Immobilization-Induced Cartilage Degeneration Mediated Through Expression of Hypoxia-Inducible Factor-1α, Vascular Endothelial Growth Factor,and Chondromodulin-I

Immobilization results in thinning of the articular cartilage and cartilage degeneration, although the exact mechanisms are not clear yet. Hypoxia is thought to contribute to the degeneration of articular cartilage. We investigated the roles of hypoxia inducible factor (HIF)-1α, vascular endothelial growth factor (VEGF), and the newly cloned antiangiogenic factor, chondromodulin-I (ChM-1), in cartilage degeneration in immobilized joints. Male Wistar rats (n = 30, 12-week-old) were divided randomly into the control group (n = 10), immobilization group (n = 10), and continuous passive motion (CPM) group (n = 10). In the immobilization group, the ankle joints were fixed in full plantar flexion with plaster casts for 4 weeks. In the CPM group, the ankle casts were removed during the immobilization period and the ankle joints were subjected to CPM. Significant thinning of the articular cartilage was noted in the immobilization group but not in the control or CPM group. In the immobilized group, vascular channels were found in the area between the calcified cartilage zone and the subchondral bone. The densities of HIF-1α—and VEGF-immunostained cells were higher in the immobilized group than the other two groups. In contrast, low expression of ChM-1 was detected in the articular cartilage of the immobilized group compared with the control and CPM group. Our results showed that immobilization induces thinning of the articular cartilage and appearance of vascular channel, in areas with balanced expression of HIF-1α/VEGF and ChM-1.     

医用臭氧对骨关节炎关节软骨作用的病理-磁共振成像实验研究

目的 通过病理-磁共振成像(MRI)对照研究,评价医用臭氧对骨关节炎动物模型的关节软骨的修复作用.方法 新西兰大白兔36只,分为正常对照组、模型对照组、10mg/L臭氧关节腔内注射组、30mg/L臭氧关节腔内注射组、10mg/L臭氧自血回输组、30mg/L臭氧自血回输组,每组6只兔.采用Ⅱ型胶原蛋白酶关节腔内注射法诱导骨关节炎模型,造模4周后进行臭氧干预.比较各组关节软骨的MRI表现,测量其关节软骨的平均厚度及信号强度,与病理学改变对照分析,并对MRI表现与Mankin评分进行直线相关及回归分析.结果 模型对照组、各臭氧干预组的膝关节软骨平均厚度及信号强度较正常对照组变薄和降低(均P<0.05).病理结果显示关节软骨表面粗糙,裂隙形成并基质失染,模型对照及臭氧干预各组的Mankin评分均高于正常对照组(均P<0.05),而模型组与各臭氧干预组间的关节软骨平均厚度、信号强度及Mankin评分差异均无统计学意义(均P>0.05).关节软骨平均厚度与信号强度呈正的直线相关(r=0.561,P=0.000);关节软骨平均厚度及信号强度与Mankin评分呈负的直线相关(r=-0.727、-0.590,均P=0.000);关节软骨平均厚度与Mankin评分存在线性回归关系(Y=18.582-0.035X,R~2=0.528).结论 关节软骨损伤的MRI表现与病理有较好的相关性,中低浓度的医用臭氧经关节腔内注射及自血回输对骨关节炎动物模型的关节软骨可能均无修复作用.     

Changes in the hyaline articular cartilage after air exposure.

The changes of hyaline articular cartilage from rabbits after air exposure were evaluated. The knee joints were exposed to air for periods of thirty minutes to two hours. The animals were killed periodically, at three days, one week and three weeks postoperatively. After sacrifice, the cartilage was removed and prepared for study by light microscopy and electron microscopy. Exposure to room air for thirty minutes produced chondrocyte necrosis in the upper third of the cartilage, and exposure for 60 minutes or longer produced chondrocyte necrosis of the entire thickness of articular cartilage at three days after arthrotomy. But, three weeks after arthrotomy, we could not find any chondrocyte necrosis in any rabbits at varying periods of air exposure. There was no significant change in proteoglycan content between the aired and control cartilage. Clinical Relevance: Exposing cartilage to air can cause transient and reversible cartilage damage. If these changes are not reversible, the orthopedic surgeon should consider avoiding the prolonged exposure of articular cartilage to air, since complete matrix disintegration is known to occur months after chondrocyte necrosis.     

