Induction of osteoarthritis in the rat by surgical tear of the meniscus: Inhibition of joint damage by a matrix metalloproteinase inhibitor

METTL14 promotes chondrocyte ferroptosis in osteoarthritis via m6A modification of GPX4

BACKGROUND

Ferroptosis is caused by iron-dependent peroxidation of membrane phospholipids and chondrocyte ferroptosis contributes to osteoarthritis (OA) progression. Glutathione peroxidase 4 (GPX4) plays a master role in blocking ferroptosis. N6-methyladenosine (m6A) is an epigenetic modification among mRNA post-transcriptional modifications. This study investigated the effect of methyltransferase-like 14 (METTL14), the key component of the m6A methyltransferase, on chondrocyte ferroptosis via m6A modification.

METHODS

An OA rat model was established through an intra-articular injection of monosodium iodoacetate in the right knee. OA cartilages in rat models were used for gene expression analysis. Primary mouse chondrocytes or ADTC5 cells were stimulated with IL-1β or erastin. The m6A RNA methylation quantification kit was used to measure m6A level. The effect of METTL14 and GPX4 on ECM degradation and ferroptosis was investigated through western blotting, fluorescence immunostaining, propidium iodide staining, and commercially available kits. The mechanism of METTL14 action was explored through MeRIP-qPCR assays.

RESULTS

METTL14 and m6A expression was upregulated in osteoarthritic cartilages and IL-1β-induced chondrocytes. METTL14 depletion repressed the IL-1β or erastin-stimulated ECM degradation and ferroptosis in mouse chondrocytes. METTL14 inhibited GPX4 gene through m6A methylation modification. GPX4 knockdown reversed the si-METTL14-mediated protection in IL-1β-induced chondrocytes.

CONCLUSION

METTL14 depletion inhibits ferroptosis and ECM degradation by suppressing GPX4 mRNA m6A modification in injured chondrocytes.

The dual amylin and calcitonin receptor agonist KBP-336 elicits a unique combination of weight loss, antinociception and bone protection - a novel disease-modifying osteoarthritis drug

BACKGROUND

Despite the extensive research to provide a disease-modifying osteoarthritis drug (DMOAD), there is still no approved DMOAD. Dual amylin and calcitonin receptor agonists (DACRA) can provide metabolic benefits along with antinociceptive and potential structural preserving effects. In these studies, we tested a DACRA named KBP-336 on a metabolic model of OA in meniscectomised (MNX) rats.

METHODS

We evaluated KBP-336's effect on pain-like symptoms in Sprague Dawley (SD) rats on high-fat diet (HFD) that underwent meniscectomy using the von Frey test to measure the 50% paw withdrawal threshold (PWT) and analyzed using one-way ANOVA. Short in vivo studies and in vitro cell receptor expression systems were used to illustrate receptor pharmacology.

RESULTS

After 30 weeks on HFD, including an 8-week treatment, female MNX animals receiving KBP-336 4.5 nmol/Kg/72 h had lower body weight and smaller adipose tissues than their vehicle-treated counterparts. After 20 weeks on HFD, including an 8-week treatment, male rats receiving KBP-336 had lower body weight than the vehicle group. In both the female and male rats, the MNX groups on KBP-336 treatment had a higher PWT than the vehicle-treated MNX group. Aiming to identify the receptor influencing pain alleviation, KBP-336 was compared to the long-acting human calcitonin (hCTA). Single-dose studies on 12-week-old male rats showed that hCTA lowers CTX-I without affecting food intake, confirming its calcitonin receptor selectivity. On the metabolic OA model with 18 weeks of HFD, including 6-week treatment, hCTA at 100 nmol/Kg/24 h and KBP-336 at 0.5, 1.5, and 4.5 nmol/Kg/72 h produced significantly higher PWT in MNX animals compared to MNX animals on vehicle treatment. hCTA and KBP-336 at 0.5 nmol/Kg did not affect body weight and fat tissues.

CONCLUSION

Overall, KBP-336 improved the pain observed in the metabolic OA model. Calcitonin receptor activation proved to be essential in this antinociceptive effect.

Effect of amniotic suspension allograft in a rat destabilization of medial meniscus osteoarthritis model

Placental-derived allografts have been of interest as a potential nonsurgical treatment to reduce pain and improve function in knee osteoarthritis (OA). The purpose of this study was to evaluate the effect of single and repeat injection of amniotic suspension allograft (ASA) on pain, function, and cytokine levels using a destabilization of the medial meniscus (DMM) rat model of OA. Post-DMM surgery, animals were treated with a single injection of either ASA, vehicle, or triamcinolone, or repeated injection of either ASA or vehicle. Behavioral testing including knee swelling, pain threshold, dynamic weight bearing (DWB), and gait analysis were evaluated during the in-life phase. Postsacrifice, histopathology and serum and synovial fluid analyses were evaluated. Significant improvements in both DWB differentials and pain threshold were seen in response to repeated injection of ASA, while a single injection of ASA and triamcinolone resulted in significant improvements in pain threshold. Histopathology analysis found no significant differences regardless of treatment compared to vehicle, except for an increase in synovitis following repeated injection of ASA. A single injection of ASA and triamcinolone resulted in increased anti-inflammatory cytokines; repeated ASA injection resulted in significant increases in several immune-modulating factors relevant to OA. When comparing the impact of single and repeat ASA treatments on behavioral testing, repeated injection provided significant additional improvements in both pain and function. This study provides evidence demonstrating the impact of a second injection while also providing additional data for evaluating the use of ASA as a nonsurgical treatment for knee OA.

Enlarged colony housing promotes linear progression of subchondral bone remodeling in joint instability rat models

Objective: Osteoarthritis (OA) is a disease with high prevalence and an unmet medical need for disease modifying treatments. In rat models, OA-like subchondral bone and cartilage changes can be induced by instability surgery with different severity levels. Factors which determine structural changes additionally comprise the study duration and activity-impacted joint loading. Methods: A medial meniscal tear (MMT) or anterior cruciate ligament transection with partial meniscectomy (ACLT+pMx) was induced unilaterally in rats housed in a rat colony cage (RCC), allowing high activity levels including jumping and stair climbing. In parallel, ACLT+pMx rats were housed in Type IV cages. The time course of OA-related changes was investigated at 4, 8, 12, and 16 weeks after surgery by micro-CT, gait analysis and joint diameter measurements. Results: Gait disturbance was observed after 2 weeks and to a similar extend in all models. The increase in ipsilateral joint diameters peaked after 2 weeks and were more pronounced after ACLT+pMx compared to MMT-surgery, but independent of housing. Micro-CT analysis revealed that increases in osseous tibial width were most distinct after ACLT+pMx in RCC and progressed continuously until week sixteen. In contrast, osseous tibial width of ipsilateral joints in MMT RCC and ACLT+pMx Type IV groups did not increase further after week twelve. In contralateral joints, this parameter was not affected, regardless of the model or caging. However, a significant increase in bone volume fraction and trabecular thickness was observed over time in the femur and tibia of both ipsilateral and contralateral knees. Here, the medial tibial compartment of the operated joint was most affected and linear changes were most pronounced in the ACLT+pMx RCC group. Conclusion: Increased movement of animals in colony cages leads to robust structural changes in subchondral bone after surgically induced joint instability over time, while in regular Type IV housing maximal changes are reached in week twelve. The new insights into the differentiation of the models, particularly with respect to the linear progression of bone changes in ACLT+pMx in the RCC, may be useful for the design of chronic OA-studies within a longer lifespan and therefore supporting the development of novel therapies.

Inhibition of Brd4 alleviates osteoarthritis pain via suppression of neuroinflammation and activation of Nrf2-mediated antioxidant signalling

BACKGROUND AND PURPOSE

Osteoarthritis (OA) pain remains a major clinical problem. It is urgent to identify novel therapeutic approaches for OA pain states. Bromodomain and extra-terminal (BET) protein inhibitors have robust anti-inflammatory effects in several pain models. However, the underlying mechanisms of these inhibitors in OA pain have not been determined. We, therefore, investigated the effects and the underlying mechanism(s) of BET inhibition on pain-related behaviours in a rat model of OA.

EXPERIMENTAL APPROACH

The OA model was established by intra-articular injection of monosodium iodoacetate (MIA) in rat knees. Pain behaviours were assessed in rats by hindlimb weight-bearing asymmetry, mechanical allodynia and thermal hyperalgesia. Possible mechanisms underlying BET inhibition were explored in the MIA-induced OA pain model in the spinal cord and dorsal root ganglia (DRG).

KEY RESULTS

Inhibiting bromodomain-containing protein 4 (Brd4) with either JQ1 or MS417, or using AAV2/9-shRNA-Brd4-EGFP-mediated knockdown of Brd4 genes, significantly attenuated MIA-induced pain behaviours. Brd4 inhibition suppressed NF-κB and NF-κB-mediated inflammatory cytokines in both the spinal cord and DRG in rats with MIA-induced OA pain. Brd4 inhibition also attenuated the oxidative stress and promoted nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent antioxidant genes in both the spinal cord and DRG in our odel of MIA-induced OA pain.

CONCLUSIONS AND IMPLICATIONS

In conclusion, Brd4 inhibition alleviated MIA-induced OA pain in rats, via suppression of neuroinflammation and activation of Nrf2-mediated antioxidant signalling. Although our model does not perfectly represent how OA develops in humans, inhibition of Brd4 may provide novel insights into possible treatments for OA pain.

Development of a Novel Rat Knee Osteoarthritis Model Induced by Medial Meniscus Extrusion

OBJECTIVE

The medial meniscus extrusion (MME) is associated with increased stress on the knee joint, which leads to cartilage degeneration. To evaluate the etiology of knee osteoarthritis, it is extremely important to create animal models of the disease that more closely resemble actual clinical conditions in terms of symptomatology, molecular biology, and histology. This study aimed to create a clinically relevant model of MME in rats.

DESIGN

Behavioral, molecular biological, and histological changes in the newly developed rat MME model were compared with those in sham and medial meniscus transection and medial collateral ligament transection (MMT) models to examine the characteristics of this model.

