Immunolocalization of water channel aquaporins in the nasal olfactory mucosa

Aquaporins (AQPs), membrane water channel proteins expressed in various tissues and organs, serve in the transfer of water and small solutes across the membrane. We raised antibodies to AQPs using isoform-specific synthetic peptides and surveyed their expression in the rat nasal olfactory and respiratory mucosae. AQP1, AQP3, AQP4, and AQP5 were detected by immunohistochemical and immunoblotting analyses. AQP1 was expressed in the endothelial cells of blood vessels and the surrounding connective tissue cells in the olfactory and respiratory mucosae. AQP1 may be involved in water transfer across the blood vessel wall. In the olfactory epithelium, no AQP was detected in the olfactory sensory cells. Instead, AQP3 was abundant in the olfactory epithelium, where it was localized in the supporting cells and basal cells. Expression of AQP3 was mostly restricted to the basal cells in the respiratory epithelium. In marked contrast, AQP4 was abundant in the respiratory epithelium, but its abundance was limited to the basal cells in the olfactory epithelium. In the Bowman's gland, AQP5 was localized in the apical membrane in the secretory acinar cells, whereas AQP3 and AQP4 were found in the basolateral membrane. Similar localization was seen in its duct cells. These results showed a distinct localization pattern for AQPs in the olfactory epithelium. AQP3 and AQP4 in the supporting cells and basal cells may play an important role in generating and maintaining the specific microenvironment around the olfactory sensory cells. AQP3, AQP4, and AQP5 in the Bowman's gland may serve in the secretion to generate the microenvironment at the apical surface of the olfactory dendrites for odorant reception.     

Vitrification of intact human articular cartilage

Articular cartilage injuries do not heal and large defects result in osteoarthritis with major personal and socioeconomic costs. Osteochondral transplantation is an effective treatment for large joint defects but its use is limited by the inability to store cartilage for long periods of time. Cryopreservation/vitrification is one method to enable banking of this tissue but decades of research have been unable to successfully preserve the tissue while maintaining cartilage on its bone base - a requirement for transplantation. To address this limitation, human knee articular cartilage from total knee arthroplasty patients and deceased donors was exposed to specified concentrations of 4 different cryoprotective agents for mathematically determined periods of time at lowering temperatures. After complete exposure, the cartilage was immersed in liquid nitrogen for up to 3 months. Cell viability was 75.4 ± 12.1% determined by membrane integrity stains and confirmed with a mitochondrial assay and pellet culture documented production of sulfated glycosaminoglycans and collagen II similar to controls. This report documents successful vitrification of intact human articular cartilage on its bone base making it possible to bank this tissue indefinitely.     

Comparative biomechanical analysis of human and caprine knee articular cartilage

BackgroundThe goat is one of the most commonly used preclinical models for focal defect repair and regeneration. While the biomechanics of the human knee has been studied extensively, less is known about the biomechanics of the caprine knee. Differences between human and caprine knees have not been quantified and their significance is largely unknown.MethodsWe conducted a biomechanical analysis of the differences in goat and human knees to assess the validity of these preclinical in vivo models.ResultsCT and MRI scans revealed several differences in articular geometry: the caprine tibial plateaux were more convex and the menisci were significantly thicker and covered a larger proportion of the tibial articular surface. Caprine cartilage thickness was consistently thinner, while elastic modulus on indentation testing was consistently stiffer than human cartilage measured at eight different articular locations. Contact area and pressure were measured with electronic pressure sensors under loads normalized by multiples of body weight and at knee flexion angles reported for walking. The highest peaks in contact pressure were measured in the patellofemoral joint in goat and human knees. Peak contact pressure measured at 2 times body weight at the goat tibiofemoral joint at 70° flexion was significantly higher than for any other condition at the human tibiofemoral joint.ConclusionThese differences in contact conditions might explain the lower quality of local repair reported for caprine femoral condylar defects relative to trochlear defects. Further comparative analysis, including biologic response, is necessary to determine the extent to which the goat knee reproduces clinical conditions.     

Normal human synovial fluid and articular cartilage contain similar intact proteoglycans.

