Biological skin aging: types of skin aging

Chronological aging of the skin

Changes occur in both the epidermis and dermal structures. In particular, a decrease in the number of epidermal cell rows, disturbances in keratinocyte differentiation, an increase in the size of keratinocytes, a change in the ratio of ceramides and other highly specialized skin lipids that provide its barrier properties, including water retention in the skin, are noted. Smoothing is observed in the basement membrane zone. In the dermis, a decrease in the synthesis of collagen and elastin proteins by fibroblasts is recorded with aging. It is from these proteins in the main substance of the dermis that collagen and elastic fibers are synthesized, providing turgor (tone) and elasticity of the skin. In addition, a decrease in the number of important components of the main substance of connective tissue that ensure water retention in the skin (glycosaminoglycans, chondroitin sulfates, etc.), and disturbances in skin microcirculation are recorded.

As a result of the listed morphological changes, clinical signs of chronological aging become noticeable: thinning, dryness, wrinkles (small and deeper) and decreased skin turgor, gravitational ptosis of soft facial tissues. The listed symptoms are the main or obligatory ones; indirect (secondary) ones may also occur. These include swelling and pastosity of the face, especially in the periorbital zone, large-porosity of the skin, erythema of the face, telangiectasias, seborrheic keratoses, xanthelasmas.

The stages of the appearance of signs of skin aging can be represented as follows.

Eye area:

• the appearance at the age of 20-25 of a network of fine superficial wrinkles in the corners of the eyes;
• the appearance by the age of 30-35 of so-called “crow’s feet”, which are radial folds in the corners of the eyes;
• changes in the condition of the skin of the upper and lower eyelids: the appearance of overhanging folds in the area of the upper eyelid, drooping of the leveleyebrows, perceived visually as a narrowing of the eye slits, also saccular formations in the lower eyelid area (not caused by pathology of internal organs); ptosis of the upper and lower eyelids is accompanied by the formation of fatty "hernias" of the eyelids, i.e. bulging of the intraorbital fatty tissue.

Forehead skin area:

• formation of longitudinal folds (“thinking lines”) in the forehead area;
• the appearance of transverse folds in the bridge of the nose area (“concentration wrinkles”).

Area around the mouth:

• deepening of nasolabial folds;
• drooping corners of the mouth;
• the formation of small transverse folds above the upper lip ("corrugation").

Cheek, neck, and auricular area:

• decreased turgor, skin elasticity and muscle tone in the cheeks and neck area, leading to a change in the facial contour and a lowering of the fat pad;
• the appearance of folds in the behind-the-ear and anterior-ear regions, changes in the shape of the auricle due to drooping lobes.

Menopausal skin aging

An important role in the development of aging is played by physiological age-related changes in the endocrine system, especially those occurring in the female body. After the onset of menopause, the aging process accelerates. There is a decrease in the level of estradiol production in the ovaries, resulting in the cessation of menstruation, hot flashes, increased blood pressure, osteoporosis and other changes. Estrogen deficiency significantly affects various structures in the skin. It is known that the average level of estradiol in blood plasma during a normal menstrual cycle is about 100 pg / ml, and at the beginning of menopause it drops sharply to 25 pg / ml. It is the sharp drop in estradiol concentration that explains the rapid appearance of signs of menopausal skin aging. At the same time, extraovarian synthesis of estrone in the subcutaneous fat from androstenediol by its aromatization takes place. This is why, at the stage of ovarian function fading, this hormone is the dominant estrogen, exerting a significant protective effect on the skin, especially in overweight women.

The biological "targets" for estrogens in the skin are basal keratinocytes, fibroblasts, melanocytes, and adipocytes. To date, extensive data have been accumulated on changes in the epidermis, in the area of dermal-epidermal contact, in the dermis, in the subcutaneous fat cell, and in the underlying muscles. A slowdown in the proliferation rate of basal keratinocytes is detected in the epidermis, which ultimately leads to its atrophy. A decrease in the expression of integrins and CD44, which play an important role in the adhesion and differentiation of keratinocytes, has been recorded. Thinning of the epidermis and impaired differentiation of keratinocytes lead to a disruption of the barrier properties of the skin and an increase in transepidermal water loss. Clinically described changes in the epidermis are expressed in thinning of the skin, its dryness, superficial wrinkles; the optical properties of the stratum corneum also change, becoming dull and acquiring a yellowish tint. In patients in the climacteric period, diffuse xerosis of the skin is often recorded, and xerotic eczema may develop. Dry skin and disruption of keratinization processes may be the cause of palmoplantar keratoderma (Haxthausen syndrome). Disruption of the barrier properties of the skin also leads to increased sensitivity of the skin; there are indications of increased permeability of the epidermis for various allergens and an increase in the frequency of allergic dermatitis in this age group.

As for the dermo-epidermal contact, a decrease in the content of type VII collagen in the anchor fibrils is noted during the perimenopause period. These changes lead to a disruption in the supply of nutrients to the epidermis and a smoothing of the basement membrane line, which also contributes to the development of atrophy of the superficial layers of the skin.

