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

Efficacy and safety of culture-expanded, mesenchymal stem/stromal cells for the treatment of knee osteoarthritis: a systematic review protocol

Background

Osteoarthritis is a progressive multifactorial condition of the musculoskeletal system with major symptoms including pain, loss of function, damage of articular cartilage and other tissues in the affected area. Knee osteoarthritis imposes major individual and social burden, especially with the cost and complexity of surgical interventions. Mesenchymal stem/stromal cells have been indicated as a treatment for degenerative musculoskeletal conditions given their capacity to differentiate into tissues of the musculoskeletal system.

Methods

A systematic search will be conducted in Medline, Embase, Cochrane Library, Scopus and relevant trial databases of English, Japanese, Korean, German, French, Italian, Spanish and Portuguese language papers published or in press to June 2018, with no restrictions on publication year applied. References will be screened and assessed for eligibility by two independent reviewers as per PRISMA guidelines. Cohort, cross-sectional or case controlled studies will be included for the analysis. Data extraction will be conducted using a predefined template and quality of evidence assessed. Statistical summaries and meta-analyses will be performed as necessary.

Discussion

Results will be published in relevant peer-reviewed scientific journals and presented at national or international conferences by the investigators.

Trial registration

The protocol was registered on the PROSPERO international prospective register of systematic reviews prior to commencement, CRD42018091763.

Electronic supplementary material

The online version of this article (10.1186/s13018-019-1070-8) contains supplementary material, which is available to authorized users.

Histopathological Evaluation of Orthopedic Medical Devices: The State-of-the-art in Animal Models, Imaging, and Histomorphometry Techniques

Orthopedic medical devices are continuously evolving for the latest clinical indications in craniomaxillofacial, spine, trauma, joint arthroplasty, sports medicine, and soft tissue regeneration fields, with a variety of materials from new metallic alloys and ceramics to composite polymers, bioresorbables, or surface-treated implants. There is great need for qualified medical device pathologists to evaluate these next generation biomaterials, with improved biocompatibility and bioactivity for orthopedic applications, and a broad range of knowledge is required to stay abreast of this ever-changing field. Orthopedic implants require specialized imaging and processing techniques to fully evaluate the bone-implant interface, and the pathologist plays an important role in determining the proper combination of histologic processing and staining for quality slide production based on research and development trials and validation. Additionally, histomorphometry is an essential part of the analysis to quantify tissue integration and residual biomaterials. In this article, an overview of orthopedic implants and animal models, as well as pertinent insights for tissue collection, imaging, processing, and slide generation will be provided with a special focus on histopathology and histomorphometry evaluation.

Histopathological changes in the infrapatellar fat pad in an experimental rabbit model of early patellofemoral osteoarthritis

BACKGROUND

The purpose of this study was to characterise the histopathological changes in the infrapatellar fat pad (IPFP) in the early stage of patellofemoral osteoarthritis (PFOA).

METHODS

Sixty-four New Zealand white rabbits were randomly divided into experimental (n = 24), sham (n = 16), and control groups (n = 24). In the experimental group, denoted as the patellar ligament uneven shortening group (US group), the patellar ligament (PL) was folded eight millimetres and sutured. After eight weeks, all animals were euthanised, and magnetic resonance imaging (MRI) evaluation, wet IPFP weight measurement, and histopathological and immunohistochemistry analysis were performed to analyse the histopathological changes in the IPFPs.

RESULTS

The maximum cross-sectional area (CSA) of the IPFPs in the sagittal position of MRI in the control group, sham group, and US group were 45.50 ± 7.19 mm², 45.88 ± 6.60 mm² (vs. control group, P = 0.907), and 53.83 ± 8.24 mm² (vs. control group, P = 0.015; vs. sham group, P = 0.035), respectively. The MRI intensity of the IPFPs in the control group, sham group, and US group were 115.53 ± 28.85, 108.53 ± 26.73 (vs. control group, P = 0.589), and 154.52 ± 18.48 (vs. control group, P = 0.002; vs. sham group, P = 0.002), respectively. The wet weight of the IPFPs in the control group, sham group, and US group were 0.32 ± 0.05 g, 0.32 ± 0.04 g (vs. control group, P = 0.895), and 0.38 ± 0.06 g (vs. control group, P = 0.017; vs. sham group, P = 0.033), respectively. The Osteoarthritis Research Society International (OARSI) scores of the IPFPs in the US group were 6.00 ± 1.91, which was higher than the scores of 2.50 ± 2.02 (P < 0.001) in the control group and of 2.75 ± 1.67 (P = 0.001) in the sham group.

CONCLUSIONS

The histopathological changes of the IPFPs as determined via MRI and microscopic structure appeared to occur much earlier than cartilage damage in PFOA. Furthermore, detecting and treating the IPFP changes may offer aid in the diagnosis and treatment of PFOA.

Shockwave Targeting on Subchondral Bone Is More Suitable than Articular Cartilage for Knee Osteoarthritis

Our study compared the effects of extracorporeal shockwave therapy (ESWT) on the subchondral bone and the articular cartilage in the treatment of early osteoarthritis (OA) of rat knee. The rats were divided into 5 groups which included Sham group, Meniscus group (ESWT applied on medial meniscus), OA group (arthrotomy and medial menisectomy (MMx) and anterior cruciate ligament transection (ACLT), T(M) group (arthrotomy and MMx and ACLT followed by ESWT on medial tibial subchondral bone) and Articular cartilage group (arthrotomy and MMx and ACLT followed by ESWT on medial articular cartilage). Evaluations included the pathological changes of the synovium, articular cartilage and subchondral bone, and compared with ESWT on the meniscus, medial tibial subchondral bone and articular cartilage. The ESWT (0.25 mJ/mm² and 800 impulses) did not cause any damages on the cartilage of the meniscus and the tissue of the joint when compared with Sham group. Among the treatment of osteoarthritic groups (OA, T(M) and Articular cartilage groups), T(M) group showed significant in pathological examination, micro-CT analysis, cartilage grading score and grading of synovium changes by compared with OA and Articular cartilage groups (P < 0.05) in the treatment of early OA knee. In immunohistochemical analysis, T(M) group significantly increased the expression of TGF-β1 but reduced DMP-1, MMP-13 and ADAMTS-5 in the cartilage by compared with OA group and Articular cartilage group (P < 0.05). Our results showed that subchondral bone was an excellent target than articular cartilage for ESWT on early knee osteoarthritis.

Enhanced repair of meniscal hoop structure injuries using an aligned electrospun nanofibrous scaffold combined with a mesenchymal stem cell-derived tissue engineered construct

Damage to the meniscal hoop structure results in loss of biomechanical function, which potentially leads to the extrusion of the meniscus from the weight bearing area. However, there have been no established, effective treatments for such injuries. The purpose of this study was to investigate the applicability of cell-seeded nanofibrous scaffolds to repair the damaged meniscal hoop structure along with the prevention of subsequent cartilage degeneration using a rabbit model. Meniscal radial defects (5 mm width) in the medial meniscus were treated by wrapping and suturing with either an aligned electrospun nanofibrous scaffold alone or a scaffold combined with a tissue engineered construct (TEC) derived from synovial mesenchymal stem cells (MSCs), with the scaffold fiber direction matching that of the meniscal circumferential fibers. The MSC-based TEC-combined nanofibrous scaffolds contributed significantly to the prevention of meniscal extrusion and exerted a chondroprotective effect, compared with either scaffold alone or the untreated control groups. Also, meniscal defects treated with such TEC-combined nanofibrous scaffolds were consistently repaired with a fibrocartilaginous tissue. In this study, we have demonstrated the feasibility of a combined TEC-nanofibrous scaffold to repair the meniscal hoop structure, and prevent the progression to cartilage degeneration, as a potential tissue engineering method.

Intra-Articular Injection of Alginate-Microencapsulated Adipose Tissue-Derived Mesenchymal Stem Cells for the Treatment of Osteoarthritis in Rabbits

We investigated the effects of intra-articular injections of alginate-microencapsulated adipose tissue-derived mesenchymal stem cells (ASCs) during osteoarthritis (OA) development in a rabbit model of anterior cruciate ligament transection (ACLT). We induced OA in mature New Zealand white rabbits by bilateral ACLT. Stifle joints were categorised into four groups according to intra-articular injection materials. Alginate microbeads and microencapsulated ASCs were prepared using the vibrational nozzle technology. Two weeks after ACLT, the rabbits received three consecutive weekly intra-articular injections of 0.9% NaCl, alginate microbeads, ASCs, or microencapsulated ASCs, into each joint. Nine weeks after ACLT, we euthanised the rabbits and collected bilateral femoral condyles for macroscopic, histological, and immunohistochemical analyses. Macroscopic evaluation using the modified OA Research Society International (OARSI) score and total cartilage damage score showed that cartilage degradation on the femoral condyle was relatively low in the microencapsulated-ASC group. Histological analysis of the lateral femoral condyles indicated that microencapsulated ASCs had significant chondroprotective effects. Immunohistochemically, the expression of MMP-13 after the articular cartilage damage was relatively low in the microencapsulated-ASC-treated stifle joints. During the development of experimental OA, as compared to ASCs alone, intra-articular injection of microencapsulated ASCs significantly decreased the progression and extent of OA.

