The Swarm rat
chondrosarcoma (RCS) cell lines derived from a spontaneous
neoplasm in a rat spine several decades ago have provided excellent models of
chondrosarcoma tumor development. In addition the robust chondrocyte phenotype (expression of a large panel of genes identical to that seen in normal rat cartilage) and the ability to generate cell clones have facilitated their extensive use in the identification of chondrocyte
proteins and genes. The clustered regularly interspersed short palindromic repeat (CRISPR) technology employing the
RNA-guided nuclease Cas9 has rapidly dominated the genome engineering field as a unique and powerful gene editing tool. We have generated a stable RCS cell line (RCS Cas9) expressing the nuclease Cas9 that enables the editing of any target gene or
non-coding RNA by simple transfection with a guide
RNA. As proof of principle, stable cell lines with targeted ablation of
aggrecan expression (Acan KO) were generated and characterized. The studies show that stable chondrocyte cell lines with targeted genome editing can be quickly generated from RCS Cas9 cells using this system. The Acan KO cell lines also provided a tool for characterizing the response of chondrocytes to
aggrecan loss and the role of
aggrecan in
chondrosarcoma development. Loss of
aggrecan expression while not affecting the chondrocyte phenotype resulted in a much firmer attachment of cells to their substrate in culture. Large changes in the expression of several genes were observed in response to the absence of the
proteoglycan matrix, including those for several
small leucine rich proteoglycans (SLRPs),
transcription factors and
membrane transporters. Acan KO cells failed to form a substantial
chondrosarcoma when injected subcutaneously in nude mice consistent with previous suggestions that the
glycosaminoglycan-rich matrix surrounding the
chondrosarcoma protects it from destruction by the host immune system. The studies provide new understanding of
aggrecan function and the RCS Cas9 cell line is expected to provide a very valuable tool for the study gene function in chondrocytes.