Hair Follicle Epithelial Cells Research Articles

DNA dioxygenases Tet2/3 regulate gene promoter accessibility and chromatin topology in lineage-specific loci to control epithelial differentiation.

Execution of lineage-specific differentiation programs requires tight coordination between many regulators including Ten-eleven translocation (TET) family enzymes, catalyzing 5-methylcytosine oxidation in DNA. Here, by using Keratin 14-Cre-driven ablation of Tet genes in skin epithelial cells, we demonstrate that ablation of Tet2/Tet3 results in marked alterations of hair shape and length followed by hair loss. We show that, through DNA demethylation, Tet2/Tet3 control chromatin accessibility and Dlx3 binding and promoter activity of the Krt25 and Krt28 genes regulating hair shape, as well as regulate interactions between the Krt28 gene promoter and distal enhancer. Moreover, Tet2/Tet3 also control three-dimensional chromatin topology in Keratin type I/II gene loci via DNA methylation-independent mechanisms. These data demonstrate the essential roles for Tet2/3 in establishment of lineage-specific gene expression program and control of Dlx3/Krt25/Krt28 axis in hair follicle epithelial cells and implicate modulation of DNA methylation as a novel approach for hair growth control.

Recombinant Oil-Body-Expressed Oleosin-hFGF5 in Arabidopsis thaliana Regulates Hair Growth.

FGF5 (Fibroblast Growth Factor) is a member of the fibroblast growth factor family, which not only regulates growth and development but also inhibits hair regeneration. The oil-body expression vector pOTB-hFGF5 was constructed by the genetic engineering method and it was transformed into Arabidopsis by flora dip. T3 homozygous transgenic Arabidopsis was obtained after screening and propagation by the PCR and Western blot methods. The recombinant oil-body-expressed oleosin-hFGF5 can inhibit the proliferation of hair follicle epithelial cells and it exhibits the pharmacological activity of inhibiting hair regeneration in vivo by protein hybridization and imunohistochemistry. At the same time, the potential mechanism of recombinant oil-body-expressed oleosin-hFGF5 inhibiting hair growth was also revealed by RNA-Seq. This implies that the recombinant oil-body-expressed oleosin-hFGF5 has a good effect on inhibiting hair growth.

723 DNA dioxygenases Tet2/3 regulate gene promoter accessibility and three-dimensional chromatin topology in lineage-specific loci to control hair growth

Lineage-specific and functionally-related genes frequently form conserved clusters or loci in the mammalian genomes. Execution of lineage-specific differentiation programs requires tight coordination between many regulators including Ten-eleven translocation (TET) family enzymes catalyzing DNA oxidation. However, the role of Tet genes in the control of cell differentiation at the levels of lineage-specific gene loci is unknown. Epithelial keratin genes are organized in the genome into two distinct (Keratin type I and II) loci on mouse chromosomes 11 and 15. Here, by using Keratin 14-driven ablation of Tet genes in skin epithelial cells, we demonstrate that Tet enzymes play essential roles in the control of gene expression in Keratin type I/II gene loci and execution of hair-specific differentiation program. Mice with Keratin 14-driven ablation of Tet2/Tet3 or all three Tet genes exhibit marked alterations of hair shape and length followed by hair loss. We show that through DNA demethylation, Tet2 and Tet3 control chromatin accessibility, Dlx3 binding and promoter activity of the Krt25 and Krt28 genes regulating hair shape, as well as regulate interactions between the Krt28 gene promoter and distal enhancer. However, Tet2/3 also control three-dimensional chromatin topology in Keratin type I/II gene loci via catalytic activity-independent mechanisms. These data demonstrate for the first time the essential roles for Tet2/3 in establishment of lineage-specific gene expression program and control of Dlx3/Krt25/Krt28 axis in hair follicle epithelial cells and implicate modulation of DNA methylation as a novel approach for hair growth control.

829 Cytotoxic T lymphocytes target henle’s layer in alopecia areata

Autoimmune disease occurs when a specific adaptive immune response is mounted against self-antigen(s) and immune-mediated tissue damage is sustained until the self-antigen is eliminated. We recently identified immunogenic cell death via necroptosis in the hair follicle (HF) epithelium as the primary initiating mechanism in alopecia areata (AA). Here, we aimed to identify the major target cells of T cell-mediated cytotoxicity in AA, after the autoimmune response was initiated. Using the C3H/HeJ mouse model of AA, we first established a spatiotemporal map of caspase-8-driven immune-mediated apoptosis in HF epithelial cells during premature HF regression in AA.

