Estrogen leads to reversible hair cycle retardation through inducing premature catagen and maintaining telogen

iTRAQ-based quantitative proteomics revealing the therapeutic mechanism of a medicinal and edible formula YH0618 in reducing doxorubicin-induced alopecia by targeting keratins and TGF-β/Smad3 pathway

YH0618, a medicinal and edible formulation, has demonstrated the potential to alleviate doxorubicin-induced alopecia in animal studies and clinical trials. However, the mechanisms underlying its therapeutic effects remain unexplored. The objective of this study was to ascertain possible therapeutic targets of YH0618 in the treatment of doxorubicin-induced alopecia. The assessment of hair loss was conducted through the measurement of the proportion of the affected area and the examination of skin histology. Isobaric tags for relative and absolute quantification (iTRAQ) in quantitative proteomics was employed to discern proteins that exhibited variable expressions. The major proteins associated with doxorubicin-induced alopecia were identified using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The interaction network of the differentially expressed proteins was constructed using the STRING database and the Python software. The study analyzed a total of 3894 proteins extracted from the skin tissue of mice. Doxorubicin treatment resulted in the upregulation of 18 distinct proteins, whereas one differential protein was found to be downregulated. The above effects were reinstated after the administration of the YH0618 therapy. The bioinformatic study revealed that the identified proteins exhibited enrichment in many biological processes, including staphylococcus aureus infection, estrogen signaling route, pyruvate metabolism, chemical carcinogenesis, and PPAR signaling pathway. The results of Western blot revealed that the levels of keratin 81 (Krt81), keratin 34 (Krt34), keratin 33a (Krt33a), and Sma and MAD-related protein 3 (Smad3) were upregulated in response to doxorubicin treatment, and were attenuated by the administration of YH0618. These four proteins are likely to correlate with DOX-induced alopecia and serve as promising therapeutic targets for YH0618. This work presents significant insights and empirical evidence for comprehending the process underlying chemotherapy-induced alopecia, paving the way for exploring innovative therapeutic or preventive strategies employing herbal items.

Epidermal retinol dehydrogenases cyclically regulate stem cell markers and clock genes and influence hair composition

The hair follicle (HF) is a self-renewing adult miniorgan that undergoes drastic metabolic and morphological changes during precisely timed cyclic organogenesis. The HF cycle is known to be regulated by steroid hormones, growth factors and circadian clock genes. Recent data also suggest a role for a vitamin A derivative, all-trans-retinoic acid (ATRA), the activating ligand of transcription factors, retinoic acid receptors, in the regulation of the HF cycle. Here we demonstrate that ATRA signaling cycles during HF regeneration and this pattern is disrupted by genetic deletion of epidermal retinol dehydrogenases 2 (RDHE2, SDR16C5) and RDHE2-similar (RDHE2S, SDR16C6) that catalyze the rate-limiting step in ATRA biosynthesis. Deletion of RDHEs results in accelerated anagen to catagen and telogen to anagen transitions, altered HF composition, reduced levels of HF stem cell markers, and dysregulated circadian clock gene expression, suggesting a broad role of RDHEs in coordinating multiple signaling pathways.

Prioritizing susceptibility genes for the prognosis of male-pattern baldness with transcriptome-wide association study

BACKGROUND

Male-pattern baldness (MPB) is the most common cause of hair loss in men. It can be categorized into three types: type 2 (T2), type 3 (T3), and type 4 (T4), with type 1 (T1) being considered normal. Although various MPB-associated genetic variants have been suggested, a comprehensive study for linking these variants to gene expression regulation has not been performed to the best of our knowledge.

RESULTS

In this study, we prioritized MPB-related tissue panels using tissue-specific enrichment analysis and utilized single-tissue panels from genotype-tissue expression version 8, as well as cross-tissue panels from context-specific genetics. Through a transcriptome-wide association study and colocalization analysis, we identified 52, 75, and 144 MPB associations for T2, T3, and T4, respectively. To assess the causality of MPB genes, we performed a conditional and joint analysis, which revealed 10, 11, and 54 putative causality genes for T2, T3, and T4, respectively. Finally, we conducted drug repositioning and identified potential drug candidates that are connected to MPB-associated genes.

CONCLUSIONS

Overall, through an integrative analysis of gene expression and genotype data, we have identified robust MPB susceptibility genes that may help uncover the underlying molecular mechanisms and the novel drug candidates that may alleviate MPB.

