Randomized controlled studies on the efficacy of antiarthritic agents in inhibiting cartilage degeneration and pain associated with progression of osteoarthritis in the rat

Amniotic suspension allograft improves pain and function in a rat meniscal tear-induced osteoarthritis model

BACKGROUND

Osteoarthritis is a degenerative disease of the knee that affects 250 million people worldwide. Due to the rising incidence of knee replacement and revision surgery, there is a need for a nonsurgical treatment to reduce pain and improve function in patients with knee osteoarthritis. Placental-derived allografts, such as an amniotic suspension allograft (ASA), provide growth factors and cytokines that could potentially modulate the inflammatory environment of osteoarthritis. The purpose of this study was to evaluate the efficacy of ASA in a rat medial meniscal tear (MMT) induced osteoarthritis model through histology, microCT, synovial fluid biomarkers, and behavioral testing.

METHODS

Rats underwent MMT surgery at day - 7; at day 0, rats were injected with either ASA, vehicle control, or fibroblast growth factor-18 (FGF18). Behavioral testing, including gait analysis, pain threshold, incapacitance, and knee swelling were evaluated in-life, along with histology, microCT analysis of cartilage, and synovial fluid testing post-sacrifice. One MMT cohort was sacrificed at day 10, the other at day 21. A third cohort acted as a safety arm and did not receive MMT surgery; these rats were injected with either vehicle control or ASA and evaluated at day 3 and day 21.

RESULTS

Behavioral testing showed a significant improvement in pain threshold, incapacitance, and gait following an injection of ASA. MicroCT showed significant improvements in cartilage thickness and attenuation at day 10 only, and histology showed no detrimental effects compared to the vehicle control at day 21. Synovial fluid analysis showed a significant increase in anti-inflammatory IL-10. The safety cohort showed no significant differences except for an increase in synovitis at day 21, which could be evidence of a xenogeneic response in this model.

CONCLUSIONS

In this study, an injection of ASA was well tolerated with no adverse events. Improvements in pain and function, along with cartilage properties at day 10, were observed. Increases in anti-inflammatory cytokines was also seen, along with no significant cartilage degeneration at day 21 compared to the vehicle control. This study provides evidence for the use of ASA as a nonsurgical treatment for knee OA.

Intra-Articular Injections of Curcumin Monoglucuronide TBP1901 Suppresses Articular Cartilage Damage and Regulates Subchondral Bone Alteration in an Osteoarthritis Rat Model

OBJECTIVE

Curcumin monoglucuronide (TBP1901) is highly water soluble and can convert to free form curcumin, which has pharmacological effects, on intravenous administration. This study aimed to investigate the effectiveness of TBP1901 intra-articular injections in an osteoarthritis (OA) rat model.

METHODS

Sixty-four male Wistar rats (12 weeks old) who underwent destabilized medial meniscus (DMM) surgery were randomly separated into the TBP1901 injection or saline solution (control) injection group. They were sacrificed at 1, 2, 6, or 10 weeks postoperatively (weeks 1, 2, 6, and 10; n = 8 for each group). TBP1901 (30 mg/mL) or saline solution of 50 μL was injected into the knee joints twice a week during weeks 1 and 2 to investigate the effects in the acute phase of posttraumatic (PT) OA or once a week during weeks 6 and 10 to investigate it in the chronic phase of PTOA. Histology, immunohistochemistry, and micro-computed tomography were performed to evaluate the changes in OA.

RESULTS

TBP1901 injections significantly reduced synovial inflammation at weeks 1 and 2, and tumor necrosis factor-α expression in the articular cartilage at week 6. The TBP1901 injections also significantly suppressed articular cartilage damage, subchondral bone (SB) plate thickening, SB plate perforation, and osteophyte formation at week 10.

CONCLUSIONS

TBP1901 intra-articular injections suppressed synovial inflammation in the acute phase of PTOA in DMM rats. In the chronic phase, TBP1901 suppresses articular cartilage damage and regulates SB plate changes.

