Experimentally induced degenerative joint lesions following partial meniscectomy in the rabbit

Animal models for osteoarthritis: processes, problems and prospects

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The effects of the neodymium laser on meniscal repair in the avascular zone of the meniscus

Thirty mature New Zealand white rabbits were divided into four surgical groups, and a 3- to 4-mm incision was made in the inner avascular zone of the central third of the medial meniscus. In group I, the tear was not treated by lasering or suturing. In group II, the tear was sutured. Group III was given four different doses of the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation with no suturing. Group IV underwent meniscal suturing followed by the same four different laser irradiation doses. The animals were killed at 2, 4, and 6 weeks, with gross and histologic evaluation of the healing responses by group and time. The overall results showed no healing of this meniscal tear in the avascular zone. Suturing generally showed increased cellular infiltration. The varying doses of the Nd:YAG lasing demonstrated no gradient effect, and no "welding" of menisci was noted. The maximum cellular inflammatory response was noted in the sutured and lased menisci, reinforcing the importance of a stable meniscal environment for healing meniscal tears.

Site-specific cartilage changes in murine degenerative knee joint disease induced by iodoacetate and collagenase

Degenerative joint disease was induced in the knee joints of mice by intraarticular injection of two different stimuli: iodoacetate and highly purified collagenase. Proteoglycan synthesis was measured in vivo at different time points in four topographical areas of the knee joint (central and peripheral parts of the patella and central parts of the medial and lateral tibial plateaus) and was compared with histological observations of localized damage to the joint. In vitro incubation with iodoacetate had a direct effect on proteoglycan metabolism. Intra-articular injection of iodoacetate in vivo inhibited the proteoglycan synthesis in cartilage from the central part of the patella. In the peripheral part of the patella, inhibition on day 1 was followed by stimulation of synthesis on days 3-30. Proteoglycan synthesis also was inhibited in the central parts of the medial and lateral tibial plateaus. The areas with inhibited synthesis had loss of safranin O staining on histology. In vitro incubation with collagenase did not have a direct effect on the proteoglycan metabolism of intact cartilage; this led to the assumption that osteoarthritis after injection of collagenase is caused by ligamentous injury, which leads to an unstable joint. Injection of collagenase in vivo stimulated the proteoglycan synthesis in cartilage from the central and peripheral parts of the patella. In an early stage of the process, the cartilage from the tibial plateaus also was slightly stimulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related changes in glycosaminoglycan distribution in different anatomical sites on the surface of knee-joint articular cartilage in young rabbits

In spite of the fact that the various anatomical regions of a given articular cartilage surface are subjected to different degrees of stress, the present observations strongly suggest that there exists a topographical homogeneity in the distribution of glycosaminoglycans in the same articular cartilage. In contrast to this age-related changes in the proportion of the different types of glycosaminoglycan species in articular cartilage are remarkable. Non-sulphated chondroitin could only be detected in very young articular cartilage. Dermatan sulphate, which has already been detected in young adult rabbits, was followed by the appearance of keratan sulphate in older rabbits. Chondroitin 4-6-sulphates were detected in all articular cartilages studied, the proportion of the 6-sulphated variably increasing with age. The present report suggests that the distribution of glycosaminoglycans in articular cartilage varies with species and age, and the data can further vary, depending on the methods used. It is therefore concluded that generalizations against the results reported in the literature should be considered skeptically.

Animal models of early osteoarthritis: their use for the evaluation of potential chondroprotective agents

Medial meniscectomy was undertaken in adult merino sheep and after 16 weeks exercise each group was administered five weekly intra-articular injections of saline, pentosan polysulphate (PPS), hyaluronic acid (HA) or a combination of PPS + HA. Gait analysis and x-rays were undertaken before and after drug treatment. At sacrifice (26 weeks), joints were examined for gross pathological and histochemical changes. Only the PPS-treated group showed an improvement in gait, with low radiological and histology scores. The HA-treated group showed similar but less significant changes to these parameters.

A model for osteoarthritis of the temporomandibular joint

There is a need for a simple, reproducible animal model of advanced osteoarthritis of the temporomandibular joint (TMJ). In this study, gentle removal of the condylar articular layer in the sheep TMJ resulted in an eburnated condyle with peripheral osteophytes, thin or perforated discs, and temporal surface proliferation. This model can be used for both the study of osteoarthritis and the evaluation of therapeutic methods.

Quinolone arthropathy--acute toxicity to immature articular cartilage

A class effect of quinolone antibacterial agents observed during animal toxicity testing is a specific arthropathy (QAP). Despite the growing list of laboratory animals susceptible to QAP and reports of arthralgia in patients treated with quinolones, the potential for QAP development in humans remains unknown. This review discusses current concepts in the biology of articular cartilage and how these concepts elucidate QAP pathogenesis. Biomechanical forces within synovial joints and toxicokinetic properties of quinolones contribute to QAP induction. Since a limited number of mechanistic pathways exist for acute articular damage, QAP may serve as a research tool to probe the pathobiology of injury to articular cartilage.

Mechanical determinants of osteoarthrosis

The joint is an organ and functions as a mechanical bearing created of biological materials. In the joint, as in all connective tissues, there is a relationship between mechanical factors and tissue behavior. Therefore, it is not surprising that joint health and osteoarthrosis are reflections of both mechanical and biological factors. Osteoarthrosis is not a disease, but organ failure caused initially by mechanical factors. The biological changes follow. There is no habitual pathophysiological cascade. Osteoarthrosis is best thought of not as a common final pathway, but as a common end stage. The hypotheses that in osteoarthrosis substructural disorganization of the matrix proceeds chondrocytic enzyme production, that impulsive loading is an essential factor in the progressive cartilage destruction, and that tidemark advancement and horizontal cartilage splitting are the primary mechanisms in progressive cartilage loss are discussed.

