TGF-beta 1 PATHWAY AND AGE-RELATED MACULAR DEGENERATION

Purpose: To set up a retinal degenerative model in rat that mimics pathologic conditions such as age-related macular degeneration (AMD) using amyloid-beta (Abeta) oligomers, and assess the effect of TGF-beta 1. Furthermore a topical formulation of transforming growth factor 1 (TGF-beta 1) was developed; and TGF-beta 1 ocular pharmacokinetics profile was assessed. Methods: Sprague-Dawley male rats were used. Human Abeta 1-42 oligomers were intravitreally (ITV) injected in the presence or in the absence of recombinant human TGF-beta 1. The apoptotic markers Bax and Bcl-2 were assessed by western blot analysis in retina lysates. TGF-beta1 has been formulated as encapsulated in small unilamellar liposomes(SUV). Ocular bioavailability of TGF-beta 1 was assesed in the vitreous of New Zealand rabbits at different time points (30, 60, 120, 180 and 240 min) after a single administration of eye drops by a commercial ELISA kit. Ocular tolerability was also assessed by a modified Draize s test. Results: Treatment with Abeta oligomers induced a strong increase in Bax protein levels and a significant reduction in Bcl-2 protein. Co-injection of TGF-beta 1 triggered a significant reduction of Bax protein induced by Abeta oligomers. The pharmacokinetics profile of TGF-beta 1 lipid formulation demonstrated remarkable levels of TGFbeta-1 in the posterior segment of the eye. In particular, high levels of TGFbeta-1 were detected in the vitreous after 240 minutes (Tmax) from the topical application of the eye drops. The tested formulation was well tolerated and the score for each parameter was zero at all time of observations. Conclusions: Overall, these data indicate that ITV injection of Abeta1-42 oligomers in rat induced molecular changes associated with apoptosis in rat retina, highlighting a potential pathogenetic role of Abeta oligomers in AMD. Abeta1-42 oligomers damage was counteracted by intreavitreal injection of TGF-beta1. Furthermore, the novel formulation was able to deliver remarkable levels of TGFbeta-1 into the back of the eye. Therefore, this TGFbeta-1 delivery system may be useful in clinical practice to manage ophthalmic conditions such as age-related macular degeneration avoiding invasive intraocular injections.