Hypertension meets osteoarthritis - revisiting the vascular aetiology hypothesis

Osteoarthritis (OA) is a whole-joint disease characterized by subchondral bone perfusion abnormalities and neovascular invasion into the synovium and articular cartilage. In addition to local vascular disturbance, mounting evidence suggests a pivotal role for systemic vascular pathology in the aetiology of OA. This Review outlines the current understanding of the close relationship between high blood pressure (hypertension) and OA at the crossroads of epidemiology and molecular biology. As one of the most common comorbidities in patients with OA, hypertension can disrupt joint homeostasis both biophysically and biochemically. High blood pressure can increase intraosseous pressure and cause hypoxia, which in turn triggers subchondral bone and osteochondral junction remodelling. Furthermore, systemic activation of the renin-angiotensin and endothelin systems can affect the Wnt-β-catenin signalling pathway locally to govern joint disease. The intimate relationship between hypertension and OA indicates that endothelium-targeted strategies, including re-purposed FDA-approved antihypertensive drugs, could be useful in the treatment of OA.

Systematic analysis reveals that colony housing aligns gait profiles and strengthens link between histological and micro-CT bone markers in rat models of osteoarthritis

Osteoarthritis (OA) etiopathogenesis is complex with strong environmental/lifestyle determinants that, in laboratory animals, extend to social context and stress levels. This study seeks to identify whether colony housing of rats exerts a social impact on locomotion behaviors to influence alignment between symptomatic (gait) and structural (bone micro-CT measures, cartilage morphometry, and histology) OA outcome measures. Rats were randomly allocated to conventional (type IV; n = 48) or rat colony cage (RCC; n = 30) housing, further randomized to OA surgical models (ACLT + tMx, MMT or DMM) or no surgery (control), and maintained for 19 weeks during which multiple gait recordings were made. Standard histological grading and bone micro-CT data were collected at necropsy. Principal component analysis was used to summarize the variation in gait, micro-CT or histology. Linear mixed effects model or two-way ANOVA was employed to evaluate the impact of the housing system, surgery and time on gait, or micro-CT and histology components Analyses reveal that RCC exaggerates trends in gait change via a combined effect of the housing system and surgery. Intriguingly, RCC-housed nonoperated control rats showed similar gait changes to rats subjected to surgery; the latter exhibited significant structural joint changes in both systems. Stronger correlation between histological and micro-CT bone changes were found in medial and lateral tibia joint compartments of rats housed in RCC system. This study has established that rat social housing exaggerates outcomes in traditional histological measures of OA, generates stronger links between histology and micro-CT bone changes and removes gait differences as a variable in their etiology.

Knockdown of TRIM8 Attenuates IL-1β-induced Inflammatory Response in Osteoarthritis Chondrocytes Through the Inactivation of NF-κB Pathway

Osteoarthritis (OA) is a degenerative joint disease associated with inflammatory response. Tripartite motif 8 (TRIM8) is a member of TRIM family that has been found to regulate inflammation. The present study was aimed to evaluate the role of TRIM8 in OA chondrocytes. Our results showed that TRIM8 expression was significantly increased in interleukin 1 beta (IL-1β)-stimulated OA chondrocytes. To knock down the TRIM8 expression in chondrocytes, the chondrocytes were transfected with si-TRIM8. Knockdown of TRIM8 attenuated IL-1β-induced production of inflammatory mediators including nitric oxide and prostaglandin E₂. The increased expression levels of inducible nitric oxide synthase and cyclooxygenase-2 in IL-1β-induced chondrocytes were suppressed by TRIM8 knockdown. The IL-1β-induced production of proinflammatory cytokines including TNF-α and IL-6 was significantly decreased after transfection with si-TRIM8. Besides, knockdown of TRIM8 mitigated the IL-1β-induced decrease in aggrecan and collagen-II proteins expression and increase in matrix-degrading enzymes in chondrocytes. Furthermore, TRIM8 knockdown prevented IL-1β-induced nuclear factor kappa B (NF-κB) activation in chondrocytes. Taken together, these findings indicated that knockdown of TRIM8 attenuates IL-1β-induced inflammatory response in OA chondrocytes through the inactivation of NF-κB pathway. Thus, targeting TRIM8 might provide therapeutic treatment for OA.

