Attenuation of intrinsic aging of the skin via elimination of senescent dermal fibroblasts with senolytic drugs

Senolytic Targeting of Anti-Apoptotic Bcl Family Increases Cell Death in UV-Irradiated Senescent Melanocytes: Search for Senolytics

Senescent melanocytes have been suggested to play a role in the development of ageing-associated pigmentary changes and skin ageing. Here, we assessed the senolytic capacity of recognised senolytic chemicals and natural compounds in UV-irradiated senescent melanocytes. Among the tested agents, only ABT-737 and ABT-263 showed a significant reduction in the number of SA-β-Gal-positive senescent melanocytes and in the expressions of p16INK4A and p21Waf1. The senolytic effects of the ABT drugs were associated with increased expression of cleaved caspase-3, which was hindered with a caspase inhibitor, Z-VAD. These findings indicate that ABT-737 and ABT-263 eliminate senescent melanocytes through caspase-mediated apoptosis, suggesting their future potential to address ageing skin.

Topical ABT-263 treatment reduces aged skin senescence and improves subsequent wound healing

Senescent cells accumulate in aging tissues, impairing their ability to undergo repair and regeneration following injury. Previous research has demonstrated that targeting tissue senescence with senolytics can enhance tissue regeneration and repair by selectively eliminating SnCs in specific aged tissues. In this study, we focused on eliminating senescent skin cells in aged mice to assess the effects on subsequent wound healing. We applied ABT-263 directly to the skin of 24-month-old mice over a 5-day period. Following topical ABT-263, aged skin demonstrated decreased gene expression of senescence markers p16 and p21, accompanied by reductions in SA-β-gal- and p21-positive cells compared to DMSO controls. However, ABT-263 also triggered a temporary inflammatory response and macrophage infiltration in the skin. Bulk RNA sequencing of ABT-263-treated skin revealed prompt upregulation of genes associated with wound healing pathways, including hemostasis, inflammation, cell proliferation, angiogenesis, collagen synthesis, and extracellular matrix organization. Aged mice skin pre-treated with topical ABT-263 exhibited accelerated wound closure. In conclusion, topical ABT-263 effectively reduced several senescence markers in aged skin, thereby priming the skin for improved subsequent wound healing. This enhancement may be attributed to ABT-263-induced senolysis which in turn stimulates the expression of genes involved in extracellular matrix remodeling and wound repair pathways.

Elimination of physiological senescent cutaneous cells in a novel p16-dependent senolytic mouse model impacts lipid metabolism in skin aging

The evidence of the correlation between cellular senescence and aging has increased in research with animal models. These models have been intentionally generated to target and regulate cellular senescent cells with the promoter activity of p16Ink4a or p19Arf, genes that are highly expressed in aging cells. However, the senolytic efficiency in various organs and cells from these models represents unexpected variation and diversity in some cases. We have generated a novel knock-in model, p16tdT-hDTR mice, which possess tdTomato and human diphtheria toxin receptor (hDTR) downstream of Cdkn2a, an endogenous p16Ink4a gene. We successfully demonstrated that p16-derived tdTomato and hDTR expressions are observed in these mouse embryo fibroblasts and following treatment with diphtheria toxin (DT) eliminates those cells. Furthermore, we demonstrated the efficacy of eliminating p16-positive cells in vivo, and also observed a tendency to decrease their cutaneous SA-β-gal activity after subcutaneous DT injection into p16tdT-hDTR mice. In particular, comprehensive gene expression analysis in skin revealed that upregulated genes related to lipid metabolisms with aging exhibited remarkable expressions under the senolysis. These results clearly unveiled p16-positive senescent cells contribute to age-related changes in skin.

Aging, senescence, and cutaneous wound healing-a complex relationship

Cutaneous wound healing is a complex multi-step process that is highly controlled, ensuring efficient repair to damaged tissue and restoring tissue architecture. Multiple cell types play a critical role in wound healing, and perturbations in this can lead to non-healing wounds or scarring and fibrosis. Thus, the process is tightly regulated and controlled. Cellular senescence is defined as irreversible cell cycle arrest and is associated with various phenotypic changes and metabolic alterations and coupled to a secretory program. Its role in wound healing, at least in the acute setting, appears to help promote appropriate mechanisms leading to the complete restoration of tissue architecture. Opposing this is the role of senescence in chronic wounds where it can lead to either chronic non-healing wounds or fibrosis. Given the two opposing outcomes of wound healing in either acute or chronic settings, this has led to disparate views on the role of senescence in wound healing. This review aims to consolidate knowledge on the role of senescence and aging in wound healing, examining the nuances of the roles in the acute or chronic settings, and attempts to evaluate the modulation of this to promote efficient wound healing.

