Sox-9 Is Expressed in Adult Articular Chondrocytes in Vivo and in Vitro, but Is Notcorrelated to the Regulation of Collagen Type Ii

Introduction: Anabolic activity is a crucial activity in articular chondrocytes and its failure is one major reason of osteoarthritic cartilage degeneration. Unclear are the intracellular factors responsible for upand down regulation of the molecules of interest. In this respect, the transcription factor Sox-9, a member of the HMG-domain transcription factor family, elicited much of interest as it is co-expressed with type II collagen during mouse development and is thought to be involved in chondrogenic differentiation. Sox-9 is known to bind directly to a 48bp enhancer element in the COL2 gene (1) and mutations in this binding site lead to a loss of transcriptional activation of the COL2 gene. Thus, Sox-9 might be a top candidate for regulating anabolic activity of gene expression also in adult articular chondrocytes. In the present study, we therefor quantitatively evaluated expression levels of Sox-9 and correlated them with the expression of COL2 in normal and osteoarthritic articular human chondrocytes in vivo as well as interleukin-1ß (Il-1ß) stimulated chondrocytes in vitro. Additionally, we performed immunostaining in order to evaluate the zonal distribution pattern of Sox-9 within the tissue.