Maternal Vertical Transmission Provides a Mitochondrial Basis for ROP Susceptibility

Purpose: The purpose of this study was to link strain-based susceptibility to mitochondria. Methods: Crosses between susceptible and protected strains of mice were analyzed for oxygen-induced retinopathy (OIR). Oxygen consumption and extracellular acidification of retina explants from individual strains were quantified. Expression and protein concentrations of key metabolic proteins were measured. Isotopic based metabolomics was used to measure transformations of glycolytic carbon. Results: A/J mice were protected from OIR compared to C57Bl/6 mice, having a 5-fold reduction in the ratio of vaso-obliteration (P = 1*10-5) and a 20-fold reduction in neovascularization (P = 0.002). Mapping among A/J, Balb/C, and C57Bl/6 mice showed a maternal inheritance pattern of protection that implicated mitochondria. A/J and C57Bl/6 mitochondrial functions showed a reduction in the basal respiration rates of A/J ex vivo retina (P = 4*10-9) and a two-fold reduction in the carboxyethyl pyrrole oxidative stress marker of A/J mice retinas with OIR (P = 0.007) compared with C57Bl/6 mice. Placed in hyperoxia, A/J mice retina demonstrated reduced levels of respiratory proteins, as well as expression of subunit IVi1 of cytochrome c oxidase in comparison to C57Bl/6 (P = 3*10-6). To support the hypothesis that a reduction in oxidative phosphorylation was protective, C57Bl/6 mice were injected with the mitochondrial uncoupler 2,4 dinitrophenylhydrazine (DNP) during the hyperoxia phase of OIR; DNP created reduced levels of vaso-obliteration (P = 1.5*10-5) and neovascularization (P = 8*10-6). Isotopic metabolomics demonstrated that A/J aortic endothelium increased glutamine (Gln) synthesis from glycolytic carbon in comparison to C57Bl/6 with upregulation of Hmox1 expression. Conclusions: Strain-specific susceptibility or protection may involve vertical maternal transmission.