Large-scale isolation of functional dermal papilla cells using novel surface marker LEPTIN Receptor.

Dermal papilla (DP) cells regulate hair follicle epithelial cells and melanocytes by secreting functional factors, playing a key role in hair follicle morphogenesis and hair growth. DP cells can reconstitute new hair follicles and induce hair regeneration, providing a potential therapeutic strategy for treating hair loss. However, current methods for isolating DP cells are either inefficient (physical microdissection) or only applied to genetically labeled mice. We systematically screened for the surface proteins specifically expressed in skin DP using mRNA expression databases. We identified two antibodies against receptors LEPTIN Receptor (LEPR ) and Scavenger Receptor Class A Member 5 (SCARA5) which could specifically label and isolate DP cells by flow cytometry from mice back skin at the growth phase. The sorted LEPR+ cells maintained the DP characteristics after culturing in vitro, expressing DP marker alkaline phosphatase and functional factors including RSPO1/2 and EDN3, the three major DP secretory factors that regulate hair follicle epithelial cells and melanocytes. Furthermore, the low-passage LEPR+ DP cells could reconstitute hair follicles on nude mice using chamber graft assay when combined with epithelial stem cells. The method of isolating functional DP cells we established here lays a solid foundation for developing DP cell-based therapy.

Dysfunction of Hair Follicle Mesenchymal Progenitors Contributes to Age-Associated Hair Loss.

Skin aging is accompanied by hair loss due to impairments in hair follicle (HF) epithelial progenitor cellsand their mesenchymal niche. This inductive mesenchyme, called dermal papilla (DP), undergoes progressive cell loss and eventual miniaturization that contributes to HF pathogenesis. Using laser ablation and fate mapping, we show that HF dermal stem cells (hfDSCs) reconstitute the damaged DP and maintain hair growth, suggesting that hfDSC dysfunction may trigger degeneration of the inductive niche. Fate mapping over 24months revealed progressive hfDSC depletion, and invivo clonal analysis of aged hfDSCs showed impaired self-renewal and biased differentiation. Single-cell RNA-seq confirmed hfDSCs as a central precursor, giving rise to divergent mesenchymal trajectories. In agedskin, hfDSCs exhibited senescent-like characteristics, and senescence-associated secretory phenotypes were identified in the aging HF mesenchyme. These results clarify fibroblast dynamics within the HF and suggest that progressive dysfunction within the mesenchymal progenitor pool contributes to age-related hair loss.

CD49fhigh Defines a Distinct Skin Mesenchymal Stem Cell Population Capable of Hair Follicle Epithelial Cell Maintenance

The dermis harbors distinct mesenchymal stem cell (MSC) populations, which play equally important roles as epidermal stem cells in skin homeostasis and regeneration. However, to reliably identify and directly isolate the invivo counterpart of these cells is still challenging. Using the epidermal stem cell marker CD49f, we defined a CD49fhigh distinct mesenchymal subpopulation in the dermis. Invitro and invivo differentiation assays, and transcriptome analysis demonstrated that CD49fhigh cells possess neural crest-like cell characteristics. Our results showed that the formation of hair follicle-like budding structure and the expressions of key genes regulating hair follicle development were induced when hair follicle epithelial cells were co-cultured with CD49fhigh cells. We also found that CD49fhigh cells activated Notch signaling in co-cultured hair follicle epithelial cells, whereas the inhibition of Notch signaling resulted in epidermal cyst-like spheres and loss of maintenance of hair follicle epithelial cell characteristics. Furthermore, we identified Itga7 and CD49f as an efficient biomarker panel for direct selection of CD49fhigh skin MSCs. Our results lead to a deeper understanding of heterogeneity and the function of MSCs in the skin and may facilitate potential translational applications of these cells.

Progenitor cells expressing nestin, a neural crest stem cell marker, differentiate into outer root sheath keratinocytes.

