Haem oxygenase-1 regulates catabolic and anabolic processes in osteoarthritic chondrocytes

Pro-inflammatory cytokines, matrix metalloproteinases (MMPs) and other catabolic factors participate in the pathogenesis of cartilage damage in osteoarthritis (OA). Pro-inflammatory cytokines such as interleukin-1beta (IL-1beta) mediate cartilage degradation and might be involved in the progression of OA. Previously, we found that haem oxygenase-1 (HO-1) is down-regulated by pro-inflammatory cytokines and up-regulated by IL-10 in OA chondrocytes. The aim of this study was to determine whether HO-1 can modify the catabolic effects of IL-1beta in OA cartilage and chondrocytes. Up-regulation of HO-1 by cobalt protoporphyrin IX significantly reduced glycosaminoglycan degradation elicited by IL-1beta in OA cartilage explants but increased glycosaminoglycan synthesis and the expression of collagen II in OA chondrocytes in primary culture, as determined by radiometric procedures, immunoblotting and immunocytochemistry. HO-1 decreased the activation of extracellular signal-regulated kinase 1/2. This was accompanied by a significant inhibition in MMP activity and expression of collagenases MMP-1 and MMP-13 at the protein and mRNA levels. In addition, HO-1 induction caused a significant increase in the production of insulin-like growth factor-1 and a reduction in the levels of insulin-like growth factor binding protein-3. We have shown in primary culture of chondrocytes and articular explants from OA patients that HO-1 counteracts the catabolic and anti-anabolic effects of IL-1beta. Our data thus suggest that HO-1 may be a factor regulating the degradation and synthesis of extracellular matrix components in OA.     

Metalloproteinase production by rabbit articular cartilage: comparison of the effects of interleukin-1α in vitro and in vivo

To assess the effects of interleukin-1 on intact articular cartilage in vitro, explants from young and adult rabbits were cultured with interleukin-1 and the distributions of the matrix metalloproteinases and tissue inhibitor of metalloproteinases (TIMP-1) were investigated by indirect immunofluorescence microscopy. One to 2-week-old cartilage chondrocytes synthesized collagenase in response to pure or crude interleukin-1 (monocyte conditioned medium), with subarticular cells most responsive. Collagenase synthesis was not stimulated in adult articular chondrocytes when explants were treated with either pure or crude interleukin-1. Stromelysin, gelatinase and TIMP-1 could not be demonstrated within any zone of the cartilage, indicating that their synthesis was not stimulated by either pure or crude interleukin-1. The addition of fibroblast growth factors, either alone or in combination with interleukin-1, did not modify these responses. These results contrast markedly with observations on cultured chondrocyte monolayers, where interleukin-1 treatment induces near co-ordinate expression of metalloproteinases. To assess the effects of interleukin-1 in vivo, it was injected into adult rabbit knee joint spaces and the articular cartilage subsequently analysed for evidence of altered metalloproteinase production by immunocytochemistry. No significant increase in metalloproteinase or TIMP-1 synthesis by chondrocytes was detected, although the cartilage matrix showed a marked loss of toluidine blue metachromasia. We conclude that metalloproteinases are not involved in the rapid loss of proteoglycan from cartilage matrix in these situations.     

Matrine inhibits IL-1β-induced expression of matrix metalloproteinases by suppressing the activation of MAPK and NF-κB in human chondrocytes in vitro

