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.

Combined dasatinib and quercetin treatment contributes to skin rejuvenation through selective elimination of senescent cells in vitro and in vivo.

The skin's protective functions are compromised over time by both endogenous and exogenous aging. Senescence is well-documented in skin phenotypes, such as wrinkling and sagging, a consequence of the senescence-associated secretory phenotype (SASP) that involves the accumulation of senescent fibroblasts, chronic inflammation, and collagen remodeling. Although therapeutic approaches for eliminating senescent cells from the skin are available, their efficacy remains unclear. Accordingly, we aimed to examine the effects of dasatinib in combination with quercetin (D + Q) on senescent human skin fibroblasts and aging human skin. Senescence was induced in human dermal fibroblasts (HDFs) using approaches such as long-term passaging, ionizing radiation, and doxorubicin treatment. The generated senescent cells were treated with D + Q or vehicle. Additionally, a mouse-human chimera model was generated by subcutaneously transplanting whole-skin grafts of aged individuals onto nude mice. Mouse models were administered D + Q or vehicle by oral gavage for 30 days. Subsequently, skin samples were harvested and stained for senescence-associated beta-galactosidase. Senescence-associated markers were assessed by western blotting, reverse transcription-quantitative PCR and histological analyses. Herein, D + Q selectively eliminated senescent HDFs in all cellular models of induced senescence. Additionally, D + Q-treated aged human skin grafts exhibited increased collagen density and suppression of the SASP compared with control grafts. No adverse events were observed during the study period. Collectively, D + Q could ameliorate skin aging through selective elimination of senescent dermal fibroblasts and suppression of the SASP. Our findings suggest that D + Q could be developed as an effective therapeutic approach for combating skin aging.

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.

Treatment of Cicatricial Lower Eyelid Ectropion with Suture of Horner Muscle Combined with Fascia Transplantation.

This case series aimed to describe a new technique for correcting contractures and deformities that reliably addresses lacrimal punctum deviation and severe cicatricial lower eyelid ectropion. This was a technical description and a retrospective interventional case series. Eyelid ectropion and lacrimal punctum deviation were treated surgically by grafting the fascia lata and suturing the tarsus-Horner muscle. In total, three patients underwent this surgery: one for burns, one for lower eyelid tumor resection, and the other for an orbital floor fracture following a motorcycle accident, all resulting in ectropion. All patients previously had failed ectropion correction procedures, including scar revision, skin grafting, auricular cartilage grafting, and lateral tarsal strips. The mean follow-up was 15.8 (12.5-18.5) months. Furthermore, all patients showed resolution of lower eyelid ectropion and significant improvement in lower eyelid contracture, with a mean increase of 4.0 (2.5-5) mm. No severe complications were observed, and they reported a significant improvement in ocular surface symptoms. Our study shows that tacking of the tarsus and Horner muscles in combination with fascia lata grafting is effective in correcting refractory cicatricial lower eyelid ectropion with deviation of the tear punctum.

Twist2 contributes to skin regeneration and hair follicle formation in mouse fetuses.

Unlike adult mammalian wounds, early embryonic mouse skin wounds completely regenerate and heal without scars. Analysis of the underlying molecular mechanism will provide insights into scarless wound healing. Twist2 is an important regulator of hair follicle formation and biological patterning; however, it is unclear whether it plays a role in skin or skin appendage regeneration. Here, we aimed to elucidate Twist2 expression and its role in fetal wound healing. ICR mouse fetuses were surgically wounded on embryonic day 13 (E13), E15, and E17, and Twist2 expression in tissue samples from these fetuses was evaluated via in situ hybridization, immunohistochemistry, and reverse transcription-quantitative polymerase chain reaction. Twist2 expression was upregulated in the dermis of E13 wound margins but downregulated in E15 and E17 wounds. Twist2 knockdown on E13 left visible marks at the wound site, inhibited regeneration, and resulted in defective follicle formation. Twist2-knockdown dermal fibroblasts lacked the ability to undifferentiate. Furthermore, Twist2 hetero knockout mice (Twist + /-) formed visible scars, even on E13, when all skin structures should regenerate. Thus, Twist2 expression correlated with skin texture formation and hair follicle defects in late mouse embryos. These findings may help develop a therapeutic strategy to reduce scarring and promote hair follicle regeneration.

