(1) Background: Calcium transfer between the endoplasmic reticulum (ER) and mitochondria through the IP3R-VDAC1 complex at mitochondria-associated ER membranes (MAMs) is essential for cellular homeostasis. Alterations in this signalling axis have been implicated in ageing and cellular senescence. (2) Methods: We developed an in vitro human dermal fibroblast (HDF) model combining replicative senescence and acute oxidative stress to investigate the role of ER-mitochondria coupling in skin ageing and to enable biomolecule screening. (3) Results: In situ proximity ligation assays revealed that replicative senescence significantly increased the number of VDAC1/IP3R complexes per cell (+85% and +72%, p < 0.01), together with elevated cellular reactive oxygen species (+47% and +74%, p < 0.05). Consistently, acute oxidative stress (50 µM t-BHP, 30 min) rapidly increased VDAC1/IP3R complexes (+48%, p < 0.001) and intra-mitochondrial calcium levels (+19%, p < 0.001). These effects persisted for 24 h post-treatment and were associated with impaired mitochondrial function (-27% in the Bioenergetic Health Index, p < 0.05). We also established a flexibility index capturing both acute and long-term adaptations and detecting the protective effects of an orchid extract. (4) Conclusions: ER-mitochondria coupling disruption via the IP3R-VDAC1 complex may contribute to oxidative stress-induced senescence and represent a key mechanism in extrinsic skin ageing.

Human skin homeostasis relies on the delicate equilibrium between epidermal stem cell renewal, dermoepidermal junction (DEJ) architecture, and environmental interactions. With aging and exposure to external stressors, this equilibrium becomes disrupted, leading to reduced regenerative capacity. In this study, we established an ex vivo human skin model to examine the impact of dry and tropical (hot and humid) environmental conditions on epidermal homeostasis and to evaluate the protective potential of Kombucha tea extract, a fermented tea known for its antioxidant and regenerative properties. Histological analyses revealed that tropical conditions induced pronounced epidermal thickening (+157%) and disruption of the normal undulating architecture of the DEJ. Atomic force microscopy demonstrated a loss of mechanical contrast between dermal papillae and epidermal ridges, indicative of junctional flattening (-61 and -81%). At the molecular level, heat and humidity upregulated a stem cell marker (+85%) and collagen VII (+39%), reflecting an adaptive but potentially destabilizing activation of basal keratinocytes and matrix reorganization. Topical application of Kombucha tea extract counteracted these effects. Together, these results highlight the sensitivity of epidermal stem cell niches to heat and humidity stress and identify Kombucha tea extract as a promising bioactive agent to preserve epidermal homeostasis under challenging climatic conditions.

OBJECTIVE:Human skin is a highly dynamic organ capable of sensing and responding to mechanical stimuli through tightly regulated communication between the epidermis and dermis. Daily mechanical forces-such as stretching and compression-modulate skin structure and function via mechanotransduction pathways. Central to this process are the mechanosensitive Piezo channels, which convert mechanical tension into electrochemical signals. While the role of Piezo channels in epidermal keratinocytes has been established, it remains unclear whether mechanical tension at the skin's surface can influence deeper dermal responses. METHODS:In this study, we examined whether Piezo-mediated mechanotransduction in keratinocytes affects fibroblast activity and extracellular matrix (ECM) remodelling in the dermis. We applied controlled mechanical tension to the skin surface by the application of cosmetic products on the stratum corneum and measured key features of fibroblast activity and dermal matrix composition. RESULTS:We showed that generating surface tension-induced mechanotransduction in keratinocytes is consistent with the activation of Piezo channels and molecular changes in markers from distinct compartments, including the epidermal protein E-cadherin and dermal ECM proteins such as fibronectin and collagen III. These alterations suggest activation of downstream signalling pathways that may influence dermal fibroblasts, leading to remodelling of key ECM proteins including fibronectin and collagen III, while elastin levels remained unchanged. CONCLUSION:Our findings support the hypothesis that mechanical cues at the epidermal level, sensed via Piezo channels, may participate in interlayer communication and be associated with ECM remodelling in the dermis, supporting the hypothesis of a potential epidermis-to-dermis mechanotransduction axis in human skin.

