COMPLEXITY OF IL-1-BETA INDUCED GENE-EXPRESSION PATTERN IN HUMAN ARTICULAR CHONDROCYTES

The mRNA fingerprinting technique, differential display reverse transc ription polymerase chain (DDRT-PCR), was used to detect changes in the overall pattern of gene expression in human articular knee chondrocyt es induced by interleulrin-1 beta (IL-1 beta), the prototypical induce r of catabolic responses in degenerate joint diseases. One hundred dif ferent primer combinations generated approximately 10 000 different PC R fragments for IL-1 beta treated, as well as for untreated human chon drocytes, cultivated in alginate beads. This represented 53% of all ex pressed chondrocyte genes as based on statistical considerations. Side by side comparisons of differential display patterns originating from two different donor tissues yielded 44 reproducibly, differentially-d isplayed cDNA fragments, which were subcloned and sequenced. Sequence homology searches revealed sequence identities to the human necrosis f actor alpha (TNF-alpha) and IL-1 regulated gene TSG-6, fibronectin, os teopontin, calnexin, and the DNA repair enzyme ERCC5. The differential expression was confirmed with Northern and quantitative PCR analyses. The known function of these genes and their known IL-1 responsiveness indicate that the employed model system reflects the pleiotropic effe cts of IL-1 on the overall gene expression in human articular chondroc ytes and identifies genes involved in very different biochemical pathw ays. Twenty-seven cDNAs lacked sequence homologies to known genes and may represent novel genes.