OBJECTIVE: The physiological and pathogenetic role of microRNAs (miRNAs) in the maintenance of joint homeostasis and in the development of arthritis is recently being elucidated. In this study, we attempted to identify differentially expressed miRNAs in human osteoarthritis (OA) chondrocytes in response to interleukin (IL)-1beta. In addition, simultaneous profiling of miRNA and mRNA expression was performed to get an integrated analysis of miRNA and mRNA expression. METHODS: Monolayer cultured chondrocytes obtained from knee cartilages of OA patients were stimulated with IL-1beta for 4 hours and RNA was isolated. One microgram of total RNA was polyadenylated and converted to cDNA and miRNA microarray was performed. Seven hundred thirty five oligos were used, corresponding to 470 well-annotated human miRNA sequences and 265 potential miRNAs that were identified recently. mRNA microarray was performed simultaneously using the RNA samples that were used for miRNA array. Both sequence and expression information was used to identify regulatory relationship between miRNA and mRNA pairs. RESULTS: Expression profiling of miRNA extracted from IL-1beta treated chondrocytes identified 25 miRNA which showed differential expression. We also identified 7190 mRNAs differentially regulated by IL-1beta treatment. Among the 25 miRNAs differentially regulated, 13 miRNAs had targets searched by MiRANDA scheme. By combining target search and miRNA-mRNA pairing, we could identify 1043 miRNA-mRNA target pairs. MiR-200a was found to be expressed in human OA and normal cartilages, with downregulation in OA lesion cartilages. CONCLUSION: It is suggested that miRNA may play a role in the regulation of cartilage degradation in OA.