The senolytic drug ABT-263 accelerates ovarian aging in older female mice

Previous studies have reported that senolytic drugs can reverse obesity-mediated accumulation of senescent cells in the ovary and protect against cisplatin-induced ovarian injury by removing senescent cells. Early intervention with ABT-263 has been shown to mitigate ovarian aging. However, it remains unknown whether treatment with ABT-263 could rejuvenate the aged ovary in reproductively old females. Therefore, the current study was aimed to investigate whether advanced age intervention with ABT-263 could ameliorate age-related decline in ovarian function. Fourteen 16-month-old mice with a C57/BL6 background were treated with ABT-263 (N = 7) or vehicle (N = 7) for two weeks. Mice were initially treated with ABT-263 (60 mg/kg/d) or vehicle for 7 consecutive days. After a 7-day break, the treatment was repeated for another 7 consecutive days. Six 2-month-old mice with C57BL/6 were used as a young control. The hormonal levels, estrus cycles, ovarian reserve, ovarian cell proliferation and apoptosis, ovarian fibrosis, and steroidogenic gene expression of ovarian stromal cells were evaluated. ABT-263 treatment did not rescue abnormal estrus cycles and sex hormonal levels, or inhibit the formation of multinucleated giant cells and ovarian stromal cell apoptosis in aged ovaries. However, it reduced ovarian fibrosis and preserved the steroidogenic gene expression of ovarian stromal cells in aged ovaries. Importantly, ABT-263 treatment further depleted ovarian follicles in aged mice. In conclusion, ABT-263 treatment accelerated the depletion of ovarian follicles in aged mice, suggesting that senolytic drugs for reproductively old female may adversely affect female fertility.

Ligustilide, A Novel Senolytic Compound Isolated from the Roots of Angelica Acutiloba

Senescent cells accumulate with age and contribute to age-related diseases and organ dysfunctions. Early evidence suggests that removal of senescent cells using senolytic drugs improves the aging phenotype in mice and may improve the health of individuals with chronic diseases. Signs of skin aging, including wrinkles, and sagging, occur largely due to the accumulation of senescent fibroblasts within the dermis; However, there is currently no skin treatment that eliminates senescent cells. In this study, human fibroblasts subjected to replicative aging and ionizing radiation exposure are used to screen plant extracts for potential senescent cell-destructive and/or senescent cell-forming activities. Angelica acutiloba-a traditional Chinese herbal medicine-selectively kills senescent cells without affecting the proliferating cells. Among the major components of this herb, ligustilide shows promising senescent cell-destructive properties, and selectively eliminates senescent cells by inducing an apoptosis. Moreover, ligustilide markedly inhibits senescence-associated secretory phenotypes. Administration of ligustilide to mouse skin eliminates senescent cells and increases dermal collagen density and subcutaneous adipose tissue content; it selectively promotes death of senescent cells without affecting non-senescent cells. These results provide evidence that a natural compound-ligustilide-may exhibit therapeutic effects on the skin aging phenotype by specifically inducing apoptosis in senescent cells.

Topical ABT-263 treatment reduces aged skin senescence and improves subsequent wound healing

Senescent cells (SnC) accumulate in aging tissues, impairing their ability to undergo repair and regeneration following injury. Previous research has demonstrated that targeting tissue senescence with senolytics can enhance tissue regeneration and repair by selectively eliminating SnCs in specific aged tissues. In this study, we focused on eliminating SnC skin cells in aged mice to assess the effects on subsequent wound healing. We applied ABT-263 directly to the skin of 24-month-old mice over a 5-day period. Following topical ABT-263, aged skin demonstrated decreased gene expression of senescent markers p16 and p21, accompanied by reductions in SA-β-gal and p21-positive cells compared to DMSO controls. However, ABT-263 also triggered a temporary inflammatory response and macrophage infiltration in the skin. Bulk RNA sequencing of ABT-263-treated skin revealed prompt upregulation of genes associated with wound healing pathways, including hemostasis, inflammation, cell proliferation, angiogenesis, collagen synthesis, and extracellular matrix organization. Aged mice skin pre-treated with topical ABT-263 exhibited accelerated wound closure. In conclusion, topical ABT-263 effectively reduced several senescence markers in aged skin, thereby priming the skin for improved subsequent wound healing. This enhancement may be attributed to ABT-263-induced senolysis which in turn stimulates the expression of genes involved in extracellular matrix remodeling and wound repair pathways.