This work, directed to characterization of proteoglycans present in normal human synovial fluid by Western blotting techniques, revealed an intimate relationship of these proteoglycans to those of articular cartilage. Analyses were performed on samples subjected to digestion with chondroitinase ABC, in the presence or absence of keratanase, yielding products containing core proteins with glycosaminoglycan side chain stubs. The proteoglycan core proteins contained epitopes reactive with monoclonal antibodies that distinguish between chondroitin sulfate-4 and chondroitin sulfate-6. Additionally, these products reacted with monoclonal antibody to keratan sulfate when keratanase was omitted from the digestion. The analysis of synovial fluid revealed that the proteoglycan core proteins expressed predominantly the chondroitin sulfate-6 epitope, with expression of the chondroitin sulfate-4 epitope demonstrable only in prepubertal individuals. There was coexpression of both chondroitin sulfate epitopes in all proteoglycan core proteins of prepubertal individuals. Coexpression of chondroitin sulfate and keratan sulfate epitopes occurred in all proteoglycan core proteins. Proteoglycan core proteins had M(r) similar to those obtained from articular cartilage. Hence, in individuals free of joint disease, most proteoglycans seem to be transferred from articular cartilage to the synovial fluid without major alteration in the apparent size of the proteoglycan core protein. Only a minor set of proteoglycan core proteins had no direct articular cartilage equivalent. As this set also contained keratan sulfate, it is likely to be of articular cartilage origin, but probably modified by proteolysis.     

红姜提取物保护早期膝骨关节炎模型大鼠的关节软骨

BACKGROUND: Studies have reported that the combined use of ginger extract to reduce the levels of serum pro-inflammatory cytokines, including interleukin-1β, interleukin-6, tumor necrosis factor-α, is related to the reduction of cartilage injury in knee osteoarthritis. OBJECTIVE: To observe the protective effect of red ginger extract on articular cartilage and the expression of serum interleukin-1β, interleukin-6, tumor necrosis factor-α and cartilage tissue type II collagen α1 mRNA in rats with early knee osteoarthritis, and to explore the protective effect of red ginger extract on articular cartilage of rats with early knee osteoarthritis and its possible mechanism. METHODS: Fifty SPF Sprague-Dawley rats were randomly divided into blank group, model group, low-dose red ginger, high-dose red ginger and positive control group (n=10 per group). Except for the blank group, the rats in the other four groups were used to prepare knee osteoarthritis models by intraarticular injection of 4% papain 0.2 mL+0.03 mol/L L-cysteine mixed solution. The rats in the blank and model groups were fed routinely, and the low-dose red ginger, high-dose red ginger and positive control groups were given 50 mg/kg red ginger extract aqueous solution, 100 mg/kg red ginger extract aqueous solution and 18 mg/kg celecoxib capsule aqueous solution respectively. All the interventions were conducted once a day, for 4 continuous weeks. Four weeks after treatment, the rats in each group were killed and the knee joints were stained with safranin O-fast green. The articular cartilage was scored by Mankin scoring. The expression levels of interleukin-1β, interleukin-6, tumor necrosis factor-α in serum and type II collagen α1 mRNA in cartilage were detected. The study protocol was approved by the Animal Ethics Committee of Guangzhou University of Chinese Medicine, with an approval No. 20190917002. RESULTS AND CONCLUSION: The pathological section of knee cartilage showed that there was cartilage matrix loss in the model and each treatment group, and the Mankin score of each treatment group was significantly higher than that of the blank group (P < 0.05) and lower than that of the model group (P < 0.05). There was no significant difference between the high-dose group and the positive control group (P > 0.05), but the scores of the two groups were lower than that of the low-dose group. The levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α were upregulated in the positive control group, high-dose red ginger group and low-dose red ginger group compared with the blank group and down-regulated compared with the model group (P < 0.05). Moreover, and the levels of these cytokines were ranked as follows: positive control group < high-dose red ginger group < low-dose red ginger group (P < 0.05). The level of type II collagen α1 mRNA in cartilage showed no significant difference between the blank group and the high-dose red ginger group and the positive control group (P > 0.05), whereas the expression of type II collagen α1 mRNA was significantly increased in the model group and low-dose red ginger group compared with the other three groups (P < 0.05). To conclude, red ginger extract may protect the articular cartilage of knee osteoarthritis by inhibiting interleukin-1β, interleukin-6, and tumor necrosis factor-α, thereby delaying the development of knee osteoarthritis. Compared with the low-dose group, high-dose red ginger extract has better anti-inflammatory effect. © 2021, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.     