Interleukin (IL)-1β plays an important role in promoting osteoarthritis (OA) lesions by inducing chondrocytes to secrete matrix metalloproteinases (MMPs), which degrade the extracellular matrix and facilitate chondrocyte apoptosis. Matrine was shown to exert anti-inflammatory effects. However, the role of matrine in OA is still unclear. Therefore, in this study, we investigated the effects of matrine on the expression of MMPs in IL-1β-treated human chondrocytes and the underlying mechanism. The cell viability of chondrocytes was detected by MTT assay. The cell apoptosis of chondrocytes was measured by flow cytometric analysis. The protein production of MMPs was determined by ELISA. The protein expression of phosphorylation of mitogen-activated protein kinases (MAPKs) and the inhibitor of kappaB alpha (IκBα) was determined by Western blot. Matrine significantly inhibited the IL-1β-induced apoptosis in chondrocytes. It also significantly inhibited the IL-1β-induced release of MMP-3 and MMP-13, and increased the production of TIMP-1. Furthermore, matrine inhibits the phosphorylation of p-38, extracellular regulated kinase (ERK), c-Jun-N-terminal kinase (JNK) and IκBα degradation induced by IL-1β in chondrocytes. Taken together, our results show that matrine inhibits IL-1β-induced expression of matrix metalloproteinases by suppressing the activation of MAPK and NF-κB in human chondrocytes in vitro. Therefore,-matrine may be beneficial in the treatment of OA.     

Standardized butanol fraction of WIN-34B suppresses cartilage destruction via inhibited production of matrix metalloproteinase and inflammatory mediator in osteoarthritis human cartilage explants culture and chondrocytes

Background

WIN-34B is a novel Oriental medicine, which represents the n-butanol fraction prepared from dried flowers of Lonicera japonica Thunb and dried roots of Anemarrhena asphodeloides BUNGE. The component herb of WIN-34B is used for arthritis treatment in East Asian countries. The aim of this study was to determine the cartilage-protective effects and mechanisms of WIN-34B and its major phenolic compounds, chlorogenic acid and mangiferin, in osteoarthritis (OA) human cartilage explants culture and chondrocytes.

Methods

The investigation focused on whether WIN-34B and its standard compounds protected cartilage in interleukin (IL)-1β-stimulated cartilage explants culture and chondrocytes derived from OA patients. Also, the mechanisms of WIN-34B on matrix metalloproteinases (MMPs), tissue inhibitor of matrix metalloproteinases (TIMPs), inflammatory mediators, and mitogen-activated protein kinases (MAPKs) pathways were assessed.

Results

WIN-34B was not cytotoxic to cultured cartilage explants or chondrocytes. WIN-34B dose-dependently inhibited the release of glycosaminoglycan and type II collagen, increased the mRNA expression of aggrecan and type II collagen, and recovered the intensity of proteoglycan and collagen by histological analysis in IL-1β-stimulated human cartilage explants culture. The cartilage protective effect of WIN-34B was similar to or better than that of chlorogenic acid and mangiferin. Compared to chlorogenic acid and mangiferin, WIN-34B displayed equal or greater decreases in the levels of MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5, and markedly up-regulated TIMP-1 and TIMP-3. WIN-34B inhibited inflammatory mediators involved in cartilage destruction, such as prostaglandin E2, nitric oxide, tumor necrosis factor-alpha, and IL-1β. The phosphorylation of extracellular signal-regulated kinase, c-Jun N-terminal kinase (JNK), and p38 was significantly reduced by WIN-34B treatment, while phosphorylation of JNK was only inhibited by chlorogenic acid or mangiferin in IL-1β-stimulated chondrocytes.

Conclusions

WIN-34B is potentially valuable as a treatment for OA by virtue of its suppression of MMPs, ADAMTSs, and inflammatory mediators, and it’s up-regulation of TIMP-1 and TIMP-3 involved in the MAPK pathway.

     

Increased matrix metalloproteinases as possible cause of osseoarticular tissue destruction in long-term haemodialysis and β2-microglobulin amyloidosis

Immunolocalization of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in periarticular tissues of ₂-microglobulin amyloidosis patients was investigated. MMP-1 (interstitial collagenase) the most strongly expressed of the MMPs, was localized in the synovial lining cells, mesenchymal cells in granulation tissue and nodular amyloid deposits, and chondrocytes within areas of cartilage erosion. Expression of MMP-1 was correlated with the degree of macrophage infiltration and synovial cell hyperplasia, but it was not correlated with the degree of amyloid deposition or haemodialysis period. Expression of MMP-1 appeared more intense than that of TIMP-1 and TIMP-2 in highly inflammatory cases. MMP-2 was mildly expressed in the interstitial fibroblasts and MMP-3 was faintly stained in the extracellular matrix of the synovial membrane. MMP-9 (gelatinase B) was found to be strongly positive in the osteoclasts which increased in the progressing osteolytic lesion from the destructive arthropathy. These results suggest involvement of MMPs in inflammation with an imbalance between expression of MMPs and TIMPs being closely related to pathogenesis of the destructive arthropathy.     

