Comparison of Cortical and Cutaneous Vascular Hemodynamic Changes in Hypoxia by Using in Vivo Skull and Skin Optical Clearing Techniques

Abstract

Hypoxia occurs in various pathophysiological conditions. Especially, brain can be seriously affected by the oxygen deficiency. However, challenges exist in optically monitoring cerebral hemodynamics with high resolution. As an easily-detected vessel bed, peripheral skin is a potential target for predicting cerebrovascular hemodynamic changes. However, the similarities and differences between cerebral and cutaneous hemodynamics during hypoxia are still unclear. One of the main reasons is that optical imaging techniques are fundamentally depth/resolution-limited due to high scattering properties of turbid tissue. Fortunately, in vivo tissue optical clearing techniques can efficiently overcome these problems, and avoid the side-effects of surgical windows. In this work, we simultaneously monitor the changes in cortical and cutaneous microvascular blood oxygen and blood flow under the assistance of in vivo skull and skin optical clearing techniques, and quantitatively compared the differences between cerebral and cutaneous arteriovenous functional responses to the hypoxic stimulus. The results indicated that the variation tendency of blood oxygen response might be more similar, and cutaneous vascular blood oxygen response has the potential to serve as an accessible indicator for revealing cerebrovascular dysfunction. Moreover, it provides a feasible approach to realize visualization of in vivo monitoring cerebral and cutaneous microvascular reactivity with minimal invasiveness.