Structural and Functional Changes and Possible Molecular Mechanisms in Aged Skin

Mechanism of action and therapeutic effects of oxidative stress and stem cell-based materials in skin aging: Current evidence and future perspectives

Aging is associated with multiple degenerative diseases, including atherosclerosis, osteoporosis, and Alzheimer's disease. As the most intuitive manifestation of aging, skin aging has received the most significant attention. Skin aging results from various intrinsic and extrinsic factors. Aged skin is characterized by wrinkles, laxity, elastosis, telangiectasia, and aberrant pigmentation. The underlying mechanism is complex and may involve cellular senescence, DNA damage, oxidative stress (OS), inflammation, and genetic mutations, among other factors. Among them, OS plays an important role in skin aging, and multiple antioxidants (e.g., vitamin C, glutathione, and melatonin) are considered to promote skin rejuvenation. In addition, stem cells that exhibit self-replication, multi-directional differentiation, and a strong paracrine function can exert anti-aging effects by inhibiting OS. With the further development of stem cell technology, treatments related to OS mitigation and involving stem cell use may have a promising future in anti-skin aging therapy.

TRPV1: A promising therapeutic target for skin aging and inflammatory skin diseases

TRPV1 is a non-selective channel receptor widely expressed in skin tissues, including keratinocytes, peripheral sensory nerve fibers and immune cells. It is activated by a variety of exogenous or endogenous inflammatory mediators, triggering neuropeptide release and neurogenic inflammatory response. Previous studies have shown that TRPV1 is closely related to the occurrence and/or development of skin aging and various chronic inflammatory skin diseases, such as psoriasis, atopic dermatitis, rosacea, herpes zoster, allergic contact dermatitis and prurigo nodularis. This review summarizes the structure of the TRPV1 channel and discusses the expression of TRPV1 in the skin as well as its role of TRPV1 in skin aging and inflammatory skin diseases.

Evaluation and characterization of facial skin aging using optical coherence tomography

OBJECTIVES

The skin aging exposome encompasses internal and external factors that contribute to clinical signs of facial aging. Aging skin can be characterized by distinctive features such as wrinkles, lentigines, elastosis, and roughness. Optical coherence tomography (OCT) is capable of noninvasively measuring skin characteristics. This study aimed to assess bilateral features using OCT to explore temporal skin changes among decades and potential changes in facial skin aging based on laterality.

METHODS

A total of 97 subjects between 20 and 89 years old with Fitzpatrick skin types I to IV were enrolled. VivoSight, a Multi-Beam OCT system intended to gather topographical and histological images of skin, was used to scan the area inferolateral to the lateral canthus, bilaterally. Investigators compared characteristics of skin roughness, attenuation coefficient and blood flow across age groups and based on laterality to determine any differences.

RESULTS

Only data from successful OCT scans were used. Seventy subjects, 10 from each specified decade, had successful bilateral scans and were thus included in the analysis. Chronological aging was characterized by significantly decreased dermal attenuation coefficient with increased age. Skin roughness measurements showed trends of increased roughness with age; however, no statistically significant changes were seen between groups. Qualitative differences amongst scans taken on right and left sides of the face showed no significance regarding roughness, density or blood flow at depths ranging from 0.05 to 0.5 mm.

CONCLUSIONS

OCT is an effective method for evaluating changes in aging skin. Our results illustrate a decline in skin density with chronological age. Additionally, it was illustrated that structural change in the epidermis and dermis does occur, however on a microscopic scale, there are no significant differences based on laterality. OCT holds promise as a noninvasive technique for characterization of aging skin. Its utility and application in the clinical management and treatment of aged skin requires further research; however, the technology has potential to personalize therapies based on objective findings.

Current Understanding of the Role of Senescent Melanocytes in Skin Ageing

Melanocytes reside within the basal epidermis of human skin, and function to protect the skin from ultraviolet light through the production of melanin. Prolonged exposure of the skin to UV light can induce irreparable DNA damage and drive cells into senescence, a sustained cell cycle arrest that prevents the propagation of this damage. Senescent cells can also be detrimental and contribute to skin ageing phenotypes through their senescence-associated secretory phenotype. Senescent cells can act in both an autocrine and paracrine manner to produce widespread tissue inflammation and skin ageing. Recently, melanocytes have been identified as the main senescent cell population within the epidermis and have been linked to a variety of skin ageing phenotypes, such as epidermal thinning and the presence of wrinkles. However, the literature surrounding melanocyte senescence is limited and tends to focus on the role of senescence in the prevention of melanoma. Therefore, this review aims to explore the current understanding of the contribution of senescent melanocytes to human skin ageing.