Moderate Joint Loading Reduces Degenerative Actions of Matrix Metalloproteinases in the Articular Cartilage of Mouse Ulnae

Joint loading is a recently developed loading modality, which can enhance bone formation and accelerate healing of bone fracture. Since mechanical stimulation alters expression of matrix metalloproteinases (MMPs) in chondrocytes, a question addressed herein was, does joint loading alter actions of MMPs in the articular cartilage? We hypothesized that expression and activity of MMPs are regulated in a load–intensity-dependent manner and that moderate load scan downregulates MMPs. To test this hypothesis, a mouse elbow-loading model was employed. In the articular cartilage of an ulna, the mRNA levels of a group of MMPs as well as their degenerative activities were determined. The result revealed that elbow loading altered the expression and activities of MMPs depending on its loading intensity. Collectively, the data in this study indicate that 0.2 and 0.5 N joint loading significantly reduced the expression of multiple MMPs, that is, MMP-1, MMP-3, MMP-8, and MMP-13, and overall activities of collagenases or gelatinases in articular cartilage, while higher loads increased the expression and activity of MMP-1 and MMP-13. Furthermore, moderate loads at 1 N elevated the mRNA level of CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2), but higher loads at 4 N did not induce a detectable amount of CITED2 mRNA. Since CITED2 is known to mediate the downregulation of MMP-1 and MMP-13, the result indicates that joint loading at moderate intensity reduces MMP activities through potential induction of CITED2. MMPs such as MMP-1 and MMP-13 are predominant collagenases in the pathology of osteoarthritis. Therefore, joint loading could offer an interventional regimen for maintenance of joint tissues.     

Moderate joint loading reduces degenerative actions of matrix metalloproteinases in the articular cartilage of mouse ulnae

Joint loading is a recently developed loading modality, which can enhance bone formation and accelerate healing of bone fracture. Since mechanical stimulation alters expression of matrix metalloproteinases (MMPs) in chondrocytes, a question addressed herein was, does joint loading alter actions of MMPs in the articular cartilage? We hypothesized that expression and activity of MMPs are regulated in a load-intensity-dependent manner and that moderate load scan downregulates MMPs. To test this hypothesis, a mouse elbow-loading model was employed. In the articular cartilage of an ulna, the mRNA levels of a group of MMPs as well as their degenerative activities were determined. The result revealed that elbow loading altered the expression and activities of MMPs depending on its loading intensity. Collectively, the data in this study indicate that 0.2 and 0.5?N joint loading significantly reduced the expression of multiple MMPs, that is, MMP-1, MMP-3, MMP-8, and MMP-13, and overall activities of collagenases or gelatinases in articular cartilage, while higher loads increased the expression and activity of MMP-1 and MMP-13. Furthermore, moderate loads at 1 N elevated the mRNA level of CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2), but higher loads at 4 N did not induce a detectable amount of CITED2 mRNA. Since CITED2 is known to mediate the downregulation of MMP-1 and MMP-13, the result indicates that joint loading at moderate intensity reduces MMP activities through potential induction of CITED2. MMPs such as MMP-1 and MMP-13 are predominant collagenases in the pathology of osteoarthritis. Therefore, joint loading could offer an interventional regimen for maintenance of joint tissues.     

