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Skin Aging: Difference between revisions
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Skin aging is one of the most studied aspects of aging because it is visible and can affect a person’s appearance, which can have significant social and psychological effects. Aging of the skin can lead to changes in skin texture, color, and elasticity, which can affect how people look and feel about themselves. Furthermore, the skin plays an important role in protecting the body from environmental factors, such as UV radiation and pollution. It also prevents excessive water loss and the entry of toxic substances and pathogens into the environment. Upon aging, the skin’s ability to perform these functions can decrease, which can have negative effects on overall health. | Skin aging is one of the most studied aspects of aging because it is visible and can affect a person’s appearance, which can have significant social and psychological effects. Aging of the skin can lead to changes in skin texture, color, and elasticity, which can affect how people look and feel about themselves. Furthermore, the skin plays an important role in protecting the body from environmental factors, such as UV radiation and pollution. It also prevents excessive water loss and the entry of toxic substances and pathogens into the environment. Upon aging, the skin’s ability to perform these functions can decrease, which can have negative effects on overall health. | ||
As the largest organ of the body exposed to the external environment, the skin endures both intrinsic and extrinsic aging factors with extrinsic aging prompted by environmental impacts and overlaying the effects of temporal aging. Intrinsic aging is a physiological process that results in several phenotypes such as, but not limited to, wrinkling, pigmentation, telangiectasis, and gradual dermal atrophy,{{pmid|2476468}} | As the largest organ of the body exposed to the external environment, the skin endures both intrinsic and extrinsic aging factors with extrinsic aging prompted by environmental impacts and overlaying the effects of temporal aging. Intrinsic aging is a physiological process that results in several phenotypes such as, but not limited to, wrinkling, pigmentation, telangiectasis, and gradual dermal atrophy,{{pmid|2476468}}{{pmid|12518793}}{{pmid|1550366}}{{pmid|8123569}}{{pmid|19059763}}{{pmid|25363020}}{{pmid|34764376}} while extrinsic aging is provoked by exterior environment and behavioral factors such as air pollution, tobacco smoking, inadequate nutrition, and sun exposure, causing wrinkles, elasticity loss, as well as rough-textured appearance.{{pmid|2476468}}{{pmid|12518793}} Particularly, long-term exposure to solar UV radiation is the prime factor of extrinsic skin aging referred to as photoaging.{{pmid|12518793}} | ||
Skin aging is accompanied by phenotypic changes in cutaneous cells along with structural and functional alterations in extracellular matrix components such collagen, elastin and proteoglycans, which are required to afford tensile strength, elasticity, and moisture to the skin.{{pmid|29692196}}{{pmid|27569260}} This can result in the appearance of fine lines and wrinkles, sagging skin, and a loss of facial volume. In addition, skin aging is characterized by a decrease in the level of production of hyaluronic acid, a substance that helps to maintain skin hydration and suppleness. Other intrinsic factors that contribute to skin aging include genetic inheritance, slower cell turnover, and hormonal changes, including estrogen, progesterone, and testosterone decrease, which can affect the skin structure. which can lead to a loss of skin elasticity and changes in skin cell metabolism. Additionally, changes in skin microbiota, the collection of microorganisms that live on our skin, can contribute to skin aging and the development of aging-associated skin diseases.{{pmid|29692196}} | Skin aging is accompanied by phenotypic changes in cutaneous cells along with structural and functional alterations in extracellular matrix components such collagen, elastin and proteoglycans, which are required to afford tensile strength, elasticity, and moisture to the skin.{{pmid|29692196}}{{pmid|27569260}} This can result in the appearance of fine lines and wrinkles, sagging skin, and a loss of facial volume. In addition, skin aging is characterized by a decrease in the level of production of hyaluronic acid, a substance that helps to maintain skin hydration and suppleness. Other intrinsic factors that contribute to skin aging include genetic inheritance, slower cell turnover, and hormonal changes, including estrogen, progesterone, and testosterone decrease, which can affect the skin structure. which can lead to a loss of skin elasticity and changes in skin cell metabolism. Additionally, changes in skin microbiota, the collection of microorganisms that live on our skin, can contribute to skin aging and the development of aging-associated skin diseases.{{pmid|29692196}} | ||
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Macrophages are the most abundant immune cell type in the skin and are vital for skin homeostasis and host defense.{{pmid|34073434}} However, they have also been associated with chronic inflammation upon aging. It has been suggested that age-modified skin macrophages may promote adaptive immunity exacerbation and exhaustion, facilitating the development of proinflammatory pathologies, including skin cancer.{{pmid|34073434}} | Macrophages are the most abundant immune cell type in the skin and are vital for skin homeostasis and host defense.{{pmid|34073434}} However, they have also been associated with chronic inflammation upon aging. It has been suggested that age-modified skin macrophages may promote adaptive immunity exacerbation and exhaustion, facilitating the development of proinflammatory pathologies, including skin cancer.{{pmid|34073434}} | ||
While the intrinsic and extrinsic aging factors are both related to phenotypic changes in dermal cells, the most significant structural changes take place in the extracellular matrix (ECM) of dermis, in which collagens, elastin, and proteoglycans impart tensile strength and hydration. The utmost longevity of these biomolecules, relative to the intracellular proteins, exposes them to accumulated damage, which in turn affects their capability to provide mechanical properties and to manage tissue homeostasis.{{pmid|2022748}} | While the intrinsic and extrinsic aging factors are both related to phenotypic changes in dermal cells, the most significant structural changes take place in the extracellular matrix (ECM) of dermis, in which collagens, elastin, and proteoglycans impart tensile strength and hydration. The utmost longevity of these biomolecules, relative to the intracellular proteins, exposes them to accumulated damage, which in turn affects their capability to provide mechanical properties and to manage tissue homeostasis.{{pmid|2022748}}{{pmid|14632798}}{{pmid|7628459}}{{pmid|11322995}}{{pmid|18175202}} Thus, at variance with the intracellular proteins, the half-lives of which are measured in hours or at most days,{{pmid|7628459}} many ECM proteins exhibit half-lives measured in years. For instance, human skin and cartilage collagens types I and II have half-lives of about 15 and 95 years,{{pmid|10976109}} while the half-lives of elastin fibers is equal to{{pmid|2022748}} or many times longer than average human life.{{pmid|8226106}}{{pmid|849882}} Therefore, in humans, ECM proteins are required to function for long years, during which time they are at risk of accumulating damage via glycation,{{pmid|15036419}} calcium and lipid accumulation,{{pmid|8062142}}{{pmid|4576166}} and alterations of aspartic acid residues.{{pmid|14632798}}{{pmid|12039448}} In turn these events have a profound effect on the mechanical properties of ECM proteins.{{pmid|21612880}} | ||
Various molecular models are proposed to rationalize the molecular basis of skin aging, mostly including the overall recognized aging mechanisms such as cellular senescence, telomere shortening, decrease in cellular DNA repair capacity and point mutations of extranuclear mitochondrial DNA, oxidative stress, chromosomal abnormalities, gene mutations, and chronic inflammation (inflammaging).{{pmid|21612880}} | Various molecular models are proposed to rationalize the molecular basis of skin aging, mostly including the overall recognized aging mechanisms such as cellular senescence, telomere shortening, decrease in cellular DNA repair capacity and point mutations of extranuclear mitochondrial DNA, oxidative stress, chromosomal abnormalities, gene mutations, and chronic inflammation (inflammaging).{{pmid|21612880}} | ||