, it is thought to be as a result of the proinflammatory properties of aminobisphosphonates. With the increasing use of bisphosphonates in the treatment and prevention of osteoporosis, physicians should be well aware of this possible side effect of these drugs.

STUDY DESIGN.: To examine whether lidocaine cytotoxicity to chondrocytes has been implicated in the development of osteoarthritis of the zygapophysial joints. OBJECTIVE.: This study was performed to determine the effects of varying concentrations and exposure times of lidocaine on the viability and proteoglycan metabolism of rabbit zygapophysial chondrocytes in vitro. SUMMARY OF BACKGROUND DATA.: Zygapophysial joint injections are commonly administered with lidocaine for chronic spinal pain in orthopedic treatment. A lot of studies on the effect of zygapophysial joint injections are clinical, but many questions on the effect of lidocaine to zygapophysial chondrocytes remain unanswered. METHODS.: Cartilage was obtained from zygapophysial joints of adult rabbits. Chondrocytes in alginate beads were cultured in medium containing 6% fetal calf serum at 370 mOsmol at cell densities of 4 million cells/mL. They were then cultured for 24 hours under 21% oxygen with 0.125%, 0.25%, 0.5%, and 1% lidocaine, and without lidocaine as control. The cell viability profile across intact beads was determined by manual counting using fluorescent probes (LIVE/DEAD assay) and transmission electron microscopy. Lactate production was measured enzymatically as a marker of energy metabolism. Glycosaminoglycan (GAG) accumulation was measured using a modified dimethylmethylene blue assay. RESULTS.: Cell viability decreased in a time- and dose-dependent manner in the concentration range of 0.125% to 1.0% lidocaine under the confocal microscope. Under the electron microscope, apoptosis increased as the concentration of lidocaine increased. GAG accumulation/tissue volume decreases as the concentration of lidocaine increased. However, GAG produced per million cells and the rate of lactate production per live cell was significantly higher for cells cultured at 0.5% and 1% lidocaine than the control group. CONCLUSION.: While these in vitro results cannot be directly extrapolated to the clinical setting, this data suggestcaution in prolonged exposure of zygapophysial cartilage to high concentration lidocaine.

A monolithic drug-in-adhesive (MDIA) type patch containing meloxicam (MX) was designed with an acrylic adhesive, a solubility modulator increasing MX solubility, and enhancers. MDIA patches having one adhesive layer between the backing and the release liner give high productivity and improve patient compliance. The biggest problem to prepare MDIA patch including MX was poor solubility of MX. In this research, solubility modulators to increase solubility of MX and acrylic adhesives and skin permeation enhancers were investigated through solubility tests, in vitro skin permeation tests, and stability tests. Consequently, the composition of sodium methoxide (SM), an acrylic adhesive containing poly(vinyl pyrrolidone) blocks (MAS683), polyoxyethylene cetylether (BC-2), and diisopropanolamine (DIPA) made it possible for MX to be contained in an adhesive layer at a concentration of as much as 15 wt% without MX crystal and with high skin permeation over 400 microG/cm(2). Finally, the patch formulation containing MX (MX-patch) selected through our in vitro study was characterized by in vivo using an animal study to acquire pharmacokinetic (PK) parameters and to confirm the anti-inflammatory efficacy of MX-patch. In the animal study, MX-patch was compared with a commercially available piroxicam patch (PX-patch). The amount of MX delivered from MX-patch to the skin surface was believed to be higher than the amount of MX diffused from the skin tissue to circulatory system because the plasma concentration of MX continuously increased up to 32 h, the end time of PK study, although the patch samples were detached at 24 h. PX-patch produced a C(max) at 8 h. MX-patch showed better significant efficacy than PX-patch in adjuvant arthritis model.