Changes in articular cartilage after meniscectomy

Hitherto, the meniscus has been regarded as a developmental remnant. However, when removed in part or in total, it alters the normal biomechanical, biochemical, and physiologic processes of the knee joint. Although the pathogenesis of osteoarthritis (OA) is unknown, accelerated rates of normal metabolism may result in failure of the articular cartilage to maintain its mechanical integrity as a result of meniscectomy. In addition, an inflammatory state within the joint cavity may result in degenerative changes, due to a perturbation of the homeostatic anabolic and catabolic processes maintaining the knee joint. Animal models reliably reproduce the focal and relatively slow degeneration seen in humans. OA degeneration after meniscectomy has been described histologically with fibrillation, swelling, fissures, cell proliferation, clustering, cell nesting, and even necrosis. Biochemical changes, however, include proteoglycan loss, proteoglycan disaggregation, and an increase in proteoglycan synthesis. In addition to increased hydration, the main structural fibers of articular cartilage, composed of Type II collagen, are exposed to increased biomechanical forces. The minor collagens, e.g., Type IX collagen, may play a role in stabilizing the proteoglycan-Type II interaction, thus providing mechanical integrity. It appears that meniscectomy produces much more than wear-and-tear arthritis.     

Early changes in material properties of rabbit articular cartilage after meniscectomy

We have correlated early material and biochemical changes in articular cartilage in a surgical model for cartilage degeneration. Medial meniscectomy was performed on the left knee of 17 adult, female New Zealand white rabbits. The equilibrium Young's modulus of cartilage was assessed by an indentation test in situ at defined sites on the medial and lateral tibial plateaus of the operated and control knees; the cartilage was then excised and analyzed biochemically. Focal changes were consistently observed in the medial surface of the operated knee. The equilibrium modulus and the glycosaminoglycan content fell rapidly, reaching a minimum by 2 weeks after surgery; the lateral tibial surface was essentially unaffected. Six months after surgery, the glycosaminoglycan content had returned to normal and the modulus to near normal. Independent measurements on cored plugs from the medial surface 2 weeks after surgery revealed a significant decrease in both the dynamic stiffness and the streaming potential in the operated knee compared with the control. The findings suggest that normal ambulatory loads in vivo will deform the affected medial cartilage much more than normal. It remains to be seen if altered mechanical stresses are solely responsible for initiating and sustaining matrix remodeling by the chondrocytes.     

Increased release of matrix components from articular cartilage in experimental canine osteoarthritis.

The release rates of specific components of the proteoglycan aggregates (G1 domain, the chondroitin sulfate and keratan sulfate containing portion of the protein core, and link protein) of the articular cartilage of mature beagles were studied at early stages of canine experimental osteoarthritis (OA), generated by transection of the anterior cruciate ligament. Analysis of cartilage explants and synovial fluids indicates that at early stages of experimental OA, there is increased release of the proteoglycan aggregates of the articular cartilage. This involves a release from the tissue of the components of the proteoglycan that are specifically involved with aggregation together with the glycosaminoglycans of the proteoglycan. These components were detected at elevated levels in the media of explants of cartilage from the operated joint, and in the synovial fluids of the operated joints.     

Simultaneous changes in the mechanical properties, quantitative collagen organization, and proteoglycan concentration of articular cartilage following canine meniscectomy.