Experimental haemarthrosis in rhesus monkeys: morphometric, biochemical and metabolic analyses

The effects of a single episode of massive haemarthrosis in rhesus monkeys were studied. Autologous whole blood was injected into a femorotibial joint of 16 anaesthetized monkeys, equally divided into four groups and killed 7 days, 2, 3 and 6 months post-injection (PI). Synovial membrane and femoral articular cartilage were analysed morphometrically and articular cartilage was further analysed biochemically and metabolically. At 7 days PI, morphometric evaluation revealed a significant increase (P less than 0.05) in synovial membrane cellularity and synovial intimal thickness of injected joints versus control joints. This change was no longer evident 2 months PI. There was also an overall (n = 16) significant increase (P less than 0.05) in femoral articular cartilage cellularity in injected joints. The average chondrocyte lacuna area of injected joints was not statistically different from the control joints. Biochemical analyses of femoral articular cartilage revealed a significant decrease in hexosamine concentration (P less than 0.05) of injected joints. There was no significant difference between the injected and control joints in hydroxyproline or total protein concentration. Metabolic analyses revealed a significant increase (P less than 0.05) in cartilage collagenous protein production by injected joints compared with control joints. There were no significant differences in cartilage or secreted total protein production between injected and control joints. There were also no significant differences in cartilage or secreted proteoglycan production between joints. Morphometric evaluation of articular tissues following massive haemarthrosis has quantified a temporary hyperplastic reaction. A significant decrease in cartilage hexosamine concentration in haemarthrotic joints suggests this is a crucial biochemical event in the pathogenesis of blood-induced cartilage destruction.     

Effects of immobilization and remobilization on the ankle joint in Wistar rats

A sprained ankle is a common musculoskeletal sports injury and it is often treated by immobilization of the joint. Despite the beneficial effects of this therapeutic measure, the high prevalence of residual symptoms affects the quality of life, and remobilization of the joint can reverse this situation. The aim of this study was to analyze the effects of immobilization and remobilization on the ankle joint of Wistar rats. Eighteen male rats had their right hindlimb immobilized for 15 days, and were divided into the following groups: G1, immobilized; G2, remobilized freely for 14 days; and G3, remobilized by swimming and jumping in water for 14 days, performed on alternate days, with progression of time and a series of exercises. The contralateral limb was the control. After the experimental period, the ankle joints were processed for microscopic analysis. Histomorphometry did not show any significant differences between the control and immobilized/remobilized groups and members, in terms of number of chondrocytes and thickness of the articular cartilage of the tibia and talus. Morphological analysis of animals from G1 showed significant degenerative lesions in the talus, such as exposure of the subchondral bone, flocculation, and cracks between the anterior and mid-regions of the articular cartilage and the synovial membrane. Remobilization by therapeutic exercise in water led to recovery in the articular cartilage and synovial membrane of the ankle joint when compared with free remobilization, and it was shown to be an effective therapeutic measure in the recovery of the ankle joint.     

二甲双胍通过AMPK信号通路对小鼠骨关节炎保护作用的研究

目的　研究二甲双胍对小鼠骨关节炎及软骨细胞分化的影响。 方法　切除小鼠右膝关节的内侧半月板和前交叉韧带造模骨关节炎,造模成功后,随机分为2组,实验组给予二甲双胍(2mg/kg/d)而对照组予等量的生理盐水灌胃干预治疗8周,通过HE、番红O-快速绿切片染色和Micro-CT观察关节结构变化,进行Mankin评分评估关节炎严重程度,通过Western Blot检测各组关节软骨AMPK、mTOR的活性及自噬程度;取新生小鼠肋软骨和膝关节软骨进行细胞培养,随机分为实验组（2mmol/L的二甲双胍）和空白对照组,观察软骨细胞形态、数量,MTT法检测细胞活性, Western Blot检测软骨细胞AMPK、mTOR的活性及自噬程度。 结果　（1）成功构建了小鼠骨关节炎模型, HE、番红O-快速绿染色、Micro-CT结果及Mankin评分证明二甲双胍能保护骨关节炎;（2）关节软骨Western Blot结果显示二甲双胍能激活AMPK,增强自噬保护骨关节炎;（3）MTT法显示二甲双胍抑制软骨细胞增殖分化,Western Blot结果显示二甲双胍促进软骨细胞自噬。 结论　二甲双胍通过激活AMPK信号通路,抑制mTOR信号通路,促进软骨细胞自噬,发挥保护骨关节炎作用。     

