Comparison of differential biomarkers of osteoarthritis with and without posttraumatic injury in the Hartley guinea pig model

A synoptic literature review of animal models for investigating the biomechanics of knee osteoarthritis

Osteoarthritis (OA) is a common chronic disease largely driven by mechanical factors, causing significant health and economic burdens worldwide. Early detection is challenging, making animal models a key tool for studying its onset and mechanically-relevant pathogenesis. This review evaluate current use of preclinical in vivo models and progressive measurement techniques for analysing biomechanical factors in the specific context of the clinical OA phenotypes. It categorizes preclinical in vivo models into naturally occurring, genetically modified, chemically-induced, surgically-induced, and non-invasive types, linking each to clinical phenotypes like chronic pain, inflammation, and mechanical overload. Specifically, we discriminate between mechanical and biological factors, give a new explanation of the mechanical overload OA phenotype and propose that it should be further subcategorized into two subtypes, post-traumatic and chronic overloading OA. This review then summarises the representative models and tools in biomechanical studies of OA. We highlight and identify how to develop a mechanical model without inflammatory sequelae and how to induce OA without significant experimental trauma and so enable the detection of changes indicative of early-stage OA in the absence of such sequelae. We propose that the most popular post-traumatic OA biomechanical models are not representative of all types of mechanical overloading OA and, in particular, identify a deficiency of current rodent models to represent the chronic overloading OA phenotype without requiring intraarticular surgery. We therefore pinpoint well standardized and reproducible chronic overloading models that are being developed to enable the study of early OA changes in non-trauma related, slowly-progressive OA. In particular, non-invasive models (repetitive small compression loading model and exercise model) and an extra-articular surgical model (osteotomy) are attractive ways to present the chronic natural course of primary OA. Use of these models and quantitative mechanical behaviour tools such as gait analysis and non-invasive imaging techniques show great promise in understanding the mechanical aspects of the onset and progression of OA in the context of chronic knee joint overloading. Further development of these models and the advanced characterisation tools will enable better replication of the human chronic overloading OA phenotype and thus facilitate mechanically-driven clinical questions to be answered.

Molecular biomarker approaches to prevention of post-traumatic osteoarthritis

Up to 50% of individuals develop post-traumatic osteoarthritis (PTOA) within 10 years following knee-joint injuries such as anterior cruciate ligament rupture or acute meniscal tear. Lower-extremity PTOA prevalence is estimated to account for ≥12% of all symptomatic osteoarthritis (OA), or approximately 5.6 million cases in the USA. With knowledge of the inciting event, it might be possible to 'catch PTOA in the act' with sensitive imaging and soluble biomarkers and thereby prevent OA sequelae by early intervention. Existing biomarker data in the joint-injury literature can provide insights into the pathogenesis and early risk trajectory related to PTOA and can help to elucidate a research agenda for preventing or slowing the onset of PTOA. Non-traumatic OA and PTOA have many clinical, radiological and genetic similarities, and efforts to understand early risk trajectories in PTOA might therefore contribute to the identification and classification of early non-traumatic OA, which is the most prevalent form of OA.

3D T1 relaxation time measurements in an equine model of subtle post-traumatic osteoarthritis using MB-SWIFT

The aim of this study is to assess whether articular cartilage changes in an equine model of post-traumatic osteoarthritis (PTOA), induced by surgical creation of standard (blunt) grooves, and very subtle sharp grooves, could be detected with ex vivo T1 relaxation time mapping utilizing three-dimensional (3D) readout sequence with zero echo time. Grooves were made on the articular surfaces of the middle carpal and radiocarpal joints of nine mature Shetland ponies and osteochondral samples were harvested at 39 weeks after being euthanized under respective ethical permissions. T1 relaxation times of the samples (n = 8 + 8 for experimental and n = 12 for contralateral controls) were measured with a variable flip angle 3D multiband-sweep imaging with Fourier transform sequence. Equilibrium and instantaneous Young's moduli and proteoglycan (PG) content from OD of Safranin-O-stained histological sections were measured and utilized as reference parameters for the T1 relaxation times. T1 relaxation time was significantly (p < 0.05) increased in both groove areas, particularly in the blunt grooves, compared with control samples, with the largest changes observed in the superficial half of the cartilage. T1 relaxation times correlated weakly (Rs  ≈ 0.33) with equilibrium modulus and PG content (Rs  ≈ 0.21). T1 relaxation time in the superficial articular cartilage is sensitive to changes induced by the blunt grooves but not to the much subtler sharp grooves, at the 39-week timepoint post-injury. These findings support that T1 relaxation time has potential in detection of mild PTOA, albeit the most subtle changes could not be detected.

Knee Osteoarthritis Following Anterior Cruciate Ligament Reconstruction: Frequency, Contributory Elements, and Recent Interventions to Modify the Route of Degeneration

Half of the individuals who experience an anterior cruciate ligament reconstruction (ACLR) suffer from knee osteoarthritis (OA) 12-14 years later. Elements that make a contribution to the appearance of OA following ACLR are anomalous anterior tibial displacement and anomalous tibial rotation in the course of the stance phase of walking (exhibited in 85% of operated knees). Individuals who undergo an early ACLR (5 days on average following anterior cruciate ligament [ACL] breakage) have an inferior frequency of radiographically apparent tibiofemoral OA at 32-37 years of follow-up than individuals with ACL rupture who did not experience the procedure. Nevertheless, the percentage of symptomatic OA, radiographically apparent patellofemoral OA and knee symptoms are alike in both groups. At 15 years of follow-up, 23% of knees that experienced an anatomic ACLR suffer from OA, while this percentage augments to 44% if the ACLR was non-anatomic. Knees of individuals who experience ACLR need total knee arthroplasty at an earlier age than healthy knees. Intra-articular injections of interleukin-1 receptor antagonist and corticosteroids may reduce the risk of OA after ACLR.

α2-macroglobulin-rich serum as a master inhibitor of inflammatory factors attenuates cartilage degeneration in a mini pig model of osteoarthritis induced by “idealized” anterior cruciate ligament reconstruction

Post-traumatic osteoarthritis is a special type of osteoarthritis and a common disease, with few effective treatments available. α2-Macroglobulin (α2M) is important to chondral protection in post-traumatic osteoarthritis. However, its injection into xenogeneic joint cavities involves safety hazards, limiting clinical applications. Exploring serum α2M-enriching strategies and the therapeutic effect and mechanism of α2M-rich serum (α2MRS) autologous joint injection to treat post-traumatic osteoarthritis has significant value. In the present study, a unique filtration process was used to obtain α2MRS from human and mini pig serum. We evaluated the potential of α2MRS in protecting against post-surgery cartilage degeneration. We identify the potential of α2MRS in reducing the expression of inflammatory cytokines and factors that hasten cartilage degeneration in post-operative conditions leading to post-traumatic osteoarthritis. The potential of α2MRS was analyzed in interleukin-1β induced human chondrocytes and mini pig models. In the chondrocyte model, α2MRS significantly promoted human chondrocyte proliferation and reduced apoptosis and chondrocyte catabolic cytokine gene transcription and secretion. The anterior cruciate ligament autograft reconstruction model of mini pigs was randomized into groups, operated on, and injected with α2MRS or saline. The results showed that α2MRS injection significantly suppressed the levels of inflammatory factors, improved gait, and showed significantly lower cartilage degeneration than the groups that did not receive α2MRS injections. This study highlights the chondroprotective effects of α2MRS, elucidated its potential applications against cartilage degeneration, and could provide a basis for the clinical translation of α2MRS.

Small laboratory animal models of anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) injuries are common knee ligament injuries. While generally successful, ACL reconstruction that uses a tendon graft to stabilize the knee is still associated with a notable percentage of failures and long-term morbidities. Preclinical research that uses small laboratory species (i.e., mice, rats, and rabbits) to model ACL reconstruction are important to evaluate factors that can impact graft incorporation or posttraumatic osteoarthritis after ACL reconstruction. Small animal ACL reconstruction models are also used for proof-of-concept studies for the development of emerging biological strategies aimed at improving ACL reconstruction healing. The objective of this review is to provide an overview on the use of common small animal laboratory species to model ACL reconstruction. The review includes a discussion on comparative knee anatomy, technical considerations including types of tendon grafts employed amongst the small laboratory species (i.e., mice, rats, and rabbits), and common laboratory evaluative methods used to study healing and outcomes after ACL reconstruction in small laboratory animals. The review will also highlight common research questions addressed with small animal models of ACL reconstruction.

An Injectable Containing Morphine, Ropivacaine, Epinephrine, and Ketorolac Is Not Cytotoxic to Articular Cartilage Explants From Degenerative Knees

PURPOSE

The purpose of this study was to determine the effects of a multidrug injectate containing morphine, ropivacaine, epinephrine, and ketorolac, commonly referred to as the "Orthococktail," on cartilage tissue viability and metabolic responses using an established in vitro model.

METHODS

With institutional review board approval and informed patient consent, tissues normally discarded after total knee arthroplasty (TKA) were recovered. Full-thickness cartilage explants (n = 72, Outerbridge grade 1 to 3) were created and bisected. Paired explant halves were treated with either 1 mL Orthococktail or 1 mL of saline and cultured for 8 hours at 37°C, with 0.5 mL of the treatment being removed and replaced with tissue culture media every hour. Explants were cultured for 6 days, and media were changed and collected on days 3 and 6. After day 6, tissues were processed for cell viability, weighed, and processed for histologic grading. Outcome measures were compared for significant differences between treated and untreated samples.

