The immunolocalization and possible role of c-Met (MET, hepatic growth factor receptor) in the developing human fetal mandibular condyle

The c-Met system is involved in skeletogenesis and is expressed in the cartilage of growth plates. However, the localization and role of c-Met during endochondral ossification of developing mandibular condyles or during intramembranous ossification has not yet been elucidated. In this study, c-Met was examined immunohistochemically in the mandibles of human fetuses during weeks 9 and 16 of pregnancy. c-Met was immunolocalised in the whole area of the developing mandible, although to different extents. In the intramembranous bone, mesenchymal cells showed a weak immunopositivity. Osteoprogenitor cells demonstrated a moderate immunopositivity for c-Met, while osteoblasts and osteocytes showed a very strong immunolabelling of c-Met. In the developing mandibular condyles, c-Met immunopositivity increased gradually throughout the proliferative layer towards the pre-hypertrophic cell layer, whereas the cells of the hypertrophic layer were weakly immunopositive. These findings have demonstrated, for the first time, the prominent immunolocalization of c-Met in osteogenic and chondrogenic tissues of developing human mandibles, which indicates possible functions for this receptor during mandibular development.