Metaplasia of chondrocytes into osteoblasts.

Hypertrophic chondrocytes, commonly considered as terminal cells responsible for apoptotic elimination in endochondral osteogenesis, have the potential to switch their metabolic role and enter osteoblastic differentiation, based on histochemical, immunohistochemical, biochemical and cytological analysis. During endochondral osteogenesis, some osteocytes are derived from hypertrophic chondrocytes. Also non-hypertrophic chondrocytes are able to transform into osteogenic cells, and the bone thus formed is termed "transchondroid bone". In this review a summary and discussion of reports on chondrocyte transdifferentiation is given.