Developmental control of chondrogenesis and osteogenesis.

During vertebrate embryogenesis, bones of the vertebral column, pelvis, and upper and lower limbs, are formed on an initial cartilaginous model. This process, called endochondral ossification, is characterized by a precise series of events such as aggregation and differentiation of mesenchymal cells, and proliferation, hypertrophy and death of chondrocytes. Bone formation initiates in the collar surrounding the hypertrophic cartilage core that is eventually invaded by blood vessels and replaced by bone tissue and bone marrow. Over the last years we have extensively investigated cellular and molecular events leading to cartilage and bone formation. This has been partially accomplished by using a cell culture model developed in our laboratory. In several cases observations have been confirmed or directly made in the developing embryonic bone of normal and genetically modified chick and mouse embryos. In this article we will review our work in this field.