Histological findings in TMJ treated with high condilectomy for internal derangement

Intra-Articular Temporo-Mandibular Disorders (TMD) are characterized by displacement of the disc that causes the condyles to slip back over the disc thus resulting in TMJ discal damage and erosion of the condyle's bone. The etiology of temporomandibular disorder (TMD) is multidimensional: biomechanical, neuromuscular, bio-psychosocial and biological factors may contribute to the disorder. The study involved 46 joints in 27 patients with a diagnosis of Intra-Articular Temporo-Mandibular Disorders (TMD) according to Axis I of Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) for Clinical and Research Applications and underwent surgery between 2011 and 2014. Patients were divided into three groups. Group 1 were included patients with Disc Displacement (DD) without reduction without limited opening, Group 2 patients with DD without reduction with limited opening. Finally, Group 3 included patients with Degenerative Joint Disease (DJD) TMD. In all cases, diagnosis of Intra-Articular Temporo-Mandibular Disorders (TMD) was confirmed by pre-operative examination (clinical, MRI and/or CT scan). Tissue specimens were obtained from all 50 joints for histopathology. The aim of this study was to analyse histological features of the surgical specimens obtained from patients with Intra-Articular Temporo-Mandibular Disorders who underwent surgery and assess the association with clinical findings and imaging. Preliminary results show in Group 1, fibrocartilage is preserved and regular, there are isolated outbreaks of bone resorption and focal sclerosis. In Groups 2 and 3 fibrocartilages are irregular and thickness varies widely and sclerosis is more pronounced. In early stages of TMD, the disc antero-medial displacement might play a fundamental role in the etiopathogenesis that can became an irreversible joint damage thus leading to a wide spectrum of articular symptoms and signs in TMD (Cohen et al., 2014; Hagandora and Almarza, 2012; Nah, 2012).

Emodin ameliorates cartilage degradation in osteoarthritis by inhibiting NF-κB and Wnt/β-catenin signaling in-vitro and in-vivo

The overproduction of MMPs (matrix metalloproteinases) and members of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) protein family plays an important role in the pathogenesis of osteoarthritis (OA). The potential of selective MMPs or ADAMTS inhibitors as chemopreventive agents for OA has been demonstrated in several studies. In this study, we investigated the protective effects of emodin (1,3,8-trihydroxy-6-methylanthaquinone), isolated from the root of Rheum palmatum L., in the inhibition of MMP and ADAMTS expression in both rat chondrocytes and an animal model of OA. The expression of MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, aggrecan, and collagen II mRNA and protein in interleukin-1beta (IL-1β)-induced rat chondrocytes was followed by quantitative real-time PCR and western blot. The activation of the NF-κB and Wnt/β-catenin pathways by IL-1β was assessed by western blot. The in vivo effects of emodin were evaluated by intra-articular injection in rats in an experimental model of OA induced by anterior cruciate ligament transection. Emodin dose-dependently down-regulated the expression of MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5 at both the mRNA and protein level in IL-1β-stimulated rat chondrocytes. In addition, the IL-1β-induced activation of NF-κB and Wnt signals was attenuated by emodin, as determined by western blotting. The intra-articular injection of emodin in a rat OA model ameliorated OA progression, as determined in morphological and histological analyses in vivo. Taken together, our findings demonstrate that emodin is a promising therapeutic agent for the prevention and treatment of OA.

Early detection of osteoarthritis in rabbits using MRI with a double-contrast agent

BACKGROUND

Articular cartilage degeneration has been evaluated by magnetic resonance imaging (MRI). However, this method has several problems, including its time-consuming nature and the requirement of a high magnetic field or specialized hardware. The purpose of this study was to sequentially assess early degenerative changes in rabbit knee articular cartilage using MRI with a new double-contrast agent.

METHODS

We induced osteoarthritis (OA) in the right knee of rabbits by anterior cruciate ligament transection and partial medial meniscectomy. Proton density-weighted images and T₂-calculated images were obtained before and after contrast agent injection into the knee. The signal intensity ratio (SIR) values on the proton density-weighted images were calculated by dividing the signal intensity of the articular cartilage by that of joint fluid. Six rabbits were examined using MRI at 2 (designated 2-w OA) and 4 weeks (4-w OA) after the operation. Histological examination was performed 4 weeks after the operation. One rabbit was histologically examined 2 weeks after the operation. The control consisted of six rabbits that were not subjected to the operation. The SIR values, T₂ values and the thicknesses of the cartilage of the 2-w OA, 4-w OA and the control before and after contrast agent injection were analyzed. The Mankin score and OARSI (Osteoarthritis Research Society International) score were used for the histological evaluation.

RESULTS

Significant differences in the SIR and T₂ values of the medial and lateral condyles of the femur were found between the control and the 4-w OA only after contrast agent injection. No significant differences were found in the SIR and T₂ values before contrast agent injection between the control, the 2-w OA and 4-w OA. The thickness of the articular cartilage revealed no significant differences. In the histological assessment, the Mankin score and OARSI score sequentially increased from the control to the 4-w OA.

CONCLUSION

We evaluated the SIR and T₂ values of the knees in a rabbit OA model and a control model using a new double-contrast agent. MRI with this agent enabled OA detection earlier than using conventional MRI.

Short-Term Homing of Hyaluronan-Primed Cells: Therapeutic Implications for Osteoarthritis Treatment

The evaluation of key factors modulating cell homing following injection can provide new insights in the comprehension of unsolved biological questions about the use of cell therapies for osteoarthritis (OA). The main purpose of this in vivo study was to investigate the biodistribution of an intra-articular injection of mesenchymal stromal cells (MSCs) and bone marrow concentrate (BMC) in a rabbit OA model and whether the additional use of sodium hyaluronate (HA) could modulate their migration and delay joint degeneration. OA was surgically induced in adult male New Zealand rabbits. A group of animals was used to test the biodistribution of labeled cells alone or with HA at 7 and 14 days to investigate cell migration. The efficacy of treatments was evaluated in other experimental groups at 2 months. Histology and immunohistochemistry for markers identifying anabolic and catabolic processes in the cartilage and meniscus, or macrophage subset population in the synovial membrane, were performed. Kruskal-Wallis test, followed by post hoc Dunn's test, and Spearman's rank-order correlation method were used. MSCs and BMC preferentially migrate toward tissue areas showing OA features in the meniscus and cartilage and in detail near inflammatory zones in the synovial membrane. The combination with HA contributed to boost cell migration toward articular cartilage. In general, both labeled cells combined with HA were found near cell cluster and fissures in the cartilage and meniscus, respectively, and close to areas of synovial membrane showing mainly anti-inflammatory macrophages. A promotion of joint repair was observed at different levels for all treatments, although BMC-HA treatment resulted as the best strategy to support joint repair. This last, displayed a good protein expression of type II collagen in the cartilage, as well as the presence of anti-inflammatory macrophages in the synovial membrane at 2 months from the treatment. Studies tracking cell biodistribution indicate that priming progenitor cells with HA modulated cell homing favoring not only attachment but also their integration within articular cartilage.

Toxicology Evaluation of Drugs Administered via Uncommon Routes: Intranasal, Intraocular, Intrathecal/Intraspinal, and Intra-Articular

As the need for nasal, ocular, spinal, and articular therapeutic compounds increases, toxicology assessments of drugs administered via these routes play an important role in human safety. This symposium outlined the local and systemic evaluation to support safety during the development of these drugs in nonclinical models with some case studies. Discussions included selection of appropriate species for the intended route; conducting nonclinical studies that closely mimic the intended use with adequate duration; functional assessment, if deemed necessary; evaluation of local tissues with special histological staining procedure; and evaluations of safety margins based on local and systemic toxicity.