Pharmacological characterization of the chronic phase of the monoiodoacetate-induced rat model of osteoarthritis pain in the knee joint

For patients with osteoarthritis (OA) of the knee, pain is the most debilitating symptom. Although it has been proposed that the chronic phase of the monoiodoacetate (MIA)-induced rodent model of knee joint pain may be superior to other chronic or acute OA models for assessing the analgesic efficacy of novel molecules, relatively few pharmacological studies have been conducted in the chronic phase of this model. Hence, this study was designed to use pharmacological methods to characterize the chronic phase of the MIA-induced rat model of knee joint OA pain. Rats received a single intraarticular injection of MIA at 2.5 mg or vehicle (saline) into the left (ipsilateral) knee joint. Pain behaviour was assessed by measuring paw withdrawal thresholds (PWTs) in the hindpaws pre-MIA injection and twice-weekly until study completion on day 42. Mechanical allodynia was fully developed in the ipsilateral hindpaws (PWTs ≤6 g) from day 7 and it persisted until day 42. MIA-injected rats with PWTs ≤6 g in the ipsilateral hindpaws received single doses of one of four clinically available drugs that represent four distinct pharmacological classes, viz gabapentin, amitriptyline, meloxicam and morphine, according to a 'washout' protocol with at least 48 hours between successive doses. Gabapentin evoked dose-dependent anti-allodynia as did morphine whereas amitriptyline and meloxicam were inactive. Our findings are aligned with clinical data showing that gabapentin and morphine alleviated OA pain in the knee. The lack of efficacy of amitriptyline is consistent with the loss of descending diffuse noxious inhibitory controls reported by others in this model.

Therapeutic Attributes of Endocannabinoid System against Neuro-Inflammatory Autoimmune Disorders

In humans, various sites like cannabinoid receptors (CBR) having a binding affinity with cannabinoids are distributed on the surface of different cell types, where endocannabinoids (ECs) and derivatives of fatty acid can bind. The binding of these substance(s) triggers the activation of specific receptors required for various physiological functions, including pain sensation, memory, and appetite. The ECs and CBR perform multiple functions via the cannabinoid receptor 1 (CB1); cannabinoid receptor 2 (CB2), having a key effect in restraining neurotransmitters and the arrangement of cytokines. The role of cannabinoids in the immune system is illustrated because of their immunosuppressive characteristics. These characteristics include inhibition of leucocyte proliferation, T cells apoptosis, and induction of macrophages along with reduced pro-inflammatory cytokines secretion. The review seeks to discuss the functional relationship between the endocannabinoid system (ECS) and anti-tumor characteristics of cannabinoids in various cancers. The therapeutic potential of cannabinoids for cancer-both in vivo and in vitro clinical trials-has also been highlighted and reported to be effective in mice models in arthritis for the inflammation reduction, neuropathic pain, positive effect in multiple sclerosis and type-1 diabetes mellitus, and found beneficial for treating in various cancers. In human models, such studies are limited; thereby, further research is indispensable in this field to get a conclusive outcome. Therefore, in autoimmune disorders, therapeutic cannabinoids can serve as promising immunosuppressive and anti-fibrotic agents.

Chondroprotection and Molecular Mechanism of Action of Phytonutraceuticals on Osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease and an important cause of incapacitation. There is a lack of drugs and effective treatments that stop or slow the OA progression. Modern pharmacological treatments, such as analgesics, have analgesic effects but do not affect the course of OA. Long-term use of these drugs can lead to serious side effects. Given the OA nature, it is likely that lifelong treatment will be required to stop or slow its progression. Therefore, there is an urgent need for disease-modifying OA treatments that are also safe for clinical use over long periods. Phytonutraceuticals are herbal products that provide a therapeutic effect, including disease prevention, which not only have favorable safety characteristics but may have an alleviating effect on the OA and its symptoms. An estimated 47% of OA patients use alternative drugs, including phytonutraceuticals. The review studies the efficacy and action mechanism of widely used phytonutraceuticals, analyzes the available experimental and clinical data on the effect of some phytonutraceuticals (phytoflavonoids, polyphenols, and bioflavonoids) on OA, and examines the known molecular effect and the possibility of their use for chondroprotection.

