Embryological craniofacial growth:: Back to the morphogenetic bases of distraction osteogenesis

The flat bones of the prechordal skull arc deposited by crest cells originating from the primordial brain vesicles and migrating ventrally to give rise to the multiple anlages of the cranial vault and face. In each mesenchymal condensation, the skeletogenic stem cells differentiate first into chondroid tissue cells, producing a specific collagenous matrix which mineralizes in a quick centripetal, multifocal and multidirectional manner. In contrast, the perichordal bones of the cranial base, which share their pure mesodermal origin with the axial skeleton, are built on the pattern of slow endochondral ossification. Moreover, the desmocranial bones develop as result of a highly adaptive extrinsic growth, mediated by complex cell-tissue-matrix interactions, which does not exist in the endochondral bones of the skull base and of the postcephalic skeleton. Interestingly, the calcified tissues induced during DOG show a very close morphogenetic and histogenic analogy with those observed during the normal development of the desmocranium. This suggests that DOG seems to generate in the craniofacial mesenchyme the same histogenic cascade that operates in the normal cranio- and dento-facial development.