Effects of tetracyclines on the production of matrix metalloproteinases and plasminogen activators as well as of their natural inhibitors, tissue inhibitor of metalloproteinases-1 and plasminogen activator inhibitor-1

OBJECTIVE: Evaluation of tetracycline effects on the expression of MMP-1, MMP-3, tissue inhibitor(s) of metalloproteinase-1 (TIMP-1), plasminogen activators (PA), and PA inhibitor-1, which are all involved in the ultimate regulation of MMP activity could provide new insight into how tetracyclines achieve their cartilage preserving effects. MATERIALS AND METHODS: We used bovine articular chondrocytes cultured in alginate gel beads for our studies which were initially treated with 10 microM tetracyclines in the presence of IL-1. Only significant effects were studied at additional concentrations. Expression of mRNA was analyzed by RT-PCR-ELISA. The activity of enzymes and TIMP was measured by functional assays; whereas, the level of PAI-1 was determined by ELISA. RESULTS: Treating chondrocytes with IL-1 induced the expression of MMPs and downregulated TIMP-1 but stimulated both the expression of PAs and PAI-1. When tested at 10 microM only minocycline reduced collagenase activity and expression of MMP-1. Further pharmacokinetic analysis revealed IC50 values of 26 microM and 16 microM for the inhibition of collagenase activity and mRNA expression, respectively. Production of MMP-3 was only decreased by tetracycline (IC50 = 45.4 microM). No effects of tetracyclines could be observed on proteoglycan degradation, TIMP activity and the production of PAs, PAI-1, and TIMP-1. CONCLUSIONS: We conclude that the inhibition of MMPs by tetracyclines occurs mainly via down-regulation of the respective gene expression.     

Anti-arthritic effects of crocin in interleukin-1β-treated articular chondrocytes and cartilage in a rabbit osteoarthritic model

Objective

Interleukin-1β-mediated production of matrix metalloproteinases (MMPs) plays a pivotal role in the process of osteoarthritis. Crocin, a pharmacologically active component of Crocus sativus L. (saffron), has been used in Chinese traditional medicine. In this study, we aimed to investigate the effects of crocin on MMP-1, MMP-3 and MMP-13 expression in rabbit chondrocytes induced by interleukin-1β (IL-1β) and in an experimental rabbit model induced by anterior cruciate ligament transection.

Methods

Chondrocytes isolated from the articular cartilage of 4-week-old rabbits were cultured and passaged. Confluent chondrocytes were treated with various concentrations of crocin in the presence or absence of IL-1β (10 ng/ml) for 24 h. Quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blotting were used to investigate the expression of inducible MMP-1, MMP-3 and MMP-13. In addition, the in-vivo effects of crocin were assessed by morphological and histological analysis.

Results

IL-1β markedly upregulated the expression of MMP-1, -3 and -13 in chondrocytes, and this activation was inhibited by co-incubation with crocin in a dose-dependent manner, in contrast with the control group. Moreover, crocin inhibited IL-1β-induced activation of the nuclear factor kappa B pathway through suppressing degradation of inhibitory-kappa-B-α. In-vivo investigations showed that crocin ameliorated cartilage degeneration and that expression of the MMP-1, -3 and -13 genes in cartilage was significantly inhibited by crocin.

Conclusion

Taken together, our findings suggest that the anti-inflammatory activity of crocin may be of potential value in the prevention and treatment of osteoarthritis.     

Human chondrocytes differentially express matrix modulators during in vitro expansion for tissue engineering

Cartilage tissue engineering plays an important role in the generation of grafts for reconstructive surgery. In cultured chondrocytes, the dedifferentiation of cells seems unavoidable for multiplication. Dedifferentiated cells produce matrix of less quality, and the molecular basis is still not well understood. Therefore, the aim of our study was to investigate the expression of matrix modulators in human chondrocytes during expansion. Human chondrocytes were isolated from septal cartilage (n=32) and held in primary cell culture. Cells were harvested after 1, 6 and 21 days. The differentiation of cells using light microscopy, the expression patterns of various proteins (MMPs, BMPs, and TIMPs) using immunohistochemistry, and the expression of distinct genes using microarray technique, were investigated. The chondrocytes showed strong in vitro proliferation. After 6 and 21 days, BMP-5 and -8 were up-regulated, BMP-2 was down-regulated and BMP-6 was inactivated. Other BMPs were not expressed. The expression of MMP-2, -3 and -13 was up-regulated from day 1 to 21, and MMP-12 and -20 were down-regulated. Other MMPs were not expressed. TIMP-1 was up-regulated and TIMP-3 was down-regulated during expansion. Differential expression of matrix modulators might influence the matrix composition of engineered cartilage. Improving the basic knowledge in this area may ultimately help clinicians to identify and proactively intervene in an attempt to prevent bioartificial cartilage from losing stability.     