Arthroscopic meniscal repair evaluated by second-look arthroscopy

Of 353 arthroscopic peripheral meniscal repairs performed using the "outside to inside" suturing technique with rasp preparation of the tear region, 74 repairs (50 medial and 24 lateral) were assessed by second-look arthroscopy and are the basis of this report. Results were graded as either healed, incompletely healed, or failed; these findings were correlated with clinical symptoms and associated ACL deficiency. Overall, asymptomatic healing occurred in 84%, with 65% healed and 19% incompletely healed. The failure rate was 16%. All failures were symptomatic while all healed and incompletely healed menisci were asymptomatic. Failure was associated with ACL deficiency in all cases. No failures occurred in either an ACL uninjured knee or an ACL reconstructed knee. Failure was also associated with tear location in the posterior horn of the medial meniscus. Eleven of 12 failures (92%) involved posterior medial meniscal tears with only 1 failure located posterolaterally. Visual evidence of healing required a 4 month time interval.

Proteoglycan alterations during developing experimental osteoarthritis in a novel hip joint model

Degenerative hip joint disease was induced in dogs by extra-articular surgery that created a condition that mimics hip dysplasia. Decreased acetabular coverage of the femoral head gave altered mechanical load, with ensuing cartilage degeneration. For comparison, degenerative knee joint disease was induced in other dogs by transection of the anterior cruciate ligament of the knee. The femoral head articular cartilage showed macroscopic signs of degeneration within a month. No macroscopical changes of synovitis were present. Chemical analysis of cartilage samples showed loss of proteoglycans. Guanidine hydrochloride extracts of the cartilage contained proteoglycan fragments that could be separated by equilibrium density gradient centrifugation in cesium chloride. The data indicate that proteoglycans are fragmented by proteolytic cleavage and lost from the cartilage. The proteoglycans remaining in the tissue are smaller and have lost the ability to aggregate with hyaluronic acid. Similarly, in experimental knee joint osteoarthritis, the proteoglycan content of the cartilage decreased. The structural changes of those proteoglycans remaining were of a different nature, with no changes in proteoglycan size or aggregation properties, possibly indicating that both degradation and repair took place in the knee articular cartilage and/or that fragments were rapidly lost from the tissue. This may follow from different surgical procedures, only the one used for the hip joint being extra-articular, or from the different anatomy and physiology of the hip joint and the knee joint.

Articular cartilage changes following meniscal lesions. Repair and meniscectomy studied in the rabbit knee

A well-defined, longitudinal lesion in the avascular part of the medial meniscus of the right knee was made in 30 rabbits. After 3 months, the lesion was repaired surgically in 12 rabbits, was untreated in 12 rabbits, and a meniscectomy was performed in 6 rabbits. The articular cartilage was studied macroscopically and microscopically at 3-month intervals. Cartilage changes 3 months after meniscectomy were more pronounced than after meniscal repair or than in untreated lesions. However, meniscal repair did not reverse the cartilage changes.

Passive role of articular chondrocytes in the pathogenesis of acute meniscectomy-induced cartilage degeneration

The importance of viable articular chondrocytes and enzymes or factors from surgically traumatized synovium in the pathogenesis of acute meniscectomy-induced cartilage degeneration was examined in guinea pigs (nine groups of five animals each). Iodoacetate injected intra-articularly was used to kill articular chondrocytes of guinea pigs prior to meniscectomy to determine if they were active participants in the acute lesion induction. Lesions of similar severity to those occurring in animals with viable chondrocytes at the time of surgery were observed, suggesting that the chondrocytes were not actively involved in the pathogenesis in this group. In an additional group of guinea pigs in which chondrocytes were killed by iodoacetate, the medial collateral ligament was transected to determine if acute degenerative changes could be induced in acellular cartilage exposed to a surgical manipulation that does not by itself induce lesions but does expose cartilage to enzymes/factors from traumatized synovium. Transecting the medial collateral ligament and entering the joint space without induction of instability via meniscectomy did not result in histologic evidence of cartilage damage. This suggests that synovial trauma and mild inflammation were insufficient to induce matrix degeneration in the absence of abnormal load bearing. In further support of this, guinea pigs subjected to unilateral sciatic neurectomy at the time of meniscectomy were protected against development of acute cartilage degeneration. Results of this study suggest that articular cartilage devoid of viable chondrocytes at the time of meniscectomy responds acutely in much the same way as intact cartilage subjected to this procedure.

Amelioration of lapine osteoarthritis by treatment with glycosaminoglycan-peptide association complex (Rumalon)

The chondroprotective potential of glycosaminoglycan-peptide association complex (GP-C) was examined in the medial meniscectomy model of lapine osteoarthritis (OA). Prophylactic treatment with increasing doses of intramuscular GP-C (0.05-0.5 ml/kg) caused a significant reduction in OA lesion area and histologic scores, and the effect on disease activity appeared to be dose related. The DNA and uronic acid contents of OA tissue were unaffected by prophylactic treatment with GP-C. However, levels of hydroxyproline in OA cartilage increased to near control levels with prophylactic treatment. Cartilage levels of active and total metalloproteinases that digest proteoglycans were elevated in rabbits with OA; prophylactic treatment with low-dose GP-C (0.05 ml/kg) produced a significant reduction in active, but not total, enzyme. Cartilage levels of tissue inhibitor of metalloproteinases in animals with OA were comparable with control levels, but rose with increasing doses of GP-C. We also investigated GP-C as a therapeutic treatment in animals that had already developed OA lesions. Carbon black retention and histologic score returned to near-normal after therapeutic treatment with GP-C. Uronic acid and hydroxyproline levels were decreased in OA cartilage. Therapeutic treatment with GP-C had no statistically significant effect on uronic acid levels, but was associated with increased hydroxyproline content in the cartilage. The changes in metalloproteinase and metalloproteinase inhibitor were similar to those found in the studies of prophylactic treatment. The findings in this animal model may help explain some of the beneficial effects of GP-C in human OA.

