Follicular unit grafting in chronic ulcers: a valuable technique for integrated management

Abstract Chronic ulcers significantly affect the quality of life of patients and impose a high cost on the healthcare system. The therapeutic management should be comprehensive, taking into consideration the etiological diagnosis of the wound and the characteristics of the wound bed when deciding on a therapeutic proposal appropriate to the healing phase, correcting factors that delay healing. During the epithelialization phase, repair techniques with grafts are recommended to shorten re-epithelialization time, improve the quality of scar tissue, and achieve adequate pain management. Currently, due to the reported benefits of skin appendages, the technique of follicular unit auto-grafting obtained with a scalp punch is among the chosen strategies for wound repair. This is a minimally invasive, outpatient practice, whose technique has advantages over the donor site, patients recovery and well-being.

LncRNA RP11-818O24.3 promotes hair-follicle recovery via FGF2-PI3K/Akt signal pathway.

A previous study indicated that patients with androgenic alopecia (AGA) have significantly reduced levels of LncRNA RP11-818O24.3. This study investigates whether LncRNA RP11-818O24.3 promotes hair-follicle recovery and its possible mechanism. Hair alteration and cutaneous histopathological changes induced by testosterone propionate were observed by H&E and bromodeoxyuridinc (BrdU) stain to evaluate the therapeutic effect of LncRNA RP11-818O24.3 in C57BL/6 J mice. The cellular viability was analyzed in LncRNA RP11-818O24.3-transfected human hair-follicle stem cells (HFSCs) in vitro. The signaling pathways and pro-proliferative factors were investigated by transcriptomic gene sequencing and qRT-PCR. LncRNA RP11-818O24.3 transfection successfully recovered hair growth and hair-follicle cells in AGA mice. In a series of HFSC studies in vitro, LncRNA RP11-818O24.3 transfection greatly promoted cellular proliferation and decreased cellular apoptosis. Transcriptome gene sequencing suggested that the phosphatidylinositol 3-kinase (PI3K)-Akt pathway was upregulated by LncRNA RP11-818O24.3. The qRT-PCR results showed that fibroblast growth factor (FGF)-2 was 14-times upregulated after LncRNA RP11-818O24.3 transfection. Hair-follicle recovery activity of LncRNA RP11-818O24.3 may involve the upregulation of FGF2 and PI3K-Akt to promote follicle stem cell survival. These data not only provide a theoretical basis for AGA development but also reveal a novel therapeutic method for AGA patients. Supplementary Information: The online version contains supplementary material available at 10.1007/s10616-024-00624-3.

Hair follicles modulate skin barrier function.

Our skin provides a protective barrier that shields us from our environment. Barrier function is typically associated with the interfollicular epidermis; however, whether hair follicles influence this process remains unclear. Here, we utilize a potent genetic tool to probe barrier function by conditionally ablating a quintessential epidermal barrier gene, Abca12, which is mutated in the most severe skin barrier disease, harlequin ichthyosis. With this tool, we deduced 4 ways by which hair follicles modulate skin barrier function. First, the upper hair follicle (uHF) forms a functioning barrier. Second, barrier disruption in the uHF elicits non-cell-autonomous responses in the epidermis. Third, deleting Abca12 in the uHF impairs desquamation and blocks sebum release. Finally, barrier perturbation causes uHF cells to move into the epidermis. Neutralizing IL-17a, whose expression is enriched in the uHF, partially alleviated some disease phenotypes. Altogether, our findings implicate hair follicles as multi-faceted regulators of skin barrier function.

Adult hair follicle stem cells differentiate into neuronal cells in explanted rat intestinal tissue.