RESULTS

In the MME rat model, behavioral evaluation shows abnormalities in gait compared with the other 2 groups, and molecular biological evaluation of the infrapatellar synovia of rats shows that gene expression of inflammatory cytokines, matrix-degrading enzymes, and pain-related nerve growth factor was increased compared with the sham group. Furthermore, histological evaluation reveals that cartilage degeneration was the most severe in the MME group.

CONCLUSIONS

The newly developed MME model reproduced the characteristic pathology of MME in clinical practice, such as severe pain, inflammation, and rapid progression of osteoarthritis. The MME model, which might more closely mimic human knee osteoarthritis (OA), could be a useful model for elucidating the pathophysiology and considering therapeutic management for knee OA.

Identification and validation of FPR1, FPR2, IL17RA and TLR7 as immunogenic cell death related genes in osteoarthritis

Immunogenic cell death (ICDs) has gained increasing attention for its significant clinical efficacy in various diseases. Similarly, more and more attention has been paid in the role of immune factors in the pathological process of osteoarthritis (OA). The objective of this study is to reveal the relationship between ICD-related genes and the process of OA at the gene level through bioinformatics analysis. In this study, Limma R package was applied to identify differentially expressed genes (DEG), and OA related module genes were determined by weighted gene co-expression network analysis. The ICD-related genes were extracted from a previous study. The module genes related to DEGs and ICD were overlapped. Then, hub genes were identified by a series of analyses using the Least absolute shrinkage and selection operator and random forest algorithm, the expression level and diagnostic value of hub genes were evaluated by Logistic regression. In addition, we used Spearman rank correlation analysis to clarify the relationship between hub genes and infiltrating immune cells and immune pathways. The expression levels of FPR1, FPR2, IL17RA, and TLR7 was verified in SD rat knee joint model of OA by immunohistochemistry. The expression levels of FPR1, FPR2, IL17RA, and TLR7 mRNA were detected in the IL-1β induced rat chondrocytes in qPCR experiment in vitro. Four hub genes (FPR1, FPR2, IL17RA, and TLR7) were ultimately identified as OA biomarkers associated with ICD. And knockdown of TLR7 reversed collagen II and ADAMTS-5 degradation in IL-1β-stimulated chondrocytes. This research may provide new immune related biomarkers for the diagnosis of OA and serve as a reference for disease treatment monitoring.

Intra-articular delivery of an indoleamine 2,3-dioxygenase galectin-3 fusion protein for osteoarthritis treatment in male Lewis rats

OBJECTIVE

Osteoarthritis (OA) is driven by low-grade inflammation, and controlling local inflammation may offer symptomatic relief. Here, we developed an indoleamine 2,3-dioxygenase and galectin-3 fusion protein (IDO-Gal3), where IDO increases the production of local anti-inflammatory metabolites and Gal3 binds carbohydrates to extend IDO's joint residence time. In this study, we evaluated IDO-Gal3's ability to alter OA-associated inflammation and pain-related behaviors in a rat model of established knee OA.

METHODS

Joint residence was first evaluated with an analog Gal3 fusion protein (NanoLuc™ and Gal3, NL-Gal3) that produces luminescence from furimazine. OA was induced in male Lewis rats via a medial collateral ligament and medial meniscus transection (MCLT + MMT). At 8 weeks, NL or NL-Gal3 were injected intra-articularly (n = 8 per group), and bioluminescence was tracked for 4 weeks. Next, IDO-Gal3s's ability to modulate OA pain and inflammation was assessed. Again, OA was induced via MCLT + MMT in male Lewis rats, with IDO-Gal3 or saline injected into OA-affected knees at 8 weeks post-surgery (n = 7 per group). Gait and tactile sensitivity were then assessed weekly. At 12 weeks, intra-articular levels of IL6, CCL2, and CTXII were assessed.

RESULTS

The Gal3 fusion increased joint residence in OA and contralateral knees (p < 0.0001). In OA-affected animals, both saline and IDO-Gal3 improved tactile sensitivity (p = 0.008), but IDO-Gal3 also increased walking velocities (p ≤ 0.033) and improved vertical ground reaction forces (p ≤ 0.04). Finally, IDO-Gal3 decreased intra-articular IL6 levels within the OA-affected joint (p = 0.0025).

CONCLUSION

Intra-articular IDO-Gal3 delivery provided long-term modulation of joint inflammation and pain-related behaviors in rats with established OA.

Intra-articular delivery of micronized dehydrated human amnion/chorion membrane reduces degenerative changes after onset of post-traumatic osteoarthritis

Background: Micronized dehydrated human amnion/chorion membrane (mdHACM) has reduced short term post-traumatic osteoarthritis (PTOA) progression in rats when delivered 24 h after medial meniscal transection (MMT) and is being investigated for clinical use as a disease modifying therapy. Much remains to be assessed, including its potential for longer-term therapeutic benefit and treatment effects after onset of joint degeneration. Objectives: Characterize longer-term effects of acute treatment with mdHACM and determine whether treatment administered to joints with established PTOA could slow or reverse degeneration. Hypotheses: Acute treatment effects will be sustained for 6 weeks, and delivery of mdHACM after onset of joint degeneration will attenuate structural osteoarthritic changes. Methods: Rats underwent MMT or sham surgery (left leg). mdHACM was delivered intra-articularly 24 h or 3 weeks post-surgery (n = 5-7 per group). Six weeks post-surgery, animals were euthanized and left tibiae scanned using equilibrium partitioning of an ionic contrast agent microcomputed tomography (EPIC-µCT) to structurally quantify joint degeneration. Histology was performed to examine tibial plateau cartilage. Results: Quantitative 3D µCT showed that cartilage structural metrics (thickness, X-ray attenuation, surface roughness, exposed bone area) for delayed mdHACM treatment limbs were significantly improved over saline treatment and not significantly different from shams. Subchondral bone mineral density and thickness for the delayed treatment group were significantly improved over acute treated, and subchondral bone thickness was not significantly different from sham. Marginal osteophyte degenerative changes were decreased with delayed mdHACM treatment compared to saline. Acute treatment (24 h post-surgery) did not reduce longer-term joint tissue degeneration compared to saline. Histology supported µCT findings and further revealed that while delayed treatment reduced cartilage damage, chondrocytes displayed qualitatively different morphologies and density compared to sham. Conclusion: This study provides insight into effects of intra-articular delivery timing relative to PTOA progression and the duration of therapeutic benefit of mdHACM. Results suggest that mdHACM injection into already osteoarthritic joints can improve joint health, but a single, acute mdHACM injection post-injury does not prevent long term osteoarthritis associated with meniscal instability. Further work is needed to fully characterize the durability of therapeutic benefit in stable osteoarthritic joints and the effects of repeated injections.

No Evidence for Cognitive Impairment in an Experimental Rat Model of Knee Osteoarthritis and Associated Chronic Pain

Although chronic pain states have been associated with impaired cognitive functions, including memory and cognitive flexibility, the cognitive effects of osteoarthritis (OA) pain remain to be clarified. The aim of this study was to measure cognitive function in the mono-iodoacetate (MIA) rat model of chronic OA-like knee pain. We used young adult male Lister hooded rats, which are well-suited for cognitive testing. Rats received either a unilateral knee injection of MIA (3 mg/50 µL) or saline as control. Joint pain at rest was assessed for up to 12 weeks, using weight-bearing asymmetry, and referred pain at a distal site, using determination of hindpaw withdrawal thresholds. The watermaze delayed-matching-to-place test of rapid place learning, novel object recognition memory assay, and an operant response-shift and -reversal task were used to measure memory and behavioral flexibility. Open-field locomotor activity, startle response, and prepulse inhibition were also measured for comparison. MIA-injected rats showed markedly reduced weight-bearing on the injured limb, as well as pronounced cartilage damage and synovitis, but interestingly no changes in paw withdrawal threshold. Rearing was reduced, but otherwise, locomotor activity was normal and no changes in startle and prepulse inhibition were detected. MIA-injected rats had intact watermaze delayed-matching-to-place performance, suggesting no substantial change in hippocampal function, and there were no changes in novel object recognition memory or performance on the operant task of behavioral flexibility. Our finding that OA-like pain does not alter hippocampal function, unlike other chronic pain conditions, is consistent with human neuroimaging findings. PERSPECTIVE: Young adult rats with OA-like knee pain showed no impairments in hippocampal memory function and behavioral flexibility, suggesting that OA pain impacts cognitive functions less than other chronic pain conditions. In patients, OA pain may interact with other factors (e.g., age, socio-economic factors, and medication) to impair cognition.

Total Knee Arthroplasty After Meniscectomy Is More Likely in Patients With Bicompartmental or Complex Tears

Purpose

To determine the relationship between meniscus tear morphologies, stratified by location and pattern, and knee arthroplasty rates in a commercial insurance population.

Methods

The PearlDiver database was queried for patients ≥35 years old with a meniscus tear of specified laterality and ≥2 years follow-up between 2015 and 2018. Two analyses were conducted with cohorts matched on age, sex, Charlson Comorbidity Index, obesity, osteoarthritis (OA), and treatment (meniscectomy vs conservative): one with equal-sized subgroups by tear location (medial only, lateral only, or both medial and lateral) and another by tear pattern (bucket-handle, complex, or peripheral). The rate of subsequent total knee arthroplasty (TKA) was compared between matched groups.

Results

In total, 129,987 patients (mean age: 57.8 ± 10.5 years) were matched by tear location; 1,734 patients with medial-only tears (4.0%), 1,786 with lateral-only tears (4.1%), and 2,611 with medial plus lateral tears (6.0%) underwent a TKA within 5 years (P < .001). Patients with both medial and lateral tears were 1.55-fold more likely to undergo TKA. In total, 24,213 patients (mean age: 56.0 ± 10.5 years) were matched by tear pattern; 296 patients with bucket-handle tears (3.7%), 373 with complex tears (4.6%), and 336 with peripheral tears (4.2%) underwent TKA (P = .01). Patients with complex tears were 1.29-fold more likely to undergo TKA than patients with bucket-handle tears (P = .002).

