Immortalization of human articular chondrocytes for generation of stable, differentiated cell lines.

Immortalized chondrocytes of human origin have been developed to serve as reproducible models for studying chondrocyte function. In this chapter, methods for immortalization of primary human chondrocytes with SV40-TAg, HPV-16 E6/E7, and telomerase by retrovirally mediated transduction and selection for neomycin resistance are described. However, stable integration of an immortalizing gene stabilizes proliferative capacity, but not the differentiated chondrocyte phenotype. Thus, strategies for selection of chondrocyte cell lines, involving the maintenance of high cell density and moderation of cell proliferation, are also described. The methods for immortalization and selection are applicable to the development of chondrocyte cell lines using any immortalizing agent. Although immortalized chondrocytes should not be considered as substitutes for primary chondrocytes, they may be useful tools for evaluating and further validating mechanisms relevant to cartilage biology.