Mechanical overload of a single compartment induces early degenerative changes in the rabbit knee: a preliminary study

The purpose of this experiment was to determine whether mechanical overload of a single compartment of the knee in rabbits via proximal tibial osteotomy could produce early changes consistent with degenerative arthritis. Ten New Zealand white female rabbits were allocated into two groups. Group 1 (five animals) underwent a right 20 degrees valgus proximal tibial osteotomy to overload the lateral compartment of the knee. Group 2 (five animals) underwent a tibial osteotomy without malalignment (sham controls). The osteotomies were stabilized with a mini AO/ASIF plate and screws, allowing early mobilization. The left leg in each animal was left intact and served as a control. Animals were sacrificed after 3 months. Histological grading of the cartilage was performed according to Mankin et al. The mean histological gradings for the right minus the left knee were the same for the lateral and medial compartments in the 0 degrees sham osteotomy group. However, the mean histological grading of the "overloaded" lateral compartment was 2.4 times greater than the medial compartment in the 20 degrees valgus osteotomy group. These findings suggest that histological evidence of degenerative changes can be surgically induced in the rabbit knee by creating a biomechanical overload of one compartment.

Synovitis and osteoarthritic changes in canine articular cartilage after anterior cruciate ligament transection. Effect of surgical hemostasis

Anterior cruciate ligament transection (ACLT) in the dog produces changes in the articular cartilage of the unstable knee that are consistent with those of osteoarthritis (OA). To determine whether the degrees of severity of OA cartilage changes, of synovitis, and of synovial iron deposition were related to adequacy of hemostasis at the time of ACLT, a modified surgical technique was devised, whereby electrocautery was used to obtain meticulous control of bleeding when the ligament was severed and irrigation was used to remove intraarticular blood before closure of the joint. When no particular attention was given to hemostasis, 69% of the dogs showed synovitis in the OA knee 10 weeks after ACLT; when electrocautery and irrigation were used to maintain hemostasis, synovitis was present in only 24% of the OA knees 10 weeks after ACLT (P less than 0.01). Iron deposits were present in 75% of synovial samples obtained after routine ACLT, but in only 6% (P less than 0.001) when attention was given to hemostasis. Hypertrophy of articular cartilage, chondrocyte cloning, fibrillation, and changes in tangential zone chondrocytes were less prominent in the OA knee when electrocautery and irrigation were used. However, the water content, uronic acid concentration, and rate of net 35S-labeled glycosaminoglycan synthesis were similarly increased regardless of the surgical technique used, and presumably, these changes reflect the reaction of joint cartilage to mechanical instability in this model of OA.

Osteoarthritis research: animal models

Although limited in scope and detail, the current review has sought to highlight the contribution of animal models in the study of OA. Further use of these and other models should provide information that may lead to methods for the early detection and successful treatment of human OA.

The relevance of animal models in osteoarthritis

Studies of osteoarthritis (OA) in humans are restricted by the slow rate at which the disease progresses, and the limited opportunity for study of the tissue changes over time. A range of animal models of OA have been developed which demonstrate histopathological and gross features typical of OA in humans. Animal models can be used to study OA, and to investigate the effects of a variety of agents, including so-called chondroprotective agents, on the progression of the disease.

Effect of interleukin-1 on the size distribution of cartilage proteoglycans as determined by sedimentation field flow fractionation

The effect of interleukin-1 (IL-1) on the size distribution of cartilage proteoglycans was studied using sedimentation field flow fractionation (SdFFF), a rapid, high-resolution technique for the separation of proteoglycan monomers and aggregates. During incubation of cartilage in control media, 35S-prelabeled proteoglycan was lost primarily from proteoglycan present in the monomer form; aggregates were conserved. In the presence of IL-1, both 35S-proteoglycan monomers and aggregates were lost, suggesting that IL-1 increases the susceptibility of aggregates to loss from the cartilage matrix. Evaluation of uronic acid as a measure of net change in proteoglycan content indicated that IL-1 causes a net decrease in both monomers and aggregates. Kinetic studies suggested that aggregates are degraded to monomers which then diffuse out of the matrix. Incorporation of [35S]sulfate into cartilage proteoglycans following exposure to IL-1 showed that synthesis of monomers and aggregates is inhibited similarly. SdFFF is a valuable technique for studying proteoglycan metabolism. With its use, changes in proteoglycan monomer and aggregate populations can be detected in response to cytokines such as IL-1.

