SummarySkin, the largest organ of the human body, is organized into an elaborate layered structure consisting mainly of the outermost epidermis and the underlying dermis. A subcutaneous adipose-storing hypodermis layer and various appendages such as hair follicles, sweat glands, sebaceous glands, nerves, lymphatics, and blood vessels are also present in the skin. These multiple components of the skin ensure survival by carrying out critical functions such as protection, thermoregulation, excretion, absorption, metabolic functions, sensation, evaporation management, and aesthetics. The study of how these biological functions are performed is critical to our understanding of basic skin biology such as regulation of pigmentation and wound repair.Impairment of any of these functions may lead to pathogenic alterations, including skin cancers. Therefore, the development of genetically controlled and well characterized skin models can have important implications, not only for scientists and physicians, but also for manufacturers, consumers, governing regulatory boards and animal welfare organizations. As cells making up human skin tissue grow within an organized threedimensional (3D) matrix surrounded by neighboring cells, standard monolayer (2D) cell cultures do not recapitulate the physiological architecture of the skin. Several types of human skin recombinants, also called artificial skin, that provide this critical 3D structure have now been reconstructed in vitro. This review contemplates the use of these organotypic skin models in different applications, including substitutes to animal testing.

Skin aging is a complex process that may be caused by factors that are intrinsic and extrinsic to the body. Ultraviolet (UV) radiation represents one of the main sources of skin damage over the years and characterizes a process known as photoaging. Among the changes that affect cutaneous tissue with age, the loss of elastic properties caused by changes in elastin production, increased degradation and/or processing produces a substantial impact on tissue esthetics and health. The occurrence of solar elastosis is one of the main markers of cutaneous photoaging and is characterized by disorganized and non-functional deposition of elastic fibers. The occurrence of UV radiation-induced alternative splicing of the elastin gene, which leads to inadequate synthesis of the proteins required for the correct assembly of elastic fibers, is a potential explanation for this phenomenon. Innovative studies have been fundamental for the elucidation of rarely explored photoaging mechanisms and have enabled the identification of effective therapeutic alternatives such as cosmetic products. This review addresses cutaneous photoaging and the changes that affect elastin in this process.R esum e Le vieillissement de la peau est un processus complexe qui peutêtre caus e par des facteurs intrins eques et extrins eques du corps. Les rayons ultraviolets (UV) repr esentent l'une des principales sources de dommages de la peau au fil des ans et caract erise un processus connu sous le nom de photo-vieillissement. Parmi les changements qui affectent le tissu cutan e avec l'âge, la perte des propri et es elastiques caus ees par des changements dans la production d' elastine, augmentation de la d egradation et / ou le traitement, produit un impact important sur l'esth etique et la sant e des tissus. La survenue d'une elastose solaire est l'un des principaux marqueurs de photo-vieillissement cutan e et se caract erise par un d epôt d esordonn e et non-fonctionnel des fibres elastiques. L'apparition d'un epissage alternatif du g ene de l' elastine induit par le rayonnement UV, ce qui conduit a une synth ese insuffisante des prot eines n ecessaires a l'assemblage correct des fibres elastiques, est une explication possible de ce ph enom ene. Des etudes novatrices ont et e fondamentales pour l' elucidation des m ecanismes de photovieillissement rarement explor es et ont permis l'identification d'alternatives th erapeutiques efficaces, tels que les produits cosm etiques. Cette revue porte sur le photo-vieillissement cutan e et les changements qui affectent l' elastine dans ce processus.

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Human dermal fibroblasts have a potential to adhere to plastic surfaces and differentiate into other cell types. However, for stem cells intended to be used in cosmetics, experiments conducted with contaminated fibroblasts may produce poor or even falsely negative results for the efficacy of the active ingredient or formulation and thus conceal their promising effects as anti-ageing and skin rejuvenation products.

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