Inhibition of histone deacetylases antagonized FGF2 and IL-1β effects on MMP expression in human articular chondrocytes

Fibroblast growth factor-2 (FGF2) and interleukin-1β (IL-1β) stimulate the expression of matrix metalloproteinases (MMPs) in articular chondrocytes, which may contribute to cartilage degradation and development of osteoarthritis. Histone deacetylases (HDACs) have recently been implicated in the regulation of MMP gene expression. To investigate the functional involvement of HDACs in the signaling pathway of FGF2 and IL-1β, we examined the effects of HDAC inhibition on activities of FGF2 or IL-1β on gene expression of MMP-1, MMP-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS5), collagen type II, and aggrecan. Human articular chondrocyte cultures were treated with FGF2 or IL-1β in the presence or absence of HDAC inhibitor (trichostatin A, TSA). Gene expression levels after treatments were assessed using quantitative real time PCR. Results showed that FGF2 and IL-1β both increased MMP-1 and -13 expression, while IL-1β also increased MMP-3 mRNA levels. These effects were attenuated in the presence of TSA in a dose dependent manner. In contrast to the effects on MMPs, FGF2 decreased mRNA levels of ADAMTS-5, which was not affected by HDAC inhibition. FGF2, IL-1β, and TSA inhibited expression of aggrecan, while TSA also decreased mRNA levels of collagen type II. These findings showed that HDAC inhibition antagonized FGF2 and IL-1β induced MMP expression. Combination of FGF2 and the HDAC inhibitor decreases both anabolic and catabolic genes, which may slow the cartilage turnover and be beneficial for maintaining cartilage integrity.     

Matrix Metalloproteinase Activity in Pediatric Acute Lung Injury

Pediatric Acute Lung Injury (ALI) is associated with a high mortality and morbidity, and dysregulation of matrix metalloproteinases (MMPs) may play an important role in the pathogenesis and evolution of ALI. Here we examined MMP expression and activity in pediatric ALI compared with controls. MMP-8, -9, and to a lesser extent, MMP-2, -3, -11 and -12 were identified at higher levels in lung secretions of pediatric ALI patients compared with controls. Tissue Inhibitor of Matrix metalloproteinase-1 (TIMP-1), a natural inhibitor of MMPs was detected in most ALI samples, but MMP-9:TIMP-1 ratios were high relative to controls. In subjects who remained intubated for ≥10 days, MMP-9 activity decreased, with > 80% found in the latent form. In contrast, almost all MMP-8 detected at later disease course was constitutively active. Discriminating MMP-9:TIMP-1 ratios were found in those who had a prolonged ALI course. These results identify a specific repertoire of MMP isoforms in the lung secretions of pediatric ALI patients, and demonstrate inverse changes in MMPs -8 and -9 with protracted disease.     