Serum keratan sulfate levels in rabbits with experimentally induced osteoarthritis

Serum keratan sulfate (KS) levels were measured with an enzyme-linked immunosorbent assay using monoclonal antibody (MAb) 5-D-4 (anti-KS) in a rabbit model of osteoarthritis (OA) induced by partial meniscectomy. The partial medial meniscectomy produced pathologic changes of OA in the joints of the rabbits, which were seen when the animals were killed at 3, 6, 9, or 12 weeks postsurgery. Tibial or femoral osteophytes were seen in up to 90% of the operated joints; pitting and ulceration of medial femoral condyles were also frequently noted (77% of cases). Rabbits that underwent sham surgery, back-skin-operated rabbits, or nonoperated normal rabbits served as controls; the joints of these animals were normal at the time of killing. A rise in the level of serum KS was recorded in 50% of rabbits following partial meniscectomy, but this was matched by similar changes in the control groups. The mean serum KS level of the OA animals at serial intervals (3, 6, 9, or 12 weeks) following surgery was not significantly different from that in the control groups. When measured with a second MAb, 2-D-3, KS levels showed similar trends as with MAb 5-D-4, although lower assay values were obtained. These findings indicate that experimentally induced OA in rabbits is not associated with a significant rise in serum KS levels. KS levels did not differentiate OA from non-OA animals, nor did they parallel disease progression.

Mechanics of the healed meniscus in a canine model

The mechanical behavior of the intact canine stifle joint was studied, using a surgical model of meniscal injury and repair. Thirty-eight animals were divided into five study groups: Group S received only a sham arthrotomy (without a meniscal incision), Groups P13 and P26 received peripheral medial meniscal incisions, and Groups R13 and R26 received radial medial meniscus incisions. All meniscal incisions were repaired anatomically with absorbable suture. Groups P13 and R13 were sacrificed at 13 weeks following surgery and Groups P26 and R26 at 26 weeks. Following sacrifice, the joints were subjected to gross and histologic examination, and structural and material properties testing. All meniscal repairs healed, and the peripheral repairs were virtually invisible, with no articular damage. The radial repairs healed with 3 to 5 mm wide fibrovascular scars, and several joints demonstrated articular erosions. The radial repair tissue contained unorganized collagen bundles and ground substance deficient in mucopolysaccharides. Groups S, P13 and P26 demonstrated no statistically significant differences between test and control limbs in compressive force-displacement behavior, input energy (EI), and ratio of dissipated to input energy (ED/EI). There were significant test-control differences in the load-displacement characteristics of Groups R13 (P less than 0.05) and R26 (P less than 0.05), with the repaired joint stiffer than the control. EI decreased 26% in Group R13 (not significant) and 34% in Group R26 (P less than 0.05), while the ratio ED/EI increased from 27% to 44% in Group R13 (not significant) and from 31% to 38% in Group R26 (P less than 0.05). Medial compartment contact area did not change significantly in either peripheral repair group, but decreased by 25% in Group R13 (P less than 0.05) and by 13% in Group R26 (P less than 0.05). Yield stress, maximum stress, and Young's modulus decreased significantly (P less than 0.05) relative to the controls in tensile tests of the radial repair tissue. There were no significant changes in these properties from 13 to 26 weeks. We concluded that in this animal model, the mechanical function of the meniscus is restored following repair of peripheral longitudinal lesions; however, it appears that in the radial repairs, progressive spreading at the repair site (filled by a fibrovascular scar) altered normal meniscal geometry and structure, adversely influencing mechanical function. Future studies may document whether protective measures (immobilization, limited weightbearing, etc.) can preserve normal mechanical function following repair of radial lesions.

Protective effects of corticosteroids on cartilage lesions and osteophyte formation in the Pond-Nuki dog model of osteoarthritis

The in vivo effects of corticosteroids on osteoarthritic (OA) lesions were examined in 12 dogs in which the anterior cruciate ligament had been sectioned. Six were treated with oral prednisone and 6 were treated with intraarticular (IA) injections of triamcinolone hexacetonide (TH), at surgery and 4 weeks later. Twelve other operated dogs received no treatment. All dogs were killed 8 weeks postsurgery. Four of 15 normal control dogs received IA TH injections. Operated untreated dogs developed significant cartilage lesions on the femoral condyles and tibial plateaus with prominent osteophytes. Operated dogs treated orally or with IA injections had a significant reduction in osteophyte size. Cartilage erosions on femoral condyles were observed in 25% of the untreated dogs, 8% of the dogs receiving oral prednisone, and none of the dogs receiving IA TH. In both groups of treated dogs, the size of the tibial plateau lesions was significantly reduced compared with the operated untreated dogs. Histologically, corticosteroids significantly reduced the severity of OA structural changes of the cartilage on both medial and lateral femoral condyles and tibial plateaus in operated animals, with the exception of the lateral plateaus of those treated orally. In electron microscopy studies, we found no evidence of increased cell degeneration or death associated with steroids. IA corticosteroids had no deleterious effects on normal articular cartilage. These results indicate that glucocorticoids administered orally or intraarticularly are effective against the development of OA lesions in this model.

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.

Degenerative changes in dog articular cartilage induced by a unilateral tibial valgus osteotomy

We present preliminary details of the changes that occur in a new model for the study of degenerative arthritis which does not involve intraarticular surgery. A unilateral valgus tibial osteotomy was performed in a group of 8 skeletally mature dogs of mixed breed and sex. Proximal tibial cartilages, femoral condyles and patellas were examined in operated and unoperated knees of experimental and unoperated dogs. Lesions were examined histologically and analyses were made of 35SO4 uptake and uronic acid content as measures of proteoglycan synthesis and content, respectively. Water contents were also determined. Dogs were examined from 22 to 62 weeks after osteotomy. Angulation induced by the osteoarthritis was varied from animal to animal in this preliminary study. Histologically, degeneration of the patella was observed in 3 of 5 experimental dogs and in both operated and unoperated limbs in two of the dogs. Lesions were seen in both limbs and were most common in the tibial plateau where they were present both in the lateral (covered by meniscus) and medical (uncovered) compartments of the operated and unoperated limb. In the tibial plateau initial increases in proteoglycan content and synthesis were recorded in both limbs: later after 30/36 weeks these declined to normal. In the femoral condyles, increases in water content with angulation were seen in the lateral and medial condyles of operated limbs and in the medial condyles of unoperated limbs. Other changes in proteoglycan content were observed in both condyles with a loss of proteoglycan with increased angulation being recorded in the lateral condyle of the operated limb and an increase in proteoglycan with angulation in the medial condyle of the unoperated limb. These early changes are presumably in response to alterations in load bearing in both limbs. CLINICAL RELEVANCE. This study permits an analysis of degenerative changes that can occur when articulation is changed by an osteotomy. Since the changes occur in both limbs, are potentially reversible and are induced by extraarticular surgery, we have an attractive new model for studying degenerative arthritis.

