共抑制分子PD-1在类风湿关节炎模型免疫系统及滑膜组织的表达

目的:探讨共抑制分子PD-1在牛二型胶原(CII)诱导的类风湿关节炎模型(CIA)小鼠免疫器官、关节及RA患者滑膜组织内的表达.方法:使用牛二型胶原免疫DBA-1/j小鼠,建立小鼠类风湿关节炎模型;免疫组化检测类风湿关节炎标本PD-1的表达变化;流式细胞分析术(FACs)检测对PD-1阳性细胞进行定位.结果:免疫组化的结果证实,小鼠的骨髓、胸腺、脾脏及淋巴结有中有大量的PD-1阳性细胞,FACs分析结果表明这些PD-1+ 细胞主要为CD3+T细胞,B220+B细胞,CD68+巨噬细胞及CD11c+树突状细胞,统计分析表明CIA小鼠体内PD-1表达及分布相对于对照组小鼠没有显著提高.此外,RA患者及CIA小鼠的滑膜组织内仅发现少量PD-1阳性的细胞. 结论:PD-1阳性细胞可能不参与类风湿性关节炎的发生发展过程.     

青藤碱抑制CaN / NFAT 通路信号抑制CIA 骨破坏的研究

目的:从钙调神经磷酸酶/活化T细胞核因子(CaN/NFAT)通路探讨青藤碱(SIN)对胶原诱导性关节炎(CIA)小鼠骨破坏的作用。方法:C57BL/6小鼠60只,随机选取6只为正常组(C组),其余小鼠为造模组。造模组小鼠以牛Ⅱ型胶原(CⅡ)和完全弗氏佐剂的混合乳化剂为抗原尾根部注射,3周后加强免疫,取CⅡ与等体积的不完全弗氏佐剂混合尾根部注射,建立CIA模型。造模成功后,随机分为模型组(M组)、SIN低剂量组(SL组)、SIN高剂量组(SH组)各9只。初次免疫后第31天起,SL组、SH组分别给予SIN 30 mg/kg、300 mg/kg灌胃,连续12 d,每日1次,C组、M组给予等体积的生理盐水。观察小鼠关节肿胀程度并评估关节炎指数(AI);HE染色观察小鼠踝关节病理变化并评价;免疫组化检测CIA小鼠踝关节切片CaNAα、NFAT蛋白表达水平;Western blot检测CIA小鼠滑膜组织CaNAα、NFAT蛋白表达水平。结果:与C组相比,M组关节AI指数、炎症细胞浸润、软骨及骨破坏评分、CaNAα、NFAT蛋白表达均明显升高(P0.05或P0.01);与M组相比,SL、SH组的AI指数、炎症细胞浸润、骨及软骨破坏评分、CaNAα、NFAT蛋白水平均明显降低(P0.05或P0.01),且呈剂量依赖性。结论:SIN可能通过抑制CaN/NFAT信号通路,抑制破骨细胞分化,改善CIA小鼠骨破坏,为临床治疗类风湿关节炎提供实验依据。     

VEGF与endoglin在CIA大鼠滑膜组织中表达增高

目的探讨胶原性关节炎大鼠滑膜组织中血管内皮生长因子(VEGF)及endoglin在蛋白水平和分子水平(mRNA)的表达与意义。方法皮下给Wistar大鼠多点注射牛Ⅱ型胶原建立胶原诱导关节炎模型。观察关节肿胀和滑膜的病理学改变,用免疫组化法和RT-PCR技术检测VEGF与endoglin的蛋白及分子水平的表达。结果大部分鼠在胶原致敏后两周左右发病,主要表现为关节红肿,活动受限。VEGF与endoglin在CIA大鼠滑膜组织中表达增高(P<0.05),且两者在CIA滑膜中的蛋白表达和分子表达呈正相关(r=0.481,P<0.05)。结论 VEGF和en-doglin共同参与了类风湿性关节炎(RA)的病理过程,它们相互促进,相互影响,调控着RA的病理过程,它们是RA滑膜增生,浸润,关节破坏的关键因子。     

