Impact orientation can significantly affect the outcome of a blunt impact to the rabbit patellofemoral joint

This laboratory has developed a subfracture, joint trauma model in rabbits. Using a dropped impact mass directed onto a slightly abducted joint, chronic softening of retropatellar cartilage and thickening of underlying subchondral bone are documented in studies to 1 year post-insult. It has been hypothesized that these tissue changes are initiated by stresses developed during impact loading. A previous analytical study by this laboratory suggests that tensile strains in retropatellar cartilage can be significantly lowered, without significantly changing the intensity of stresses in the underlying subchondral bone, by reorientation of patellar impact more centrally on the joint. In the current study comparative experiments were performed on groups of animals after either an impact directed on the slightly abducted limb or a more central impact. One-year post-trauma in animals subjected to the central-oriented impact no degradation of the shear modulus for the retropatellar cartilage was documented, but the thickness of the underlying subchondral bone was significantly increased. In contrast, alterations in cartilage and underlying bone following impact on the slightly abducted limb were consistent with previous studies. The current experimental investigation showed the sensitivity of post-trauma alterations in joint tissues to slight changes in the orientation of impact load on the joint. Interestingly, for this trauma model thickening of the underlying subchondral plate occurred without mechanical degradation of the overlying articular cartilage. This supports the current laboratory hypothesis that alterations in the subchondral bone and overlying cartilage occur independently in this animal model.     

Anti-Osteoarthritic Effects of the Litsea japonica Fruit in a Rat Model of Osteoarthritis Induced by Monosodium Iodoacetate

Osteoarthritis (OA) is a degenerative chronic disease that affects various tissues surrounding the joints, such as the subchondral bone and articular cartilage. The onset of OA is associated with uncontrolled catabolic and anabolic remodeling processes of the joints, including the cartilage and subchondral bone, to adapt to local biological and biochemical signals. In this study, we determined whether 70% ethanolic (EtOH) extract of Litsea japonica fruit (LJFE) had beneficial effects on the articular cartilage, including structural changes in the tibial subchondral bone, matrix degradation, and inflammatory responses, in OA by using a rat model of monosodium iodoacetate-induced OA. Our results showed that administration of LJFE increased the bone volume and cross-section thickness, but the mean number of objects per slice in this group was lower than that in the OA control (OAC) group. In addition, the LJFE decreased the expression of inflammatory cytokines. Compared to the OAC group, the group treated with high doses of LJFE (100 and 200 mg/kg) showed a more than 80% inhibition of the expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases. Our results suggest that LJFE can be used as a potential anti-osteoarthritic agent.     

Parathyroid hormone promotes cartilage healing after free reduction of mandibular condylar fractures by upregulating Sox9

After high fractures of the mandibular condyle, the insufficient blood supply to the condyle often leads to poor bone and cartilage repair ability and poor clinical outcome. Parathyroid hormone (PTH) can promote the bone formation and mineralization of mandibular fracture, but its effects on cartilage healing after the free reduction and internal fixation of high fractures of the mandibular condyle are unknown. In this study, a rabbit model of free reduction and internal fixation of high fractures of the mandibular condyle was established, and the effects and mechanisms of PTH on condylar cartilage healing were explored. Forty-eight specific-pathogen-free (SPF) grade rabbits were randomly divided into two groups. In the experimental group, PTH was injected subcutaneously at 20 µg/kg (PTH (1–34)) every other day, and in the control group, PTH was replaced with 1 ml saline. The healing cartilages were assessed at postoperative days 7, 14, 21, and 28. Observation of gross specimens, hematoxylin eosin staining and Safranin O/fast green staining found that every-other-day subcutaneous injection of PTH at 20 µg/kg promoted healing of condylar cartilage and subchondral osteogenesis in the fracture site. Immunohistochemistry and polymerase chain reaction showed that PTH significantly upregulated the chondrogenic genes Sox9 and Col2a1 in the cartilage fracture site within 7–21 postoperative days in the experimental group than those in the control group, while it downregulated the cartilage inflammation gene matrix metalloproteinase-13 and chondrocyte terminal differentiation gene ColX. In summary, exogenous PTH can stimulate the formation of cartilage matrix by triggering Sox9 expression at the early stage of cartilage healing, and it provides a potential therapeutic protocol for high fractures of the mandibular condyle.     