Hair follicle stem cells (HFSCs) are adult stem cells located in the outer root sheath of the follicle bulge with high neural plasticity, which promise a potential for the stem cell therapy for neurological diseases. Hirschsprung's disease (HD) is characterized by the absence of ganglia in the distant bowel. In this study, we elucidated the capacity of HFSCs to differentiate into neuronal cells in the aganglionic colon from embryonic rat. HFSCs were isolated from adult Sprague-Dawley (SD) rats and formed spheres that could be passaged. The cultured HFSCs expressed neural crest stem cells (NCSCs) markers such as SOX10, CD34, and nestin, which indicated their neural crest lineage. Subsequent differentiation assays demonstrated that these cells could give rise to neural progeny that expressed neuronal or glial markers. The aganglionic colon from the embryonic intestine was applied as in vitro explant to test the capacity of proliferation and differentiation of HFSCs. The HFSCs expressing GFP or RFP integrated in intestinal explants and maintained proliferative capacity. Moreover, the HFSCs differentiated into Tuj1- or S100ß-positive cells in the cultured intestinal explants. The results proposed that the HFSCs might be an alternative source of neural stem cells for the HD therapy.

DNA methylation of microRNA-365-1 induces apoptosis of hair follicle stem cells by targeting DAP3.

Background: DNA methylation is a crucial epigenetic alteration involved in diverse biological processes and diseases. Nevertheless, the precise role of DNA methylation in chemotherapeutic drug-induced alopecia remains unclear. This study examined the role and novel processes of DNA methylation in regulating of chemotherapeutic drug-induced alopecia. Methods: A mouse model of cyclophosphamide (CTX)-induced alopecia was established. Hematoxylin-eosin staining and immunohistochemical staining for the Ki67 proportion and a mitochondrial membrane potential assay (JC-1) were performed to assess the structural integrity and proliferative efficiency of the hair follicle stem cells (HFSCs). Immunofluorescence staining and real-time fluorescence quantitative PCR (RT-qPCR) were performed to determine the expression levels of key HFSC markers, namely Lgr5, CD49f, Sox9, CD200, and FZD10. Differential DNA methylation levels between the normal and CTX-induced model groups were determined through simple methylation sequencing and analyzed using bioinformatics tools. The expression levels of miR-365-1, apoptosis markers, and DAP3 were detected through RT-qPCR and western blotting. In parallel, primary mouse HFSCs were extracted and used as a cell model, which was constructed using 4-hydroperoxycyclophosphamide. The luciferase reporter gene assay was conducted to confirm miR-365-1 binding to DAP3. To measure the expression of relevant indicators, superoxide dismutase (SOD) and malondialdehyde (MDA) kits were used. Methylation-specific PCR (MS-PCR) was performed to determine DNA methylation levels. The regulatory relationship within HFSCs was confirmed through plasmid overexpression of miR-365-1 and DAP3. Result: In the alopecia areata model, a substantial number of apoptotic cells were observed within the hair follicles on the mouse backs. Immunofluorescence staining revealed that the expression of HFSC markers significantly reduced in the CTX group. Both RT-qPCR and western blotting demonstrated a noteworthy difference in DNA methyltransferase expression. Simple methylation sequencing unveiled that DNA methylation substantially increased within the dorsal skin of the CTX group. Subsequent screening identified miR-365-1 as the most differentially expressed miRNA. miR-365-1 was predicted and confirmed to bind to the target gene DAP3. In the CTX group, SOD and ATP expression markedly reduced, whereas MDA levels were significantly elevated. Cellular investigations revealed 4-HC-induced cell cycle arrest and decreased expression of HFSC markers. MS-PCR indicated hypermethylation modification of miR-365-1 in the 4-HC-induced HFSCs. The luciferase reporter gene experiment confirmed the binding of miR-365-1 to the DAP3 promoter region. miR-365-1 overexpression dramatically reduced apoptotic protein expression in the HFSCs. However, this effect was slightly reversed after DAP3 overexpression in lentivirus. Conclusion: This study explored the occurrence of miR-365-1 DNA methylation in chemotherapeutic drug-induced alopecia. The results unveiled that miR-365-1 reduces cell apoptosis by targeting DAP3 in HFSCs, thereby revealing the role of DNA methylation of the miR-365-1 promoter in chemotherapeutic drug-induced alopecia.