基质金属蛋白酶和胶原在创伤关节软骨组织中的表达

背景：研究发现,基质金属蛋白酶和胶原参与关节软骨组织机体生理重建及病理破坏。 目的：观察膝关节骨软骨缺损及表面软骨缺损动物模型关节软骨组织中胶原及基质金属蛋白酶的表达变化。 方法：雌性SD大鼠48只随机分为3组：骨软骨缺损组在双膝关节制作骨软骨缺损模型,表面缺损组在双膝关节制作表面软骨缺损,对照组双膝关节制作关节囊切开。分别于术后4、8、12周取股骨髁标本,行苏木精-伊红染色,免疫组化检测Ⅰ型胶原、Ⅱ型胶原、基质金属蛋白酶3的表达。 结果与结论：骨软骨缺损组术后4周缺损中有少量新生组织生成,8及12周可见到纤维组织填充,修复组织细胞外基质Ⅰ型胶原免疫组化染色阳性,Ⅱ型胶原免疫组化染色阴性,关节软骨组织中基质金属蛋白酶3表达增高。表面缺损组表面软骨缺损4及8周未见修复迹象,12周可见微量纤维组织填充,细胞外基质Ⅰ型胶原免疫组化染色阳性,Ⅱ型胶原免疫组化染色阴性,术后表面缺损组关节软骨组织基质金属蛋白酶3表达增高。对照组关节软骨组织Ⅰ型胶原免疫组化染色阴性,Ⅱ型胶原免疫组化染色阳性,基质金属蛋白酶3低表达,无形态学异常改变。说明机械性损伤可以导致关节软骨细胞外基质成分发生改变,丧失其原有的生物学特性而退变,基质金属蛋白酶3在损伤后的软骨组织中表达增高,使细胞外基质的降解增加,是导致关节软骨退变的重要因素。     

THH对胶原诱导型关节炎小鼠Th17细胞及细胞因子的影响

目的通过观察昆明山海棠(Tripterygium hypoglaucum hutch,THH)对胶原诱导型关节炎(collagen induced arthritis,CIA)小鼠Th17细胞及相关炎性细胞因子的影响,探讨THH治疗类风湿关节炎的相关免疫学机制。方法 30只健康雄性C57BL/6小鼠随机选取10只作为正常对照组,剩余20只用于制备CIA小鼠模型。将造模成功的小鼠随机分为CIA模型组、THH治疗组,每组9只。通过观测小鼠体质量、关节炎指数评分、关节肿胀程度及HE染色了解THH治疗情况,利用流式细胞术、实时荧光定量PCR(RT-qPCR)及ELISA观察THH对CIA小鼠Th17细胞及IL-17A的影响,并使用GraphPad软件对结果进行分析。结果CIA模型组小鼠体质量与THH治疗组间无统计学差异;关节炎指数评分及关节肿胀程度CIA模型组均高于THH治疗组;HE染色显示THH治疗组关节炎的炎症较模型组减轻,骨损伤减少。流式结果显示,脾脏Th17细胞比例CIA模型组低于正常对照组(P0.01),THH治疗组高于CIA模型组(P0.05)。CIA模型组踝关节及血清中IL-17A表达明显高于正常对照组(P0.01),THH治疗组中的表达量低于CIA模型组(P0.05)。结论 THH可通过升高CIA小鼠外周免疫器官Th17细胞比例、降低关节组织及血清IL-17A表达水平,从而减轻关节炎的炎症反应,减少关节骨损伤。     

核因子-κB诱骗剂局部应用对胶原诱导性关节炎大鼠治疗作用的研究

探讨核因子-κB诱骗剂(NF-κB decoy)局部应用对Ⅱ型胶原诱导关节炎(CIA)大鼠的治疗作用及其对滑膜基质金属蛋白酶-3(MMP-3)、IL-17、TGF-β表达的影响。建立Ⅱ型胶原诱导大鼠关节炎模型,用NF-κB诱骗剂注射到大鼠右后踝关节腔内,并设对照组、CIA模型组和实验组。42d后观察各组关节炎指数、病理指标,采用ELISA法检测各组大鼠关节液中IL-17、IL-12和TGF-β的水平,免疫组织化学方法检测关节组织MMP-3、TGF-β和IL-17表达。与对照组比较,CIA模型组大鼠关节炎指数、关节液中IL-17、IL-12水平均明显升高,滑膜组织MMP-3、IL-17阳性表达的积分光密度(IOD)值明显增加;实验组经NF-κB诱骗剂注射后,与CIA模型组比较,关节炎指数、关节液中IL-17、IL-12水平均明显降低,而TGF-β的含量显著增高,滑膜组织MMP-3、IL-17阳性表达的IOD值明显降低,TGF-β阳性表达的IOD值显著增高。NF-κB诱骗明显减轻CIA大鼠的关节炎症状,延缓关节破坏的进展,对CIA有较好的治疗作用。     