RESULTS

There were no significant differences in cartilage viability between control and Orthococktail-treated samples across a spectrum of cartilage pathologies. Orthococktail treatment consistently resulted in a significant decrease in the release of PGE2, MCP-1, MMP-7, and MMP-8 on day 3 of culture and PGE2, MMP-3, MMP-7, and MMP-8 on day 6 of culture, compared with saline controls.

CONCLUSION

The results of the present study indicate that an Orthococktail injection composed of morphine, ropivacaine, epinephrine, and ketorolac is associated with a transient decrease in degradative and inflammatory mediators produced by more severely affected articular cartilage and may mitigate perioperative joint pain such that postoperative narcotic drug use could be reduced.

CLINICAL RELEVANCE

The Orthococktail solution used in this study may be a safe intraoperative, intra-articular injection option for patients undergoing joint arthroplasty and other joint preservation surgical procedures.

Tantalum Oxide Nanoparticles for the Quantitative Contrast-Enhanced Computed Tomography of Ex Vivo Human Cartilage: Assessment of Biochemical Composition and Biomechanics

Nanoparticle-based contrast agents, when used in concert with imaging modalities such as computed tomography (CT), enhance the visualization of tissues and boundary interfaces. However, the ability to determine the physiological state of the tissue via the quantitative assessment of biochemical or biomechanical properties remains elusive. We report the synthesis and characterization of tantalum oxide (Ta₂O₅) nanoparticle (NP) contrast agents for rapid, nondestructive, and quantitative contrast-enhanced computed tomography (CECT) to assess both the glycosaminoglycan (GAG) content and the biomechanical integrity of human metacarpal phalangeal joint (MCPJ) articular cartilage. Ta₂O₅ NPs 3-6 nm in diameter and coated with either nonionic poly(ethylene) glycol (PEG) or cationic trimethylammonium ligands readily diffuse into both healthy and osteoarthritic MCPJ cartilage. The CECT attenuation for the cationic and neutral NPs correlates with the glycosaminoglycan (GAG) content (R² = 0.8975, p < 0.05 and 0.7054, respectively) and the equilibrium modulus (R² = 0.8285, p < 0.05 and 0.9312, p < 0.05, respectively). The results highlight the importance of the surface charge and size in the design of NP agents for targeting and imaging articular cartilage. Further, nanoparticle CECT offers the visualization of both soft tissue and underlying bone unlike plain radiography, which is the standard for imaging bone in musculoskeletal diseases, and the ability to provide a real-time quantitative assessment of both hard and soft tissues to provide a comprehensive image of the disease stage, as demonstrated herein.

Inflammatory factors are crucial for the pathogenesis of post-traumatic osteoarthritis confirmed by a novel porcine model: "Idealized" anterior cruciate ligament reconstruction" and gait analysis

OBJECTIVE

To determine whether idealized anterior cruciate ligament reconstruction (IACL-R) restores normal gait features, and whether inflammatory factors are involved in the pathogenesisof post-traumatic osteoarthritis (PTOA).

METHODS

Fourteen mature female minipigs were allocated to a sham group (n = 7) or an IACL-R group (n = 7). Load asymmetry during gait was recorded using a pressure-sensing walkway measurement system to evaluate the gait features of the right knee joint before and after surgery. Inflammatory factors (including interleukin [IL]-1α, IL-1β, IL-2, IL-6, IL-8, IL-18, tumor necrosis factor-α, and granulocyte-macrophage colony-stimulating factor) in synovial fluid were measured using Luminex assays before and after surgery. Cartilage integrity and the subchondral bone plate of the right knee were evaluated using histology and imaging at 3 months postoperatively.

RESULTS

Swing time and stance time returned to their preoperative values on day 31, while maximum force, contact area, peak force ,and impulse returned to their preoperative values on day 45 after the surgery in the IACL-R group (P = 0.073, 0.053, 0.107, 0.052, 0.152, and 0.059, respectively).Thus, IACL-R restored normal gait. Compared with their preoperative concentrations, all tested inflammatory factors showed significantly increased concentrations in the synovial fluid in the IACL-R group, especially at 3, 7, and 15 days postoperatively. X-ray, computed tomography, magnetic resonance imaging, and histological data showed severe cartilage damage in the IACL-R model.

CONCLUSION

IACL-R restored normal gait features but caused significant cartilage damage, indicating that significantly elevated inflammatory factors maybe crucial for the pathogenesis of PTOA.

Primary Osteoarthritis Early Joint Degeneration Induced by Endoplasmic Reticulum Stress Is Mitigated by Resveratrol

Increasing numbers of people are living with osteoarthritis (OA) due to aging and obesity, creating an urgent need for effective treatment and preventions. Two top risk factors for OA, age and obesity, are associated with endoplasmic reticulum (ER) stress. The I-ERS mouse, an ER stress-driven model of primary OA, was developed to study the role of ER stress in primary OA susceptibility. The I-ERS mouse has the unique ability to induce ER stress in healthy adult articular chondrocytes and cartilage, driving joint degeneration that mimics early primary OA. In this study, ER stress-induced damage occurred gradually and stimulated joint degeneration with OA characteristics including increased matrix metalloproteinase activity, inflammation, senescence, chondrocyte death, decreased proteoglycans, autophagy block, and gait dysfunction. Consistent with human OA, intense exercise hastened and increased the level of ER stress-induced joint damage. Notably, loss of a critical ER stress response protein (CHOP) largely ameliorated ER stress-stimulated OA outcomes including preserving proteoglycan content, reducing inflammation, and relieving autophagy block. Resveratrol diminished ER stress-induced joint degeneration by decreasing CHOP, TNFα, IL-1β, MMP-13, pS6, number of TUNEL-positive chondrocytes, and senescence marker p16 INK4a. The finding, that a dietary supplement can prevent ER stressed-induced joint degeneration in mice, provides a preclinical foundation to potentially develop a prevention strategy for those at high risk to develop OA.

Assessment of the efficacy of intra-articular platelet rich plasma treatment in an ACLT experimental model by dynamic contrast enhancement MRI of knee subchondral bone marrow and MRI T2∗ measurement of articular cartilage

OBJECTIVE

The vascularization of subchondral bone plays a significant role in the progression of knee osteoarthritis (OA). Treatment with platelet-rich plasma (PRP) has positive effects on cartilage lesions. However, PRP's efficacy for subchondral bone marrow lesions and the relationship of these lesions to cartilage are still undiscovered. Therefore, our aims were first to longitudinally investigate the change in subchondral flow by dynamic contrast enhanced MRI and degeneration of cartilage by MRI T2∗ in an anterior cruciate transection rodent (ACLT) model, and second to examine changes in parameters after intra-articular PRP injection.

DESIGN

A 32-week investigation in 18 rats allocated to sham-control, ACLT with normal saline injection (ACLT + NS), and ACLT with PRP injection groups ended with histological evaluation. Another rat was used as a donor of allogenic PRP.

RESULTS

Compared to the sham-control group, the ACLT + NS group had higher subchondral blood volume A (0.051, 95% confidence interval: 0.009, 0.092) and lower venous washout kel (-0.030: -0.055, -0.005) from week 4; lower permeability kep from week 18 (-0.954: -1.339, -0.569); higher cartilage T2∗ values (1.803: 1.504, 2.102) reflecting collagen loss beginning at week 10. For the PRP treatment group, subchondral bone marrow A and cartilage T2∗ decreased from week 10. Histological results confirmed and were correlated with the MRI findings.

CONCLUSION

Subchondral hyper-perfusion plays a vital role in the pathogenesis of OA and was associated with cartilage degeneration. The efficacy of PRP can be observed from reduced perfusion and MRI T2∗ values.

Effects of in vivo cyclic compressive loading on the distribution of local Col2 and superficial lubricin in rat knee cartilage

This study aimed to examine the effects of an episode of in vivo cyclic loading on rat knee articular cartilage (AC) under medium-term observation, while also investigating relevant factors associated with the progression of post-traumatic osteoarthritis (PTOA). Twelve-week-old Wistar rats underwent one episode comprising 60 cycles of 20 N or 50 N dynamic compression on the right knee joint. Spatiotemporal changes in the AC after loading were evaluated using histology and immunohistochemistry at 3 days and 1, 2, 4, and 8 weeks after loading (n = 6 for each condition). Chondrocyte vitality was assessed at 1, 3, 6, and 12 hours after loading (n = 2 for each condition). A localized AC lesion on the lateral femoral condyle was confirmed in all subjects. The surface and intermediate cartilage in the affected area degenerated after loading, but the calcified cartilage remained intact. Expression of type II collagen in the lesion cartilage was upregulated after loading, whereas the superficial lubricin layer was eroded in response to cyclic compression. However, the distribution of superficial lubricin gradually recovered to the normal level 4 weeks after loading-induced injury. We confirmed that 60 repetitions of cyclic loading exceeding 20 N could result in cartilage damage in the rat knee. Endogenous repairs in well-structured joints work well to rebuild protective layers on the lesion cartilage surface, which may be the latent factor delaying the progression of PTOA.

The ankle cartilage cascade: incremental cartilage damage in the ankle joint

Level of evidence Editorial, Level V.

Lubricin in experimental and naturally occurring osteoarthritis: a systematic review

OBJECTIVE

Lubricin is increasingly being evaluated as an outcome measure in studies investigating post-traumatic and naturally occurring osteoarthritis. However, there are discrepancies in results, making it unclear as to whether lubricin is increased, decreased or unchanged in osteoarthritis. The purpose of this study was to review all papers that measured lubricin in joint injury or osteoarthritis in order to draw conclusions about lubricin regulation in joint disease.

