Abstract
Chondrocyte phenotype has been shown to dedifferentiate during passaged monolayer cultivation. Hence, we have investigated the expression profile of 27 chondrocyteโassociated genes from both osteoarthritic cartilage tissue and healthy passaged human articular chondrocytes by quantitative realโtime PCR. Our results indicate that the gene expression levels of matrix proteins and proteases in chondrocytes from monolayer culture decrease compared with those from cartilage tissue, while monolayer cultured chondrocytes from normal and osteoarthritic cartilage exhibit similar gene expression patterns. However, chondrocytic gene expression profiles were differentially altered at various stages of passage. The expression of the matrix proteins aggrecan, type II collagen, and fibromodulin inversely correlated with increasing passage number, while fibronectin and link protein exhibited a marked increase with passage. The expression of matrix proteinases MMPโ3/9/13 and ADAMTSโ4/5 decreased with passage, whereas proteinase inhibitors TIMPโ2/3 were elevated. The cytokine ILโ1 also showed increased expression with monolayer chondrocyte culture, while IGFโ1 expression levels were diminished. No significant changes in TGFโฮฒ, or the chondrogenic transcription factors Soxโ9, cโfos, or cโjun were observed. Our data indicates that cultured chondrocytes undergo dedifferentiation during monolayer culture, although the gene expression level of transcription factors necessary for chondrogenesis remains unchanged. This data may prove important for the future development of more specific and efficacious cultivation techniques for human articular chondrocyteโbased therapies. ยฉ 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1230โ1237, 2008