Protease inhibitors decrease rabbit cartilage degradation after meniscectomy

In vitro proteoglycan (PG) synthesis and release were measured on cartilage removed from rabbit knees within 1 week of meniscectomy. Three days following partial lateral meniscectomy, 72% of the femurs and 82% of the tibias had visible ulcers. Cartilage from the weight-bearing areas incorporated 2.0-2.9 times more 35S-sulfate in vitro than cartilage from the opposite, unoperated knees. 3H-thymidine incorporation was 2.5-3.4 times higher for surgical than control groups. 35S-sulfate incorporation by the surgical group was inhibited by 22% in the presence of 10(-4) M U24522, an inhibitor of rabbit chondrocyte metalloprotease (CMP). 3H-thymidine incorporation by the surgical group was inhibited by 28% by 10(-4) M U24522. In vitro PG release from cartilage removed 2 days after surgery was 1.6-3.7 times higher for the surgical than the control group. PG release by the surgical group after 22 h of incubation was reduced to the control level by three CMP inhibitors, U24278, U24279, and U24522. PG release by cartilage from the nonsurgical group was also reduced by these compounds at 22 h. These results suggest that both the anabolic and catabolic processes that are stimulated by surgery can be isolated in vitro and that CMP may be involved in the catabolic process.

Synovial membrane and cartilage changes in experimental osteoarthrosis

The Hulth instability model was performed on 25 rabbit knee joints. Electron-microscopic, light-microscopic, and histomorphometric data demonstrated consistent chondrocyte alterations and cartilage destruction. The comparison between operated, sham, and control knees shows that surgical intervention without surgically induced instability is followed by changes in the synovial membrane and cartilage. The cartilage destruction is preceded by a synovial reaction, suggesting that the inflammatory response has an important role in the onset of cartilage damage in this model. The damage was more severe in the experimental knees, suggesting that mechanical instability is also a factor in cartilage destruction.

Effect of S-adenosylmethionine on experimental osteoarthritis in rabbits

Twenty-four rabbits with surgically induced osteoarthritis of the knee were allocated into three treatment groups (placebo, S-adenosylmethionine (SAMe) 30 mg/kg per day, and SAMe 60 mg/kg per day). Intramuscular administration of drug or placebo was begun immediately after surgery and continued for 12 consecutive weeks. At the end of the treatment period, animals were killed, and the articular surfaces of the knees were studied using histologic and histochemical techniques. Microscopic studies showed that the number of cells and the depth of the cartilage were significantly (p less than 0.001) increased in SAMe-treated rabbits in comparison with placebo-treated animals. No difference was found in comparing data in animals given SAMe at the two dosage levels. In conclusion, these results suggest a chondroprotective effect of SAMe in animals with experimental osteoarthritis.

S-adenosylmethionine in the treatment of osteoarthritis. Review of the clinical studies

S-Adenosylmethionine (SAMe), a physiologic compound that ranks with ATP as a pivotal molecule in biology, offers physicians an innovative approach to the treatment of osteoarthritis. Experimental investigations suggest that the administration of SAMe exerts analgesic and antiphlogistic activities and stimulates the synthesis of proteoglycans by articular chondrocytes with minimal or absent side effects on the gastrointestinal tract and other organs. The results of extensive clinical trials, which have enrolled about 22,000 patients with osteoarthritis in the last five years, support the clinical effectiveness and the optimal tolerability of SAMe administration. The intensity of therapeutic activity of SAMe against osteoarthritis is similar to that exerted by nonsteroidal anti-inflammatory drugs, but its tolerability is higher. Based on these findings, SAMe is proposed as the prototype of a new class of safe drugs for the treatment of osteoarthritis.

Primary osteoarthritis: epidemiology, clinical aspects, and general management

The etiology of osteoarthritis, the most common articular disorder, is still unknown. Epidemiologic studies demonstrate a relationship to aging and to certain occupations; relationships to obesity as an etiologic factor remain controversial. An inverse relationship of osteoarthritis and bony density has been observed. Medical management is primarily symptomatic; surgery, particularly of the hip or knee, restores function and relieves pain at late stages of the disease. Investigational trials of specific therapeutic agents suggest possible forthcoming interventions to prevent, retard, or reverse the disease process.

Progressive chronic osteoarthritis in femorotibial joints of partial medial meniscectomized guinea pigs

The sequential histopathologic alterations in femorotibial joints of partial meniscectomized male and female guinea pigs were evaluated at 1, 2, 3, 6, and 12 weeks post-surgery. Foci of moderate to severe cartilage degeneration were present in the medial tibial plateau and femoral condyle of the operated leg by 1 week post-surgery. At 2 weeks post-surgery, the cartilage degeneration in the operated legs was more extensive and there was evidence of early chondrophyte formation on the medial side of either the femur or tibia in three animals. Changes were progressively more severe at 3, 6, and 12 weeks. Focal areas of minimal to mild cartilage degeneration were in the medial tibial plateau of the contralateral nonoperated leg in some animals at 3 weeks post-surgery and in all animals at 12 weeks post-surgery. Changes in the contralateral leg of meniscectomized guinea pigs have not been described previously. Since cartilage degeneration was often severe by 1 week post-surgery, the model has limited utility for testing agents designed to modify the degenerative process in the operated leg. Milder, more slowly progressive lesions in the contralateral leg may be amenable to therapeutic intervention.