Effect of intra-articular dexmedetomidine on experimental osteoarthritis in rats

Pharmacological treatment of osteoarthritis is still inadequate due to the low efficacy of the drugs used. Dexmedetomidine via the intra-articular (i.a.) route might be an option for the treatment of osteoarthritis-associated pain. The present study assessed the analgesic and anti-inflammatory effects of dexmedetomidine administered via the i.a. route in different doses in an experimental model of rat knee osteoarthritis induced with monosodium iodoacetate. Rats were allocated to four groups with 24 animals in each group. The OA (osteoarthritis), DEX-1 (dexmedetomidine in dose of 1μg/kg) and DEX-3 (dexmedetomidine in dose of 3μg/kg) groups were subjected to induction of osteoarthritis through injection of monosodium iodoacetate (MIA) via the i.a. route on the right knee; the control group was not subjected to osteoarthritis induction. Clinical assessment was performed on day 0 (before osteoarthritis induction) and then on days 5, 10, 14, 21 and 28 after induction. Treatment was performed on day 7 via the i.a. route, consisting of dexmedetomidine in doses of 1 and 3 μg/kg, while group OA received 0.9% normal saline. The animals were euthanized on days 7, 14, 21 and 28. Samples of the synovial membrane were collected for histopathological analysis, and the popliteal lymph nodes were collected for measurement of cytokines (interleukin [IL] IL-6, tumor necrosis factor alpha [TNF-α]). Dexmedetomidine (1 and 3 μg/kg) significantly reduced the animals’ weight distribution deficit during the chronic-degenerative stage of osteoarthritis and improved the pain threshold throughout the entire experiment. Histological analysis showed that dexmedetomidine did not cause any additional damage to the synovial membrane. The TNF-α levels decreased significantly in the DEX-3 group on day 28 compared with the OA group. Dexmedetomidine reduced pain, as evidenced by clinical parameters of osteoarthritis in rats, but did not have an anti-inflammatory effect on histological evaluation.

Early-stage knee OA induced by MIA and MMT compared in the murine model via histological and topographical approaches

Osteoarthritis (OA) is a common degenerative disease whose early management includes promising mechanical treatments. New treatments are initially validated using an animal model in which OA is induced. The MMT (mechanical induction) and MIA (chemical induction) models of OA induction are widespread, but their use to generate early OA is poorly documented. We analyzed and compared early-stage knee OA-induction via these two methods in 16 rats divided into two groups. After 4 weeks of induction, the knees were sampled and studied using both histology (Toluidine Blue and Sirius Red) and surface topology, an innovative technique for characterizing osteoarthritic cartilage. The Mankin-modified score confirms that the two OA-induction models evolved at the same speed. At this early stage, the two models can be differentiated morphologically, although no significant differences were revealed by either cellularity or birefringence analysis. However, the topological analysis generated two forms of quantitative data, the deformation ratio and the cohesion index, that differentiated between the two groups. Thus, the early-stage OA induced by these two models is revealed to differ. The patterns of cartilage damage induced point to MMT as the better choice to assess mechanical approaches to clinical OA treatment.

Amniotic Suspension Allograft Modulates Inflammation in a Rat Pain Model of Osteoarthritis

Osteoarthritis (OA) affects over 301 million adults worldwide. Inflammation is a recognized component of the OA process; two potent pro-inflammatory cytokines involved in OA are interleukin-1β and tumor necrosis factor-α. Placental-derived tissues and fluids are known to contain anti-inflammatory and immunomodulatory cytokines and growth factors. The objective of this study was to evaluate the anti-inflammatory effects of amniotic suspension allograft (ASA) in an in vivo model of OA; we evaluated pain, function, and cytokine levels following ASA treatment in the rat monosodium iodoacetate (MIA) OA pain model. Rats were injected with 2 mg of MIA, which causes pain, cartilage degeneration, and inflammation, followed by treatment with saline, triamcinolone (positive control), or ASA 7 days following disease induction with MIA. Behavioral assays, including gait analysis, mechanical pain threshold, incapacitance, and swelling were evaluated, along with histology and serum and synovial fluid biomarkers. Treatment with ASA resulted in significant improvements in pain threshold, while weight bearing aversion and swelling were significantly decreased. There were no differences between groups in total joint score after histological grading. Serum biomarkers did not show differences, indicating a lack of systemic response; however, synovial fluid levels of IL-10 were significantly increased in animals treated with ASA. ASA treatment significantly reduced pain, weight-bearing aversion and swelling. This study provides mechanistic data regarding potential therapeutic effects of ASA in OA and preliminary evidence of the anti-inflammatory nature of ASA. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1141-1149, 2020.