Progesterone receptor modulator CDB-2914 induces extracellular matrix metalloproteinase inducer in cultured human uterine leiomyoma cells

Effects of progesterone receptor modulator CDB-2914 on the expression of the extracellular matrix (ECM) components were examined in cultured human uterine leiomyoma and myometrial cells. ECM metalloproteinase inducer (EMMPRIN), matrix metalloproteinases (MMPs), tissue inhibitors of MMP (TIMPs) and collagen levels were assessed by Western blot analysis, MMP activity assay and real-time RT-PCR. RNA interference (RNAi) of EMMPRIN was performed using small interfering mRNA. In cultured leiomyoma cells, CDB-2914 treatment at concentrations greater than or equal to 10(-8) M significantly increased EMMPRIN, MMP-1 and MMP-8 protein contents and MMP-1, MMP-2, MMP-3 and MMP-9 mRNA levels, and activity of MMP-1, MMP-2, MMP-3 and MMP-9 in the medium. TIMP-1 and TIMP-2 were significantly decreased at mRNA and protein levels by CDB-2914 treatment at concentrations > or =10(-7) M in these cells. CDB-2914 treatment decreased types I and III collagen protein contents. However, CDB-2914 treatment did not affect the ECM component expression in cultured myometrial cells. RNAi of EMMPRIN abrogated CDB-2914-mediated both induction of MMPs and reduction of TIMPs and collagens in cultured leiomyoma cells. These results suggest that CDB-2914 modulates the expression of EMMPRIN, MMPs, TIMPs and collagens in cultured leiomyoma cells without comparable effects on myometrial cells.     

The effects of mycotoxins and selenium deficiency on tissue-engineered cartilage

Objective: To investigate the effects of 3 mycotoxins, deoxynivalenol (DON), nivalenol (NIV) and T-2 toxin, in the presence and absence of selenium (Se) on the metabolism of tissue-engineered cartilage to mimic conditions found in Kashin-Beck disease (KBD) environments. Materials and Methods: Chondrocytes were seeded onto bone matrix gelatin (BMG) to construct engineered cartilage. The 3 toxins were added to the culture media for 3 weeks followed by immunhistochemical analyses of collagens type II and X, aggrecan, matrix metalloproteinases 1 and 3 (MMP-1 and MMP-3), MMP inhibitors 1 and 3 (TIMP-1 and TIMP-3) and α(2) macroglobulin (α2M). Results: Type II collagen was decreased while type X collagen was increased in response to DON, NIV and T-2 toxin. Aggrecan was reduced by all 3 mycotoxins. Compared with the control, the 3 toxins decreased the expression of α2M, TIMP-1 and TIMP-3, and increased the expression of MMP-1 and MMP-3. Se could partially inhibit the effects of DON, NIV and T-2 toxins. Conclusion: Under the low Se condition, the 3 mycotoxins produced procatabolic changes in cartilage resulting in the loss of aggrecan and type II collagen and promoted a hypertrophic phenotype of chondrocytes characterized by increasing type-X-collagen expression, enhancing the expression of MMPs, while weakening the TIMPs. Se could partially block the effects mentioned above. These results support the hypothesis that the combination of mycotoxin stress and Se deficiency would be the causative factors for KBD.     

Expression of transforming growth factor-beta 1 by pancreatic stellate cells and its implications for matrix secretion and turnover in chronic pancreatitis

Pancreatic stellate cells mediate fibrosis in chronic pancreatitis. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs)-1 and -2 are crucial modulators of fibrosis. Transforming growth factor-beta (TGF-beta) is a key regulator of extracellular matrix production and myofibroblast proliferation. We have examined MMP and TIMP synthesis by transformed cultured pancreatic stellate cells and their regulation by TGF-beta 1. By Northern analysis they expressed mRNAs for procollagen 1, TIMP-1, TIMP-2, and MMP-2. Expression of membrane type-1 MMP was confirmed by Western blotting. By immunohistochemistry these enzymes localized to fibrotic areas in human chronic pancreatitis. Active TGF-beta 1 constitutes 2 to 5% of total TGF-beta 1 secreted by pancreatic stellate cells; they express TGF-beta receptors I and II. Exogenous TGF-beta 1 (10 ng/ml) significantly increased procollagen-1 mRNA by 69% and collagen protein synthesis by 34%. Similarly TGF-beta 1 at 0.1, 1, and 10 ng/ml significantly reduced cellular proliferation rate by 37%, 44%, and 44%, respectively, whereas pan-TGF-beta-neutralizing antibody increased proliferation by 40%. TGF-beta1 (10 ng/ml) down-regulated MMP-9 by 54% and MMP-3 by 34% whereas TGF-beta 1-neutralizing antibody increased MMP-9 expression by 39%. Pancreatic stellate cells express both mediators of matrix remodeling and the regulatory cytokine TGF-beta 1 that, by autocrine inhibition of MMP-3 and MMP-9, may enhance fibrogenesis by reducing collagen degradation.     