In vitro cell proliferation and proteoglycan synthesis of rabbit meniscal fibrochondrocytes as a function of age and sex

Meniscal fibrochondrocytes from male and female New Zealand white rabbits, ages 6, 12, and 24 months, were grown in primary and secondary monolayer cell culture. Neither age nor sex affected the majority of their cell culture characteristics. Cells from young males (6 months old) synthesized greater amounts of sulfated proteoglycans than did those from young females, but by 2 years of age, this result was reversed. All age groups synthesized 2 classes of proteoglycans, based on hydrodynamic size, but the ratio of the 2 classes changed as a function of age. Overall, the meniscal fibrochondrocytes from both skeletally immature and skeletally mature rabbits of both sexes were capable of proliferation and matrix synthesis in vitro.

Analysis of osteoarthritic cartilage using monoclonal antibodies reactive with rabbit proteoglycan

Femoral and tibial cartilage specimens from nonoperated, sham operated, and partially meniscectomized knees of New Zealand white rabbits were studied, using fluorescein-conjugated mouse IgG or 3 monoclonal antibodies (2G2, 2E9, and 6C9) that portrayed differing fine antigenic specificity for rabbit cartilage proteoglycan monomer. In nonoperated and sham operated animals, monoclonal antibodies 2G2 and 2E9 stained cellular/pericellular (C/PC) and matrix areas; antibody 6C9 stained only C/PC areas. Augmented C/PC and matrix staining of osteoarthritic femoral cartilage occurred with 2G2 and 6C9; tibial cartilage staining was reduced. Increased 2E9 staining of C/PC regions was seen in tibial cartilage. The differential staining patterns indicate that proteoglycan macromolecular changes occur in experimental osteoarthritis and that these monoclonal antibodies can be utilized as probes for the connective tissue changes observed.

Experimental arthrosis by hyperpressure

The frequent occurrence of degenerative joint disease (DJD) pathology and the high degree of functional prejudice associated with it, justify the search for experimental models with a view to a better understanding of this pathology and its treatment. The models most commonly used resort to a sudden mechanical degradation by shock (post-contusive osteoarthritis) or to a kinematic disruption of the joint through more or less extensive menisco-capsulo-ligamentary lesions or lesions induced by toxic substances.

Cartilaginous lesions met with in human pathology are often secondary to a morphological anomaly at the origin of a hyperpressure. Maquet (1977) has suggested the bringing forward of the anterior tibial tubercle (ATT) in order to reduce the retro-patellar pressure. The drawing back by hollowing of this ATT appeared to us a suitable model for experimental osteoarthritis by hyperpressure.

Experimental osteoarthritis induced by selective myectomy and tendotomy

A new model of osteoarthritis has been developed that utilizes an extraarticular surgical technique to alter gait and weight-bearing capabilities in the hind limbs of experimental animals. Guinea pigs, averaging 650 gm in weight, were subjected to unilateral resection of a segment of the gluteal muscles at the sacral origin, to section of the infrapatellar ligament, or to both procedures. Progressive changes consistent with osteoarthritis developed over 10-24 weeks as judged by gross, radiologic, and microscopic findings. In addition, an increase in mean cartilage water content and 35SO4(-2) incorporation into proteoglycans by 10 and 14 weeks, respectively, were consistent with the chemical changes observed in early osteoarthritis. Abnormalities developed not only in the operated hind limb, but in the contralateral, unoperated hind limb at a slightly later time. Thus, this animal model provided the opportunity to evaluate a mild gait abnormality and other biomechanical influences on the evolution of osteoarthritis which is uninfluenced by any intraarticular joint trauma.

Joint reaction to polyethylene implantation: a method for inducing osteoarthritic change and osteophyte formation in the rabbit knee joint

Joint lesions were induced by implantation of a rigid piece of polyethylene sutured under the patella and quadriceps tendon of the rabbit's right knee. Compared to the left sham-operated knee, follow-up studies revealed progressive changes that consisted of early and transient synovial hyperemia and proliferation and late osteoarthritis. By day 7 after surgery, soft synovial-like tissue proliferated around the implant and the articular margins of the femoral trochlea indicating primitive "osteophytic" protuberances (synoviophytes). By day 15 after surgery, the synoviophytes had acquired a more solid consistency and were composed mostly of fibrocartilage covered by a fibro-cellular synovial lining (chondrophytes). By that time, this tissue was invaded with vascular channels; signs of ossification were already present in the deepest layer adjacent to bone. Between the 2nd and 12th weeks, this fibro-cartilaginous tissue, except for the surface fibrous or fibrocartilaginous layer, was progressively replaced by immature bone (osteophyte). Secondary bone remodeling started soon after the first lamellae of immature bone were deposited. Complete integration of the osteophyte into the distal femur occurred during the 2nd and 3rd month.