CeRNA regulates network and expression and SNP effect on NFKBIA of cashmere fineness

In this study, a total of 1140 Liaoning Cashmere Goats (LCG) were genotyped for single nucleotide polymorphism (SNP) of NFKBIA gene. There are 15 SNPs and 7 genotypes have been found, and G1547A (GG) genotype has been associated with cashmere fineness and cashmere yield. An integrated ceRNA regulatory network of NFKBIA gene was made. To prove NFKBIA and these non-coding RNAs (ncRNAs) may be related to cashmere fineness, we performed qPCR on these ncRNA in LCG coarse type skin (CT-LCG) and LCG fine type skin (FT-LCG). The result of qPCR showed lncRNA XLOC_011060 and ciRNA452 are at high expression level in CT-LCG, all miRNAs appear high expressed in FT-LCG, and mir-93 was the most significant difference between CT-LCG and FT-LCG. In addition, five miRNAs were selected for qPCR in different genotypes. The qPCR results showed that mir-93 might negatively regulate cashmere fineness and mir-17-5p may play a positive role in regulating cashmere fineness of individuals with G1355A (AG) genotype. These results demonstrated that NFKBIA gene is associated with cashmere fineness of LCG and G1547A (GG) genotype is the preferred marker genotype for cashmere fineness.

Signaling pathways in hair aging

Hair follicle (HF) homeostasis is regulated by various signaling pathways. Disruption of such homeostasis leads to HF disorders, such as alopecia, pigment loss, and hair aging, which is causing severe health problems and aesthetic concerns. Among these disorders, hair aging is characterized by hair graying, hair loss, hair follicle miniaturization (HFM), and structural changes to the hair shaft. Hair aging occurs under physiological conditions, while premature hair aging is often associated with certain pathological conditions. Numerous investigations have been made to determine the mechanisms and explore treatments to prevent hair aging. The most well-known hypotheses about hair aging include oxidative stress, hormonal disorders, inflammation, as well as DNA damage and repair defects. Ultimately, these factors pose threats to HF cells, especially stem cells such as hair follicle stem cells, melanocyte stem cells, and mesenchymal stem cells, which hamper hair regeneration and pigmentation. Here, we summarize previous studies investigating the above mechanisms and the existing therapeutic methods for hair aging. We also provide insights into hair aging research and discuss the limitations and outlook.

Estrogen administration and withdrawal in a model of hormone-simulated pregnancy lead to alterations in behavior and gene expression but do not induce depression-like phenotypes in mice

Pregnancy and the post-partum period are associated with substantial fluctuations in hormone levels and are frequently associated with significant stress. Many individuals also experience affective disturbances during the peri‑partum period, including anxiety, the 'baby blues,' and post-partum depression. However, the extent to which these affective changes result from rapidly altering hormone levels, increased stress, or the combination of both remains largely unknown. The current study sought to evaluate the consequences of pregnancy-like hormonal changes on behavior and gene expression in c57BL/6 mice in the absence of stress using a hormone-simulated pregnancy model. Our results reveal that animals receiving hormone injections to simulate the high levels of estrogen observed in late pregnancy and animals withdrawn from estrogen to mimic the rapid decline in this hormone following parturition both exhibit increased anxiety-like behavior compared to ovariectomized controls in the novel open field test. However, no other significant anxiety- or depression-like alterations were observed in either hormone-treated group compared to ovariectomized controls. Both hormone administration and estrogen withdrawal were shown to induce several significant alterations in gene expression in the bed nucleus of the stria terminalis and the paraventricular nucleus of the hypothalamus. In contrast to the estrogen withdrawal hypothesis of post-partum depression, our results suggest that this method estrogen withdrawal following hormone-simulated pregnancy in the absence of stress does not induce phenotypes consistent with post-partum depression in c57BL/6 mice. However, given that estrogen withdrawal does lead to significant gene expression changes in two stress-sensitive brain regions, it remains possible that estrogen withdrawal could still contribute to affective dysregulation in the peri-partum period by influencing susceptibility to stress. Future research is required to evaluate this possibility.