Nestin, which was originally described as a neural crest stem cell marker, is known to be expressed in bulge follicle cells of human, canine and murine anagen hairs. However, the capacity of nestin-expressing cells to differentiate into the components of the hair follicle or the epidermis has been insufficiently investigated. To determine whether nestin-expressing cells are capable of differentiating into keratinocytes. A double-transgenic mouse line Nes-Cre/CAG-CAT-EGFP, in which enhanced green fluorescent protein (EGFP) is expressed upon Cre-based recombination driven by the nestin promoter. The tissue distribution of EGFP+ and nestin+ cells in the skin of the mouse line was analysed by immunofluorescence and immunohistochemical analyses. EGFP+ cells were recognized in the outer epithelial cell layers of anagen and telogen hair follicles, but rarely seen in the interfollicular epidermis. The EGFP+ cells in the outer layers of the hair follicles coexpressed keratin 14, a marker of the outer root sheath (ORS) keratinocytes, but not trichohyalin granules, an inner root sheath keratinocyte cell marker. Immunostaining for nestin failed to detect its expression in the majority of hair follicle epithelial cells, suggesting that the EGFP+ cells in the ORS were derived from nestin-expressing progenitor cells that had become further committed along the epithelial cell lineage, where nestin is no longer expressed. These results suggest that progenitor cells that differentiate into ORS keratinocytes are distinct from those for other hair follicle or epidermal components and provide implications for regenerative medicine and the molecular classification of hair follicle tumours.

TGF-β and HSP70 profiles during transformation of yak hair follicles from the anagen to catagen stage.

Transforming growth factor-β (TGF-β) and heat shock protein 70 (HSP70) are important for the hair follicle (HF) cycle, but it is unclear whether they participate in HF regression in yak skin. In this study, we investigated the role of TGF-β, TGF-βRII, and HSP70 in the transition from anagen to catagen of HFs. The results showed that TGF-β2 transcription was significantly higher than that of TGF-β1 and TGF-β3 in the same periods. Meanwhile, the expressions of TGF-β2, TGF-βRII, and caspase-3 were higher in the catagen phase than that in mid-anagen, and some TGF-βRII-positive HF cells were terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL)-positive. Moreover, the HSP70 protein levels in mid-anagen were higher than those in late-anagen and catagen. These results suggested that TGF-β2 plays a major role in catagen induction in yak HFs, which might be achieved via TGF-βRII-mediated apoptosis in HF epithelial cells. In contrast, HSP70 might protect epithelial cells from apoptosis and ultimately inhibit HF regression. In conclusion, TGF-β2 has positive effects, whereas HSP70 has negative effects, on catagen induction.

Is prolactin a negative neuroendocrine regulator of human skin re-epithelisation after wounding?

Chronic wounds remain a major unmet healthcare challenge, associated with substantial morbidity and economic costs. Therefore, novel treatment strategies and therapeutic approaches need to be urgently developed. Yet, despite the increasingly recognized importance of neurohormonal signaling in skin physiology, the neuroendocrine regulation of cutaneous wound healing has received surprisingly little attention. Human skin, and its appendages, locally express the pleiotropic neurohormone prolactin (PRL), which not only regulates lactation but also hair follicle cycling, angiogenesis, keratinocyte proliferation, and epithelial stem cell functions. Therefore, we examined the effects of PRL in experimentally wounded female human skin organ culture. Overall, this revealed that PRL slightly, but significantly, inhibited epidermal regeneration (reepithelialisation), cytokeratin 6 protein expression and intraepidermal mitochondrial activity (MTCO1 expression), while it promoted keratinocyte terminal differentiation (i.e. involucrin expression) ex vivo. If the current pilot data are confirmed by further studies, PRL may serve as one of the-rarely studied-negative regulators of cutaneous wound healing that control excessive reepithelialisation. This raises the intriguing and clinically relevant question of whether PRL receptor antagonists could actually promote epidermal repair after human skin wounding.

1357 β-catenin regulation in Krox20 lineage hair follicle epithelial cells

1357 β-catenin regulation in Krox20 lineage hair follicle epithelial cells

The cellular and molecular basis of direction selectivity of Aδ-LTMRs.

The perception of touch, including the direction of stimulus movement across the skin, begins with activation of low-threshold mechanosensory neurons (LTMRs) that innervate the skin. Here, we show that murine Aδ-LTMRs are preferentially tuned to deflection of body hairs in the caudal-to-rostral direction. This tuning property is explained by the finding that Aδ-LTMR lanceolate endings around hair follicles are polarized; they are concentrated on the caudal (downward) side of each hair follicle. The neurotrophic factor BDNF is synthesized in epithelial cells on the caudal, but not rostral, side of hair follicles, in close proximity to Aδ-LTMR lanceolate endings, which express TrkB. Moreover, ablation of BDNF in hair follicle epithelial cells disrupts polarization of Aδ-LTMR lanceolate endings and results in randomization of Aδ-LTMR responses to hair deflection. Thus, BDNF-TrkB signaling directs polarization of Aδ-LTMR lanceolate endings, which underlies direction-selective responsiveness of Aδ-LTMRs to hair deflection.

A newly discovered linkage between proteoglycans and hair biology: decorin acts as an anagen inducer.