Follicular unit grafting in chronic ulcers: a valuable technique for integrated management.

Chronic ulcers significantly affect the quality of life of patients and impose a high cost on the healthcare system. The therapeutic management should be comprehensive, taking into consideration the etiological diagnosis of the wound and the characteristics of the wound bed when deciding on a therapeutic proposal appropriate to the healing phase, correcting factors that delay healing. During the epithelialization phase, repair techniques with grafts are recommended to shorten re-epithelialization time, improve the quality of scar tissue, and achieve adequate pain management. Currently, due to the reported benefits of skin appendages, the technique of follicular unit auto-grafting obtained with a scalp punch is among the chosen strategies for wound repair. This is a minimally invasive, outpatient practice, whose technique has advantages over the donor site, patients recovery and well-being.

TLR2 regulates hair follicle cycle and regeneration via BMP signaling.

The etiology of hair loss remains enigmatic, and current remedies remain inadequate. Transcriptome analysis of aging hair follicles uncovered changes in immune pathways, including Toll-like receptors (TLRs). Our findings demonstrate that the maintenance of hair follicle homeostasis and the regeneration capacity after damage depend on TLR2 in hair follicle stem cells (HFSCs). In healthy hair follicles, TLR2 is expressed in a cycle-dependent manner and governs HFSCs activation by countering inhibitory BMP signaling. Hair follicles in aging and obesity exhibit a decrease in both TLR2 and its endogenous ligand carboxyethylpyrrole (CEP), a metabolite of polyunsaturated fatty acids. Administration of CEP stimulates hair regeneration through a TLR2-dependent mechanism. These results establish a novel connection between TLR2-mediated innate immunity and HFSC activation, which is pivotal to hair follicle health and the prevention of hair loss and provide new avenues for therapeutic intervention.

Recent progress in hair follicle stem cell markers and their regulatory roles.

Hair follicle stem cells (HFSCs) in the bulge are a multipotent adult stem cell population. They can periodically give rise to new HFs and even regenerate the epidermis and sebaceous glands during wound healing. An increasing number of biomarkers have been used to isolate, label, and trace HFSCs in recent years. Considering more detailed data from single-cell transcriptomics technology, we mainly focus on the important HFSC molecular markers and their regulatory roles in this review.

Hair follicle stem cells promote epidermal regeneration under expanded condition.

Skin soft tissue expansion is the process of obtaining excess skin mixed with skin development, wound healing, and mechanical stretching. Previous studies have reported that tissue expansion significantly induces epidermal proliferation throughout the skin. However, the mechanisms underlying epidermal regeneration during skin soft tissue expansion are yet to be clarified. Hair follicle stem cells (HFSCs) have been recognized as a promising approach for epidermal regeneration. This study examines HFSC-related epidermal regeneration mechanisms under expanded condition and proposes a potential method for its cellular and molecular regulation.

Characterization of the Newborn Epidermis and Adult Hair Follicles Using Whole-Mount Immunofluorescent Staining of Mouse Dorsal Skin.

The mammalian integumentary system, including skin and its appendages, serves as a protective barrier for the body. During development, skin epidermis undergoes rapid cell division and differentiation to form multiple stratified layers of keratinocytes. Concurrently the epidermis also gives rise to hair follicles that invaginate into the dermis. In adult skin, the hair follicle undergoes cyclic regeneration fueled by hair follicle stem cells located in the bulge. Three-dimensional and high-resolution imaging of these structures using whole-mount immunofluorescent staining allows to better characterize epidermal progenitors and stem cells.

Deciphering Early-Stage Molecular Mechanisms of Negative Pressure Wound Therapy in a Murine Model.

