Abstract
Abstract: :
Purpose: In various tissues of the body, increased levels of hepatocyte growth factor (HGF) have been identified in conjunction with neovascular development; however, only a few studies have examined the effects of HGF expression in the eye. This study investigates the initial expression of HGF in a laser-induced animal model of choroidal neovascularization (CNV). Methods: CNV was induced in adult male Brown Norway rats using a previously described laser-trauma model (Criswell, et al.; ARVO 2000). Eyes were enucleated at 6, 12, 18, 24, 36, 48 and 72 hours after laser photocoagulation. Neural retina and RPE/choroidal tissues were harvested and homogenized as individual samples. Soluble proteins were extracted and separated on SDS polyacrylamide gels in the presence and absence of dithiothreitol (DTT). HGF was visualized by Western blot using ECL Plus (Amersham). Results: In neural retina, HGF expression levels were increased at 6 hours after laser treatment. Levels remained relatively unchanged throughout 72 hours. On Western blot only one major band was expressed, with or without DTT. In RPE/choroidal tissues, the expression of HGF remained comparable to that found in untreated controls. Unlike the neural retina, three bands were observed in DTT reduced samples, whereas only one band occurred in the non-DTT samples. Conclusions: Our results suggest that HGF expression is evident following laser trauma to the subretina and thus may be potentially involved in the early stages of neovascular development. Interestingly, the neural retina and RPE/choroidal tissues seem to express different forms of HGF. The single band found in retina is thought to be the precursor, inactive form of HGF. The three bands found in RPE/choroidal tissues are considered to represent the inactive precursor as well as the active α- and ß-subunits of HGF. In the absence of DTT, the precursor and the active heterodimer are not separable on 10% polyacrylamide gels. The significance of these differences is currently under investigation.
Keywords: growth factors/growth factor receptors • choroid: neovascularization • animal model