Proteoglycans have been suggested to play pivotal roles in hair biology. Decorin is a prototypical member of the small leucine-rich proteoglycan family, which is involved in numerous biological processes. However, the role of decorin in the hair cycle has not been elucidated. Moreover, the effects of decorin on the activities of many growth factors are complex, and it is hard to predict whether decorin would affect hair growth or the hair cycle positively or negatively. Jing etal. focused on the potential role of decorin in the hair cycle and found that decorin is highly expressed in the epidermis, in hair follicle epithelial cells and in dermal papilla cells in the anagen phase. The expression of decorin was decreased during catagen to telogen, except for the bulge region. Exogenous administration of decorin accelerated anagen and delayed catagen transition as a positive regulator of the hair cycle. Because TGF-β is one of the androgen-induced pathogenic factors in androgenetic alopecia, this study provides clues to understand the pathogenesis and new therapeutic targets of hair loss.

Hair follicle regression and perifollicular inflammatory infiltrate in alopecia areata

Alopecia areata (AA) is a kind of inflammation-induced,self-limited and non-scarring hair loss.No satisfactory treatment is available for AA at present,and relapse is frequent.The pathogenesis of AA remains unclear.Pathologically,it is characterized by inflammatory infiltrate around anagen hair follicles and degeneration of hair follicles.Most current studies suggest that inflammatory cells attack anagen hair follicles,which together with cytokines and neuropeptides constitute a vacious cycle,leading to the apoptosis in hair follicle epithelial cells followed by sudden simultaneous regression of numerous hair follicles,and,finally,causing the initiation of AA. Key words: Alopecia areata; Hair follicle; Inflammation

Trichorhinophalangeal syndrome with low expression of TRPS1 on epidermal and hair follicle epithelial cells

Trichorhinophalangeal syndrome (TRPS) is an autosomal-dominant congenital hair loss disease characterized by sparse and slow-growing scalp hair, craniofacial and skeletal abnormalities, pear-shaped nose, thin upper lip, brittle and thin toenails, and bilateral brachydactyly of the big toes. We report a case of TRPS1 exhibiting these clinical features with a novel heterozygous single nucleotide substitution in exon 3 of the TRPS1 gene. By immunohistochemical analysis of a biopsied specimen of the patient's alopecia lesion, we found for the first time that the expression level of TRPS1 was markedly reduced in the epidermis and the outer root sheath of hair follicles as compared to a normal subject. In addition, higher expression of phospho-Stat3 was found consequent to the loss of TRPS1 in the outer root sheath.

Effects of diphencyprone on expression of Bcl-2 protein in patients with Alopecia areata

Background: Alopecia areata (AA) development is attributed to a T cell involved autoimmune process. Apoptosis is one of the suspected culprits in pathogenesis of this disorder. This disorder can be treated by contact sensitizers like diphencyprone (DPCP). We investigated the effects of treatment with DPCP on the expression of Bcl-2 protein in hair follicle epithelial cells of AA patients and its relation to clinical response to treatment.Materials and Methods: Patients with chronic and extensive AA who had not received any treatment for at least 6 months were included. Furthermore, 3-mm punch biopsies were obtained from the affected areas before starting the treatment, and, six months after DPCP application, punch biopsies of the same size were taken from the following groups of patients: Group 1: six patients with complete hair regrowth, Group 2: six patients with partial regrowth, and Group 3: six patients with no regrowth. The samples were studied by immunohistochemistry to detect and compare the rate of Bcl-2 expression.Results: Level of Bcl-2 expression in respondent patients (Group 1) was significantly higher after DPCP treatment (36.50 ± 4.23) compared to pretreatment state (3.67 ± 1.406, P < 0.001). Similar finding was observed in second group with partial regrowth (17.67 ± 1.745 versus 5.33 ± 2.076, P < 0.01). Such significant change was not observed in third group (4.75 ± 1.315 versus 3.50 ± 0.645, P > 0.05).Conclusion:The results of this study indicate the positive effect of DPCP on regulation (inhibition) of apoptotic process in patients with AA.

Review of hair follicle dermal cells

Hair follicle stem cells in the epithelial bulge are responsible for the continual regeneration of the hair follicle during cycling. The bulge cells reside in a niche composed of dermal cells. The dermal compartment of the hair follicle consists of the dermal papilla and dermal sheath. Interactions between hair follicle epithelial and dermal cells are necessary for hair follicle morphogenesis during development and in hair reconstitution assays. Dermal papilla and dermal sheath cells express specific markers and possess distinctive morphology and behavior in culture. These cells can induce hair follicle differentiation in epithelial cells and are required in hair reconstitution assays either in the form of intact tissue, dissociated freshly prepared cells or cultured cells. This review will focus on hair follicle dermal cells since most therapeutic efforts to date have concentrated on this aspect of the hair follicle, with the idea that enriching hair-inductive dermal cell populations and expanding their number by culture while maintaining their properties, will establish an efficient hair reconstitution assay that could eventually have therapeutic implications.