Negative Pressure Wound Therapy (NPWT) is a commonly employed clinical strategy for wound healing, yet its early-stage mechanisms remain poorly understood. To address this knowledge gap and overcome the limitations of human trials, we establish an NPWT C57BL/6JNarl mouse model to investigate the molecular mechanisms involved in NPWT. In this study, we investigate the intricate molecular mechanisms through which NPWT expedites wound healing. Our focus is on NPWT's modulation of inflammatory immune responses and the concurrent orchestration of multiple signal transduction pathways, resulting in shortened coagulation time and reduced inflammation. Notably, we observe a significant rise in dickkopf-related protein 1 (DKK-1) concentration during NPWT, promoting the differentiation of Hair Follicle Stem Cells (HFSCs) into epidermal cells, expediting wound closure. Under negative pressure, macrophages express and release DKK-1 cytokines, crucial for stimulating HFSC differentiation, as validated in animal experiments and in vitro studies. Our findings illuminate the inflammatory dynamics under NPWT, revealing potential signal transduction pathways. The proposed framework, involving early hemostasis, balanced inflammation, and macrophage-mediated DKK-1 induction, provides a novel perspective on enhancing wound healing during NPWT. Furthermore, these insights lay the groundwork for future pharmacological advancements in managing extensive wounds, opening avenues for targeted therapeutic interventions in wound care.

M1 polarization of macrophages promotes stress-induced hair loss via interleukin-18 and interleukin-1ß.

Stress-induced hair loss is a prevalent health concern, with mechanisms that remain unclear, and effective treatment options are not yet available. In this study, we investigated whether stress-induced hair loss was related to an imbalanced immune microenvironment. Screening the skin-infiltrated immune cells in a stressed mouse model, we discovered a significant increase in macrophages upon stress induction. Clearance of macrophages rescues mice from stress-induced hair shedding and depletion of hair follicle stem cells (HFSCs) in the skin, demonstrating the role of macrophages in triggering hair loss in response to stress. Further flow cytometry analysis revealed a significant increase in M1 phenotype macrophages in mice under stressed conditions. In searching for humoral factors mediating stress-induced macrophage polarization, we found that the hormone Norepinephrine (NE) was elevated in the blood of stressed mice. In addition, in-vivo and in-vitro studies confirm that NE can induce macrophage polarization toward M1 through the ß-adrenergic receptor, Adrb2. Transcriptome, enzyme-linked immunosorbent assay (ELISA), and western blot analyses reveal that the NLRP3/caspase-1 inflammasome signaling and its downstream effector interleukin 18 (IL-18) and interleukin 1 beta (IL-1ß) were significantly upregulated in the NE-treated macrophages. However, inhibition of the NE receptor Adrb2 with ICI118551 reversed the upregulation of NLRP3/caspase-1, IL-18, and IL-1ß. Indeed, IL-18 and IL-1ß treatments lead to apoptosis of HFSCs. More importantly, blocking IL-18 and IL-1ß signals reversed HFSCs depletion in skin organoid models and attenuated stress-induced hair shedding in mice. Taken together, this study demonstrates the role of the neural (stress)-endocrine (NE)-immune (M1 macrophages) axis in stress-induced hair shedding and suggestes that IL-18 or IL-1ß may be promising therapeutic targets.

Autophagy induces hair follicle stem cell activation and hair follicle regeneration by regulating glycolysis.