Sustained intra-cartilage delivery of low dose dexamethasone using a cationic carrier for treatment of post traumatic osteoarthritis

Disease-modifying osteoarthritis drugs (DMOADs) should reach their intra-tissue target sites at optimal doses for clinical efficacy. The dense, negatively charged matrix of cartilage poses a major hindrance to the transport of potential therapeutics. In this work, electrostatic interactions were utilised to overcome this challenge and enable higher uptake, full-thickness penetration and enhanced retention of dexamethasone (Dex) inside rabbit cartilage. This was accomplished by using the positively charged glycoprotein avidin as nanocarrier, conjugated to Dex by releasable linkers. Therapeutic effects of a single intra-articular injection of low dose avidin-Dex (0.5 mg Dex) were evaluated in rabbits 3 weeks after anterior cruciate ligament transection (ACLT). Immunostaining confirmed that avidin penetrated the full cartilage thickness and was retained for at least 3 weeks. Avidin-Dex suppressed injury-induced joint swelling and catabolic gene expression to a greater extent than free Dex. It also significantly improved the histological score of cell infiltration and morphogenesis within the periarticular synovium. Micro-computed tomography confirmed the reduced incidence and volume of osteophytes following avidin-Dex treatment. However, neither treatment restored the loss of cartilage stiffness following ACLT, suggesting the need for a combinational therapy with a pro-anabolic factor for enhancing matrix biosynthesis. The avidin dose used caused significant glycosaminoglycan (GAG) loss, suggesting the use of higher Dex : avidin ratios in future formulations, such that the delivered avidin dose could be much less than that shown to affect GAGs. This charge-based delivery system converted cartilage into a drug depot that could also be employed for delivery to nearby synovium, menisci and ligaments, enabling clinical translation of a variety of DMOADs.

Injectable nanohydroxyapatite-chitosan-gelatin micro-scaffolds induce regeneration of knee subchondral bone lesions

Subchondral bone has been identified as an attractive target for KOA. To determine whether a minimally invasive micro-scaffolds could be used to induce regeneration of knee subchondral bone lesions, and to examine the protective effect of subchondral bone regeneration on upper cartilage, a ready-to-use injectable treatment with nanohydroxyapatite-chitosan-gelatin micro-scaffolds (HaCGMs) is proposed. Human-infrapatellar-fat-pad-derived adipose stem cells (IPFP-ASCs) were used as a cellular model to examine the osteo-inductivity and biocompatibility of HaCGMs, which were feasibly obtained with potency for multi-potential differentiations. Furthermore, a subchondral bone lesion model was developed to mimic the necrotic region removing performed by surgeons before sequestrectomy. HaCGMs were injected into the model to induce regeneration of subchondral bone. HaCGMs exhibited desirable swelling ratios, porosity, stiffness, and bioactivity and allowed cellular infiltration. Eight weeks after treatment, assessment via X-ray imaging, micro-CT imaging, and histological analysis revealed that rabbits treated with HaCGMs had better subchondral bone regeneration than those not treated. Interestingly, rabbits in the HaCGM treatment group also exhibited improved reservation of upper cartilage compared to those in other groups, as shown by safranin O-fast green staining. Present study provides an in-depth demonstration of injectable HaCGM-based regenerative therapy, which may provide an attractive alternative strategy for treating KOA.

Single intra-articular injection of fluvastatin-PLGA microspheres reduces cartilage degradation in rabbits with experimental osteoarthritis

Statins are cholesterol-lowering drugs that inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a rate-limiting enzyme of the mevalonate pathway. The anti-inflammatory effect of statins has been reported in recent years. The present study investigated therapeutic effects of the local administration of statin in osteoarthritis (OA). We assessed clinically used statins and selected fluvastatin for further experimentation, as it showed potent anabolic and anti-catabolic effects on human OA chondrocytes. To achieve controlled intra-articular administration of statin, we developed an intra-articular injectable statin using poly(lactic-co-glycolic acid) (PLGA) as a drug delivery system (DDS). The release profile of the statin was evaluated in vitro. Finally, therapeutic effects of fluvastatin-loaded PLGA microspheres (FLU-PLGA) were tested in a rabbit OA model. Rabbit knees were divided into four subgroups: group 1-A, PLGA-treated group; group 1-B, PLGA contralateral saline control group; group 2-A, FLU-PLGA-treated group; and group 2-B, FLU-PLGA contralateral saline control group. Histological analysis 5 weeks after intra-articular injection revealed that OARSI scores were lower in group 2-A. No significant differences in OARSI scores were observed between groups 1-A, 1-B, and 2-B. This study indicates that a single intra-articular injection of fluvastatin-loaded PLGA microspheres could be a novel therapeutic approach for treating patients with OA. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2465-2475, 2017.

Chitosan in viscosupplementation: in vivo effect on rabbit subchondral bone

Background

To investigate the effect of intra-articular injection of Chitosan (Cs) added to hyaluronic acid (HA) on subchondral bone during osteoarthritis (OA), microarchitectural parameters and mineral density were measured in a rabbit model of early OA. A novel hybrid hydrogel adding reacetylated Cs of fungal origin to HA was compared to high molecular weight HA commercial formulation.

Method

Eighteen rabbits underwent unilateral anterior cruciate ligament transection (ACLT) and were divided into three groups (Saline-group, HA-group and Hybrid-group) depending on the intra-articular injection compound. Eight contralateral knees were used as non-operated controls (Contralateral-group). Micro-computed tomography was performed six weeks post-ACLT to study subchondral bone microarchitectural parameters and mineral density at an early stage of OA development.

Results

Cartilage thickness mean value was reduced only in Saline-group compared to Contralateral-group. When the Hybrid-group was compared to Saline-group, subchondral bone microarchitectural parameters (trabecular thickness and trabecular bone volume fraction) were significantly changed; subchondral bone plate and trabecular bone mineral densities (bone mineral density and tissue mineral density) were reduced. When the Hybrid-group was compared to HA-group, subchondral bone microarchitectural parameters (subchondral plate thickness and trabecular thickness) and trabecular bone mineral densities (bone mineral density and tissue mineral density) were significantly decreased.

Conclusion

Conclusion: Compared to HA alone, the novel hybrid hydrogel, constituted of Cs added to HA, enhanced microarchitectural parameters and mineral density changes, leading to subchondral bone loss in a rabbit model of early experimental OA.

A Preclinical Assessment of Early Continuous Passive Motion and Treadmill Therapeutic Exercises for Generating Chondroprotective Effects After Anterior Cruciate Ligament Rupture

BACKGROUND

Anterior cruciate ligament (ACL) injury is a well-known risk factor for the development of posttraumatic osteoarthritis (PTOA). However, whether using continuous passive motion (CPM) with or without additional treadmill exercise (TRE) in early ACL injury might provide chondroprotective effects and further decrease the risk of PTOA has yet to be determined.

HYPOTHESIS

CPM may offer an enhanced chondroprotective effect, but TRE may attenuate that effect due to the mechanical stress on the joint and inflammatory cytokines in the joint.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty adult New Zealand White male rabbits were randomly allocated to sedentary (SED), CPM, TRE, or CPM+TRE groups. Each rabbit underwent an ACL transection (ACLT) on the right knee, with the contralateral knee used as an internal control (sham). The 4 joint surfaces (ie, medial and lateral femoral condyles and tibial plateaus) were evaluated 4 weeks after surgery for gross appearance, histological characteristics, and quantitative osteoarthritis (OA) scores.

RESULTS

Overall, at the end of testing, the CPM group experienced the best protective therapeutic effects in all compartments. In gross appearance, CPM resulted in normal articular surfaces, while the TRE and SED groups exhibited surface abrasion. Histological analysis showed significant differences in articular cartilage status. The CPM group had significantly better histological OA scores ( P < .01), corresponding to the smoothest cartilage surface and sound chondrocyte and collagen arrangement. This group also showed abundant glycosaminoglycan (GAG) content and a sound growth microenvironment, with significantly lower expression levels of the inflammatory cytokine tumor necrosis factor α and the apoptotic marker caspase 3. In contrast, the TRE and SED groups showed several features of damage: distinct graded cartilage abrasion; damaged collagen fibers, corresponding to noticeable collagen type X (osteoarthritic cartilage); reduced cartilage thickness; fewer cartilaginous cells; and the appearance of chondrocyte clusters. These groups also showed loss of GAG, corresponding to higher levels of inflammatory cytokines and apoptosis of articular chondrocytes. Furthermore, the CPM+TRE group displayed visible pathological changes in the superficial cartilage, indicating that early loading exercise may contribute to osteoarthritis. The sham treatment showed no difference in the changes in all compartments between groups.

CONCLUSION

Immediate CPM therapy produces a superior in situ microenvironment for reducing the occurrence of PTOA after ACL injury without reconstruction in rabbits.

CLINICAL RELEVANCE

These data suggest that immediate application of CPM therapy may be necessary to create a sound microenvironment in joints and possibly to decrease the risk of PTOA without or while awaiting ACL reconstruction. In contrast, both early active loading exercise and inactivity lead to the development of PTOA.