The mechanical properties and microstructure of articular cartilage from the canine tibial plateau were studied 12 weeks after total medial meniscectomy. The organization of the birefringent collagen network was measured with quantitative polarized light microscopy to determine the thickness and the degree of organization of the superficial and deep zones. The zonal concentration of sulfated glycosaminoglycan was quantified with digital densitometry of safranin-O staining. Equilibrium compressive and shear properties, as well as dynamic shear properties, were measured at sites adjacent to those of microstructural analysis. The results evinced significant loss of cartilage function following meniscectomy, with decreases of 20-50% in the compressive and shear moduli. There was no evidence of alterations in the degree of collagen fibrillar organization, although a complete loss of the surface zone was seen in 60% of the samples that underwent meniscectomy. Meniscectomy resulted in a decreased concentration of sulfated glycosaminoglycan, and significant positive correlations were found between the equilibrium compressive modulus and the glycosaminoglycan content. Furthermore, the shear properties of cartilage correlated directly with collagen fibrillar organization measured at the superficial zone of corresponding sites. These findings demonstrate that meniscectomy leads to impaired mechanical function of articular cartilage, with significant evidence of quantitative correlations between cartilage microstructure and mechanics.     

Longitudinal characterization of synovial fluid biomarkers in the canine meniscectomy model of osteoarthritis.

Damage to the meniscus can lead to posttraumatic osteoarthritis. Early markers of joint injury and tissue disease may be useful in developing and administering clinical treatment. We investigated the effects of total medial meniscectomy on biomarkers measured serially in synovial lavage fluid each month for 3 months. Following meniscectomy in dogs, four biomarkers were evaluated: cartilage oligomeric matrix protein, keratan sulfate epitope (5D4), the 3B3(-) neoepitope of chondroitin-6-sulfate, and the 3B3(+) chondroitinase-generated epitope of chondroitin-6-sulfate. Meniscectomy led to statistically significant elevations of all four biomarkers, with levels peaking at 4 weeks. By 12 weeks, the level of the 5D4 epitope returned to the preoperative baseline level whereas that of cartilage oligomeric matrix protein, 3B3(-), and 3B3(+) remained above the baseline. Concentrations of these biomarkers in the knees not operated on did not change significantly from the baseline. The levels of cartilage oligomeric matrix protein and 3B3(-) relative to 3B3(+) remained constant in all knees. In contrast, the level of 5D4 relative to 3B3(+) declined over time in the knee operated on but remained constant in the knee not operated on. These results demonstrate a quantitative change in the molecular components of synovial fluid after meniscectomy, as well as a qualitative change evinced by an alteration in the relative proportions of these epitopes. Extensive analyses showed a strong correlation between serum levels of 3B3(-) from the femoral and cephalic veins; however, serum 3B3(-) was not correlated with synovial fluid 3B3(-). These findings support the hypothesis that the concentrations of select cartilage biomarkers in synovial fluid are altered following meniscectomy and are promising tools for objectively monitoring the induction of osteoarthritis in this model system.     

Synovial fluid biomarker levels predict articular cartilage damage following complete medial meniscectomy in the canine knee.

The purposes of this study were to document the histological changes present in the tibial plateaus 12 weeks after complete medial meniscectomy in dogs and to determine if synovial lavage fluid biomarker levels are predictive of the severity of joint damage. Twelve adult dogs underwent complete unilateral medial meniscectomy and synovial lavage fluid biomarker levels, including cartilage oligomeric matrix protein (COMP), keratan sulfate (5D4). 3B3(-), and 3B3(+), were measured serially at 4-week intervals. The dogs were euthanized 12 weeks after surgery and each medial and lateral tibial plateau from the meniscectomized and contralateral knees was graded histologically. Histological data were analyzed using principal components analysis, which resulted in 4 factors that explained 70% of the variation in the data. Factor 2 (weighted most heavily by subchondral bone thickness) and Factor 3 (representative of articular cartilage damage) were significantly affected by compartmental site (P < 0.01 for both). Both of these factors were highest in the medial tibial plateau of the meniscectomized knee, and Factor 3 was significantly higher in this site than in the medial tibial plateau of the contralateral knee (P < 0.01). Peak levels of all 4 synovial lavage fluid biomarkers occurred at 4 weeks post-meniscectomy and 4-week minus baseline levels of all biomarkers were significantly correlated with the Factor 3 scores. This study demonstrates that significant articular cartilage damage occurs relatively quickly following complete medial meniscectomy in dogs and establishes the content and criterion validity for these synovial fluid lavage biomarkers in canine meniscectomy as surrogate measures of articular cartilage damage.     