慢性睡眠限制状态下大鼠髁突软骨MMP-1,MMP-13表达的变化

目的:探讨MMP-1,MMP-13在慢性睡眠限制引起大鼠髁突软骨结构变化中的表达变化及作用。方法:180只雄性Wistar大鼠随机分为3组(n=60):慢性睡眠限制组(CSR)、大平台组(LC)、笼养组(CON)。每组根据试验时间不同分别分为3个亚组(n=20):7天(7D)、14天(14D)、21天(21D)组。参考改良多平台法(MMPM)建立大鼠的慢性睡眠限制模型。通过HE染色观察大鼠髁突软骨的结构变化。通过免疫组化和实时定量PCR分别检测MMP-1和MMP-13的蛋白水平及m RNA水平的表达变化。结果:HE染色和扫描电镜结果显示,CSR组的大鼠髁突软骨出现了病理性的改变。与CON和LC组比较,CSR组MMP-1和MMP-13的m RNA转录和蛋白表达水平明显升高(P0.05)。结论:慢性睡眠限制能够引起大鼠颞下颌关节髁突软骨的病理性变化。MMP-1和MMP-13的表达水平的变化可能在大鼠髁突软骨病理性改变中起关键作用。     

Reduced PDGF-AA in subchondral bone leads to articular cartilage degeneration after strenuous running

To identify the effects of running on articular cartilage and subchondral bone remodeling, C57BL/6 mice were randomly divided into three groups: control, moderate-, and strenuous running. Magnetic resonance imaging showed bone marrow lesions in the knee subchondral bone in the strenuous-running group in contrast with the other two groups. The microcomputed tomography analysis showed promoted bone formation in the subchondral bone in mice subjected to strenuous running. Histological and immunohistochemistry results indicated that terminal differentiation of chondrocytes and degeneration of articular cartilage were enhanced but, synthesis of platelet-derived growth factor-AA (PDGF-AA) in the subchondral bone was suppressed after strenuous running. In vitro, excessive mechanical treatments suppressed the expression of PDGF-AA in osteoblasts, and the condition medium from mechanical-treated osteoblasts stimulated maturation and terminal differentiation of chondrocytes. These results indicate that strenuous running suppresses the synthesis of PDGF-AA in subchondral bone, leading to downregulated PDGF/Akt signal in articular cartilage and thus cartilage degeneration.     

Oxymatrine exerts protective effects on osteoarthritis via modulating chondrocyte homoeostasis and suppressing osteoclastogenesis

Osteoarthritis (OA) is a common degenerative disease characterized by the progressive destruction both articular cartilage and the subchondral bone. The agents that can effectively suppress chondrocyte degradation and subchondral bone loss are crucial for the prevention and treatment of OA. Oxymatrine (OMT) is a natural compound with anti‐inflammatory and antitumour properties. We found that OMT exhibited a strong inhibitory effect on LPS‐induced chondrocyte inflammation and catabolism. To further support our results, fresh human cartilage explants were treated with LPS to establish an ex vivo degradation model, and the results revealed that OMT inhibited the catabolic events of LPS‐stimulated human cartilage and substantially attenuated the degradation of articular cartilage ex vivo. As subchondral bone remodelling is involved in OA progression, and osteoclasts are a unique cell type in bone resorption, we investigated the effects of OMT on osteoclastogenesis, and the results demonstrated that OMT suppresses RANKL‐induced osteoclastogenesis by suppressing the RANKL‐induced NFATc1 and c‐fos signalling pathway in vitro. Further, we found that the anti‐inflammatory and anti‐osteoclastic effects of oxymatrine are mediated via the inhibition of the NF‐κB and MAPK pathways. In animal studies, OMT suppressed the ACLT‐induced cartilage degradation, and TUNEL assays further confirmed the protective effect of OMT on chondrocyte apoptosis. MicroCT analysis revealed that OMT had an attenuating effect on ACLT‐induced subchondral bone loss in vivo. Taken together, these results show that OMT interferes with the vicious cycle associated with OA and may be a potential therapeutic agent for abnormal subchondral bone loss and cartilage degradation in osteoarthritis.     

