Topic:Articular Cartilage
Articular cartilage in horses is a specialized connective tissue found at the ends of bones within joints. It provides a smooth, lubricated surface for articulation and facilitates the transmission of loads with a low frictional coefficient. Articular cartilage is primarily composed of chondrocytes, collagen fibers, and proteoglycans, and it lacks blood vessels, nerves, and lymphatics. This avascular nature contributes to its limited capacity for self-repair following injury. The health and integrity of articular cartilage are essential for maintaining joint function and mobility in horses. This page compiles peer-reviewed research studies and scholarly articles that explore the structure, function, and pathological changes of articular cartilage in equine species, as well as advancements in diagnostic and therapeutic approaches for cartilage-related disorders.
Surgical treatment of subchondral cyst-like lesions in the tibia of an adult pony. A 13 year-old pony was evaluated because of right hind limb lameness of acute onset. Radiographs of the right tarsus obtained shortly after the onset of lameness were normal, but results of nuclear scintigraphy were abnormal. Two radiolucent subchondral cyst-like lesions of the distal part of the tibia were seen on radiographs obtained 9 months later. The lesions were surgically decompressed, and the pony was sound 1 year later. It is hypothesized that a traumatic insult created a crack or split in the articular cartilage that allowed subsequent development of the cyst-like lesions.
Repair and function of synovium after arthroscopic synovectomy of the dorsal compartment of the equine antebrachiocarpal joint. The reparative ability of equine synovium was determined by gross, histological, and ultrastructural examination. The functional potential of the synovium was estimated by examination of synovial cell organelles with transmission electron microscopy. Results from rested and exercised horses were compared to determine the effect of exercise on synovial healing. The response of synovectomized joint to exercise was evaluated with a standardized lameness examination and by gross, histological, and histochemical observations of the articular cartilage. A 7-mm diameter motorized synovial resector wa...
Effects of holmium: YAG laser energy on cartilage metabolism, healing, and biochemical properties of lesional and perilesional tissue in a weight-bearing model. Comparison of perilesional cartilage, lesional repair tissue, and subchondral bone activity 6 months after application of holmium-yttrium-aluminum-garnet (Ho:YAG) laser energy to chronic (10 week) induced 10-mm full-thickness (FT) circular articular cartilage craters followed by 6 months' intermittent active motion (IAM) in a free exercise environment was investigated. The 2.1-microns wavelength was delivered in hand-controlled near-contact mode by arthroscopic surgery in a saline medium. Bilateral arthroscopy was performed on normal antebrachiocarpal, intercarpal, and metacarpophalangeal join...
The dose-related effects of phenylbutazone and a methylprednisolone acetate formulation (Depo-Medrol) on cultured explants of equine carpal articular cartilage. The dose-related effects of phenylbutazone and Depo-Medrol on chondrocyte viability and chondrocyte-mediated synthesis and depletion of proteoglycans were investigated using cultured explants of equine middle carpal joint articular cartilage. Explants from 12 horses (941 x 3 mm diameter) were cultured for a total of 5 days, which included 3 days' exposure to either phenylbutazone (0, 2, 20, 200 or 2000 micrograms/mL) or Depo-Medrol (0, 20, 200 or 2000 micrograms/mL). For each explant, amino sugar content was used as a measure of proteoglycan content, 35S incorporation as a measure of the rate ...
Site-specific proteoglycan characteristics of third carpal articular cartilage in exercised and nonexercised horses. The relevance of site and the influence of exercise on third carpal articular cartilage proteoglycan (PG) were assessed in 16 horses. Six horses were exercised (exercised group) for 30 minutes, 3 times/wk, for 6 weeks. The other 10 horses (nonexercised group) were housed in box stalls for the same 6-week period. At week 6, articular cartilage from the proximal surface of the right third carpal bone was harvested and cultured with radioactive sulfate to label newly synthesized PG. Endogenous PG was measured by use of a uronic acid assay. Newly synthesized and endogenous PG were characterized by...