Changes in the antiangiogenic properties of articular cartilage in osteoarthritis

Avascularity is important for the unique biomechanical properties of articular cartilage, and normal cartilage actively repels vascular invasion. This study investigated whether the antiangiogenic properties changed in the presence of osteoarthritis (OA) by culturing explants of human articular cartilage on the chorioallantoic membrane (CAM) of chick embryos and investigating the incidence of vascular invasion and the effects of exogenous vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9). The results were compared with those of non-OA cartilage obtained after femoral neck fractures. Altogether, 72% of OA samples but only 5% of non-OA samples were invaded by the CAM, indicating that changes in the antiangiogenic properties represented a fundamental difference between control and OA cartilage. Exogenous VEGF or MMP-9 increased the frequency of invasion to 70%–100%. Invasion most frequently occurred into cartilage matrix from which proteoglycans had been lost, the latter being detectable by sirius red staining of cartilage collagen. VEGF was synthesized by chondrocytes in proportion to the severity of degradation and might exacerbate the loss of resistance to invasion. These results indicate that loss of resistance to vascular invasion distinguishes OA cartilage from normal articular cartilage, which may be important in the pathogenesis of OA.     

Modification of articular cartilage and subchondral bone pathology in an ovine meniscectomy model of osteoarthritis by avocado and soya unsaponifiables (ASU)

OBJECTIVE: To examine the effect of an oral preparation of avocado and soya unsaponifiables (ASU) on the development of joint pathology in an ovine model of osteoarthritis (OA), using computer-assisted histomorphometric methods. DESIGN: OA was induced in ovine knee joints by bilateral lateral meniscectomy (N=32). ASU (900 mg/weekday) was given orally to half the group (MenX+ASU), the remainder receiving placebo (MenX). Sixteen animals were used as non-operated controls (NOC). At 3 and 6 months post-meniscectomy, histological sections from the medial and lateral femoral condyles (MFC, LFC), tibial plateaux (MTP, LTP) and trochlear groove (TG) were prepared from all joints. Sections were scored using traditional histopathological scales, and computerized image analysis, measuring total cartilage area, uncalcified cartilage (UCC) and subchondral bone plate (SCP) thickness, and intensity of articular cartilage toluidine blue staining (mean greyscale intensity, black=255) as an index of proteoglycan (PG) content. RESULTS: Computerized image analysis showed significant histological differences not detectable by traditional scoring methods. ASU-treated animals at 6 months showed reduced loss of toluidine blue stain in the MTP (P=0.015) and LTP (P=0.001), and significantly greater staining in the TG than either placebo or NOC groups (P=0.011). UCC thickness increased after meniscectomy, but tended to be highest in ASU-treated animals, significantly so in the middle zone of the LFC (MenX+ASU: 1.03+/-0.21mm vs MenX: 0.79+/-0.14 mm, P=0.018; NOC: 0.77+/-0.17 mm). Lateral compartment SCP thickness increased post-meniscectomy but was increased significantly less in the inner zone of the LTP in ASU-treated sheep (MenX+ASU: 1.37+/-0. 23 mm vs MenX: 1.68+/-0.28 mm, P=0.033; NOC=1.22+/-0.33 mm). CONCLUSIONS: In this model ASU treatment following meniscectomy appeared to confer a subtle but statistically significant protective effect on articular cartilage. Although the drug failed to prevent focal cartilage lesions, characteristic of this model, histomorphometric analysis demonstrated greater PG content and UCC thickness in adjacent joint regions of ASU-treated animals. In addition, a statistically significant reduction of subchondral bone sclerosis was noted in the LTP region of the drug-treated group. An anabolic effect on chondrocytes, resulting in the stimulation of matrix production in regions distant to the insult, was also suggested by the data. These findings support other studies which have proposed that ASU may exhibit disease-modifying anti-OA activity.     