Combatting joint pain and inflammation by dual inhibition of monoacylglycerol lipase and cyclooxygenase-2 in a rat model of osteoarthritis

BACKGROUND

Endocannabinoids are showing great promise as effective mediators for controlling joint inflammation and pain. One strategy that could be harnessed to promote endogenous cannabinoid function is to inhibit the enzymatic break down of endocannabinoids locally in the joint. KML29 is an inhibitor of monoacylglycerol lipase (MAGL) activity which has been shown to promote increased 2-arachodonylglycerol (2-AG) levels in the circulation and in peripheral tissues. It is also known that 2-AG can be metabolised via the cyclo-oxygenase-2 (COX-2) pathway leading to the production of pro-inflammatory prostaglandins, which may counteract the effects of 2-AG. Therefore, this study examined the effect of KML29 alone as well as in combination with low-dose celecoxib (CXB) on joint pain and inflammation in the monoiodoacetate (MIA) model of osteoarthritis (OA) pain.

METHODS

Injection of MIA (3 mg) into the knee joints of male Wistar rats was used to model OA pain, inflammation, and nerve damage. Pain behaviour was assessed by von Frey hair algesiometry, and inflammation was evaluated using intravital microscopy to measure leukocyte trafficking in the synovial microvasculature.

RESULTS

Intra-articular injection of MIA produced mechanical hypersensitivity as measured by von Frey hair algesiometry. Local injection of KML29 (700 μg) reduced joint pain at day 14 post-MIA induction, and this analgesic effect was blocked by the cannabinoid receptor antagonists AM281 and AM630 (P < 0.0001; n = 6). During the acute inflammatory phase of the MIA model (day 1), a significant reduction in withdrawal threshold (P < 0.0001; n = 6-8) and leukocyte trafficking was seen after treatment with KML29 + CXB (P < 0.0001; n = 6-8). Early treatment of MIA-injected knees (days 1-3) with KML29 + CXB ameliorated the development of mechanical secondary allodynia (P < 0.0001; n = 8) in the later stages of the MIA model.

CONCLUSIONS

Combination therapy of KML29 plus CXB reduced joint pain and inflammation. Thus, dual inhibition of MAGL and cyclooxygenase-2 pathways could be a useful approach to alleviate joint inflammation and pain in OA joints.

Monosodium iodoacetate-induced monoarthritis develops differently in knee versus ankle joint in rats

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Ankle versus knee joint injection of MIA in rats resulted in different behavioural profiles.

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Levels of biochemical mediators differs between ankle and knee injection of MIA in rats.

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Histopathological analysis show different results after ankle versus knee injection of MIA in rats.

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The rat results mirror what has been found in human patients with osteoarthritis.

Objective

Disability and movement-related pain are major symptoms of joint disease, motivating the development of methods to quantify motor behaviour in rodent joint pain models. We compared effects on behaviour, assessed the levels of biochemical mediators and made a detailed histopathological evaluation after induction of rat monoiodoacetate (MIA) monoarthritis into the ankle or knee joint.

Design

Twenty-seven male Lewis rats were used. Before and up to 28 days after induction, they were tested for weight bearing during walking (dynamic), and standing (static), and for mechanical sensitivity. At termination synovial fluid was taken from ankle and/or knee joints for analysis of monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), macrophage inflammatory protein 3 alpha (MIP-3α), keratinocyte chemoattractant (KC)/human growth-regulated oncogene (GRO) and L(+)-lactate, and from separate rats joints were collected for histopathological assessment.

Results

MIA ankle joint injection gave a marked reduction of dynamic weight bearing during the first days, not seen in rats with knee joint injection. At three weeks, it was decreased in the group with knee injection, but not in those with ankle injection. However, the different injection sites caused similar reductions in static weight bearing during the early phase, which was normalized in the group with ankle injection but continued and was strengthened with time in the knee injected group. Histopathological assessment, biochemical mediators and joint swelling confirmed the disparate profiles.

Conclusions

This work shows that ankle versus knee joint injection of MIA resulted in different profiles in rats, which may mirror what has been found in human patients with osteoarthritis.

