Abstract
BackgroundIn osteoarthritis (OA), cartilage matrix is lost despite vigorous chondrocyte anabolism. In this study, we attempted to determine whether altered matrix synthesis is involved in this paradox in disease progression through gene expression analysis and ultrastructural analysis of collagen fibrils within the cartilage matrix.MethodsCartilage tissues were obtained from 29 end-stage OA knees and 11 control knees. First, cDNA microarray analysis was performed and the expression of 9 genes involved in collagen fibrillogenesis was compared between OA and control cartilages. Then their expression was investigated in further detail by a quantitative polymerase chain reaction (qPCR) analysis combined with laser capture microdissection. Finally, collagen fibril formation was compared between OA and control cartilage by transmission electron microscopy.ResultsThe result of the microarray analysis suggested that the expression of type IX and type XI collagens and fibrillogenesis-related small leucine-rich proteoglycans (SLRPs) may be reduced in OA cartilage relative to the type II collagen expression. The qPCR analysis confirmed these results and further indicated that the relative reduction in the minor collagen and SLRP expression may be more obvious in degenerated areas of OA cartilage. An ultrastructural analysis suggested that thicker collagen fibrils may be formed by OA chondrocytes possibly through reduction in the minor collagen and SLRP expression.ConclusionsThis may be the first study to report the possibility of altered collagen fibrillogenesis in OA cartilage. Disturbance in collagen fibril formation may be a previously unidentified mechanism underlying the loss of cartilage matrix in OA.
Highlights
In osteoarthritis (OA), cartilage matrix is lost despite vigorous chondrocyte anabolism
Results quantitative polymerase chain reaction (qPCR) analyses of the cartilage procollagen gene expression in OA and control cartilage samples Since the result of cDNA microarray analysis indicated disturbed procollagen expression in OA cartilage (Additional file 2: Figure S1), we investigated their expression in further detail by qPCR analysis combined with laser capture microdissection (LCM)
The present findings suggest that collagen fibrillogenesis may be significantly altered in OA cartilage through a deficiency in the minor collagens and Small leucine rich proteoglycan (SLRP)
Summary
In osteoarthritis (OA), cartilage matrix is lost despite vigorous chondrocyte anabolism. We attempted to determine whether altered matrix synthesis is involved in this paradox in disease progression through gene expression analysis and ultrastructural analysis of collagen fibrils within the cartilage matrix. Osteoarthritis (OA) is the most prevalent joint disease in developed countries and primarily affects articular cartilage. In OA, the cartilage matrix is lost gradually, eventually devastating the functional joints. In OA, the cartilage matrix is lost gradually despite enhanced matrix synthesis. Collagen forms networks within articular cartilage, which is composed primarily of type II collagen with smaller amounts of type IX and XI collagens [3, 8,9,10]. Type II collagen comprises more than 90% of cartilage collagen, while type IX and XI collagens comprise only
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