Regulation of ENPP5, a senescence-associated secretory phenotype factor, prevents skin aging

Aging negatively affects the appearance and texture of the skin owing to the accumulation of senescent fibroblasts within the dermis. Senescent cells undergo abnormal remodeling of collagen and the extracellular matrix through an inflammatory histolytic senescence-associated secretory phenotype (SASP). Therefore, suppression of SASP in senescent cells is essential for the development of effective skin anti-aging therapies. Ectonucleotide pyrophosphatase/phosphodiesterase family member 5 (ENPP5), an extracellular signaling molecule, has been implicated in vascular aging and apoptosis; however, its role in SASP remains unclear. Therefore, this study aimed to investigate the role of ENPP5 in SASP and skin aging using molecular techniques. We investigated the effects of siRNA-mediated ENPP5 knockdown, human recombinant ENPP5 (rENPP5) treatment, and lentiviral overexpression of ENPP5 on SASP and aging in human skin fibroblasts. Additionally, we investigated the effect of siRNA-mediated ENPP5 knockdown on the skin of C57BL/6 mice. We found that ENPP5 was significantly expressed in replication-aged and otherwise DNA-damaged human skin fibroblasts and that treatment with human rENPP5 and lentiviral overexpression of ENPP5 promoted SASP and senescence. By contrast, siRNA-mediated knockdown of ENPP5 suppressed SASP and the expression of skin aging-related factors. Additionally, ENPP5 knockdown in mouse skin ameliorated the age-related reduction of subcutaneous adipose tissue, the panniculus carnosus muscle layer, and thinning of collagen fibers. Conclusively, these findings suggest that age-related changes may be prevented through the regulation of ENPP5 expression to suppress SASP in aging cells, contributing to the development of anti-aging treatments for the skin.

Double-blind, vehicle-controlled clinical investigation of peptide OS-01 for skin rejuvenation

INTRODUCTION

Senescent cells contribute to age-related tissue deterioration, including the skin, which plays important roles in overall health and social interactions. This study aimed to assess the effects of the senotherapeutic peptide, OS-01 (a.k.a. Pep 14), on skin.

METHODS

A 12-week split-face, double-blinded, vehicle-controlled study involving 22 participants was conducted. The OS-01-containing formulation was applied to one side of the face, while the other side received an identical control formulation lacking the peptide. Skin characteristics were assessed using instrumental measurements, expert clinical grading, and subjective questionnaires.

RESULTS

Results showed that the OS-01 formulation significantly improved one aspect of skin barrier function, as evidenced by reduced trans-epidermal water loss compared to both baseline and vehicle control. Expert grading and Antera 3D image analysis revealed a reduction in wrinkle appearance and indentation in the periorbital area, and improved skin texture and radiance on both sides of the face, with the OS-01-containing formulation demonstrating superior results. Participants also perceived improvements in skin hydration, smoothness, radiance, and overall appearance.

CONCLUSION

The findings suggest that the OS-01 formulation promotes skin health by strengthening the skin barrier, protecting against dehydration, reducing the appearance of wrinkles, and improving skin texture and radiance. These effects are likely attributed to the senotherapeutic properties of OS-01 in reducing cellular senescence and its associated detrimental effects.

The potential for senotherapy as a novel approach to extend life quality in veterinary medicine

Cellular senescence, a condition where cells undergo arrest and can assume an inflammatory phenotype, has been associated with initiation and perpetuation of inflammation driving multiple disease processes in rodent models and humans. Senescent cells secrete inflammatory cytokines, proteins, and matrix metalloproteinases, termed the senescence associated secretory phenotype (SASP), which accelerates the aging processes. In preclinical models, drug interventions termed "senotherapeutics" selectively clear senescent cells and represent a promising strategy to prevent or treat multiple age-related conditions in humans and veterinary species. In this review, we summarize the current available literature describing in vitro evidence for senotheraputic activity, preclinical models of disease, ongoing human clinical trials, and potential clinical applications in veterinary medicine. These promising data to date provide further justification for future studies identifying the most active senotherapeutic combinations, dosages, and routes of administration for use in veterinary medicine.

