Induction of original phenotype of human immortalized chondrocytes: a quantitative gene expression analysis.

We previously established a line of immortalized normal human articular chondrocytes, lbpva55, expressing the E6 and E7 transforming genes of the human papilloma virus type 16. With this study we investigated the phenotypic modulation ability of this cell line, cultured in different conditions, with the aim of validating its use for studies on cartilage metabolism and physiology. To this end, we performed a quantitative analysis, using real-time PCR technology, of the expression of the main structural components of the cartilage matrix (collagens I, II and aggrecan), of two transcription factors regulating chondrocyte differentiation (Sox-9 and Egr-1) and of some enzymes involved in matrix turnover (cathepsin B, MMP-1 and MMP-13). Results showed that, under defined conditions, lbpva55 cells were able to re-express the chondrocyte phenotype that was lost in a conventional monolayer condition, as demonstrated by an up-regulation of collagen II, the main marker of hyaline cartilage and Sox-9, a master gene regulator of chondrocytic differentiation. The gene expression profile of our immortalized cells compared with that of normal articular chondrocytes showed that this line could be used as a valid in vitro model for a better understanding of cell molecular mechanisms relevant for the development of new therapeutic approaches in rheumatic diseases and for the cartilage engineering field.