Effects of a viscosupplementation therapy on rabbit menisci in an anterior cruciate ligament transection model of osteoarthritis

The aim of this study was to evaluate the morphological, microstructural, and mechanical effects of a viscosupplementation therapy on rabbit menisci at an early stage of osteoarthritis (OA). Anterior cruciate ligament transection (ACLT) was performed in twelve male New-Zealand White rabbits on the right knee joint. Six of these twelve rabbits received a mono intra-articular injection of high molecular weight hyaluronic acid (HA) two weeks after ACLT. Six additional healthy rabbits served as controls. Medial menisci were removed from all right knees (n=18) six weeks after ACLT and were graded macroscopically. Indentation-relaxation tests were performed in the anterior and posterior regions of the menisci. Collagen fiber organization and glycosaminoglycan (GAG) content were assessed by biphotonic confocal microscopy and histology, respectively. Viscosupplementation significantly (p=0.002) improved the surface integrity of the medial menisci compared to the operated non-treated group. Moreover, the injection seems to have an effect on the GAG distribution in the anterior region of the menisci. However, the viscoelastic properties of both operated groups were similar and significantly lower than those of the healthy group, which was explained by their modified collagen fiber organization. They displayed disruption of the tie fibers due to structural alterations of the superficial layers from which they emanate, leading to modifications in the deep zone. To conclude, the viscosupplementation therapy prevents macroscopic lesions of the menisci, but it fails to restore their collagen fiber organization and their viscoelastic properties. This finding supports the role of this treatment in improving the lubrication over the knee.

Comparison between two different experimental models of osteoarthritis in rabbits. Intra-articular collagenase injection and anterior cruciate ligament transection

PURPOSE:

To compare two different experimental models of osteoarthritis in rabbits: intra-articular collagenase injection and anterior cruciate ligament transection.

METHODS:

Ten adult rabbits were randomly divided in two groups: COLL (collagenase group) and ACLT (anterior cruciate ligament transection). The COLL group was treated with 0.5 ml collagenase solution (2mg collagenase/0.5 ml sterile PBS), and the ACTL group was subjected to anterior cruciate ligament. After six and twelve weeks, respectively, the animals in the COLL and ACTL groups were euthanized. The gross appearance and histological examinations conducted in the cartilage articular surface was blindly scored according to the criteria developed by Yoshimi et al. (1994) and Mankin et al. (1971), respectively.

RESULTS:

The gross morphologic observation, macroscopic score and histological examinations have demonstrated that the ACTL group presented the highest scores, and lesions more severe than those in the COLL group.

CONCLUSIONS:

Both methods, anterior cruciate ligament transection and collagenase, applied to the stifle joint of the rabbits have effectively induced degenerative changes in the cartilage tissue, through statistically significant analysis (p≤0.05). The ACTL method has presented more severe lesions.

The biomechanical and histological effects of posterior cruciate ligament rupture on the medial tibial plateau

Background

The objective of this study was to investigate the biomechanical and histological effects of the posterior cruciate ligament (PCL) on the medial tibial plateau.

Methods

A total of 12 cadaveric human knee specimens were collected and grouped as follows: the PCL intact group (n = 12), the anterolateral bundle rupture group (n = 6), the postmedial bundle rupture group (n = 6), and the PCL rupture group (n = 12). The strain on the anterior, middle, and posterior parts of the medial tibial plateau with an axial loading force at different flexion angles was measured and analyzed, respectively. Forty-eight rabbits were chosen for animal study: surgery was performed on the one side of each rabbit randomly (experimental group), while the other side was taken as control (control group). Every 12 rabbits were culled at each of the four selected time points to collect the medial tibial plateau for morphological and histological observation.

Results

The PCL rupture, either partial or complete, may generate an abnormal load on all the parts of the medial tibial plateau with axial loading at all positions. Noticeable time-dependent degenerative histological changes of the medial tibial plateau were observed in the rabbit models of PCL rupture. Compared with the control group, all the PCL rupture groups exhibited a higher expression of the matrix metalloproteinase-7 (MMP-7) and the tissue inhibitors of metalloproteinase-1 (TIMP-1) at all the time points.

Conclusions

Either partial or complete PCL rupture may generate an abnormal load on all the parts of the medial tibial plateau with axial loading at all the positions and may cause cartilage degeneration on the medial tibial plateau.

Time-dependent loss of mitochondrial function precedes progressive histologic cartilage degeneration in a rabbit meniscal destabilization model

The goals of this work were to characterize progression of osteoarthritic cartilage degeneration in a rabbit medial meniscus destabilization (MMD) model and then to use the model to identify pre-histologic disruptions in chondrocyte metabolism under chronically elevated joint contact stresses in vivo. To characterize PTOA progression, 24 rabbits received either MMD or sham surgery. Limb loading was analyzed preoperatively and at regular postoperative intervals using a Tekscan pressure-sensitive walkway. Animals were euthanized 8 (n = 8 MMD; n = 8 sham) or 26 weeks (n = 8 MMD) postoperatively for histological cartilage evaluation by an objective, semi-automated Mankin scoring routine. To examine pre-histologic pathology, MMD was performed on an additional 20 rabbits, euthanized 1 (n = 9) or 4 weeks (n = 10) postoperatively. Chondrocytes were harvested fresh for measurement of mitochondrial function, an intracellular indicator of pathology after mechanical injury. Both MMD and sham surgery caused slight decreases in limb loading which returned to preoperative levels after 2 weeks. Histologically apparent cartilage damage progressed from 8 to 26 weeks after MMD. Changes in chondrocyte respiration were variable at 1 week, but by 4 weeks postoperatively chondrocyte mitochondrial function was significantly reduced. Many human injuries that lead to PTOA are relatively mild, and the cell-level mechanisms leading to disease remain unclear. We have documented PTOA progression in an animal model of subtle joint injury under continued use, and demonstrated that this model provides a realistic environment for investigation of multi-stage cellular pathology that develops prior to overt tissue degeneration and which could be targeted for disease modifying treatments. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:590-599, 2017.

Collagenous Ultrastructure of the Discoid Meniscus: A Transmission Electron Microscopy Study

BACKGROUND

The collagen ultrastructure of the discoid lateral meniscus (DLM) has not been precisely defined.

PURPOSE

To investigate the ultrastructure of the DLM, focusing on its collagen fibers, and to compare the collagen net architecture between intact and torn DLMs using the Collagen Meniscal Architecture (CMA) scoring system.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Thirty specimens were taken from 30 patients with a diagnosis of a complete DLM using a 1-piece technique. The collagen ultrastructure of the DLMs was assessed with transmission electron microscopy. To evaluate the meniscal ultrastructure, the degree of collagen disruption, intrafibrillar edema, loss of banding, degree of collagen packing, and fibril size variability were assessed and graded from 1 (normal) to 3 (severe disarray) according to the CMA scoring system. The DLM specimens were divided into 3 groups according to the intrasubstance tear: the intact group (group I) had no tear; the simple tear group (group S) had a radial, longitudinal, or horizontal tear; and the complicated tear group (group C) had a complicated horizontal tear. Intact normal meniscus specimens (group N) were used as the control group.

RESULTS

There were 10 specimens in group I, 8 in group S, 12 in group C, and 13 in group N. In group I, there were 5 grade 1 and 5 grade 2 menisci; group S had 2 grade 1, 3 grade 2, and 3 grade 3 menisci; group C had 1 grade 1, 4 grade 2, and 7 grade 3 menisci; and group N had 4 grade 1, 7 grade 2, and 2 grade 3 menisci. A significant difference in the CMA score was observed between the 4 groups ( P = .009). The median CMA score was significantly lower in group I (2; range, 1-4) than in group S (4; range, 2-7) ( P = .041) and group C (4.25; range, 1.5-7) ( P = .018). No significant difference was found between groups S, C, and N.

CONCLUSION

Variability existed in the collagen ultrastructure of the DLM, and some DLMs showed a nearly normal ultrastructural pattern. The degree of density and disorganization of the collagen architecture in the DLM was related to the tear.

CLINICAL RELEVANCE

The study results might provide a histological background for partial meniscectomy in the treatment of a symptomatic DLM.

Osteoarthritis in the Knee Joints of Göttingen Minipigs after Resection of the Anterior Cruciate Ligament? Missing Correlation of MRI, Gene and Protein Expression with Histological Scoring

Introduction

The Göttingen Minipig (GM) is used as large animal model in articular cartilage research. The aim of the study was to introduce osteoarthritis (OA) in the GM by resecting the anterior cruciate ligament (ACLR) according to Pond and Nuki, verified by histological and magnetic resonance imaging (MRI) scoring as well as analysis of gene and protein expression.

Materials and Methods

The eight included skeletally mature female GM were assessed after ACLR in the left and a sham operation in the right knee, which served as control. 26 weeks after surgery the knee joints were scanned using a 3-Tesla high-field MR tomography unit with a 3 T CP Large Flex Coil. Standard proton-density weighted fat saturated sequences in coronal and sagittal direction with a slice thickness of 3 mm were used. The MRI scans were assessed by two radiologists according to a modified WORMS-score, the X-rays of the knee joints by two evaluators. Osteochondral plugs with a diameter of 4mm were taken for histological examination from either the main loading zone or the macroscopic most degenerated parts of the tibia plateau or condyle respectively. The histological sections were blinded and scored by three experts according to Little et al. Gene expression analysis was performed from surrounding cartilage. Expression of adamts4, adamts5, acan, col1A1, col2, il-1ß, mmp1, mmp3, mmp13, vegf was determined by qRT-PCR. Immunohistochemical staining (IH) of Col I and II was performed. IH was scored using a 4 point grading (0—no staining; 3-intense staining).