Potentilloside A, a New Flavonol-bis-Glucuronide from the Leaves of Potentilla chinensis, Inhibits TNF-α-Induced ROS Generation and MMP-1 Secretion

The major contributor to skin aging is UV radiation, which activates pro-inflammatory cytokines including TNF-α. TNF-α is involved in the acceleration of skin aging via ROS generation and MMP-1 secretion. In our preliminary study, a 30% EtOH extract from the leaves of Potentilla chinensis (LPCE) significantly inhibited TNF-α-induced ROS generation in human dermal fibroblasts (HDFs). Therefore, the objective of this study is to identify the active components in LPCE. A new flavonol-bis-glucuronide (potentilloside A, 1) and 14 known compounds (2-15) were isolated from an LPCE by repeated chromatography. The chemical structure of the new compound 1 was determined by analyzing its spectroscopic data (NMR and HRMS) and by acidic hydrolysis. Nine flavonols (2-9 and 11) and two flavone glycosides (12 and 13) from P. chinensis were reported for the first time in this study. Next, we evaluated the effects of the isolates (1-15) on TNF-α-induced ROS generation in HDFs. As a result, all compounds significantly inhibited ROS generation. Furthermore, LPCE and potentilloside A (1) remarkably suppressed MMP-1 secretion in HDFs stimulated by TNF-α. The data suggested that LPCE and potentilloside A (1) are worthy of further experiments for their potential as anti-skin aging agents.

Involvement of caveolin-1 in skin diseases

The skin is the outermost layer and largest organ in the human body. Since the skin interfaces with the environment, it has a variety of roles, including providing a protective barrier against external factors, regulating body temperature, and retaining water in the body. It is also involved in the immune system, interacting with immune cells residing in the dermis. Caveolin-1 (CAV-1) is essential for caveolae formation and has multiple functions including endocytosis, lipid homeostasis, and signal transduction. CAV-1 is known to interact with a variety of signaling molecules and receptors and may influence cell proliferation and migration. Several skin-related disorders, especially those of the inflammatory or hyperproliferative type such as skin cancers, psoriasis, fibrosis, and wound healing, are reported to be associated with aberrant CAV-1 expression. In this review, we have explored CAV-1 involvement in skin physiology and skin diseases.

Protective Effect of Bifidobacterium animalis subs. lactis MG741 as Probiotics against UVB-Exposed Fibroblasts and Hairless Mice

Skin photoaging, which causes wrinkles, increased epidermal thickness, and rough skin texture, is induced by ultraviolet B (UVB) exposure. These symptoms by skin photoaging have been reported to be involved in the reduction of collagen by the expression of matrix metalloproteinases (MMPs) and activator protein-1 (AP-1). This study investigated the protective effects of Bifidobacterium animalis subsp. lactis MG741 (Bi. lactis MG741) in Hs-68 fibroblasts and hairless mice (HR-1) following UVB exposure. We demonstrated that the Bi. lactis MG741 reduces wrinkles and skin thickness by downregulating MMP-1 and MMP-3, phosphorylation of extracellular signal-regulated kinase (ERK), and c-FOS in fibroblasts and HR-1. Additionally, in UVB-irradiated dorsal skin of HR-1, Bi. lactis MG741 inhibits the expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), an inflammation-related factor. Thus, Bi. lactis MG741 has the potential to prevent wrinkles and skin inflammation by modulating skin photoaging markers.

Effectiveness of Topical Conditioned Medium of Stem Cells in Facial Skin Nonsurgical Resurfacing Modalities for Antiaging: Systematic Review and Meta-Analysis of Randomized Controlled Trials

Facial skin nonsurgical resurfacing modalities, including laser, chemical peeling, and microneedling, have become common due to increasing public concern about skin aging. The potential effect of stem cell conditioned medium (CM) for antiaging has been reported in recent years, and such medium may be able to improve the efficacy of resurfacing modalities. This study investigated the efficacy of topical CM combined with resurfacing in comparison with resurfacing alone. We searched the PubMed, Embase, and Cochrane Library databases for randomized controlled trials (RCTs). We used the Cochrane risk-of-bias tool (version 2) to assess the risk of bias of the included studies and Review Manager (version 5.4) for data analysis. Means and standard deviations of outcomes, namely wrinkle, pigmentation, pore, and overall improvement, were extracted. After screening, we included five RCTs in the analysis, four of which were quantitatively analyzed. The result revealed that stem cell CM significantly reduced wrinkles (P = 0.0006), pigmentation (P = 0.004), and pores (P = 0.01) and improved overall skin condition (P < 0.0001). In summary, we suggest that stem cell CM is a safe treatment that can enhance the efficacy of facial skin nonsurgical resurfacing modalities.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