膝关节软骨损伤的研究进展

本文通过系统回顾分析中老年患者膝关节软骨损伤的流行病学特点、病因及可能的发病机制,进而探讨软骨损伤后的危害性,归纳外科治疗膝关节软骨损伤术式的选择及存在的优缺点,以及软骨损伤最新研究进展情况。     

超声评价膝关节软骨退行性变与手术的对照研究

目的 探讨膝关节软骨不同时期退行性变(退变)的超声表现,并进一步分析超声的诊断价值.方法　对行关节镜手术的9个膝关节用超声术中经皮实时观察,对关节置换术的2个膝关节标本(置生理盐水中)进行离体观察.总结正常软骨及Ⅰ～Ⅳ期软骨退变的超声表现.以此为超声诊断标准,术前检查40例患者的41个膝关节,将超声诊断与关节镜结果及手术切除标本对照.结果 正常软骨表现为高-低-高"夹心饼断面"样回声带,Ⅰ期退变常无异常,Ⅱ期退变软骨表面毛糙,轻度变薄或局部隆起,Ⅲ期退变软骨局部变薄,Ⅳ期退变软骨层完全丧失.超声诊断膝关节软骨退变的敏感性、特异性、准确性分别为64.9%、92.0%、76.5%.结论 除Ⅰ期外,其余各期关节软骨退变在超声上均有一定特点.超声可作为诊断膝关节软骨退变的重要辅助手段.     

Some biochemical characteristics and water exchange in human articular cartilage in osteoarthrosis

Rearrangement of intra- and intermolecular bonds in collagen molecule, disaggregation of proteoglycans and their elimination from cartilage involved in osteoarthrosis are responsible for water accumulation and its increased mobility in cartilage.     

Positive and negative regulation of water channel aquaporins in human small intestine by cholera toxin

Analysis of osmotic water permeability of aquaporin (AQP) 1, AQP3 and AQP4, which are expressed in human small intestine, in the presence or absence of cholera toxin (CT) was performed using a Xenopus oocyte expression system. When treated with CT, water permeability of AQP4 was facilitated while that of AQP3 was suppressed. AQP1 did not show any significant change of water permeability when treated with CT. An adenylyl cyclase accelerator forskolin showed similar effects as CT did, suggesting that changes of the water permeability of AQP4 and AQP3 were due to an increase of intracellular cAMP concentration. A possibility that these AQPs are responsible molecules for causing acute secretory diarrhoea as in cholera is considered.     

Expression of matrix metalloproteinases in normal and damaged articular cartilage from human knee and ankle joints

The objectives of this study were the following: (a) describe the appearance of histopathologic changes observed in human articular cartilage from the knee and ankle joints of organ donors with no symptomatic joint disease; (b) compare by in situ hybridization mRNA expression of six matrix metalloproteinases (MMP) in these cartilages; (c) compare MMP mRNA expression with the histology of the cartilage; and (d) test whether the effect of interleukin-1beta (IL-1beta) on the MMP mRNA expression could be detected with in situ hybridization. Human articular cartilages from the knee (tibiofemoral) and ankle (talocrural) joints of 41 different donors (aged 18 to 84 years) were obtained through the Regional Organ Bank of Illinois. The microscopic appearance of the cartilages was graded on a histopathologic scale from 0 to 13 with the highest grade representing severely damaged cartilage. In situ hybridization was performed using oligonucleotide probes to three collagenases (MMP-1, MMP-8, MMP-13), gelatinase A (MMP-2), stromelysin (MMP-3), and matrix type-1 metalloproteinase (MMP-14). Cartilages from some donors were cultured with IL-1beta and then analyzed for MMP expression using in situ hybridization. The histopathology grades of the cartilages from the asymptomatic donors covered the entire scale even in the ankle. Based on their grades, the cartilages were described as either normal (grades 0 to 5) or damaged (grades 6 to 13). The cartilages contained message for all six MMP tested with no detectable differences in expression of MMP-1, -2, -13, and -14 between the normal and damaged cartilages. However the expression of MMP-3 and MMP-8 was elevated in the damaged cartilages. In normal knee cartilage, mRNA expression of MMP-3 and MMP-8 was low, whereas in normal ankle cartilage, MMP-8 expression was below the detection limit. MMP-3 and MMP-8 message was up-regulated in the damaged cartilage from both joints, or if the tissue was cultured in the presence of IL-1beta. From this study we conclude the following: (a) similar histopathologic changes occur in both knee and ankle cartilages; (b) MMP-1, -2, -13, and -14 are constitutively expressed in adult human cartilage; and (c) only up-regulation of mRNA expression of MMP-3 and MMP-8 could be detected with naturally occurring cartilage damage and IL-1beta induction.     

