© Borgis - Postępy Nauk Medycznych 3/2015, s. 186-192
*Beata Bergler-Czop
Starzenie – co nowego?
Aging – what’s new?
School of Medicine in Katowice, Medical University of Silesia in Katowice, Department of Dermatology
Head of Department: prof. Ligia Brzezińska-Wcisło, MD, PhD
Streszczenie
Starzenie się skóry jest naturalnym procesem polegającym na zmniejszeniu biologicznej aktywności komórek organizmu, spowolnieniu procesów regeneracyjnych i utracie zdolności adaptacyjnych ustroju. Decydującą rolę odgrywają tu czynniki genetyczne oraz współdziałające z nimi czynniki zewnętrzne, takie jak: promieniowanie UV, skażenie środowiska, palenie papierosów, niewłaściwa pielęgnacja i czynniki wewnętrzne, związane z zaburzeniami regulacji hormonalnej, nieprawidłowym odżywianiem i niedoborami witamin. Starzenie się skóry możemy podzielić na: wewnątrz- i zewnątrzpochodne.
Część z tych zmian można wyeliminować, części zapobiegać, ale niestety wraz z upływem czasu pojawiają się charakterystyczne odznaki starzenia, takie jak: nadmiar skóry powiek górnych, „kurze łapki” w bocznych kątach oka, wyraźnie zaznaczone fałdy nosowo-wargowe, poprzeczne zmarszczki czoła i zmarszczki marsowe, opadanie końca nosa; mniej wyraźnie zaznaczona linia żuchwy; zmarszczki szyi; widoczne poziome pasma mięśnia szerokiego szyi; opadanie bocznych części policzków.
Do substancji, które skutecznie przeciwdziałają procesowi starzenia się skóry, zaliczamy: witaminę A i jej pochodne, filtry ochronne UVA i UVB, hydroksykwasy (w szczególności kwas glikolowy z uwagi na jego najmniejszą cząsteczkę), przeciwutleniacze (antyoksydanty), substancje hormonopodobne, a także kwas hialuronowy. Nieinwazyjne (niechirurgiczne) programy odmładzające obejmują m.in.: powierzchniowe peelingi chemiczne, retinoidy miejscowe, toksynę botulinową, wypełnienia, wolumetrię, nici, mezoterapię, Roll-Cit, mikrodermabrazję, laseroterapię i wiele innych.
Summary
Skin aging is a natural process, which consists in reducing the biological activity of body’s cells, slowing down regenerative processes and loss of adaptability. The decisive role is played by genetic factors and associated with them external factors, such as: UV radiation, environmental pollution, smoking, improper care and internal factors connected with hormonal regulation disorders, poor nutrition and vitamin deficiencies. We can distinguish endogenous and exogenous skin aging.
Some of these changes can be eliminated and prevented, but unfortunately together with the passage of time, there are distinctive symptoms of aging, such as: an excess of the skin on upper eyelids, „crow’s feet” in side corners of the eye, clearly marked nasolabial folds, transverse forehead creases and frown lines, prolapse of the nose’s tip, less clearly marked line of the mandible, neck wrinkles, visible horizontal bands of platysma, prolapse of side parts of cheeks, thinning of the skin and subcutaneous tissue atrophy contributing to clear wrinkles and skin laxity and much more. Substances, which effectively prevent aging of the skin, include: vitamin A and its derivatives, UVA and UVB protective filters, hydroxyl acids (especially glycolic acid, because of its smallest molecule), antioxidants, hormone-substances and hyaluronic acid. Non-invasive (non-surgical) rejuvenating programs include: superficial chemical peelings, local retinoids, botulinum toxin, filling, volumetry, threads, mesotherapy, rollcit, microdermabrasion, lasers and much more.
