Cellular responses of embryonic hyaline cartilage to experimental woundingin vitro

It is well established that the reparative potential of many tissues is gre atest during embryonic development. Despite the extensive literature docume nting repair in nonembryonic cartilage models, there is no comparable wealt h of experience relating to embryonic cartilage repair. With the embryonic chick sternum as a model of hyaline cartilage, this paper accounts cellular responses and alterations in extracellular matrix composition in response to experimental wounding in vitro. Creation of an experimental lesion induc ed a rapid (<20 minutes) apoptotic response in chondrocytes adjacent to the lesion edge; the presence of perichondrium delayed this response. Alterati ons in the extracellular matrix included immediate mechanical damage to typ e-II collagen fibrils and an increase in the expression of chondroitin-il s ulphate next to the lesion. Creation of the lesion induced an increased pro liferative response in chondrocytes behind the zone of apoptosis and the ex pression of alpha 5 and alpha 6 integrin subunits.