Characterization of newly synthesized proteoglycans from rabbit menisci in organ culture

Rabbit menisci were incubated with Na2 35SO4 in short-term organ culture to label newly synthesized proteoglycans. The radioactive products present in both tissue and culture medium were characterized separately with respect to distribution after ultracentrifugation in CsCl isopycnic density gradients, hydrodynamic size, interaction with hyaluronic acid, and glycosaminoglycan composition (types, size and content). Analysis of proteoglycan size by gel-filtration chromatography of the most-dense CsCl fractions (A1) on Sephacryl S-500 (associative conditions) resolved three species. A peak with Kav. approx. 0.7 was present in each chromatogram, and constituted the principal component in tissue extracts. Two other peaks with Kav. values of approx. 0.2 and 0.45 were also found. When the A1 fraction from tissue was subjected to CsCl-density-gradient ultracentrifugation under dissociative conditions, 71% of the recovered radioactivity was present in the most dense (A1D1) fraction. Incubation with hyaluronic acid of either A1 or A1D1 fraction from associative extract did not alter the apparent size of the labelled product, indicating a lack of aggregate formation. Meniscal proteoglycans showed an unusual and marked tendency to adsorb irreversibly to agarose and agarose-containing gel-filtration-chromatography media. High-pressure liquid-chromatographic analyses indicated that the sulphated glycosaminoglycans consisted of chondroitin 6-sulphate (72%), chondroitin 4-sulphate (19%) and dermatan sulphate (5%). Endo-beta-galactosidase (keratanase) digestion of the material failed to detect the presence of keratan sulphate. Of the labelled glycosaminoglycans, 95% was eluted from Sephacryl S-400 as a single symmetrical peak with a Kav. of 0.5. The results of studies with tissue extracts and culture medium were similar.

Articular cartilage after meniscectomy. Rabbit knees studied with the scanning electron microscope

Ten rabbits had a medial meniscectomy in both knees. The articular surface was studied with a scanning electron microscope 2, 4 or 12 weeks after the operation. Three sham operated and two unoperated rabbits served as controls. Progressive articular cartilage damage was observed on the weight-bearing areas of the medial condyles. The findings are compatible with clinical observations after meniscectomy; they confirm that meniscectomy is not a harmless operation.

Correlation of histopathology and sulfated proteoglycans in human osteoarthritic hip cartilage

The histopathologic characteristics, in vitro proteoglycan and glycosaminoglycan biosynthesis, and proteoglycan content of osteoarthritic (OA) cartilage tissue types from human femoral heads obtained at the time of total joint replacement were compared. Articular cartilage from fibrillated or discolored cartilage surfaces demonstrated overlapping histopathologic patterns, while cartilage from osteophytic areas was distinct. 35SO4 from each of these three tissue types was found in two peaks of radioactivity on a Sepharose CL-2B column. The average partition coefficient (Kav) of the first peak (peak I) was 0.07, while that of the second (peak II) was 0.63. Proteoglycan monomer predominated in discolored, fibrillated, and osteophytic OA cartilage in peak I. The hydrodynamic size on Sepharose CL-2B of the synthetic proteoglycan monomer was the same for discolored, fibrillated, and osteophytic samples (Kav, 0.25-0.28). Discolored and fibrillated tissues showed a similar percentage of proteoglycan monomer in peak II, whereas osteophyte was reduced in proteoglycan monomer content in peak II. In addition, the endogenous proteoglycans extracted from each cartilage area were generally of a smaller hydrodynamic size than the newly synthesized peak I or proteoglycan monomer. Glycosaminoglycans were predominantly chondroitin 6-sulfate. These results indicated that OA discolored and fibrillated cartilage tissue types from defined topographical areas of human femoral heads possessed neither unique histopathologic nor synthetic or endogenous proteoglycan characteristics. Osteophytic cartilage appeared more histopathologically distinct than either discolored or fibrillated OA cartilage, but synthesized proteoglycan monomer with similar hydrodynamic size to the other cartilage tissue types.

A new model of osteoarthritis in rabbits. I. Development of knee joint pathology following lateral meniscectomy and section of the fibular collateral and sesamoid ligaments

A partial lateral meniscectomy procedure has been developed for the induction of a predictable and reproducible degenerative joint disease in knees of rabbits. The procedure adopted involves section of the fibular collateral and sesamoid ligaments and removal of 4-5 mm of the anterior lateral meniscus. In most experiments the animals are killed and tissues obtained for histologic examination at 6 weeks. Section of the ligaments alone (with or without penetration of the joint space) did not result in significant pathologic change. Significant degeneration was observed in tibial and femoral cartilage when the meniscus as well as the ligaments were cut, but the most extensive lesions were seen when a piece of the anterolateral meniscus was actually removed. These lesions included fibrillation, ulceration and erosion, "clone" and osteophyte formation, loss of chondrocytes, and loss of safraninophilic staining in the articular cartilage. The incidence and distribution of lesions with time following surgery were also investigated. Lesions were observed as early as 1-2 weeks post-surgery and increased in number and severity up to 12 weeks. A global scoring system has been devised to permit statistical comparisons of lesion incidence and severity in different groups of rabbits. This scoring system has enabled us to test drug efficacy in the rabbit lateral meniscectomy model of osteoarthritis.