BACKGROUND: Hair follicle stem cells (HFSCs) typically remain quiescent and are activated only during the transition from telogen to anagen to ensure that the hair follicle enters a new cycle. The metabolic behavior of stem cells in tissues is regulated by macroautophagy/autophagy, and changes in HFSC metabolism directly affect their activation and maintenance. However, the role of autophagy in the regulation of HFSC metabolism and function remains unclear. METHODS: Back skin samples were obtained from mice at different hair follicle cycle stages, and immunofluorescence staining was used to monitor autophagy in HFSCs. Mouse and human hair follicles were treated with rapamycin (Rapa, an autophagy activator) or 3-methyladenine (3-MA, an autophagy inhibitor). The effects of autophagy on the hair follicle cycle and HFSC were investigated by imaging, cell proliferation staining, and HFSC-specific marker staining. The influence and mechanism of autophagy on HFSC metabolism were explored using RNA sequencing, real-time polymerase chain reaction, immunohistochemical staining, and detection of lactate and glucose concentrations. Finally, the influence of autophagy-induced glycolysis on HFSC and the hair follicle cycle was verified by stem cell characteristics and in vivo functional experiments. RESULTS: Autophagy in HFSC was highest during the transition from telogen to anagen. Inhibiting autophagy with 3-MA led to early entry into catagen and prolonged telogen, whereas Rapa promoted autophagy and hair growth. Autophagy activated HFSC by increasing the expression and activity of HFSC lactate dehydrogenase (Ldha), thereby transforming HFSC metabolism into glycolysis. Inhibition of Ldha expression counteracted the effects of autophagy. CONCLUSIONS: Autophagy activated HFSC by promoting the transition from HFSC metabolism to glycolysis, ultimately initiating the hair follicle cycle and promoting hair growth.

Short-Term Clinical Assessment of Treating Female Androgenetic Alopecia with Autologous Stem Cells Derived from Human Hair Follicles.

BACKGROUND: Androgenetic alopecia (AGA) is the most common form of alopecia, but treatment options are limited. This study evaluated clinical improvement in hair condition in women with AGA six months after a single injection of autologous cell micrografts (ACMs) containing hair follicle stem cells and dermal papilla cells. METHODS: Twenty-three women with clinically and dermoscopy-confirmed AGA were included. Five 2.5 mm punch biopsies were taken from the skin of each patient with the Regenera device. The cell suspension was prepared with the Rigeneracons device and then injected into the hormone-dependent hairy zone of the scalp. RESULTS: A significant improvement was observed on the visual analog scale (VAS) when comparing pre- and post-procedure photos (p < 0.001). The change in VAS scores was moderately negatively correlated with baseline ferritin concentration and positively with iron concentration. Improved outcomes were associated with higher baseline levels of sex hormone-binding globulin and 17α-hydroxyprogesterone. Neither testosterone nor DHT showed a significant correlation with VAS scores. CONCLUSIONS: The ACM procedure was shown to be both safe and effective, yielding satisfying results six months after a single treatment session. Future investigations should aim to gather evidence that enables the development of a cost-effective approach while minimizing treatment burden and costs.

Reversibly immortalization establishes a hair follicle stem cell line with hair follicle reconstruction ability.

Hair follicle stem cells (HFSCs) play critical roles in the periodic regeneration of hair follicles. HFSCs are also a good model for stem cell biology research. However, no stable mouse HFSC cell line has been reported, which restricts the research and application of HFSCs. We isolated HFSCs from mouse hair follicles and immortalized them by inducing a reversible SV40 large T antigen. Through monoclonal screening, we identified a reversibly immortalized cell line, immortalized HFSC (iHFSC2). RNA sequencing, fluorescence-activated cell sorting, western blotting and immunofluorescence experiments revealed that the expression patterns of iHFSC2 and HFSC were similar at the protein and mRNA levels. After that, iHFSC2s were passaged and morphologically monitored for up to 40 times to detect their long-term culture potential. The long-term cultured iHFSC2 could regenerate hair follicles with complete hair follicle structure and HFSCs in the bulge area. This work successfully established an HFSC cell line with the ability of hair follicle reconstruction.

Photobiomodulation Facilitates Rat Cutaneous Wound Healing by Promoting Epidermal Stem Cells and Hair Follicle Stem Cells Proliferation.