Results and Discussion

Similar signs of OA were evident both in ACLR and sham operated knee joints with the histological scoring result of the ACLR joints with 6.48 ± 5.67 points and the sham joints with 6.86 ± 5.84 points (p = 0.7953) The MRI scoring yielded 0.34 ± 0.89 points for the ACLR and 0.03 ± 0.17 for the sham knee joints. There was no correlation between the histological and MRI scores (r = 0.10021). The gene expression profiles as well as the immunohistochemical findings showed no significant differences between ACLR and sham knee joints. In conclusion, both knee joints showed histological signs of OA after 26 weeks irrespective of whether the ACL was resected or not. As MRI results did not match the histological findings, MRI was obviously unsuitable to diagnose the OA in GM. The analysis of the expression patterns of the 10 genes could not shed light on the question, whether sham operation also induced cartilage erosion or if the degeneration was spontaneous. The modified Pond-Nuki model may be used with reservation in the adult minipig to induce an isolated osteoarthritis.

Safety Studies for Use of Adipose Tissue-Derived Mesenchymal Stromal/Stem Cells in a Rabbit Model for Osteoarthritis to Support a Phase I Clinical Trial

Adipose‐derived mesenchymal stem cells (AMSCs) offer potential as a therapeutic option for clinical applications in musculoskeletal regenerative medicine because of their immunomodulatory functions and capacity for trilineage differentiation. In preparation for a phase I clinical trial using AMSCs to treat patients with osteoarthritis, we carried out preclinical studies to assess the safety of human AMSCs within the intra‐articular joint space. Culture‐expanded human AMSCs grown in human platelet‐lysate were delivered via intra‐articular injections into normal healthy rabbit knees and knees at risk for the development of osteoarthritis after bilateral medial anterior hemimeniscectomy. Treatment outcomes and safety were evaluated by assessing the general health, function, and behavior of the animals. Joint tissues were analyzed by x‐ray, magnetic resonance imaging, and histopathology. Intra‐articular AMSC therapy was well tolerated in this study. We did not observe adverse systemic reactions, nor did we find evidence of damage to intra‐articular joint tissues. Thus, the data generated in this study show a favorable safety profile for AMSCs within the joint space in support of a phase I clinical trial evaluating the clinical utility of AMSCs to treat osteoarthritis. Stem Cells Translational Medicine2017;6:910–922

A novel rabbit model of early osteoarthritis exhibits gradual cartilage degeneration after medial collateral ligament transection outside the joint capsule

Though many surgical animal models have been used to induce osteoarthritis (OA) of the knee joint, they always open the capsule of the joint. Any surgical procedures that incises the capsule may cause inflammation, pain, and possibly altered gait. One common disadvantage of these surgically induced animal models is that they may affect the initial structures and synovial fluid in joint. These animal models may not be suitable for research into synovial fluid changes during early OA. This study aimed to create an animal model of early OA by resecting the medial collateral ligament (MCL) outside of the capsule. At 1, 2, 3, 4, 5 and 6 weeks after surgery, eight knees from each group were harvested. The joint gap was measured on posteroanterior radiographs after MCL-transection (MCLT). Gross examination and histological analysis were performed to evaluate cartilage damage to the medial femoral condyles, and knee joints were scanned using a Micro-CT system. The MCLT group experienced early stage OA from 3 to 6 weeks according to the histological scores. IL-6, MMP-1 and MMP-13 content in the synovial fluid were higher after MCLT than anterior cruciate ligament transection (ACLT) at 1 and 2 weeks.

Exploiting endogenous fibrocartilage stem cells to regenerate cartilage and repair joint injury

Tissue regeneration using stem cell-based transplantation faces many hurdles. Alternatively, therapeutically exploiting endogenous stem cells to regenerate injured or diseased tissue may circumvent these challenges. Here we show resident fibrocartilage stem cells (FCSCs) can be used to regenerate and repair cartilage. We identify FCSCs residing within the superficial zone niche in the temporomandibular joint (TMJ) condyle. A single FCSC spontaneously generates a cartilage anlage, remodels into bone and organizes a haematopoietic microenvironment. Wnt signals deplete the reservoir of FCSCs and cause cartilage degeneration. We also show that intra-articular treatment with the Wnt inhibitor sclerostin sustains the FCSC pool and regenerates cartilage in a TMJ injury model. We demonstrate the promise of exploiting resident FCSCs as a regenerative therapeutic strategy to substitute cell transplantation that could be beneficial for patients suffering from fibrocartilage injury and disease. These data prompt the examination of utilizing this strategy for other musculoskeletal tissues.

Olive and grape seed extract prevents post-traumatic osteoarthritis damages and exhibits in vitro anti IL-1β activities before and after oral consumption

Polyphenols exert a large range of beneficial effects in the prevention of age-related diseases. We sought to determine whether an extract of olive and grape seed standardized according to hydroxytyrosol (HT) and procyanidins (PCy) content, exerts preventive anti-osteoathritic effects. To this aim, we evaluated whether the HT/PCy mix could (i) have in vitro anti-inflammatory and chondroprotective actions, (ii) exert anti-osteoarthritis effects in two post-traumatic animal models and (iii) retain its bioactivity after oral administration. Anti-inflammatory and chondroprotective actions of HT/PCy were tested on primary cultured rabbit chondrocytes stimulated by interleukin-1 beta (IL-1β). The results showed that HT/PCy exerts anti-inflammatory and chondroprotective actions in vitro. The preventive effect of HT/PCy association was assessed in two animal models of post-traumatic OA in mice and rabbits. Diet supplementation with HT/PCy significantly decreased the severity of post-traumatic osteoarthritis in two complementary mice and rabbit models. The bioavailability and bioactivity was evaluated following gavage with HT/PCy in rabbits. Regular metabolites from HT/PCy extract were found in sera from rabbits following oral intake. Finally, sera from rabbits force-fed with HT/PCy conserved anti-IL-1β effect, suggesting the bioactivity of this extract. To conclude, HT/PCy extract may be of clinical significance for the preventive treatment of osteoarthritis.

Inhibition of cartilage degradation and suppression of PGE2 and MMPs expression by pomegranate fruit extract in a model of posttraumatic osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is characterized by cartilage degradation in the affected joints. Pomegranate fruit extract (PFE) inhibits cartilage degradation in vitro. The aim of this study was to determine whether oral consumption of PFE inhibits disease progression in rabbits with surgically induced OA.

METHODS

OA was surgically induced in the tibiofemoral joints of adult New Zealand White rabbits. In one group, animals were fed PFE in water for 8 wk postsurgery. In the second group, animals were fed PFE for 2 wk before surgery and for 8 wk postsurgery. Histologic assessment and scoring of the cartilage was per Osteoarthritis Research Society International guidelines. Gene expression and matrix metalloproteinases (MMP) activity were determined using quantitative reverse transcriptase polymerase chain reaction and fluorometric assay, respectively. Interleukin (IL)-1 β, MMP-13, IL-6, prostaglandin (PG)E₂, and type II collagen (COL2A1) levels in synovial fluid/plasma/culture media were quantified using enzyme-linked immunosorbent assay. Expression of active caspase-3 and poly (ADP-ribose) polymerase p85 was determined by immunohistochemistry. Effect of PFE and inhibitors of MMP-13, mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB was studied in IL-1 β-stimulated rabbit articular chondrocytes.

RESULTS

Safranin-O-staining and chondrocyte cluster formation was significantly reduced in the anterior cruciate ligament transaction plus PFE fed groups. Expression of MMP-3, MMP-9, and MMP-13 mRNA was higher in the cartilage of rabbits given water alone but was significantly lower in the animals fed PFE. PFE-fed rabbits had lower IL-6, MMP-13, and PGE₂ levels in the synovial fluid and plasma, respectively, and showed higher expression of aggrecan and COL2A1 mRNA. Significantly higher numbers of chondrocytes were positive for markers of apoptosis in the joints of rabbits with OA given water only compared with those in the PFE-fed groups. PFE pretreatment significantly reduced IL-1 β induced IL-6 and MMPs expression in rabbit articular chondrocytes. These effects were also mimicked using MMP-13, MAPK, and NF-κB inhibitors in IL-1 β-stimulated rabbit chondrocytes. In an in vitro activity assay, PFE blocked the activity of MMP-13. Like MAPK and NF-κB inhibitors, PFE was also effective in inhibiting IL-1 β-induced PGE₂ production in rabbit chondrocytes. PFE also reversed the inhibitory effect of IL-1β on COL2A1 mRNA and protein expression in IL-1 β-stimulated rabbit chondrocytes.