Conclusions

In matched cohorts of patients with degenerative meniscus tears, having both medial plus lateral tears conferred a 1.5-fold risk of TKA, whereas complex tears conferred a 1.3-fold risk within 5 years. Specific meniscal tear patterns and locations harbor varying risk in progressing to end-stage knee OA, and these data may help counsel patients about their likelihood of progressing to end-stage OA warranting an arthroplasty procedure.

Level of Evidence

Level III, retrospective comparative study.

Development of a cyclic-inverso AHSG/Fetuin A-based peptide for inhibition of calcification in osteoarthritis

OBJECTIVE

Ectopic calcification is an important contributor to chronic diseases, such as osteoarthritis. Currently, no effective therapies exist to counteract calcification. We developed peptides derived from the calcium binding domain of human Alpha-2-HS-Glycoprotein (AHSG/Fetuin A) to counteract calcification.

METHODS

A library of seven 30 amino acid (AA) long peptides, spanning the 118 AA Cystatin 1 domain of AHSG, were synthesized and evaluated in an in vitro calcium phosphate precipitation assay. The best performing peptide was modified (cyclic, retro-inverso and combinations thereof) and evaluated in cellular calcification models and the rat Medial Collateral Ligament Transection + Medial Meniscal Tear (MCLT + MMT) osteoarthritis model.

RESULTS

A cyclic peptide spanning AA 1-30 of mature AHSG showed clear inhibition of calcium phosphate precipitation in the nM-pM range that far exceeded the biological activity of the linear peptide variant or bovine Fetuin. Biochemical and electron microscopy analyses of calcium phosphate particles revealed a similar, but distinct, mode of action in comparison with bFetuin. A cyclic-inverso variant of the AHSG 1-30 peptide inhibited calcification of human articular chondrocytes, vascular smooth muscle cells and during osteogenic differentiation of bone marrow derived stromal cells. Lastly, we evaluated the effect of intra-articular injection of the cyclic-inverso AHSG 1-30 peptide in a rat osteoarthritis model. A significant improvement was found in histopathological osteoarthritis score and animal mobility. Serum levels of IFNγ were found to be lower in AHSG 1-30 peptide treated animals.

CONCLUSIONS

The cyclic-inverso AHSG 1-30 peptide directly inhibits the calcification process and holds the potential for future application in osteoarthritis.

Analgesic effects and arthritic changes following intra-articular injection of diclofenac etalhyaluronate in a rat knee osteoarthritis model

Background

Diclofenac etalhyaluronate (DF-HA) is a recently developed analgesic conjugate of diclofenac and hyaluronic acid that has analgesic and anti-inflammatory effects on acute arthritis. In this study, we investigated its analgesic effect on osteoarthritis, using a rat model of monoiodoacetate (MIA).

Methods

We injected MIA into the right knees of eight 6-weeks-old male Sprague–Dawley rats. Four weeks later, rats were randomly injected with DF-HA or vehicle into the right knee. Seven weeks after the MIA injection, fluorogold (FG) and sterile saline were injected into the right knees of all the rats. We assessed hyperalgesia with weekly von Frey tests for 8 weeks after MIA administration. We took the right knee computed tomography (CT) as radiographical evaluation every 2 weeks. All rats were sacrificed 8 weeks after administration of MIA for histological evaluation of the right knee and immunohistochemical evaluation of the DRG and spinal cord. We also evaluated the number of FG-labeled calcitonin gene-related peptide (CGRP)-immunoreactive(ir) neurons in the dorsal root ganglion (DRG) and ionized calcium-binding adapter molecule 1 (Iba1)-ir microglia in the spinal cord.

Results

Administration of DF-HA significantly improved pain sensitivity and reduced CGRP and Iba1 expression in the DRG and spinal cord, respectively. However, computed tomography and histological evaluation of the right knee showed similar levels of joint deformity, despite DF-HA administration.

Conclusion

DF-HA exerted analgesic effects on osteoarthritic pain, but did not affect joint deformity.

Pulsed Electromagnetic Field Enhances Healing of a Meniscal Tear and Mitigates Posttraumatic Osteoarthritis in a Rat Model

BACKGROUND

Meniscal tears in the avascular region are thought to rarely heal and are a considerable challenge to treat. Although the therapeutic effects of a pulsed electromagnetic field (PEMF) have been extensively studied in a variety of orthopaedic disorders, the effect of a PEMF on meniscal healing has not been reported.

HYPOTHESIS

PEMF treatment would promote meniscal healing and prevent osteoarthritis progression.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 72 twelve-week-old male Sprague-Dawley rats with full-thickness longitudinal medial meniscal tears in the avascular region were divided into 3 groups: control (G_con), treatment with a classic signal PEMF (G_classic), and treatment with a high-slew rate signal PEMF (G_HSR). Macroscopic observation and histological analysis of the meniscus and articular cartilage were performed to evaluate the meniscal healing and progression of osteoarthritis. The synovium was harvested for histological and immunofluorescent analysis to evaluate the intra-articular inflammation. Meniscal healing, articular cartilage degeneration, and synovitis were quantitatively evaluated according to their scoring systems.

RESULTS

Dramatic degenerative changes of the meniscus and articular cartilage were noticed during gross observation and histological evaluation in G_con at 8 weeks. However, the menisci in the 2 treatment groups were restored to normal morphology, with a smooth surface and shiny white color. Particularly, the HSR signal remarkably enhanced the fibrochondrogenesis and accelerated the remodeling process of the regenerated tissue. The meniscal healing scores of the PEMF treatment groups were significantly higher than those in G_con at 8 weeks. Specifically, the HSR signal showed a significantly higher meniscal repair score than did the classic signal at week 8 (P < .01). Additionally, the HSR signal significantly downregulated the secretion levels of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in the meniscus and synovium as compared with the control group. When compared with the 2 treatment groups, G_con had significantly higher degeneration scores (G_con vs G_classic, P < .0001; G_con vs G_HSR, P < .0001). The HSR signal also exhibited significantly lower synovitis scores compared with the other two groups (G_con vs G_classic, P < .0001; G_classic vs G_HSR, P = .0002).

CONCLUSION

A PEMF promoted the healing of meniscal tears in the avascular region and restored the injured meniscus to its structural integrity in a rat model. As compared with the classic signal, the HSR signal showed increased capability to promote fibrocartilaginous tissue formation and modulate the inflammatory environment, therefore protecting the knee joint from posttraumatic osteoarthritis development.

CLINICAL RELEVANCE

Adjuvant PEMF therapy may offer a new approach for the treatment of meniscal tears attributed to the enhanced meniscal repair and ameliorated osteoarthritis progression.

Analgesic effects and arthritic changes following tramadol administration in a rat hip osteoarthritis model

We investigated the analgesic effects of tramadol and the arthritic changes following tramadol administration in the rat hip osteoarthritis (OA) model using mono-iodoacetate (MIA). The right hip joints of male Sprague-Dawley rats (n = 5 rats/group) in the Sham group were injected with 25 μl of sterile saline and 1% of fluorogold (FG) retrograde neurotracer. In the MIA + Vehicle and MIA + Tramadol groups, FG and 25 μl of sterile saline with 0.5 mg of MIA were injected into the right hip joint. The MIA + Vehicle and MIA + Tramadol groups were administered daily for 4 weeks, either sterile saline (10 mg/kg, intraperitoneal [i.p.]) or tramadol (10 mg/kg, i.p.). We assessed hyperalgesia every week after MIA administration. Histopathological changes and immunoreactive neurons for calcitonin gene-related peptide (CGRP) in dorsal root ganglia (DRG) were evaluated after 4 weeks of treatment. MIA injection into the hip joint led to mechanical hyperalgesia (p < 0.01), which was significantly reduced by tramadol administration (p < 0.01). Furthermore, daily i.p injection of tramadol significantly suppressed CGRP expression in DRG (p < 0.0001). MIA + Vehicle and MIA + Tramadol groups showed significant cartilage reduction and degeneration compared to the Sham group (p < 0.0001). Interestingly, OA changes significantly progressed in the MIA + Tramadol group compared to the MIA + Vehicle group (p < 0.0001).

Rodent models of knee osteoarthritis for pain research

Osteoarthritis (OA) is a chronic degenerative joint disease and a leading cause of disability worldwide. Pain is the main symptom, yet no current treatment can halt disease progression or effectively provide symptomatic relief. Numerous animal models have been described for studying OA and some for the associated OA pain. This review aims to update on current models used for studying OA pain, focusing on mice and rats. These models include surgical, chemical, mechanical, and spontaneous OA models. The impact of sex and age will also be addressed in the context of OA modelling. Although no single animal model has been shown ideal for studying OA pain, increased efforts to phenotype OA will likely impact the choice of models for pre-clinical and basic research studies.

Measures of cardiovascular function suggest autonomic nervous system dysregulation after surgical induction of joint injury in the male Lewis rat

OBJECTIVES

Functional changes in the autonomic nervous system may help explain variability in the progression of knee osteoarthritis (OA). Thus, the objective of this study was to evaluate autonomic nervous system shifts, measured via heart rate response variables, in rat knee joint injury and OA models.

METHODS

Cardiovascular characteristics were measured at baseline and bi-weekly for 8 weeks after skin incision, medial collateral ligament transection (MCLT), or MCLT+medial meniscus transection (MCLT+MMT). Heart rate was also assessed during a mild stressor (elevated maze). At endpoint, cardiovascular responses to mechanical knee stimuli were evaluated, as well as responses to 1-phenylbiguanide, a 5HT_3A receptor agonist with reported ability to stimulate vagal responses.

RESULTS

During low activity, a slower heart rate occurred in MCLT (299 ± 10 bpm) and MCLT+MMT (310 ± 10 bpm) animals compared to controls (325 ± 10 bpm). Furthermore, patellar ligament mechanical stimuli produced an immediate decrease in heart rate and blood pressure in all groups. Finally, a larger drop in heart rate was observed in MCLT (252 ± 40 bpm) and MCLT+MMT (263 ± 49 bpm) following administration of 1-phenylbiguanide compared to skin incision (168 ± 45 bpm).