Anti-inflammatory role of TPCA-1 encapsulated nanosomes in porcine chondrocytes against TNF-α stimulation

In this study, we evaluated the hypothesis that immunonanosomes carrying the drug [5-(p-Fluorophenyl)-2-ureido]thiophene-3-carboxamide (TPCA-1) will help in reducing nuclear factor-kappaB (NF-κB)-associated inflammation in porcine chondrocytes against tumor necrosis factor-alpha (TNF-α)-induced stress. The nanosomes were tagged with monoclonal anti-type II collagen (MabCII) antibody to specifically target the exposed type II collagen in cartilage matrix. TPCA-1 at a concentration of 10 µM significantly reduced expression of the matrix-degrading enzyme, Matrix metalloproteinase-13 (MMP-13) and blocked the p65 nuclear translocation. In comparison to the TPCA-1 solution alone, the TPCA-1 nanosomes were found to be more effective in reducing the cellular toxicity, oxidative stress and inflammation in chondrocytes treated with TNF-α. In addition, TPCA-1 nanosomes were more effective in reducing the gene expression of hypoxia-inducible factor-2alpha (HIF-2α) that in turn is associated with the regulation of MMP-13 gene. TPCA-1 nanosomes significantly reduced expression of both these genes. The data also showed that TPCA-1 did not attenuate the down-regulated gene expression levels of anabolic genes aggrecan (ACAN) and collagen type II alpha (COL2A1). In conclusion, this study showed that TPCA-1 nanosomes carrying a dose of 10 µM TPCA-1 can effectively increase the survival of cultured porcine chondrocytes against TNF-α-induced stress. The findings of this study could be used to develop nanosome-based drug delivery systems (DDSs) for animal model of OA. Moreover, the approach presented here can be further utilized in other studies for targeted delivery of the drug of interest at a cellular level.

Cartilage regeneration and ageing: Targeting cellular plasticity in osteoarthritis

Ageing processes play a major contributing role for the development of Osteoarthritis (OA). This prototypic degenerative condition of ageing is the most common form of arthritis and is accompanied by a general decline, chronic pain and mobility deficits. The disease is primarily characterized by articular cartilage degradation, followed by subchondral bone thickening, osteophyte formation, synovial inflammation and joint degeneration. In the early stages, osteoarthritic chondrocytes undergo phenotypic changes that increase cell proliferation and cluster formation and enhance the production of matrix-remodelling enzymes. In fact, chondrocytes exhibit differentiation plasticity and undergo phenotypic changes during the healing process. Current studies are focusing on unravelling whether OA is a consequence of an abnormal wound healing response. Recent investigations suggest that alterations in different proteins, such as TGF-ß/BMPs, NF-Kß, Wnt, and Cx43, or SASP factors involved in signalling pathways in wound healing response, could be directly implicated in the initiation of OA. Several findings suggest that osteoarthritic chondrocytes remain in an immature state expressing stemness-associated cell surface markers. In fact, the efficacy of new disease-modifying OA drugs that promote chondrogenic differentiation in animal models indicates that this may be a drug-sensible state. In this review, we highlight the current knowledge regarding cellular plasticity in chondrocytes and OA. A better comprehension of the mechanisms involved in these processes may enable us to understand the molecular pathways that promote abnormal repair and cartilage degradation in OA. This understanding would be advantageous in identifying novel targets and designing therapies to promote effective cartilage repair and successful joint ageing by preventing functional limitations and disability.

Involvement of neutrophils and interleukin-18 in nociception in a mouse model of muscle pain

Muscle pain is a common condition that relates to various pathologies. Muscle overuse induces muscle pain, and neutrophils are key players in pain production. Neutrophils also play a central role in chronic pain by secreting interleukin (IL)-18. The aim of this study was to investigate the involvement of neutrophils and IL-18 in a mouse model of muscle pain. The right hind leg muscles of BALB/c mice were stimulated electrically to induce excessive muscle contraction. The left hind leg muscles were not stimulated. The pressure pain threshold, number of neutrophils, and IL-18 levels were investigated. Furthermore, the effects of the IL-18-binding protein and Brilliant Blue G on pain were investigated. In stimulated muscles, pressure pain thresholds decreased, and neutrophil and IL-18 levels increased compared with that in non-stimulated muscles. The administration of IL-18-binding protein and Brilliant Blue G attenuated hyperalgesia caused by excessive muscle contraction. These results suggest that increased IL-18 secretion from larger numbers of neutrophils elicits mechanical hyperalgesia.