少阳主骨方对食蟹猴自然退变膝关节骨性关节炎模型p16/Rb信号通路的影响

目的　根据中医“少阳主骨”理论,研究少阳主骨方延缓关节软骨细胞衰老和退变的作用机制。 方法　通过X线选取13只膝关节退变的老年食蟹猴作为动物模型,随机选取1只进行病理学观察,其余食蟹猴随机分为少阳主骨方组、氨糖美辛组、生理盐水组,每组4只,连续灌胃8周后处死所有食蟹猴,对关节软骨进行病理学观察,RT-qPCR、Western-blot检测关节软骨中p16、Rb基因与蛋白的表达。 结果　老年食蟹猴KOA模型关节软骨病理改变符合KOA病理变化特点,三组食蟹猴Mankin评分少阳主骨方组(7.5±0.53)分、氨糖美辛组(7.75±0.71)分、生理盐水组(8.25±0.46)分,少阳主骨方组与生理盐水组间具有统计学差异（P<0.05）;p16基因与蛋白的表达少阳主骨方组<氨糖美辛组<生理盐水组,具有统计学差异（P<0.05）;Rb基因与蛋白的表达少阳主骨方组>氨糖美辛组>生理盐水组,具有统计学差异（P<0.05）。 结论　少阳主骨方可以通过p16/Rb途径延缓关节软骨细胞衰老,从而延缓关节软骨退变。     

Influence of antigen-induced arthritis on connective tissue cell metabolism

Loss of hyaline articular cartilage during chronic joint inflammation may be due to enzymatic breakdown of cartilage proteoglycans and inhibition of proteoglycan biosynthesis. In vivo study in the mouse on the influence of antigen-induced arthritis on articular cartilage chondrocyte function revealed that proteoglycan synthesis was severely inhibited during active joint inflammation. In addition, autoradiographs showed that inhibition of chondrocyte synthetic function and chondrocyte death at later stages of the arthritis were most pronounced in the central part of patellar hyaline articular cartilage without pannus tissue being present nearby.     

RhoA/ROCK信号通路在异常应力下关节软骨中的表达

背景：RhoA/ROCK信号通路在活体内关节软骨退变或者骨性关节炎的病理过程中是否发挥着作用,为此设计了该实验。 目的：探索RhoA/ROCK信号通路在软骨退变过程中的作用。 方法：采用家兔右膝关节伸直位制动模型,对制动2,4,6 周及对照组家兔的右膝关节胫骨平台负重面全层软骨进行苏木精-伊红染色、番红O染色及RhoA、ROCK免疫组织化学染色,比较制动前后软骨组织学、病理积分及RhoA、ROCK表达变化情况。 结果与结论：随着制动时间的延长,关节软骨退变程度逐渐加重,Mankin评分逐渐增加,且各组评分之间差异有显著性意义(P < 0.05)。免疫组织化学提示RhoA、ROCK表达变化主要集中在切线层及中间层软骨,且二者在关节软骨退变过程中表达变化趋势一致,均为先增多后减少。结果表明,在关节软骨退变过程中,RhoA/ROCK信号通路表达先递增后逐渐降低,RhoA/ROCK信号通路在异常应力所致的关节软骨退变过程中发挥了效应。     

Thermoreversible hydrogel scaffolds for articular cartilage engineering

Articular cartilage has limited potential for repair. Current clinical treatments for articular cartilage damage often result in fibrocartilage and are associated with joint pain and stiffness. To address these concerns, researchers have turned to the engineering of cartilage grafts. Tissue engineering, an emerging field for the functional restoration of articular cartilage and other tissues, is based on the utilization of morphogens, scaffolds, and responding progenitor/stem cells. Because articular cartilage is a water-laden tissue and contains within its matrix hydrophilic proteoglycans, an engineered cartilage graft may be based on synthetic hydrogels to mimic these properties. To this end, we have developed a polymer system based on the hydrophilic copolymer poly(propylene fumarate-co-ethylene glycol) [P(PF-co-EG)]. Solutions of this polymer are liquid below 25 degrees C and gel above 35 degrees C, allowing an aqueous solution containing cells at room temperature to form a hydrogel with encapsulated cells at physiological body temperature. The objective of this work was to determine the effects of the hydrogel components on the phenotype of encapsulated chondrocytes. Bovine articular chondrocytes were used as an experimental model. Results demonstrated that the components required for hydrogel fabrication did not significantly reduce the proteoglycan synthesis of chondrocytes, a phenotypic marker of chondrocyte function. In addition, chondrocyte viability, proteoglycan synthesis, and type II collagen synthesis within P(PF-co-EG) hydrogels were investigated. The addition of bone morphogenetic protein-7 increased chondrocyte proliferation with the P(PF-co-EG) hydrogels, but did not increase proteoglycan synthesis by the chondrocytes. These results indicate that the temperature-responsive P(PF-co-EG) hydrogels are suitable for chondrocyte delivery for articular cartilage repair.     