Pathological mechanism of chondrocytes and the surrounding environment during osteoarthritis of temporomandibular joint

Temporomandibular joint (TMJ) osteoarthritis is a common chronic degenerative disease of the TMJ. In order to explore its aetiology and pathological mechanism, many animal models and cell models have been constructed to simulate the pathological process of TMJ osteoarthritis. The main pathological features of TMJ osteoarthritis include chondrocyte death, extracellular matrix (ECM) degradation and subchondral bone remodelling. Chondrocyte apoptosis accelerates the destruction of cartilage. However, autophagy has a protective effect on condylar chondrocytes. Degradation of ECM not only changes the properties of cartilage but also affects the phenotype of chondrocytes. The loss of subchondral bone in the early stages of TMJ osteoarthritis plays an aetiological role in the onset of osteoarthritis. In recent years, increasing evidence has suggested that chondrocyte hypertrophy and endochondral angiogenesis promote TMJ osteoarthritis. Hypertrophic chondrocytes secrete many factors that promote cartilage degeneration. These chondrocytes can further differentiate into osteoblasts and osteocytes and accelerate cartilage ossification. Intrachondral angiogenesis and neoneurogenesis are considered to be important triggers of arthralgia in TMJ osteoarthritis. Many molecular signalling pathways in endochondral osteogenesis are responsible for TMJ osteoarthritis. These latest discoveries in TMJ osteoarthritis have further enhanced the understanding of this disease and contributed to the development of molecular therapies. This paper summarizes recent cognition on the pathogenesis of TMJ osteoarthritis, focusing on the role of chondrocyte hypertrophy degeneration and cartilage angiogenesis.     

Extracellular matrix changes in early osteochondrotic defects in foals: a key role for collagen?

Osteochondrosis (OC) is the most important developmental orthopaedic disease in the horse. Despite some decades of research, much of the pathogenesis of the disorder remains obscure. Increasing knowledge of articular cartilage development in juvenile animals led to the presumption that the role of collagen in OC might be more important than previously thought. To study collagen characteristics of both cartilage and subchondral bone in young (5 and 11 months of age) horses, samples were taken of subchondral bone and articular cartilage from a group of 43 Dutch Warmblood foals and yearlings that suffered from varying degrees of OC. Based on a histological classification, lesions were graded as early, middle and end stage. Collagen content and some posttranslational modifications (lysyl hydroxylation, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) cross-links) were determined, as was proteoglycan content. Data were compensated for site effects and analysed for differences due to the stage of the lesion. In early lesions total collagen was significantly decreased in both cartilage and subchondral bone of 5- and 11-month-old foals. Also in cartilage, HP cross-linking was reduced in the early lesions of 5- and 11-month-old foals, while LP cross-linking was decreased in subchondral bone of the end-stage lesions of both 5- and 11-month-old foals. Hydroxylysine content was unaffected. Collagen content remained reduced in cartilage from middle- and end-stage lesions, but returned to normal in subchondral bone. In cartilage there was a decrease in proteoglycan content in the end-stage lesions of both age groups. Thus, alterations of the collagen component, but not of the proteoglycan component, of the extracellular matrix might play a role in early OC. More severe lesions show a more general picture of an unspecific repair reaction. Biomarkers of collagen metabolism can be expected to be good candidates for early detection of OC.     

Quantitative Assessment of Murine Articular Cartilage and Bone Using X-Ray Phase-Contrast Imaging