Frontal Fibrosing Alopecia: An Observational Single-Center Study of 306 Cases

(1) Background: Frontal fibrosing alopecia (FFA) is a scarring alopecia that predominantly affects postmenopausal women; (2) Methods: A retrospective, observational, single-center study was conducted in the Hospital General Universitario in Ciudad Real, Spain, including all patients diagnosed with FFA between 2010 and 2021; (3) Results: A total of 306 patients (296 women and 10 men) were included in our study. The mean age of onset was 59.5 years. The severity of this disease was evenly distributed between mild (147 patients) and severe (149 patients) forms. There was a positive, statistically significant, medium correlation between the severity of the disease and its time of progression. Moreover, hypothyroidism was present in 70 patients (22.9%) and classic signs of concomitant lichen planopilaris were observed in just 30 patients (9.8%), while other forms of lichen planus were uncommon. The estimated prevalence in our population is 0.15% and the incidence is 15.47 new cases per 100,000 inhabitants; (4) Conclusions: The time of progression was positively correlated with the severity of FFA. However, the presence of clinical signs, such as inflammatory trichoscopic signs, was not associated with the progression of this condition.

Genome-Wide Analysis of the Homeobox Gene Family and Identification of Drought-Responsive Members in Populus trichocarpa

Homeobox (HB) genes play critical roles in the regulation of plant morphogenesis, growth and development. Here, we identified a total of 156 PtrHB genes from the Populus trichocarpa genome. According to the topologies and taxonomy of the phylogenetic tree constructed by Arabidopsis thaliana HB members, all PtrHB proteins were divided into six subgroups, namely HD-ZIP, ZF-HD, HB-PHD, TALE, WOX and HB-OTHERS. Multiple alignments of conserved homeodomains (HDs) revealed the conserved loci of each subgroup, while gene structure analysis showed similar exon–intron gene structures, and motif analysis indicated the similarity of motif number and pattern in the same subgroup. Promoter analysis indicated that the promoters of PtrHB genes contain a series of cis-acting regulatory elements involved in responding to various abiotic stresses, indicating that PtrHBs had potential functions in these processes. Collinearity analysis revealed that there are 96 pairs of 127 PtrHB genes mainly distributing on Chromosomes 1, 2, and 5. We analyzed the spatio-temporal expression patterns of PtrHB genes, and the virus-induced gene silencing (VIGS) of PtrHB3 gene resulted in the compromised tolerance of poplar seedlings to mannitol treatment. The bioinformatics on PtrHB family and preliminary exploration of drought-responsive genes can provide support for further study of the family in woody plants, especially in drought-related biological processes. It also provides a direction for developing new varieties of poplar with drought resistance. Overall, our results provided significant information for further functional analysis of PtrHB genes in poplar and demonstrated that PtrHB3 is a dominant gene regulating tolerance to water stress treatment in poplar seedlings.

Estrogen regulates the expression of retinoic acid synthesis enzymes and binding proteins in mouse skin

Topical 17-beta-estradiol (E2) regulates the hair cycle, hair shaft differentiation, and sebum production. Vitamin A also regulates sebum production. Vitamin A metabolism proteins localized to the pilosebaceous unit (PSU; hair follicle and sebaceous gland); and were regulated by E2 in other tissues. This study tests the hypothesis that E2 also regulates vitamin A metabolism in the PSU. First, aromatase and estrogen receptors localized to similar sites as retinoid metabolism proteins during mid-anagen. Next, female and male wax stripped C57BL/6J mice were topically treated with E2, the estrogen receptor antagonist ICI 182,780 (ICI), letrozole, E2 plus letrozole, or vehicle control (acetone) during mid-anagen. E2 or one of its inhibitors regulated most of the vitamin A metabolism genes and proteins examined in a sex-dependent manner. Most components were higher in females and reduced with ICI in females. ICI reductions occurred in the premedulla, sebaceous gland, and epidermis. Reduced E2 also reduced RA receptors in the sebaceous gland and bulge in females. However, reduced E2 increased the number of retinal dehydrogenase 2 positive hair follicle associated dermal dendritic cells in males. These results suggest that estrogen regulates vitamin A metabolism in the skin. Interactions between E2 and vitamin A have implications in acne treatment, hair loss, and skin immunity.

Frontal Fibrosing Alopecia: A Review

Frontal fibrosing alopecia is a scarring alopecia, the prevalence of which is increasing worldwide since its first description in 1994. The reason for this emerging epidemic may be a higher exposure to an unknown trigger, although its aethiology and pathogenesis still remain enigmatic. Clinical, trichoscopic, sonographic, and histopathologic findings are allowing clinicians to understand more aspects about this type of cicatricial alopecia. Several treatments have been used in frontal fibrosing alopecia, although the 5-alpha reductase inhibitors seem to be the most promising. The aim of this report is to provide a compilation about the published data regarding frontal fibrosing alopecia in a narrative review.