CONCLUSION

The present data highlight the chondroprotective effects of PFE oral consumption in a model of posttraumatic OA and suggest that PFE-derived compounds may have potential value in the management of OA.

Viscoelastic properties of rabbit osteoarthritic menisci: A correlation with matrix alterations

The aim of this study was to evaluate the effect of early osteoarthritis (OA) on the viscoelastic properties of rabbit menisci and to correlate the mechanical alterations with the microstructural changes. Anterior Cruciate Ligament Transection (ACLT) was performed in six male New-Zealand White rabbits on the right knee joint. Six healthy rabbits served as controls. Menisci were removed six weeks after ACLT and were graded macroscopically. Indentation-relaxation tests were performed in the anterior and posterior regions of the medial menisci. The collagen fibre organization and glycosaminoglycan (GAG) content were assessed by biphotonic confocal microscopy and histology, respectively. OA menisci displayed severe macroscopic lesions compared with healthy menisci (p=0.009). Moreover, the instantaneous and equilibrium moduli, which were 2.9±1.0MPa and 0.60±0.18MPa in the anterior region of healthy menisci, respectively, decreased significantly (p=0.03 and p=0.004, respectively) in OA menisci by 55% and 57%, respectively, indicating a global decrease in meniscal stiffness in this region. The equilibrium modulus alone decreased significantly (p=0.04) in the posterior region, going from 0.60±0.18MPa to 0.26±012MPa. This induced a loss of tissue elasticity. These mechanical changes were associated in the posterior region with a structural disruption of the superficial layers, from which the tie fibres emanate, and with a decrease in the GAG content in the anterior region. Consequently, the circumferential collagen fibres of the deep zone were dissociated and the collagen bundles were less compact. Our results demonstrate the strong meniscal modifications induced by ACLT at an early stage of OA and highlight the relationship between structural and chemical matrix alterations and mechanical properties.

Joint instability leads to long-term alterations to knee synovium and osteoarthritis in a rabbit model

OBJECTIVES

Joint instability is believed to promote early osteoarthritic changes in the knee. Inflammatory reactions are associated with cartilage degradation in osteoarthritis (OA) but their possible synergistic or additive effects remain largely unexplored. The goal of the present study was to investigate the in vivo effects of Botulinum Toxin A (BTX-A) induced joint instability on intraarticular alterations in an otherwise intact rabbit knee joint model.

METHODS

Ten 1-year-old female New Zealand White rabbits (average 5.7 kg, range 4.8-6.6 kg) were randomly assigned to receive three monthly unilateral intramuscular injections of BTX-A (experimental group), or no treatment (control group). After 90 days, all knees were analyzed for specific mRNA levels using RT-qPCR. The synovium and cartilage tissue was assessed for histological alterations using the OARSI scoring system.

RESULTS

Cartilage and synovial histology showed significant higher OARSI scores in the BTX-A group animals compared to the untreated controls and contralateral limbs. There were no differences between the untreated control and the contralateral experimental limbs. Gene expression showed significant elevations for collagen I, collagen III, nitric oxide, TGF-β, IL-1 and IL-6 compared to the healthy controls.

CONCLUSION

BTX-A induced joint instability in a muscle weakness model uniquely leads to alterations in gene expression and histological changes in the synovial membranes and cartilage in otherwise intact knee joints. These results lead to the conclusion that joint instability may promote an inflammatory intraarticular milieu, thereby contributing to the development of OA.

Histopathological analyses of murine menisci: implications for joint aging and osteoarthritis

OBJECTIVE

To establish a standardized protocol for histopathological assessment of murine menisci that can be applied to evaluate transgenic, knock-out/in, and surgically induced OA models.

METHODS

Knee joints from C57BL/6J mice (6-36 months) as well as from mice with surgically-induced OA were processed and cut into sagittal sections. All sections included the anterior and posterior horns of the menisci and were graded for (1) surface integrity, (2) cellularity, (3) Safranin-O staining distribution and intensity. Articular cartilage in the knee joints was also scored.

RESULTS

The new histopathological grading system showed good inter- and intra-class correlation coefficients. The major age-related changes in murine menisci in the absence of OA included decreased Safranin O staining intensity, abnormal cell distribution and the appearance of acellular areas. Menisci from mice with surgically-induced OA showed severe fibrillations, partial/total loss of tissue, and calcifications. Abnormal cell arrangements included both regional hypercellularity and hypocellularity along with hypertrophy and cell clusters. In general, the posterior horns were less affected by age and OA.

CONCLUSION

A new standardized protocol and histopathological grading system has been developed and validated to allow for a comprehensive, systematic evaluation of changes in aging and OA-affected murine menisci. This system was developed to serve as a standardized technique and tool for further studies in murine meniscal pathophysiology models.

Osteoclasts are recruited to the subchondral bone in naturally occurring post-traumatic equine carpal osteoarthritis and may contribute to cartilage degradation

The role of osteoclasts in osteochondral degeneration in osteoarthritis (OA) has rarely been investigated in spontaneous disease or animal models of OA.

OBJECTIVE

The objectives of the current study were to investigate osteoclast density and location in post-traumatic OA (PTOA) and control specimens from racehorses.

METHOD

Cores were harvested from a site in the equine third carpal bone, that undergoes repetitive, high intensity loading. Histological and immunohistochemical (Cathepsin K and Receptor-activator of Nuclear Factor kappa-β ligand (RANKL)) stained sections were scored (global and subregional) and the osteoclast density calculated. The cartilage histological scores were compared with osteoclast density and RANKL scores.

RESULTS

There was a greater density of osteoclasts in PTOA samples and they were preferentially located in the subchondral bone plate. RANKL scores positively correlated to the scores of cartilage degeneration and the osteoclast density. The relationship between hyaline articular cartilage RANKL score and osteoclast density was stronger than that of the subchondral bone RANKL score suggesting that cartilage RANKL may have a role in recruiting osteoclasts. The RANKL score in the articular calcified cartilage correlated with the number of microcracks also suggesting that osteoclasts recruited by RANKL may contribute to calcified cartilage degeneration in PTOA.

CONCLUSION

Our results support the hypothesis that osteoclasts are recruited during the progression of spontaneous equine carpal PTOA by cartilage RANKL, contributing to calcified cartilage microcracks and focal subchondral bone loss.

The infrapatellar fat pad is affected by injury induced inflammation in the rabbit knee: use of dexamethasone to mitigate damage

OBJECTIVE AND DESIGN

The health of the infrapatellar fat pad (IFP) has been linked to pain, joint inflammation, and the onset of post-traumatic osteoarthritis. Thus, early inflammation effects on the IFP could have long term sequelae on joint integrity. This study was designed to characterize the natural history of the IFP in a model of surgically induced knee injury and inflammation, and to test the efficacy of one intra-articular (IA) administration of dexamethasone (DEX) immediately following surgery.

METHODS

An IA bone drill hole injury to the rabbit knee was conducted and immediately treated with DEX (n = 12). Early and late post-surgical time-points were investigated (48 h and 9 weeks) and the outcome measures were analysis of IFP histology, mRNA levels for relevant molecules, and protein levels for a subset of cytokines. Data were analyzed against a surgical control (injury without treatment; n = 12), a surgical sham (capsular incision only; n = 12), and normal control (n = 6).

TREATMENT

Single IA injection of DEX (0.5 mg/kg), administered at the completion of surgery.

RESULTS

IFPs from injured joints exhibited significantly increased cellularity and early fibrosis at 48 h post surgery. While the histological inflammation from a capsular incision alone resolved, knee injured animals progressed to a significantly more fibrotic IFP by 9 weeks. DEX significantly lowered histological scores at 48 h, but not at the 9 weeks. DEX did not influence mRNA levels for IL-1β, 6, and 8, however, protein analysis indicated that IL-8 levels were lower in DEX treated joints. DEX resulted in significantly elevated expression of mRNA for MCP-1, leptin, and VEGF.

CONCLUSION

One IA administration of a glucocorticoid appears to mitigate the initial inflammation within the joint, but is not sufficient to protect the joint to 9 weeks post-surgery.

Animal models of osteoarthritis: classification, update, and measurement of outcomes

Osteoarthritis (OA) is one of the most commonly occurring forms of arthritis in the world today. It is a debilitating chronic illness causing pain and immense discomfort to the affected individual. Significant research is currently ongoing to understand its pathophysiology and develop successful treatment regimens based on this knowledge. Animal models have played a key role in achieving this goal. Animal models currently used to study osteoarthritis can be classified based on the etiology under investigation, primary osteoarthritis, and post-traumatic osteoarthritis, to better clarify the relationship between these models and the pathogenesis of the disease. Non-invasive animal models have shown significant promise in understanding early osteoarthritic changes. Imaging modalities play a pivotal role in understanding the pathogenesis of OA and the correlation with pain. These imaging studies would also allow in vivo surveillance of the disease as a function of time in the animal model. This review summarizes the current understanding of the disease pathogenesis, invasive and non-invasive animal models, imaging modalities, and pain assessment techniques in the animals.