低氧诱导因子-1α在CIA模型中的表达及其意义

目的 探讨低氧诱导因子-1α(HIF-1α)在胶原诱导性关节炎(CIA)模型中的表达及其在类风湿性关节炎(RA)发病中的作用.方法 建立CIA模型,取CIA模型踝关节进行HE染色及HIF-1α免疫组化染色,观察HIF-1α在RA组织中表达的情况.结果 CIA大鼠关节滑膜层和滑膜下层均表达HIF-1α,第21天阳性表达量最高,随病程进展,表达逐渐下降,与滑膜病理学评分、滑膜增生评分及血管生成评分呈显著正相关,与炎症浸润评分无明显相关.结论 HIF-1α在RA组织中的表达与炎症严重程度呈正相关,HIF-1α与RA的发生发展有一定相关性.     

PC对CIA小鼠关节的保护作用研究

目的：研究蛋白C(PC)对胶原诱导的关节炎（CIA）的影响及其是否通过内皮细胞蛋白C受体（EPCR）通路发挥作用。方法：构建CIA小鼠模型，并随机分为CIA模型组和CIA+PC组。CIA+PC组预防性给予PC,CIA模型组不做任何处理。应用量化评分评估PC对足肿胀的缓解程度；Micro-CT、HE染色、甲苯胺蓝染色观察小鼠骨/软骨破坏情况；双重免疫荧光法检测EPCR在小鼠滑膜组织中的表达情况；应用siEPCR腺病毒载体干扰EPCR蛋白表达，观察其对PC作用的影响。结果：PC干预CIA小鼠后，小鼠的临床评分降低，足爪肿胀程度减轻，骨侵蚀缓解；在CIA小鼠和DBA1小鼠的关节滑膜组织中检测到EPCR表达，且CIA小鼠EPCR表达明显低于DBA1小鼠。PC+siEPCR腺病毒载体干预CIA小鼠后，CIA小鼠临床评分无明显降低，关节症状未得到有效缓解。结论：PC可改善CIA小鼠的关节症状，进而缓解CIA疾病进展。而siEPCR可逆转PC的这种保护作用，因此PC缓解CIA疾病进展依赖于EPCR蛋白表达。     

异种脐血干细胞移植胶原性关节炎小鼠Bcl-2和Bax的表达*☆

背景：类风湿性关节炎的发生发展与滑膜细胞及淋巴细胞的增殖与凋亡不平衡密切相关,其滑膜细胞存在细胞凋亡过程的异常。 目的：观察异种、异基因双份脐血干细胞移植对Ⅱ型胶原性关节炎小鼠Bcl-2和Bax表达的影响。 方法：弗氏完全佐剂+Ⅱ型胶原诱导C57BL/6(H-2b)小鼠,建立Ⅱ型胶原性关节炎小鼠模型。小鼠二次免疫接种后第2天,模型组、正常对照组尾静脉注射生理盐水,细胞移植组将脐血造血干细胞注入小鼠尾静脉内(其中单份剂量2×106/50 g;双份剂量：每份1×106/50 g,共2×106/50 g)。甲氨喋呤阳性对照组小鼠灌胃甲氨蝶呤,每次0.017 5 g/kg,每5天1次,共6次。 结果与结论：移植后第42天全部处死动物取膝及肘以下关节组织,病理组织学显示正常对照组关节面光滑,滑膜层未见炎性细胞浸润,软骨细胞形态正常;模型组滑膜组织高度增生,大量的炎性细胞浸润,软骨面破坏;甲氨蝶呤阳性对照组、单份脐血造血干细胞移植组滑膜组织可见轻度增生,少量炎性细胞浸润,双份脐血造血干细胞移植组关节软骨表面光滑,未见破坏,有极少量炎性细胞浸润。免疫组织化学检测显示,双份脐血造血干细胞移植组Bax、Bcl-2的表达低于单份脐血造血干细胞移植治疗组(P < 0.05);与正常对照组比较,差异无显著性意义(P > 0.05)。结果说明双份脐血干细胞在一定数量及作用时间内可诱导Ⅱ型胶原性关节炎小鼠滑膜细胞凋亡,对滑膜组织损伤起保护作用。     

