Photoaging is the characteristic structural and functional alteration of the skin due to repeated exposure to ultraviolet light.
Clinical changes are wrinkles, leathery appearance, skin laxity, roughness, atrophy, smudgy pigmented spots such as age spots, pigmentary disorder phenomenon, freckles, dilated or absent capillaries, grayish, lusterless or grayish-yellow skin appearance, purpura, and cancerous lesions.
Photoaging is more pronounced in light-skinned people. It is most evident on the face, neck, and the extensor side of the upper limbs. The distribution of photoaging is related to the style of dressing, hairstyle and sun exposure. It is related to the anatomical distribution of skin structures (e.g., melanocytes and sebaceous glands). The severity of the changes depends on the individual’s tolerance to sunlight and the ability to repair sun damage.
Treatment of skin photoaging
1. Retinoic acid
Retinoic acid is the most widely reported drug in the literature for photoaging treatment. 0.05% all-trans retinoic acid cream is currently the only product approved by the FDA for the treatment of photoaging. Patients treated with retinoic acid showed significant improvement in local wrinkles, punctate pigmentation and skin roughness. The mechanism of action of retinoic acid in the treatment of skin photoaging is mainly manifested in preventing the reduction of collagen fibers, increasing the synthesis of collagen fibers and inhibiting the appearance of abnormal elastic fibers; blocking the inflammatory response; and promoting the clearance of melanin or melanophagocytes. From the perspective of biological regulation, retinoic acid, as a powerful regulator of cell proliferation, differentiation and gene expression, has a multifaceted effect on the metabolism of epidermis and dermis.
2.Antioxidant agents
Oxygen free radicals or reactive oxygen radicals play an important role in the process of skin photoaging, and the use of antioxidants orally or topically is an effective way to prevent skin photoaging damage. Commonly used antioxidants include vitamin E, vitamin C, beta-carotene, etc., which can be taken orally or used topically.
Coenzyme Q10: The photoaging process is closely related to cellular oxidation, which is partly due to the decrease of endogenous coenzyme Q10 level. Topical coenzyme Q10 is effective in preventing a variety of damages in photoaging. Topical coenzyme Q10 penetrates all layers of the epidermis and effectively counteracts UVA-induced oxidative stress, while preventing oxidative DNA damage, and coenzyme Q10 also significantly inhibits collagenase overexpression in fibroblasts.
L-ascorbic acid
L-ascorbic acid, which is found in large quantities in fruits, vegetables and vegetables, can strongly inhibit the activity of tyrosinase and has a significant effect on melanin inhibition and spot removal. It cannot be synthesized in the body and can only be taken from food. What we eat is a mixture of left and right spin, which is broken down into left spin only when it reaches the body, playing the role of cleaning the blood, increasing the toughness of blood vessel walls and increasing collagen production. L-vitamin C cannot be absorbed through the skin. The Cellex-c produced by Denver in the United States can be used directly and absorbed percutaneously.
Hydroxyacetic acid: It can promote the proliferation of fibroblasts. In the hairless mouse model of photoaging, after 10 weeks of topical application of 15% hydroxyacetic acid, wrinkles were significantly reduced, the dermal repair zone was significantly widened, and the synthetic collagen fibers were significantly increased. 25% hydroxyacetic acid lotion significantly increased the thickness of the skin, atypical basal cells became normal, melanocyte clustering phenomenon was reduced, and the distribution of normal network, dermal collagen fibers increased, elastic fibers became longer and thicker, and fracture was significantly reduced. The dermal collagen fibers increased, the elastic fibers became longer and thicker, and the fracture was significantly reduced.
L-epigallocatechin-3-gallate: It is a major polyphenol component in green tea, which has a preventive effect on photoaging when applied topically. Mechanism of action: blocking UVB-induced CD 11b+ cell infiltration to inflammation sites, reducing IL-10 production in skin and local lymph nodes, increasing IL-12 production in local lymph nodes; reducing spinal peroxidase activity; inhibiting prostaglandin (PG) metabolism in microsomes, especially PC2, PG metabolism plays an extremely important role in free radical production, skin tumorigenesis Pre-administration of EGCG treatment reduced the number of UVB-induced epidermal cell death.
In addition, alkaline amino acid iron ion chelator can mimic the binding site of iron chelator protein, which is inactivated by binding to iron ions, preventing the production of free radicals catalyzed by iron ions;
PL is a tropical fern of the family Hydrocotyleae, and PL has photoprotective and immunomodulatory effects both in vivo and in vitro. PL has significant photoprotective effects when administered internally or externally. Internal administration of PL shows good promise for systemic photoprotection and will make photochemotherapy and phototherapy safer.
3.Laser/photon therapy
CO2 laser: CO2 laser grinding has been used to treat facial photoaging since 1993. After treatment with high-energy CO2 pulsed laser, the epidermal thickness and fibrous tissue formation zone thickened with increased collagen fiber density; while the thickness of heliotropic elastic fiber zone decreased with reduced density. The high-energy CO2 pulsed laser can reverse the photoaging changes in the epidermis and dermis at the ultrastructural level. Long-term clinical follow-up shows that patients treated with C02 laser have significant and stable improvement of facial wrinkles and high patient satisfaction rate. However, hyperpigmentation is the most common side effect for yellow individuals. Also, a longer recovery time is required after the procedure.
Er:YAG laser: Comparison of wrinkle reduction results with C02 laser revealed that patients treated with C02 laser had longer lasting facial scabs than Er:YAG laser and lower wrinkle improvement rate than Er:YAG laser, and both had no posterior scarring. For yellows, hyperpigmentation remains the most common side effect.
Fraxel laser: The Fraxel laser works on the skin through an intensive pinhole-like laser beam to remove superficial hyperpigmentation and capillary dilation, and stimulates the proliferation and rearrangement of dermal collagen fibers for the purpose of skin rejuvenation. The procedure causes minimal damage and hardly affects the patient’s daily life.
Intense Pulsed Light (IPL): The so-called photorejuvenation technique uses incoherent intense pulsed light (IPL) technology to perform non-exfoliative skin rejuvenation treatments with low energy density. IPL emits a spectral range of 510-1200nm, and its longer wavelengths can lead to significant improvement in photodamage and aging of the skin, while shorter wavelengths can treat pigmented and vascular lesions of the skin. In addition to its significant wrinkle rejuvenation effect, it can also treat skin damage such as enlarged pores, capillary dilation and a variety of pigment spots, significantly improving the appearance of facial skin. The most significant advantage is that it is non-ablative and painless, and patients can work and socialize as usual after the treatment.
Radiofrequency: Radiofrequency radiation of about 4MH acts on the dermis, producing a thermal effect that causes the dermal collagen fibers to proliferate and rearrange, resulting in skin rejuvenation. The treatment is safe, without side effects such as discoloration, and does not affect the patient’s daily life.