Establishment of a rabbit model to study the influence of advanced glycation end products accumulation on osteoarthritis and the protective effect of pioglitazone

OBJECTIVE

To investigate the role of advanced glycation end products (AGEs) in cartilage degeneration in vivo and determine the influence of the peroxisome proliferator-activated receptor-γ (PPARγ) agonist pioglitazone on AGEs-induced osteoarthritis (OA) in a rabbit model.

DESIGN

Thirty-two rabbits were separated into four groups (n = 8 each) and received 500 μL of 123, 350, or 1000 mmol/L D-ribose or Phosphate buffered saline (PBS) solution administered to the right stifle joint via intra-articular injection twice a week. All the rabbits ran 500 m on treadmills every day. Another 16 rabbits were administered 1000 mmol/L D-ribose and divided into 2 groups (n = 8) that received either placebo or pioglitazone administered orally at 20 mg/kg/day. Eight weeks later, cartilage damage was evaluated macroscopically, histologically, and biochemically.

RESULTS

Artificially increasing the AGEs level and exercise load resulted in cartilage damage and dose-dependent downregulation of PPARγ expression. The efficacy of pioglitazone treatment was tested in a rabbit OA model, and a clear chondroprotective effect was revealed by macro- and microscopic assessments.

CONCLUSION

Elevating AGEs in rabbits can accelerate the articular cartilage degradation that occurs with physical exercise, and pioglitazone can reduce the severity of the AGEs-induced OA in a rabbit model.

Three-Dimensional Quantitative Morphometric Analysis (QMA) for In Situ Joint and Tissue Assessment of Osteoarthritis in a Preclinical Rabbit Disease Model

This work utilises advances in multi-tissue imaging, and incorporates new metrics which define in situ joint changes and individual tissue changes in osteoarthritis (OA). The aims are to (1) demonstrate a protocol for processing intact animal joints for microCT to visualise relevant joint, bone and cartilage structures for understanding OA in a preclinical rabbit model, and (2) introduce a comprehensive three-dimensional (3D) quantitative morphometric analysis (QMA), including an assessment of reproducibility. Sixteen rabbit joints with and without transection of the anterior cruciate ligament were scanned with microCT and contrast agents, and processed for histology. Semi-quantitative evaluation was performed on matching two-dimensional (2D) histology and microCT images. Subsequently, 3D QMA was performed; including measures of cartilage, subchondral cortical and epiphyseal bone, and novel tibio-femoral joint metrics. Reproducibility of the QMA was tested on seven additional joints. A significant correlation was observed in cartilage thickness from matching histology-microCT pairs. The lateral compartment of operated joints had larger joint space width, thicker femoral cartilage and reduced bone volume, while osteophytes could be detected quantitatively. Measures between the in situ tibia and femur indicated an altered loading scenario. High measurement reproducibility was observed for all new parameters; with ICC ranging from 0.754 to 0.998. In conclusion, this study provides a novel 3D QMA to quantify macro and micro tissue measures in the joint of a rabbit OA model. New metrics were established consisting of: an angle to quantitatively measure osteophytes (σ), an angle to indicate erosion between the lateral and medial femoral condyles (ρ), a vector defining altered angulation (λ, α, β, γ) and a twist angle (τ) measuring instability and tissue degeneration between the femur and tibia, a length measure of joint space width (JSW), and a slope and intercept (m, Χ) of joint contact to demonstrate altered loading with disease progression, as well as traditional bone and cartilage and histo-morphometry measures. We demonstrate correlation of microCT and histology, sensitive discrimination of OA change and robust reproducibility.

Gene therapy for human osteoarthritis: principles and clinical translation

INTRODUCTION

Osteoarthritis (OA) is the most prevalent chronic joint disease. Its key feature is a progressive articular cartilage loss. Gene therapy for OA aims at delivering gene-based therapeutic agents to the osteoarthritic cartilage, resulting in a controlled, site-specific, long-term presence to rebuild the damaged cartilage.

AREAS COVERED

An overview is provided of the principles of gene therapy for OA based on a PubMed literature search. Gene transfer to normal and osteoarthritic cartilage in vitro and in animal models in vivo is reviewed. Results from recent clinical gene therapy trials for OA are discussed and placed into perspective.

EXPERT OPINION

Recombinant adeno-associated viral (rAAV) vectors enable to directly transfer candidate sequences in human articular chondrocytes in situ, providing a potent tool to modulate the structure of osteoarthritic cartilage. However, few preclinical animal studies in OA models have been performed thus far. Noteworthy, several gene therapy clinical trials have been carried out in patients with end-stage knee OA based on the intraarticular injection of human juvenile allogeneic chondrocytes overexpressing a cDNA encoding transforming growth factor-beta-1 via retroviral vectors. In a recent placebo-controlled randomized trial, clinical scores were improved compared with placebo. These translational results provide sufficient reason to proceed with further clinical testing of gene transfer protocols for the treatment of OA.

Large animal models in experimental knee sports surgery: focus on clinical translation

Large animal models play a crucial role in sports surgery of the knee, as they are critical for the exploration of new experimental strategies and the clinical translation of novel techniques. The purpose of this contribution is to provide critical aspects of relevant animal models in this field, with a focus on paediatric anterior cruciate ligament (ACL) reconstruction, high tibial osteotomy, and articular cartilage repair. Although there is no single large animal model strictly replicating the human knee joint, the sheep stifle joint shares strong similarities. Studies in large animal models of paediatric ACL reconstruction identified specific risk factors associated with the different surgical techniques. The sheep model of high tibial osteotomy is a powerful new tool to advance the understanding of the effect of axial alignment on the lower extremity on specific issues of the knee joint. Large animal models of both focal chondral and osteochondral defects and of osteoarthritis have brought new findings about the mechanisms of cartilage repair and treatment options. The clinical application of a magnetic device for targeted cell delivery serves as a suitable example of how data from such animal models are directly translated into in clinical cartilage repair. As novel insights from studies in these translational models will advance the basic science, close cooperation in this important field of clinical translation will improve current reconstructive surgical options and open novel avenues for regenerative therapies of musculoskeletal disorders.

Single intra-articular dexamethasone injection immediately post-surgery in a rabbit model mitigates early inflammatory responses and post-traumatic osteoarthritis-like alterations

Despite surgical reconstruction of the anterior cruciate ligament, a significant number of patients will still develop post-traumatic osteoarthritis (PTOA). Our objective was to determine if mitigating aspects of the acute phase of inflammation following a defined knee surgery with a single administration of a glucocorticoid could prevent the development of PTOA-like changes within an established rabbit model of surgically induced PTOA. An early and late post-surgical time-point was investigated in this study (48 h and 9 weeks post-surgery) in which the following groups were repeated (each n=6, for a total of 24 rabbits per time-point, and 48 rabbits used in the study): control (age/sex matched), sham (arthrotomy), drill injury (arthrotomy+two drill holes to a non-cartilaginous area of the femoral notch), and drill injury+single intra-articular (IA) injection of dexamethasone (DEX). At 48 h post-surgery, DEX treatment significantly lowered the mRNA levels for a subset of pro-inflammatory mediators, and significantly lowered the histological grade. Nine weeks post surgery, DEX treatment significantly lowered the histological scores (presented as effect size) for synovium (3.8), lateral femoral condyle (3.9), and lateral tibial cartilage (5.1) samples. Thus, DEX likely acts to prevent injury induced inflammation that could contribute to subsequent joint damage.

Comprehensive analysis of translational osteochondral repair: Focus on the histological assessment

Articular cartilage guarantees for an optimal functioning of diarthrodial joints by providing a gliding surface for smooth articulation, weight distribution, and shock absorbing while the subchondral bone plays a crucial role in its biomechanical and nutritive support. Both tissues together form the osteochondral unit. The structural assessment of the osteochondral unit is now considered the key standard procedure for evaluating articular cartilage repair in translational animal models. The aim of this review is to give a detailed overview of the different methods for a comprehensive evaluation of osteochondral repair. The main focus is on the histological assessment as the gold standard, together with immunohistochemistry, and polarized light microscopy. Additionally, standards of macroscopic, non-destructive imaging such as high resolution MRI and micro-CT, biochemical, and molecular biological evaluations are addressed. Potential pitfalls of analysis are outlined. A second focus is to suggest recommendations for osteochondral evaluation.