Murine models for rheumatoid arthritis (RA) research can provide important insights for understanding RA pathogenesis and evaluating the efficacy of novel treatments. However, simultaneously imaging both murine articular cartilage and subchondral bone using conventional techniques is challenging because of low spatial resolution and poor soft tissue contrast. X-ray phase-contrast imaging (XPCI) is a new technique that offers high spatial resolution for the visualisation of cartilage and skeletal tissues. The purpose of this study was to utilise XPCI to observe articular cartilage and subchondral bone in a collagen-induced arthritis (CIA) murine model and quantitatively assess changes in the joint microstructure. XPCI was performed on the two treatment groups (the control group and CIA group, n = 9 per group) to monitor the progression of damage to the femur from the knee joint in a longitudinal study (at 0, 4 and 8 weeks after primary injection). For quantitative assessment, morphologic parameters were measured in three-dimensional (3D) images using appropriate image analysis software. Our results showed that the average femoral cartilage volume, surface area and thickness were significantly decreased (P<0.05) in the CIA group compared to the control group. Meanwhile, these decreases were accompanied by obvious destruction of the surface of subchondral bone and a loss of trabecular bone in the CIA group. This study confirms that XPCI technology has the ability to qualitatively and quantitatively evaluate microstructural changes in mouse joints. This technique has the potential to become a routine analysis method for accurately monitoring joint damage and comprehensively assessing treatment efficacy.     

Progression of Cartilage Degradation, Bone Resorption and Pain in Rat Temporomandibular Joint Osteoarthritis Induced by Injection of Iodoacetate

Background

Osteoarthritis (OA) is an important subtype of temporomandibular disorders. A simple and reproducible animal model that mimics the histopathologic changes, both in the cartilage and subchondral bone, and clinical symptoms of temporomandibular joint osteoarthritis (TMJOA) would help in our understanding of its process and underlying mechanism.

Objective

To explore whether injection of monosodium iodoacetate (MIA) into the upper compartment of rat TMJ could induce OA-like lesions.

Methods

Female rats were injected with varied doses of MIA into the upper compartment and observed for up to 12 weeks. Histologic, radiographic, behavioral, and molecular changes in the TMJ were evaluated by light and electron microscopy, MicroCT scanning, head withdrawal threshold test, real-time PCR, immunohistochemistry, and TUNEL assay.

Results

The intermediate zone of the disc loosened by 1 day post-MIA injection and thinned thereafter. Injection of an MIA dose of 0.5 mg or higher induced typical OA-like lesions in the TMJ within 4 weeks. Condylar destruction presented in a time-dependent manner, including chondrocyte apoptosis in the early stages, subsequent cartilage matrix disorganization and subchondral bone erosion, fibrosis, subchondral bone sclerosis, and osteophyte formation in the late stages. Nociceptive responses increased in the early stages, corresponding to severe synovitis. Furthermore, chondrocyte apoptosis and an imbalance between anabolism and catabolism of cartilage and subchondral bone might account for the condylar destruction.

Conclusions

Multi-level data demonstrated a reliable and convenient rat model of TMJOA could be induced by MIA injection into the upper compartment. The model might facilitate TMJOA related researches.     

Characteristics of responses of rabbit joint structures to intraarticular introduction of calcitonin

On a model of autoimmune arthritis in rabbits, reduction of inflammatory-destructive process manifestation was observed in all joint tissues under the influence of the intraarticular introduction of calcitonin. Improving metabolic processes in the matrix of tissue-connecting elements of a joint, this specimen inhibits the inflammatory destruction of the subchondral bone and hyaline cartilage in conditions of experimental rheumatoid inflammation.     

Solute transport at the interface of cartilage and subchondral bone plate: Effect of micro-architecture

Cross-talk of subchondral bone and articular cartilage could be an important aspect in the etiology of osteoarthritis. Previous research has provided some evidence of transport of small molecules (~370 Da) through the calcified cartilage and subchondral bone plate in murine osteoarthritis models. The current study, for the first time, uses a neutral diffusing computed tomography (CT) contrast agent (iodixanol, ~1550 Da) to study the permeability of the osteochondral interface in equine and human samples. Sequential CT monitoring of diffusion after injecting a finite amount of contrast agent solution onto the cartilage surface using a micro-CT showed penetration of the contrast molecules across the cartilage-bone interface. Moreover, diffusion through the cartilage-bone interface was affected by thickness and porosity of the subchondral bone as well as the cartilage thickness in both human and equine samples. Our results revealed that porosity of the subchondral plate contributed more strongly to the diffusion across osteochondral interface compared to other morphological parameters in healthy equine samples. However, thickness of the subchondral plate contributed more strongly to the diffusion in slightly osteoarthritic human samples.     

