Alterations in cartilage type‐ii procollagen and aggrecan contents in synovial fluid in equine osteochondrosis

Abstract

The etiology and pathophysiology of osteochondrosis remain poorly understood because it is difficult to obtain material from lesions in the early stage of this disease and because there is no satisfactory experimental animal model. We wished to determine whether there are changes in articular cartilage turnover in equine osteochondrosis, which closely resembles the human disease, by assaying cartilage matrix molecules in synovial fluids. We used immunoassays that measure a keratan sulfate epitope and the epitope 846 on the cartilage proteoglycan aggrecan and the C-propeptide of cartilage type-II procollagen, which is released following the synthesis of this molecule, to analyse synovial fluids from equine tarsocrural joints with and without osteochondrosis. In young horses with osteochondrosis, there was a significant increase of C-propeptide of type-II procollagen accompanied by a decrease in the 846 and keratan sulfate epitopes. The results identify differential alterations in aggrecan and type-II collagen turnover in the cartilage matrix in young animals with osteochondrosis that may contribute to the pathological degeneration of articular cartilage in this disease.

An Update on the Pathogenesis of Osteochondrosis

“…41,42,104 The study by Henson et al 42 included localization of type VI collagen. Collagens were subsequently studied as a group 113 and in terms of individual types, including type II, 61,62,103 type I, 103 and type X. 103 The studies did not result in a unified hypothesis for how disease of a particular type of collagen would lead to osteochondrosis but rather revolved around whether collagen changes were the cause of 62,103,113 or represented compensation for 42,103 inferior quality cartilage that would not withstand biomechanical load, thus resulting in lesions.…”

Concentration of the CS-846 Epitope in Serum and Synovial Fluid of Horses with Different Grades of Osteochondral Fragments in the Carpal Joints

“…For example, keratan sulfate increases in synovial fluid as a marker of articular cartilage catabolism [17]. The 846 epitope of chondroitin sulfate (CS-846) is another indicator of changes in cartilage glycosaminoglycan content, specifically of aggrecan turnover, and it can be measured in SF by immunoassay [18][19][20][21]. In humans, the release of CS-846, normally present in juvenile articular cartilage but almost completely absent from adult cartilage, is closely correlated with aggrecan synthesis [22].…”

Evaluation of biomarkers following autologous osteochondral transplantation in the equine stifle joint — An experimental study

“…Biomarkers have been employed to date in experimental equine studies (Billinghurst et al, 1997;Frisbie et al, 1999;Laverty et al, 2000;Celeste et al, 2005) and are a promising tool for diagnostic purposes (de Grauw et al, 2006). As the early detection of a joint disease is crucial for the outcome of treatment, the use of biomarkers is a great tool (Van Weeren and Firth, 2008).…”

“…This epitope is only present on the largest aggrecan molecules and was originally identified in human fetal cartilage; its content decreases considerably with cessation of growth (Glant et al, 1986). Degraded aggrecan molecules containing CS846 epitopes released from the matrix into the SF are detectable by immunoassay and indicative of aggrecan turnover (Frisbie et al, 1999;Laverty et al, 2000;Thonar and Manicourt, 2001). This epitope reappears in adult cartilage in joints with osteochondritis dissecans (OCD) and is believed to get elevated in an attempt at repair (Frisbie et al, 1999).…”

“…In OA, CS846 epitope concentrations in cartilage correlate with those in SF. Thus, increases of the CS846 epitope in cartilage and SF suggest an increase in aggrecan synthesis (Laverty et al, 2000).…”