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- Author or Editor: Charles L. Malemud x
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Abstract
Objective—To compare articular cartilage from horses with naturally developing osteochondrosis (OC) with normal articular cartilage and healing cartilage obtained from horses with experimentally induced osteochondral fractures.
Sample Population—109 specimens of articular cartilage from 78 horses.
Procedure—Morphologic characteristics, proteoglycan (PG), and type II collagen were analyzed in articular cartilage of OC specimens (group 1), matched healing cartilage obtained 40 days after experimentally induced osteochondral fractures (group 2), and matched normal cartilage from the same sites (group 3).
Results—79 specimens of OC cartilage were obtained from horses. Ex vivo PG synthesis was significantly greater in the femoral cartilage, compared with synthesis in the tibial cartilage, and significantly greater for groups 1 and 2, compared with group 3. For groups 1 and 2, femoral fragments had significantly greater PG content, compared with PG content in tibial fragments. Keratan sulfate content was significantly less in group 3, compared with groups 1 and 2. Cartilage from the OC specimens had loss of structural architecture. The OC tissue bed stained positive for chondroitin sulfate and type II collagen, but the fracture bed did not.
Conclusions and Clinical Relevance—Our analyses could not distinguish articular cartilage from horses with OC and a healing fracture. Both resembled an anabolic, reparative process. Immunohistochemical analysis suggested a chondromyxoid tissue in the OC bed that was morphologically similar to fibrous tissue but phenotypically resembled hyaline cartilage. Thus, tissue in the OC bed may be degenerative cartilage, whereas tissue in the fracture bed may be reparative fibrous callus. (Am J Vet Res 2005;66:1881–1890)
SUMMARY
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 use of Sepharose CL-2B chromatography, composite gel electrophoresis, and/or immunoblot analysis with monoclonal antibody 1C6 directed against the hyaluronic acid-binding region on pg.
There was a significant (P = 0.0002) effect of exercise, but not site, on newly synthesized pg, which was increased in the exercised horses, compared with the nonexercised horses at the end of the 6-week study period. The increase in newly synthesized pg was not reflected in the existing cartilage matrix as there was no significant difference between groups in endogenous pg. However, there was a significant (P = 0.01) effect of site on endogenous pg, with the nest of sites located in the palmar aspect of the radial facet containing a greater concentration of endogenous pg than the nests of sites located on the dorsal aspect of the radial facet or all sites on the intermediate facet. Most newly synthesized pg in both groups consisted of hydrodynamically small pg monomers. However, there was a change in the profile of newly synthesized pg at some sites in the exercised horses to include an early elution peak on Sepharose CL-2B, which may contain aggregating pg. All sites in both groups contained a diverse population of endogenous large and small pg on toluidine blue-stained composite gels that reacted with monoclonal antibody 1C6, indicating the potential to bind to hyaluronic acid.
Abstract
Objective
To compare the biochemical, histochemical, and immunohistochemical profiles of articular cartilage from horses with naturally acquired distal tibial osteochondrosis (OC) with cartilage from a similar location in clinically normal horses.
Animals
9 affected horses (group 1, 16 OC lesions) and 4 control horses (group 2, 8 normal osteochondral specimens).
Procedure
OC specimens were collected during arthroscopic removal of the fragment, and control specimens were collected by aseptic osteotomy. Uronic acid, total protein, total glycosaminoglycan (GAG), chondroitin sulfate (CS), and keratan sulfate (KS) contents were determined. Histomorphologic, histochemical, and immunohistochemical examinations were performed on specimens after snap freezing at −80 C and cryosectioning. Monoclonal antibodies (MAB) 3B3 and 5D4 were applied for location of epitopes of CS and KS, respectively.
Results
OC lesions had significantly lower quantity of uronic acid, total GAG, and CS, compared with normal cartilage. OC cartilage had significantly less intense staining with toluidine blue, along with irregular cellularity and tidemark characteristics, compared with normal cartilage. Monoclonal antibodies 3B3 and 5D4 stained OC cartilage, whereas MAB 5D4 did not stain control cartilage. Additionally, MAB 3B3 and 5D4 stained the fibrous tissue that was found firmly attached to the OC lesion located between the parent distal portion of the tibia and OC fragment.
Conclusion
OC cartilage lesions of the distal intermediate ridge of the tibia in horses are biochemically, histochemically, and immunohistochemically distinct from normal cartilage from the same location. Results may reflect the inability of the chondrocyte of the developing joint to alter matrix components that would allow proper maturation and differentiation into bone. (Am J Vet Res 1997;58:89–98)
