LIGHT AND ELECTRON-MICROSCOPIC IN-SITU HYBRIDIZATION OF COLLAGEN TYPE-I AND TYPE-II MESSENGER-RNA IN THE FIBROCARTILAGINOUS TISSUE OF LATE-STAGE OSTEOARTHRITIS

Objective: Biochemical analysis indicates the presence of collagen typ e I in fibrocartilaginous tissue of osteoarthritic cartilage, whereas normal hyaline cartilage contains only collagen type II produced by no rmal chondrocytes. Fibrocartilaginous tissue of late-stage osteoarthri tis also exhibits irregularly shaped type 2b secretory chondrocytes as described in the literature. We have attempted to elucidate the type of cell which produces each type of collagen in late-stage osteoarthri tis. Design: We carried out in-situ hybridization at the light and ele ctron microscopic level on the same tissue embedded in LR-Gold(R) appl ying silver enhancement for gold-coupled anti-DIG antibodies. We corre lated the types of cells with the expression of transcripts for type I and type II collagen. Results: We found that cells resembling type 2b secretory chondrocytes of deep zones of fibrocartilaginous tissue exp ressed collagen type I mRNA and almost no collagen type II mRNA. The a mount of collagen type I mRNA was as high as the amount produced in no rmal human skin fibroblasts. Conclusion: Some of the collagen type I i n osteoarthritic human cartilage of late-stage disease is produced by cells resembling type 2b secretory chondrocytes of the deep zone.