Abstract
Abstract: :
Purpose: To evaluate and compare the expression patterns of HGF, bFGF and VEGF in choroidal and retinal tissues using the laser–trauma rat model of choroidal neovascularization (CNV). Methods: CNV was induced in Brown Norway rats as described previously (Criswell, et al. IOVS 1999; 40: ARVO Abstract 1222). Neural retinal and RPE/choroidal tissues were harvested at 30, 60, 90, and 120 minutes and at 6, 12, 24, 48 and 72 hours after laser photocoagulation. Expression patterns of HGF, bFGF and VEGF were visualized by Western blot under reduced condition. Results: HGF expression levels in neural retina increased at 30 minutes after laser treatment, peaked around 6 hours, and then stabilized at a slightly lower level through 72 hours. Only one major band (at 67 kDa) was observed. In RPE/choroidal tissues, three distinct bands (at 31, 53, & 67 kDa) were present and maximum expression occurred between 90 and 120 minutes. bFGF was expressed in neural retina as multiple bands from 18 to 34 kDa with minimum variability. However, a low molecular weight isoform (at 12 kDa) was observed only from 90 minutes to 12 hours. In contrast to neural retina, the 12 kDa band was expressed in RPE/choroidal tissues and its level increased from 30 minutes, maximized around 6 hours and maintained a high level through 72 hours. Interestingly, VEGF was not detectable in neural retina and, in RPE/choroidal tissues, only a single band (at 25 kDa) occurred at 72 hours. Conclusions: In the rat CNV laser trauma model, HGF and bFGF were expressed earlier and to a greater extent as compared to VEGF. Activated HGF and cytoplasmic bFGF isoforms were primarily expressed in RPE/choroidal tissues rather than in the neural retina. The data from this model suggests that both HGF and bFGF may play important and possibly interrelated roles following trauma and during initial CNV development, whereas VEGF upregulation may correspond to the time period (48 to 72 hours) when CNV is first observed histologically.
Keywords: choroid: neovascularization • growth factors/growth factor receptors • age–related macular degeneration