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.

This review presents several aspects of the innovative concept of sebaceous immunobiology, which summarizes the numerous activities of the sebaceous gland including its classical physiological and pathophysiological tasks, namely sebum production and the development of seborrhea and acne. Sebaceous lipids, which represent 90% of the skin surface lipids in adolescents and adults, are markedly involved in the skin barrier function and perifollicular and dermal innate immune processes, leading to inflammatory skin diseases. Innovative experimental techniques using stem cell and sebocyte models have clarified the roles of distinct stem cells in sebaceous gland physiology and sebocyte function control mechanisms. The sebaceous gland represents an integral part of the pilosebaceous unit and its status is connected to hair follicle morphogenesis. Interestingly, professional inflammatory cells contribute to sebocyte differentiation and homeostasis, whereas the regulation of sebaceous gland function by immune cells is antigen-independent. Inflammation is involved in the very earliest differentiation changes of the pilosebaceous unit in acne. Sebocytes behave as potent immune regulators, integrating into the innate immune responses of the skin. Expressing inflammatory mediators, sebocytes also contribute to the polarization of cutaneous T cells towards the Th17 phenotype. In addition, the immune response of the perifollicular infiltrate depends on factors produced by the sebaceous glands, mostly sebaceous lipids. Human sebocytes in vitro express functional pattern recognition receptors, which are likely to interact with bacteria in acne pathogenesis. Sex steroids, peroxisome proliferator-activated receptor ligands, neuropeptides, endocannabinoids and a selective apoptotic process contribute to a complex regulation of sebocyte-induced immunological reaction in numerous acquired and congenital skin diseases, including hair diseases and atopic dermatitis.

BACKGROUND: Botanical ingredients are widely used in hair- and skin-care products. However, few studies have investigated the effectiveness of botanical products on counteracting sebum synthesis and secretion.
OBJECTIVE: To investigate the composition of Lotus corniculatus seed extract (LC) and its potential inhibition of lipogenesis in SZ95 sebocytes and oily human skin.
METHODS: The active components of LC solutions were identified by high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). The in vitro effects of LC were evaluated using SZ95 cells treated with linoleic acid (LA) and dihydrotestosterone (DHT) and incubated with LCs for 24 h and 72 h. Lipogenesis was assessed by Oil Red O and Nile Red staining of the cells. In vivo effects were assessed on 30 subjects with oily skin who were enrolled in a randomized, blank-controlled trial and were treated with LC solution for 6 h and 4 weeks. The skin sebum contents and area on the forehead and cheeks were evaluated using a Sebumeter SM815 and Sebfix sebutape with Visioscan VC98. In addition, VISIA was used to collect half-face photos for analysis.
RESULTS: A novel active molecule, 5\'-o-rhamnosyl uridine, was identified in LC. LC exhibited a dose-dependent inhibitory effect on LA and DHT-induced lipid synthesis. When 5% LC was applied for 3 h, the skin sebum contents and area were significantly reduced compared with the vehicle control, with an obvious reduction after 6 h. Continued use of the serum containing 5% LC for 4 weeks resulted in a significant reduction in the skin sebum contents and area. No adverse reactions were reported during the study.
CONCLUSIONS: Topical application of LC resulted in an immediate and long-lasting reduction of the sebum contents and area of oily human skin by reducing sebaceous lipogenesis through the LA and DHT pathways. This indicates the potential of LC as a new biological treatment for oily skin.
BACKGROUND: Les ingrédients végétaux sont largement utilisés dans les produits de soins des cheveux et de la peau. Cependant, peu d\'études ont examiné l\'efficacité des produits végétaux dans l\'inhibition de la synthèse et de la sécrétion de sébum.
OBJECTIVE: Étudier les composants de l\'extrait de graines de lotus (LC) et son effet inhibiteur potentiel sur la lipogenèse des cellules sébacées SZ95 et de la peau grasse. MÉTHODES: Les composants actifs de la solution LC ont été identifiés par chromatographie liquide à haute performance (HPLC) et par résonance magnétique nucléaire (NMR). Les effets de la LC in vitro ont été évalués à l\'aide de cellules SZ95 traitées à l\'acide linoléique (LA) et à la dihydrotestostérone (DHT) et incubées avec la LC pendant 24 et 72 heures. Les effets in vivo ont été évalués chez 30 sujets à peau grasse qui ont participé à un essai contrôlé randomisé à blanc et qui ont été traités avec une solution de LC pendant 6 heures et 4 semaines. Le sebumeter SM815 et le sebfix sebutape et le visioscan VC98 ont été utilisés pour évaluer la teneur en sébum et la surface de la peau sur le front et les joues. De plus, des photos de demi - visage ont été recueillies pour analyse à l\'aide de VISIA. RÉSULTATS: Une nouvelle molécule active, 5′-o-rhamnosyluridine, a été identifiée dans la LC. La LC a un effet inhibiteur dose - dépendant sur la synthèse lipidique induite par LA et DHT. La teneur et la surface du sébum cutané ont été significativement diminuées par rapport à celles du support photographique après 3 heures d\'application de 5% de LC, et significativement diminuées après 6 heures. L\'utilization de sérum contenant 5% de LC pendant quatre semaines consécutives a entraîné une réduction significative de la teneur en sébum et de la surface de la peau. Aucun effet indésirable n\'a été signalé au cours de l\'étude.
CONCLUSIONS: L\'application topique de LC peut réduire la production de sébum par les voies LA et DHT, ce qui réduit immédiatement et durablement la teneur en sébum et la surface de la peau huileuse humaine. Cela démontre le potentiel de la LC en tant que nouveau traitement biologique de la peau huileuse.