A Collagen–Poly(Vinyl Alcohol) Nanofiber Scaffold for Cartilage Repair

Articular cartilage has a limited capacity for self-repair. Untreated injuries of cartilage may lead to osteoarthritis. This problem demands new effective methods to reconstruct articular cartilage. Mesenchymal stem cells (MSCs) have the proclivity to differentiate along multiple lineages giving rise to new bone, cartilage, muscle, or fat. This study was an animal model for autologous effects of transplantation of MSCs with a collagen–poly(vinyl alcohol) (PVA) scaffold into full-thickness osteochondral defects of the stifle joint in the rabbit as an animal model. A group of 10 rabbits had a defect created experimentally in the full thickness of articular cartilage penetrated into the subchondral space in the both stifle joints. The defect in the right stifle was filled with MSCs/collagen–PVA scaffold (group I), and in the left stifle, the defect was left without any treatment as the control group (group II). Specimens were harvested at 12 weeks after implantation, examined histologically for morphologic features, and stained immunohistochemically for type-II collagen. Histology observation showed that the MSCs/collagen–PVA repair group had better chondrocyte morphology, continuous subchondral bone, and much thicker newly formed cartilage compared with the control group at 12 weeks post operation. There was a significant difference in histological grading score between these two groups. The present study suggested that the hybrid collagen–PVA scaffold might serve as a new way to keep the differentiation of MSCs for enhancing cartilage repair.     

Protective effects of tumor necrosis factor-α blockade by adalimumab on articular cartilage and subchondral bone in a rat model of osteoarthritis

We aimed to investigate the effects of an anti-tumor necrosis factor-α antibody (ATNF) on cartilage and subchondral bone in a rat model of osteoarthritis. Twenty-four rats were randomly divided into three groups: sham-operated group (n=8); anterior cruciate ligament transection (ACLT)+normal saline (NS) group (n=8); and ACLT+ATNF group (n=8). The rats in the ACLT+ATNF group received subcutaneous injections of ATNF (20 μg/kg) for 12 weeks, while those in the ACLT+NS group received NS at the same dose for 12 weeks. All rats were euthanized at 12 weeks after surgery and specimens from the affected knees were harvested. Hematoxylin and eosin staining, Masson''s trichrome staining, and Mankin score assessment were carried out to evaluate the cartilage status and cartilage matrix degradation. Matrix metalloproteinase (MMP)-13 immunohistochemistry was performed to assess the cartilage molecular metabolism. Bone histomorphometry was used to observe the subchondral trabecular microstructure. Compared with the rats in the ACLT+NS group, histological and Mankin score analyses showed that ATNF treatment reduced the severity of the cartilage lesions and led to a lower Mankin score. Immunohistochemical and histomorphometric analyses revealed that ATNF treatment reduced the ACLT-induced destruction of the subchondral trabecular microstructure, and decreased MMP-13 expression. ATNF treatment may delay degradation of the extracellular matrix via a decrease in MMP-13 expression. ATNF treatment probably protects articular cartilage by improving the structure of the subchondral bone and reducing the degradation of the cartilage matrix.     

Unilateral hindpaw amputation causes bilateral articular cartilage remodeling of the rat hip joint

The purpose of this paper was to describe the remodeling of adult coxofemoral articular cartilage (AC) in response to altered weight bearing. Twelve adult male Sprague-Dawley rats underwent unilateral hindpaw transection at the distal tibiofibular junction (AmpCont group); another group of eight rats served as normal controls (Norm group). Subpopulations of both groups were injected with 35SO4 24 hr before harvest. All femora were harvested after 8 weeks. Safranin O stained longitudinal sections were used to determine AC thickness, cellularity, and proteoglycan (PG) staining. Regional grain counting was performed on autoradiographs. Analysis of the data revealed that the AC of Norm hips in the region near the fovea capitis femoris was significantly thicker, had a lower cell density, a greater PG density, and a lower 35SO4 incorporation rate per chondrocyte than the AC of the Norm lateral edge region. The intact limbs of the AmpCont animals demonstrated a relative thinning of the AC near the fovea capitis femoris, compared with the edge region, and reduced 35SO4 incorporation rate in the lateral edge region, compared with normal values. The operated limb of the AmpCont animals displayed a relative increase of PG density in the edge region compared with the foveal region and a reduced 35SO4 incorporation rate in the lateral edge region, compared with normal values. We concluded that rat coxofemoral AC responds bilaterally to unilateral hindpaw amputation through appropriate morphologic remodeling.     

