BACKGROUND: Our facial skin hosts millions of microorganisms, primarily bacteria, crucial for skin health by maintaining the physical barrier, modulating immune response, and metabolizing bioactive materials. Aging significantly influences the composition and function of the facial microbiome, impacting skin immunity, hydration, and inflammation, highlighting potential avenues for interventions targeting aging-related facial microbes amidst changes in skin physiological properties.
RESULTS: We conducted a multi-center and deep sequencing survey to investigate the intricate interplay of aging, skin physio-optical conditions, and facial microbiome. Leveraging a newly-generated dataset of 2737 species-level metagenome-assembled genomes (MAGs), our integrative analysis highlighted aging as the primary driver, influencing both facial microbiome composition and key skin characteristics, including moisture, sebum production, gloss, pH, elasticity, and sensitivity. Further mediation analysis revealed that skin characteristics significantly impacted the microbiome, mostly as a mediator of aging. Utilizing this dataset, we uncovered two consistent cutotypes across sampling cities and identified aging-related microbial MAGs. Additionally, a Facial Aging Index (FAI) was formulated based on the microbiome, uncovering the cutotype-dependent effects of unhealthy lifestyles on skin aging. Finally, we distinguished aging related microbial pathways influenced by lifestyles with cutotype-dependent effect.
CONCLUSIONS: Together, our findings emphasize aging\'s central role in facial microbiome dynamics, and support personalized skin microbiome interventions by targeting lifestyle, skin properties, and aging-related microbial factors. Video Abstract.

BACKGROUND: Patients with Parkinson\'s Disease (PD) have a distinctive body odor, which was first described by a patient\'s wife as musky and strong. Later analysis of sebum of patients with PD revealed four volatile organic compounds (VOC) (perillic aldehyde, hippuric acid, eicosane, octadecanal), that differed from healthy subjects, and the patient\'s wife confirmed that three of them smelled like patients with PD. However, it is unclear whether other people can also perceive this PD body odor and whether it can be artificially recreated. Hence, we aimed to systematically assess whether young women can perceive the PD body odor and whether they can discriminate between the PD body odor and the \"artificial PD odor\" composed of the four VOCs mentioned above.
METHODS: T-shirts were collected from 19 people with idiopathic PD and 15 age- and gender-matched healthy participants to represent the PD body odor and the healthy body odor, respectively. The four VOCs were diluted in 1,2-propanediol to prepare the artificial PD body odor. Body odors were rated by 26 young women.
RESULTS: PD body odor was perceived as more musty, strong, smelly, and unpleasant compared to healthy and artificial PD body odor. Furthermore, around 80 % of women were able to discriminate PD body odor from artificial PD body odor.
CONCLUSIONS: Overall, this study confirmed a distinctive body odor quality of patients with PD, which can be perceived by young women. However, the four VOCs, composing the artificial PD body odor, were insufficient to reproduce the body odor from PD patients.

BACKGROUND: Acne vulgaris (AV) is a widespread inflammatory skin condition associated with increased sebum production, abnormal keratinization, bacterial overgrowth, and inflammation. Overactive sebaceous glands (SGs) produce excess sebum, promote Cutibacterium acnes growth, and affect acne development. Energy-based treatments (EBDs), including light therapy, photodynamic therapy (PDT), lasers, and radiofrequency (RF) devices, have emerged as effective treatment options. As the use of EBDs becomes more widespread, it is imperative to understand their effects on skin parameters, such as sebum, in AV.
METHODS: Searches were conducted in Embase, PubMed, Web of Science, and the Cochrane Library. The studies included were randomized and nonrandomized trials on facial AV that used EBDs and featured objective casual sebum level (CSL) measurements via Sebumeter. Data synthesis involved percentage reductions in CSL at follow-ups compared to baseline.
RESULTS: Twenty-three studies were analyzed. PDT and RF consistently reduced CSL by 30%-40% and 30%-35%, respectively. Laser therapy showed lesser reductions, whereas light therapy varied significantly and studies had a high risk of bias. All EBD therapies were more effective than no treatment and PDT was superior to light monotherapy. Laser therapy combined with fractional microneedling radiofrequency (FMR) or as a standalone was more effective than laser alone.
CONCLUSIONS: Noninvasive sebum measurement provides valuable insights into AV treatment efficacy. PDT, lasers, especially the 1450-nm diode laser, and FMR are promising for reducing sebum. Standardization of measurement techniques and further research are vital for enhancing treatment personalization, reducing side effects, and improving AV management.

