The mature chick sternum is divisible almost equally into cephalic calcified and caudal cartilagenous regions. Isolation and culture of cells derived from embryonic precursors of these regions has revealed two discrete populations of cells with distinct morphological features and synthetic capabilities. Both cell populations grew well in culture within or upon collagen gels or upon plastic and maintained morphologies similar to those observed in the parent tissue. Polyacrylamide gel electrophoresis of radiolabeled proteins synthesized by the cells in culture demonstrated large differences in the types of collagens synthesized. Both chondrocyte populations synthesized type II and minor cartilage collagens but only chondrocytes isolated from the presumptive calcification region synthesized the previously identified, low molecular weight collagen, termed G collagen. Synthesis of G collagen was stimulated by culture within or upon collagen gels such that it represented an average of 65% of the total collagen synthesized by presumptive calcification region chondrocytes after 7 d of culture within collagen gels. Light and scanning electron microscopy demonstrated that the two chondrocyte types exhibited distinct morphological features and accumulated different extracellular matrices in culture.

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