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in joint fluid of the patients with loose artificial hip joints.

The pseudojoint cavity formed in patients undergoing total hip arthroplasty (THA) is later remodeled to synovial membrane-like tissue, which produces pseudosynovial fluid. This pseudosynovium also is an important source of matrix metalloproteinases (MMPs). As it is widely speculated that synovial fluid MMPs may contribute to local tissue degradation in rheumatoid arthritis (RA) and osteoarthritis (OA), we hypothesize that locally produced MMPs are found in the pseudosynovial fluid, via which they have access to the implant-host interface, and that if they retain their proteolytic potential, they might contribute to aseptic loosening. Enzyme-linked immunosorbent assay (ELISA), immunoblotting, and zymography were used to analyze MMPs and tissue inhibitors of metalloproteinases (TIMPs) in synovial fluid in aseptic loosening, which was compared to RA and OA. Pseudosynovial THA fluid was characterized using low levels of MMP-1 but moderate levels of MMP-13 and MT1-MMP (MMP-14). Due to the lack of an appropriate assay, MMP-13 and MT1-MMP were not similarly assessed, but the immunoblotting indicated that they were in the 56 kD intermediate proteolytically processed forms. The MMP-9 level was intermediate between RA and OA. MMP-2 was on a significant level, but there were no differences among study groups. The THA group also was characterized using relatively high levels of TIMP-1 and TIMP-2. Accordingly, MMP-9 and MMP-2 were found to occur in the 92 kD and 72 kD proenzyme form, respectively, with full activity retained in all study groups. The data suggest that proMMP-2-TIMP-2 and proMMP-9-TIMP-1 complexes are formed in the pseudosynovial fluid due to the excess of TIMPs over MMPs in aseptic loosening of THA. TIMP-complexed MMPs are resistant to MMP-mediated proteolytic activation, which may explain their latency and proenzyme zymogen form. Thus, formation of stabilizing proMMP-TIMP complexes enable transportation of proMMPs far from their original site of production. Due to motion-associated cyclic changes of the intra-articular pressure, fluid-phase MMPs stabilized by TIMPs might be absorbed to implant surfaces and interface tissues and help to dissect the implant/cement-to-bone interface in situ. Consequently, they may contribute to local proteolytic/tissue destructive events and aseptic loosening.     

创伤性关节炎软骨中基质金属蛋白酶13及组织特异性抑制剂1的表达*

背景：关节软骨损伤后继发性退变机制仍不十分清楚。近年研究发现关节软骨细胞外基质合成与降解失衡是造成软骨变性的重要原因之一,其中基质金属蛋白酶可能起决定性的作用。 目的：观察基质金属蛋白酶13及其组织特异性抑制剂1在创伤性关节炎中的表达及与软骨退变的关系。 方法：将新西兰兔分别用骨水泥制作的模具从1.33 kg,46 cm高度和0.43 kg,20 cm高度进行自由落体撞击制备轻型和重型撞击创伤性关节炎兔模型。 结果与结论：苏木精-伊红染色和免疫组织化学染色结果显示,基质金属蛋白酶13和组织特异性抑制剂1在两组均增高(P < 0.05)。组织特异性抑制剂1在重型撞击创伤性关节炎模型兔软骨组织中的分泌明显高于轻型撞击组(P < 0.05)。说明关节软骨在创伤后,基质金属蛋白酶13及组织特异性抑制剂1表达上调,共同作用促进了关节软骨退变,其中组织特异性抑制剂1的过量表达可能是造成关节软骨进一步损害的原因之一。