CONCLUSIONS

Acute mechanical stimulation of the patellar ligament produced drops in heart rate, suggesting a possible joint-brain connection that modulates autonomic responses. With both joint injury, cardiac vagal activation was altered in response to pharmacological stimulation, with chronic longitudinal heart rate reduction. These data provide some preliminary evidence of potential functional shifts in autonomic nervous system function in models of joint injury and OA.

Sodium alginate microencapsulation of human mesenchymal stromal cells modulates paracrine signaling response and enhances efficacy for treatment of established osteoarthritis

Mesenchymal stromal cells (MSCs) have shown promise as osteoarthritis (OA) treatments; however, effective translation has been limited by high variability and heterogeneity of MSCs, suboptimal delivery strategies, and poor understanding of critical quality and potency attributes. Furthermore, most pre-clinical studies of MSC therapeutics for OA have focused on delaying OA development and not on treating established OA, which brings added clinical relevance. Thus, the objective of the current study was to assess the effects of sodium alginate microencapsulation on human MSC (hMSC) secretion of immunomodulatory cytokines in an OA microenvironment and therapeutic efficacy in treating established OA. A Medial Meniscal Transection (MMT) pre-clinical model of OA was implemented. Three weeks post-surgery, after OA was established, intra-articular injections of encapsulated hMSCs or nonencapsulated hMSCs were administered. Six weeks post-surgery, microstructural changes in the knee joint were quantified using microCT. Encapsulated hMSCs reduced articular cartilage degeneration and subchondral bone remodeling. A multiplexed immunoassay panel was used to profile the in vitro secretome of hMSCs in response to IL-1β. Nonencapsulated hMSCs showed an indiscriminate increase in all cytokines in response to IL-1β while encapsulated hMSCs showed a targeted secretory response with increased expression of pro-inflammatory (IL-1β, IL-6, IL-7, IL-8), anti-inflammatory (IL-1RA), and chemotactic (G-CSF, MDC, IP10) cytokines. These data show that sodium alginate microencapsulation can modulate hMSC paracrine signaling and enhance the therapeutic efficacy of the hMSCs in treating established OA. This cytokine profile provides a foundation for the identification of key factors affecting the overall potency of hMSC therapeutics for OA. STATEMENT OF SIGNIFICANCE: While there has been considerable interest in material based MSC encapsulation for treatment of OA, there are critical gaps in our translational understanding of these biomaterial-based technologies for OA. More specifically, previous studies have several important limitations: (1) they have been largely focused on preventing OA development, which limits their translational utility and (2) little prior work has been done to delineate potential routes/mechanisms by which material encapsulation alters MSC therapeutic action. In our manuscript, we aimed to fill these gaps in knowledge by testing the hypotheses that: (1) hMSC encapsulation can attenuate established disease progression, which is a more clinically relevant scenario and (2) hMSC encapsulation significantly changes the secreted paracrine factors from hMSCs.

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.

Innovations and advances in modelling and measuring pain in animals

Best practices in preclinical algesiometry (pain behaviour testing) have shifted over the past decade as a result of technological advancements, the continued dearth of translational progress and the emphasis that funding institutions and journals have placed on rigour and reproducibility. Here we describe the changing trends in research methods by analysing the methods reported in preclinical pain publications from the past 40 years, with a focus on the last 5 years. We also discuss how the status quo may be hampering translational success. This discussion is centred on four fundamental decisions that apply to every pain behaviour experiment: choice of subject (model organism), choice of assay (pain-inducing injury), laboratory environment and choice of outcome measures. Finally, we discuss how human tissues, which are increasingly accessible, can be used to validate the translatability of targets and mechanisms identified in animal pain models.

Pharmacological characterization of GLPG1972/S201086, a potent and selective small-molecule inhibitor of ADAMTS5

OBJECTIVE

A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) is a key enzyme in degradation of cartilage in osteoarthritis (OA). We report the pharmacological characterization of GLPG1972/S201086, a new, potent and selective small-molecule ADAMTS5 inhibitor.

METHODS

Potency and selectivity of GLPG1972/S201086 for ADAMTS5 were determined using fluorescently labeled peptide substrates. Inhibitory effects of GLPG1972/S201086 on interleukin-1α-stimulated glycosaminoglycan release in mouse femoral head cartilage explants and on interleukin-1β-stimulated release of an ADAMTS5-derived aggrecan neoepitope (quantified with ELISA) in human articular cartilage explants were determined. In the destabilization of the medial meniscus (DMM) mouse and menisectomized (MNX) rat models, effects of oral GLPG1972/S201086 on relevant OA histological and histomorphometric parameters were evaluated.

RESULTS

GLPG1972/S201086 inhibited human and rat ADAMTS5 (IC50 ± SD: 19 ± 2 nM and <23 ± 1 nM, respectively), with 8-fold selectivity over ADAMTS4, and 60->5,000-fold selectivity over other related proteases in humans. GLPG1972/S201086 dose-dependently inhibited cytokine-stimulated aggrenolysis in mouse and human cartilage explants (100% at 20 μM and 10 μM, respectively). In DMM mice, GLPG1972/S201086 (30-120 mg/kg b.i.d) vs vehicle reduced femorotibial cartilage proteoglycan loss (23-37%), cartilage structural damage (23-39%) and subchondral bone sclerosis (21-36%). In MNX rats, GLPG1972/S201086 (10-50 mg/kg b.i.d) vs vehicle reduced cartilage damage (OARSI score reduction, 6-23%), and decreased proteoglycan loss (∼27%) and subchondral bone sclerosis (77-110%).

CONCLUSIONS

GLPG1972/S201086 is a potent, selective and orally available ADAMTS5 inhibitor, demonstrating significant protective efficacy on both cartilage and subchondral bone in two relevant in vivo preclinical OA models.

Targeting Proteinase Activated Receptor-4 Reduces Mechanonociception During the Acute Inflammatory Phase but not the Chronic Neuropathic Phase of Osteoarthritis in Rats

Serine proteases are elevated in arthritic joints where they can cleave protease activated receptors (PARs) to modulate pain and inflammation. Activation of protease-activated receptor 4 (PAR4) has been implicated in inflammatory joint pain. Whether PAR4 is involved in osteoarthritis (OA) pain has not yet been explored. The aim of this study was to compare the role of PAR4 in modulating early versus late stage OA pain using two models of OA viz. monoiodoacetate (MIA) and medial meniscal transection (MMT). G-ratio calculation and electron microscopy analysis revealed saphenous nerve demyelination and structural damage during late stage but not early OA in both models. Using immunohistochemistry, neuronal expression of PAR4 was higher in early versus late OA. Systemic administration of the PAR4 antagonist pepducin P4pal10 reduced both secondary allodynia (von Frey hair algesiometry) and joint nociceptor firing (single unit recordings) in MMT and MIA animals compared to vehicle-treated animals in early OA. The PAR4 antagonist was ineffective at altering pain or joint afferent firing in post-inflammatory OA. During the acute phase of the models, joint inflammation as determined by laser speckle contrast analysis and intravital microscopy could be partially blocked by pepducin P4pal10. Compared to late-stage disease, inflammatory cytokines were elevated in early MIA and MMT rats. These findings suggest that PAR4 may be a viable target to treat the pain of early onset OA or during episodic inflammatory flares.

The 50 Most Cited Articles on Meniscus Injuries and Surgery from 2000 to 2019 Focus on Arthroscopic Repair or Removal, Originate from Institutions Within the United States and Were Published Before 2010

Purpose

To identify the 50 most cited original articles on meniscus injury and surgery from 2000 to 2019, and to perform a bibliometric analysis of the identified articles.

Methods

A Clarivate Web of Science search, completed in June 2020, generated a list of the most cited articles related to meniscus research. Articles were sorted by number of times cited, and review articles or those unrelated to the meniscus were removed. Articles were classified as basic science or assigned the appropriate level of evidence. Extracted data included title, authors, journal, year of publication, country/institution of origin, total number of citations, and number of citations per year.

Results

The final list of 50 included articles with a range of 106 to 490 citations and a mean of 162.34 total or 11.91 citations per year. The most cited articles appeared in 8 of the most influential journals in the field per the Journal Citation Index. Twenty-nine (58%) originated from institutions within the United States, and only 13 (26%) were published in 2010 or later. Overall, 25 (50%) were classified as therapeutic, only 5 (10%) were therapeutic randomized controlled studies, and 17 (34%) were basic science. “Arthroscopic meniscal repair or meniscectomy” appeared most frequently, with 16 (32%) falling into this subclassification.

Conclusion

This study of the most cited meniscus articles showed a strong predominance for therapeutic studies, studies generated and published within the United States, and studies focused on topics of arthroscopic repair or removal. Overwhelmingly, included articles were published before 2010, affirming the criticism that bibliometric analysis favors older articles.

Clinical relevance

This study provides information about which articles are driving the field relating to meniscus injuries and meniscus surgery in the last two decades.

Inhibition of SYK and cSrc kinases can protect bone and cartilage in preclinical models of osteoarthritis and rheumatoid arthritis

The pathophysiology of osteoarthritis (OA) includes the destruction of subchondral bone tissue and inflammation of the synovium. Thus, an effective disease-modifying treatment should act on both of these pathogenetic components. It is known that cSrc kinase is involved in bone and cartilage remodeling, and SYK kinase is associated with the inflammatory component. Thus the aim of this study was to characterize the mechanism of action and efficacy of a small molecule multikinase inhibitor MT-SYK-03 targeting SYK and cSrc kinases among others in different in vitro and in vivo arthritis models. The selectivity of MT-SYK-03 kinase inhibition was assayed on a panel of 341 kinases. The compound was evaluated in a set of in vitro models of OA and in vivo OA and RA models: surgically-induced arthritis (SIA), monosodium iodoacetate-induced arthritis (MIA), collagen-induced arthritis (CIA), adjuvant-induced arthritis (AIA). MT-SYK-03 inhibited cSrc and SYK with IC₅₀ of 14.2 and 23 nM respectively. Only five kinases were inhibited > 90% at 500 nM of MT-SYK-03. In in vitro OA models MT-SYK-03 reduced hypertrophic changes of chondrocytes, bone resorption, and inhibited SYK-mediated inflammatory signaling. MT-SYK-03 showed preferential distribution to joint and bone tissue (in rats) and revealed disease-modifying activity in vivo by halving the depth of cartilage erosion in rat SIA model, and increasing the pain threshold in rat MIA model. Chondroprotective and antiresorptive effects were shown in a monotherapy regime and in combination with methotrexate (MTX) in murine and rat CIA models; an immune-mediated inflammation in rat AIA model was decreased. The obtained preclinical data support inhibition of cSrc and SYK as a viable strategy for disease-modifying treatment of OA. A Phase 2 clinical study of MT-SYK-03 is to be started.

