Dermatology and restorative medicine

The skin is the largest organ of the human body, with a surface area of approximately 2 m2. It is a barrier between the internal and external environment and has multiple specialized functions including thermoregulation, hydration, immunological surveillance, and protection against external chemical, mechanical, and pathogenic insults. Skin aging, like aging of the other organs, is characterized by a progressive loss of functionality and regenerative potential. It is a complex and heterogeneous process affecting the different constituents of the skin, which is influenced by both intrinsic and extrinsic factors. The aging process is proposed to consist of nine concomitant hallmarks including genomic instability, epigenetic alterations, telomere shortening, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. The skin's capacity to efficiently mirror age-associated changes in the entire human body further highlights the importance of elucidating the mechanisms of skin aging. Thus, skin aging is not only a physiologic phenomenon but also a health risk, resulting in increased skin fragility, delayed and impaired wound healing, and increased incidence of infection and skin cancers. As the proportion of the aging population in industrialized countries continues to increase, the dermatological focus gradually shifts towards improving the cosmetic outcomes of skin aging and reducing the morbidity associated with aging skin. In this chapter, we focus on the pathomechanisms and clinical features of skin aging together with prevention and treatment recommendations.