Cellular senescence and wound healing in aged and diabetic skin

Cellular senescence is a biological mechanism that prevents abnormal cell proliferation during tissue repair, and it is often accompanied by the secretion of various factors, such as cytokines and chemokines, known as the senescence-associated secretory phenotype (SASP). SASP-mediated cell-to-cell communication promotes tissue repair, regeneration, and development. However, senescent cells can accumulate abnormally at injury sites, leading to excessive inflammation, tissue dysfunction, and intractable wounds. The effects of cellular senescence on skin wound healing can be both beneficial and detrimental, depending on the condition. Here, we reviewed the functional differences in cellular senescence that emerge during wound healing, chronic inflammation, and skin aging. We also review the latest mechanisms of wound healing in the epidermis, dermis, and subcutaneous fat, with a focus on cellular senescence, chronic inflammation, and tissue regeneration. Finally, we discuss the potential clinical applications of promoting and inhibiting cellular senescence to maximize benefits and minimize detrimental effects.

Fisetin, a potential skin rejuvenation drug that eliminates senescent cells in the dermis

Accumulation of senescent fibroblasts, chronic inflammation, and collagen remodeling due to aging-related secretory phenotypes have been hypothesized to cause age-related skin aging, which results in wrinkles and loss of skin elasticity, thus compromising appearance attractiveness. However, the rejuvenating effects of removing senescent cells from the human skin and the efficacy of related therapeutic agents remain unclear. Here, we investigated the effects of fisetin, a potential anti-aging component found in various edible fruits and vegetables, on senescent human dermal fibroblasts (HDFs) and aging human skin. Senescence was induced in primary HDFs using long-term passaging and treatment with ionizing radiation, and cell viability was assessed after treatment with fisetin and a control component. A mouse/human chimeric model was established by subcutaneously transplanting whole skin grafts from aged individuals into nude mice, which were treated intraperitoneally with fisetin or control a component for 30 d. Skin samples were obtained and subjected to senescence-associated-beta-galactosidase staining; the extent of aging was evaluated using western blotting, reverse transcription-quantitative PCR, and histological analysis. Fisetin selectively eliminated senescent dermal fibroblasts in both senescence-induced cellular models; this effect is attributable to cell death induction by caspases 3, 8, and 9-mediated endogenous and exogenous apoptosis. Fisetin-treated senescent human skin grafts showed increased collagen density and decreased senescence-associated secretory phenotypes (SASP), including matrix metalloproteinases and interleukins. No apparent adverse events were observed. Thus, fisetin could improve skin aging through selective removal of senescent dermal fibroblasts and SASP inhibition, indicating its potential as an effective novel therapeutic agent for combating skin aging.

Cellular senescence and frailty: a comprehensive insight into the causal links

Senescent cells may have a prominent role in driving inflammation and frailty. The impact of cellular senescence on frailty varies depending on the assessment tool used, as it is influenced by the criteria or items predominantly affected by senescent cells and the varying weights assigned to these items across different health domains. To address this challenge, we undertook a thorough review of all available studies involving gain- or loss-of-function experiments as well as interventions targeting senescent cells, focusing our attention on those studies that examined outcomes based on the individual frailty phenotype criteria or specific items used to calculate two humans (35 and 70 items) and one mouse (31 items) frailty indexes. Based on the calculation of a simple "evidence score," we found that the burden of senescent cells related to musculoskeletal and cerebral health has the strongest causal link to frailty. We deem that insight into these mechanisms may not only contribute to clarifying the role of cellular senescence in frailty but could additionally provide multiple therapeutic opportunities to help the future development of a desirable personalized therapy in these extremely heterogeneous patients.

Identification of resibufogenin, a component of toad venom, as a novel senolytic compound in vitro and for potential skin rejuvenation in male mice

Senescent cells that accumulate with age have been shown to contribute to age-related diseases and organ dysfunction and have attracted attention as a target for anti-aging therapy. In particular, the use of senescent cell-depleting agents, or senolytics, has been shown to improve the aging phenotype in animal models. Since senescence has been implicated in the skin, particularly in fibroblasts, this study used aged human skin fibroblasts to investigate the effects of resibufogenin. A component of the traditional Chinese medicine toad venom, resibufogenin was investigated for senolytic and/or senomorphic activity. We found that the compound selectively caused senescent cell death without affecting proliferating cells, with a marked effect on the suppression of the senescence-associated secretory phenotype. We also found that resibufogenin causes senescent cell death by inducing a caspase-3-mediated apoptotic program. Administration of resibufogenin to aging mice resulted in an increase in dermal collagen density and subcutaneous fat, improving the phenotype of aging skin. In other words, resibufogenin ameliorates skin aging through selective induction of senescent cell apoptosis without affecting non-aged cells. This traditional compound may have potential therapeutic benefits in skin aging characterized by senescent cell accumulation.