Introduction
Skin aging is a natural process, which consists in reducing the biological activity of body’s cells, slowing down regenerative processes and loss of adaptability. The decisive role is played by genetic factors and associated with them external factors, such as: UV radiation, environmental pollution, smoking, improper care and internal factors connected with hormonal regulation disorders, poor nutrition and vitamin deficiencies. We can distinguish endogenous and exogenous skin aging (1-3).
Aging in the area of epidermis
Around living layers of the epidermis, we can observe an atrophy, which is caused by a decrease in the ability of proliferation of keratinocytes. Stratum corneum is more and more thick. The „turnover” can be prolonged even twice. Simultaneously, the number of melanocytes, which group themselves and create lentigines or disappear from certain places causing colored spots, decreases. The number of Langerhans cells is reduced by 50%. There is also a decrease in the secretion of sebum what dries the skin. It contributes to changes of the hydro-lipid composition, and consequently to change the pH of the skin. It becomes more acid, and this means that the epidermis is less resistant to adverse effects of external environment and microorganisms. Moreover, the decrease in sebum secretion causes the enlargement of glands, which favors the formation of sebaceous adenoma. The sensitivity to exogenous substances, i.e. soaps, detergents and UV radiation, increases. It causes the reduction of the skin’s ability to slow down TEWL. Synthesis of vitamin D3 is also reduced (1, 4, 5).
Aging in the area of dermal-epidermal junction
The dermal-epidermal junction flattens. Adhesion of the skin to dermis is also reduced (1, 4, 5).
Aging of the skin within the dermis
Within the dermis, there is a decrease in the number and size of fibroblasts. Consumption of oxygen decreases and there is a reduction of intracellular ATP. This causes deterioration in the ability of protein synthesis with a significant reduction in the ability of passage into interior of cells. It causes the reduction in the number of macrophages, and the loss of hyaluronic acid and dermatan sulfate. Water-binding capacity is weaken by the proteoglycan gel.
Elastin fibers disappear in the papillary layer of the skin, but they become hypertrophied in a reticular layer what leads to the formation of senile elastosis. There is a reduction in the synthesis of collagen and proteoglycans and to impair of angiogenesis, that is, the formation of new blood vessels what results in the formation of wrinkles and furrows, decreased flexibility and increased sensitivity of the skin (1, 6).
Aging of the skin appendages
There is a decrease in sweat glands what reduces the sweat secretion. Nails, just like the skin, are subject to aging. Their recovery process slows down, the plate becomes thickened, there are longitudinal furrows, a nail becomes more brittle. The deterioration of the nail’s condition is affected by many factors, among other, drying chemical agents, radiation, etc. (1, 7).
Endogenous factors affect the endogenous skin aging. Aging is a genetically determined process, which causes a decrease of skin’s flexibility. It becomes dry and thinner, but remains smooth. During this process, we can observe atrophic lesions, i.e. thinning of the epidermis, flaccidity, mimic wrinkles. There are two theories that explain changes in cells, tissues and organs of an aging body. The first is so-called programming theory, which says that so-called gerontogenes are responsible for aging. On the other hand, disorders of cell renewal are responsible for the endogenous aging. Somatic cells have a limited ability to divide. This is so-called Hayflick number or cellular aging. It has been proved that the combination of senescent cells with young cells evokes in these young ells degenerative symptoms. This means that gerontogenes work dominantly. Cell regeneration disorder occurs by the inhibition of cell division, influence of genes on the connective tissue metabolism, e.g. degradation of collagen, apoptosis disorders. The second theory is a „stochastic” theory, which assumes that the aging of cells is associated with biochemical abnormalities, causing their dysfunction (1, 7).
The most important biochemical disorders include:
– excessive formation of oxygen radicals, which damage proteins and DNA,
– amino-acid racemization,
– non-enzymatic glycosylation.