On the Potential Role of the Antioxidant Couple Vitamin E/Selenium Taken by the Oral Route in Skin and Hair Health

The relationship between oxidative stress and skin aging/disorders is well established. Many topical and oral antioxidants (vitamins C and E, carotenoids, polyphenols) have been proposed to protect the skin against the deleterious effect induced by increased reactive oxygen species production, particularly in the context of sun exposure. In this review, we focused on the combination of vitamin E and selenium taken in supplements since both molecules act in synergy either by non-enzymatic and enzymatic pathways to eliminate skin lipids peroxides, which are strongly implicated in skin and hair disorders.

Laser-assisted nanoparticle delivery to promote skin absorption and penetration depth of retinoic acid with the aim for treating photoaging

Retinoic acid (RA) is an approved treatment for skin photoaging induced by ultraviolet (UVA). Topically applied RA is mainly located in the stratum corneum (SC) with limited diffusion into the deeper strata. A delivery system capable of facilitating dermal delivery and cellular internalization for RA is critical for a successful photoaging therapy. Two delivery approaches, namely nanoparticles and laser ablation, were combined to improve RA's absorption efficacy and safety. The nanoparticle absorption enhancement by the lasers was compared between full-ablative (Er:YAG) and fractional (CO₂) modalities. We fabricated poly-L-lactic acid (PLA) and PLA/poly(lactic-co-glycolic acid) (PLGA) nanoparticles by an emulsion-solvent evaporation technique. The mean size of PLA and PLA/PLGA nanocarriers was 237 and 222 nm, respectively. The RA encapsulation percentage in both nanosystems was > 96 %. PLA and PLA/PLGA nanocarriers promoted RA skin deposition by 5- and 3-fold compared to free control. The ablative lasers further enhanced the skin deposition of RA-loaded nanoparticles, with the full-ablative laser showing greater permeation enhancement than the fractional mode. The skin biodistribution assay evaluated by confocal and fluorescence microscopies demonstrated that the laser-assisted nanoparticle delivery achieved a significant dermis and follicular accumulation. The cell-based study indicated a facile uptake of the nanoparticles into the human dermal fibroblasts. The nanoparticulate RA increased type I collagen and elastin production in the UVA-treated fibroblasts. A reduction of matrix metalloproteinase (MMP)-1 was also highlighted in the photoaging cells. The calculation of therapeutic index (TI) by multiplying collagen/elastin elevation percentage and skin deposition predicted better anti-photoaging performance in Er:YAG laser-assisted nanoparticle delivery than CO₂ laser. Nanoencapsulation of RA decreased the cytotoxicity against skin fibroblasts. In vivo skin tolerance test on a nude mouse showed less skin damage after topical application of the nanoparticles than free RA. Our results hypothesized that the laser-mediated nanoparticle delivery provided an efficient and safe use for treating photoaging.

Cultured Human Foreskin as a Model System for Evaluating Ionizing Radiation-Induced Skin Injury

Purpose: Precise molecular and cellular mechanisms of radiation-induced dermatitis are incompletely understood. Histone variant H2A.J is associated with cellular senescence and modulates senescence-associated secretory phenotype (SASP) after DNA-damaging insults, such as ionizing radiation (IR). Using ex vivo irradiated cultured foreskin, H2A.J was analyzed as a biomarker of radiation-induced senescence, potentially initiating the inflammatory cascade of radiation-induced skin injury. Methods: Human foreskin explants were collected from young donors, irradiated ex vivo with 10 Gy, and cultured in air-liquid interphase for up to 72 h. At different time-points after ex vivo IR exposure, the foreskin epidermis was analyzed for proliferation and senescence markers by immunofluorescence and immunohistochemical staining of sectioned tissue. Secretion of cytokines was measured in supernatants by ELISA. Using our mouse model with fractionated in vivo irradiation, H2A.J expression was analyzed in epidermal stem/progenitor cell populations localized in different regions of murine hair follicles (HF). Results: Non-vascularized foreskin explants preserved their tissue homeostasis up to 72 h (even after IR exposure), but already non-irradiated foreskin epithelium expressed high levels of H2A.J in all epidermal layers and secreted high amounts of cytokines. Unexpectedly, no further increase in H2A.J expression and no obvious upregulation of cytokine secretion was observed in the foreskin epidermis after ex vivo IR. Undifferentiated keratinocytes in murine HF regions, by contrast, revealed low H2A.J expression in non-irradiated skin and significant radiation-induced H2A.J upregulations at different time-points after IR exposure. Based on its staining characteristics, we presume that H2A.J may have previously underestimated the importance of the epigenetic regulation of keratinocyte maturation. Conclusions: Cultured foreskin characterized by highly keratinized epithelium and specific immunological features is not an appropriate model for studying H2A.J-associated tissue reactions during radiation-induced dermatitis.