Cistanche deserticola Polysaccharide Reduces Inflammation and Aging Phenotypes in the Dermal Fibroblasts through the Activation of the NRF2/HO-1 Pathway

Dermal fibroblasts maintain the skin homeostasis by interacting with the epidermis and extracellular matrix. Their senescence contributes to functional defects in the skin related to aging. Therefore, there is an urgent need for novel therapeutic agents that could inhibit fibroblast senescence. In this study, we investigated the effects of Cistanche deserticola polysaccharide (CDP), a natural anti-inflammatory component, on the progression of senescence in human dermal fibroblasts. Normal human dermal fibroblasts (NHDFs) were cultured in passages, and highly senescent cells were selected as senescent cells. CDP treatment increased the cell proliferation in senescent NHDFs and decreased the proportion of senescence-associated-β-galactosidase-positive cells. The treatment suppressed the senescence-related secretory phenotype, and reactive oxygen species (ROS) production was reduced, alleviating H2O2-induced oxidative stress. CDP mitigated ROS formation via the nuclear factor erythroid 2-related factor/heme oxygenase-1 pathway in senescent cells and was involved in the suppression of upstream p-extracellular signal-regulated kinase. These results indicate that CDP is an antioxidant that can alleviate age-related inflammation and may be a useful compound for skin anti-aging.

[Skin aging-cellular senescence : What is the future?]

BACKGROUND

Cellular senescence is the main cause of skin and organ aging and is associated with a wide range of aging-related diseases.

OBJECTIVES

To understand which senolytics, senomorphics, and cell-based therapies have been developed to alleviate and even rejuvenate skin aging and reduce cellular senescence.

METHODS

Basic literature for the mode of action of senolytics and senomorphics and their clinical perspectives in daily routine are discussed.

RESULTS

Various causes lead to mitochondrial dysfunction and the activation of pro-aging signaling pathways, which eventually lead to cellular senescence with degradation of structural proteins of the dermal connective tissue and severe suppression of regenerative stem cell niches of the skin.

CONCLUSIONS

Depletion of senescent cells suppress skin aging and enforce rejuvenation of skin and other organs and their function. The removal of senescent cells by cells of the native immune system is severely disturbed during aging. Selected senolytics and senomorphics are approved and are already on the market.

Development of a Novel Senolysis Approach Targeting the Senescent Fibroblast Marker HTR2A via Antibody-Dependent Cellular Cytotoxicity

Abnormal remodeling of collagen and extracellular matrix caused by the accumulation of senescent fibroblasts in the dermis is the most likely cause of skin aging. Therefore, the application of "senolysis," in which only senescent cells are cleared from the body, has a potential in the development of antiaging treatments for skin. However, markers that label senescent fibroblasts only reflect the state of senescence, and it is important to develop markers as therapeutic targets to aid senolysis application. We investigated the potential of serotonin 2A receptor (HTR2A), which is involved in melanin production in response to ultraviolet light, as a senescent cell marker. The results showed that HTR2A is upregulated in aging dermal fibroblasts but is expressed at low levels in proliferating young cells. Flow cytometry demonstrated the presence of many HTR2A-positive cells in the aging cell population and few in the young cells. Furthermore, antibody-dependent cytotoxicity assays revealed that HTR2A preferentially sensitizes senescent fibroblasts and specifically damages only senescent cells by natural killer cells that recognize it. In conclusion, selective labeling of the novel senescent cell marker, HTR2A, could preferentially eliminate senescent cells and may contribute to the future development of novel skin senolysis approaches.

