Introduction and review of cartilage and craniofacial growth

This special issue on Cartilage and Craniofacial Growth builds upon more than a century of work on the development of cranial cartilages. Illuminating work has been done in recent years on the cranial cartilages that serve as the template for much endochondral bone of the skull - the chondrocranium. With a focus on elements of the chondrocranium at the tissue level, the papers in this issue emphasize key characteristics of hyaline cartilage to skull morphogenesis. Based on matrix properties and cellular capabilities, cartilage is the ideal skeletal tissue for directional growth, but it also has multiple possible fates beyond its well-established importance as the source for endochondral components of the skull. In this issue, we have provided a greater focus on other fates, including persistence as cartilage or dictating the position of facial bones that are adjacent to cartilage which will disappear; that is, cartilage has both direct and indirect roles in facial morphogenesis. At the tissue level, cartilage is also important in a greatly prolonged temporal manner. Chondrogenic and osteogenic cells have a close relationship prior to differentiation, and endochondral bones have a long window of development time for change beyond the initial formation of a cartilage template.