Anti-Inflammatory microRNAs for Treating Inflammatory Skin Diseases

Skin inflammation occurs due to immune dysregulation because of internal disorders, infections, and allergic reactions. The inflammation of the skin is a major sign of chronic autoimmune inflammatory diseases, such as psoriasis, atopic dermatitis (AD), and lupus erythematosus. Although there are many therapies for treating these cutaneous inflammation diseases, their recurrence rates are high due to incomplete resolution. MicroRNA (miRNA) plays a critical role in skin inflammation by regulating the expression of protein-coding genes at the posttranscriptional level during pathogenesis and homeostasis maintenance. Some miRNAs possess anti-inflammatory features, which are beneficial for mitigating the inflammatory response. miRNAs that are reduced in inflammatory skin diseases can be supplied transiently using miRNA mimics and agomir. miRNA-based therapies that can target multiple genes in a given pathway are potential candidates for the treatment of skin inflammation. This review article offers an overview of the function of miRNA in skin inflammation regulation, with a focus on psoriasis, AD, and cutaneous wounds. Some bioactive molecules can target and modulate miRNAs to achieve the objective of inflammation suppression. This review also reports the anti-inflammatory efficacy of these molecules through modulating miRNA expression. The main limitations of miRNA-based therapies are rapid biodegradation and poor skin and cell penetration. Consideration was given to improving these drawbacks using the approaches of cell-penetrating peptides (CPPs), nanocarriers, exosomes, and low-frequency ultrasound. A formulation design for successful miRNA delivery into skin and target cells is also described in this review. The possible use of miRNAs as biomarkers and therapeutic modalities could open a novel opportunity for the diagnosis and treatment of inflammation-associated skin diseases.

Human organ rejuvenation by VEGF-A: Lessons from the skin

Transplanting aged human skin onto young SCID/beige mice morphologically rejuvenates the xenotransplants. This is accompanied by angiogenesis, epidermal repigmentation, and substantial improvements in key aging-associated biomarkers, including ß-galactosidase, p16^ink4a, SIRT1, PGC1α, collagen 17A, and MMP1. Angiogenesis- and hypoxia-related pathways, namely, vascular endothelial growth factor A (VEGF-A) and HIF1A, are most up-regulated in rejuvenated human skin. This rejuvenation cascade, which can be prevented by VEGF-A-neutralizing antibodies, appears to be initiated by murine VEGF-A, which then up-regulates VEGF-A expression/secretion within aged human skin. While intradermally injected VEGF-loaded nanoparticles suffice to induce a molecular rejuvenation signature in aged human skin on old mice, VEGF-A treatment improves key aging parameters also in isolated, organ-cultured aged human skin, i.e., in the absence of functional skin vasculature, neural, or murine host inputs. This identifies VEGF-A as the first pharmacologically pliable master pathway for human organ rejuvenation in vivo and demonstrates the potential of our humanized mouse model for clinically relevant aging research.

Photoaging: UV radiation-induced inflammation and immunosuppression accelerate the aging process in the skin

Background

Excessive exposure of the skin to UV radiation (UVR) triggers a remodeling of the immune system and leads to the photoaging state which is reminiscent of chronological aging. Over 30 years ago, it was observed that UVR induced an immunosuppressive state which inhibited skin contact hypersensitivity.

Methods

Original and review articles encompassing inflammation and immunosuppression in the photoaging and chronological aging processes were examined from major databases including PubMed, Scopus, and Google Scholar.

