Immortalization of chondrocytes enables long term in vitro culture; however， the chondrogenic capacity of transformed cells varies， thus highlighting the need to develop a proliferative and tuneable chondrocyte cell line where hypertrophic differentiation can be controlled. In this study the SV40 large T antigen and human telomerase reverse transcriptase were employed to immortalize pooled equine chondrocytes through lentiviral vector mediated transduction either singly or on combination. Transformed chondrocytes proliferated stably over multiple passages， but resulted in significantly lower expression of chondrocyte specific collagen II mRNA (P?