Clinical characteristics, trichoscopy, histopathology and treatment outcomes of frontal fibrosing alopecia in an Asian population: A retro-prospective cohort study

Frontal fibrosing alopecia (FFA) is a distinctive lymphocytic scarring alopecia with rapid increase in prevalence. Most FFA series are retrospectively reported from Caucasians with only few from Asians. The objective of this study was to characterize the clinical, trichoscopic and histopathological findings as well as treatment outcomes. This was a retro-prospective cohort study of patients diagnosed with FFA from 1 January 2010 to 1 November 2019. All patients were asked to present for re-examination. Clinical, trichoscopic, histopathological and laboratory data were recorded. A questionnaire was used to investigate hair care, hairstyle and facial skin care compared with age-matched normal controls. Multivariate analysis was performed in order to clarify factors associated with severity. All 58 FFA patients were female, of whom 27.6% were premenopausal, 37.7% had a history of surgical menopause, 13.8% had thyroid diseases, 69% had eyebrow loss and 32.8% facial papules. On physical examination, 10.3% showed linear pattern, 46.6% diffuse pattern and 43.1% pseudo-fringe sign. Concomitant lichen planopilaris was found in 25.9%, lichen planus pigmentosus in 24.1% and female pattern hair loss in 48.3%. The most common trichoscopic characteristics in the frontal hairline were lack of follicular ostia (91.4%), perifollicular scales (79.3%) and perifollicular erythema (63.8%). Up to 90% of patients reported FFA as improved or stable after receiving antiandrogen (finasteride or dutasteride) or antimalarial with topical treatment. Multivariate analyses revealed that facial lentiginous macules and trichoscopic perifollicular erythema at the frontal area were FFA severity-associated factors. "Front puff" Thai hairstyle was associated with FFA, while sunscreens and other cosmetic products were not. In conclusion, diffuse and pseudo-fringe sign pattern are common in Asian FFA. The most common autoimmune systemic comorbidity is thyroid disease, while common concomitant dermatological diseases are female pattern hair loss, lichen planopilaris and lichen planus pigmentosus. Antiandrogens or antimalarial plus topical treatment are the most useful therapy.

All-trans-retinoic acid inhibits mink hair follicle growth via inhibiting proliferation and inducing apoptosis of dermal papilla cells through TGF-β2/Smad2/3 pathway

Dermal papilla cells (DPCs), an important component of hair follicles, its proliferation and apoptosis directly regulate and maintain the growth of hair follicles. All-trans-retinoic acid (ATRA) plays a critical role in hair growth. In this study, the effects of ATRA on cultured mink hair follicle growth were studied by administration of different concentrations of ATRA for 12 days in vitro. In addition, the proliferation and apoptosis of DPCs were measured after treating with ATRA. The mRNA and protein levels of hair follicle growth associated factor transforming growth factor-β2 (TGF-β2) and the phosphorylation levels of Smad2/3 were determined. Moreover, TGF-β type I and type II receptor inhibitor LY2109761 and specific inhibitor of Smad3 (SIS3) were administered to investigate the underlying molecular mechanism. The results showed that ATRA inhibited hair follicle growth, promoted TGF-β2 expression and activated phosphorylation of Smad2/3. In addition, ATRA inhibited cell proliferation by arresting the cell cycle at G1 phase and induced apoptosis of DPCs by enhancing the ratio of Bax/Bcl-2 and promoted the cleavage of caspase-3. Furthermore, LY2109761 or SIS3 partially reversed the decreased cell viability, increased apoptosis that were induced by ATRA. In conclusion, ATRA could inhibit hair follicle growth via inhibiting proliferation and inducing apoptosis of DPCs partially through the TGF-β2/Smad2/3 pathway.

Skin transcriptome reveals the periodic changes in genes underlying cashmere (ground hair) follicle transition in cashmere goats

Background

Cashmere goats make an outstanding contribution to the livestock textile industry and their cashmere is famous for its slenderness and softness and has been extensively studied. However, there are few reports on the molecular regulatory mechanisms of the secondary hair follicle growth cycle in cashmere goats. In order to explore the regular transition through the follicle cycle and the role of key genes in this cycle, we used a transcriptome sequencing technique to sequence the skin of Inner Mongolian cashmere goats during different months. We analyzed the variation and difference in genes throughout the whole hair follicle cycle. We then verified the regulatory mechanism of the cashmere goat secondary hair follicle growth cycle using fluorescence quantitative PCR.

