Abstract
Chondrocytes from Swarm rat chondrosarcoma were successfully maintained in a suspension culture for over 18 months without losing its original phenotypic traits of producing tumor upon transplantation and of synthesizing cartilage-type proteoglycans. The chondrocytes were initially cultured by using a cell-encapsulation technique with alginate gels and were grown in an ordinary Dullbecco's modified Eagle's medium containing fetal bovine serum. The cells thus obtained after 18 months were morphologically indistinguishable from the chondrocytes in situ in the orginal tumor. No fibroblast-like cell was detected in the cultured cell population. When transplanted into rats, they grew at a rate comparable to that of original chondrosarcoma cells. This observation was supported, thought not directly, by measuring the rate of 3H-thymidine incorporation into their DNA fractions, which was also comparable to that of the original tumor cells. Biochemically, the cultured cells were able to synthesize proteoglycans at a similar rate to that by freshly isolated cells from the tumor. The molecular size and subclass of the proteoglycans produced within the cells or secreted to the extracellular medium were the same as those produced by the chondrosarcoma tumor cells and also to those synthesized by normal cartilage. Thus, the present culture system can be used as a suitable model to study the synthesis and assembly of the extracellular matrix in connective tissues, especially, those in cartilage.