Salicylate induces epithelial actin reorganization via activation of the AMP-activated protein kinase and promotes wound healing and contraction in mice.

Wounds that occur in adults form scars due to fibrosis, whereas those in embryos regenerate. If wound healing in embryos is mimicked in adults, scarring can be reduced. We found that mouse fetuses could regenerate tissues up to embryonic day (E) 13, but visible scars remained thereafter. This regeneration pattern requires actin cable formation at the epithelial wound margin via activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK). Here, we investigated whether the AMPK-activating effect of salicylate, an anti-inflammatory drug, promotes regenerative wound healing. Salicylate administration resulted in actin cable formation and complete wound regeneration in E14 fetuses, in which scarring should have normally occurred, and promoted contraction of the panniculus carnosus muscle, resulting in complete wound regeneration. In vitro, salicylate further induced actin remodeling in mouse epidermal keratinocytes in a manner dependent on cell and substrate target-specific AMPK activation and subsequent regulation of Rac1 signaling. Furthermore, salicylate promoted epithelialization, enhanced panniculus carnosus muscle contraction, and inhibited scar formation in adult mice. Administration of salicylates to wounds immediately after injury may be a novel method for preventing scarring by promoting a wound healing pattern similar to that of embryonic wounds.

Tunneling nanotube-driven complete regeneration of murine fetal skin.

This study investigated the three-dimensional (3D) cellular interactions and tunneling nanotubes (TNTs) during fetal mouse skin regeneration on embryonic days 13 (E13) and 15 (E15). We aimed to understand spatial relationships among cell types involved in skin regeneration and assess the potential role of TNTs. Full-thickness skin incisions were performed in E13 and E15 embryos. Wound sites were collected, embedded in epoxy resin, processed for 3D reconstruction (1 µm thickness sections), and subjected to whole-mount immunostaining. We conducted in vitro co-culture experiments with fetal macrophages and fibroblasts to observe TNT formation. To assess the effect of TNTs on skin regeneration, an inhibiting agent (cytochalasin B) was administered to amniotic fluid. Results revealed that E13 epidermal keratinocytes interacted with dermal fibroblasts and macrophages, facilitating skin regrowth. TNT structures were observed at the E13-cell wound sites, among macrophages, and between macrophages and fibroblasts, confirmed through in vitro co-culture experiments. In vitro and utero cytochalasin B administration hindered those formation and inefficient skin texture regeneration at E13 wound sites. This emphasizes the necessity of 3D cellular interactions between epidermal and dermal cells during skin regeneration in mouse embryos at E13. The prevalence of TNT structures indicated their involvement in achieving complete skin texture restoration.

Regeneration of Panniculus Carnosus Muscle in Fetal Mice Is Characterized by the Presence of Actin Cables.

Mammalian skin, including human and mouse skin, does not regenerate completely after injury; it is repaired, leaving a scar. However, it is known that skin wounds up to a certain stage of embryonic development can regenerate. The mechanism behind the transition from regeneration to scar formation is not fully understood. Panniculus carnosus muscle (PCM) is present beneath the dermal fat layer and is a very important tissue for wound contraction. In rodents, PCM is present throughout the body. In humans, on the other hand, it disappears and becomes a shallow fascia on the trunk. Fetal cutaneous wounds, including PCM made until embryonic day 13 (E13), regenerate completely, but not beyond E14. We visualized the previously uncharacterized development of PCM in the fetus and investigated the temporal and spatial changes in PCM at different developmental stages, ranging from full regeneration to non-regeneration. Furthermore, we report that E13 epidermal closure occurs through actin cables, which are bundles of actomyosin formed at wound margins. The wound healing process of PCM suggests that actin cables may also be associated with PCM. Our findings reveal that PCM regenerates through a similar mechanism.