Abstract
Oxygen (O(2)) uptake by cells and tissues is a critical indicator of metabolic demand, changes in microenvironment, and pathophysiology. O(2) uptake from the atmosphere accounts for virtually all the O(2) consumption in the avascular cornea; however, a detailed spatiotemporal profile of corneal O(2) uptake (COU) remains undetermined. Here, we used a non-invasive self-referencing optical fiber O(2) sensor-the scanning micro-optrode technique (SMOT)-to report the O(2) partial pressure and flux variations at the ocular surface of rodents and non-human primates. In vivo spatial mapping in mice revealed a distinct COU, characterized by a centripetal gradient with a significantly higher O(2) influx at the limbus and conjunctiva regions than at the center of the cornea. This regional COU profile was reproduced ex vivo in freshly enucleated eyes. The centripetal gradient was conserved across the following species analyzed: mice, rats, and rhesus monkeys. In vivo temporal mapping in mice showed a significant increase in the O(2) flux in the limbus in the evening compared to other times. Altogether, the data unveiled a conserved centripetal COU profile, which may be associated with the limbal epithelial stem cells residing at the intersection of the limbus and conjunctiva. These physiological observations will serve as a useful baseline for comparative studies with contact lens wear, ocular disease, diabetes, etc. Moreover, the sensor may be applied to understand the responses of the cornea and other tissues to various insults, drugs, or changes in the environment.