Cellular senescence in skin-related research: Targeted signaling pathways and naturally occurring therapeutic agents

Despite the growing interest by researchers into cellular senescence, a hallmark of cellular aging, its role in human skin remains equivocal. The skin is the largest and most accessible human organ, reacting to the external and internal environment. Hence, it is an organ of choice to investigate cellular senescence and to target root-cause aging processes using senolytic and senomorphic agents, including naturally occurring plant-based derivatives. This review presents different aspects of skin cellular senescence, from physiology to pathology and signaling pathways. Cellular senescence can have both beneficial and detrimental effects on the skin, indicating that both prosenescent and antisenescent therapies may be desirable, based on the context. Knowledge of molecular mechanisms involved in skin cellular senescence may provide meaningful insights for developing effective therapeutics for senescence-related skin disorders, such as wound healing and cosmetic skin aging changes.

Skin aging from mechanisms to interventions: focusing on dermal aging

Skin aging is a multifaceted process that involves intrinsic and extrinsic mechanisms that lead to various structural and physiological changes in the skin. Intrinsic aging is associated with programmed aging and cellular senescence, which are caused by endogenous oxidative stress and cellular damage. Extrinsic aging is the result of environmental factors, such as ultraviolet (UV) radiation and pollution, and leads to the production of reactive oxygen species, ultimately causing DNA damage and cellular dysfunction. In aged skin, senescent cells accumulate and contribute to the degradation of the extracellular matrix, which further contributes to the aging process. To combat the symptoms of aging, various topical agents and clinical procedures such as chemical peels, injectables, and energy-based devices have been developed. These procedures address different symptoms of aging, but to devise an effective anti-aging treatment protocol, it is essential to thoroughly understand the mechanisms of skin aging. This review provides an overview of the mechanisms of skin aging and their significance in the development of anti-aging treatments.

Topical Application of Peptide Nucleic Acid Antisense Oligonucleotide for MMP-1 and Its Potential Anti-Aging Properties

Matrix metalloproteinase-1 (MMP-1) is a zinc-containing endopeptidase that degrades dermal collagen and other extracellular matrix molecules. It is recognized as one of the most important indicators of cellular senescence and age-related skin changes. Here, we introduced a novel MMP-1 peptide nucleic acid (PNA) derivative-PNA-20 carboxyethyl fluorene (CEF)-which can interact with and consequently silence the MMP-1 gene sequence. The investigation on the efficacy of PNA-20 CEF in MMP-1 silencing in human dermal fibroblasts revealed significantly decreased expression of MMP-1 at both gene and protein levels. Treatment with PNA-20 CEF showed significantly increased expression of collagen I protein, indicating its potential role in preventing the degradation of collagen I and consequently combating the skin aging process. Its topical application on 3D human skin tissue showed successful absorption into the epidermis and the upper dermis. Furthermore, the additional 4-week single-arm prospective study on 21 Asian women revealed improvements in facial wrinkles, skin moisture, elasticity, and density after the use of the topical PNA-20 CEF cosmeceutical formulation. Additional in-vitro and ex-vivo studies are needed for a comprehensive understanding of the skin anti-aging effects of MMP-1 PNA.

Fat infiltration into dermal layer induces aged facial appearance by decreasing dermal elasticity

BACKGROUND

Facial morphology changes with aging, producing an aged appearance, but the mechanisms involved are not fully established. We recently showed that subcutaneous fat infiltrates into the dermal layer with aging, but it is not yet clear whether and how this drastic change of the dermal layer influences facial appearance.

PURPOSE

We aimed to establish the role of fat infiltration in producing an aged facial appearance and to clarify the mechanism involved.

METHODS

We analyzed the severity of fat infiltration in cheek skin of 30 middle-aged female volunteers by means of ultrasonography. Severity of the nasolabial fold, an established age-related morphology, was evaluated based on our photographic grading criteria as a measure of aged appearance. Skin elasticity was measured with a Cutometer.

RESULTS

Fat infiltration to the dermal layer was detected at the cheek skin noninvasively by means of ultrasonography. Fat infiltration severity, measured as the minimum depth of the fat inside the dermal layer from the skin surface, was positively correlated with the magnitude of the nasolabial fold. Further, fat infiltration severity was significantly negatively correlated with dermal elasticity.

CONCLUSIONS

Our results suggest that fat infiltration into the dermal layer is a critical factor inducing aged appearance of the face. The infiltrated fat decreases the dermal elasticity, which exacerbates nasolabial folds, namely producing an aged facial appearance.