Adaptation of subchondral bone in osteoarthritis

Osteoarthritis is a chronic joint disease with pathological changes in the articulating cartilage and all other tissues that occupy the joint. Radin and coworkers have suggested the involvement of subchondral bone in the disease process. However, evidence for an essential role in the etiology has never been proven. Recent studies showing reduced chemical and mechanical properties of subchondral bone in various stages of the disease have invigorated interest in the role of subchondral bone in the development and progression of the disease. The current study showed that the concept of bone adaptation might explain subchondral stiffening, a process where subchondral bone becomes typically sclerotic in osteoarthritis. In addition, we report reduced mechanical matrix tissue properties as well as an increase in denatured collagen content. In conclusion, although osteoarthritic bone tissue contains increased denatured collagen and has reduced matrix mechanical properties, the widely accepted concept of subchondral stiffening is compatible with the process of normal bone adaptation.     

Mandibular repositioning modulates IGFBP-3, -4, -5 and -6 expression in the mandibular condylar cartilage of young rats

Functional orthopedic appliances correct dental malocclusion partially by exerting indirect mechanical stimulus on the condylar cartilage, modulating growth and the adaptation of orofacial structures. However, the exact nature of the biological responses to this therapy is not well understood. Insulin-like growth factors I and II (IGF-I and II) are important local factors during growth and differentiation in the condylar cartilage [D. Hajjar, M.F. Santos and E.T. Kimura, Propulsive appliance stimulates the synthesis of insulin-like growth factors I and II in the mandibular condylar cartilage of young rats, Arch. Oral Biol. 48 (2003), 635-642]. The bioefficacy of IGFs at the cellular level is modulated by IGF binding proteins (IGFBP). The aim of this study was to verify the mRNA and protein expression of IGFBP-3, IGFBP-4, IGFBP-5 and IGFBP-6 in the condylar cartilage of young male Wistar rats that used a mandibular propulsive appliance for 3, 9, 15, 20, 30 or 35 days. For this purpose, sagittal sections of decalcified and paraffin-embedded condyles were submitted to immunohistochemistry and the condylar cartilage to RT-PCR. The control group showed a gradual increase in the protein expression of all IGFBPs, except IGFBP-4. Following use of the appliance, IGFBP-3 and IGFBP-6 expression decreased in the early stage of the treatment. At 20 days of treatment there was a decline in the IGFs and IGFBP-3, IGFBP-4 and IGFBP-5 expression and at 30 days there was a peak in the IGFs and all IGFBPs expression except for IGFBP-3 where the peak was observed in the control animals. The expression patterns of all IGFBPs in the condylar cartilage were similar. The modulation of IGFBP-3, -4, -5 and -6 expression in the condylar cartilage in response to the propulsive appliance suggests that those peptides are involved in the mandibular adaptation during this therapy.     

Swelling of articular cartilage depends on the integrity of adjacent cartilage and bone

Articular cartilage swells when its collagen network is degraded, both in osteoarthritis (OA) and following mechanical trauma. However, most of the experimental evidence actually shows that it is small excised samples of cartilage that swell, implying that the cartilage was not greatly swollen in-situ before it was excised. We hypothesise that degraded cartilage can be prevented from swelling in-situ by restraint from adjacent normal cartilage and subchondral bone. Four adjacent osteochondral specimens, 20 x 20 mm, were obtained from regions of the humeral heads of each of 11 skeletally-mature cows. The central region of each specimen was injured by compressive loading using a 9 mm-diameter flat metal indenter, and cartilage surface damage was confirmed using Indian ink. Damaged cartilage was allowed to swell in physiological saline for 1 h under one of four conditions of restraint: (A) normal in-situ restraint from subchondral bone and surrounding cartilage, (B) restraint from bone only, (C) restraint from cartilage only, (D) no restraint (excised specimen). Cartilage hydration was assessed by freeze-drying to constant weight. Proteoglycan loss from damaged cartilage was quantified by analyzing the GAG content of the surrounding bath using the DMB assay. Hydration of damaged cartilage after swelling depended on restraint (p < 0.001), averaging: (A) 76.8%, (B) 78.2%, (C) 78.0%, (D) 81.3%. GAG loss following cartilage surface damage was insufficient to explain observed differences in hydration. The 6% increase in hydration between (A) and (D) can be attributed to swelling which is prohibited when the cartilage remains in-situ. Swelling of degraded cartilage can be largely prevented if it remains in-situ, supported by adjacent healthy bone and cartilage. Adverse physico-chemical consequences of cartilage degradation and swelling may become apparent only when this support is diminished, either because the affected region is large, or following deterioration of adjacent bone or cartilage.     