Simultaneous changes in bone mineral density and articular cartilage in a rabbit meniscectomy model of knee osteoarthrosis

OBJECTIVE: It was hypothesized that increased bone mineral density of the medial proximal tibia would precede or coincide with the development of more severe cartilage changes after meniscectomy. METHODS: In a rabbit knee model, mineral density of subchondral bone and changes of articular cartilage were monitored 13 to 40 weeks after medial meniscectomy or a sham operation. RESULTS: Both procedures resulted in a decrease of bone mineral density, especially of the medial proximal tibia, which persisted up to 40 weeks (P< 0.02-0.0007). Meniscectomy induced cartilage changes typical for osteoarthrosis (P< 0.009), which progressed over time on the posterior aspect of the medial tibial plateau (P< 0.009), which is physiologically covered by the meniscus, but the procedure also induced iatrogenic changes which were located mainly on the anterior aspect of the concerned compartment, and which did not progress or develop to osteoarthrosis. CONCLUSIONS: The data suggest that the cartilage changes after meniscectomy in this animal model are caused by the surgical trauma, subsequent limb misuse, and altered load distribution, and initially associated by a decrease not an increase in bone mineral density of the proximal tibia. Moreover, the cartilage changes progressed without a simultaneous increase of the bone mineral density at corresponding sites.     

Intra‐articular delivery of glucosamine for treatment of experimental osteoarthritis created by a medial meniscectomy in a rat model

Glucosamine (GlcN) is a naturally occurring amino‐monosaccharide with putative chondroprotective activity. Optimum responses to GlcN are achieved at concentrations which are impractical with oral dosing. Intra‐articular delivery of a bolus dose of GlcN is one way to overcome these pharmacokinetic obstacles. In this study we report the effects of exposing primary human chondrocytes to a bolus dose of GlcN. We also locally administered GlcN in the context of a meniscal transection model of rat osteoarthritis (OA). The knees of male rats were subjected to medial meniscal transection and developed arthritic changes over 4 weeks. Treatment groups were then given thrice weekly 100 μL injections of 35 μg, 350 μg, 1.8 mg, or 3.5 mg of GlcN dissolved in normal saline. Gross images, modified Mankin scores, and histomorphometric measurements were used as outcome measures. The 350 μg dosage of GlcN had the most significant positive impact on all components of the modified Mankin score. Together, these findings suggest the local delivery of high concentrations of GlcN is well tolerated and can suppress experimental OA through influences on both bone and cartilage. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:302–309, 2014.     

Effect of hip hemiarthroplasty on articular cartilage and bone in a canine model

The purpose of this study was to determine if acetabular articular cartilage damage occurs in the presence or absence of changes in subchondral plate thickness or porosity and trabecular bone architecture after hip hemiarthroplasty. Eight canines were sacrificed 6 months after receiving unilateral hemiarthroplasties in which a cobalt chrome alloy femoral head was used. The acetabular cartilage, subchondral plate, and trabecular bone were quantitatively evaluated. Although the articular cartilage in the treated hip showed gross and histologic degenerative changes, there were no differences in the treated and contralateral hips in any of the trabecular bone parameters or subchondral plate thickness. However, the subchondral plate porosity was increased 2.6-fold in the treated hip. Therefore, degradation of cartilage can occur in the absence of thickening of the subchondral plate or alterations in the supporting trabecular bone architecture. These observations provide a better understanding of the role that periarticular bone has in the degenerative process after hemiarthoplasty.     

Biomechanical, histological and immunohistological studies of patellar cartilage in an ovine model of osteoarthritis induced by lateral meniscectomy.

