AIM: To demonstrate the feasibility of mesenchymal stem cell (MSC)-mediated nano drug delivery, which was characterized by the “Trojan horse”-like transport of hypoxia-inducible factor-1α small interfering RNA (HIF-1α siRNA) between MSCs and retinal pigment epithelial cells (RPE) under hypoxia environment. METHODS: Plasmid and lentivirus targeting the human HIF-1α gene were designed and constructed. HIF-1α siRNA was encapsulated into poly(lactic-co-glycolic acid) nanoparticles (PLGA-NPs) through the water-in-oil-in-water (w/o/w) multiple emulsion technique. The effect of PLGA-NPs uptake on the expression of HIF-1α mRNA was tested in RPE cells by real-time quantitative polymerase chain reaction (qPCR) and additional transfected conditions were used as control, including lentivirus group, nude plasmid group and blank PLGA group. MSCs were transfected with the NPs and the transfection efficacy was evaluated by flow cytometry. Transwell co-culture system of transfected MSCs and RPE cells was constructed under hypoxia environment. The effects of MSC-loaded HIF-1α siRNA PLGA-NPs on proliferation, apoptosis, and migration of RPE cells were then evaluated. The effect of transfected MSCs on HIF-1α expression of RPE cells was analyzed by using qPCR at the time points 24h, 3d, and 7d. RESULTS: The average diameter of PLGA-NPs loaded with HIF siRNA was 314.1 nm and the zeta potential was -0.36 mV. The transfection efficiency of PLGA-NPs was 67.3%±5.2% into MSCs by using flow cytometry. Compared with the lentivirus group, the PLGA-NPs loaded with HIF-1α siRNA can effectively reduce the expression of HIF-1α mRNA up to 7d in RPE (0.63±0.05 at 7d, P<0.001). In the Transwell co-culture system of transfected MSCs and RPE, the abilities of proliferation (2.34±0.17, 2.40±0.28, 2.47±0.24 at 48h, F=0.23, P=0.80), apoptosis (14.83%±2.43%, 12.94%±2.19%, 12.39%±3.21%; F=0.70, P=0.53) and migration (124.5±7.78, 119.5±5.32, 130±9.89, F=1.33, P=0.33) of the RPE cells had no differences between MSC-loaded HIF-1α siRNA PLGA-NPs and other groups. The inhibition of PLGA on the HIF-1α mRNA expression in RPE cells could continue until the 7th day, the level of HIF-1α mRNA was lower than that of other groups (F=171.98, P<0.001). CONCLUSION: The delivery of PLGA-NPs loaded with HIF-1α siRNA carried by MSCs is found to be beneficial temporally for HIF-1α mRNA inhibition in RPE cells under hypoxia environment. The MSC-based bio-mimetic delivery of HIF-1α siRNA nanoparticles is a potential method for therapy against choroidal neovascularization.