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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.

Stimuli-responsive gene delivery vectors based on physiologically triggered structure changing have been recently recognized as a new therapeutic agent for their excellent performance in vivo. Herein, we present an intelligent gene delivery system based on the octa-arginine peptides (R8)-conjugated polyamino acid derivatives noted as PPCRC (PVIm-(PAsp-Cystamine-R8)-Cholesteryl), which processed pH responsive, surface charge-switching, intracellular redox-responsive and enhanced nucleus import of gene together. Due to the imidazole group in the PPCRC backbone, the DNA/PPCRC polyplexes not only exhibited the enhanced buffering capacity in the endosome after endocytosis, but also displayed the reversible surface charge from negative to positive with decreasing the pH value form pH 7.4 to pH 6.5–6.8, which would promote the cell membrane binding and cellular uptake. The disulfide bond for R8 peptides conjugation in the polymer side chain could be rapidly cleaved under reductive conditions, facilitating DNA release in the cytoplasm. Subsequently, the DNA would be still associated with the R8 peptides, which would promote the intracellular nucleus import of DNA. The luciferase gene expression level of COS-7 cells transfected by DNA/PPCRC polyplexes was almost 2000 folds higher than cells transfected by DNA/PPCC polyplexes (without R8 peptides modification) in growth-arrested cell model. Nearly 10 folds enhanced gene transfection efficiency was found on human bone mesenchymal stem cells (hBMSCs) using the same strategy, which revealed that this intelligent vector can be also utilized in transfection of non-dividing cells. Intravenous injection of the DNA/PPCRC polyplexes also achieved the effective transfection in subcutaneous tumor model. Taken together, PPCRC vector has great potential for both dividing and non-dividing cells transfection and in vivo gene delivery application.