Standardized study of atorvastatin possible osteoarthritis disease-modifying effect in a rat model of osteoarthritis

We studied the osteoarthritis (OA)-modifying effects of atorvastatin in an experimental OA rat model and possible underlining mechanisms. We used 62 adult male Sprague-Dawley rats (250-300 g): 32 rats were used to assess the effects of atorvastatin on surgically induced OA in the knee, and 30 rats were used to assess the potential inflammatory effects of carrageenan-induced paw edema. In the OA model, joint stiffness was assessed by measuring the knee extension angle, and pathological changes in the OA knee joint were determined by histological examination and the measurement of serum biochemical markers, including interleukin-1β (IL-1β), matrix metalloproteinase-13 (MMP-13), and reduced glutathione (GSH). In the carrageenan-induced paw edema model, both paw thickness and pain threshold were assessed in different groups. Atorvastatin significantly improved joint stiffness, pathological changes, a significant mitigation of the higher MMP-13 and IL-1β, and a significant increase of reduced GSH in OA rats. Additionally, atorvastatin significantly improved both paw thickness and pain threshold in animals. Atorvastatin is a potential OA-modifying drug that warrants further clinical investigation.

TDP-43 maintains chondrocyte homeostasis and alleviates cartilage degradation in osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is the most prevalent age-related disorder due to cartilage degradation. Previous studies have identified aberrant chondrocyte homeostasis under extracellular stress as a key pathological mechanism behind cartilage degradation in OA. TDP-43, a DNA/RNA-binding protein has been demonstrated to participate in processing many extracellular stress responses; however, understanding of the role of TDP-43 in OA is limited. This study aims to investigate the role of TDP-43 in chondrocyte homeostasis and cartilage degradation in OA.

METHODS

The role of TDP-43 during degradation of cartilage is examined by experimental posttraumatic OA animal models and human cartilage specimens. Cartilage degradation is assessed by histological analysis, qPCR, and Western blot. The molecular mechanisms are investigated in vitro using human primary chondrocytes.

RESULTS

TDP-43 decreases significantly in degenerated cartilage. TDP-43 concentration is positively correlated with IL-1β concentration in synovial fluid derived from OA patients (Pearson r = 0.95, CI (95%) [0.80, 0.99], P < 0.0001). Intra-articular injection of recombinant TDP-43 significantly alleviates cartilage degradation and subchondral bone remodeling in vivo. In vitro mechanistic analyses show that TDP-43 maintains chondrocyte homeostasis under oxidative stress through regulating stress granule dynamics via G3BP1.

CONCLUSION

The present study indicates that TDP-43 maintains chondrocyte homeostasis under oxidative stress and alleviates cartilage degeneration in osteoarthritis, identifying TDP-43 as a potential target for the diagnosis and treatment of knee OA.

Discovery of bone morphogenetic protein 7-derived peptide sequences that attenuate the human osteoarthritic chondrocyte phenotype

Treatment of osteoarthritis (OA) is mainly symptomatic by alleviating pain to postpone total joint replacement. Bone morphogenetic protein 7 (BMP7) is a candidate morphogen for experimental OA treatment that favorably alters the chondrocyte and cartilage phenotype. Intra-articular delivery and sustained release of a recombinant growth factor for treating OA are challenging, whereas the use of peptide technology potentially circumvents many of these challenges. In this study, we screened a high-resolution BMP7 peptide library and discovered several overlapping peptide sequences from two regions in BMP7 with nanomolar bioactivity that attenuated the pathological OA chondrocyte phenotype. A single exposure of OA chondrocytes to peptides p[63-82] and p[113-132] ameliorated the OA chondrocyte phenotype for up to 8 days, and peptides were bioactive on chondrocytes in OA synovial fluid. Peptides p[63-82] and p[113-132] required NKX3-2 for their bioactivity on chondrocytes and provoke changes in SMAD signaling activity. The bioactivity of p[63-82] depended on specific evolutionary conserved sequence elements common to BMP family members. Intra-articular injection of a rat medial meniscal tear (MMT) model with peptide p[63-82] attenuated cartilage degeneration. Together, this study identified two regions in BMP7 from which bioactive peptides are able to attenuate the OA chondrocyte phenotype. These BMP7-derived peptides provide potential novel disease-modifying treatment options for OA.

Evaluation of CCL21 role in post-knee injury inflammation and early cartilage degeneration

The expression of some chemokines and chemokine receptors is induced during the development of post-traumatic osteoarthritis (PTOA), but their involvement in the pathogenesis of the disease is unclear. The goal of this study was to test whether CCL21 and CXCL13 play a role in PTOA development. For this purpose, we evaluated the expression profiles of the chemokines Ccl21 and Cxcl13, matrix metalloproteinase enzymes Mmp3 and Mmp13, and inflammatory cell markers in response to partial medial meniscectomy and destabilization (MMD). We then assessed the effect of local administration of CCL21 neutralizing antibody on PTOA development and post-knee injury inflammation. The mRNA expression of both Ccl21 and Cxcl13 was induced early post-surgery, but only Ccl21 mRNA levels remained elevated 4 weeks post-surgery in rat MMD-operated knees compared to controls. This suggests that while both CXCL13 and CCL21 are involved in post-surgery inflammation, CCL21 is necessary for development of PTOA. A significant increase in the mRNA levels of Cd4, Cd8 and Cd20 was observed during the first 3 days post-surgery. Significantly, treatment with CCL21 antibody reduced post-surgical inflammation that was accompanied by a reduction in the expression of Mmp3 and Mmp13 and post-MMD cartilage degradation. Our findings are consistent with a role for CCL21 in mediating changes in early inflammation and subsequent cartilage degeneration in response to knee injury. Our results suggest that targeting CCL21 signaling pathways may yield new therapeutic approaches effective in delaying or preventing PTOA development following injury.

Refining surgical models of osteoarthritis in mice and rats alters pain phenotype but not joint pathology

The relationship between osteoarthritis (OA) structural change and pain is complex. Surgical models of OA in rodents are often rapid in onset, limiting mechanistic utility and translational validity. We aimed to investigate the effect of refining surgical small rodent models of OA on both joint pathology and pain behaviour. Adult male C57BL/6 mice (n = 76, 10-11 weeks of age at time of surgery) underwent either traditional (transection of the medial meniscotibial ligament [MMTL]) or modified (MMTL left intact, transection of the coronary ligaments) DMM surgery, or sham surgery. Adult male Sprague Dawley rats (n = 76, weight 175-199g) underwent either modified meniscal transection (MMNX) surgery (transection of the medial meniscus whilst the medial collateral ligament is left intact) or sham surgery. Pain behaviours (weight bearing asymmetry [in mice and rats] and paw withdrawal thresholds [in rats]) were measured pre-surgery and weekly up to 16 weeks post-surgery. Post-mortem knee joints were scored for cartilage damage, synovitis, and osteophyte size. There was a significant increase in weight bearing asymmetry from 13 weeks following traditional, but not modified, DMM surgery when compared to sham operated mice. Both traditional and modified DMM surgery led to similar joint pathology. There was significant pain behaviour from 6 weeks following MMNX model compared to sham operated control rats. Synovitis was significant 4 weeks after MMNX surgery, whereas significant chondropathy was first evident 8 weeks post-surgery, compared to sham controls. Pain behaviour is not always present despite significant changes in medial tibial plateau cartilage damage and synovitis, reflecting the heterogeneity seen in human OA. The development of a slowly progressing surgical model of OA pain in the rat suggests that synovitis precedes pain behaviour and that chondropathy is evident later, providing the foundations for future mechanistic studies into the disease.

Alleviation of medial meniscal transection-induced osteoarthritis pain in rats by human adipose derived mesenchymal stem cells

Knee osteoarthritis (KOA) is a degenerative joint disorder manifested with deformity, pain, and functional disability due to damage of the articular cartilage. Cell therapy with mesenchymal stem cells (MSCs) holds great promise to alleviate or even cure the degenerative diseases including KOA. However, the evidence of efficacy of human adipose tissue-derived MSCs (hAdMSCs) on KOA therapy remains limited. Here, we evaluate the therapeutic efficacy of hAdMSCs for KOA, using a medial meniscal transection (MMT) rat model. Our study demonstrated that intra-articular injection of 1.25×10⁶ hAdMSCs significantly attenuated MMT-induced joint pain in a KOA rats model. The results of this study provide strong evidence that hAdMSCs-based therapy can be regarded as a prominent treatment option for patients with KOA.

Aggrecanase-selective tissue inhibitor of metalloproteinase-3 (TIMP3) protects articular cartilage in a surgical mouse model of osteoarthritis

A key feature of osteoarthritis is the gradual loss of articular cartilage and bone deformation, resulting in the impairment of joint function. The primary cause of cartilage destruction is considered to be the presence of elevated proteases, such as matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs). However, clinically tested global MMP inhibitors have low efficacy that may be due to their lack of selectivity. We previously demonstrated in vitro that a variant of tissue inhibitor of metalloproteinase-3 ([-1A]TIMP3) inhibits ADAMTSs but not MMPs. In this study, we tested whether the selectivity of [-1A]TIMP3 is beneficial compared with that of the wild-type TIMP3 in preventing or delaying the onset of the degenerative effects in a mouse model of osteoarthritis. We generated transgenic mice that overexpressed TIMP3 or [-1A]TIMP3 driven by a chondrocyte-specific type II collagen promoter. TIMP3 transgenic mice showed compromised bone integrity as opposed to [-1A]TIMP3 mice. After surgically induced joint instability, TIMP3 overexpression proved to be less protective in cartilage destruction than [-1A]TIMP3 at late stages of OA. The selective inhibition of ADAMTSs provides the possibility of modifying TIMP3 to specifically target a class of cartilage-degrading proteinases and to minimize adverse effects on bone and possibly other tissues.