Biomechanical properties of third carpal articular cartilage in exercised and nonexercised horses. The relevance of site and exercise on the biomechanical properties of the articular cartilage from the equine third carpal bone were assessed by creep indentation testing. Six horses were exercised for 30 minutes three times weekly. Another six horses were housed in box stalls and were not exercised. At the conclusion of the study, one third carpal bone from each horse was harvested and the KLM biphasic material properties of cartilage were determined at 12 sites. There was a significant (p < 0.01) effect of site but not exercise on the cartilage aggregate modulus, which was significantly l...
Osteochondrosis of the articular-epiphyseal cartilage complex in young horses: evidence for a defect in cartilage canal blood supply. The objectives of this study were to determine in horses 1) the ages at which viable cartilage canal vessels are present in the articular-epiphyseal cartilage complex of three predilection sites and one nonpredilection site of osteochondrosis (OC), 2) the prevalence of lesions of OC in these sites, and 3) whether there was an association of lesions of OC with necrotic cartilage canal blood vessels. The medial femoral condyle, lateral femoral trochlear ridge, and distal ends of the tibia and proximal phalanx were examined grossly, microradiographically, and histologically in 35 horses 18 months...
Arthroscopic findings in the carpal joints of lame horses without radiographically visible abnormalities: 41 cases (1986-1991). Arthroscopy was performed in 1 carpal joint unilaterally in 27 horses and either in 2 carpal joints unilaterally or 1 carpal joint bilaterally in 7 horses. All horses were lame, but the cause of lameness could not be determined from radiographs. Twenty-seven carpi did not have radiographically visible abnormalities; the remaining 14 had only mild to moderate lucency or sclerosis of the radial facet of the third carpal bone. The primary abnormalities identified during arthroscopy included a crush fracture of the third carpal bone (7 carpi), an incomplete fracture of the third carpal bone in the...
Proteoglycan metabolism of equine articular cartilage and its modulation by insulin-like growth factors. The effect of human recombinant insulin-like growth factor 1 (rhIGF-1) on proteoglycan (PG) metabolism of full thickness equine articular cartilage explants was investigated. PG synthesis was stimulated at all ages, but higher concentrations of rhIGF-1 were required for maximal stimulation of adult cartilage. There were no changes in the hydrodynamic size, electrophoretic heterogeneity or composition of proteoglycans isolated from rhIGF-1-stimulated cartilage. rhIGF-1 reduced the rate of turnover of both newly synthesized and endogenous proteoglycans in all ages of cartilage investigated. The ...
Local and remote matrix responses to chondrocyte-laden collagen scaffold implantation in extensive articular cartilage defects. Chondrocyte-laden collagen scaffolds were evaluated in extensive cartilage defects in an equine model. Arthroscopic techniques were used to implant a chondrocyte-collagen culture product in 15-mm defects in the lateral trochlear ridge of the femoropatellar joint of 12 horses. Ungrafted control defects were formed in the opposite joint. Groups of six horses were terminated at 4 and 8 months after implantation and the repair sites, adjacent cartilage, and remote cartilage within each femoropatellar joint examined biochemically. Eight months following surgery the relative proportions of type II c...
Arthroscopic removal of axial osteochondral fragments of the plantar/palmar proximal aspect of the proximal phalanx in horses: 119 cases (1988-1992). Medical records from 119 horses that had undergone arthroscopic surgery for removal of axial osteochondral fragments of the palmar/plantar proximal aspect of the proximal phalanx were reviewed. Standardbred racehorses represented 109 (92%) of those affected. Ninety-three (78%) of the horses were < 3 years old. Gender distribution was consistent with that of the equine hospital population. Fragments most commonly were observed in the hind limbs (155/164; 95%), specifically, on the medial aspect of the left hind limb (72/164; 44%). Bilateral fragmentation occurred in 21 of 119 (18%) horses, a...
