Type X collagen synthesis by cultured chondrocytes derived from the permanent cartilaginous region of chick embryo sternum.

In the developing chick embryo sternum, type X collagen is synthesized by chondrocytes from the cephalic region (presumptive mineralization zone) but not by chondrocytes from the caudal region (permanent cartilaginous zone) (Gibson et al., 1984, J. Cell Biol. 99, 208-216). To distinguish between two possibilities, the presence of a nonpermissive microenvironment in the permanent cartilage or the intrinsic inability of caudal chondrocytes to become hypertrophic, type X-producing cells, we have isolated chondrocytes from the caudal third of stage 44 chick embryo sterna and grown them in suspension on agarose-coated dishes. We have found that in these conditions chondrocytes from the caudal zone differentiate to hypertrophic chondrocytes and synthesize large amount of type X collagen, as revealed by the electrophoretic pattern of labeled proteins made in vitro and by slot blot analysis of mRNAs with specific cDNA probes.