Decoding multiscale mechanisms in facial sagging: Impact of soft tissue deformability, growth, and dermal anchoring...

Despite the growing interest in anti-aging products and surgical procedures, the mechanistic links between age-based biomechanical tissue alterations and the emergence of a sagged facial appearance have remained relatively unexplored. In this study, we provide corresponding insights by leveraging accurate in vivo characterization of the nonlinear viscoelastic behavior of cheek cutis and subcutis to inform anatomically accurate computational face models. We report that age-based changes in tissue deformability are location- and layer-specific, measuring stronger softening for the subcutis (2.7×-14.2×) than for the cutis (1.9×). Corresponding experimentally-informed simulations further indicate that biomechanical alterations of the cutis, subcutis, and dermal anchoring structures are necessary conditions toward recapitulating jowl formation, although each is insufficient on its own. We relate this to the mechanical gradients across facial tissues, whereby softening of the stiffer outer layers is required for deeper tissue aging to appreciably influence the facial appearance and significantly activate stretch-based mechanobiological pathways driving skin tension relaxation. We envision these findings to inform the development of biophysically grounded surgical and cosmetic anti-aging strategies specifically targeting individual facial tissue layers.