BACKGROUND: It is known that tropospheric ozone (O3) generated from pollutants reacting with UV forms lipid peroxidation products and induces oxidative stress to the skin. With the ever-increasing consumer awareness of the effects pollution has on skin, more testing methods will be needed to evaluate cosmetic ingredients. Recently, others have shown how antioxidants are able to reduce the effects from ozone on skin through in vitro, ex vivo and clinical studies where human subjects place their arms into large stationary chambers.
OBJECTIVE: To develop a small, easy to use ozone exposure module (OEM) that can be used on various sites of the body and to validate this device for use in testing the ability of topical products to mitigate the effects of ozone exposure on the skin.
METHODS: We have produced an OEM which can generate levels of ozone in excess of 1000 ppb and can be set to achieve the equivalent exposure to what is found in polluted environmental conditions. After exposure we used D-squame discs to remove the sebum and analytically quantitate squalene depletion. Squalene, which is very sensitive to ROS, easily oxidizes into early metabolite squalene monohydroperoxide (SQOOH) with ozone exposure.
RESULTS: We were able to show decreases in squalene levels after exposure and protective effects from a topical formulation.
CONCLUSIONS: This generator will be a useful tool for researchers to easily create a small and safe exposure from ozone for clinical testing.
BACKGROUND: On sait que l’ozone troposphérique (O3) générée par les polluants réagissant avec les UV forme des produits de peroxydation lipidique et induit un stress oxydatif pour la peau. Avec la sensibilisation croissante des consommateurs aux effets de la pollution sur la peau, plus de méthodes d’analyse seront nécessaires pour évaluer les ingrédients cosmétiques. Récemment, d’autres méthodes ont montré la capacité des antioxydants à réduire les effets de l’ozone sur la peau grâce à des études in vitro, ex vivo et cliniques où les sujets humains placent leurs bras dans de grandes chambres stationnaires.
OBJECTIVE: Développer un petit module d’exposition à l’ozone (MEO) facile à utiliser qui peut être utilisé sur divers sites corporels afin de valider ce dispositif pour utilisation dans des analyses de capacité des produits topiques à atténuer les effets de l’exposition à l’ozone sur la peau MATÉRIELS ET MÉTHODES: Nous avons produit un MEO qui peut générer des niveaux d’ozone supérieurs à 1 000 ppb et qui peut être réglé pour atteindre l’exposition équivalente aux niveaux présents dans des conditions d’environnement pollué. Après exposition, nous avons utilisé des disques D‐squame pour éliminer le sébum et quantifier analytiquement la déplétion en squalène. Le squalène, qui est très sensible au ROS, s’oxyde facilement en métabolite précoce monohydroperoxyde de squalène (SQOOH) avec exposition à l’ozone RÉSULTATS: Nous avons pu montrer des diminutions des taux de squalène après exposition et les effets protecteurs d’une formulation topique.
CONCLUSIONS: Ce générateur sera un outil utile pour que les chercheurs puissent facilement créer une petite exposition sûre à l’ozone pour les analyses cliniques.

BACKGROUND: Skincare and makeup \"pilling\" is an unsightly and undesirable phenomenon whereby skincare such as moisturizers or foundation ball up to form flakes on the skin. To date, the causes of skincare product pilling have not been studied. This study aimed to examine the relationship between skin physiology and pilling potential of sunscreen and foundation (the two products most reported by consumers to cause pilling). This study also examined the effects of product application methods on pilling.
METHODS: 528 female volunteers from Guangzhou, China, aged between 20 and 49 years, underwent various clinical skin assessments, followed by three steps of product layering. Pilling was assessed after each product application step.
RESULTS: 217 volunteers (41%) experienced pilling. The majority of pilling (n = 655 events) occurred following sunscreen application, while only a few pilling events (n = 35) occurred with foundation. Foundation improved pilling caused by sunscreen in 98.9% of cases. Volunteers experiencing pilling with both sunscreen and foundation had significantly lower facial skin hydration and oiliness, higher pH, and smoother skin texture (P < 0.05). Two application methods, rubbing of products in circular and linear motions, yielded the highest numbers of pilling events.
CONCLUSIONS: This study has provided the first insights into the causes of pilling. Sunscreen is a promoter of pilling, while foundation may resolve sunscreen-induced pilling in many cases. Skin physiology, particularly drier, smoother skin with higher pH, and product application methods are likely contributing factors to this undesirable phenomenon.