Cathepsin F is a potential marker for senescent human skin fibroblasts and keratinocytes associated with skin aging

Cellular senescence is characterized by cell cycle arrest and the senescence-associated secretory phenotype (SASP) and can be triggered by a variety of stimuli, including deoxyribonucleic acid (DNA) damage, oxidative stress, and telomere exhaustion. Cellular senescence is associated with skin aging, and identification of specific markers of senescent cells is essential for development of targeted therapies. Cathepsin F (CTSF) has been implicated in dermatitis and various cancers and participates in cell immortalization through its association with Bcl family proteins. It is a candidate therapeutic target to specifically label and eliminate human skin fibroblasts and keratinocytes immortalized by aging and achieve skin rejuvenation. In this study, we investigated whether CTSF is associated with senescence in human fibroblasts and keratinocytes. In senescence models, created using replicative aging, ionizing radiation exposure, and the anticancer drug doxorubicin, various senescence markers were observed, such as senescence-associated β-galactosidase (SA-β-gal) activity, increased SASP gene expression, and decreased uptake of the proliferation marker BrdU. Furthermore, CTSF expression was elevated at the gene and protein levels. In addition, CTSF-positive cells were abundant in aged human epidermis and in some parts of the dermis. In the population of senescent cells with arrested division, the number of CTSF-positive cells was significantly higher than that in the proliferating cell population. These results suggest that CTSF is a candidate for therapeutic modalities targeting aging fibroblasts and keratinocytes.

Skin-Aging Pigmentation: Who Is the Real Enemy?

Skin aging is induced and sustained by chronological aging and photoaging. Aging skin pigmentation such as mottled pigmentation (senile lentigo) and melasma are typical signs of photoaging. The skin, like other human organs, undergoes cellular senescence, and senescent cells in the skin increase with age. The crosstalk between melanocytes as pigmentary cells and other adjacent types of aged skin cells such as senescent fibroblasts play a role in skin-aging pigmentation. In this review, we provide an overview of cellular senescence during the skin-aging process. The discussion also includes cellular senescence related to skin-aging pigmentation and the therapeutic potential of regulating the senescence process.

Human placental extract activates a wide array of gene expressions related to skin functions

As skin aging is one of the most common dermatological concerns in recent years, scientific research has promoted treatment strategies aimed at preventing or reversing skin aging. Breakdown of the extracellular matrix (ECM), such as collagen and elastin fibers, in the skin results in decreased skin elasticity and tension. Cutaneous cells, especially fibroblasts in the dermis layer of the skin, mainly produce ECM proteins. Although clinical studies have demonstrated that placental extract (PE) has positive effects on skin health, the molecular mechanisms by which PE acts against skin aging are still largely unknown. In this study, we performed RNA-sequence analysis to investigate whether human PE (HPE) alters ECM-related gene expression in normal human dermal fibroblast (NHDF) cells. Gene ontology analysis showed that genes related to extracellular matrix/structure organization, such as COL1A1, COL5A3, ELN, and HAS2 were highly enriched, and most of these genes were upregulated. We further confirmed that the HPE increased the type I collagen, proteoglycan versican, elastin, and hyaluronan levels in NHDF cells. Our results demonstrate that HPE activates global ECM-related gene expression in NHDF cells, which accounts for the clinical evidence that the HPE affects skin aging.

Inhibition of matrix metalloproteinase expression by selective clearing of senescent dermal fibroblasts attenuates ultraviolet-induced photoaging

Photoaging mainly occurs due to ultraviolet (UV) radiation, and is accompanied by increased secretion of matrix metalloproteinases (MMPs) and degradation of collagen. UV radiation induces cell senescence in the skin; however, the role of senescent cells in photoaging remains unclear. Therefore, to elucidate the role of senescent cells in photoaging, we evaluated the effect of senolytics in a photoaging mouse model and investigated the underlying mechanism of their antiaging effect. Both UV-induced senescent human dermal fibroblasts and a photoaging mouse model, ABT-263 and ABT-737, demonstrated senolytic effects on senescent fibroblasts. Moreover, we found that several senescence-associated secretory phenotype factors, such as IL-6, CCL5, CCL7, CXCL12, and SCF, induced MMP-1 expression in dermal fibroblasts, which decreased after treatment with ABT-263 and ABT-737 in vivo and in vitro. Both senolytic drugs attenuated the induction of MMPs and decreased collagen density in the photoaging mouse model. Our data suggest that senolytic agents reduce UV-induced photoaging, making strategies for targeting senescent dermal fibroblasts promising options for the treatment of photoaging.