Comparison of proteoglycan and collagen in articular cartilage of horses with naturally developing osteochondrosis and healing osteochondral fragments of experimentally induced fractures.
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.


METHODS
109 specimens of articular cartilage from 78 horses.


METHODS
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
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.
Bertone
Alicia L
AL
Comparative Orthopedic Research Laboratories, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus 43210, USA.
Bramlage
Lawrence R
LR
McIlwraith
C Wayne
CW
Malemud
Charles J
CJ
Malemud
Charles L
CL
D000818:Animals; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D024043:Collagen Type II / Q000378:metabolism*; D005260:Female; D005269:Femur / Q000473:pathology; D017102:Fracture Healing / Q000502:physiology; D006734:Horse Diseases / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D006736:Horses; D007150:Immunohistochemistry / Q000662:veterinary; D066298:In Vitro Techniques; D008297:Male; D010007:Osteochondritis / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D011509:Proteoglycans / Q000378:metabolism*; D011859:Radiography; D013977:Tibia / Q000473:pathology
D024043:Collagen Type II; D011509:Proteoglycans