Acne vulgaris is a complex condition involving factors that affect the pilosebaceous unit. A primary manifestation of acne pathology is the development of comedones, often linked to the overproduction of sebum resulting from 5α-dihydrotestosterone (5α-DHT) and insulin activity. Ozenoxacin is a topical quinolone that exhibits potent antibacterial activity against Cutibacterium acnes (C. acnes). It is commonly used to treat acne associated with this bacterium; however, its effect on sebum production within the sebaceous glands remains unclear. In this study, the effects of ozenoxacin on sebum production were examined using insulin- and 5α-DHT-differentiated hamster sebocytes. Ozenoxacin showed a dose-dependent inhibition of lipid droplet formation and triacylglycerol (TG) production, which is a major component of sebum. In addition, it suppressed the expression of diacylglycerol acyltransferase 1, stearoyl-CoA desaturase-1, and perilipin-1 mRNA, all important factors involved in sebum synthesis, in a dose-dependent manner. Moreover, ozenoxacin decreased phosphorylated 40S ribosomal protein S6 levels downstream of the mechanistic/mammalian target of rapamycin complex 1 (mTORC1), without altering the phosphorylation of Akt, an upstream regulator of mTORC1, in both insulin- and 5α-DHT-treated hamster sebocytes. Interestingly, nadifloxacin, but not clindamycin, exhibited a similar suppression of sebum production, albeit with lesser potency compared with ozenoxacin. Furthermore, a topical application of a 2% ozenoxacin-containing lotion to the auricle skin of hamsters did not affect the size of the sebaceous glands or epidermal thickness. Notably, it decreased the amount of TG on the skin surface. The results provide novel insights into the sebum-inhibitory properties of ozenoxacin, indicating its potential efficacy in controlling microbial growth and regulating sebum production for acne management.

The skin surface is an important sample source that the metabolomics community has only just begun to explore. Alterations in sebum, the lipid-rich mixture coating the skin surface, correlate with age, sex, ethnicity, diet, exercise, and disease state, making the skin surface an ideal sample source for future noninvasive biomarker exploration, disease diagnosis, and forensic investigation. The potential of sebum sampling has been realized primarily via electrospray ionization mass spectrometry (ESI-MS), an ideal approach to assess the skin surface lipidome. However, a better understanding of sebum collection and subsequent ESI-MS analysis is required before skin surface sampling can be implemented in routine analyses. Challenges include ambiguity in definitive lipid identification, inherent biological variability in sebum production, and methodological, technical variability in analyses. To overcome these obstacles, avoid common pitfalls, and achieve reproducible, robust outcomes, every portion of the workflow-from sample collection to data analysis-should be carefully considered with the specific application in mind. This review details current practices in sebum sampling, sample preparation, ESI-MS data acquisition, and data analysis, and it provides important considerations in acquiring meaningful lipidomic datasets from the skin surface. Forensic researchers investigating sebum as a means for suspect elimination in lieu of adequate fingerprint ridge detail or database matches, as well as clinical researchers interested in noninvasive biomarker exploration, disease diagnosis, and treatment monitoring, can use this review as a guide for developing methods of best-practice.

Cutibacterium acnes is an opportunistic pathogen recognized as a contributing factor to acne vulgaris. The accumulation of keratin and sebum plugs in hair follicles facilitates C. acnes proliferation, leading to inflammatory acne. Although numerous antimicrobial cosmetic products for acne-prone skin are available, their efficacy is commonly evaluated against planktonic cells of C. acnes. Limited research has assessed the antimicrobial effects on microorganisms within keratin and sebum plugs. This study investigates whether an antibacterial toner can penetrate keratin and sebum plugs, exhibiting bactericidal effects against C. acnes. Scanning electron microscopy and next-generation sequencing analysis of the keratin and sebum plug suggest that C. acnes proliferate within the plug, predominantly in a biofilm-like morphology. To clarify the potential bactericidal effect of the antibacterial toner against C. acnes inside keratin and sebum plugs, we immersed the plugs in the toner, stained them with LIVE/DEAD BacLight Bacterial Viability Kit to visualize microorganism viability, and observed them using confocal laser scanning microscopy. Results indicate that most microorganisms in the plugs were killed by the antibacterial toner. To quantitatively evaluate the bactericidal efficacy of the toner against C. acnes within keratin and sebum, we immersed an artificial plug with inoculated C. acnes type strain and an isolate collected from acne-prone skin into the toner and obtained viable cell counts. The number of the type strain and the isolate inside the artificial plug decreased by over 2.2 log and 1.2 log, respectively, showing that the antibacterial toner exhibits bactericidal effects against C. acnes via keratin and sebum plug penetration.

