Quantitative volumetric photoacoustic assessment of vasoconstriction by topical corticosteroid application in mice skin.

Topical corticosteroids manage inflammatory skin conditions via their action on the immune system. An effect of application of corticosteroids to the skin is skin blanching caused by peripheral vasoconstriction. This has been used to characterize, in some cases relative potency and also as a way to compare skin penetration. Chromameters have been used to assess skin blanching-the outcome of vasoconstriction caused by topical corticosteroids-but do not directly measure vasoconstriction. Here, we demonstrate quantitative volumetric photoacoustic microscopy (PAM) as a tool for directly assessing the vasoconstriction followed by topical corticosteroid application, noninvasively visualizing skin vasculature without any exogeneous contrast agent. We photoacoustically differentiated the vasoconstrictive ability of four topical corticosteroids in small animals through multiparametric analyses, offering detailed 3D insights into vasoconstrictive mechanisms across different skin depths. Our findings highlight the potential of PAM as a noninvasive tool for measurement of comparative vasoconstriction with potential for clinical, pharmaceutical, and bioequivalence applications.