SPLICING PATTERNS OF FIBRONECTIN MESSENGER-RNA FROM NORMAL AND OSTEOARTHRITIC HUMAN ARTICULAR-CARTILAGE

Fibronectin, a large extracellular glycoprotein, mediates the interact ion of cells with the extracellular matrix. Heterogeneity in the struc ture of fibronectin is largely due to the alternative splicing of thre e exons (IIIB, IIIA and V) during processing of the fibronectin primar y transcript. Osteoarthritis, a degenerative disease of synovial joint s, is characterized by a progressive loss of the articular cartilage e ventually resulting in pain and loss of joint function. In contrast to the loss of most cartilage matrix proteins accompanying this process, osteoarthritic cartilage contains more fibronectin than disease-free cartilage. We examined the splicing patterns of fibronectin mRNA from adult human articular cartilage of normal and osteoarthritic joints by RNase protection (exon IIIA and exon IIIB) and reversed transcription -polymerase chain reaction (exon V) assays to determine whether or not the increased fibronectin content in osteoarthritic cartilage is also associated with differences in the splicing patterns of these three a lternatively spliced exons. The results revealed no gross differences in splicing of these exons between the fibronectin mRNA isolated from adult human articular normal and osteoarthritic cartilage. Thus altera tions in the structure of cartilage fibronectin do not appear to corre late with the increased level of fibronectin protein associated with o steoarthritis.