BACKGROUND: Cutaneous wound healing represents a common fundamental phenomenon requiring the participation of cells of distinct types and a major concern for the public. Evidence has confirmed that photobiomodulation (PBM) using near-infrared (NIR) can promote wound healing, but the  cells involved and the precise molecular mechanisms remain elusive. METHODS: Full-thickness skin defects with a diameter of 1.0 cm were made on the back of rats and randomly divided into the control group, 10 J, 15 J, and 30 J groups. The wound healing rate at days 4, 8, and 12 postoperatively was measured. HE and Masson staining was conducted to reveal the histological characteristics. Immunofluorescence staining was performed to label the epidermal stem cells (ESCs) and hair follicle stem cells (HFSCs). Western blot was performed to detect the expressions of proteins associated with ESCs and HFSCs. Cutaneous wound tissues were collected for RNA sequencing. Gene ontology and the Kyoto Encyclopedia of Genes and Genomes analysis was performed, and the hub genes were identified using CytoHubba and validated by qRT-PCR. RESULTS: PBM can promote reepithelialization, extracellular matrix deposition, and wound healing, increase the number of KRT14+/PCNA+ ESCs and KRT15+/PCNA+ HFSCs, and upregulate the protein expression of P63, Krt14, and PCNA. Three hundred and sixty-six differentially expressed genes (DEGs) and 7 hub genes including Sox9, Krt5, Epcam, Cdh1, Cdh3, Dsp, and Pkp3 were identified. These DEGs are enriched in skin development, cell junction, and cadherin binding involved in cell-cell adhesion etc., while these hub genes are related to skin derived stem cells and cell adhesion. CONCLUSION: PBM accelerates wound healing by enhancing reepithelialization through promoting ESCs and HFSCs proliferation and elevating the expression of genes associated with stem cells and cell adhesion. This may provide a valuable alternative strategy to promote wound healing and reepithelialization by modulating the proliferation of skin derived stem cells and regulating genes related to cell adhesion.

Exosomes for hair growth and regeneration.

Exosomes are lipid bilayer vesicles, 30-200 nm in diameter, that are produced by cells and play essential roles in cell-cell communication. Exosomes have been studied in several medical fields including dermatology. Hair loss, a major disorder that affects people and sometimes causes mental stress, urgently requires more effective treatment. Because the growth and cycling of hair follicles are governed by interactions between hair follicle stem cells (HFSCs) and dermal papilla cells (DPCs), a better understanding of the mechanisms responsible for hair growth and cycling through exosomes may provide new insights into novel treatments for hair loss. In this review, we focused on the comprehensive knowledge and recent studies on exosomes in the field of hair development and regeneration. We classified exosomes of several cellular origins for the treatment of hair loss. Exosomes and their components, such as microRNAs, are promising drugs for effective hair loss treatment.

Carbon Dioxide Fractional Laser Treatment Induces Lgr5+ Stem Cell Activation and Hair Regrowth Through the Canonical Wnt/ß-Catenin Pathway.