Viscosupplementation may preserve tibial cartilage and collagen in osteoarthritis: findings from a preclinical model of osteoarthritis

PURPOSE

Intraarticular (IA) hyaluronic acid (HA) injection is used to reduce pain and improve mobility in knee osteoarthritis (OA). Little is known about histopathological changes underlying HA efficacy. This study investigated dose-related effects of 1% sodium hyaluronate (BioHA) on knee joint histopathology and pain responses in a medial meniscal tear (MMT) rat model of OA.

METHODS

Following MMT surgery, rats were randomized into treatment groups: single IA injection of vehicle, BioHA, or an avian-derived hyaluronic acid (hylan G-F 20) on Day 7; or 3 weekly injections of vehicle or BioHA on Days 7, 14, and 21. On Day 35, joints were evaluated by microscopic histopathology for cartilage degeneration, collagen degeneration, synovitis, and cytokine expression (tumor necrosis factor α, transforming growth factor β).

RESULTS

Joint pathology for control animals was consistent with that expected for the MMT model. Rats treated with 3 injections of IA-BioHA had significantly reduced collagen degeneration (21%) relative to control animals. No significant change in collagen degeneration was observed for rats given a single injection of hylan G-F 20 or IA-BioHA compared to control animals. HA treatment did not affect cytokine expression.

CONCLUSIONS

IA-BioHA viscosupplementation in a rat MMT model of OA showed preservation of joint cartilage and collagen. This effect was most pronounced on tibial surfaces having less severe injury, suggesting that treatment should be initiated early in the disease process. A comparison of responses to IA-BioHA or hylan G-F 20 in the MMT rat OA model suggest IA-BioHA may be more effective in preserving joint connective tissue.

Pain and knee damage in male and female mice in the medial meniscal transection-induced osteoarthritis

OBJECTIVE

To investigate sex effects on pain-related behaviors in the medial meniscal transection (MMT) knee osteoarthritis (OA) model.

METHODS

Experiments were performed in male and female C57BL/6J mice (12/group/sex). MMT was induced by transection of the medial collateral ligament and the medial meniscus. Sham-operated and naïve mice served as controls. Mechanical and heat sensitivity in hind paws, hind limb use, and locomotor activity were measured for 3 months. Knee histology was performed on week 12.

RESULTS

In males, MMT triggered a bi-phasic mechanical hypersensitivity and decreased load on OA limb, with an acute post-operative (1-5 days) and chronic (3-12 weeks) OA phases separated by a remission in the intermediate phase (1-2 weeks). Females showed a less pronounced bi-phasic pattern, with a greater mechanical hypersensitivity, but not poorer limb use, than males in the intermediate phase (maximal difference: 1.1 g, 95% confidence intervals (CI) [0.7, 1.5]). There were no major sex differences in the chronic phase. MMT did not induce heat hypersensitivity or change in locomotor activity in the chronic phase in both sexes. MMT caused more severe cartilage damage in males than in females (maximal difference: 1.1 score points, 95% CI [1.9, 0.3]), and a comparable between sexes osteophyte formation. The knee damage did not correlate with pain.

CONCLUSIONS

MMT modelled human knee OA well, capturing cartilage destruction and osteophyte formation, mechanical pain, and poorer limb use in both sexes. Sex differences in pain were modality- and time-dependent, reflecting complex sex-related features of human OA.

Vitellaria paradoxa Nut Triterpene-Rich Extract Ameliorates Symptoms of Inflammation on Post-Traumatic Osteoarthritis in Obese Rats

Purpose

To investigate the ameliorative effects of Vitellaria paradoxa (VP) nut extract for an anterior cruciate ligament transection with medial meniscectomy (ACLT+MMx)-induced osteoarthritis (OA) in high-fat diet (HFD)-induced obese rats.

Methods

The rats were fed by HFD for 5 weeks before surgery-induced OA. Rats were treated orally with three different doses of VP nut extract (111.6, 223.2, and 446.4 mg/kg) for 8 weeks.

Results

The VP nut triterpene-rich extract decreased the level of triglycerides and increased high-density lipoprotein-cholesterol. The level of nitric oxide, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α decreased after treatment with VP nut triterpene-rich extract, especially in high-doses. The VP nut triterpene-rich extracts also alleviated swelling in the knee OA, weight-bearing difference, and suppressed cartilage degradation.

Conclusion

The Vitellaria paradoxa nut triterpene-rich extract suppressed proinflammatory mediators and attenuated the cartilage degradation and pain in osteoarthritis with an obesity rat model. As such, Vitellaria paradoxa nut triterpene-rich extract can be used as an alternative for osteoarthritis treatment.

The effects of age on the severity of joint damage and intra-articular inflammation following a simulated medial meniscus injury in 3, 6, and 9 month old male rats

Purpose: Aging is a known risk factor for osteoarthritis (OA). Several transgenic rodent models have been used to investigate the effects of accelerated or delayed aging in articular joints. However, age-effects on the progression of post-traumatic OA are less frequently evaluated. The objective of this study is to evaluate how animal age affects the severity of intra-articular inflammation and joint damage in the rat medial collateral ligament plus medial meniscus transection (MCLT+MMT) model of knee OA.Methods: Forty-eight, male Lewis rats were aged to 3, 6, or 9 months old. At each age, eight rats received either an MCLT+MMT surgery or a skin-incision. At 2 months post-surgery, intra-articular evidence of CTXII, IL1β, IL6, TNFα, and IFNγ was evaluated using a multiplex magnetic capture technique, and histological evidence of OA was assessed via a quantitative histological scoring technique.Results: Elevated levels of CTXII and IL6 were found in MCLT+MMT knees relative to skin-incision and contralateral controls; however, animal age did not affect the severity of joint inflammation. Conversely, histological investigation of cartilage damage showed larger cartilage lesion areas, greater width of affected cartilage, and more evidence of hypertrophic cartilage damage in MCLT+MMT knees with age.Conclusions: These data indicate the severity of cartilage damage subsequent to MCLT+MMT surgery is related to the rat's age at the time of injury. However, despite greater levels of cartilage damage, the level of intra-articular inflammation was not necessarily affected in 3, 6, and 9 month old male rats.

Reduced Size Profile of Amniotic Membrane Particles Decreases Osteoarthritis Therapeutic Efficacy

Osteoarthritis (OA) is a widespread disease that continues to lack approved and efficacious treatments that modify disease progression. Micronized dehydrated human amnion/chorion membrane (μ-dHACM) has been shown to be effective in reducing OA progression, but many of the engineering design parameters have not been explored. The objectives of this study were to characterize the particle size distributions of two μ-dHACM formulations and to investigate the influence of these distributions on the in vivo therapeutic efficacy of μ-dHACM. Male Lewis rats underwent medial meniscus transection (MMT) or sham surgery, and intra-articular injections of saline, μ-dHACM, or reduced particle size μ-dHACM (RPS μ-dHACM) were administered at 24 hours postsurgery (n = 9 per treatment group). After 3 weeks, the animals were euthanized, and left legs harvested for equilibrium partitioning of an ionic contrast agent microcomputed tomography and histological analysis. μ-dHACM and RPS μ-dHACM particles were fluorescently tagged and particle clearance was tracked in vivo for up to 42 days postsurgery. Protein elution from both formulations was quantified in vitro. Treatment with μ-HACM, but not RPS μ-dHACM, reduced lesion volume in the MMT model 3 weeks postsurgery. In contrast, RPS μ-dHACM increased cartilage surface roughness and osteophyte cartilage thickness and volume compared to saline treatment. There was no difference of in vivo fluorescently tagged particle clearance between the two μ-dHACM sizes. RPS μ-dHACM showed significantly greater protein elution in vitro over 21 days. Overall, delivery of RPS μ-dHACM did result in an increase of in vivo joint degeneration and in vitro protein elution compared to μ-dHACM, but did not result in differences in joint clearance in vivo. These results suggest that particle size and factor elution may be tailorable factors that are important to optimize for particulate amniotic membrane treatment to be an effective therapy for OA. Impact Statement Osteoarthritis (OA) is a widespread disease that continues to lack treatments that modify the progression of the disease. Micronized dehydrated human amnion/chorion membrane (μ-dHACM) has been shown to be effective in reducing OA progression, but many of the engineering design parameters have not been explored. This work investigates the effects of particle size profile of the μ-dHACM particles and lays out the methods used in these studies. The results of this work will guide engineers in designing μ-dHACM treatments specifically and disease-modifying OA therapeutics generally, and it demonstrates the utility of novel therapeutic evaluation methods such as contrast-enhanced microcomputed tomography.

