Origin-associated features of chondrocytes in mouse Meckel's cartilage and costal cartilage: an in vitro study.

Using a cell culture method, we histochemically and immunohistochemically investigated whether chondrocytes deriving from different origins, such as Meckel's or costal cartilages, express similar phenotypic characteristics. Chondrocytes isolated enzymatically from Meckel's and costal cartilages of 17-day embryonic mice both actively proliferated and formed cartilage nodules consisting of toluidine blue-positive proteoglycans and type II collagen. Both deposited calcified cartilaginous matrix as revealed by alkaline phosphatase (ALPase) activity and alizarin red staining throughout 3 weeks in culture. Immunostaining for osteopontin (OP), osteocalcin (OC), and osteonectin (ON) revealed that chondrocytes from both cartilages were positive for their proteins, but type I collagen was detected only in cells transforming from Meckel's chondrocytes late in the culture. Electron microscopy demonstrated that although costal and Meckel's chondrocytes had typical chondrocytic features during 2 weeks in culture, Meckel's chondrocytes transformed into osteocytic cells that produced thick, banded type I collagen fibrils. In contrast, costal chondrocytes maintained typical hypertrophic morphology throughout the final stage of culture. The present study suggests that Meckel's chondrocytes derived from neural crest-ectomesenchyme retain osteogenic potential, and differ from costal chondrocytes originating from mesoderm.