Microinjury to the synovial membrane may cause disaggregation of proteoglycans in rabbit knee joint articular cartilage

Intra-articular morphine and saline injections induce release of large molecular weight proteoglycans into equine synovial fluid

Both morphine and physiologic saline injected intra-articularly into healthy equine tarsocrural joints induced a release of large molecular size proteoglycan (PG) subunits into the synovial fluid (SF) analysed 24 h postinjection. High-performance liquid chromatography (HPLC) with a size-exclusion column was used to assess the high molecular weight proteoglycans in equine synovial fluid (SF). The PG peaks of SF samples eluated separately from SF hyaluronate and other molecular components of the SF in the HPLC chromatographies indicating no interaction between hyaluronate and PG in the SF. Individual elution profiles varied between joints and horses. The amount of PG release was measured by relative area index from the HPLC chromatograms. The synovial fluid PG content was significantly increased (P < 0.05) after morphine but not in saline injected joints compared with pretreatment but there were no significant differences between the two groups. It was concluded that intra-articular injections of both morphine and physiologic saline are able to elicit a marked PG release into the SF from articular cartilage within 24 h of injection.

Effects of valgus tibial angulation on cartilage degeneration in the rabbit knee

Thirteen adult female rabbits underwent unilateral osteotomy of the proximal tibia. In nine animals, 30 degrees of valgus angulation was created; in four animals, osteotomy without angulation was performed. After a 12-week survival period, the knee joints were processed for histology by staining with hematoxylin and eosin and safranin O. Additionally, the chondroitin sulphate epitopes 3-B-3(-) and 7-D-4 were evaluated immunohistochemically as markers of osteoarthritis. Changes of the articular surface of the tibia were visualized by scanning electron microscopy. Light microscopic evaluation by the Mankin et al. scoring system revealed mild or moderate damage of the cartilage in the lateral compartment of angulated extremities when compared with the control side. Immunohistology with the monoclonal 3-B-3 and 7-D-4 antibodies showed no increased expression of these epitopes in the lateral compartments of the knee. Scanning electron microscopic evaluation of the tibial surfaces revealed slight surface damage localized to the central, weight-bearing portion of the lateral tibial plateau of angulated extremities. Angulation of 30 degrees led to only mild degenerative changes of the cartilage. These results indicate that, in the short term, cartilage has considerable capacity to withstand the effects caused by severe angulation of the limb.

Intra-articular injections and articular cartilage metabolism. An experimental study in rabbits

We studied the effects of repeated intra-articular injections of sterile 140 mM NaCl solution on articular cartilage in adult rabbits. After 20 injections into the knee joints over a period of 4 weeks, chondrocyte glucosaminoglycan synthesis was evenly reduced in all cartilage layers, accompanied by a significant proteoglycan depletion of the matrix which was most marked in the superficial half of the cartilage. These and other changes only partially reversed during a further 4-week period after the injections had been stopped. Our data underline the need for a clear-cut indication for intra-articular injections. The microtrauma caused by injection, in conjunction with the introduction of a carrier solution into the joint, may, at least when repeated at short intervals, lead to measurable damage to the articular cartilage.

Morphologic and morphometric changes in synovial membrane associated with mechanically induced osteoarthrosis

We sought to determine whether synovial leukocytic inflammation is a primary event in mechanically induced osteoarthrosis. Repetitive impulse loading (50 ms duration at 60 Hz for 40 minutes each day) was applied to the right hindlimbs of 24 New Zealand white rabbits for 3, 6, or 9 weeks. The synovial membrane from the medial suprapatellar area was examined qualitatively using transmission electron microscopy and quantitatively using light microscopic morphometry. The results indicate that synovial inflammation is not a primary event in this mechanically induced osteoarthrosis, but synovial hyperplasia occurs prior to histologically evident cartilage destruction at 6-9 weeks.

Retardation of articular cartilage degradation by glycosaminoglycan polysulfate, pentosan polysulfate, and DH-40J in the rat air pouch model

The rat subcutaneous air pouch model was adapted to examine the in vivo degradation of implanted rabbit articular cartilage, both with and without induced air pouch inflammation, over a 7-day period. The effects of 3 drugs, glycosaminoglycan polysulfate (Arteparon), pentosan polysulfate (SP-54), and zinc-chelated pentosan polysulfate (DH-40J), on inflammation-induced cartilage degradation were also examined. Implanted articular cartilage from noninflamed air pouches showed a reduction in total proteoglycan (PG) content (as hexuronic acid), but not in PG extractability or aggregation, compared with cartilage maintained in tissue culture. The injection of peptone into the air pouch as an inflammogen caused an influx of leukocytes and plasma exudate and a reduction in implanted articular cartilage PG content, extractability, and aggregation, which was significantly greater than that which occurred in noninflamed air pouches. In vitro experiments demonstrated that peptone did not have a direct effect on cartilage PG degradation. Daily injection of Arteparon, SP-54, or DH-40J (10 mg/kg) into peptone-inflamed air pouches significantly increased the PG content, extractability, and aggregation in implanted articular cartilage, compared with that in cartilage from non-drug-treated control animals. The infiltration of leukocytes into the peptone-inflamed air pouches was significantly reduced by daily administration of Arteparon, 10 mg/kg. At an equivalent dose, DH-40J increased leukocyte numbers in the pouch fluid, whereas SP-54 had no significant effect on leukocyte accumulation.

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.

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.

Variations of the proteoglycans of the canine intervertebral disc with ageing

A group of young (2.0 +/- 0.6 years) (group 1) and old (9.7 +/- 1.5 years) (group 2) beagle dogs were given Na2 35SO4 (1.0 mCi/kg) intravenously 60 days prior to being killed to radiolabel their proteoglycans. Lumbar discs were removed and dissected into nucleus pulposus and annulus fibrosus. Proteoglycans were extracted at 4 degrees C from these tissues with buffered 4.0 M Gdn-HCl containing proteinase inhibitors, and purified by CsCl density gradient ultracentrifugation. The average hydrodynamic size and ability of the purified proteoglycans to aggregate in the presence of excess hyaluronic acid was determined by Sepharose CL-2B chromatography. The galactosamine/glucosamine ratios of these proteoglycans as well as their non-aggregating fractions were also ascertained. The proteoglycan content of discs of old animals was significantly less than in the young. The proportion of 35S-labelled, or non-labelled proteoglycans which could aggregate in the presence of hyaluronic acid was also much lower in the preparations isolated from the older discs. In contrast, the average hydrodynamic size of the non-aggregating proteoglycans isolated from the annuli fibrosi of group 2 animals were larger than the corresponding population of group 1 animals. Aminosugar analysis of these same proteoglycan fractions from older animals afforded galactosamine/glucosamine ratios (mean 1.81 +/- 0.14) which were less than the younger age group (mean 2.63 +/- 0.40). These data suggest that with ageing and degeneration the proteoglycans of the beagle disc undergo increased degradation with the accumulation in the annulus fibrosus of a population which is of larger average hydrodynamic size and richer in keratan sulphate than proteoglycans present in younger tissues.