Euphorbia bicolor (Euphorbiaceae) Latex Extract Reduces Inflammatory Cytokines and Oxidative Stress in a Rat Model of Orofacial Pain

Recent studies have reported that the transient receptor potential V1 ion channel (TRPV1), a pain generator on sensory neurons, is activated and potentiated by NADPH oxidase-generated reactive oxygen species (ROS). ROS are increased by advanced oxidation protein products (AOPPs), which activate NADPH oxidase by upregulating Nox4 expression. Our previous studies reported that Euphorbia bicolor (Euphorbiaceae) latex extract induced peripheral analgesia, partly via TRPV1, in hindpaw-inflamed male and female rats. The present study reports that E. bicolor latex extract also can evoke analgesia via reduction of oxidative stress biomarkers and proinflammatory cytokines/chemokines in a rat model of orofacial pain. Male and female rats were injected with complete Freund's adjuvant (CFA) into the left vibrissal pad to induce orofacial inflammation, and mechanical allodynia was measured by the von Frey method. Twenty-four hours later, rats received one injection of E. bicolor latex extract or vehicle into the inflamed vibrissal pad. Mechanical sensitivity was reassessed at 1, 6, 24, and/or 72 hours. Trigeminal ganglia and trunk blood were collected at each time point. In the trigeminal ganglia, ROS were quantified using 2',7'-dichlorodihydrofluorescein diacetate dye, Nox4 protein was quantified by Western blots, and cytokines/chemokines were quantified using a cytokine array. AOPPs were quantified in trunk blood using a spectrophotometric assay. E. bicolor latex extract significantly reduced orofacial mechanical allodynia in male and female rats at 24 and 72 hours, respectively. ROS, Nox4, and proinflammatory cytokines/chemokines were significantly reduced in the trigeminal ganglia, and plasma AOPP was significantly reduced in the trunk blood of extract-treated compared to vehicle-treated rats. In vitro assays indicate that E. bicolor latex extract possessed antioxidant activities by scavenging free radicals. Together our data indicate that the phytochemicals in E. bicolor latex may serve as novel therapeutics for treating oxidative stress-induced pain conditions.

A dual amylin and calcitonin receptor agonist inhibits pain behavior and reduces cartilage pathology in an osteoarthritis rat model

OBJECTIVES

Pain and disability are the main clinical manifestations of osteoarthritis, for which only symptomatic therapies are available. Hence, there is a need for therapies that can simultaneously alter disease progression and provide pain relief. KBP is a dual amylin- and calcitonin-receptor agonist with antiresorptive and chondroprotective properties. In this study we investigated the effect of KBP in a rat model of osteoarthritis.

METHODS

Medial meniscectomy (MNX) was performed in 39 rats, while 10 underwent sham surgery. Rats were treated with KBP and/or naproxen. Nociception was assessed by mechanical and cold allodynia, weight bearing asymmetry, and burrowing behavior. Blood samples were collected for biomarker measurements, and knees for histology. Cartilage histopathology was evaluated according to the advanced Osteoarthritis Research International (OARSI) score and KBPs in vitro antiresorptive effects were assessed using human osteoclasts cultured on bone.

RESULTS

The MNX animals displayed an increased nociceptive behavior. Treatment with KBP attenuated the MNX-induced osteoarthritis-associated joint pain. The cartilage histopathology was significantly lower in rats treated with KBP than in MNX animals. Bone and cartilage degradation, assessed by CTX-I and CTX-II plasma levels, were decreased in all KBP-treated groups and KBP potently inhibited bone resorption in vitro.

CONCLUSIONS

Our study demonstrates the effectiveness of KBP in ameliorating osteoarthritis-associated joint pain and in protecting the articular cartilage, suggesting KBP as a potential drug candidate for osteoarthritis.

Regional gene expression analysis of multiple tissues in an experimental animal model of post-traumatic osteoarthritis

OBJECTIVE

To characterize local disease progression of the medial meniscus transection (MMT) model of post-traumatic osteoarthritis (OA) at the molecular level, in order to establish a baseline for therapeutic testing at the preclinical stage.

DESIGN

Weight-matched male Lewis rats underwent MMT or sham surgery on the left limb with the right leg as contralateral control. At 1 and 3 weeks post-surgery, tissues were harvested from different areas of the articular cartilage (medial and lateral tibial plateaus, and medial osteophyte region) and synovium (medial and lateral), and analyzed separately. RNA was extracted and used for microarray (RT-PCR) analysis.

RESULTS

Gene expression changes due to surgery were isolated to the medial side of the joint. Gene changes in chondrocyte phenotype of the medial tibial plateau cartilage preceded changes in tissue composition genes. Differences in inflammatory markers were only observed at the osteophyte region at 3 weeks post-surgery. There was surgical noise in the synovium at week 1, which dissipated at week 3. At this later timepoint, meniscal instability resulted in elevated expression of matrix degradation proteins and osteogenic markers in the synovium and cartilage.

CONCLUSION

These results suggest feedback interactions between joint tissues during disease progression. Regional tissue expression differences found in MMT joints indicated similar pathophysiology to human OA, and provided novel insights about this degeneration model. The examination of gene expression at a localized level in multiple tissues provides a well-characterized baseline to evaluate mechanistic effects of potential therapeutic agents on OA disease progression in the MMT model.

Therapeutic efficacy of intra-articular delivery of encapsulated human mesenchymal stem cells on early stage osteoarthritis

Mesenchymal stem cells (MSCs) represent a great therapeutic promise in pre-clinical models of osteoarthritis (OA), but many questions remain as to their therapeutic mechanism of action: engraftment versus paracrine action. Encapsulation of human MSCs (hMSCs) in sodium alginate microspheres allowed for the paracrine signaling properties of these cells to be isolated and studied independently of direct cellular engraftment. The objective of the present study was to quantitatively assess the efficacy of encapsulated hMSCs as a disease-modifying therapeutic for OA, using a medial meniscal tear (MMT) rat model. It was hypothesized that encapsulated hMSCs would have a therapeutic effect, through paracrine-mediated action, on early OA development. Lewis rats underwent MMT surgery to induce OA. 1 d post-surgery, rats received intra-articular injections of encapsulated hMSCs or controls (i.e., saline, empty capsules, non-encapsulated hMSCs). Microstructural changes in the knee joint were quantified using equilibrium partitioning of a ionic contrast agent based micro-computed tomography (EPIC-μCT) at 3 weeks post-surgery, an established time point for early OA. Encapsulated hMSCs significantly attenuated MMT-induced increases in articular cartilage swelling and surface roughness and augmented cartilaginous and mineralized osteophyte volumes. Cellular encapsulation allowed to isolate the hMSC paracrine signaling effects and demonstrated that hMSCs could exert a chondroprotective therapeutic role on early stage OA through paracrine signaling alone. In addition to this chondroprotective role, encapsulated hMSCs augmented the compensatory increases in osteophyte formation. The latter should be taken into strong consideration as many clinical trials using MSCs for OA are currently ongoing.

Discovery of Novel Transient Receptor Potential Vanilloid 4 (TRPV4) Agonists as Regulators of Chondrogenic Differentiation: Identification of Quinazolin-4(3 H)-ones and in Vivo Studies on a Surgically Induced Rat Model of Osteoarthritis

Osteoarthritis (OA) is a degenerative disease characterized by joint destruction and loss of cartilage. There are many unmet needs in the treatment of OA and there are few promising candidates for disease-modifying OA drugs, particularly, anabolic agents. Here, we describe the identification of novel quinazolin-4(3 H)-one derivatives, which stimulate chondrocyte cartilage matrix production via TRPV4 and mitigate damaged articular cartilage. We successfully identified the water-soluble, highly potent quinazolin-4(3 H)-one derivative 36 and studied its intra-articular physicochemical profile to use in in vivo surgical OA model studies. Compound 36·HCl provided relief from OA damage in a rat medial meniscal tear (MT) model. Specifically, 36·HCl dose-dependently suppressed cartilage degradation and enhanced the messenger RNA expression of aggrecan and SOX9 in cartilage isolated from MT-operated rat knees compared with knees treated with vehicle. These results suggest that 36 induces anabolic changes in articular cartilage and consequently reduces OA progression.

Analgesic effects of the cathepsin K inhibitor L-006235 in the monosodium iodoacetate model of osteoarthritis pain

INTRODUCTION

The mounting evidence that osteoclasts play an important role in osteoarthritis (OA) pain lead us to investigate the effects of L-006235, a potent and selective inhibitor of cathepsin K, on pain behaviour and joint pathology in a model of OA pain.

METHODS

Effects of preventative (30 and 100 mg/kg) and therapeutic (100 mg/kg) oral dosing with L-006235 on weight-bearing asymmetry, hind paw withdrawal thresholds, cartilage and bone pathology, synovial inflammation, and drug exposure were studied in the monosodium iodoacetate rat model of OA pain.

RESULTS

Preventative L-006235 inhibited weight-bearing asymmetry from day 14, with this measure nearly abolished by the higher dose. In the same treatment setting, L-006235 prevented lowering of hind paw withdrawal thresholds from day 7. Exposure to L-006235 in plasma was higher for the 100 mg/kg dose, compared with 30 mg/kg. Therapeutic dosing with L-006235 from day 14 significantly inhibited weight-bearing asymmetry, compared with monosodium iodoacetate vehicle rats. Regression analysis revealed a significant interaction coefficient of the effects of L-006235 on weight-bearing asymmetry and synovitis score, but not for cartilage damage nor osteophyte scores.

CONCLUSION

Our novel finding that cathepsin K inhibition is analgesic in a clinically relevant model of OA pain provides new evidence for the therapeutic potential of this target.

Changes in proinflammatory cytokines, neuropeptides, and microglia in an animal model of monosodium iodoacetate-induced hip osteoarthritis

The aim of this study was to investigate the local production of proinflammatory cytokines, pain-related sensory innervation of dorsal-root ganglia (DRG), and spinal changes in a rat model of induced hip osteoarthritis (OA). Seventy-five Sprague-Dawley rats were used, including 25 controls and 50 injected into the right hip joints (sham group, injected with 25 µl of sterile saline: N = 25; and monosodium iodoacetate (MIA) group, injected with 25 µl of sterile saline with 2 mg of MIA: N = 25). We measured the local production of TNF-α, immunoreactive (-ir) neurons for calcitonin gene-related peptide (CGRP), and growth associated protein-43 (GAP-43) in DRG, and immunoreactive neurons for ionized-calcium-binding adaptor molecule-1 (Iba-1) in the dorsal horn of spinal cord, on post-induction days 7, 14, 28, 42, and 56 (N = 5 rats/group/time point). For post-induction days 7-42, the MIA group presented significantly elevated concentrations of TNF-α than the other groups (p < 0.01), and a higher expression of CGRP-ir in FG-labeled DRG neurons than the sham group (p < 0.01). MIA rats also presented significantly more FG-labeled GAP-43-ir DRG neurons than the sham group on post-induction days 28, 42, and 56 (p < 0.05), and a significantly higher number of Iba-1-ir microglia in the ipsilateral dorsal horn than the other groups, on post-induction days 28, 42, and 56. The results suggest that in rat models, pain-related pathologies due to MIA-induced hip OA, originate from inflammation caused by cytokines, which leads to progressive, chronic neuronal damage that may cause neuropathic pain. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2978-2986, 2018.

