Rat Oxygen-induced Retinopathy (OIR) Model and Intraperitoneal Injections

The rat OIR model used in this study has been described previously.18,19 Within 6 hours of birth, newborn Sprague-Dawley pups (male and female) and dam were placed into an oxygen chamber (Oxycycler, Biospherix, NY, USA) with controlled oxygen concentrations that cycled between 50% and 10% every 24 hours. After 14 days, pups were moved into room air (RA). Each litter had 12 to 14 pups to maintain consistency in measured outcomes in the model. Experiments were repeated in four individual litters.

In a litter, pups were randomly assigned to two groups and treated with intraperitoneal injections of genipin (10 mg/kg, Sigma-Aldrich Corp., St. Louis, MO, USA) dissolved in dimethyl sulfoxide (DMSO) and PBS (1:500) or an equal volume of vehicle (DMSO+PBS) as control beginning at postnatal day 3 (p3) and repeated every other day until p13. For pups in the OIR model, injections were performed at the end of 50% oxygen cycles and before 10% oxygen cycles to avoid interventions during the 10% oxygen cycle.