As a result of these molecular and cellular disorders, there are changes in the function of tissues and organs, including the skin. It leads to abnormal response to external stimuli, epidermal barrier dysfunction, as well as disorders of immunological reactions and production of sweat and sebum. There is a decrease of mechanical protection of the skin, reduction in the production of vitamin D3, as well as the thermoregulation disorder. One of the endogenous factors affecting the skin aging process is hormones. The fact that estrogens and androgens deficiency results in degradation of collagen, dryness, loss of elasticity, loss of epidermis and formation of wrinkles was documented (7-10).
Theories of the endogenous skin aging:
1. Theory of biochemical disturbances in the area of aging skin.
It is assumed that the aging process is connected with a damage of its function due to excess production of free oxygen radicals, which damage proteins and DNA of cells. During the excessive accumulation, an oxidative stress occurs. With age, there is also the racemization process, i.e. changes of D-amino acids form to L-amino acids resulting in changes in the composition of proteins. There is also non-enzymatic glycosylation, which leads to an incorrect cross-linking of collagen fibers and other proteins and causes a reduction in the barrier function of the skin (7).
2. Theory of a limited number of cell divisions – so-called Hayflick theory.
It assumes that the ability of cells to divide is limited and decreases with age. After exceeding the number of cell divisions programmed in the genetic material, this cell dies. There is also a decrease in the activity of telomerase, which is an enzyme responsible for replication of telomeres that during each division are shortened. As a result of this process, the transcription and apoptosis process are precluded, which means the death of particular cell (7, 8).
3. Gene theory.
It assumes that the longest duration of life is a genetically determined characteristic. According to this theory, aging does not depend solely on external factors. Generic material of cells include genes that are responsible for the speed of aging (1, 7).
Menopause and the effects of estrogens on the process of skin aging
Menopause is an absence of menstruation sustained for over a year caused by the ovarian failure. The lack of estrogens effects on the metabolism of skin cells leading to changes in a content of collagen and a decrease in skin flexibility, as well as a decrease in the synthesis of hyaluronic acid and glycosaminoglycan concentration. The effect of this situation is a reduction in hydration, dry skin and a drop of skin tension.
During the menopause, there is a significant influence of estrogens on the skin’s condition. Along with the decrease in their level, there are changes mainly in the form of loss of elasticity, thinning and skin’s density loss (11).
Somatopause
With increasing age, there is also a decline of growth hormone secretion and it is connected with symptoms of aging. The action of this hormone can be easily observed in people, who have the growth hormone deficiency. The skin of these persons is dry, flaccid and thin, due to a reduction of water and collagen in its content. There is also a reduction in the sweat secretion by sweat glands, which have growth hormone receptors. It contributes to a disorder of thermoregulation and degrading the physical capacity. The skin becomes cool especially in distal parts of limbs. Moreover, growth hormone deficiency causes reduction in lean body mass, i.e. bone and muscle atrophy (11).
Impact of free radicals
Free radicals (reactive forms of the oxygen) are produced in our body during metabolic processes, i.e. digestion, blood circulation, energy production. These are molecules with an unpaired electron. Each molecule tends to have on its orbit a pair of electrons. In order to obtain this pair, free radicals collect the electron from cell membranes what initiates a chain reaction. There are more and more of free electrons, which have the potential to damage cells. Damage of cell nucleus’s DNA causes disorders of DNA translation what weakens the ability of cells to self-repair and regeneration and increases the aging process (8, 12).
Exogenous factors affecting the skin aging process
Factors that accelerate the skin aging process are:
– UV radiation,
– cigarette smoking,
– pollution of the external environment.
Ultraviolet radiation is a primary factor responsible for the formation of changes occurring in the skin with age within the area exposed to light. Changes occurring within the facial skin are dependent on environmental factors in 80%. Biological effects, triggered in the skin, depend on the length of radiation, and thus are associated in a greater or lesser extent with the specific UV spectrum. Initially, it was believed that the main role in photo-aging of the skin is played by UVB radiation. Nowadays, it is known that both UVA and UVB radiations induce a number of degenerative changes in the skin, acting like immunosuppressants and have carcinogenic properties (13).
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Piśmiennictwo
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