VEGF-A is associated with early degenerative changes in cartilage and subchondral bone

Paired cartilage and subchondral bone of subjects with no clinical history of joint disorders were analyzed to determine whether antioxidant enzymes, inflammatory cytokines and growth factors can be linked to a pre-osteoarthritis. Tissue explants were phenotyped according to Osteoarthritis Research Society International grading and micro-computed tomography, and also screened for the expression of several markers using quantitative polymerase chain reaction. The expression of these same genes was measured in SW1353 cells treated with hydrogen peroxide, to gain insight into the pathways involved with oxidative stress responses. Vascular endothelial growth factor A (VEGF-A) was up-regulated in the cartilage samples that showed early cartilage or bone degeneration. Oxidative stress in chondrocytes provoked up-regulation of interleukin-1β, interleukin-6, aggrecan, and SRY-box containing gene 9. Our results confirm the hitherto evidence of the deteriorating effects of the oxidative stress on cartilage and suggest the link between VEGF-A and pre-osteoarthritis.     

富血小板血浆干预膝关节骨性关节炎模型兔关节软骨和滑膜的改变

文题释义： 富血小板血浆(PRP)：1993年Hood等首先提出富血小板血浆概念,并发现富血小板血浆含有丰富的血小板,其数目比全血中数目高3倍以上。血小板中含有大量的生长因子,如血小板衍生生长因子、转化生长因子β、类胰岛素生长因子、表皮生长因子、血管内皮生长因子等。 Ⅱ型胶原纤维(COL Ⅱ)：胶原纤维是关节软骨基质的重要组成结构之一,其中含量最多的Ⅱ型胶原纤维是构成软骨的基本框架,具有维持关节软骨的形态结构和抗张力强度的功能。基质金属蛋白酶为Ⅱ型胶原纤维的特异性降解酶,其中基质金属蛋白酶13降解Ⅱ型胶原纤维的速度是基质金属蛋白酶1的10倍。 背景：研究显示富血小板血浆具有很强的促进软骨细胞修复和增生作用。 目的：探讨富血小板血浆在骨性关节炎中对软骨细胞修复及滑膜炎症抑制的疗效。 方法：新西兰大白兔40只,于兔耳中央动脉取血后采用Hokugo等的方法制备富血小板血浆,同时检测外周血及富血小板血浆的血小板、血小板衍生生长因子、转化生长因子β和血管内皮生长因子水平。采用前交叉韧带切断法来制作动物模型后随机将兔分为实验组和对照组,实验组双侧膝关节每周注射1次0.3 mL 富血小板血浆;对照组每周注射1次0.3 mL无菌生理盐水,共注射10周。注射后第2,4,6,8,10周对兔进行大体观察及膝关节组织学观察;检测关节软骨Ⅱ型胶原蛋白及基质金属蛋白酶13水平,并进行软骨组织Mankin评分。实验方案经重庆医科大学动物实验伦理委员会批准。 结果与结论：①富血小板血浆中血小板、血小板衍生生长因子、转化生长因子β和血管内皮生长因子水平分别是正常血中的5.5,4.8,7.7和6.2倍(均P < 0.05);②注射后第6周实验组Mankin评分小于对照组(P < 0.05);③实验组第4,6,8,10周时Ⅱ型胶原蛋白水平明显高于对照组(P < 0.05);实验组第2,4,6,8,10周时基质金属蛋白酶13水平明显小于对照组(P < 0.05);④结果表明,关节腔内注射富血小板血浆能通过缓解关节滑膜炎症及延缓甚至阻断软骨细胞的损伤来抑制骨性关节炎的进展。 ORCID: 0000-0001-6301-4790(邱皓) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Quantitative ultrasound imaging detects degenerative changes in articular cartilage surface and subchondral bone

