Retention of epithelial basal lamina allows isolated mandibular mesenchyme to form bone

The initiation of bone formation in the avian mandible requires that neural crest-derived cells undergo an inductive interaction with mandibular epithelium. To examine the role of the epithelial basal lamina in that interaction, mandibles were separated into their epithelial and mesenchymal components following exposure to the chelating agent, EDTA. Transmission and scanning electron microscopy was used to show that the basal lamina was retained as a continuous layer over the mesenchyme. Osteogenesis was initiated when such EDTA-isolated mesenchyme was grafted to the chorioallantoic membranes of host embryos. In contrast, mesenchyme isolated using trypsin and pancreatin failed to form bone. It is concluded that the property of mandibular epithelium which permits osteogenesis resides within the basal lamina.