Differential expression of hepatocyte growth factor and its receptor, c-Met in the rat retina during development.

Hepatocyte growth factor (HGF) is a pleiotrophic factor with mitogenic, motogenic, and morphogenic activities. Recent evidence has suggested that HGF plays an important role in the development and maintenance of the nervous system. In this study, we examined spatial and temporal expression of HGF and its receptor, c-Met, during retinal development at RNA or protein levels. Competitive RT-PCR revealed that HGF and c-met mRNA expressions were up-regulated during the development and sustained at high levels in adulthood. By immunohistochemical analysis, we demonstrated that c-Met-immunoreactivity (IR) was present in the major classes of retinal neurons after their differentiation. In the adult, c-Met-IR was predominantly present in the photoreceptors. In contrast, HGF-IR was observed from P7 and thereafter in ganglion cells and the inner nuclear layer, but not in other layers. Differential or co-localization of HGF and c-Met indicates the autocrine or paracrine action of HGF depending on the cell types and developmental stages. Moreover, dynamic regulation of HGF and c-Met implicates their multiple roles in the development, maintenance and modification of retinal system.