Stimulation of the oxygen consumption by photobiomodulation in the chicken embryo chorioallantoic membrane during hypoxia

Abstract

The main objective of this project is to study the effects of photobiomodulation (PBM) on the oxygen consumption in the in vivo chick’s embryo chorioallantoic membrane (CAM) under hypoxia to improve understanding of the mechanisms involved in PBM therapy of various conditions, including strokes and ischemic wounds. Protoporphyrin IX (PPIX), produced endogenously after administration of aminolevulinic acid, was used to probe the oxygen partial pressure (pO 2 ) in the CAM by time-resolved spectroscopy of its delayed fluorescence. This approach enables exploring and optimizing conveniently different radiometric and spectral parameters at play in PBM. Interestingly, since PPIX is produced in the mitochondria, an organelle playing a key role in cell respiration, and then diffuses in different compartments, the pO 2 can be determined in different (sub-) cellular/tissue locations. Our results showed that PBM applied between 6 and 16 minutes (5 mW/cm 2 ) after the beginning of hypoxia with light at 730 or 820 nm sustains the oxygen consumption in the CAM for more than one hour, an effect that is not observed in control eggs. This may explain the positive effects induced by PBM in hypoxic tissues, including those that are subject to ischemia-reperfusion injuries.