BACKGROUND: Different types of alopecia have negative impacts on patients. Recently, some kinds of laser or light therapies have been reported to effectively alleviate hair loss. Carbon dioxide fractional laser (CO2FL) treatment is one of the most effective laser treatments, but its beneficial effects and exact mechanism in hair regrowth have not been reported in detail. The purpose of this study was to investigate the effect and molecular mechanism further. METHODS: C57 and Lgr5-Cre: Rosa-mTmG mouse models of hair regrowth were established by CO2FL treatment, and the parameters that induced the best effect were determined. Tissues were harvested on the day prior to the treatment day and on days 3, 5, 7, 10 and 14 after CO2FL. H&E and immunofluorescence staining, RNA sequencing (RNA-seq), quantitative real-time polymerase chain reaction (qPCR), Western blotting (WB) and related inhibitor were used to determine the molecular mechanism underlying the effect of CO2FL treatment on the hair cycle and hair regrowth. In clinical trial, five participants were treated three sessions at 1-month intervals to obverse the effects. RESULTS: Hair regrew and covered the treatment area on the tenth day after CO2FL treatment with the best parameters, while the control group showed signs of hair growth on the 14th day. H&E and immunofluorescence staining showed that the transition of hair follicles (HFs) from telogen to anagen was accelerated, and the rapid activation and proliferation of Lgr5+ hair follicle stem cells (HFSCs) were observed in the treatment group. The RNA-seq, qPCR and WB results indicated that the Wnt pathway was significantly activated after CO2FL treatment. Improvement achieved with CO2FL treatment in clinical trial. CONCLUSIONS: The results of this study suggest that CO2FL treatment can promote hair regrowth by activating Lgr5+ HFSCs and upregulating the Wnt/ß-catenin pathway. Clinical trial results demonstrated that CO2FL treatment will be a promising therapeutic regimen for alopecia. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Distinct mechanisms for sebaceous gland self-renewal and regeneration provide durability in response to injury.

Sebaceous glands (SGs) release oils that protect our skin, but how these glands respond to injury has not been previously examined. Here, we report that SGs are largely self-renewed by dedicated stem cell pools during homeostasis. Using targeted single-cell RNA sequencing, we uncovered both direct and indirect paths by which resident SG progenitors ordinarily differentiate into sebocytes, including transit through a Krt5+PPARγ+ transitional basal cell state. Upon skin injury, however, SG progenitors depart their niche, reepithelialize the wound, and are replaced by hair-follicle-derived stem cells. Furthermore, following targeted genetic ablation of >99% of SGs from dorsal skin, these glands unexpectedly regenerate within weeks. This regenerative process is mediated by alternative stem cells originating from the hair follicle bulge, is dependent upon FGFR2 signaling, and can be accelerated by inducing hair growth. Altogether, our studies demonstrate that stem cell plasticity promotes SG durability following injury.

Autophagy critically controls skin inflammation and apoptosis-induced stem cell activation.

Macroautophagy/autophagy is a cellular recycling program regulating cell survival and controlling inflammatory responses in a context-dependent manner. Here, we demonstrate that keratinocyte-selective ablation of Atg16l1, an essential autophagy mediator, results in exacerbated inflammatory and neoplastic skin responses. In addition, mice lacking keratinocyte autophagy exhibit precocious onset of hair follicle growth, indicating altered activation kinetics of hair follicle stem cells (HFSCs). These HFSCs also exhibit expanded potencies in an autophagy-deficient context as shown by de novo hair follicle formation and improved healing of abrasion wounds. ATG16L1-deficient keratinocytes are markedly sensitized to apoptosis. Compound deletion of RIPK3-dependent necroptotic and CASP8-dependent apoptotic responses or of TNFRSF1A/TNFR1 reveals that the enhanced sensitivity of autophagy-deficient keratinocytes to TNF-dependent cell death is driving altered activation of HFSCs. Together, our data demonstrate that keratinocyte autophagy dampens skin inflammation and tumorigenesis but curtails HFSC activation by restraining apoptotic responses.Abbreviations: ATG16L1: autophagy related 16 like 1; DMBA: 2,4-dimethoxybenzaldehyde; DP: dermal papilla; EpdSCs: epidermal stem cells; Gas6: growth arrest specific 6; HF: hair follicle; HFSC: hair follicle stem cell; IFE: interfollicular epidermis; KRT5: keratin 5; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; PMK: primary mouse keratinocyte; RIPK3: receptor-interacting serine-threonine kinase 3; scRNAseq: single-cell RNA-sequencing; SG: sebaceous gland; TEWL: transepidermal water loss; TPA: 12-O-tetradecanoylphorbol-13-acetate; TNF: tumor necrosis factor; TNFRSF1A/TNFR1: tumor necrosis factor receptor superfamily, member 1a; UMAP: uniform manifold approximation and projection.