Modulatory effects of CoREST on osteoarthritic chondrocytes differentiation

Abstract

Objective To compare the differential expression of RE-1 silencing transcription factor (REST) compressor (CoREST) in normal and osteoarthritic chondrocytes and investigate the role of CoREST in regulating osteoarthritic chondrocyte differentiation. Methods Osteoarthritic knee cartilage samples were obtained from patients with osteoarthritis undergoing total knee replacement and normal controls.Chonrocytes were isolated and total protein was extracted for Western blotting analysis to compare the differential expression of CoREST between normal controls ( n = 8 ) and osteoarthritic ( n = 8 ) chondrocytes. Primarily cultured normal chondrocytes ( n = 6 ) were treated with specific siRNA to mimic CoREST repression in osteoarthritis. Realtime polymerase chain reaction (PCR) was used to compare the differential expression of chondrocyte phynotypic genes ( collagen Ⅰ, collagen Ⅱ, collagen X and aggrecan) before and after CoREST knock-down. Results CoREST expression level was down-regulated by 69. 5% (P ＜ 0. 01 ) in osteoarthritic chondrocytes in contrast to that of normal controls. In response to CoREST knock-down by 64. 8% (P ＜0. 01 ) in the primarily cultured chondrocytes, the gene expression level of the chondrocyte terminal differentiation marker gene, collagen X was up-regulated by 40. 0% ( P ＜ O. 05 ), whereas the differentiation phenotypic genes, collagen Ⅱ and aggrecan were down-regulated by 71.4% (P ＜0. 01 ) and 57.6% (P ＜0. 01 ), respectively. Conclusion CoREST down-regulation triggered the expression regulation of phenotypic genes towards terminal differentiation, which suggested CoREST is involved in the differentiation status modulation of osteoarthritic chodnrocytes. Key words: Osteoarthritis; Chondrocyte; Differentiation; REST corepressor (CoREST); Phenotype