The histological features of Anteromedial Gonarthrosis — The comparison of two grading systems in a human phenotype of osteoarthritis

Anteromedial Gonarthrosis (AMG) displays a well recognised pattern of cartilage damage on the medial tibial plateau. Anteriorly there is a full thickness cartilage defect, with transition to a partial thickness defect, becoming full thickness cartilage in the posterior third of the tibial plateau. The retained posterior cartilage is macroscopically normal. This study characterises the histological changes of AMG and examines the usefulness of two histological assessment tools.Sixteen unicompartmental resection specimens of patients with primary AMG were assessed. Samples were stained with Haematoxylin and Eosin and Safranin-O stains and scored using the modified Mankin grade, and the OOCHAS assessment tool. Each specimen was assessed at five regions along the antero-posterior axis starting from the exposed bone to the region of macroscopically normal cartilage.From anterior to posterior the staining showed a consistent increase in structural integrity and cellularity of the cartilage, matched by a qualitative increase in GAG content. Mean modified Mankin and OOCHAS scores showed a progressive decrease in grade (p < 0.001). The OOCHAS grade had a good correlation with the modified Mankin grade (?? = 0.886) and there was good intra- and inter-observer variability with both assessment tools.We conclude that there is progressive decrease in histological score from anterior to posterior in AMG and that the macroscopically normal cartilage seen posteriorly is histologically normal. Both the modified Mankin and OOOCHAS assessment tools are useful in histological grading but we found the OOCHAS easier and quicker to use. We propose that AMG represents a spatial model of progressive cartilage damage.     

维药买朱尼对关节软骨前炎性因子的影响

背景：骨关节炎病理过程中,白细胞介素1β被认为是促进软骨基质降解和关节软骨破坏的最重要的细胞因之一。 目的：观察白细胞介素1β在关节软骨中的表达,并观察维药买朱尼对其的影响。 方法：将40只SD大鼠随机数字表法随机等分为模型对照组、维药买朱尼组、假手术组、正常对照组。模型对照组和维药买朱尼组采用改良Hulth造模法建立大鼠膝骨关节炎模型,假手术组仅显露膝关节,不切断韧带,不切除内侧半月板。维药买朱尼组建模第2周开始灌胃维药买朱尼10.31 mg/(kg•d),模型组及假手术组大鼠均灌服等量生理盐水,连续4周。 结果与结论：模型组软骨退变程度明显重于维药买朱尼组,模型组软骨大体评分及Mankin评分均明显高于维药买朱尼组(P < 0.05),模型组软骨细胞白细胞介素1β的表达强度亦明显高于维药买朱尼组(P < 0.05)。与正常对照组比较,假手术组软骨大体评分、Mankin评分及软骨细胞白细胞介素1β差异无显著性意义 (P > 0.05)。结果说明,维药买朱尼可以抑制关节软骨前炎性因子白细胞介素1β的表达。     

Morphometric quantitation of histopathologic changes in articular cartilage in an immunologically-induced rabbit model of rheumatoid arthritis

An immune arthropathy was induced in New Zealand white rabbits by intradermal sensitization with complete Freund's adjuvant containing Mycobacterium butyricum followed by intra-articular administration of the bacterial antigen. Half of the animals were treated with 1 mg/kg/day of prednisolone sodium phosphate for 8 weeks by gavage beginning with the day of intra-articular challenge, while the remaining rabbits received the drug vehicle alone. By morphometric analysis (matrix/chondrocyte lacunae area ratio), we observed a significant decrease in cellularity in the arthritic articular cartilages from the vehicle control group. By contrast, there was a significant increase in cellularity in the patella, femoral and tibial cartilages of the steroid-treated animals as compared with that observed in the contralateral control joint. This study suggests that image analysis provides a reliable means for evaluation of architectural changes in the articular cartilage and allows for meaningful quantitation of the chondroprotective effects of drugs like prednisolone.     