Results

The growth cycle of cashmere hair could be divided into three distinct periods: a growth period (March–September), a regression period (September–December), and a resting period (December–March). The results of differential gene analyses showed that March was the most significant month. Cluster analysis of gene expression throughout the whole growth cycle further supported the key nodes of the three periods of cashmere growth, and the differential gene expression of keratin corresponding to the ground haircashmere growth cycle further supported the results from tissue slices. Quantitative fluorescence analysis showed that KAP3–1, KRTAP 8–1, and KRTAP 24–1 genes had close positive correlation with the cashmere growth cycle, and their regulation was consistent with the growth cycle of cashmere.

Conclusion

The growth cycle of cashmere cashmere could be divided into three distinct periods: a growth period (March–September), a regression period (September–December) and a resting period (December–March). March was considered to be the beginning of the cycle. KAP and KRTAP showed close positive correlation with the growth cycle of secondary hair follicle cashmere growth, and their regulation was consistent with the cashmere growth cycle. But hair follicle development-related genes are expressed earlier than cashmere growth, indicating that cycle regulation could alter the temporal growth of cashmere. This study laid a theoretical foundation for the study of the cashmere development cycle and provided evidence for key genes during transition through the cashmere cycle. Our study provides a theoretical basis for cashmere goat breeding.

CRISPR/Cas9-mediated Disruption of Fibroblast Growth Factor 5 in Rabbits Results in a Systemic Long Hair Phenotype by Prolonging Anagen

Hair growth and morphology are generally regulated by the hair cycle in mammals. Fibroblast Growth Factor 5 (FGF5), which is a hair cycle regulator, has a role in regulating the hair cycle during the transition from the anagen phase to the catagen phase, and a hereditary long hair phenotype has been widely reported when FGF5 is mutated in humans and other species. However, there has been no such report in rabbits. Thus, the first exon of rabbit FGF5 was disrupted by the CRISPR/Cas9 system, and the phenotype of FGF5^-/- rabbits was characterized while using hematoxylin and eosin (H&E) staining, immunohistochemistry, quantitative PCR, scanning electron microscopy, and western blotting. The results showed a significant and systemic long hair phenotype in the FGF5^-/- rabbits, which indicated that FGF5 is a negative regulator of hair growth. In addition, a decreased diameter of the fiber and a higher area proportion of hair follicle clusters were determined in FGF5^-/- rabbits as compared with the WT rabbits. Further investigation verified that prolonging the anagen phase in rabbits, with decreased BMP2/4 pathway signaling and increased VERSICAN pathway signaling, caused the systemic long hair phenotype. Taken together, these results indicate a systemic long hair phenotype by prolonging anagen in FGF5^-/- rabbits, which could be widely used for Fur production and an ideal model for studying the mechanism of long hair in the future.

An Integrated Analysis of Cashmere Fineness lncRNAs in Cashmere Goats

Animal growth and development are regulated by long non-coding RNAs (lncRNAs). However, the functions of lncRNAs in regulating cashmere fineness are poorly understood. To identify the key lncRNAs that are related to cashmere fineness in skin, we have collected skin samples of Liaoning cashmere goats (LCG) and Inner Mongolia cashmere goats (MCG) in the anagen phase, and have performed RNA sequencing (RNA-seq) approach on these samples. The high-throughput sequencing and bioinformatics analyses identified 437 novel lncRNAs, including 93 differentially expressed lncRNAs. We also identified 3084 differentially expressed messenger RNAs (mRNAs) out of 27,947 mRNAs. Gene ontology (GO) analyses of lncRNAs and target genes in cis show a predominant enrichment of targets that are related to intermediate filament and intermediate filament cytoskeleton. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, sphingolipid metabolism is a significant pathway for lncRNA targets. In addition, this is the first report to reveal the possible lncRNA–mRNA regulatory network for cashmere fineness in cashmere goats. We also found that lncRNA XLOC_008679 and its target gene, KRT35, may be related to cashmere fineness in the anagen phase. The characterization and expression analyses of lncRNAs will facilitate future studies on the potential value of fiber development in LCG.