Comparison of the cranial and a new lateral approach to the femoropatellar joint for aspiration and injection in horses. The genual joint in horses is complex, making synovial fluid aspiration and injection of the femoropatellar joint difficult. Horses commonly have signs of resentment to needle penetration at this site. We compared the safety and efficacy of a new technique, using a lateral approach to the femoropatellar joint, with that of the standard cranial approach in 12 horses. A significantly greater amount of fluid was obtained with the lateral approach (2.0 +/- 0.5 ml, mean +/- SEM) than with the cranial approach (0.9 +/- 0.2 ml). Significant differences were not observed in color, nucleated cell count...
Lead foreign body arthropathy in a horse. A diagnosis of degenerative joint disease secondary to an intra-articular metallic foreign body in the right metacarpophalangeal joint was made in a Quarter Horse gelding. Arthroscopy, performed to evaluate the joint and remove the foreign body, revealed yellow discoloration of the articular cartilage and synovium, and blunting and proliferation of the synovium. The foreign body was identified as a lead sphere. Microscopic examination of synovium revealed chronic synovitis, with accumulation of hemosiderin and multifocal, mild mineralization. Another pigment was evident extracellularly in the ...
Effect of bacterial lipopolysaccharides on sulfated glycosaminoglycan metabolism and prostaglandin E2 synthesis in equine cartilage explant cultures. The metabolic responses of equine articular cartilage to incubation with bacterial lipopolysaccharide (LPS) were studied, using explant cultures of articular cartilage obtained from the metatarsophalangeal joints of 15 horses, age of which ranged from 3 months to 20 years. For comparison, explants were also established from the metatarsophalangeal joints of 3 calves. Explants were cultured for 3 days in medium containing various concentrations of LPS from 0 (control) to 100 micrograms/ml. Glycosaminoglycan (GAG) released during the 3-day incubation was determined by a spectrophotometric assay,...
Crystals in equine articular cartilage. Crystal deposits have been observed in equine articular cartilage and identified by scanning electron microscopy and X-ray diffraction as octacalcium phosphate and calcium pyrophosphate dihydrate. Of 89 equine fetlock joints examined 10 contained evidence of calcification visible by eye. It is suggested that the deposition of crystals may be a mediator of arthritis in horses and may also cause damage directly.
Chondrocyte-fibrin matrix transplants for resurfacing extensive articular cartilage defects. Cartilage resurfacing by chondrocyte implantation, with fibrin used as a vehicle, was examined in large (12 mm) full-thickness articular cartilage defects in horses. Articular chondrocytes, isolated from a 9-day-old foal, were mixed with fibrinogen and injected with thrombin, in a 1:1 mixture, into 12 mm circular defects on the lateral trochlea of the distal femur of eight normal horses. The contralateral femoropatellar (knee) joint served as a control in which the defect was left empty. Synovial fluid from the femoropatellar joints was sampled on days 0, 4, 7, 30, 120, and 240 postoperatively...
Morphological effects of arthroscopic partial synovectomy in horses. Gross and microscopic effects of arthroscopic partial synovectomy on synovium and articular cartilage of middle carpal joints were studied in 15 horses. A 7-mm diameter motorized synovial resector was inserted into each middle carpal joint and arthroscopic partial synovectomy and lavage or arthroscopic lavage alone was performed. Study periods were 0 (three horses), 16 (three horses), and 30 days (six horses). No gross evidence of degenerative joint disease was observed at day 16 or 30. At 30 days, resected areas lacked villi and there was deposition of fibrin on the synovial surface with vary...