The ability to monitor cellular processes in real-time is essential for understanding cell function, disease progression, and therapeutic responses. Engineered reporter proteins have been developed for monitoring cellular metabolism, stress responses, and bioenergetics. However, their use in primary cells is limited by inefficient plasmid transfection and the impracticality of generating and validating stable cell lines for each application. Here, we use in vitro transcription to generate mRNA-encoded metabolic trackers and achieve high transfection efficiencies in primary fibroblasts, cancer cells, and induced pluripotent stem cells. This approach provides a flexible platform for real-time monitoring of cellular processes in diverse cell types and overcomes the technical barriers of establishing stable cell lines by genetic modification. We confirm the activity of three ratiometric reporters that monitor pH, H2O2, and ATP levels in subcellular compartments. Our mRNA-based approach provides a versatile, efficient tool for real-time metabolic studies across basic and applied research, reducing reliance on commercially available reporters and broadening the applicability of metabolic reporters in patient-derived cell models.

Like with skin, both men and women—regardless of ethnicity—gradually lose satisfaction with changes in hair brought about by ageing. Especially when such transition is apparent by others, and that the hair condition has a significant role in an individual’s overall physical appearance and self-perception. Beyond the familiar age-related signs such as hair greying, hair loss, and hair fragility, this review includes current knowledge of biological processes underlying hair pigmentation and hair growth, highlights variations in gender and ethnicity, as well as delineates hair fibre diameter, ellipticity, and elasticity properties that collectively contribute to the characteristics of aged hair. Additionally, in view of the rising importance of enhancing scalp skin health to promote healthy hair growth, the latter part of the review focuses on age-associated alterations to the scalp skin and its microbiome. Consideration of the morphological changes in the hair fibre, biological processes occurring within the hair follicle and its enveloping scalp environment provide a unique, holistic overview of hair and scalp changes during ageing. Finally, after acknowledging the impact caused by chronological ageing and environmental stresses, it is important to recognise that healthy tresses are largely influenced by scalp skin care, and this stimulates the advancement of appropriate cosmetic solutions that help delay or improve the appearance of aged hair.

Accumulating evidence indicates that biological aging can be accelerated by environmental exposures, collectively called the ‘exposome’. The skin, as the largest and most exposed organ, can be viewed as a ‘window’ for the deep exploration of the exposome and its effects on systemic aging. The complex interplay across hallmarks of aging in the skin and systemic biological aging suggests that physiological processes associated with skin aging influence, and are influenced by, systemic hallmarks of aging. This bidirectional relationship provides potential avenues for the prevention of accelerated biological aging and the identification of therapeutic targets. We provide a review of the interactions between skin exposure, aging hallmarks in the skin and associated systemic changes, and their implications in treatment and disease. We also discuss key questions that need to be addressed to maintain skin and overall health, highlighting the need for the development of precise biomarkers and advanced skin models. This Review examines how hallmarks of aging manifest in the skin and interact with systemic aging, positioning the skin as both an indicator and driver of age-related physiological decline.

Resting natural killer (NK) cells display immediate effector functions after recognizing transformed or infected cells. The environmental nutrients and metabolic requirements to sustain these functions are not fully understood. Here, we show that NK cells rely on the use of extracellular pyruvate to support effector functions, signal transduction and cell viability. Glucose-derived carbons do not generate endogenous pyruvate. Consequently, NK cells import extracellular pyruvate that is reduced to lactate to regenerate glycolytic NAD+ and is oxidized in the tricarboxylic acid (TCA) cycle to produce ATP. This supports serine production through phosphoglycerate dehydrogenase, a pathway required for optimal proliferation following cytokine stimulation but dispensable for effector functions. In addition, like mouse NK cells, human NK cells rely on a citrate–malate configuration of the TCA cycle that is not fed by glutamine. Moreover, supraphysiologic pyruvate concentrations dose-dependently increase the effector functions of NK cells. Overall, this study highlights the role of exogenous pyruvate in NK cell biology, providing knowledge that could be exploited to boost NK cell potential in therapeutic settings. Kern Coquillat et al. show that NK cells rely on exogenous pyruvate import to support effector functions.