OBJECTIVE: To evaluate the biomechanical, histological and immunohistochemical changes induced in patellar articular cartilage (AC) in ovine stifle joints 3 months after bilateral lateral meniscectomy, a procedure known to induce experimental osteoarthritis (OA) in the femoro-tibial joint (FTJ). METHODOLOGY: Fifteen mature adult Merino female sheep were used in this study. Ten were subjected to bilateral-lateral meniscectomy, while the remaining five were used as 'non-operated controls' (NOC). All animals were killed 3 months post-surgery. Topographical biomechanical indentation tests were performed on each patellae using a UMIS-2000 micro-indentation system. Initial load, relaxed and unload shear moduli were determined using an elastic analytical model, while the permeability was assessed by comparing the indentation response to a simulated indentation test conducted using a poroelastic finite element model. Immunohistochemical, normal and polarized histological studies were performed on each specimen after biomechanical testing. RESULTS: Patellar AC from meniscectomized joints exhibited an overall decrease in initial (-34%), relaxed (-32%) and unload shear modulus (-22%), and an increase in the permeability (+72%) relative to NOC cartilage (P< 0.01). The most significant differences in mechanical properties occurred on the lateral and central aspects of the patellae. There were no significant histological difference in staining between sections from NOC and meniscectomized joint AC using Toluidine Blue, a dye which binds to proteoglycans. However immunohistochemical staining with monoclonal antibody MAb 3B3(-), a putative marker of early OA change in PGs, demonstrated increased binding in the lateral and central regions of patellar sections from meniscectomized joints relative to the same regions of NOC AC. Moreover polarized light microscopy of Picro Sirius red stained sections revealed a significant decrease in birefringence intensity in the superficial-middle zones of the lateral and central regions of the patellar cartilage derived from the meniscectomized joints. CONCLUSION: This study has demonstrated that lateral meniscectomy is a procedure which was known to induce classical OA like changes in AC and subchondral bone of the FTJ also produced an early pathological response in the patellar AC.     

Mechanical and biochemical changes in the superficial zone of articular cartilage in canine experimental osteoarthritis

The changes in the tensile mechanical properties and biochemical composition of the superficial zone of articular cartilage were examined in a canine model of early osteoarthritis generated by transection of the anterior cruciate ligament. Sixteen weeks following ligament transection, the tensile stiffness of the articular cartilage was decreased by 44% and the ion-induced stress relaxation of the tissue was increased by 57% compared with the contralateral control. Biochemical analyses indicated that the water content of the experimental tissue was increased by 13%, which was reflected as an apparent 37% decrease in the proteoglycan content and a 36% decrease in the collagen content (expressed per wet weight). The hydroxypyridinium crosslink density was decreased in the experimental tissue by 11%. A significant negative correlation was found between the ion-induced stress relaxation and the hydroxypyridinium crosslink density in both control tissue (R = ?0.56) and experimental tissue (R = ?0.70). No correlation was noted between the tensile stiffness and the biochemical composition of the tissue. These results suggest that, in the superficial zone of articular cartilage, the structure of the tissue may play a more important role than the composition in the determination of its mechanical properties. A major event observed in the model of early osteoarthritis appears to be the disruption and remodeling of the collagen network in the superficial zone of the articular cartilage.     

Biomechanical, histologic and macroscopic assessment of articular cartilage in a sheep model of osteoarthritis