Previous studies have suggested that quantitative ultrasound imaging could sensitively diagnose degeneration of the articular surface and changes in the subchondral bone during the development of osteoarthrosis (OA). We have recently introduced a new parameter, ultrasound roughness index (URI), for the quantification of cartilage surface roughness, and successfully tested it with normal and experimentally degraded articular surfaces. In this in vitro study, the applicability of URI was tested in bovine cartilage samples with spontaneously developed tissue degeneration. Simultaneously, we studied the sensitivity of quantitative ultrasound imaging to detect degenerative changes in the cartilage-bone interface. For reference, histological degenerative grade of the cartilage samples was determined. Mechanical reference measurements were also conducted. Cartilage surface roughness (URI) was significantly (p<0.05) higher in histologically degenerated samples with inferior mechanical properties. Ultrasound reflection at the cartilage-bone interface was also significantly (p<0.05) increased in degenerated samples. Furthermore, it was quantitatively confirmed that ultrasound attenuation in the overlying cartilage significantly affects the measured ultrasound reflection values from the cartilage-bone interface. To conclude, the combined ultrasound measurement of the cartilage surface roughness and ultrasound reflection at the cartilage-bone interface complement each other, and may together enable more sensitive and quantitative diagnosis of early OA or follow up after surgical cartilage repair.     

The surface contour of articular cartilage in an intact, loaded joint

The friction coefficients measured in diarthrodial joints are small. Theories of joint lubrication attribute this efficiency to entrapment or movement of synovial fluid, yet anatomical models of the surface are based on studies of isolated fragments of cartilage, not functional joints. To investigate the functional interrelationship of joint surfaces and synovial fluid, the ultrastructure of loaded joints was examined. Twenty-four New Zealand white rabbit knee joints were loaded either statically or moved ex vivo using simulated muscle forces and then plunge-frozen under load. After fixation in the frozen/loaded state by freeze-substitution fixation, the medial joint compartments were embedded in epoxy resin while still articulated. Bone was trimmed away from the articular surfaces, permitting the cartilage to be sectioned for light and electron microscopy. These joint surfaces were then compared with controls which were not loaded, not moved or had been disarticulated prior to embedding. Articular surfaces of loaded joints were smooth at magnifications from ×35 to ×7500, whereas the tibial surfaces of nonloaded joints were irregular. Small pools of joint fluid were observed at the meniscal edge and beneath the anterior horn of the meniscus. At magnifications of ×40000, the joint surfaces were separated by a uniform 100 nm space containing fluid. An amorphous, electron dense articular surface lamina was present but, when loaded, was thicker and flatter than previously reported. No surface pits or bumps were visible in embedded, loaded joints. This is the first ultrastructural study of intact loaded joints. The findings suggest that fluid film lubrication is present in diarthrodial joints, but the fluid sequestration postulated in several models is not apparent.     

Phosphorylation of proteoglycans in human articular cartilage.

A study of human articular cartilage indicated that componenet proteoglycans can be phosphorylated. Phosphorylation, also found in a specimen of human epiphysial cartilage, occurred when [gamma-32P]-ATP or 32Pi was included in the in vitro incubation medium. Treatment of the phosphorylated proteoglycans with chondroitinase and chondrosulfatases effectively removed the chondroitin sulfate without dephosphorylating the remaining molecule. Since phosphorylation could be effected in a totally chemically defined medium, it appears that the necessary enzyme systems for this reaction are contained entirely within chondrocytes.     

Thioredoxin gene expression in rat knee articular cartilage after full-thickness injury

To study the expression of the antioxidative protein thioredoxin (TRX) in intact and injured articular cartilage, we examined the presence of trx mRNA in rat knee joints by in situ hybridization. Our results showed that in the intact knee, most cells, including articular cartilage chondrocytes, expressed trx mRNA. We examined joints at 1, 7, 14, and 28 days after the infliction of full-thickness cartilage injuries on distal femoral condyles. At 1 day after injury, no significant changes were observed in the wound or in trx expression pattern. However, at 7 to 28 days after injury, the wound became filled with repair tissue. Also, trx expression was detected in differentiating mesenchymal cells in the deeper zones of the wound but not in fibroblast-like cells in the upper part of the repair tissue, toward the joint cavity. This lack of TRX expression in the fibroblast-like cells may underlie the susceptibility of the repair tissue fibrocartilage to oxidative stress.     