DESIGN

A systematic search of the Pubmed, Web of Knowledge, and EBSCOhost databases for papers was performed. Inclusion criteria were in vivo studies that measured lubricin in humans or animals with joint injury, that investigated lubricin supplementation in osteoarthritic joints, or that described the phenotype of a lubricin knock-out model. A methodological assessment was performed.

RESULTS

Sixty-two studies were included, of which thirty-eight measured endogenous lubricin in joint injury or osteoarthritis. Nineteen papers found an increase or no change in lubricin and nineteen reported a decrease. Papers that reported a decrease in lubricin were cited four times more often than those that reported an increase. Fifteen papers described lubricin supplementation, and all reported a beneficial effect. Eleven papers described lubricin knock-out models.

CONCLUSIONS

The human literature reveals similar distributions of papers reporting increased lubricin as compared to decreased lubricin in osteoarthritis. The animal literature is dominated by reports of decreased lubricin in the rat anterior cruciate ligament transection model, whereas studies in large animal models report increased lubricin. Intra-articular lubricin supplementation may be beneficial regardless of whether lubricin increases or decreases in OA.

Less mechanical loading attenuates osteoarthritis by reducing cartilage degeneration, subchondral bone remodelling, secondary inflammation, and activation of NLRP3 inflammasome

Aims

Osteoarthritis (OA) is a disabling joint disorder and mechanical loading is an important pathogenesis. This study aims to investigate the benefits of less mechanical loading created by intermittent tail suspension for knee OA.

Methods

A post-traumatic OA model was established in 20 rats (12 weeks old, male). Ten rats were treated with less mechanical loading through intermittent tail suspension, while another ten rats were treated with normal mechanical loading. Cartilage damage was determined by gross appearance, Safranin O/Fast Green staining, and immunohistochemistry examinations. Subchondral bone changes were analyzed by micro-CT and tartrate-resistant acid phosphatase (TRAP) staining, and serum inflammatory cytokines were evaluated by enzyme-linked immunosorbent assay (ELISA).

Results

Our radiographs showed that joint space was significantly enlarged in rats with less mechanical loading. Moreover, cartilage destruction was attenuated in the less mechanical loading group with lower histological damage scores, and lower expression of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-5, matrix metalloproteinase (MMP)-3, and MMP-13. In addition, subchondral bone abnormal changes were ameliorated in OA rats with less mechanical loading, as reduced bone mineral density (BMD), bone volume/tissue volume (BV/TV), and number of osteophytes and osteoclasts in the subchondral bone were observed. Finally, the level of serum inflammatory cytokines was significantly downregulated in the less mechanical loading group compared with the normal mechanical loading group, as well as the expression of NACHT, LRR, and PYD domains-containing protein 3 (NLRP3), caspase-1, and interleukin 1β (IL-1β) in the cartilage.

Conclusion

Less mechanical loading alleviates cartilage destruction, subchondral bone changes, and secondary inflammation in OA joints. This study provides fundamental insights into the benefit of non-weight loading rest for patients with OA.

Cite this article: Bone Joint Res 2020;9(10):731–741.

MicroRNA-1 promotes cartilage matrix synthesis and regulates chondrocyte differentiation via post-transcriptional suppression of Ihh expression

Indian hedgehog signaling molecule (Ihh) is known to play critical roles in chondrogenesis and cartilage development. However, it remains largely unknown how Ihh is regulated during the process. Previous studies suggest that Ihh plays an important regulatory role in the growth and development of articular cartilage, but whether it is regulated by miRNAs is unclear. The present study aimed to investigate the effects of miR‑1 on chondrocyte differentiation and matrix synthesis, and to determine whether miR‑1 can regulate the Ihh signaling pathway. In the present study, the expression level of miR‑1 was altered via transfection of the miR‑1 mimic or inhibitor in mouse thorax chondrocytes, and the impact on chondrocyte phenotypes and Ihh expression was examined. Overexpression of miR‑1 promoted the expression of the matrix synthesis‑associated molecules collagen (Col)‑II and aggrecan, two key components in cartilage matrix. Conversely, overexpression of miR‑1 significantly downregulated the expression of chondrocyte differentiation markers Col‑X and matrix metallopeptidase 13. Moreover, overexpression of miR‑1 dose‑dependently inhibited endogenous Ihh expression, and an association was observed between miR‑1 and Ihh expression. The 3' untranslated region (UTR) of Ihh from various species contains two miR‑1 binding sites. Luciferase reporter assays indicated that miR‑1 post‑transcriptionally suppressed Ihh expression, which was dependent on the binding of miR‑1 to one of the two putative binding sites of the Ihh 3'UTR. Furthermore, via inhibition of Ihh expression, miR‑1 decreased the expression of molecules downstream of Ihh in the Hedgehog signaling pathway in mouse thorax chondrocytes. This study provided new insight into the molecular mechanisms of miR‑1 in regulating chondrocyte phenotypes via targeting the Ihh pathway.

Osteoarthritis and ACL Reconstruction-Myths and Risks

PURPOSE OF REVIEW

Anterior cruciate ligament (ACL) injury is one of the most common ligamentous injuries suffered by athletes participating in cutting sports. A common misperception is that ACL reconstruction can prevent osteoarthritis (OA). The goal of this paper is to review and discuss the contributing factors for the development of OA following ACL injury.

RECENT FINDINGS

There has been interesting new research related to ACL reconstruction. As understanding of knee biomechanics following ACL injury and reconstruction has changed over time, many surgeons have changed their surgical techniques to low anterior drilling to position their femoral tunnel in an attempt to place the ACL in a more anatomic position. Even with this change in the femoral tunnel position, 85% of knees following ACL reconstruction have abnormal tibial motion compared to contralateral non-injured knees. Studies have shown increases in inflammatory cytokines in the knee following ACL injury, and newer MRI sequences have allowed for earlier objective detection of degenerative changes to cartilage following injury. Recent studies have shown that injecting IL-1 receptor antagonist and corticosteroids can modulate the post-injury inflammatory cascade. ACL reconstruction does not prevent the development of OA but can improve knee kinematics and reduce secondary injury to the cartilage and meniscus. Advancements in imaging studies has allowed for earlier detection of degenerative changes in the knee, which has allowed researchers to study how new interventions can alter the course of degenerative change in the knee following ACL injury.

Association of chemokine expression in anterior cruciate ligament deficient knee with patient characteristics: Implications for post-traumatic osteoarthritis

BACKGROUND

Stromal cell-derived factor-1a (SDF-1α) and high mobility group box chromosomal protein 1 (HMGB1) are chemokines that can drive post-traumatic osteoarthritis (PTOA) induced by anterior cruciate ligament (ACL) injury. However, the influence of patient characteristics on expression of those chemokines remains unclear. Our aim was to determine the relationship between chemokine expression in synovial fluid (SF) of the ACL-deficient (ACL-D) knee and patient characteristics including time from injury, sex, and age.

METHODS

SF samples were collected immediately prior to the first-time ACL reconstruction (ACLR) from 82 patients. Expression of SDF-1α and HMGB1 was measured with human-specific solid phase sandwich enzyme-linked immunosorbent assays. The expression levels between groups divided by time from injury, or age, or sex was compared using Student's t-test. The association of SDF-1α or HMGB1 levels with those variables was determined using regression analysis and Pearson product-moment correlation coefficient.

RESULTS

Regression and correlation analysis indicated significant correlation between SDF-1α expression and time from injury in the cohort (r = -0.266, P = 0.016, n = 82) and in females (r = -0.386, P = 0.024, n = 34). Significant correlation was also observed between SDF-1α expression and age in the cohort (r = -0.224, P = 0.043, n = 82) and in males (r = -0.289, P = 0.046, n = 48). No significant correlation between HMGB1 expression and patient characteristics was detected.

CONCLUSIONS

SDF-1α rather than HMGB1 might serve as a protein marker for monitoring the development of PTOA in the ACL-D knee, especially in female patients.

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.

Multiple Platelet-Rich Plasma Injections Versus Single Platelet-Rich Plasma Injection in Early Osteoarthritis of the Knee: An Experimental Study in a Guinea Pig Model of Early Knee Osteoarthritis

BACKGROUND

Platelet-rich plasma (PRP) has emerged as the forerunner among disease-modifying treatment options for early osteoarthritis (OA) of the knee. However, no consensus is available regarding optimum dosing schedules.

PURPOSE

To determine whether multiple injections of PRP (3 injections) provide better short-term and long-term results than a single injection of PRP in a guinea pig model of knee OA.

STUDY DESIGN

Controlled laboratory study.

METHODS

36 Dunkin-Hartley guinea pigs (weighing ~600-800 g) were chosen for this study. The animals were assigned to group DC (disease control group), group G1 (single-PRP group), and group G2 (multiple-PRP group) containing 10, 10, and 12 animals, respectively. Another 4 animals were used for preparation of allogenic PRP. Groups G1 and G2 received 1 and 3 injections of PRP, respectively, at weekly intervals in the intervention knee while the contralateral knee was injected with normal saline. Group DC received no intervention in either knee. Half of the animals from each group (subgroups DC.3, G1.3, and G2.3) were sacrificed at 3 months, and the remaining half (subgroups DC.6, G1.6, and G2.6) were sacrificed at 6 months after intervention. Both knee joints were harvested for histological assessment of articular cartilage and synovium.

RESULTS

The mean synovial scores for groups G1 and G2 were significantly better than those for group DC at 3 months. No difference was found between groups G1 and G2 at 3 months. At 6 months, group G2 had significantly better mean synovial scores than group G1 and group DC. The mean articular cartilage scores in group G2 were significantly better than those in group DC at 3 months. However, at 6 months, no significant difference was found among any of the groups in terms of mean articular scores.