Results

Currently it is known that UVR treatment can trigger a cellular senescence and inflammatory state in the skin. Chronic low-grade inflammation stimulates a counteracting immunosuppression involving an expansion of immunosuppressive cells, e.g., regulatory T cells (Treg), myeloid-derived suppressor cells (MDSC), and regulatory dendritic cells (DCreg). This increased immunosuppressive activity not only suppresses the function of effector immune cells, a state called immunosenescence, but it also induces bystander degeneration of neighboring cells. Interestingly, the chronological aging process also involves an accumulation of pro-inflammatory senescent cells and signs of chronic low-grade inflammation, called inflammaging. There is also clear evidence that inflammaging is associated with an increase in anti-inflammatory and immunosuppressive activities which promote immunosenescence.

Conclusion

It seems that photoaging and normal aging evoke similar processes driven by the remodeling of the immune system. However, it is likely that there are different molecular mechanisms inducing inflammation and immunosuppression in the accelerated photoaging and the chronological aging processes.

Anti-Skin-Aging Effect of a Treatment with a Cosmetic Product and a Food Supplement Based on a New Hyaluronan: A Randomized Clinical Study in Healthy Women

Hyaluronic acid (HA) has long been used for its anti-age properties, as an ingredient in both topical applications and food supplements. In this study, a novel sodium hyaluronate, based on the innovative full spectrum technology, was administered as an ingredient of a cosmetic product and as the main constituent of a food supplement to evaluate its efficacy in counteracting skin ageing signs. Seventy-five female subjects were randomly assigned to the following treatments for 4 weeks: an active food supplement and a placebo cosmetic product, an active cosmetic product and a placebo food supplement, and a combination of the two products containing the active ingredient, that is, an “In&Out” treatment. The subjects used the placebo cosmetic product for another 14 days. Improvement of all the outcome measures (skin moisturization, elasticity, firmness and profilometry) was achieved by all treatments (p < 0.05); however, the combined treatment resulted in a further amelioration of the skin aging signs with respect to the two single active treatments (p < 0.001), and such effect lasted also after the follow-up period. In conclusion, such results confirmed that the concomitant administration of hyaluronans by these two different routes represents more than an interesting approach to counteract skin aging signs.

Anti-Inflammatory and Pro-Regenerative Effects of Hyaluronan-Chitlac Mixture in Human Dermal Fibroblasts: A Skin Ageing Perspective

Inflammation and the accumulation of reactive oxygen species (ROS) play an important role in the structural and functional modifications leading to skin ageing. The reduction of inflammation, cellular oxidation and dermal extracellular matrix (ECM) alterations may prevent the ageing process. The aim of this study is to investigate the expression of pro-inflammatory markers and ECM molecules in human dermal fibroblasts derived from young and middle-aged women and the effects of lactose-modified chitosan (Chitlac®, CTL), alone or in combination with mid-MW hyaluronan (HA), using an in vitro model of inflammation. To assess the response of macrophage-induced inflamed dermal fibroblasts to HA and CTL, changes in cell viability, pro-inflammatory mediators, MMPs and ECM molecules expression and intracellular ROS generation are analysed at gene and protein levels. The expression of pro-inflammatory markers, galectins, MMP-3 and ECM molecules is age-related. CTL, HA and their combination counteracted the oxidative damage, stimulating the expression of ECM molecules, and, when added to inflamed cells, restored the baseline levels of IL-1β, TNF-α, GAL-1, GAL-3 and MMP-3. In conclusion, HA and CTL mixture attenuated the macrophage-induced inflammation, inhibited the MMP-3 expression, exhibited the anti-oxidative effects and exerted a pro-regenerative effect on ECM.

Cutaneous immune-related adverse events and photodamaged skin in metastatic melanoma patients: Could the use of nicotinamide be useful?

Cutaneous immune-related adverse events occur in more than one-third of patients treated with immune checkpoint inhibitors; they are often the first clinical manifestation although they may occur months after initiation of therapy.We noticed that our patients usually have these cutaneous adverse events on photodamaged skin. In fact, out of 19 patients being treated for metastatic melanoma, patients (42%) with significant cutaneous actinic damage presented cutaneous immuno-related adverse events earlier and in a more serious form. Thus, our metastatic melanoma patients with photodamaged skin who were initiating immunotherapy were given a high oral dose of nicotinamide (500 mg twice daily)for the entire duration of therapy. In treated patients, the appearance of the first signs of cutaneous immuno-related adverse events was 180 days after starting therapy rather than 65 days for untreated patients.