Choroidal neovascularization (CNV) is a serious complicationof age-related macular degeneration (AMD). Little is known about the role of epigenetics in the pathogenesis of CNV. The aim of current study wasto examine whether thehistone deacetylase inhibitor, trichostatin A (TSA), regulates angiogenic functions of the retinal pigment epithelial (RPE) in vitro and experimental laser induced CNV invivo.

Cultured early passage human fetal RPE cells were used to evaluate effects of TSA. The proliferation of RPE cells was tested using MTT assaywhile cell cycle analysis was evaluated by flow cytometry. RPE cell migrationwas examined using a modified Boyden chamber assay. The expression of VEGF, PEDF, Flk-1, HIF-1a, PPAR-gamma, and caspase 3 in RPE cells was examined by Western blot. Laser-inducedCNV in C57/Bl6 mice receiving intraperitoneal injections ofeither phosphate-buffered saline or 20 mg/kg of TSA every 2days for 14 days was studied by fluorescein angiography, histology, isolectin B4 staining of the CNV lesions and CNV volumes.

Our results showed that a dose-dependent inhibition of proliferation in RPEcells was obtained by TSA treatment; specifically, it halted cell cycle progression at G1phase. TSA treatment resulted in activation of caspase3 at higher doses. TSA significantly down-regulated the expression of VEGF and VEGF receptor 2, and up-regulated the anti-angiogenic and neuro-protective factor PEDF. The anti-proliferative transcription factor, PPAR-gamma, was up-regulated by TSA. Most significantly, TSA attenuated laser-inducedCNV formation in mice, as seen by the reduced leakage in fluoresceinangiography, smaller lesion sizes in histological analysis,and decreased CNV volumes after isolectin B4 staining.

Our results suggest that TSA inhibits angiogenesis by down-regulating VEGF and its signaling and up-regulating the anti-angiogenic factor PEDF. Epigenetics may play a critical role in the regulation of angiogenesis and TSA or other histone deacetylase inhibitis could be a potential therapeutic candidate for the treatment of CNV.