CONCLUSION

Both single and multiple injections of PRP exert similar anti-inflammatory effects on the synovium in the short term. However, this effect is sustained in the long term only for multiple injections. Multiple injections of PRP exert a chondroprotective effect, but only in the short term. This effect is not seen with a single injection of PRP.

CLINICAL RELEVANCE

This study provides insight into the histological basis for the superiority of multiple injections of PRP.

Adenovirus-mediated transduction with Histone Deacetylase 4 ameliorates disease progression in an osteoarthritis rat model

BACKGROUND

Downregulation of histone deacetylase-4 (HDAC4) contributes to cartilage degeneration in osteoarthritis (OA) because it promotes upregulation of runt-related transcription factor-2 (Runx-2) and osteoarthritis-related genes. The effect of HDAC4 upregulation on cartilage damage in OA remains unknown.

METHODS

Rat chondrocytes were infected with Ad-GFP or Ad-HDAC4-GFP for 48 h, stimulated with interleukin-1β (IL-1β, 10 ng/mL) for 24 h, and then harvested for RT-qPCR. Male Sprague-Dawley rats in 3 groups were given anterior cruciate ligament transection (ACLT) or sham operation, and knee injections with different adenovirus (Ad) vectors at 48 h after surgery and every 3 weeks thereafter: ACLT+Ad-GFP (n = 17); ACLT+Ad-HDAC4-GFP (n = 20); and sham+Ad-GFP (n = 15). Three ACLT-Ad-HDAC4-GFP rats were sacrificed at different times to examine the expression of HDAC4. Two ACLT-Ad-GFP rats and two ACLT-Ad-HDAC4-GFP rats were euthanized at week-2; articular cartilage was harvested and expression of HDAC4 was determined by RT-qPCR. All other rats were euthanized at week-8. Cartilage damage and OA progression was assessed using radiography, fluorescence molecular tomography (FMT), histology, immunohistochemistry (IHC), ELISA, and RT-qPCR.

RESULTS

Overexpression of HDAC4 in chondrocytes stimulated by IL-1β reduced the levels of Runx-2, MMP-13, and Collagen X, but increased the levels of Collagen II and Aggrecan. Upregulation of HDAC4 reduced osteophyte formation and cartilage damage, and increased articular cartilage anabolism.

CONCLUSION

HDAC4 attenuated articular cartilage damage by repression of Runx-2, MMP-13, and collagen X and induction of collagen II and ACAN in this rat model of OA. Upregulation of HDAC4 may provide chondroprotection in OA patients.

Ipriflavone attenuates the degeneration of cartilage by blocking the Indian hedgehog pathway

BACKGROUND

To determine if ipriflavone, a novel and safe inhibitor of Indian hedgehog (Ihh) signaling, can attenuate cartilage degeneration by blocking the Ihh pathway.

METHODS

Human chondrocytes were used to evaluate Ihh signaling, cell proliferation, apoptosis, gene, and protein expression of chondrocytes by cell proliferation and apoptosis assays, real-time qPCR, and Western blotting at 48 h after ipriflavone treatment. Human cartilage explants were further used to validate the cell culture results. The effects of ipriflavone on cartilage degeneration in vivo were assessed using the rat ACLT OA model. Two-month-old male SD rats were randomized into 3 groups (n = 75): (1) sham, (2) ACLT alone, and (3) ACLT+ ipriflavone. Ipriflavone was administered intragastrically at 24 h after ACLT for 6 weeks. The extent of OA progression was evaluated by the OARSI score and immunohistochemistry at 12 weeks after surgery. The Ihh signaling pathway and OA-related genes were quantified by real-time PCR.

RESULTS

Cell proliferation in the cells treated with ipriflavone was increased to 36.40% ± 1.32% (5 μM) and 28.54% ± 0.74% (10 μM) from 11.99% ± 0.35% (DMSO) (P < 0.001), and apoptosis was decreased to 12.64% ± 3.7% (5 μM) and 15.18% ± 3.13% (10 μM) from 25.76% ± 5.1% (DMSO) (P < 0.05). Ipriflavone blocked Runx-2 mainly through the Smo-Gli2 pathway. A similar result was found in the cartilage explant culture. Ihh signaling in vivo was inhibited in animals treated with ipriflavone. Safranin-O staining revealed a less cartilage damage with lower OARSI scores (P < 0.05) in the ipriflavone-treated animals compared with untreated animals. The gene expression of Smo and Gli2 was inhibited significantly by ipriflavone (P < 0.05). The OA-related gene and protein type X, MMP-13, and type II collagen-C fragment were reduced, while type II collagen and Agg were increased in the ipriflavone-treated animals (P < 0.05).

CONCLUSIONS

Catabolic genes were disrupted by blocking the Ihh pathway. This finding suggests that disruption of Ihh signaling with ipriflavone provides chondral protection in rat posttraumatic OA.

GPR120 is an important inflammatory regulator in the development of osteoarthritis

Background

The aim of this study was to investigate the regulatory role of G-protein coupled receptor 120 (GPR120) in the development and progression of osteoarthritis (OA).

Methods

GPR120 knockout (KO) and wild-type (WT) mice were used to create an animal model of OA by means of anterior cruciate ligament transection (ACLT) surgery. The severity of OA was staged and evaluated by histological examination, microcomputed tomography scan and enzyme-linked immunosorbent assay (ELISA). The anti-inflammatory effects of the GPR120 agonist docosahexaenoic acid (DHA) on human chondrocytes were further evaluated by specific inflammatory markers. In addition, the healing progression of a skin defect model was determined with histological assays.

Results

The GPR120-KO mice displayed an accelerated development of OA after ACLT. The secondary inflammation, cartilage degeneration, and subchondral bone aberrant changes were significantly elevated in the early phase of OA in KO mice relative to those in WT mice. In addition, we found that GPR120 levels were downregulated in OA patients compared with control subjects, whereas GPR120 activation with DHA exhibited anti-inflammatory effects in primary human chondrocytes in vitro. Moreover, results from the skin defect model showed that GPR120 agonism with DHA enhanced wound repair in mice, as shown by the downregulation of the number of CD68⁺ cells.

Conclusions

Our study suggests that GPR120 is an important inflammatory mediator during the development of OA, and that it is a potential marker for the diagnosis of high-risk patients with OA.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1660-6) contains supplementary material, which is available to authorized users.

CXCL10 is upregulated in synovium and cartilage following articular fracture

The objective of this study was to investigate the expression of the chemokine CXCL10 and its role in joint tissues following articular fracture. We hypothesized that CXCL10 is upregulated following articular fracture and contributes to cartilage degradation associated with post-traumatic arthritis (PTA). To evaluate CXCL10 expression following articular fracture, gene expression was quantified in synovial tissue from knee joints of C57BL/6 mice that develop PTA following articular fracture, and MRL/MpJ mice that are protected from PTA. CXCL10 protein expression was assessed in human cartilage in normal, osteoarthritic (OA), and post-traumatic tissue using immunohistochemistry. The effects of exogenous CXCL10, alone and in combination with IL-1, on porcine cartilage explants were assessed by quantifying the release of catabolic mediators. Synovial tissue gene expression of CXCL10 was upregulated by joint trauma, peaking one day in C57BL/6 mice (25-fold) versus 3 days post-fracture in MRL/MpJ mice (15-fold). CXCL10 protein in articular cartilage was most highly expressed following trauma compared with normal and OA tissue. In a dose dependent manner, exogenous CXCL10 significantly reduced total matrix metalloproteinase (MMP) and aggrecanase activity of culture media from cartilage explants. CXCL10 also trended toward a reduction in IL-1α-stimulated total MMP activity (p = 0.09) and S-GAG (p = 0.09), but not NO release. In conclusion, CXCL10 was upregulated in synovium and chondrocytes following trauma. However, exogenous CXCL10 did not induce a catabolic response in cartilage. CXCL10 may play a role in modulating the chondrocyte response to inflammatory stimuli associated with joint injury and the progression of PTA. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1220-1227, 2018.

A novel therapeutic strategy for cartilage diseases based on lipid nanoparticle-RNAi delivery system

Background

Cartilage degeneration affects millions of people but preventing its degeneration is a big challenge. Although RNA interference (RNAi) has been used in human trials via silencing specific genes, the cartilage RNAi has not been possible to date because the cartilage is an avascular and very dense tissue with very low permeability.

Purpose

The objective of this study was to develop and validate a novel lipid nanoparticle (LNP)-siRNA delivery system that can prevent cartilage degeneration by knocking down specific genes.

Methods

LNP transfection efficiency was evaluated in vitro and ex vivo. Indian Hedgehog (Ihh) has been correlated with cartilage degeneration. The in vivo effects of LNP-Ihh siRNA complexes on cartilage degeneration were evaluated in a rat model of surgery-induced osteoarthritis (OA).

Results

In vitro, 100% of chondrocytes were transfected with siRNA in the LNP-siRNA group. In accordance with the cell culture results, red positive signals could be detected even in the deep layer of cartilage tissue cultures treated by LNP-beacon. In vivo data showed that LNP is specific for cartilage, since positive signals were detected by fluorescence molecular tomography and confocal microscopy in joint cartilage injected with LNP-beacon, but not on the surface of the synovium. In the rat model of OA, intraarticular injection of LNP-Ihh siRNA attenuated OA progression, and PCR results showed LNP-Ihh siRNA exerted a positive impact on anabolic metabolism and negative impact on catabolic metabolism.

Conclusion

This study demonstrates that our LNP-RNAi delivery system has a significantly chondroprotective effect that attenuates cartilage degeneration and holds great promise as a powerful tool for treatment of cartilage diseases by knocking down specific genes.