富血小板血浆注射治疗在膝骨关节炎中的应用进展

富血小板血浆(platelet-rich plasma，PRP)由于富含多种活性生长因子，能够刺激软骨细胞增殖，促进软骨前体细胞增殖、迁移、向软骨细胞分化，促进胶原蛋白合成以及抑制软骨的炎性反应和退变，提供有利于组织修复的内环境，延缓病情进展。近年来PRP注射治疗已成为治疗与骨关节炎(osteoarthritis，OA)相关疾病的新型选择，并且疗效显著。为了进一步提高其效用，PRP注射治疗不仅在关节腔内进行，还可在软骨下骨内进行注射。软骨下骨的病变会加速软骨损耗，故有必要将软骨下骨也当作OA众多发病机制和病理过程的关键因素之一。根据PRP的生物特效以及PRP注射治疗在膝骨关节炎(knee osteoarthritis，KOA)中应用的研究进展进行了综述，同时对软骨下骨内PRP注射治疗KOA的研究进行了展望，以期为KOA的治疗提供更加有效的方法。     

Imaging of experimental osteoarthritis in small animal models

Normally, tissue alterations in small animal models for osteoarthritis (OA) are assessed by time-consuming and destructive histology or biochemical assays. Some high resolution imaging modalities are used for longitudinal monitoring of the OA disease process in vivo. microCT is one of these imaging modalities, which is known for superb high-resolution imaging of bone architecture alterations. A major drawback of microCT is that it has low soft-tissue contrast, which makes direct imaging of cartilage impossible. The use of microCT in combination with negatively charged radiopaque contrast agents enables imaging of cartilage degeneration. We demonstrate the possibility of microCT to image cartilage degeneration as a consequence of experimental OA, by the use contrast enhanced microCT in vivo in a rat model for OA. Furthermore, for the assessment of alterations in molecular processes involved in OA we used the recently developed technique of multi pinhole SPECT. This enables us to assess molecular processes involved in experimental OA in a rat at sub-millimeter level. Here we show quantification of subchondral bone turnover in an OA rat knee. These new techniques demonstrate the possibilities of quantitative experimental OA assessment in small animal models such as mice and rats and might enable substitution of the conventional destructive methods.     

Sequential Change in T2* Values of Cartilage,Meniscus, and Subchondral Bone Marrow in a Rat Model of Knee Osteoarthritis

Background

There is an emerging interest in using magnetic resonance imaging (MRI) T2* measurement for the evaluation of degenerative cartilage in osteoarthritis (OA). However, relatively few studies have addressed OA-related changes in adjacent knee structures. This study used MRI T2* measurement to investigate sequential changes in knee cartilage, meniscus, and subchondral bone marrow in a rat OA model induced by anterior cruciate ligament transection (ACLX).

Materials and Methods

Eighteen male Sprague Dawley rats were randomly separated into three groups (n = 6 each group). Group 1 was the normal control group. Groups 2 and 3 received ACLX and sham-ACLX, respectively, of the right knee. T2* values were measured in the knee cartilage, the meniscus, and femoral subchondral bone marrow of all rats at 0, 4, 13, and 18 weeks after surgery.

Results

Cartilage T2* values were significantly higher at 4, 13, and 18 weeks postoperatively in rats of the ACLX group than in rats of the control and sham groups (p<0.001). In the ACLX group (compared to the sham and control groups), T2* values increased significantly first in the posterior horn of the medial meniscus at 4 weeks (p = 0.001), then in the anterior horn of the medial meniscus at 13 weeks (p<0.001), and began to increase significantly in the femoral subchondral bone marrow at 13 weeks (p = 0.043).

Conclusion

Quantitative MR T2* measurements of OA-related tissues are feasible. Sequential change in T2* over time in cartilage, meniscus, and subchondral bone marrow were documented. This information could be potentially useful for in vivo monitoring of disease progression.