Heat-Induced Limb Length Asymmetry Has Functional Impact on Weight Bearing in Mouse Hindlimbs

Limb length inequality results from many types of musculoskeletal disorders. Asymmetric weight bearing from a limb length discrepancy of less than 2% can have debilitating consequences such as back problems and early-onset osteoarthritis. Existing treatments include invasive surgeries and/or drug regimens that are often only partially effective. As a noninvasive alternative, we previously developed a once daily limb-heating model using targeted heat on one side of the body for 2 weeks to unilaterally increase bone length by up to 1.5% in growing mice. In this study, we applied heat for 1 week to determine whether these small differences in limb length are functionally significant, assessed by changes in hindlimb weight bearing. We tested the hypothesis that heat-induced limb length asymmetry has a functional impact on weight bearing in mouse hindlimbs. Female 3-week-old C57BL/6 mice (N = 12 total) were treated with targeted intermittent heat for 7 days (40 C for 40 min/day). High-resolution x-ray (N = 6) and hindlimb weight bearing data (N = 8) were acquired at the start and end of the experiments. There were no significant left-right differences in starting tibial length or hindlimb weight bearing. After 1-week heat exposure, tibiae (t = 7.7, p < 0.001) and femora (t = 11.5, p < 0.001) were ~1 and 1.4% longer, respectively, on the heat-treated sides (40 C) compared to the non-treated contralateral sides (30 C). Tibial elongation rate was over 6% greater (t = 5.19, p < 0.001). Hindlimb weight bearing was nearly 20% greater (t = 11.9, p < 0.001) and significantly correlated with the increase in tibial elongation rate on the heat-treated side (R² = 0.82, p < 0.01). These results support the hypothesis that even a small limb length discrepancy can cause imbalanced weight distribution in healthy mice. The increase in bone elongation rate generated by localized heat could be a way to equalize limb length and weight bearing asymmetry caused by disease or trauma, leading to new approaches with better outcomes by using heat to lengthen limbs and reduce costly side effects of more invasive interventions.

Human blood-based anti-inflammatory solution inhibits osteoarthritis progression in a meniscal-tear rat study

Current osteoarthritis (OA) research searches for treatments that modify the course of disease progression. Autologous Protein Solution (APS) is derived from whole blood and is a unique autologous therapy that contains high concentrations of white blood cells, platelets, and concentrated plasma, providing cytokines that can target the underlying mechanisms of disease progression. The APS Kit is currently under investigation for clinical use in the USA (NCT02262364). The aim of this study was to determine if APS has disease-modifying properties in the well-characterized rat meniscal tear-induced model of OA. Thirty male athymic rats underwent surgery to induce OA by a complete tear of the medial meniscus of the right knee. Seven days later, rats were administered 50 μl intra-articular (IA) APS from a human donor or phosphate buffered saline (PBS) control. Rats were euthanized 3 weeks following treatment and knee joints were processed for histological analysis. Collagen and cartilage degeneration were decreased by APS treatment, resulting in a significantly improved total joint score in APS-treated rats compared to those treated with the PBS control. No significant variations in gait analysis, weight gain, osteophyte score, or synovitis score were observed between APS- and PBS-treated animals. There were no adverse effects of APS reported in the study. Treatment with a single IA injection of APS reduced the cartilage degeneration that characterizes the progression of OA. Further studies are necessary to determine if APS can modify OA disease progression in humans. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2260-2268, 2017.

A novel composite formulation of palmitoylethanolamide and quercetin decreases inflammation and relieves pain in inflammatory and osteoarthritic pain models

BACKGROUND

Osteoarthritis (OA) is a common progressive joint disease in dogs and cats. The goal of OA treatment is to reduce inflammation, minimize pain, and maintain joint function. Currently, non-steroidal anti-inflammatory drugs (e.g., meloxicam) are the cornerstone of treatment for OA pain, but side effects with long-term use pose important challenges to veterinary practitioners when dealing with OA pain. Palmitoylethanolamide (PEA) is a naturally-occurring fatty acid amide, locally produced on demand by tissues in response to stress. PEA endogenous levels change during inflammatory and painful conditions, including OA, i.e., they are typically increased during acute conditions and decreased in chronic inflammation. Systemic treatment with PEA has anti-inflammatory and pain-relieving effects in several disorders, yet data are lacking in OA. Here we tested a new composite, i.e., PEA co-ultramicronized with the natural antioxidant quercetin (PEA-Q), administered orally in two different rat models of inflammatory and OA pain, namely carrageenan paw oedema and sodium monoiodoacetate (MIA)-induced OA. Oral treatment with meloxicam was used as benchmark.

