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Study of Skeletal Development in Horses Sheds Light on OsteochondrosisBy Kentucky Equine Research Staff · July 22, 2011
A report published by the Australian Rural Industries Research and Development Corporation defined osteochondrosis as a significant developmental disorder that affects the joints of young growing horses. Osteochondrosis may have several causes including genetic, biomechanical, and nutritional factors. These causes and the roles they play in the disorder are not clearly understood.
Past research has tended to look at clinically significant samples of osteochondrosis. The very earliest stages of the disease are difficult to detect and thus have not been addressed. An objective of the reported research was to investigate genetic causes of osteochondrosis, examining the lesions before they became clinically apparent. Information gained in this research could help to design management strategies that prevent the condition. Other goals were to identify genes that might play a role in other equine joint disorders, and to find markers that could lead to diagnostic tests that identify foals at risk of developing osteochondrosis.
The project was conducted under an ARC-Linkage Grant with Racing Victoria as an industry partner. Two groups of foals were used, with early osteochondrosis lesions induced in foals of one group by feeding a high-energy diet in the earlier part of the project. Foals in the second group were fed a control diet. In the later part of the project, samples of lesions, normal cartilage, and plasma were taken from four euthanized animals in each group eight weeks after the start of the feeding trial. Seven weeks later, the remaining three horses from each group were euthanized and similar samples were collected. Plasma was collected at the start of the trial and at four, eight, and 12 weeks.
The project identified over 70 genes that were differentially expressed in osteochondrosis lesions compared to normal cartilage. Of these genes, nine were confirmed to be expressed significantly more highly in osteochondrosis lesions compared to unaffected cartilage. None of these genes had previously been associated with osteochondrosis. There was a range of functions within the identified genes including development, as components of bone and cartilage extracellular matrix, in the function of bone-resorbing osteoclast cells, and in cell proliferation and differentiation.
While these findings alone do not contribute enough new information to allow the development of an early diagnostic test for osteochondrosis, it is hoped that this work may aid in the development of such a test. Identifying susceptible individuals could allow management intervention before the onset of clinically apparent disease.
Although it is known that environmental factors, in this case a high-energy diet, can increase the incidence of osteochondrosis factors, the reasons for this are not known, and further study is needed in this area also.