Acne vulgaris (AV), characterized by excessive sebum production and Cutibacterium acnes proliferation in the sebaceous glands, significantly impacts physical and psychological health. Recent treatment advancements have focused on selective photothermolysis of sebaceous glands. This review evaluates two innovative therapies: the 1726-nm laser and nanoparticle-assisted laser treatments. We conducted a comprehensive search of PubMed and Embase using the primary terms \"acne vulgaris\" or \"acne\" AND \"laser,\" \"photothermal therapy,\" \"nanoparticles,\" \"treatment,\" or \"1726 nm laser.\" Inclusion criteria were articles published in English in peer-reviewed journals that focused on treating AV through targeting the sebaceous glands, yielding 11 studies. Gold nanoparticles, used with 800-nm laser, 1064-nm Nd: YAG laser, or photopneumatic device, and platinum nanoparticles with 1450-nm diode laser, showed notable improvements in severity and number of acne lesions, safety, and patient satisfaction. The 1726-nm laser treatments also showed considerable lesion reduction and tolerability, with minimal side effects such as erythema and edema. Its efficiency is credited to its short, high-power pulses that effectively target sebaceous glands, offering precise treatment with fewer side effects compared to lower-power pulses. Selective photothermolysis using nanoparticle-assisted laser therapy or the 1726-nm laser offers a promising alternative to conventional AV treatments, showcasing efficacy and high patient satisfaction. The 1726-nm laser streamlines treatment but involves new equipment costs, while nanoparticle-assisted therapy integrates well into existing setups but relies on external agents and is unsuitable for certain allergies. Future research should include long-term studies and comparative analyses. The choice of treatment modality should consider patient preferences, cost implications, and availability of specific therapies.

BACKGROUND: Acne vulgaris is a species-specific human disease. To date, there has been no established human sebocyte cell line of Asian origin. Our previous study has demonstrated the efficacy of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) in the treatment of acne vulgaris, primarily attributed to its cytotoxic properties; however, its regulatory mechanism remains largely unknown.
OBJECTIVE: To establish an immortalized human sebocyte cell line derived from Chinese population and investigate the underlying mechanism of ALA-PDT.
METHODS: Human primary sebocytes were transfected with the human tert gene (h‑tert). The biological characteristics, including cell proliferation, cell markers, and sebum secretion function, were compared between primary sebocytes and the immortalized sebocytes (XL-i-20). Stimulations such as ALA-PDT, were applied respectively to both primary sebocytes and XL-i-20 cells to assess changes in their cellular functions. The transcriptome differences between primary sebocytes and XL-i-20 sebocytes were investigated using RNA-seq analysis. The XL-i-20 cell line was used to establish a sebaceous gland (SG) organoid culture, serving as a representative model of SG for the investigation of ALA-PDT.
RESULTS: The h‑tert immortalized sebocyte cell line exhibited the ability to be consecutively cultured for more than fifty passages. Both primary and immortalized cells expressed sebocyte markers such as epithelial membrane antigens (EMA, or MUC-1), Cytokeratin 7 (CK7) and adipose differentiation-related protein associated antigens (ADRP), and maintained sebum secretion function. The proliferative capacity of XL-i-20 was found to be significantly higher than that of primary sebocytes. The responses of XL-i-20 to ALA-PDT were indistinguishable from those elicited by primary sebocytes. Cell viability and sebum secretion were decreased after ALA-PDT in both two cell lines, and lipid-related proteins (SREBP-1/PPARγ) were down-regulated. The transcriptome data consistently demonstrated upregulation of genes related to inflammatory responses and downregulation of genes involved in lipid metabolism in both cell types following PDT. The analysis of common differential genes of primary sebocytes and XL-i-20 sebocytes post ALA-PDT showed that TNF signaling pathways, MAPK signaling pathways and JAK-STAT signaling pathways were activated. The SG organoids were spherical, which expressed markers of FANS and PLET1. Ki-67 was down-regulated after ALA-PDT.
CONCLUSIONS: We have developed an h‑tert immortalized sebocyte cell line from an Asian population. The cell line, XL-i-20, maintains the essential characteristics of its parent primary sebocytes. Moreover, XL-i-20 sebocyte exhibited a significant respond to ALA-PDT, demonstrating comparable phenotypic and molecular changes to primary sebocytes. Therefore, XL-i-20 and its derived SG organoid serve as appropriate in vitro models for investigating the efficacy and mechanisms of ALA-PDT in SG-related diseases.