Cartilage begets bone versus endochondral myelopoiesis.

Observations on the cellular events involved in embryonic long-bone formation, ectopic osteogenesis, fracture repair, and the analysis of mesenchymal stem-cell potential provide evidence of the intimate and direct relationship of osteogenesis to angiogenesis and vasculature. The sequence of cellular events is that cartilage is not replaced by bone but, rather, is a target for vascularization and myelopoiesis. With this in mind, it may be necessary to replace the term "endochondral bone formation" with "endochondral myelopoiesis."