RESULTS

PEA-Q decreased inflammatory and hyperalgesic responses induced by carrageenan injection, as shown by: (i) paw oedema reduction, (ii) decreased severity in histological inflammatory score, (iii) reduced activity of myeloperoxidase, i.e., a marker of inflammatory cell infiltration, and (iv) decreased thermal hyperalgesia. Overall PEA-Q showed superior effects compared to meloxicam. In MIA-treated animals, PEA-Q exerted the following effects: (i) reduced mechanical allodynia and improved locomotor function, (ii) protected cartilage against MIA-induced histological damage, and (iii) counteracted the increased serum concentration of tumor necrosis factor alpha, interleukin 1 beta, metalloproteases 1, 3, 9 and nerve growth factor. The magnitude of these effects was comparable to, or even greater than, those of meloxicam.

CONCLUSION

The present findings shed new light on some of the inflammatory and nociceptive pathways and mediators targeted by PEA-Q and confirm its anti-inflammatory and pain-relieving effects in rodent OA pain models. The translatability of these observations to canine and feline OA pain is currently under investigation.

Reflections about Osteoarthritis and Curcuma longa

Osteoarthritis (OA) is a chronic inflammatory degenerative process that affects joints such as the hands, hips, shoulders, feet, spine, and especially knees in millions of people worldwide. Some authors have shown that Curcuma longa components may exhibit benefic effects in the treatment of degenerative diseases as OA. This plant belongs to the family Zingiberaceae and it is popularly known as turmeric or saffron. This review intended to perform a retrospective search to identify studies involving humans and animal models. This review was based on articles linking OA and C. longa. Databases as Medline, Science Direct, and Lilacs were consulted and a retrospective search was carried out in order to identify studies involving humans and animal models. The curcuminoids from C. longa exhibit actions at different locations in the pathogenesis of OA once it may play an important role as anti-inflammatory, down-regulating enzymes as phospholipase A2, cyclooxygenase-2, and lipoxygenases, and reducing tumor necrosis factor-alpha-and interleukins such as interleukin-1β (IL-1β), IL-6, and IL-8. They also act as inducer of apoptosis in synoviocytes, decreasing the inflammation process and may also reduce the synthesis of reactive oxygen species. For these reasons, new pharmaceutical technology and pharmacological studies should be proposed to determine the dose, the best delivery vehicle, pharmaceutical formulation and route of administration of this plant so its use as an adjunct in the treatment of OA may become a reality in clinical practice.

The spice for joint inflammation: anti-inflammatory role of curcumin in treating osteoarthritis

Osteoarthritis is a degenerative disease of the joint affecting aging populations worldwide. It has an underlying inflammatory cause, which contributes to the loss of chondrocytes, leading to diminished cartilage layer at the affected joints. Compounds with anti-inflammatory properties are potential treatment agents for osteoarthritis. Curcumin derived from Curcuma species is an anti-inflammatory compound as such. This review aims to summarize the antiosteoarthritic effects of curcumin derived from clinical and preclinical studies. Many clinical trials have been conducted to determine the effectiveness of curcumin in osteoarthritic patients. Extracts of Curcuma species, curcuminoids and enhanced curcumin, were used in these studies. Patients with osteoarthritis showed improvement in pain, physical function, and quality of life after taking curcumin. They also reported reduced concomitant usage of analgesics and side effects during treatment. In vitro studies demonstrated that curcumin could prevent the apoptosis of chondrocytes, suppress the release of proteoglycans and metal metalloproteases and expression of cyclooxygenase, prostaglandin E-2, and inflammatory cytokines in chondrocytes. These were achieved by blocking the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) system in the chondrocytes, by preventing the activation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha, phosphorylation, and translocation of the p65 subunit of NF-κB complexes into the nucleus. In conclusion, curcumin is a potential candidate for the treatment of osteoarthritis. More well-planned randomized control trials and enhanced curcumin formulation are required to justify the use of curcumin in treating osteoarthritis.