Advanced skin models are critical for pursuing non-animal approaches in drug and cosmetic testing. However, existing 3D models remain complex and time-consuming, which limits their adoption. Spherical skin model (SSM) is presented, a platform that balances biological fidelity with experimental robustness. The SSM is based on a core-shell structure where the dermal core is modeled by embedding human fibroblasts into collagen microcarriers (150  μ m $\mu{\rm m}$ ), while the epidermal shell is formed by outer layers of immortalized keratinocytes. The collagen beads are generated using droplet microfluidics to enable rapid and reproducible production. The biological relevance of SSM is revealed through elevated expression of epidermal differentiation markers (loricrin, involucrin, keratin 1, keratin 10) and the dermal-epidermal junction marker collagen VII. The barrier function is validated by permeability assays that show strong exclusion of fluorescent dextran above 4 kDa. Moreover, their usefulness for screening is shown by identifying a dose-dependent effect of vitamins in reducing oxidative stress and apoptosis against tert-butyl hydroperoxide. As such, this 3D microphysiological model recapitulates key structural, molecular, and functional features of human skin while offering rapid generation, scalability, and compatibility with high-throughput applications in dermatological and cosmetic research.

Elastic fibers are well-known extracellular matrix components that are essential for elastic properties and thus function of many tissues. Tropoelastin is encoded by the ELN gene which is the main component of the elastic fibers. Elastic fibers decrease with aging and this decrease is proposed to contribute to this process. Senescent cells, cells that stop to proliferate and that instruct their microenvironment, accumulate with aging and promote it. Until recently, whether ELN expression and function is linked to cellular senescence was unknown. Here we will comment and extend recent results supporting a function of the ELN gene in protecting cells from cellular senescence. We will also discuss hypotheses on mechanisms by which ELN could regulate cellular senescence, and especially a hypothesis that involves a non-canonical function of ELN regulating the mitochondrial respiratory chain activity, thereby controlling oxidative stress and cellular senescence. These findings provide critical insights into the molecular and cellular processes potentially underlying the phenotypes driven by ELN deletion in the context of aging.

Reactive oxygen species (ROS) and mitochondrial dysfunction play a major role in skin aging. Due to Tropaeolum majus’ suggested protective actions against ROS, a link between T. majus extract and increased cytoglobin (CYGB) expression was evaluated for cultured skin cells. Human dermal fibroblasts and keratinocytes were treated with 0.5% v/v T. majus extract and the effect of this treatment on the expression of CYGB and on a range of cellular markers of aging were evaluated. In fibroblasts, the treatment with the extract was associated with an increase in CYGB levels. It also decreased ROS concentrations, improved the function of mitochondria, and stimulated the synthesis of collagen and elastin. Moreover, it downregulated a set of genes controlling the terminal differentiation of keratinocytes. T. majus extract activates oxygen transport within natural killer cells and thus enhances their activity, suggesting a potential senolytic effect. This extract seemed to exert a protective effect on various aging pathways such as ROS production, mitochondrial dysfunction, and collagen homeostasis, playing a promising role against skin aging.

OBJECTIVE:Existing methods to evaluate skin care products suffer limitations. This is the case for ex vivo skin explants, a first-choice 3D model. While essential to analyse mid- to long-term biological effects, this classical model hinders assessing microrelief variations. To circumvent these limitations, we developed an ex vivo PERFused EXplant setup (Perfex) that maintains the outer skin surface in the open air, closely mirroring physiological conditions. METHODS:A custom-designed reservoir enables perfusing the dermal side of explants with buffered, temperature-controlled medium, while the epidermis is subjected to "normal" conditions. Skin tension and characteristics of the stratum corneum, microrelief, histology and immunohistology (collagen types I and III, elastin and fibrillin-1) were analysed and compared to those of explants maintained under conventional conditions or in vivo skin. The effects of skin care formulas intended to induce short- and/or mid- to long-term effects were also assessed. RESULTS:Skin explants maintained with the Perfex setup exhibit characteristics (firmness, elasticity, hydration and barrier function) closer to those of in vivo skin than with conventional conditions. Moreover, Perfex-maintained explants present no alteration in histology after 7 days and slight variation in the expression of key protein markers. Microrelief characteristics also remain mostly stable over 7 days. Formula applications corroborate that skin tensor-containing products primarily induce short-term changes in the microrelief, while those with biologically active ingredients mainly lead to mid- to long-term effects on the histology and expression of molecular markers. Furthermore, maintaining skin explants with a physiologically relevant skin surface enabled analysing the relationship between microrelief and key markers, showing that fibrillin-1 is the protein most correlated with microrelief characteristics. CONCLUSIONS:The Perfex setup allows for similar preservation of skin explant histology and key protein expression as the conventional system, yet it maintains a skin surface close to that of in vivo skin. Therefore, it is valuable to analyse both the short- and mid- to long-term impacts of skin care formulas and better comprehend their effects. The Perfex system also offers a new tool for investigating fundamental questions, such as the link that can exist between dermal proteins and skin surface properties.