OBJECTIVES: Our primary objective was to explore the full potential of the ovine medial meniscectomy (MMx) model of early osteoarthritis (OA) for studies to validate non-destructive articular cartilage (AC) assessments and therapeutic interventions. Our secondary objective was to re-evaluate the relationships between the different types of AC assessment after MMx in sheep. METHODS: Macroscopic assessments, dynamic shear modulus (G*), phase lag and AC thickness measurements were performed at a total of 5437 reference points on all six articular surfaces in four normal joints and 16 MMx ovine stifle (knee) joints. Comparisons with histologic assessments of gross structural damage, collagen organisation (birefringence) and proteoglycan content were possible at 702 of these points. RESULTS: Histologic gross structural damage and proteoglycan loss were seen throughout the joint with greatest severity (fibrillation) in closest proximity to the MMx site. Increases in AC (30-50%) thickness, reductions in G* (30-40%) and collagen birefringence intensity (15-30%) occurred more evenly throughout the joint. Macroscopic softening was evident only when G* declined by 80%. G* correlated with AC thickness (rho=-0.47), collagen organisation rho=0.44), gross structural damage (rho=-0.44) and proteoglycan content (rho=0.42). Multivariate analysis showed that collagen organisation contributed twice as much to dynamic shear modulus (t=6.66 as proteoglycan content (t=3.21). Collagen organisation (rho=0.11) and proteoglycan content (rho=0.09) correlated only weakly to phase lag. CONCLUSIONS: Macroscopic assessments were insensitive to AC softening suggesting that arthroscopic assessments of AC status might also perform poorly. Collagen integrity was more important for the maintenance of AC stiffness (G*) than proteoglycan content. The development of major AC softening and thickening throughout the joint following MMx suggested involvement of non-mechanical (e.g., protein and biochemical) chemical and cytokine mediated processes in addition to the disturbance in biomechanical loading. The ovine MMx model provides a setting in which the spectrum of AC changes associated with the initiation and progression of OA may be evaluated.     

Systemic administration of glycosaminoglycan polysulphate (arteparon) provides partial protection of articular cartilage from damage produced by meniscectomy in the canine

Bilateral medial meniscectomy was undertaken in 14 mature beagles. Another two underwent arthrotomy (sham-operated controls). One week after surgery, six of the meniscectomised animals were administered glycosaminoglycan polysulphate (Arteparon) (2 mg/kg) subcutaneously three times a week for 3 weeks, then twice weekly until killed 23 weeks later. Two months before death all animals were given Na2(35)SO4 (1.0 mCi/kg) intravenously. At autopsy, articular cartilage (AC) from the medial and lateral compartments, as well as from the femoral trochlear groove and femoral head, was sampled. Proteoglycans (PGs) were isolated by 4.0 M Guanidine hydrochloride (GuHCl) extraction of AC and purified by ultracentrifugation. The PG monomers were assayed for hexuronic acid, protein, and hexosamines (galactosamine/glucosamine), and their ability to aggregate. The results indicated that Arteparon provided some protective effect to AC in the meniscectomised compartment as demonstrated histologically by reduced surface fibrillation, diminished chondrocyte cloning, and maintenance of alcianophilia. The levels of PGs and hexuronate-protein ratios in medial AC of drug-treated meniscectomised animals were found to be comparable to sham controls, whereas these parameters in the nondrug-treated meniscectomized group were depressed.     

Chondropathy after meniscal tear or partial meniscectomy in a canine model.

A primary goal in considering treatment for meniscal injuries is the preservation of the health of the articular cartilage. However, the chondroprotective effects of various techniques for meniscal injury treatments are unknown. We used a canine model to quantify articular cartilage degeneration in the medial compartment of the canine knee, resulting from a surgically created tear or a partial meniscectomy (PM) of the posterior region of the medial meniscus (each group, n = 10). After sacrifice at 12 weeks, the development of gross chondropathy and the changes in cartilage tensile stiffness were quantified, and correlations between these measurements were examined. Both treatment surgical treatment groups caused significantly greater gross chondropathy as compared to the unoperated contralateral controls. Cartilage tensile stiffness was significantly lower than unoperated controls by nearly 28% in both experimental groups. However, there were no significant differences observed between the gross chondropathy or the cartilage mechanical property changes between the experimental groups. Importantly, the severity of gross chondropathy was found to significantly correlate with the decrement in tensile stiffness properties of the articular cartilage. These findings indicate that significant degeneration of canine articular cartilage develops to a similar degree in the presence of a partially healed meniscus tear or a PM of the knee.