Selective Enzymatic Digestion of Proteoglycans and Collagens Alters Cartilage T1rho and T2 Relaxation Times

Our objective was to determine the relationship of T1rho and T2 relaxation mapping to the biochemical and biomechanical properties of articular cartilage through selective digestion of proteoglycans and collagens. Femoral condyles were harvested from porcine knee joints and treated with either chondroitinase ABC (cABC) followed by collagenase, or collagenase followed by cABC. Magnetic resonance images were acquired and cartilage explants were harvested for biochemical, biomechanical, and histological analyses before and after each digestion. Targeted enzymatic digestion of proteoglycans with cABC resulted in elevated T1rho relaxation times and decreased sulfated glycosaminoglycan content without affecting T2 relaxation times. In contrast, extractable collagen and T2 relaxation times were increased by collagenase digestion; however, neither was altered by cABC digestion. Aggregate modulus decreased with digestion of both components. Overall, we found that targeted digestion of proteoglycans and collagens had varying effects on biochemical, biomechanical, and imaging properties. T2 relaxation times were altered with changes in extractable collagen, but not changes in proteoglycan. However, T1rho relaxation times were altered with proteoglycan loss, which may also coincide with collagen disruption. Since it is unclear which matrix components are disrupted first in osteoarthritis, both markers may be important for tracking disease progression.

Effects of carrageenan induced synovitis on joint damage and pain in a rat model of knee osteoarthritis

OBJECTIVE

Knee osteoarthritis (OA) is associated with ongoing pain and joint damage that can be punctuated by acute flares of pain and inflammation. Synovitis in normal knees might resolve without long-term detriment to joint function. We hypothesised that osteoarthritis is associated with impaired resilience to inflammatory flares.

DESIGN

We induced synovitis by injecting carrageenan into rat knees with or without meniscal transection (MNX)-induced OA, and measured synovitis, weightbearing asymmetry (pain behaviour), and joint damage up to 35 days after OA induction (23 days after carrageenan-injection).

RESULTS

Carrageenan injection induced weightbearing asymmetry for 1 week, transient increase in knee diameter for 2 days, and a sustained increase in synovial macrophages, endothelial cell proliferation and vascular density compared with naive vehicle-injected controls. MNX surgery induced weightbearing asymmetry and histological evidence of OA. Carrageenan-injection in MNX-operated knees was followed for 2 days by increased weightbearing asymmetry compared either to MNX+vehicle or to sham+carrageenan groups. OA structural damage and synovitis at day 35 were greater in MNX+carrageenan compared to MNX+vehicle and sham+carrageenan groups. Carrageenan injection did not induce OA in Sham-operated knees.

CONCLUSION

Intra-articular injection of the pro-inflammatory compound carrageenan in OA and sham-operated control knees induced a short term increase in joint pain. Even though pain flares resolved in both groups and damage was not induced in sham-operated knees, carrageen injection exacerbated long-term joint damage in OA knees. OA knees display less resilience to inflammatory episodes. Preventing inflammatory flares may be particularly important in preventing symptoms and long term joint damage in OA.

Subchondral bone fragility with meniscal tear accelerates and parathyroid hormone decelerates articular cartilage degeneration in rat osteoarthritis model

The aims of this study were to investigate the influence of subchondral bone fragility (SBF) on the progression of the knee osteoarthritis by using a novel rat model, and to examine the preventive effect of parathyroid hormone (PTH) on cartilage degeneration. First, 40 rats were assigned to the following four groups: Sham, SBF, Medial meniscal tear (MMT), and MMT + SBF groups. In SBF and MMT + SBF groups, we induced SBF by microdrilling the subchondral bone. Second, 10 additional rats were randomly assigned to the following two groups: MMT + SBF + saline and MMT + SBF + PTH groups. Osteoarthritic changes in the articular cartilage and subchondral bone were evaluated using safranin-O/fast green staining, matrix metalloproteinase-13 (MMP-13), and type X collagen immunohistochemistry, toluidine blue staining, and micro-CT scanning. The combination of SBF and meniscal tear increased the number of mast cells in the subchondral bone, and led to the abnormal subchondral bone microarchitecture, such as abnormally decreased trabecular number and increased trabecular thickness, compared with meniscal tear alone. Moreover, SBF with meniscal tear enhanced articular cartilage degeneration and increased the expression of MMP-13 and type X collagen, compared with meniscal tear alone. The administration of PTH decreased the number of mast cells in the subchondral bone and improved the microstructural parameters of the subchondral bone, and delayed the progression of articular cartilage degeneration. These results suggest that SBF is one of the factors underlying the osteoarthritis development, especially in knees with traumatic osteoarthritis, and that the administration of PTH is a potential therapeutic treatment for preventing OA progression. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1959-1968, 2018.

Intraperitoneal injection of thalidomide alleviates early osteoarthritis development by suppressing vascular endothelial growth factor expression in mice

Vascular endothelial growth factor (VEGF) is expressed in articular cartilage and increases in expression levels have been associated with the progression of osteoarthritis (OA). Thalidomide is a drug that has been reported to inhibit angiogenesis and reduce VEGF production by downregulating VEGF expression. The objective of the present study was to determine whether intraperitoneal administration of thalidomide may attenuate early OA development in mice. Male C57BL/6 mice (10‑weeks‑old) were randomly assigned into the destabilization of the medial meniscus (Dmm) with thalidomide treatment (Dmm+Th), Dmm and Sham groups equally. An OA model was induced surgically in Dmm+Th and Dmm groups, and mice of the Dmm+Th group were subsequently treated with an intraperitoneal injection of thalidomide (200 mg/kg/day). At 2 and 4 weeks following surgery, the pathological alterations in cartilage samples were assessed qualitatively by hematoxylin and eosin staining and Safranin O/Fast green staining, and quantitatively by the Osteoarthritis Research Society International scoring system. The mRNA expression levels of matrix metalloproteinase‑13 (MMP‑13) and VEGF were measured by reverse transcription‑quantitative polymerase chain reaction. The protein expression levels of MMP‑13 and VEGF were detected by immunofluorescence and immunohistochemistry, respectively. The production of VEGF in serum was evaluated via an ELISA assay. Pathological scores were significantly higher in the Dmm and the Dmm+Th groups than those in the Sham group; however, the Dmm+Th group exhibited markedly less severe pathological changes compared with the Dmm group. Compared with the Sham group, the mRNA and protein expression levels of VEGF and MMP‑13 in the Dmm and the Dmm+Th groups were significantly increased. The Dmm+Th group exhibited significantly decreased expression levels of VEGF and MMP‑13, as well as significantly decreased serum VEGF concentration compared with the Dmm group. Thus, the results of the present study demonstrated that intraperitoneal administration of thalidomide may alleviate the development of early OA by suppressing VEGF expression in mice and may have potential as a novel therapy for the treatment of OA.

The Pathobiology of the Meniscus: A Comparison Between the Human and Dog

Serious knee pain and related disability have an annual prevalence of approximately 25% on those over the age of 55 years. As curative treatments for the common knee problems are not available to date, knee pathologies typically progress and often lead to osteoarthritis (OA). While the roles that the meniscus plays in knee biomechanics are well characterized, biological mechanisms underlying meniscus pathophysiology and roles in knee pain and OA progression are not fully clear. Experimental treatments for knee disorders that are successful in animal models often produce unsatisfactory results in humans due to species differences or the inability to fully replicate disease progression in experimental animals. The use of animals with spontaneous knee pathologies, such as dogs, can significantly help addressing this issue. As microscopic and macroscopic anatomy of the canine and human menisci are similar, spontaneous meniscal pathologies in canine patients are thought to be highly relevant for translational medicine. However, it is not clear whether the biomolecular mechanisms of pain, degradation of extracellular matrix, and inflammatory responses are species dependent. The aims of this review are (1) to provide an overview of the anatomy, physiology, and pathology of the human and canine meniscus, (2) to compare the known signaling pathways involved in spontaneous meniscus pathology between both species, and (3) to assess the relevance of dogs with spontaneous meniscal pathology as a translational model. Understanding these mechanisms in human and canine meniscus can help to advance diagnostic and therapeutic strategies for painful knee disorders and improve clinical decision making.

Contrast enhanced μCT imaging of early articular changes in a pre-clinical model of osteoarthritis

OBJECTIVE

The objective of this study was to characterize early osteoarthritis (OA) development in cartilage and bone tissues in the rat medial meniscus transection (MMT) model using non-destructive equilibrium partitioning of an ionic contrast agent micro-computed tomography (EPIC-μCT) imaging. Cartilage fibrillation, one of the first physiological developments in OA, was quantified in the rat tibial plateau as three-dimensional (3D) cartilage surface roughness using a custom surface-rendering algorithm.

METHODS

Male Lewis rats underwent MMT or sham-operation in the left leg. At 1- and 3-weeks post-surgery, the animals (n = 7-8 per group) were euthanized and the left legs were scanned using EPIC-μCT imaging to quantify cartilage and bone parameters. In addition, a custom algorithm was developed to measure the roughness of 3D surfaces. This algorithm was validated and used to quantify cartilage surface roughness changes as a function of time post-surgery.

RESULTS

MMT surgery resulted in significantly greater cartilage damage and subchondral bone sclerosis with the damage increasing in both severity and area from 1- to 3-weeks post-surgery. Analysis of rendered 3D surfaces could accurately distinguish early changes in joints developing OA, detecting significant increases of 45% and 124% in surface roughness at 1- and 3-weeks post-surgery respectively.

CONCLUSION

Disease progression in the MMT model progresses sequentially through changes in the cartilage articular surface, extracellular matrix composition, and then osteophyte mineralization and subchondral bone sclerosis. Cartilage surface roughness is a quantitative, early indicator of degenerative joint disease in small animal OA models and can potentially be used to evaluate therapeutic strategies.