Clinical and mechanistic validation of skin gravitational stretchability as a new metric for skin aging assessment

Abstract

Maintaining the skin’s dynamic resilience and youthful compliance is crucial to resisting the visible signs of aging, particularly sagging. We modified a previously reported non-invasive tensile method that simulates the gravitational pull on facial skin for the direct measurement of stretchability under gravity. In this study, we defined the resulting property as skin gravitational stretchability (SGS), a new metric where higher values reflect greater youthful compliance and dynamic resilience against gravitational forces. To contextualize SGS with established biomechanics, we showed significant correlations between SGS and multiple parameters of skin elasticity and recovery, validating its linkage to broader skin elasticity and recovery capabilities. In a clinical evaluation study, a facial cream was proven effective in reducing visible skin sagging. This clinical efficacy was paralleled by a statistically significant, time-dependent increase in SGS, indicating SGS’s effectiveness as an objective biomarker for visible anti-aging assessment, especially for sagging. Subsequent in vitro and ex vivo experiments revealed a multi-level biological response to the facial cream that underpins both the observed clinical efficacy in reducing sagging and the improvement captured by SGS. This response invloved significant upregulation in protein and gene expression for key extracellular matrix components and longevity markers, as well as significant protection against reactive oxygen species (ROS), thereby elucidating the molecular mechanisms underpinning enhanced gravitational resilience. The overall evidence validates SGS for assessing skin mechanical properties, establishing it as an objective, sensitive, and clinically relevant endpoint for studying skin youthful compliance and evaluating anti-aging skincare products.