Targets, models and challenges in osteoarthritis research

Osteoarthritis is a chronic degenerative disorder of the joint and represents one of the most common diseases worldwide. Its prevalence and severity are increasing owing to aging of the population, but treatment options remain largely limited to painkillers and anti-inflammatory drugs, which only provide symptomatic relief. In the late stages of the disease, surgical interventions are often necessary to partially restore joint function. Although the focus of osteoarthritis research has been originally on the articular cartilage, novel findings are now pointing to osteoarthritis as a disease of the whole joint, in which failure of different joint components can occur. In this Review, we summarize recent progress in the field, including data from novel ‘omics’ technologies and from a number of preclinical and clinical trials. We describe different in vitro and in vivo systems that can be used to study molecules, pathways and cells that are involved in osteoarthritis. We illustrate that a comprehensive and multisystem approach is necessary to understand the complexity and heterogeneity of the disease and to better guide the development of novel therapeutic strategies for osteoarthritis.

Efficacy study of two novel hyaluronic acid-based formulations for viscosupplementation therapy in an early osteoarthrosic rabbit model

Viscosupplementation (VS) is a therapy for osteoarthrosis (OA) consisting of repetitive intra-articular injections of hyaluronic acid (HA). It is known to be clinically effective in relieving pain and increasing joint mobility by restoring joint homeostasis. In this study, the effects of two novel HA-based VS hydrogel formulations were assessed and challenged against a pure HA commercial formulation for the first time and this in a rabbit model of early OA induced by anterior cruciate ligament transection (ACLT). The first formulation tested was a hybrid hydrogel composed of HA and reacetylated chitosan, a biopolymer considered to be chondroprotective, assembled thanks to an ionic shielding. The second formulation consisted of a novel HA polymer grafted with antioxidant molecules (HA-4AR) aiming at decreasing OA oxidative stress and increasing HA retention time in the articulation. ACLT was performed on rabbits in order to cause structural changes comparable to traumatic osteoarthrosis. The protective effects of the different formulations were observed on the early phase of the pathology in a full randomized and blinded manner. The cartilage, synovial membrane, and subchondral bone were evaluated by complementary investigation techniques such as gross morphological scoring, scanning electron microscopy, histological scoring, and micro-computed tomography were used. In this study, ACLT was proven to successfully reproduce early OA articular characteristics found in humans. HA and HA-4AR hydrogels were found to be moderately protective for cartilage as highlighted by μCT. The HA-4AR was the only formulation able to decrease synovial membrane hypertrophy occurring in OA. Finally, the hybrid HA-reacetylated chitosan hydrogel surprisingly led to increased subchondral bone remodeling and cartilage defect formation. This study shows significant effects of two innovative HA modification strategies in an OA rabbit model, which warrant further studies toward more effective viscosupplementation formulations.

Topographical investigation of changes in depth-wise proteoglycan distribution in rabbit femoral articular cartilage at 4 weeks after transection of the anterior cruciate ligament

In this study, we explore topographical changes in proteoglycan distribution from femoral condylar cartilage in early osteoarthritis, acquired from both the lateral and medial condyles of anterior cruciate ligament transected (ACLT) and contralateral (CNTRL) rabbit knee joints, at 4 weeks post operation. Four sites across the cartilage surface in a parasagittal plane were defined across tissue sections taken from femoral condyles, and proteoglycan (PG) content was quantified using digital densitometry. The greatest depth-wise change in PG content due to an ACLT (compared to the CNTRL group) was observed anteriorly (site C) from the most weight-bearing location within the lateral compartment. In the medial compartment, the greatest change was observed in the most weight-bearing location (site B). The depth-wise changes in PG content were observed up to 48% and 28% depth from the tissue surface at these aforementioned sites, respectively (p < 0.05). The smallest depth-wise change in PG content was observed posteriorly (site A) from the most weight-bearing location within both femoral condyles (up to 20% and up to 5% depth from the tissue surface at lateral and medial compartments, respectively). This study gives further insight into how early cartilage deterioration progresses across the parasagittal plane of the femoral condyle.

Menisectomized miniature Vietnamese pigs develop articular cartilage pathology resembling osteoarthritis

Animal models have been used to understand the basic biology of osteoarthritis (OA) and have helped to identify new candidate biomarkers for the early diagnosis and treatment of this condition. Small animals cannot sufficiently mimic human diseases; therefore, large animal models are needed. Pigs have been used as models for human diseases because they are similar to humans in terms of their anatomy, physiology and genome. Hence, we analyzed articular cartilage and synovial membrane pathology in miniature Vietnamese pigs after a unilateral partial menisectomy and 20-day exercise regimen to determine if the pigs developed pathological characteristics similar to human OA. Histological and protein expression analysis of articular cartilage from menisectomized pigs revealed the following pathologic changes resembling OA: fibrillation, fissures, chondrocyte cluster formation, decrease in proteoglycan content and upregulation of the OA-associated proteins MMP-3, MMP-13, procaspase-3 and IL-1β. Moreover, histological analysis of synovial membrane revealed mild synovitis, characterized by hyperplasia, cell infiltration and neoangiogenesis. Pathological changes were not observed in the contralateral joints or the joints of sham-operated pigs. Further studies are required to validate such an OA model; however, our results can encourage the use of pigs to study early stages of OA physiopathology. Based on their similarities to humans, pigs may be useful for preclinical studies to identify new candidate biomarkers and novel treatments for OA.

Animal Models for Evaluation of Bone Implants and Devices

Bone implants and devices are a rapidly growing field within biomedical research, and implants have the potential to significantly improve human and animal health. Animal models play a key role in initial product development and are important components of nonclinical data included in applications for regulatory approval. Pathologists are increasingly being asked to evaluate these models at the initial developmental and nonclinical biocompatibility testing stages, and it is important to understand the relative merits and deficiencies of various species when evaluating a new material or device. This article summarizes characteristics of the most commonly used species in studies of bone implant materials, including detailed information about the relevance of a particular model to human bone physiology and pathology. Species reviewed include mice, rats, rabbits, guinea pigs, dogs, sheep, goats, and nonhuman primates. Ultimately, a comprehensive understanding of the benefits and limitations of different model species will aid in rigorously evaluating a novel bone implant material or device.

Effects of diacerein on cartilage and subchondral bone in early stages of osteoarthritis in a rabbit model

Background

Osteoarthritis is thought to be the most prevalent chronic and disabling joint disease in animals and humans. At present, there is no ideal treatment option. The aim of this study was to assess the effects of the treatment with oral diacerein on articular cartilage, synovial membrane and subchondral bone in an experimental rabbit model of osteoarthritis by micro-CT evaluation and histological analysis. To this purpose, osteoarthritis was surgically induced on one knee of 16 rabbits using the contralateral knee as healthy controls. Treatment was started three weeks later and lasted eight weeks. Animals were divided into two groups for treatment: Placebo (treated daily with oral saline) and diacerein (treated orally with 1.5 mg/kg/day of diacerein).

Results

Sample analysis revealed that this model induced osteoarthritis in the operated knee joint. Osteoarthritis placebo group showed a significant increase in non-calcified cartilage thickness and volume with respect to the control placebo group and important changes in the synovial membrane; whereas the parameters measured in subchondral bone remained unchanged. In the osteoarthritis diacerein-treated group the results showed an improvement with respect to the OA placebo group in all parameters, although the results were not statistically significant.

Conclusion

The results of this animal study suggested that the diacerein treatment for OA may be able to ameliorate the swelling and surface alterations of the cartilage and exert an anti-inflammatory effect on the synovial membrane, which might contribute to OA improvement, as well as an anabolic effect on subchondral trabecular bone.

Very early osteoarthritis changes sensitively fluid flow properties of articular cartilage

In this study, fibril-reinforced poroelastic (FRPE) modeling was used for rabbit knee after anterior cruciate ligament transection (ACLT) to assess how the mechanical properties of collagen, proteoglycans, and fluid in articular cartilage change in early osteoarthritis, and how site-specific these changes are. Unilateral ACLT was performed in eight skeletally mature, female New Zealand white rabbits. A separate control (CTRL) group consisted of knee joints of five non-operated rabbits. Animals were sacrificed at four weeks after ACLT and cartilage-on-bone samples from femoral groove, medial and lateral femoral condyles, and tibial plateaus were harvested. A stress-relaxation protocol in indentation geometry was applied and the FRPE model was fitted to the experimental force-time curve by minimizing the mean absolute error between experiment and simulation. The optimized parameters were: fibril network modulus (Ef), representing the collagen network; non-fibrillar matrix modulus (Enf), representing the PG matrix; and permeability (k), representing fluid flow. Permeability was increased significantly in the ACLT group compared to the CTRL group knees at all sites except for the medial tibial plateau. ACLT also caused a decrease in the Ef at all sites except for the medial and lateral tibial plateaus. The Enf of the ACLT group knees was altered only for the lateral femoral condyle. The results of this study suggest that early osteoarthritis primarily affects cartilage permeability and impairs the collagen network stiffness in a site-specific manner. These findings from early osteoarthritis indicate that fluid flow velocity in articular cartilage may change prior to quantifiable structural alterations in the tissue.