An investigation of the proteoglycan metabolism of mature equine articular cartilage and its regulation by interleukin-1. The effect of human recombinant interleukin-1 beta (rhIL-1 beta) on proteoglycan metabolism was investigated in cultures of full thickness explants of articular cartilage from horses 3-21 years of age. Proteoglycan synthesis was inhibited at all ages but no alteration in the hydrodynamic size or electrophoretic heterogeneity was observed in proteoglycan isolated from rhIL-1 beta stimulated cartilage. The sulphation pattern of the newly synthesised proteoglycan molecules was, however, significantly affected by the presence of the peptide regulatory factor. Interleukin-1 had no effect on the rat...
Structure of equine type I and type II collagens. Collagen type I was purified from equine skin and flexor tendon, and type II collagen was purified from equine articular cartilage. The proteoglycans in these tissues were extracted, using guanidine HCl; the collagens were solubilized, using pepsin digestion, then were selectively precipitated with NaCl. Gel electrophoresis indicated that the precipitates contained only type I or type II collagen. Amino acid analysis indicated that collagen constituted > 97% of the total protein in the precipitates. Hydroxylation of proline was 42.0 +/- 0.6% (mean +/- SEM) in alpha 1(I) and alpha 2(I), and was...
Quantitative analysis of cyanogen bromide-cleaved peptides for the assessment of type I: type II collagen ratios in equine articular repair tissue. Cyanogen bromide was used to solubilise and specifically fragment purified equine Type I and II collagen and equine articular surface repair tissue. The resultant peptides were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and quantified by densitometric scanning. Measurement of the relative amounts of the peptides alpha 2(I) CB3, 5 and alpha 1(II)CB10 provided an accurate method of establishing the ratio of Type I to Type II collagen in mixtures of purified equine collagens. The method was sensitive to 6% Type II collagen when the band areas were corrected for peptid...
Influence of intra-articular sodium hyaluronate and polysulphated glycosaminoglycans on the biochemical composition of equine articular surface repair tissue. The influence of repeated intra-articular injections of sodium hyaluronate and polysulphated glycosaminoglycan on the repair of full-thickness osteochondral defects was examined in the midcarpal joints of ponies. The study showed no significant difference between treated and control groups with regard to total collagen content, uronic acid content or the relative proportions of Type I and Type II collagen in the repair tissue, indicating that the drugs did not affect the biochemical composition of the repair tissue 11 weeks after defect induction.
Effect of interleukin 1 on articular cartilage from young and aged horses and comparison with metabolism of osteoarthritic cartilage. The effect of interleukin 1 (IL-1) on equine articular cartilage was investigated, using a cartilage explant culture system. Measurement of [35S]O4 incorporation revealed synthesis of matrix proteoglycan by cartilage to be decreased 45, 59.7, and 37.5% after 1, 3, and 5 days, respectively, in culture in the presence of 5 U of IL-1/ml. There was no change in proteoglycan degradation as determined by measurement of [35S]O4 release into the culture medium. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cartilage-conditioned medium indicated that exposure of cartilage to IL-1 caused ...
Cross-validation of cyanogen bromide-peptide ratios to measure the proportion of type II collagen in pepsin digests of equine articular cartilage, meniscus, and cartilage repair tissue. Collagen type I and type II were purified from equine flexor tendon and articular cartilage, respectively. Equal amounts of these collagens were cleaved with cyanogen bromide, and 11 mixtures containing increasing proportions of type II collagen were separated in seven identical sodium dodecyl sulfate-polyacrylamide gels. The density of bands was measured in wet gels and the peak areas were used to form six ratios of peptide bands that had polynomial relationships with the known proportions of type I and type II collagen in the mixtures. Calibration curves for determining the proportion of typ...
Energy metabolism, replicative ability, intracellular calcium concentration, and ionic channels of horse articular chondrocytes. Some aspects of the physiology of chondrocytes from horse articular cartilage were studied, since this animal model can be helpful in understanding arthritic processes. The replicative ability of articular chondrocytes, measured by the incorporation of [3H]thymidine, and their capacity of proteoglycan production, evaluated from the incorporation of [35S] sulfate, are very low. In addition, these cells do not differentiate in vitro as shown by the constant specific activity of alkaline phosphatase measured at different times in culture. Two types of potassium channels were identified by patch c...
