Stable murine chondrogenic cell lines derived from c-fos-induced cartilage tumors

This study describes the detailed characterization of four murine chondrogenic cell lines (wT2-1, wT2-7, wT2-8, and wT2-9) that were isolated from a cartilage tumor induced by the protooncogene c-fos in chimeric mice. All cell lines are clonal and display a fibroblastic morphology with a doubling time of 1-2 days. Northern blot analysis demonstrated that in addition to expressing high levels of exogenous c-fos, all clones express varying levels of the cartilage marker gene type II collagen in addition to type I collagen. The clones also expressed high levels of the AP-1 genes c-jun and fra-1. The doubling times of these clones did not change over a period of 14 months in culture. Most importantly, however, expression of type II collagen was maintained in all cell lines for 8 months in culture, and two cell lines maintained type II collagen expression when analyzed after 14 months. Interestingly, type I collagen expression was lost after long-term culture. Following injection into syngeneic and nude mice, all cell lines formed tumors containing areas with the morphologic appearance of hyaline cartilage, indicating that these cell lines are chondrogenic. Thus, these stable murine chondrogenic cell lines provide a useful tool for studying the transcriptional control of cartilage-specific gene expression, as well as the growth control of chondrogenic cells.