Expression of lipid-protein gene PLP2 in Liaoning cashmere goat

The relationship between PLP2 gene and cashmere fiber quality of Liaoning cashmere goat was investigated. The sheep fibroblast cells were treated with exogenous cytokines and melatonin, independently, and RNA interference, RT-PCR and in situ hybridization were utilized for investigating the PLP2 gene regulation mechanism underlying the Liaoning cashmere growth. The results showed that the expression of PLP2 gene in the prosperous and degenerative stage is higher than that of the primary follicle, indicating that the PLP2 gene promotes the secondary follicle, wherein the gene is expressed only in the inner root sheath, suggesting its correlation to hair loss. The results of RT-PCR showed that the trend of FGF5 expression in PLP2 gene was positively regulated. The influence of MT on the expression of PLP2 gene was negatively regulated, and the inhibition was gradually enhanced with the passage of time. Studies have confirmed that the Noggin gene is an inhibitor of the BMP signaling pathway. After the noggin gene interferes with the lentivirus infection, the expression of the PLP2 gene is downregulated. Therefore, the PLP2 gene, along with the other suppressor genes including the noggin gene, might affect the development of hair follicles by inhibiting the BMP（Bone morphogenetic proteins）pathway.

Frontal fibrosing alopecia: An update on the hypothesis of pathogenesis and treatment

Frontal fibrosing alopecia (FFA) is a relatively new scarring alopecia that is considered a variant of lichen planopilaris (LPP) with no recognized promising treatments. In this study, we tried to clarify the underlying signaling pathways and their roles in the pathogenesis and progression of FFA. Because of several differences in clinical manifestations, response to treatments, and pathological findings, these two conditions could be differentiated from each other. Taking into account the already discussed signaling pathways and involved players such as T cells, mast cells, and sebaceous glands, different possible therapeutic options could be suggested. In addition to treatments supported by clinical evidence, such as 5 alpha-reductase inhibitors, topical calcineurin inhibitors, hydroxychloroquine, peroxisome proliferator-activated receptor gamma agonists, and oral retinoid agents, various other treatment strategies and drugs, such as phototherapy, Janus kinase inhibitors, dehydroepiandrosterone, sirolimus, cetirizine, and rituximab, could be suggested to mitigate disease progression. Of course, such lines of treatment need further evaluation in clinical trials.

Nature-derived lignan compound VB-1 exerts hair growth-promoting effects by augmenting Wnt/β-catenin signaling in human dermal papilla cells

Background

Vitexin is a kind of lignan compound which has been shown to possess a variety of pharmacological effects, such as anti-inflammatory, anti-oxidative and anti-cancer activities. However the effect of vitexin on hair regeneration has not been elaborated.

Methods

The proliferation of human dermal papilla cells (hDPCs) was examined by cell counting and continuous cell culture after vitexin compound 1 (VB-1) was treated. The expression of lef1, wnt5a, bmp2, bmp4, alpl and vcan was examined by RT-PCR. The expression of dkk1, tgf-β1, active-β-Catenin, and AXIN2 was examined by RT-PCR or immunoblotting. Hair shaft growth was measured in the absence or presence of VB-1.

Results

We demonstrated that VB-1 significantly promotes the proliferation of hDPCs in a concentration-dependent manner within a certain concentration range. Among the hair growth-related genes investigated, dkk1 was clearly down-regulated in hDPCs treated with VB-1. The increased active β-Catenin and decreased AXIN2 protein levels suggest that VB-1 facilitates Wnt/β-catenin signaling in hDPCs in vitro. The expression of DP signature genes was also upregulated after VB-1 treatment. Our study further indicated that VB-1 promotes human hair follicle (HF) growth by HF organ culture assay.

Discussion

VB-1 may exert hair growth-promoting effects via augmenting Wnt/β-catenin signaling in hDPCs.

Short communication: Temporal changes in the skin morphology of dairy cows during the periparturient period

Management of dairy cow productivity requires monitoring of their nutritional status by visual observation. It has been suggested that changes in hair coat appearance are among the indicators of nutritional state in dairy cows. Temporal changes in the skin morphology in cows, however, have not been reported. In this study, we examined the changes in the skin of dairy cows that occur during the peripartum period. Seven pluriparous cows were used. Skin samples were collected at 28 d before the due date and 28 d and 56 d after calving for morphological examination. Hair follicle width was 108.8 ± 5.9 µm (±SD) in the dry period, 95.5 ± 5.5 µm at 28 d after calving, and 104.2 ± 5.3 µm at 56 d postpartum. The percentages of anagen hair follicles during these 3 periods were 41.4 ± 3.4, 18.5 ± 3.4, and 32.3 ± 3.3%, respectively. The corresponding sebaceous gland sizes were 8,362.0 ± 707.6, 7,800.0 ± 831.4, and 9,186.8 ± 962.6 µm², respectively. Hair follicle width was positively correlated with percentage of anagen hair follicles. The thickness of epidermal and proliferation rate of epidermal cell were also correlated. However, the hair follicle width, sebaceous gland size and cell proliferation rate, and thickness and proliferation rate of epidermal cells did not show any marked changes.

