Intravitreal injection of triptolide attenuates subretinal fibrosis in laser-induced murine model.

Abstract Background Choroidal neovascularization (CNV) is a common cause of irreversible blindness in elderly patients in developed countries, and subretinal fibrosis is an advanced stage of CNV. Currently, there is no effective clinical treatment for subretinal fibrosis. Purpose To investigate whether intravitreal injection of triptolide (TP) could attenuate subretinal fibrosis and determine its underlying mechanisms. Methods CNV was induced by laser photocoagulation in C57BL/6J mice. Immediately after laser photocoagulation, 1 μL of free TP (10 μg), TP-nanolip-PEG (TP-loaded PEGylated nanoliposomes containing 10 μg TP), or the same volume of phosphate-buffered saline (PBS) was intravitreally administered to each respective group. Areas and ratios of subretinal fibrosis were calculated seven days after laser injury. Additionally, expression levels of M2 macrophage-related markers, molecules of the transforming growth factor (TGF)-β1/Smad signaling pathway, and markers for epithelial-mesenchymal transition (EMT) and endothelial-to-mesenchymal transition (EndoMT) were detected both in vitro and in vivo. Results The areas of subretinal fibrosis were significantly reduced in both the free TP (10993.87 ± 2416.90 μm2) and TP-nanolip-PEG (7695.32 ± 2121.91 μm2) groups when compared with the PBS group (15971.97 ± 3203.10 μm2) (P Conclusions TP could attenuate subretinal fibrosis by suppressing the polarization of M2 macrophages and TGF-β1 induced EMT/EndoMT. TP-nanolip-PEG enhanced the inhibitory effects of TP on subretinal fibrosis, suggesting its therapeutic potential for CNV-related subretinal fibrosis.