Influences of the depth-dependent material inhomogeneity of articular cartilage on the fluid pressurization in the human knee

The material properties of articular cartilage are depth-dependent, i.e. they differ in the superficial, middle and deep zones. The role of this depth-dependent material inhomogeneity in the poromechanical response of the knee joint has not been investigated with patient-specific joint modeling. In the present study, the depth-dependent and site-specific material properties were incorporated in an anatomically accurate knee model that consisted of the distal femur, femoral cartilage, menisci, tibial cartilage and proximal tibia. The collagen fibers, proteoglycan matrix and fluid in articular cartilage and menisci were considered as distinct constituents. The fluid pressurization in the knee was determined with finite element analysis. The results demonstrated the influences of the depth-dependent inhomogeneity on the fluid pressurization, compressive stress, first principal stress and strain along the tissue depth. The depth-dependent inhomogeneity enhanced the fluid support to loading in the superficial zone by raising the fluid pressure and lowering the compressive effective stress at the same time. The depth-dependence also reduced the tensile stress and strain at the cartilage–bone interface. The present 3D modeling revealed a complex fluid pressurization and 3D stresses that depended on the mechanical contact and relaxation time, which could not be predicted by existing 2D models from the literature. The greatest fluid pressure was observed in the medial condyle, regardless of the depth-dependent inhomogeneity. The results indicated the roles of the tissue inhomogeneity in reducing deep tissue fractures, protecting the superficial tissue from excessive compressive stress and improving the lubrication in the joint.     

Immunolocalization of lymphatic vessels in human fetal knee joint tissues

We immunolocalized lymphatic and vascular blood vessels in 12- and 14-week-old human fetal knee joint tissues using a polyclonal antibody to a lymphatic vascular endothelium specific hyaluronan receptor (LYVE-1) and a monoclonal antibody to podoplanin (mAb D2-40). A number of lymphatic vessels were identified in the stratified connective tissues surrounding the cartilaginous knee joint femoral and tibial rudiments. These tissues also contained small vascular vessels with entrapped red blood cells which were imaged using Nomarsky DIC microscopy. Neither vascular nor lymphatic vessels were present in the knee joint cartilaginous rudiments. The menisci in 12-week-old fetal knees were incompletely demarcated from the adjacent tibial and femoral cartilaginous rudiments which was consistent with the ongoing joint cavitation process at the femoral-tibial junction. At 14 weeks of age the menisci were independent structural entities; they contained a major central blood vessel containing red blood cells and numerous communicating vessels at the base of the menisci but no lymphatic vessels. In contrast to the 12-week-old menisci, the 14-week meniscal rudiments contained abundant CD-31 and CD-34 positive but no lymphatic vessels. Isolated 14-week-old meniscal cells also were stained with the CD-31 and CD 34 antibodies; CD-68 +ve cells, also abundant in the 14-week-old menisci, were detectable to a far lesser degree in the 12-week menisci and were totally absent from the femoral and tibial rudiments. The distribution of lymphatic vessels and tissue macrophages in the fetal joint tissues was consistent with their roles in the clearance of metabolic waste and extracellular matrix breakdown products arising from the rapidly remodelling knee joint tissues.     

Lectin-binding in normal and fibrillated articular cartilage of human patellae

Summary Fluorescein-isothiocyanate (FITC) labeled lectins were used to study the distribution of specific binding-sites in histological sections of normal and fibrillated articular cartilage of human patellae.It has been shown that normal articular cartilage reveals lectin binding-sites for Concanavalin A (Con A) and wheat germ agglutinin (WGA), but not for soybean agglutinin (SBA), peanut agglutinin (PNA) and Ulex europaeus agglutinin (UEA).In fibrillated cartilage the distribution pattern of Con A and WGA is completely changed. SBA, PNA and UEA show a distinct staining pattern in particular in the fibrillated areas of degenerated cartilage. Lectin-staining of the extracellular matrix and the chondrocytes in both normal and fibrillated cartilage did not show any correlation with material that was either PAS- or Alcian blue-positive. In comparison with the conventional PAS- and Alcian blue reaction lectin-staining proved to be superior.Visualization of intra- and extracellular glycoconjugate-changes in normal and fibrillated cartilage in areas with no PAS and/or Alcian blue staining indicates that all layers of the cartilage are involved in the pathological process.It is evident that lectins can demonstrate minute differences between normal and arthrotic cartilage and we therefore conclude that lectins are sensitive and specific tools for the study of degenerative joint diseases.