痹祺胶囊对类风湿关节炎CIA大鼠JAK-STAT信号通路的影响

目的观察中成药痹祺胶囊对胶原诱导性(CIA)大鼠的JAK-STAT信号通路影响,并探讨其可能的作用机制。方法以牛Ⅱ型胶原和完全弗氏佐剂制备CIA大鼠模型,随机分为空白组、模型组、甲氨蝶呤组、痹祺胶囊高中低剂量组进行给药,每组12只大鼠。每周监测各组大鼠足趾容积和体质量变化。用药12周后,光镜下观察各组大鼠踝关节病理形态;Western blot检测大鼠软骨和滑膜中JAK3、STAT3蛋白表达水平;RT-PCR法测定软骨和滑膜中JAK3、STAT3的m RNA表达水平。结果模型组踝关节红肿明显,伴关节畸形、活动量减少及跛行,滑膜和软骨中JAK3及STAT3水平均明显升高(P0.05);各用药组足趾肿胀度较模型组显著减轻(P0.05),痹祺胶囊高剂量组较其它组减轻最明显(P0.05);模型组软骨和滑膜中JAK3、STAT3蛋白及m RNA表达水平明显升高,各用药组均明显降低(P0.05),痹祺胶囊高中剂量组优于MTX组(P0.05);光镜下观察模型组大鼠踝关节滑膜大量增生、血管翳生成和软骨明显破坏,各用药组可抑制滑膜增生和减轻软骨破坏,其中痹祺胶囊高剂量组作用最佳,与MTX组作用相当(P0.05)。结论痹祺胶囊能明显减轻CIA大鼠关节炎症、滑膜增生、血管翳形成及软骨破坏,其机制可能与调控JAK-STAT信号通路中JAK3、STAT3的表达相关。     

Matrix metalloproteinase 9 (gelatinase B) is expressed in multinucleated giant cells of human giant cell tumor of bone and is associated with vascular invasion.

Human giant cell tumor (GCT) consists of multinucleated giant cells and mononuclear stromal cells, and is characterized by frequent vascular invasion without distant metastases. To study the role of matrix metalloproteinases (MMPs) in the vascular invasion, we examined production of MMP-1 (tissue collagenase), -2 (gelatinase A), -3 (stromelysin-1), -9 (gelatinase B), and tissue inhibitors of metalloproteinases (TIMP-1 and -2) in GCT. MMP-9 was highly and predominantly expressed in giant cells by both immunohistochemistry and in situ hybridization. Expression of other MMPs was also observed in some cases but was inconstant. Sandwich enzyme immunoassays demonstrated that MMP-9 is the predominant MMP secreted by GCT. There was a definite imbalance between the amounts of MMP-9 and those of TIMPs in the culture media of GCT, leading to detectable gelatinolytic activity in an assay using 14C-gelatin. Gelatin zymography demonstrated the main activity at about 90 kd, which was identified as the zymogen of MMP-9 by immunoblotting. Immunohistochemistry for type IV collagen and laminin, major basement membrane components, showed that disappearance of the proteins is closely associated with MMP-9-positive giant cells. These results indicate the production of MMP-9 by multinucleated giant cells and suggest that the metalloproteinase may contribute to proteolysis associated with vascular invasion and local bone resorption in human GCT.     

Matrix metalloproteinases with gelatinolytic activity induced by Paracoccidioides brasiliensis infection

Matrix metalloproteinases (MMPs) modulate extracellular matrix turnover, inflammation and immunity. We studied MMP-9 and MMP-2 in experimental paracoccidioidomycosis. At 15 and 120 days after infection (DAI) with virulent Paracoccidioides brasiliensis , MMP-9 was positive by immunohistochemistry in multinucleated giant cells, in mononuclear cells with macrophage and lymphocyte morphologies and also in fungal cells in the lesions of susceptible and resistant mice. Using gelatin zymography, pro- and active MMP-9 and active MMP-2 were detected in all infected mice, but not in controls. Gelatinolytic activity was not observed in P. brasiliensis extracts. Semiquantitative analysis of gelatinolytic activities revealed weak or absent MMP-2 and strong MMP-9 activity in both mouse strains at 15 DAI, declining at 120 DAI. Avirulent P. brasiliensis -infected mice had residual lesions with MMP-9-positive pseudoxantomatous macrophages, but no gelatinase activity at 120 DAI. Our findings demonstrate the induction of MMPs, particularly MMP-9, in experimental paracoccidioidomycosis, suggesting a possible influence in the pattern of granulomas and in fungal dissemination.     