In the dermis, a decrease in the number and size of fibroblasts is noted, as well as a decrease in their synthetic activity, primarily with respect to the production of collagen and elastin proteins. It is now known that the number of collagen and elastic fibers, as well as the density of collagen and elastin, decrease with age. It is noted that up to 30% of collagen is lost during the first 5 years after menopause. Acceleration of degeneration of elastic fibers has been recorded. There are also indications of a decrease in the solubility of collagen molecules and a change in their mechanical properties. In addition, age-related changes include accelerated destruction of dermal fibers. It has been shown that every person after 40 years loses up to 1% of fibers per year, and during menopause this percentage increases to 2. In addition, qualitative changes in the composition of glycosaminoglycans (GAG) also occur, with the peak of these changes recorded by the age of 50, which often corresponds to the age of menopause. It is also emphasized that by the age of 50, the content of chonroitin sulfate (CS) decreases, especially in the papillary layer of the dermis, as well as in the depth of wrinkles.

Summarizing the complex of dermal changes in perimenopause, we can conclude that they lead to a violation of elasticity, skin turgor and the appearance of first superficial and then deep wrinkles.

Currently, an important role in the formation of deep wrinkles and deformation of the facial contour during the perimenopause period is attributed not only to changes in the epidermis and dermis, but also to subcutaneous fat tissue and facial muscles. The volume and distribution of subcutaneous fat tissue of the face changes. It has been proven that physiological atrophy of adipocytes occurs. A decrease in peroxisomal activity of adipocytes has been noted, which leads to significant disturbances in the regulation of their population, as well as to a decrease in the ability to accumulate fats.

Against the background of hypoestrogenism, melanogenesis also intensifies, which often leads to the appearance of melasma (chloasma). The appearance of erythema on the face is explained by the deficiency of the effect of estrogens on the superficial vascular network. This fact is the cause of the development of rosacea - a dermatosis that is very typical for the climacteric period. A sudden sharp drop in the concentration of estradiol and a gradual decrease in progesterone production in some cases leads to an increase in androgenic effects on the skin, the consequences of which are hirsutism, seborrhea and acne (acne tarda), androgenetic alopecia. Changes in the composition of sebum and the rate of its production, as well as a violation of the barrier properties of the skin predispose to the development of seborrheic dermatitis. A complex of morphological and hormonal changes can lead to the debut of psoriasis, lichen planus and other chronic inflammatory dermatoses in the climacteric period. In addition, during menopause, the skin becomes more susceptible to photoaging, since the production of sunscreen melanin becomes uneven and the skin's defense system against damage caused by UVR is weakened.

It is also common to distinguish different types of aging. When assessing signs of age-related changes in the skin, it is important to take into account the type of aging, since the algorithms for their correction differ from each other.

1. The "tired face" type occurs at the earliest stages of aging. Characterized by decreased skin turgor, swelling, pastosity of the face, mainly due to impaired lymph drainage. This type already has changes in the tone of the facial muscles. The severity of the nasolabial folds, drooping corners of the eyes and lips create the impression of fatigue, exhaustion.
2. The fine-wrinkled type, or "wrinkled face", is characterized mainly by degenerative-dystrophic changes in the epidermis and dermis. Typically, there is a decrease in turgor, a decrease in skin elasticity, its dehydration, and a violation of barrier properties. The consequence of this is multiple fine wrinkles that persist in a state of mimic rest, dry skin, and the appearance of such a symptom as large-porosity of the skin.
3. The deforming (deformational) type, or large-wrinkle type, or "deformed face", is characterized by impaired skin elasticity, decreased facial muscle tone, impaired lymphatic drainage, and venous stasis. Changes in facial muscle tone include hypertonicity of the main muscles of the upper and lower thirds of the face and hypotonicity of the muscles mainly of the middle third of the face. Thus, mm. depressor lobii inferioris, procerus, frontalis, depressor anguli oris and other muscles are in a state of hypertonicity, while mm. zigomaticus major et minor, orbicularis oculus, risorius, buccinator, etc. are in a state of hypotonicity. The result is a change in the configuration of the face and neck: disruption of the oval line of the face, sagging skin of the upper and lower eyelids, the appearance of a "double" chin, the formation of deep folds and wrinkles (nasolabial fold, cervicomental fold, wrinkles from the corners of the mouth to the chin, etc.). Characteristic for individuals with well-developed subcutaneous fat. Against the background of impaired muscle tone and increased tissue extensibility, gravitational displacement of subcutaneous fat occurs in the cheek area with the formation of overhanging cheeks and so-called "hernias" of the lower eyelid, representing an accumulation of fat in this area.
4. The combined type of aging is characterized by a combination of the first three types.
5. The muscular type of aging is characterized by a decrease in the volume of subcutaneous fat. Representatives of this type initially have well-developed facial muscles and a weakly expressed subcutaneous fat base. Typical for residents of Central Asia and the Far East. Against the background of age-related changes, pronounced mimic wrinkles are noted in the corners of the mouth, on the forehead, deep nasolabial folds, and a smoothed facial oval line.

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