The effect of intra-articular allogenic platelet rich plasma in Dunkin-Hartley guinea pig model of knee osteoarthritis

Objectives

To investigate the pathway for disease modifying effect of the PRP in osteoarthritis of knee.

Design

Two experimental models (group I and II) of Twelve Dunkin-Hartley guinea pigs each were enrolled as a part of a prospective controlled experimental study. One knee was enrolled for intervention and the other knee of the same animal used as control, the intervention being three intra-articular allogenic PRP injections given at a weekly interval. Equal volume of isotonic saline injection were given simultaneously in the control knees. Six animals from each model (subgroup IA, IIA) were euthanized at three months and the remaining six (subgroup IB, IIB) at six months post intervention. Samples of synovial fluid were collected from each knee joint for COMP level analysis by ELISA and bilateral knee joints were harvested for histopathological assessment of articular cartilage and synovium at the time of euthanasia.

Results

Mean synovial fluid COMP concentration was significantly lower in PRP treated knees (p<0.05) at three months. On histological examination mean synovitis scores and synovial vascularity were significantly lower in PRP treated knees as compared to controls at both three and six months (p < 0.05). Additionally mean articular cartilage degeneration was significantly lower in PRP treated knees in group 1 only (p<0.05).

Conclusion

Our preliminary data from the study has shown some evidence of positive influence of PRP in knee OA, possibly due to its anti-inflammatory effect and disease modifying effect, shown by short-term chondro-protective effect in PRP injected knees.

Level of evidence

V.

Synovial inflammation plays a greater role in post-traumatic osteoarthritis compared to idiopathic osteoarthritis in the Hartley guinea pig knee

Background

The objective of this study was to evaluate the extent of stromal cell-derived factor-1’s (SDF-1) involvement in the pathogenesis of idiopathic versus post-traumatic OA by comparing differences in synovial membrane morphology, SDF-1 synovial fluid (SF) concentrations, and matrix metalloproteinase-13 (MMP-13) SF concentrations.

Methods

Thirty-six 3-month-old Hartley guinea pigs were obtained and divided into 6 groups. Upon sacrifice, India Ink staining was used to evaluate gross morphology, Safranin O/Fast green staining was used to assess cartilage damage, H/E staining was employed to visualize the synovium, and SF samples were obtained for biochemical analyses. Sandwich ELISA was used to quantify the SF concentrations of SDF-1 and MMP-13.

Results

12 month-old, idiopathic OA guinea pigs and 5.5 month-old ACLT animals had comparable cartilage damage when evaluated by the Modified Mankin Score. SDF-1 and MMP-13 concentrations were not statistically different between the two groups. The synovial membrane of the 5.5 month ACLT group had severe synovitis compared to the idiopathic OA group.

Conclusion

In this study, it was found that synovial inflammation, independent of cartilage morphology, SDF-1 concentration, and MMP-13 concentration, was markedly different between idiopathic and post-traumatic OA. These results highlight the differing morphological and biochemical profiles of post-traumatic versus idiopathic osteoarthritis and calls for a more thorough examination of the sole of the synovial membrane in the pathogenesis of post-traumatic osteoarthritis.

Acute mobilization and migration of bone marrow-derived stem cells following anterior cruciate ligament rupture

OBJECTIVE

Little is known regarding acute local and systemic processes following anterior cruciate ligament (ACL) rupture. No study has elucidated whether bone marrow-derived mesenchymal stem cells (MSCs) are mobilized into circulation and recruited to the injured joint.

METHODS

In Part 1, Lewis rats were randomized to noninvasive ACL rupture (Rupture) or non-injured (Control) (n = 6/group). After 72 h, whole blood MSC concentration was assessed using flow cytometry. Synovial fluid and serum were assayed for stromal cell-derived factor (SDF)-1α and cartilage degeneration biomarkers, respectively. In Part 2, 12 additional rats were randomized and intravenously-injected with fluorescently-labeled allogenic MSCs. Cell tracking was performed using longitudinal, in vivo and ex vivo near-infrared (NIR) imaging and histology. Synovium SDF-1α and interleukin (IL)-17A immunostaining was performed. Serum was assayed for SDF-1α and 29 other cytokines.

RESULTS

In Part 1, there was a significant increase in MSC concentration and synovial fluid SDF-1α in Rupture. No differences in cartilage biomarkers were observed. In Part 2, Rupture had significantly higher NIR signal at 24, 48, and 72 h, indicating active recruitment of MSCs to the injured joint. Ex vivo cell tracking demonstrated MSC localization in the synovium and myotendinous junction (MTJ) of the quadriceps. Injured synovia exhibited increased synovitis grade and higher degree of IL-17A and SDF-1α immunostaining.

CONCLUSION

ACL rupture induced peripheral blood mobilization of MSCs and migration of intravenously-injected allogenic MSCs to the injured joint, where they localized in the synovium and quadriceps MTJ.

Targeted designed variants of alpha-2-macroglobulin (A2M) attenuate cartilage degeneration in a rat model of osteoarthritis induced by anterior cruciate ligament transection

Background

The study was performed to evaluate whether targeted alpha-2-macroglobulin (A2M) variants have a similar or enhanced function at wild-type (wt)-A2M to attenuate cartilage degeneration in vivo.

Methods

In and ex-vivo experiment, bovine cartilage explants (BCE) were incubated with TNF-α and IL-1β with or without wt-A2M or A2M variants. Cartilage catabolism was measured in culture supernatant by sulfated glycosaminoglycan (sGAG). In an in-vivo experiment, 2-month-old male Wistar rats (n = 77) were randomly divided into seven groups and treated with different doses of A2M or its variants by intra-articular injection at 24 hours and day 14 after anterior cruciate ligament transection (ACLT), receiving (1) ACLT/PBS; (2) ACLT/wt-A2M (0.153 mg); (3) ACLT/CYT-108 A2M (0.153 mg); (4) ACLT/CYT-108 A2M (0.077 mg); (5) ACLT/CYT-98 A2M (0.153 mg); (6) ACLT/CYT-98 A2M (0.077 mg); or (7) sham/PBS. The joints and synovial lavage were collected 8 weeks after surgery. Fluorescence molecular tomography was used to monitor inflammation in vivo using probes ProSense and MMPSense at 24 hours, and weeks 2, 4, and 6 after surgery. The cartilage damage was quantified using Osteoarthritis Research Society International score and matrix metalloproteinase (MMP)-3, -13, collagen (Col) X, Col 2, Runx2, and aggrecan (Acan) were detected by immunohistochemical analysis (IHC), ELISA, and RT-PCR.

Results

A2M variants inhibited catabolism in the BCE model by up to 200% compared with wt-A2M. ProSense and MMPSense were dramatically increased in all groups after surgery. Supplemental A2M or its variants reduced ProSense and MMPSense compared with the PBS treatment. Less cartilage damage, lower MMP-13 and Col 2 degraded product, and stronger Col 2 synthesis were detected in animals treated with A2M or its variants compared with PBS-treated animals. A2M and its variants enhanced Col 2 and Acan synthesis, and suppressed MMP-3, MMP-13, Runx2, and Col X production. A2M-108 variant demonstrated less cartilage damage compared with wt-A2M and A2M-98 variant.

Conclusion

The targeted variants of A2M have a chondroprotective effect similar to wt-A2M. However, A2M-108 variant has enhanced function to attenuate cartilage degeneration compared with wt-A2M.

Review of Soluble Biomarkers of Osteoarthritis: Lessons From Animal Models

Objective Osteoarthritis (OA) is one of the leading causes of disability within the adult population. Currently, its diagnosis is mainly based on clinical examination and standard radiography. To date, there is no way to detect the disease at a molecular level, before the appearance of structural changes and symptoms. So an attractive alternative for monitoring OA is the measurement of biochemical markers in blood, urine, or synovial fluid, which could reflect metabolic changes in joint tissue and therefore disease onset and progression. Animal models are relevant to investigate the early stage of OA and metabolic changes occurring in joint tissues. The goal of this narrative review is to summarize the scientific data available in the literature on soluble biomarkers in animal models of OA. Design A literature search was conducted using the PubMed/Medline and Scopus databases between February 1995 and December 2015. All original articles, systematic and narrative reviews published in French or in English were considered. Results We summarized the data of 69 studies and proposed a classification scheme for OA biomarkers in animal studies, largely inspired by the BIPEDS classification. Conclusions Studies about biomarkers and animal models indicate that some markers could be valuable to monitor OA progression and assess therapeutic response in some animal models.

Attenuation of subchondral bone abnormal changes in osteoarthritis by inhibition of SDF-1 signaling

BACKGROUND

Current conservative treatments for osteoarthritis (OA) are largely symptoms control therapies. Further understanding on the pathological mechanisms of OA is crucial for new pharmacological intervention.

OBJECTIVE

In this study, we investigated the role of Stromal cell-derived factor-1(SDF-1) in regulating subchondral bone changes during the progression of OA.

METHODS

Clinical samples of different stages of OA severity were analyzed by histology staining, micro-CT, enzyme-linked immunosorbent assay (ELISA) and western blotting, to compare SDF-1 level in subchondral bone. The effects of SDF-1 on human mesenchymal stem cells (MSCs) osteogenic differentiation were evaluated. In vivo assessment was performed in an anterior cruciate ligament transaction plus medial meniscus resection in the SD rats. The OA rats received continuous infusion of AMD3100 (SDF-1 receptor blocker) in osmotic mini-pump implanted subcutaneously for 6 weeks. These rats were then terminated and subjected to the same in vitro assessments as human OA samples.