骨髓间充质干细胞下调类风湿性关节炎小鼠脾脏单个核细胞TLR8及TLR9的表达

背景：间充质干细胞能够缓解类风湿性关节炎小鼠的症状,但是其机制还不清楚。 目的：观察骨髓间充质干细胞对类风湿性关节炎小鼠脾脏单个核细胞表达TLR8及TLR9等的影响。 方法：DBA/1J小鼠随机分3组,非造模组不造模,阳性对照组和实验组制备Ⅱ型胶原诱导的小鼠类风湿性关节炎模型。实验组尾静脉注射移植大鼠骨髓间充质干细胞。 结果与结论：与阳性对照组比较,实验组小鼠关节直径明显减小,关节炎症细胞浸润程度明显降低,但比非造模组略高;小鼠脾脏单个核细胞表达TLR8、TLR9和白细胞介素1β的水平较阳性对照组明显降低(P < 0.01或P < 0.05);阳性对照组与实验组中TLR8与TLR9的表达均无明显相关性(P > 0.05)。说明骨髓间充质干细胞下调了类风湿关节炎小鼠脾脏单个核细胞表达TLR8及TLR9的水平,但TLR8与TLR9的表达无相关性。     

Deficiency of gelatinase B/MMP-9 aggravates lpr-induced lymphoproliferation and lupus-like systemic autoimmune disease

Gelatinase B/matrix metalloproteinase-9 (MMP-9) is a key enzyme involved in inflammatory, hematological, vascular and neoplastic diseases. In previous studies, we explored the intracellular substrate set or ‘degradome’ of MMP-9 and found many systemic autoantigens as novel intracellular gelatinase B substrates. Little is known, however, about the functional role of MMP-9 in the development of systemic autoimmunity in vivo. B6^lpr/lpr mice with defective Fas-mediated apoptosis were used to investigate the functions of MMP-9 in lymphocyte proliferation and in the development of systemic autoimmunity. Combined Fas and gelatinase B deficiency resulted in extreme lymphoproliferative disease with enhanced lymphadenopathy and splenomegaly, and significantly reduced survival compared with single Fas deficiency. At the cellular level, this was corroborated by increased lymph node accumulation of ‘double negative’ T cells, B cells and myeloid cells. In addition, higher autoantibody titers and more pronounced autoimmune tissue injury were found in the absence of MMP-9, culminating in chronically enhanced systemic lupus erythematosus (SLE)-like autoimmunity. After cleavage by MMP-9 the SLE autoantigens U1snRNP A and ribosomal protein P0 were hardly recognized by plasma samples of both B6^lpr/lpr.MMP-9^?/? and B6^lpr/lpr.MMP-9^+/+ mice, pointing to a destruction of B cell epitopes by MMP-9-mediated proteolysis. In addition, the same loss of immunodominant epitopes was observed with plasma samples from SLE patients, suggesting that MMP-9 suppresses systemic antibody-mediated autoimmunity by clearance of autoepitopes in immunogenic substrates. Thus, new protective functions for MMP-9 were revealed in the suppression of lymphoproliferation and dampening of systemic autoimmunity, cautioning against the long-term use of MMP inhibitors in autoimmune lymphoproliferative syndrome (ALPS) and SLE.     

Experimental metastasis is suppressed in MMP-9-deficient mice

Matrix metalloproteinases (MMPs) are thought to play a key role in tumor invasion and metastasis. The role of MMP-9 (gelatinase B) in tumor metastasis was examined in MMP-9-deficient mice produced by gene targeting using embryonic stem cells. MMP-9-deficient mice develop normally and are fertile. In these mice, the number of metastatic colonies of B16-BL6 melanoma cells or Lewis lung carcinoma cells that were implanted intravenously fell by 45% for B16-BL6 melanoma and 59% for Lewis lung carcinoma (p=0.03 and p=0.0043, respectively). Gelatin zymography showed that both tumor cell lines did not secrete MMP-9 by themselves but the host cells surrounding the tumor cells secrete MMP-9 in vivo. These results indicated that host-derived MMP-9 plays an important role in the process of tumor metastasis.     

Immunotherapy of experimental arthritis. Analysis of the articular cartilage of mice suppressed for collagen-induced arthritis by a T-cell hybridoma.

