Endochondral ossification

The endochondral ossification, the process responsible for generating most of the skeleton, requires a cartilage intermediate before forming bone. This chapter discusses the major cellular events of endochondral ossification: chondrogenesis, chondrocyte hypertrophy, and osteoblast differentiation, as well as important molecular mediators governing each of these processes. Calcification and ossification of the endochondral skeleton begins with chondrocyte hypertrophy. During this process, columnar chondrocytes located at the center of growing cartilage rudiments, also known as prehypertrophic and hypertrophic chondrocytes, undergo further differentiation after exiting the cell cycle. Osteoblasts are responsible for producing and secreting a combination of extracellular proteins that comprise the bone matrix. The chapter highlights critical murine studies using sophisticated genetic approaches to determine the functions for many of the transcriptional regulators and signaling molecules important in coordinating proper development of the endochondral skeleton.