RESULTS

SDF-1 level was significantly elevated in the subchondral bone of human OA samples. In the cell studies, the results showed SDF-1 plays an important role in osteogenic differentiation of MSCs. In the OA animal studies, there were less cartilage damage in the AMD3100-treated group; microCT results showed that the subchondral bone formation was significantly reduced and so did the number of positive Nestin or Osterix cells in the subchondral bone region.

CONCLUSIONS

Higher level of SDF-1 may induce the subchondral bone abnormal changes in OA and inhibition of SDF-1 signaling could be a potential therapeutic approach for OA.

A systemic review of existing serological possibilities to diagnose canine osteoarthritis with a particular focus on extracellular matrix proteoglycans and protein

Extra-cellular matrix (ECM) components are important and their stabilization is significant in maintaining normal healthy joint environment. In osteoarthritis (OA), ECM components are altered and indicate disease progression. The joint ECM is composed of proteoglycans (aggrecan, perlecan, inter α-trypsin inhibitor), glycoproteins (fibronectin, lubricin, COMP) and collagen types (most abundantly collagen type II) which represent structural and functional transformation during disease advancement. ECM investigation revealed significant biomarkers of OA that could be used as a diagnostic and therapeutic tool in different canine orthopedic diseases. This review deliberates our current findings of how the components of ECM change at the molecular level during disease progression in canine OA.

Review of current understanding of post-traumatic osteoarthritis resulting from sports injuries

Certain types of joint injuries, common in athletes, are known to have a high association with the development of osteoarthritis (OA). Post-traumatic osteoarthritis (PTOA) is especially debilitating due to its earlier onset than traditional OA, and its predisposition to affect a younger and more active population. Five common athletic injuries have been demonstrated to be risk factors for the development of OA. These include ACL rupture, meniscus tear, glenohumeral instability, patellar dislocation, and ankle instability. Though the mechanisms responsible for the development of PTOA are not entirely clear, certain kinematic, biologic, and mechanical factors have been implicated. In addition, there has been an increased emphasis on development of new methods to detect early OA changes in patients with known risk factors, as early intervention may prevent the development of end-stage OA. New imaging modalities as well as the identification of specific biomarkers may allow earlier detection. Though these developments hold promise, it is not entirely known what steps we can take today to prevent the future development of OA, even with early detection. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:397-405, 2017.

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.

Meniscal biology in health and disease

The knee is a fascinating yet complex joint. Researchers and clinicians agree that the joint is an organ comprised of highly specialized intrinsic and extrinsic tissues contributing to both health and disease. Key to the function and movement of the knee are the menisci, exquisite fibrocartilage structures that are critical structures for maintaining biological and biomechanical integrity of the joint. The biological/physiological functions of the menisci must be understood at the tissue, cellular and even molecular levels in order to determine clinically relevant methods for assessing it and influencing it. By investigating normal and pathological functions at the basic science level, we can begin to translate data to patients. The objective of this article is to provide an overview of this translational pathway so that progression toward improved diagnostic, preventative, and therapeutic strategies can be effectively pursued. We have thoroughly examined the pathobiological, biomarker, and imaging aspects of meniscus research. This translational approach can be effective toward optimal diagnosis, prevention, and treatment for the millions of patients who suffer from meniscal disorders each year.

CXCL12/CXCR4 Axis Regulates Aggrecanase Activation and Cartilage Degradation in a Post-Traumatic Osteoarthritis Rat Model

We evaluated the role of the CXCL12/CXCR4 (C-X-C motif chemokine ligand 12/C-X-C chemokine receptor type 4) axis in aggrecanase-mediated cartilage degradation, and explored the underlying mechanism in a post-traumatic osteoarthritis rat model. Expression of CXCL12/CXCR4 and ADAMTS-5 was analyzed in the knees of osteoarthritic and non-arthritic rats using Western blot, ELISA, immunohistochemistry and immunofluorescence. Rodent studies were performed using Sprague-Dawley rats, with animals divided into three groups: Destabilization of the medial meniscus/AMD3100-treated (DMM/AMD3100-treated), DMM/PBS-treated, and sham controls. Rats were sacrificed after eight weeks, and samples were collected for histology and immunohistochemistry analyses. IL-1-pretreated primary chondrocytes were cultured with untreated control, CXCL12a, siNC + CXCL12a, or siRNA CXCR4 + CXCL12a, and analyzed for expression of relevant markers and cellular pathways. Higher levels of CXCL12 were detected in the knee fluid of osteoarthritic subjects, with strong staining for CXCR4 in chondrocytes and CXCL12 in synoviocytes together with enhanced expression of ADAMTS-5. DMM/AMD3100-treated rats showed a significantly reduced immunological response, with minimal evidence of pathology in both histological and immunohistochemical analyses. Treatment with CXCL12a increased the expression of ACAN, RUNX-2, and ADAMTS-4/5 in IL-1-pretreated primary chondrocytes, together with a decrease in the expression of SOX-9. Molecular analyses revealed strong induction of NF-κB activation, along with phosphorylation of MAPKs, and activation of canonical Wnt/β-catenin signaling. In conclusion, inhibition of SDF-1α/CXCR4 signaling axis was able to inhibit aggrecanase expression and lessen cartilage degeneration in post-traumatic osteoarthritis rats.

Translational potential of ginsenoside Rb1 in managing progression of osteoarthritis

BACKGROUND

Osteoarthritis (OA) is the most common degenerative joint disorder. Inflammatory cytokine plays an important role in OA progression. Previous studies have demonstrated that ginsenoside Rb1 would prevent inflammation and apoptosis in chondrocytes. However, we have not found any animal study reporting that Rb1 attenuates the severity of OA.

OBJECTIVE

In this study, we used a rat anterior cruciate ligament transaction plus medial meniscus resection (ACLT + MMx) model of OA and a cell model, to investigate whether administration of ginsenoside Rb1 may attenuate the progression of arthritis.

METHODS

In this in vivo study, 16-week-old male Sprague-Dawley rats were divided into three groups: Group 1 (sham control group), Group 2 (Rb1-treated group), and Group 3 (OA group). In Groups 2 and 3, OA was induced in the right knee joint with ACLT + MMx in rats. Then Group 2 received continuous infusion of ginsenoside Rb1 via osmotic mini-pumps implanted subcutaneously. At 4 weeks after treatment, the rats were sacrificed. Interleukin-1β (IL-1β) level was evaluated by enzyme-linked immunosorbent assay (ELISA); cartilage damage was assessed via histology (Safranin-O/fast green stain) and immunohistochemistry [matrix metalloproteinase-13 (MMP13) and type X collagen (Col X)]. For cell study, C5.18 (rat chondrocyte cell line) was used in this research. The effect of Rb1 on IL-1β-induced MMP13 or Col X expression level in C5.18 cells was investigated.

RESULTS

In this in vivo study, characteristics of OA were present in the OA group, in contrast to less severe damage generally observed in the Rb1 treatment group: first, IL-1β level was significantly decreased, and second, cartilage degeneration was attenuated, as indicated by lower histologic damage scores and lower percentages of MMP13 or Col X-positive chondrocytes. In the cell study, the results showed that Rb1 treatment would relieve the MMP13 or Col X expression in C5.18 cells induced by IL-1β.

CONCLUSION

In the present study, we demonstrated that Rb1 can attenuate the progression or severity of arthritis by reducing inflammation.

Spatiotemporal gait compensations following medial collateral ligament and medial meniscus injury in the rat: correlating gait patterns to joint damage

Introduction

After transection of the medial collateral ligament and medial meniscus (MCLT + MMT) in the rat, focal cartilage lesions develop over 4–6 weeks; however, sham surgery (MCLT alone) does not result in cartilage damage over a similar period. Thus, comparison of MCLT + MMT with the MCLT sham group offers an opportunity to investigate behavioral modifications related to focal cartilage and meniscus damage in the rat.

Methods

MCLT or MCLT + MMT surgery was performed in the right knees of male Lewis rats, with spatiotemporal gait patterns and hind limb sensitivity assessed at 1, 2, 4, and 6 weeks postsurgery (n = 8 rats per group per time point, n = 64 total). After the animals were euthanized, Histology was performed to assess joint damage.

Results

MCLT + MMT animals had unilateral gait compensations at early time points, but by week 6 bilateral gait compensations had developed in both the MCLT sham and MCLT + MMT groups. Conversely, heightened tactile sensitivity was detected in both MCLT sham and MCLT + MMT animals at week 1, but only the MCLT + MMT animals maintained heightened sensitivity to week 6. Cartilage lesions were found in the MCLT + MMT group but not in the MCLT sham group. Correlations could be identified between joint damage and gait changes in MCLT + MMT animals; however, the same gait changes were found with MCLT sham animals despite a lack of joint damage.

Conclusions

Combined, our data highlight a common conundrum in osteoarthritis (OA) research: Some behavioral changes correlate to cartilage damage in the OA group, but the same changes can be identified in non-OA controls. Of the behavioral changes detected, allodynia was maintained in MCLT + MMT animals but not in the MCLT sham group. However, the correlation between cartilage damage and hind limb sensitivity is relatively weak (R = −0.4498), and the range of sensitivity measures overlaps between groups. The factors driving gait abnormalities in MCLT and MCLT + MMT animals also remain uncertain. The gait modifications are similar between groups and do not appear until weeks after surgery, despite cartilage damage being focused in the MCLT + MMT group. Combined, our data highlight the need to evaluate the links between noncartilage changes and behavioral changes following joint injury in the rat.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0791-2) contains supplementary material, which is available to authorized users.

Joint distraction attenuates osteoarthritis by reducing secondary inflammation, cartilage degeneration and subchondral bone aberrant change

OBJECTIVE

Osteoarthritis (OA) is a progressive joint disorder. To date, there is not effective medical therapy. Joint distraction has given us hope for slowing down the OA progression. In this study, we investigated the benefits of joint distraction in OA rat model and the probable underlying mechanisms.

