Complexity of IL-1 beta induced gene expression pattern in human articular chondrocytes

The mRNA fingerprinting technique, differential display reverse transcription polymerase chain (DDRT-PCR), was used to detect changes in the overall pattern of gene expression in human articular knee chondrocytes-induced by interleukin-1 beta (IL-1 beta), the prototypical inducer of catabolic responses in degenerate joint diseases. One hundred different primer combinations generated approximately 10,000 different PCR fragments for IL-1 beta treated, as well as for untreated human chondrocytes, cultivated in alginate beads. This represented 53% of all expressed 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-displayed cDNA fragments, which were subcloned and sequenced. Sequence homology searches revealed sequence identities to the human necrosis factor alpha (TNF-alpha) and IL-1 regulated gene TSG-6, fibronectin, osteopontin, 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 effects of IL-1 on the overall gene expression in human articular chondrocytes and identifies genes involved in very different biochemical pathways. Twenty-seven cDNAs lacked sequence homologies to known genes and may represent novel genes.