Effects of the existence of nitric oxide and the degradation of extracellular matrix on CD44 mRNA expression in cultured chondrocytes

Abstract

We previously reported that interleukin-1β (IL-1β) promoted CD44 mRNA expression in cultured rabbit articular chondrocytes, together with the reduction of extracellular matrix. It was assumed from this result that the existence of nitric oxide (NO) induced by IL-1β and degradation of the extracellular matrix affects CD44 mRNA expression in the chondrocytes. To confirm this assumption, we first carried out production of NO by IL-1β through quantitative detection of inducible nitric oxide synthase (iNOS) mRNA expression in the chondrocytes and measurement of nitrite plus nitrate in the culture medium. IL-1β evidently promoted NO production in the chondrocytes. A tendency for increased release of chondroitin sulfates (CS), as extracellular matrix, to the culture medium was observed by addition of IL-1β, but release of CS to the culture medium did not increase as the result of addition of S-nitroso-N-acetyl penicillamine (SNAP) as NO donor. We then investigated the effects of SNAP, chondroitinase, and hyaluronidase on CD44 mRNA expression in the cultured chondrocytes. CD44 mRNA expression was increased significantly in chondrocytes cultured with SNAP and chondroitinase but not in chondrocytes cultured with hyaluronidase. These results suggest that the existence of NO and the degradation of CS may be associated with upregulation of CD44 mRNA expression in chondrocytes..