Acne vulgaris is a prevalent cutaneous disease characterized by a multifactorial pathogenic process including hyperseborrhea, inflammation, over-keratinization of follicular keratinocytes and Propionibacterium acnes (P acnes) overgrowth. Salicylic acid (SA), a beta-hydroxy acid, is frequently used in the treatment of acne. SA has been found to decrease skin lipids and to possess anti-inflammatory properties. However, few studies have elucidated the mechanisms and pathways involved in such treatment of acne. In this study, we initially investigated the anti-acne properties of SA in human SEB-1 sebocytes. Treatment with SA decreased sebocyte lipogenesis by downregulating the adenosine monophosphate-activated protein kinase (AMPK)/sterol response element-binding protein-1 (SREBP-1) pathway and reduced inflammation by suppressing the NF-κB pathway in these cells. Salicylic acid also decreased the cell viability of SEB-1 by increasing apoptosis via the death signal receptor pathway. Subsequently, histopathological analysis of a rabbit ear acne model after application of SA for three weeks confirmed that SA suppressed the levels of cytokines and major pathogenic proteins around acne lesions, which supports the mechanisms suggested by our in vitro experiments. These results initially clarified that therapeutic activities of SA in acne vulgaris treatment could be associated with the regulation of SREBP-1 pathway and NF-κB pathway in human SEB-1 sebocytes.

Acne vulgaris is a cutaneous chronic inflammatory disorder with complex pathogenesis. Four factors play vital roles in acne pathophysiology: hyperseborrhea and dysseborrhea, altered keratinization of the pilosebaceous duct, Cutibacterium acnes (C. acnes) and inflammation. The main hormones responsible for the development of acne vulgaris include androgens, insulin and insulin-like growth factor-1. Other factors involved in this process are corticotropin-releasing hormone, α-melanocyte-stimulating hormone and substance P. Wnt/β-catenin signaling pathway, phosphoinositide 3-kinase (PI3K)/Akt pathway, mitogen-activated protein kinase pathway, adenosine 5\'-monophosphate-activated protein kinase pathway and nuclear factor kappa B pathway participate in the modulation of sebocyte, keratinocyte and inflammatory cell (e.g. lymphocytes, monocytes, macrophages, neutrophils) activity. Among all the triggers and pathways mentioned above, IGF-1-induced PI3K/Akt/Forkhead box protein O1/mammalian target of rapamycin (mTOR) C1 pathway is the most important signaling responsible for acne pathogenesis. Commonly used anti-acne agents include retinoids, benzoyl peroxide, antibiotics and hormonal agents (e.g. spironolactone, combination oral contraceptive and flutamide). New approaches including peroxisome proliferator-activated receptor γ modifier, melanocortin receptor antagonists, epigallocatechin-3-gallate, metformin, olumacostat glasaretil, stearoyl-CoA desaturase inhibitor omiganan pentahydrochloride, KDPT, afamelanotide, apremilast and biologics have been developed as promising treatments for acne vulgaris. Although these anti-acne agents have various pharmacological effects against the diverse pathogenesis of acne, all of them have a synergistic mode of action, the attenuation of Akt/mTORC1 signaling and enhancement of p53 signal transduction. In addition to drug therapy, diet with no hyperglycemic carbohydrates, no milk and dairy products is also beneficial for treatment of acne.

BACKGROUND: The transcription factor Sox9 is pivotal in the morphogenesis of hair follicles, but its role in sebocytes is poorly understood.
OBJECTIVE: We investigated the effect of Sox9 on human sebocyte proliferation, differentiation and lipogenesis.
METHODS: Sox9 expression was detected by immunohistochemistry in normal skin and acne lesion. Primary cultured human sebocytes were transfected with adenovirus expressing GFP-Sox9 or Sox9 microRNA. Sox9 and peroxisome proliferator-activated receptor (PPAR)γ expression in sebocytes was detected by quantitative real-time PCR, Western blot and immunocytofluorescence; cell proliferation was measured by MTS and [3H]-thymidine incorporation assays; cell cycle distribution and apoptosis were evaluated by propidium iodide staining-based flow cytometry; and intracellular lipid levels were assessed by Oil Red O stain.
RESULTS: Sox9 immunostaining was increased in mature sebocytes of acne lesion compared with normal skin. Expression of Sox9 mRNA and protein and PPARγ protein was elevated with cell confluent levels in sebocytes. Sox9 overexpression enhanced proliferation, differentiation, proportion of S and G2/M cells, lipogenesis and PPARγ expression in sebocytes, while Sox9 silencing caused inhibition of differentiation, lipogenesis and PPARγ expression, and increase of G1 and sub-G1 (apoptotic) cell fraction. The suppression of Sox9 knockdown on sebocyte growth was observed using [3H]-thymidine incorporation but not MTS assay.
CONCLUSIONS: These results demonstrate that Sox9 can reinforce sebocyte proliferation, differentiation and lipogenesis. The G1/S transition arrest and apoptotic induction might contribute to inhibitory effect of Sox9 silencing on sebocyte proliferation.

The sebaceous gland is most commonly found in association with a hair follicle. Its traditional function is the holocrine production of sebum, a complex mixture of lipids, cell debris, and other rather poorly characterized substances. Due to the gland\'s central role in acne pathogenesis, early research had focused on its lipogenic activity. Less studied aspects of the sebaceous gland, such as stem cell biology, the regulation of cellular differentiation by transcription factors, the significance of specific lipid fractions, the endocrine and specially the neuroendocrine role of the sebaceous gland, and its contribution to the innate immunity, the detoxification of the skin, and skin aging have only recently attracted the attention of researchers from different disciplines. Here, we summarize recent multidisciplinary progress in sebaceous gland research and discuss how sebaceous gland research may stimulate the development of novel therapeutic strategies targeting specific molecular pathways of the pathogenesis of skin diseases.