Metabolic responses of rabbit corneas to normoxic and hypoxic conditions in the Ex Vivo Eye Irritation Test: An alternative to animal experimentation

Abstract

The cornea relies on oxygen for its physiological function and therefore for proper vision. Hypoxia induces significant metabolic and structural changes in in vivo corneal models, which underscore the importance of oxygenation in maintaining corneal function and transparency. This study investigates the impact of hypoxia on corneal metabolism using the live-animal-free Ex Vivo Eye Irritation Test (EVEIT) system. New Zealand white rabbit corneas, sourced from the slaughter industry, were incubated in an EVEIT bioreactor for 5 h under normoxic (20-21% oxygen) or hypoxic conditions (5-7% oxygen induced by argon). Macroscopic assessment and Optical Coherence Tomography (OCT) analyzed corneal transparency and central thickness respectively. The metabolic activity was assessed by quantifying lactate concentrations in both the culture medium within the bioreactor and the corneal tissue, employing photometric techniques for measurement. Significant lactate accumulation was observed in corneas under hypoxic conditions, accompanied by increased corneal thickness compared to normoxic conditions. These corneal metabolic changes observed under short-term hypoxic conditions in our ex vivo live-animal-free EVEIT system align closely with those previously recorded in vivo. Considering that the EVEIT system is consistent with in vivo models and that corneal metabolic changes may contribute to various corneal pathologies and dystrophies, EVEIT presents a promising tool and a viable alternative to animal experimentation in corneal ophthalmologic research.

Keywords: Animal free; Cornea; Edema; Hypoxia; Lactate; Organotypic culture; Rabbit.