Effects of exercise and polysulfated glycosaminoglycan on repair of articular cartilage defects in the equine carpus. Our aim was to determine if mild to moderate postoperative exercise and intra-articular polysulfated glycosaminoglycan result in improved repair of large, experimentally induced osteochondral defects in a weight-bearing surface of equine joints. Arthroscopic debridement was used to produce full-thickness defects in a weight-bearing area of the radial carpal bones in 18 ponies. The ponies were randomly assigned to two groups balanced for age: nine animals in the exercise and nine in the no exercise group. Six ponies in each group were medicated weekly for 5 weeks with an intra-articular injecti...
Effect of intramuscularly administered polysulfated glycosaminoglycan on articular cartilage from equine joints injected with methylprednisolone acetate. Intra-articularly administered, long-acting corticosteroids are a beneficial treatment for many equine joint disorders because they alleviate inflammation and signs of pain, but they also exert detrimental effects on the biochemical composition and morphologic features of articular cartilage. Chondroprotective drugs have been shown to mitigate some of the deleterious effects of intra-articularly administered corticosteroids on articular cartilage of laboratory animals. Twenty-one ponies were assigned at random to receive 1 of 3 treatments in the right middle carpal joint. Group-1 ponies (n = 8...
Keratan sulfate as a marker of articular cartilage catabolism and joint treatment in ponies. Keratan sulfate (KS) is a glycosaminoglycan, distribution of which is confined mostly to hyaline cartilage. As such, it is a putative marker of hyaline cartilage catabolism. In experiment 1, a focal osteochondral defect was made arthroscopically in 1 radial carpal bone of 2 ponies, and in 2 other ponies, chymopapain was injected into the radiocarpal joint to induce cartilage catabolism. Sequential and concurrent plasma and synovial fluid concentrations of KS were measured, up to 13 months after induction of cartilage injury, to determine whether changes in KS concentrations reflected cartilage...
Effect of polysulfated glycosaminoglycan on osteoarthritic equine articular cartilage in explant culture. Middle carpal cartilage explants from 4 horses with mild osteoarthritis involving that joint were maintained in tissue culture to test the effects of a polysulfated glycosaminoglycan (PSGAG) on proteoglycan synthesis and degradation. Cultures were exposed to 0.025 or 25 mg of PSGAG/ml for 48 hours, after which the medium was replaced with medium containing similar doses of PSGAG and 35S. Subsequently, the sulfated proteoglycan content of the medium and extracts of the explants was measured. Gel filtration chromatography was used to estimate the size and to purify the principal, large proteogly...
The incidence and severity of intercarpal ligament damage in the equine carpus. The arthroscopic findings in 104 intercarpal joints in 76 horses were reviewed to determine the incidence and severity of changes in the medial intercarpal ligament. Damage to the intercarpal ligament was observed in 43 joints in 35 horses, ranging from mild fraying of the edges of the ligament to complete disruption of all fibres. This represented an incidence of 41% of joints being affected. In 9 joints examined arthroscopically primarily as a further diagnostic procedure, ligament damage was evident in all cases. In horses undergoing arthroscopic surgery primarily for the treatment of osteo...
Effects of short-term cast immobilization on equine articular cartilage. Hexosamine concentration (an index of proteoglycan content), DNA content (an index of cellularity), and [35S]sulfate incorporation (an index of proteoglycan synthesis) of articular cartilage were measured in biopsy specimens from medial proximal sesamoid bone, medial condyle of the third metacarpal bone, and proximal dorsal rim of the proximal phalanx in both metacarpophalangeal joints of 6 adult horses. One limb was then placed in a fiberglass cast that extended down from the proximal portion of the metacarpus and enclosed the hoof; the other limb was not casted. After 30 days of stall confin...