Nonviral in Situ Green Fluorescent Protein Labeling and Culture of Primary, Adult Human Hair Follicle Epithelial Progenitor Cells

In this article we show that cloning of the human K15 promoter before a green fluorescence protein (GFP)/geneticin-resistance cassette and transfection of microdissected, organ-cultured adult human scalp hair follicles generates specific K15 promoter-driven GFP expression in their stem cell-rich bulge region. K15-GFP+ cells can be visualized in situ by GFP fluorescence and 2-photon laser scanning microscopy. Vital K15-GFP+ progenitor cells can then be selected by using the criteria of their green fluorescence, adhesion to collagen type IV and fibronectin, and geneticin resistance. Propagated K15-GFP+ cells express epithelial progenitor markers, show the expected differential gene expression profile of human bulge epithelium, and form holoclones. This application of nonretroviral, K15 promoter-driven, GFP labeling to adult human hair follicles facilitates the characterization and manipulation of human epithelial stem cells, both in situ and in vitro, and should be transferable to other complex human tissues.

Differential expression of stem-cell-associated markers in human hair follicle epithelial cells

Several putative biomarkers have been suggested for identifying murine follicular stem cells; however, human hair follicles have a different pattern of biomarker expression, and follicular stem cell isolation methods have not been established. To isolate a stem cell population applicable to clinical settings, we conducted a comprehensive survey of the expression of stem-cell-associated (K15, CD200, CD34, and CD271) and other biomarkers (K1, K14, CD29, and CD49f) in immunohistological sections of the human epidermis and follicular outer root sheath (ORS). We also examined freshly isolated and cultured epidermal or follicular cells with single- and multicolor flow cytometry or immunocytochemistry. After sorting cells by CD200, CD34, and forward scatter (FSC) values (cell size), colony-forming assays were performed. We found that biomarkers were differentially expressed in the epidermis and ORS. Basal bulge cells were mainly K15+CD200+CD34−CD271−, and suprabasal cells were K15−CD200+CD34−CD271−. We categorized follicular cells into nine subpopulations according to biomarker expression profiles. The CD200+CD34− bulge cells had much higher colony-forming abilities than the CD34+ population, and were divided into two subpopulations: a CD200+CD34−FSChigh (K15-rich, basal) and a CD200+CD34–FSClow (K15-poor, suprabasal) population. The former formed fewer but larger-sized colonies than the latter. Follicular epithelial cell cultivation resulted in loss of K15, CD200, CD34, and CD271 expression, but maintenance of K14, CD29, and CD49f expression. We found that the bulge contained two populations with different localizations, cell sizes, and colony-forming abilities. We showed that K15, CD200, CD34, and CD271 were useful biomarkers for characterizing freshly isolated human follicular epithelial cells in diverse stages of differentiation.

(Neuro-)endocrinology of epithelial hair follicle stem cells

The hair follicle is a repository of different types of somatic stem cells. However, even though the hair follicle is both a prominent target organ and a potent, non-classical site of production and/or metabolism of numerous polypetide- and steroid hormones, neuropeptides, neurotransmitters and neurotrophins, the (neuro-)endocrine controls of hair follicle epithelial stem cell (HFeSC) biology remain to be systematically explored. Focussing on HFeSCs, we attempt here to offer a "roadmap through terra incognita" by listing key open questions, by exploring endocrinologically relevant HFeSC gene profiling and mouse genomics data, and by sketching several clinically relevant pathways via which systemic and/or locally generated (neuro-)endocrine signals might impact on HFeSC. Exemplarily, we discuss, e.g. the potential roles of glucocorticoid and vitamin D receptors, the hairless gene product, thymic hormones, bone morphogenic proteins (BMPs) and their antagonists, and Skg-3 in HFeSC biology. Furthermore, we elaborate on the potential role of nerve growth factor (NGF) and substance P-dependent neurogenic inflammation in HFeSC damage, and explore how neuroendocrine signals may influence the balance between maintenance and destruction of hair follicle immune privilege, which protects these stem cells and their progeny. These considerations call for a concerted research effort to dissect the (neuro-)endocrinology of HFeSCs much more systematically than before.