Objective: Many severe acute respiratory infections are caused by viral pathogens, and viruses are responsible for a large number of deaths worldwide. Among the most common respiratory viruses are the influenza A virus (IAV) and, more recently, the SARS-CoV-2 that emerged in 2019 and caused the most significant human pandemic of the beginning of the 21st century. Both IAV and SARS-CoV-2 share clinical features and a common transmission route through the emission of viral particles via aerosols and droplets. These penetrate the host after entry from the nose and mouth or an indirect mode of transmission via contact contamination of different media. These facts prompted us to investigate the possibility of designing a soft cream with a virucidal activity targeted against IAV and SARS-CoV-2. Methods: We first investigated the action of chemical compounds known to have antiviral properties such as cyclodextrin, or algae extracts containing sulfated polysaccharides, on cultured cells infected with lentiviral viral particles pseudotyped (VP) with either proteins HA (hemagglutinin) and NA (neuraminidase) from IAV or the G protein from the vesicular stomatitis virus or spike-bearing particles in order to select molecules with antiviral activities in human embryonic kidney (HEK293T) cells. Results: Our results show that some cyclodextrin-containing creams can significantly reduce the stability of HANA- and spike-bearing particles when they are applied prior to challenge with a viral inoculum on skin. Conclusions: We observed some specificities of these creams towards either IAV or SARS-CoV-2, indicating that the neutralization of viral activity is correlated with the mechanism of receptor interaction and entry of these two pathogens.

This work reports on the demonstration of the penetration of cosmetic active ingredients (caffeine and hyaluronic acid) in human skin explants following safe and controlled plasma jet exposure. First, temperature increase and immunohistochemistry in the stratum corneum and epidermis were characterized to check the safe delivery of plasma jets and to select two operation regimes at 1 and 20 kHz. Plasma exposure for tens of seconds is shown to induce transient modulations of skin pH, transepidermal water loss, and skin wettability, revealing a reversible skin barrier function modulation. Then, it is demonstrated that plasma exposure significantly accelerates the penetration of active ingredients. The tuning of the plasma jet pulse repetition rate allows controlling the penetration kinetics. Such ex vivo results agree with previous in vitro experiments also exhibiting a transient permeabilization time window. A preliminary demonstration of human skin wettability modulation with a low-power, user-friendly dielectric barrier discharge setup is documented, opening perspectives for plasma-based home cosmetic care device development. To the best of our knowledge, this work is one of the first demonstrations of safe and controlled plasma-assisted active ingredients’ skin penetration in the context of cosmetic applications.

Objective: This study explored the impact of a black tea extract obtained through (plant small RNA) PSR (TM) technology, characterized by its abundance of small molecules, particularly citric acid-an antioxidant and tricarboxylic acid (TCA) cycle contributor-on mitochondrial health. The primary focus was to assess whether this extract could counteract reactive oxygen species (ROS)-induced mitochondrial alterations associated with aging, which lead to impaired mitochondrial function, reduced ATP production, and increased ROS generation. Methods: The PSR (TM) extraction method was employed to obtain a high content of polyphenols and small molecules, particularly citric acid. Results: In comparison with a conventional extract, the PSRTM extract demonstrated significant enhancements in aconitase activity, an ROS-sensitive enzyme in the TCA cycle, as well as basal respiration and ATP synthesis in fibroblast cells and skin biopsies. Moreover, the PSR (TM) extract effectively reduced ROS production by safeguarding this critical enzyme within the Krebs cycle and displayed superior capabilities in scavenging free radicals when exposed to UV-induced stress. When administered post-UV exposure, the PSR (TM) extract protected nuclear DNA by reducing the formation of cyclobutane pyrimidine dimers (CPDs) and promoting DNA repair mechanisms. Furthermore, the extract exhibited beneficial effects on the extracellular matrix, characterized by a reduction in matrix metalloprotease 1 (MMP1) and an increase in fibrillin 1 expression. Conclusions: These findings collectively suggest that the PSR (TM) extract holds promising antiaging potential, potentially functioning as a mitochondrial nutrient/protector due to its multifaceted benefits on mitochondrial function, nuclear DNA integrity, and the extracellular matrix.