The present study elucidates the suppression of collagen-induced arthritis (CIA) by T-suppressor cells through the analysis of the joints and articular cartilage of mice suppressed for CIA by a T-cell hybridoma. T-cell hybridomas (T101N and T104B1) were derived from the somatic cell fusion of splenic and thymic cells of mice suppressed for CIA and the AKR BW 5147 thymoma cell line. CIA mice administered 1 X 10(5) T101N hybridoma cells intravenously were observed to have reduced hind paw pathology scores as well as reduced edema, compared with CIA mice or CIA mice administered 1 X 10(5) cells of a control T-cell hybridoma, T104B1. The hind paw articular cartilage of joints from mice with CIA administered T101N cells resembled normal joint architecture in histologic staining and alignment of articular cartilage surfaces. The histopathology observed in joints of mice administered T104B1 hybridoma cells resembled that of CIA mice with large pannus formation, fibrous bridging of the joint, soft-tissue metaplasia, and joint disorganization. The data indicate that specific T-cell hybridoma cell lines can modulate the joint histopathology observed in CIA to resemble the joint architecture of noninflammatory joints.     

麻杏石甘汤对哮喘模型小鼠气道重塑及肺组织MMP-9和TIMP-1表达的影响

目的:观察麻杏石甘汤对哮喘模型小鼠气道重塑及肺组织基质金属蛋白酶9(MMP-9)和金属蛋白酶组织抑制物1(TIMP-1)表达的影响,探讨其治疗哮喘的可能机制。方法:将72只健康雌性BALB/c小鼠随机分为:空白对照组,模型组,麻杏石甘汤低剂量组、中剂量组和高剂量组,阳性对照组。采用卵清蛋白致敏激发建立小鼠哮喘模型。空白对照组和模型组于激发前30 min以生理盐水灌胃;麻杏石甘汤低剂量组、中剂量组和高剂量组分别于激发前30 min以麻杏石甘汤按5.0 g/kg、10.0 g/kg和20.0 g/kg剂量灌胃;阳性对照组于激发前30 min以地塞米松按0.005 g/kg剂量灌胃。连续给药7 d后,观察气道反应性、支气管肺泡冲洗液(BALF)中嗜酸性粒细胞(EOS)计数、杯状细胞百分比和胶原沉积的变化;ELISA法检测MMP-9和TIMP-1水平;Western blot法检测MMP-9和TIMP-1的蛋白表达;RT-qPCR法分析检测MMP-9和TIMP-1的mRNA表达。结果:与空白对照组比较,模型组的气道反应性、杯状细胞百分比、胶原沉积、BALF中EOS计数及肺组织MMP-9和TIMP-1的mRNA和蛋白水平均显著升高(P 0.01);与模型组比较,麻杏石甘汤低剂量组、中剂量组和高剂量组及阳性对照组上述指标则明显降低(P 0.05或P 0.01)。结论:麻杏石甘汤可能通过降低MMP-9和TIMP-1的表达改善哮喘模型小鼠气道重塑状态。     

Pathomechanisms of cartilage destruction by mechanical injury

Mechanical injury is considered to be a major inductor of articular cartilage destruction and therefore a risk factor for the development of secondary osteoarthritis. Mechanical injury induces damage to the tissue matrix directly or mediated by chondrocytes via expression of matrix-degrading enzymes and reduction of biosynthetic activity. As a consequence the mechanical properties of cartilage change. Some of the pathomechanisms of mechanical injury have already been uncovered by the use of a broad range of in vitro-models. They demonstrate that mechanical injury induces tissue swelling and decrease in both the compressive and shear stiffness of articular cartilage, probably due to disruption of the collagen network. Injurious compression induces chondrocyte death by necrosis and apoptosis and the remaining cells decrease their biosynthetic activity. The tissue content of proteoglycans also decreases with time in injured cartilage, and the tissue loses its ability to respond to physiological levels of mechanical stimulation with an increase in biosynthesis. Immature cartilage seems to be more vulnerable to injurious compression than more mature tissue. The expression of several matrix-degrading enzymes like ADAM-TS5 and matrix-metalloproteinases (MMP-1, MMP-2, MMP-3, MMP-9, MMP-13) is increased after injury and may in part be regulated by an autocrine vascular endothelial growth factor (VEGF)-dependent signalling pathway. Apoptosis seems to be mediated by caspase activity and reactive oxygen species. For that reason activation of antioxidative defense mechanisms as well as the inhibition of angiogenetic factors and MMPs might be key regulators in the mechanically induced destruction of cartilage and might be suggested as potential therapeutic interventions. This review summarizes some of the most important data from in vitro injury studies dealing with the pathomechanisms of cartilage destruction.