In vivo monitoring of hair cycle stages via bioluminescence imaging of hair follicle NG2 cells

Hair growth occurs periodically in a cycle that consists of three different phases: growth, regression, and resting. The length of each phase is regulated by both intrinsic and extrinsic factors throughout life, and influenced by physiological and pathological conditions. Elongation of the resting phase and shortening of the growth phase occur during physiological ageing and in baldness, respectively. In vivo discrimination of each phase of the hair cycle can be used to research for regeneration of hair follicles as well as to evaluate the efficacy of hair regrowth treatments in the same individual. Here we show that NG2+ epithelial cells in the hair follicles encompass bulge stem cells, and that the number of hair follicle NG2 cells underwent dramatic changes during the hair cycle. Transgenic rats with expression of firefly luciferase gene in NG2 cells were generated to monitor the hair cycle in vivo. Hair follicle NG2 cells were clearly visualized via bioluminescence imaging to study each phase of the hair cycle in the rats, from infancy to old age.

Novel insights into the pathways regulating the canine hair cycle and their deregulation in alopecia X

Alopecia X is a hair cycle arrest disorder in Pomeranians. Histologically, kenogen and telogen hair follicles predominate, whereas anagen follicles are sparse. The induction of anagen relies on the activation of hair follicle stem cells and their subsequent proliferation and differentiation. Stem cell function depends on finely tuned interactions of signaling molecules and transcription factors, which are not well defined in dogs. We performed transcriptome profiling on skin biopsies to analyze altered molecular pathways in alopecia X. Biopsies from five affected and four non-affected Pomeranians were investigated. Differential gene expression revealed a downregulation of key regulator genes of the Wnt (CTNNB1, LEF1, TCF3, WNT10B) and Shh (SHH, GLI1, SMO, PTCH2) pathways. In mice it has been shown that Wnt and Shh signaling results in stem cell activation and differentiation Thus our findings are in line with the lack of anagen hair follicles in dogs with Alopecia X. We also observed a significant downregulation of the stem cell markers SOX9, LHX2, LGR5, TCF7L1 and GLI1 whereas NFATc1, a quiescence marker, was upregulated in alopecia X. Moreover, genes coding for enzymes directly involved in the sex hormone metabolism (CYP1A1, CYP1B1, HSD17B14) were differentially regulated in alopecia X. These findings are in agreement with the so far proposed but not yet proven deregulation of the sex hormone metabolism in this disease.

The Modulatable Stem Cell Niche: Tissue Interactions during Hair and Feather Follicle Regeneration

Hair and feathers are unique because (1) their stem cells are contained within a follicle structure, (2) they undergo cyclic regeneration repetitively throughout life, (3) regeneration occurs physiologically in healthy individuals and (4) regeneration is also induced in response to injury. Precise control of this cyclic regeneration process is essential for maintaining the homeostasis of living organisms. While stem cells are regulated by the intra-follicle-adjacent micro-environmental niche, this niche is also modulated dynamically by extra-follicular macro-environmental signals, allowing stem cells to adapt to a larger changing environment and physiological needs. Here we review several examples of macro-environments that communicate with the follicles: intradermal adipose tissue, innate immune system, sex hormones, aging, circadian rhythm and seasonal rhythms. Related diseases are also discussed. Unveiling the mechanisms of how stem cell niches are modulated provides clues for regenerative medicine. Given that stem cells are hard to manipulate, focusing translational therapeutic applications at the environments appears to be a more practical approach.

Advances in Understanding Hair Growth

In this short review, I introduce an integrated vision of human hair follicle behavior and describe opposing influences that control hair follicle homeostasis, from morphogenesis to hair cycling. The interdependence and complementary roles of these influences allow us to propose that the hair follicle is a true paradigm of a "Yin Yang" type, that is a cold/slow-hot/fast duality. Moreover, a new promising field is emerging, suggesting that glycans are key elements of hair follicle growth control.

