Gene expression profiles of human chondrocytes during passaged monolayer cultivation

Chondrocyte phenotype has been shown to dedifferentiate during passaged monolayer cultivation. Hence, we have investigated the expression profile of 27 chondrocyte-associated genes from both osteoarthritic cartilage tissue and healthy passaged human articular chondrocytes by quantitative real-time 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 MMP-3/9/13 and ADAMTS-4/5 decreased with passage, whereas proteinase inhibitors TIMP-2/3 were elevated. The cytokine IL-1 also showed increased expression with monolayer chondrocyte culture, while IGF-1 expression levels were diminished. No significant changes in TGF-beta, or the chondrogenic transcription factors Sox-9, c-fos, or c-jun 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 chondrocyte-based therapies.