METHODS

OA was induced in the right knee joint of rats through anterior cruciate ligament transaction (ACLT) plus medial meniscus resection. The animals were randomized into three groups: two groups were treated with an external fixator for a subsequent 3 weeks, one with and one without joint distraction; and one group without external fixator as OA control. Serum interleukin-1β level was evaluated by ELISA; cartilage quality was assessed by histology examinations (gross appearance, Safranin-O/Fast green stain) and immunohistochemistry examinations (MMP13, Col X); subchondral bone aberrant changes was analyzed by micro-CT and immunohistochemistry (Nestin, Osterix) examinations.

RESULTS

Characters of OA were present in the OA group, contrary to in general less severe damage after distraction treatment: firstly, IL-1β level was significantly decreased; secondly, cartilage degeneration was attenuated with lower histologic damage scores and the lower percentage of MMP13 or Col X positive chondrocytes; finally, subchondral bone abnormal change was attenuated, with reduced bone mineral density (BMD) and bone volume/total tissue volume (BV/TV) and the number of Nestin or Osterix positive cells in the subchondral bone.

CONCLUSION

In the present study, we demonstrated that joint distraction reduced the level of secondary inflammation, cartilage degeneration and subchondral bone aberrant change, joint distraction may be a strategy for slowing OA progression.

Intraarticular Matrix Metalloproteinases and Aggrecan Degradation Are Elevated After Articular Fracture

BACKGROUND

Posttraumatic osteoarthritis (OA) is a variant of OA that can develop after articular injury. Although the mechanism(s) of posttraumatic OA are uncertain, the presence and impact of postinjury proteolytic enzymes on articular cartilage remain unknown. To our knowledge, there are no studies that evaluate the presence of matrix metalloproteinases (MMPs) or aggrecan degradation after articular fracture.

QUESTIONS/PURPOSES

(1) Are MMP concentrations and aggrecan degradation elevated after intraarticular fracture? (2) Are MMP concentrations and aggrecan degradation greater in high-energy injuries compared with low-energy injuries? (3) Do the concentrations of these biomarkers remain elevated at a secondary aspiration?

METHODS

Between December 2011 and June 2013, we prospectively enrolled patients older than 18 years of age with acute tibial plateau fracture. Exclusion criteria included age older than 60 years, preexisting knee OA, injury greater than 24 hours before evaluation, contralateral knee injury, history of autoimmune disease, open fracture, and non-English-speaking patients. During the enrollment period, we enrolled 45 of the 91 (49%) tibial plateau fractures treated at our facility. Knee synovial fluid aspirations were obtained from both the injured and uninjured knees; two patients received aspirations in the emergency department and the remaining patients received aspirations in the operating room. Twenty patients who underwent spanning external fixator followed by definitive fixation were aspirated during both surgical procedures. MMP-1, -2, -3, -7, -9, -10, -12, and -13 concentrations were quantified using multiplex assays. Aggrecan degradation was quantified using sandwich enzyme-linked immunosorbent assay.

RESULTS

There were higher concentrations of MMP-1 (3.89 ng/mL [95% confidence interval {CI}, 2.37-6.37] versus 0.37 ng/mL [95% CI, 0.23-0.61], p < 0.001), MMP-3 (457.35 ng/mL [95% CI, 274.5-762.01] versus 129.17 ng/mL [95% CI, 77.01-216.66], p < 0.001), MMP-9 (6.52 ng/mL [95% CI, 3.86-11.03] versus 0.96 ng/mL [95% CI, 0.56-1.64], p < 0.001), MMP-10 (0.52 ng/mL [95% CI, 0.40-0.69] versus 0.23 ng/mL [95% CI, 0.17-0.30], p < 0.001), and MMP-12 (0.18 ng/mL [95% CI, 0.14-0.23] versus 0.10 ng/mL [95% CI, 0.0.081-0.14], p = 0.005) in injured knees compared with uninjured knees. There was not a detectable difference in MMP concentrations or aggrecan degradation between high- and low-energy injuries. MMP-1 (53.25 versus 3.89 ng/mL, p < 0.001), MMP-2 (76.04 versus 0.37 ng/mL, p < 0.001), MMP-3 (1250.62 versus 457.35 ng/mL, p = 0.002), MMP-12 (1.37 versus 0.18, p < 0.001), MMP-13 (0.98 versus 0.032 ng/mL, p < 0.001), and aggrecan degradation (0.58 versus 0.053, p < 0.001) were increased at the second procedure (mean, 9.5 days; range, 3-21 days) as compared with the initial procedure.

CONCLUSIONS

Because MMPs and aggrecan degradation are elevated after articular fracture, future studies are necessary to evaluate the impact of elevated MMPs and aggrecan degradation on human articular cartilage.

CLINICAL RELEVANCE

If further clinical followup can demonstrate a relationship between posttraumatic OA and elevated MMPs and aggrecan degradation, they may provide potential for therapeutic targets to prevent or delay the destruction of the joint. Additionally, these markers may offer prognostic information for patients.

Attenuation of cartilage pathogenesis in post-traumatic osteoarthritis (PTOA) in mice by blocking the stromal derived factor 1 receptor (CXCR4) with the specific inhibitor, AMD3100

SDF-1 was found to infiltrate cartilage, decrease proteoglycan content, and increase MMP-13 activity after joint trauma. In this study, we tested the hypothesis that interference of the SDF-1/CXCR4 signaling pathway via AMD3100 can attenuate pathogenesis in a mouse model of PTOA. We also tested the predictive and confirmatory power of fluorescence molecular tomography (FMT) for cartilage assessment. AMD3100 was continuously delivered via mini-osmotic pumps. The extent of cartilage damage after AMD3100 or PBS treatment was assessed by histological analysis 2 months after PTOA was induced by surgical destabilization of the medial meniscus (DMM). Biochemical markers of PTOA were assessed via immunohistochemistry and in vivo fluorescence molecular tomography (FMT). Regression analysis was used to validate the predictive power of FMT measurements. Safranin-O staining revealed significant PTOA damage in the DMM/PBS mice, while the DMM/AMD3100 treated mice showed a significantly reduced response with minimal pathology. Immunohistochemistry showed that AMD3100 treatment markedly reduced typical PTOA marker expression in chondrocytes. FMT measurements showed decreased cathepsins and MMP activity in knee joints after treatment. The results demonstrate that AMD3100 treatment attenuates PTOA. AMD3100 may provide a viable and expedient option for PTOA therapy given the drug's FDA approval and well-known safety profile.

CXC chemokine ligand 12a enhances chondrocyte proliferation and maturation during endochondral bone formation

OBJECTIVE

We investigated the roles of CXC chemokine ligand 12a (CXCL12a), also known as stromal cell-derived factor-1α (SDF-1α), in endochondral bone growth, which can give us important clues to understand the role of CXCL12a in osteoarthritis (OA).

METHODS

Primary chondrocytes and tibial explants from embryonic 15.5 day-old mice were cultured with recombinant mouse CXCL12a. To assess the role of CXCL12a in chondrogenic differentiation, we conducted mesenchymal cell micromass culture.

RESULTS

In tibia organ cultures, CXCL12a increased total bone length in a dose-dependent manner through proportional effects on cartilage and bone. In accordance with increased length, CXCL12a increased the protein level of proliferation markers, such as cyclin D1 and proliferating cell nuclear antigen (PCNA), in primary chondrocytes as well as in tibia organ culture. In addition, CXCL12a increased the expression of Runx2, Col10 and MMP13 in primary chondrocytes and tibia organ culture system, implying a role of CXCL12a in chondrocyte maturation. Micromass cultures of limb-bud mesenchymal progenitor cells (MPCs) revealed that CXCL12a has a limited effect on early chondrogenesis, but significantly promoted maturation of chondrocytes. CXCL12a induced the phosphorylation of p38 and Erk1/2 MAP kinases and IκB. The increased expression of cyclin D1 by CXCL12a was significantly attenuated by inhibitors of MEK1 and NF-κB. On the other hand, p38 and Erk1/2 MAP kinase and NF-κB signaling were associated with CXCL12a-induced expression of Runx2 and MMP13, the marker of chondrocyte maturation.

CONCLUSION

CXCL12a promoted the proliferation and maturation of chondrocytes, which strongly suggest that CXCL12a may have a negative effect on articular cartilage and contribute to OA progression.

Posttraumatic knee osteoarthritis following anterior cruciate ligament injury: Potential biochemical mediators of degenerative alteration and specific biochemical markers

As a common injury, anterior cruciate ligament (ACL) injury is unable to heal itself naturally, which possibly increases knee instability, accelerates the risk of joint degeneration and leads to knee osteoarthritis (OA) in the ACL-injured knee. Thus, ACL reconstruction using an autograft or allograft tendon is proposed to maintain the biomechanical stability of the knee joint. However, previous studies demonstrate that surgical management of ACL reconstruction failed to abrogate the development of OA completely, indicating that biochemical disturbance is responsible for the osteoarthritic changes observed following ACL injury. Inflammatory mediators are elevated subsequent to ACL injury or rupture, inducing matrix metalloproteinase production, proteoglycan degradation, collagen destruction, chondrocyte necrosis and lubricin loss. These potential biochemical mediators may aid in the development of effective biological management to reduce the onset of future posttraumatic OA. Furthermore, during the degenerative process of cartilage, there are a number of cartilage-specific biomarkers, which play a critical step in the loss of structural and functional integrity of cartilage. The present review illustrates several specific biomarkers in the ACL-injured knee joint, which may provide effective diagnostic and prognostic tools for investigating cartilage degenerative progression and future posttraumatic OA of ACL-injured patients.

