[Age-dependent changes in skin biomechanics, measurements in vitro and in vivo].

Age-dependence of mechanical parameters was studied in vitro in human skin obtained at autopsy and in rat skin. Parameters indicating strength, e.g. ultimate load, tensile strength, modulus of elasticity, and ultimate extension, showed a steep increase during maturation, a maximum at adulthood and a slight but significant decrease during senescence. Parameters indicating viscosity or plasticity studied in hysteresis-, relaxation-, and creep-experiments showed a decrease during the whole life span. Simultaneous studies of biochemical parameters indicated a parallel behavior of strength with the content of insoluble cross-linked collagen and of plasticity with the content of glycosaminoglycans. The in vitro experiments in rats could be confirmed by in vivo studies. Further studies in rats indicated an excellent ability of skin in old rats for complete restoration (restitutio ad integrum) after repeated loading.