Biosynthesis of proteoglycan in vitro by cartilage from human osteochondrophytic spurs

Proteoglycan biosynthesis by human osteochondrophytic spurs (osteophytes) obtained from osteoarthritic femoral heads at the time of surgical joint replacement was studied under defined culture conditions in vitro. Osteophytes were primarily present in two anatomic locations, marginal and epi-articular. Minced tissue slices were incubated in the presence of [(35)S]sulphate or [(14)C]glucosamine. Osteophytes incorporated both labelled precursors into proteoglycan, which was subsequently characterized by CsCl-isopycnic-density-gradient ultracentrifugation and chromatography on Sepharose CL-2B. The material extracted with 0.5m-guanidinium chloride showed 78.1% of [(35)S]sulphate in the A1 fraction after centrifugation. Only 23.0% of the [(35)S]sulphate in this A1 fraction was eluted in the void volume of Sepharose CL-2B under associative conditions. About 60-80% of the [(35)S]sulphate in the tissue 4m-guanidinium chloride extract was associated with monomeric proteoglycan (fraction D1). The average partition coefficient (K(av.)) of the proteoglycan monomer on Sepharose CL-2B was 0.28-0.33. Approx. 12.4% of this monomer formed stable aggregates with high-molecular-weight hyaluronic acid in vitro. Sepharose CL-2B chromatography of fractions with lower buoyant densities (fractions D2-D4) demonstrated elution profiles on Sepharose CL-2B substantially different than that of fraction D1, indicative of the polydisperse nature of the newly synthesized proteoglycan. Analysis of the composition and chain size of the glycosaminoglycans showed the following: (1) preferential elution of both [(35)S]sulphate and [(14)C]glucosamine in the 0.5m-LiCl fraction on DEAE-cellulose; (2) the predominant sulphated glycosaminoglycan was chondroitin 6-sulphate (60-70%), with 9-11% keratan sulphate in the monomer proteoglycan; (3) K(av.) values of 0.38 on Sephadex G-200 and 0.48 on Sepharose CL-6B were obtained with papain-digested and NaBH(4)-treated D1 monomer respectively. A comparison of the synthetic with endogenous glycosaminoglycans indicated similar types. These studies indicated that human osteophytes synthesized in vitro sulphated proteoglycans with some characteristics similar to those of mature human articular cartilage, notably in the size of their proteoglycan monomer and predominance of chondroitin 6-sulphate. They differed from articular cartilage primarily in the lack of substantial quantities of keratan sulphate and aggregation properties associated with monomer interaction with hyaluronic acid.

Immunity to homologous type III collagen after partial meniscectomy and sham surgery in rabbits

Cellular immunity to rabbit types I, II, and III collagen was detected after both partial medial meniscectomy and sham operation in rabbits when an in vitro 3H-thymidine incorporation assay was used. The blastogenic responses were commonly directed towards peptides derived from collagens by cyanogen bromide cleavage used to mimic proteinase degradation products. The responses to type III collagen peptides were by far the strongest and were seen in most rabbits that were operated on. We suggest that the responses to types I and II collagen were caused by a cross-reaction with type III collagen peptides. This conclusion was supported by the observation that spleen cells from rabbits directly immunized with homologous type III collagen peptides in Freund's complete adjuvant responded strongly to the immunizing peptides and also cross-reacted with types I and II collagen peptides. Immunity to cartilage proteoglycans was observed primarily in rabbits that had undergone meniscectomy and had severe cartilage degeneration. These results indicated that immunity to collagens will develop merely as a result of joint surgery, whereas immunity to proteoglycans is largely dependent upon an osteoarthritic lesion.

Metabolic responses of cartilage in experimentally induced osteoarthritis

Serial metabolic responses in developing osteoarthritis induced in the right knees of a rabbit model of partial meniscectomy (PM) were studied. Controls were sham-operated (SH) right knees, left knees of all operated animals, nd right and left knees of a nonoperated series. Glycosaminoglycan and protein synthesis and cell replication were separately analysed utilising 35 SO4, 14C-Glycine, and 3H-thymidine, respectively. Pitting, ulceration, and osteophytes, seen only in the PM knees, increased over the 12-week period of study. 3H-thymidine and 14C-glycine incorporations by PM cartilage were increased at 3 weeks, less than nonoperated control animals at 9 weeks, and approximated to those of controls at 12 weeks. 35 SO4 incorporation by tibial osteophytes was decreased at 9 and 12 weeks. Similar isotope incorporations seen after partial meniscectomy and sham surgery represented a nonspecific response to arthrotomy. Cartilage synthetic activity did not increase in parallel with degenerative change.

Prostaglandin biosynthesis by lapine articular chondrocytes in culture

Secondary monolayer and spinner cultures of rabbit articular chondrocytes released into the culture medium prostaglandins the synthesis of which was inhibited by sodium meclofenamate. The prostaglandins measured by radioimmunoassay were, in order of decreasing abundance, prostaglandin E2, 6-oxo-prostaglandin F1 alpha (the stable metabolite of prostacyclin) and prostaglandin F2 alpha. Several lines of evidence indicated that chondrocytes synthesize little if any thromboxane B2 (the stable metabolite of thromboxane A2). The presence of prostaglandins was confirmed by radiometric thin-layer chromatography of extracts of culture media incubated with [3H]arachidonic acid-labeled cells. In monolayer culture, chondrocytes synthesized immunoreactive prostaglandins in serum-free as well as serum-containing medium. Monolayer chondrocytes produced higher levels of prostaglandin E2 relative to 6-oxo-prostaglandin F1 alpha than did spinner cells, but the latter synthesized more total prostaglandins. The identity of endogenous prostaglandins as well as those synthesized in short-term culture by rabbit cartilage slices was compared to those produced by chondrocytes in long-term culture. Chondrocytes synthesized all of the prostaglandins found in articular cartilage. Minimal quantities of thromboxane B2 were detected in cartilage. A higher percentage of 6-oxo-prostaglandin F1 alpha relative to other prostaglandins was found in cartilage than in either monolayer or spinner chondrocyte cultures. These results demonstrate that articular chondrocytes synthesize prostaglandins and prostacyclin. These prostaglandins may exert significant physiological effects on cartilage, since exogenous prostaglandins depress chondrocyte sulfated-proteoglycan synthesis and may even promote proteoglycan degradation.