Objective To immortalize human articular chondrocytes ( HACs) using gene transfection and to maintain stable phenotype of transformed HACs after induction.Methods HACs were transfected with the retroviral vector pLXSN encoding human papillomavirus 16E7 (HPV16E7), and the transformed clones were sorted and proliferated. Karyotype analysis, clone forming tests and nude mice tumor forming tests were applied to check the characteristics of the transformation. Type II collagen of transformed chondrocytes was inducted with free serum medium (FSM) supplemented with nutridoma-sp and ascorbate.Results Immortalized HACs were isolated with fifty passages achieved. The HPV16E7 transformed cells were confirmed to be benign. Induction of FSM with nutridoma-sp and ascorbate promoted type II collagen of transformed chondrocytes to the high levels of normal chondrocytes.Conclusion HACs transformed with HPV16E7 survive for long periods in vitro, and type Ⅱ collagen can maintain stability after induction. Objective To immortalize human articular chondrocytes (HACs) using gene transfection and to maintain stable phenotype of transformed HACs after induction. Methods HACs were transfected with the retroviral vector pLXSN encoding human papillomavirus 16E7 (HPV16E7), and the transformed clones were sorted and proliferated. Karyotype analysis, clone forming tests and nude mice tumor forming tests were applied to check the characteristics of the transformation. Type II collagen of transformed chondrocytes was inducted with free serum medium (FSM) supplemented with nutridoma-sp and ascorbate. Results of Immortalized HACs were isolated with Fifually passages achieved. The HPV16 E7 transformed cells were confirmed to be benign. Induction of FSM with nutridoma-sp and ascorbate promoted type II collagen of transformed chondrocytes to the high levels of normal chondrocytes. Conlusion HACs transformed with HPV16 E7 survive for long periods in vitro, and type Ⅱ collagen can maintain stability after inductiation on.