The effects of joint immobilization on articular cartilage of the knee in previously exercised rats

Studies have determined the effects of joint immobilization on the articular cartilage of sedentary animals, but we are not aware of any studies reporting the effects of joint immobilization in previously trained animals. The objective of the present study was to determine whether exercise could prevent degeneration of the articular cartilage that accompanies joint immobilization. We used light microscopy to study the thickness, cell density, nuclear size, and collagen density of articular cartilage of the femoral condyle of Wistar rats subjected to aerobic physical activity on an adapted treadmill five times per week. Four groups of Wistar rats were used: a control group (C), an immobilized group (I), an exercised group (E), and an exercised and then immobilized group (EI). The right knee joints from rats in groups I and EI were immobilized at 90 °C of flexion using a plastic cast for 8 weeks. Cartilage thickness decreased significantly in group I (mean, 120.14 ± 15.6 μm, P < 0.05), but not in group EI (mean, 174 ± 2.25), and increased significantly in group E (mean, 289.49 ± 9.15) compared with group C (mean, 239.20 ± 6.25). The same results were obtained for cell density, nuclear size, and collagen density (in all cases, P < 0.05). We concluded that exercise can prevent degenerative changes in femoral articular cartilage caused by immobilization of the knee joint.     

T-2 toxin induces degenerative articular changes in rodents: link to Kaschin-Beck disease

Osteoarthritis (OA) is a degenerative joint disease that is characterized by joint pain and a progressive loss of articular cartilage. Kaschin-Beck Disease is a form of endemic OA in China whose etiology is unclear, but epidemiological data indicate a possible link to trichothecenes mycotoxin exposure. In vitro, T-2 toxin, a trichothecenes mycotoxin, has been demonstrated to inhibit aggrecan synthesis and promote aggrecanase and pro-inflammatory cytokine production in cultured chondrocytes. To assess the effects of T-2 toxin on articular cartilage in vivo, Wistar rats were fed a diet containing T-2 toxin (100 ng/kg chow) for six and ten months. Following six months of T-2 toxin exposure, histopathological changes in femorotibial cartilage were characterized by chondrocyte degeneration/necrosis and loss, chondrocyte clones, and loss of proteoglycan staining of articular cartilage, sometimes involving the entire thickness of the cartilage in the tibial plateaus and femoral condyles. By ten months, in addition to these changes, there was evidence of cartilage fibration in some rats. In conclusion, T-2 toxin exposure in rats induced degenerative lesions in articular cartilage similar to spontaneous OA, lending support to an etiologic role of mycotoxins in Kaschin-Beck Disease. T-2 toxin-induced degenerative joint disease may be a useful model of metabolic polyarticular OA.     

软骨下骨量变化与软骨退变的相关性

背景：关节软骨与软骨下骨在骨关节炎病变进程中的相互作用机制目前尚未完全阐明。软骨下骨量改变在骨关节炎病理进程中亦发挥重要作用。 目的：分析2种手术方式及2种蛋白酶诱导建立兔膝关节骨关节炎动物模型的效果,以及软骨下骨量变化与关节软骨退变的相关性。 方法：32只新西兰大白兔随机分为4组：Hulth模型组、前交叉韧带切断模型组、Ⅱ型胶原蛋白酶组及木瓜蛋白酶组,每组8只,右膝关节造模,左膝关节作为自身对照。造模后0,4,8周行DXA扫描,8周行MRI扫描后处死实验动物,取双侧膝关节制作病理组织学切片,比较各组膝关节影像学表现、大体形态及病理变化,并采用Mankin评分进行定量分析。 结果与结论：造模后0,4,8周实验侧膝关节骨密度进行性降低,骨量降低程度Hulth模型组>前交叉韧带切断模型组>Ⅱ型胶原蛋白酶组>木瓜蛋白酶组。MRI显示实验侧股骨内外髁关节软骨厚度变薄,厚度Hulth模型组<前交叉韧带切断模型组<Ⅱ型胶原蛋白酶组<木瓜蛋白酶组。大体标本、组织切片观察及Mankin评分显示手术建模组骨关节炎程度较药物组重,Hulth模型组病变最重,木瓜蛋白酶组最轻。结果说明关节内手术及关节腔内注射蛋白酶均能建立骨关节炎动物模型;手术造模可复制出中晚期骨关节炎,药物诱导可产生骨关节炎早期改变。骨关节炎病变严重程度与软骨下骨骨密度呈负相关;关节软骨退变和软骨下骨改变相互关联,病变进行性发展。