Concentrations of stromal cell-derived factor-1 in serum, plasma, and synovial fluid of horses with osteochondral injury

OBJECTIVE

To determine whether stromal cell-derived factor-1 (SDF-1) concentrations in serum, plasma, and synovial fluid differed among untrained, race-trained, and osteochondral-injured Thoroughbred racehorses.

ANIMALS

22 racehorses without osteochondral injury and 37 racehorses with osteochondral injury.

PROCEDURES

Horses without osteochondral injury were examined before and after 5 to 6 months of race training. Horses with osteochondral injury were undergoing arthroscopic surgery for removal of osteochondral fragments from carpal or metacarpophalangeal or metatarsophalangeal joints (fetlock joints). Serum, plasma, and fetlock or carpal synovial fluid samples were obtained and analyzed for SDF-1 concentration by use of an ELISA.

RESULTS

In horses with fetlock or carpal joint injury, mean synovial fluid SDF-1 concentrations were significantly higher, serum SDF-1 concentrations were significantly lower, and synovial fluid-to-serum SDF-1 ratios were significantly higher than in untrained and trained horses. Synovial fluid SDF-1 concentrations were not significantly different between trained and untrained horses. Plasma SDF-1 concentrations were not different among the 3 groups. Results obtained with serum, compared with synovial fluid and plasma, had better sensitivity for differentiating between osteochondral-injured horses and uninjured horses. In horses with fetlock joint osteochondral injury, serum SDF-1 concentrations were correlated with radiographic and arthroscopic inflammation scores, but not arthroscopic cartilage scores.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that serum SDF-1 concentrations were more sensitive than plasma and synovial fluid concentrations for detection of osteochondral injury in the fetlock or carpal joint of racehorses. Analysis of serum and synovial SDF-1 concentrations in horses with experimentally induced joint injury may help define the onset and progression of post-traumatic osteoarthritis and aid in the evaluation of anti-inflammatory treatments.

A normative study of the synovial fluid proteome from healthy porcine knee joints

Synovial fluid in an articulating joint contains proteins derived from the blood plasma and proteins that are produced by cells within the joint tissues, such as synovium, cartilage, ligament, and meniscus. The proteome composition of healthy synovial fluid and the cellular origins of many synovial fluid components are not fully understood. Here, we present a normative proteomics study using porcine synovial fluid. Using our optimized method, we identified 267 proteins with high confidence in healthy synovial fluid. We also evaluated mRNA expression data from tissues that can contribute to the synovial fluid proteome, including synovium, cartilage, blood, and liver, to better estimate the relative contributions from these sources to specific synovial fluid components. We identified 113 proteins in healthy synovial fluid that appear to be primarily derived from plasma transudates, 37 proteins primarily derived from synovium, and 11 proteins primarily derived from cartilage. Finally, we compared the identified synovial fluid proteome to the proteome of human plasma, and we found that the two body fluids share many similarities, underlining the detected plasma derived nature of many synovial fluid components. Knowing the synovial fluid proteome of a healthy joint will help to identify mechanisms that cause joint disease and pathways involved in disease progression.

Identification of α2-macroglobulin as a master inhibitor of cartilage-degrading factors that attenuates the progression of posttraumatic osteoarthritis

OBJECTIVE

To determine if supplemental intraarticular α2-macroglobulin (α2 M) has a chondroprotective effect in a rat model of osteoarthritis (OA).

METHODS

Using Western blotting, mass spectrometry, enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry, α2 M was identified as a potential therapeutic agent through a comparison of α2 M concentrations in serum, synovial fluid (SF), and cartilage from normal subjects and patients with OA. In cultured chondrocytes, the effects of α2 M on interleukin-1 (IL-1)-induced cartilage catabolic enzymes were evaluated by Luminex assay and ELISA. In vivo effects on cartilage degeneration and matrix metalloproteinase 13 (MMP-13) concentration were evaluated in male rats (n = 120) randomized to 1 of 4 treatments: 1) anterior cruciate ligament transection (ACLT) and saline injections, 2) ACLT and 1 IU/kg injections of α2 M, 3) ACLT and 2 IU/kg injections of α2 M, or 4) sham operation and saline injections. Rats were administered intraarticular injections for 6 weeks. The concentration of MMP-13 in SF lavage fluid was measured using ELISA. OA-related gene expression was quantified by real-time quantitative polymerase chain reaction. The extent of OA progression was graded by histologic examination.

RESULTS

In both normal subjects and OA patients, α2 M levels were lower in SF as compared to serum, and in OA patients, MMP-13 levels were higher in SF than in serum. In vitro, α2 M inhibited the induction of MMP-13 by IL-1 in a dose-dependent manner in human chondrocytes. In the rat model of ACLT OA, supplemental intraarticular injection of α2 M reduced the concentration of MMP-13 in SF, had a favorable effect on OA-related gene expression, and attenuated OA progression.

CONCLUSION

The plasma protease inhibitor α2 M is not present in sufficient concentrations to inactivate the high concentrations of catabolic factors found in OA SF. Our findings suggest that supplemental intraarticular α2 M provides chondral protection in posttraumatic OA.

Pathogenesis of post-traumatic OA with a view to intervention

Post-traumatic osteoarthritis (PTOA) subsequent to joint injury accounts for over 12% of the overall disease burden of OA, and higher in the most at-risk ankle and knee joints. Evidence suggests that the pathogenesis of PTOA may be related to inflammatory processes and alterations to the articular cartilage, menisci, muscle and subchondral bone that are initiated in the acute post-injury phase. Imaging of these early changes, as well as a number of biochemical markers, demonstrates the potential for use as predictors of future disease, and may help stratify patients on the likelihood of their developing clinical disease. This will be important in guiding future interventions, which will likely target elements of the inflammatory response within the joint, molecular abnormalities related to cartilage matrix degradation, chondrocyte function and subchondral bone remodelling. Until significant improvements are made, however, in identifying patients most at risk for developing PTOA--and therefore those who are candidates for therapy--primary prevention programmes will remain the most effective current management tools.

MicroRNA-1 regulates chondrocyte phenotype by repressing histone deacetylase 4 during growth plate development

MicroRNAs (miRs) are noncoding RNAs (17-25 nt) that control translation and/or mRNA degradation. Using Northern blot analysis, we identified that miR-1 is specifically expressed in growth plate cartilage in addition to muscle tissue, but not in brain, intestine, liver, or lung. We obtained the first evidence that miR-1 is highly expressed in the hypertrophic zone of the growth plate, with an 8-fold increase compared with the proliferation zone; this location coincides with the Ihh and Col X expression regions in vivo. MiR-1 significantly induces chondrocyte proliferation and differentiation. We further identified histone deacetylase 4 (HDAC4) as a target of miR-1. HDAC4 negatively regulates chondrocyte hypertrophy by inhibiting Runx2, a critical transcription factor for chondrocyte hypertrophy. MiR-1 inhibits both endogenous HDAC4 protein by 2.2-fold and the activity of a reporter gene bearing the 3'-untranslated region (UTR) of HDAC4 by 3.3-fold. Conversely, knockdown of endogenous miR-1 relieves the repression of HDAC4. Deletion of the miR-1 binding site in HDAC4 3'-UTR or mutated miR-1 abolishes miR-1-mediated inhibition of the reporter gene activity. Overexpression of HDAC4 reverses miR-1 induction of chondrocyte differentiation markers Col X and Ihh. HDAC4 inhibits Runx2 promoter activity in a dosage-dependent manner. Thus, miR-1 plays an important role in the regulation of the chondrocyte phenotype during the growth plate development via direct targeting of HDAC4.

Post-traumatic knee osteoarthritis in the young patient: therapeutic dilemmas and emerging technologies

Traumatic knee injury is common in young adults and strongly contributes to premature development of knee osteoarthritis (OA). Post-traumatic knee OA poses a therapeutic dilemma to the physician, since no known therapy has an acceptable safety profile, effectively relieves joint pain, and enjoys reasonable patient acceptance. Consequently, these young patients will ultimately be faced with the decision to either undergo surgical intervention, despite prosthesis durability concerns, or to continue with ineffective nonsurgical treatment. Emerging therapies, such as biologics, disease-modifying drugs, partial joint resurfacings, and minimally invasive joint-unloading implants are currently being studied to fill this therapeutic void in the young patient with post-traumatic knee OA.

Joint instability and cartilage compression in a mouse model of posttraumatic osteoarthritis

Joint instability and cartilage trauma have been previously studied and identified as key mediators in the development of posttraumatic osteoarthritis (PTOA). The purpose of this study was to use an in vivo model to compare the effect of joint instability, caused by the rupture of the anterior cruciate ligament (ACL), versus cartilage compression. In this study, mice were subjected to cyclical axial loads of twelve Newtons (N) for 240 cycles or until the ACL ruptured. One and eight weeks after this procedure, knees were sectioned coronally and evaluated for osteoarthritis by histology. Using a scoring scale established by [Pritzker K, Gay S, Jimenez S, et al. (2006): Osteoarthritis Cartilage 14:13-29], the articular cartilage across each surface was scored and combined to produce a total degeneration score. The ACL-ruptured group had a significantly greater total degeneration score than either control or compression treated joints at 1 and 8 weeks. Additionally, only sections from ACL-ruptured knees consistently showed synovitis after 1 week and osteophyte formation after 8 weeks. Thus, it appears using that ACL rupture consistently creates a severe osteoarthritis phenotype, while axial cartilage compression alone does not appear to be an appropriate method of inducing PTOA in vivo.