Two-photon phosphorescence lifetime microscopy of retinal capillary plexus oxygenation in mice.

Ikbal Sencan ,Tatiana V Esipova ,Buyin Fu,Mahnaz Shahidi,Sergei A Vinogradov ,David A Boas ,Mohammad A Yaseen ,Sava Sakadžić

doi:10.1117/1.jbo.23.12.126501

Abstract

Impaired oxygen delivery and/or consumption in the retinal tissue underlies the pathophysiology of many retinal diseases. However, the essential tools for measuring oxygen concentration in retinal capillaries and studying oxygen transport to retinal tissue are still lacking. We show that two-photon phosphorescence lifetime microscopy can be used to map absolute partial pressures of oxygen (pO2) in the retinal capillary plexus. Measurements were performed at various retinal depths in anesthetized mice under systemic normoxic and hyperoxic conditions. We used a newly developed two-photon phosphorescent oxygen probe, based on a two-photon absorbing platinum tetraphthalimidoporphyrin, and commercially available optics without correction for optical aberrations of the eye. The transverse and axial distances within the tissue volume were calibrated using a model of the eye's optical system. We believe this is the first demonstration of in vivo depth-resolved imaging of pO2 in retinal capillaries. Application of this method has the potential to advance our understanding of oxygen delivery on the microvascular scale and help elucidate mechanisms underlying various retinal diseases.

Highlights

The retina has complex microvascular architecture and requires ample oxygen delivery to maintain its high metabolic activity.[1]
Recent studies have demonstrated elevation in the inner-retinal pO2 levels in diabetic rats[10] as well as variations in perfusion of different inner-retinal capillary layers in humans affected by diabetic retinopathy.[11,12]
There is a need for development of techniques for depth-resolved pO2 measurements in the retina, which will help in unraveling mechanisms underlying neurovascular coupling and retinal diseases

Summary

Introduction

The retina has complex microvascular architecture and requires ample oxygen delivery to maintain its high metabolic activity.[1] Insufficient blood supply to the retina can cause impaired vision and blindness[2,3] due to common retinal diseases, such as diabetic retinopathy. Light flicker stimulation differentially affects vessel dilation and blood flux at the inner retina capillary layers in rats.[9] Recent studies have demonstrated elevation in the inner-retinal pO2 levels in diabetic rats[10] as well as variations in perfusion of different inner-retinal capillary layers in humans affected by diabetic retinopathy.[11,12] there is a need for development of techniques for depth-resolved pO2 measurements in the retina, which will help in unraveling mechanisms underlying neurovascular coupling and retinal diseases

Methods

Results

Conclusion