Differential Expression of Proteins Associated with the Hair Follicle Cycle - Proteomics and Bioinformatics Analyses

Hair follicle cycling can be divided into the following three stages: anagen, catagen, and telogen. The molecular signals that orchestrate the follicular transition between phases are still unknown. To better understand the detailed protein networks controlling this process, proteomics and bioinformatics analyses were performed to construct comparative protein profiles of mouse skin at specific time points (0, 8, and 20 days). Ninety-five differentially expressed protein spots were identified by MALDI-TOF/TOF as 44 proteins, which were found to change during hair follicle cycle transition. Proteomics analysis revealed that these changes in protein expression are involved in Ca2+-regulated biological processes, migration, and regulation of signal transduction, among other processes. Subsequently, three proteins were selected to validate the reliability of expression patterns using western blotting. Cluster analysis revealed three expression patterns, and each pattern correlated with specific cell processes that occur during the hair cycle. Furthermore, bioinformatics analysis indicated that the differentially expressed proteins impacted multiple biological networks, after which detailed functional analyses were performed. Taken together, the above data may provide insight into the three stages of mouse hair follicle morphogenesis and provide a solid basis for potential therapeutic molecular targets for this hair disease.

mTOR signaling promotes stem cell activation via counterbalancing BMP-mediated suppression during hair regeneration

Hair follicles (HFs) undergo cycles of degeneration (catagen), rest (telogen), and regeneration (anagen) phases. Anagen begins when the hair follicle stem cells (HFSCs) obtain sufficient activation cues to overcome suppressive signals, mainly the BMP pathway, from their niche cells. Here, we unveil that mTOR complex 1 (mTORC1) signaling is activated in HFSCs, which coincides with the HFSC activation at the telogen-to-anagen transition. By using both an inducible conditional gene targeting strategy and a pharmacological inhibition method to ablate or inhibit mTOR signaling in adult skin epithelium before anagen initiation, we demonstrate that HFs that cannot respond to mTOR signaling display significantly delayed HFSC activation and extended telogen. Unexpectedly, BMP signaling activity is dramatically prolonged in mTOR signaling-deficient HFs. Through both gain- and loss-of-function studies in vitro, we show that mTORC1 signaling negatively affects BMP signaling, which serves as a main mechanism whereby mTORC1 signaling facilitates HFSC activation. Indeed, in vivo suppression of BMP by its antagonist Noggin rescues the HFSC activation defect in mTORC1-null skin. Our findings reveal a critical role for mTOR signaling in regulating stem cell activation through counterbalancing BMP-mediated repression during hair regeneration.

Adipocytes in skin health and disease

Adipocytes are intimately associated with the dermal compartment of the skin, existing in a specialized dermal depot and displaying dynamic changes in size during tissue homeostasis. However, the roles of adipocytes in cutaneous biology and disease are not well understood. Traditionally, adipocytes within tissues were thought to act as reservoirs of energy, as thermal, or as structural support. In this review, we discuss recent studies revealing the cellular basis of the dynamic development and regenerative capacity of dermal adipocytes associated with the hair cycle and following injury. We discuss and speculate on potential roles of dermal adipocytes in cutaneous biology with an emphasis on communication during hair follicle growth and wound healing. Finally, we explore how alterations in the dermal adipose tissue may support clinical manifestations of cutaneous diseases such as lipodystrophy, obesity, and alopecia.

Frontal fibrosing alopecia: a multicenter review of 355 patients

BACKGROUND

To our knowledge, there are no large multicenter studies concerning frontal fibrosing alopecia (FFA) that could give clues about its pathogenesis and best treatment.

OBJECTIVE

We sought to describe the epidemiology, comorbidities, clinical presentation, diagnostic findings, and therapeutic choices in a large series of patients with FFA.

METHODS

This retrospective multicenter study included patients given the diagnosis of FFA. Clinical severity was classified based on the recession of the frontotemporal hairline.

RESULTS

In all, 355 patients (343 women [49 premenopausal] and 12 men) with a mean age of 61 years (range 23-86) were included. Early menopause was detected in 49 patients (14%), whereas 46 (13%) had undergone hysterectomy. Severe FFA was observed in 131 patients (37%). Independent factors associated with severe FFA after multivariate analysis were: eyelash loss, facial papules, and body hair involvement. Eyebrow loss as the initial clinical presentation was associated with mild forms. Antiandrogens such as finasteride and dutasteride were used in 111 patients (31%), with improvement in 52 (47%) and stabilization in 59 (53%).

LIMITATIONS

The retrospective design is a limitation.

CONCLUSIONS

Eyelash loss, facial papules, and body hair involvement were associated with severe FFA. Antiandrogens were the most useful treatment.

Transcriptome sequencing reveals differences between anagen and telogen secondary hair follicle-derived dermal papilla cells of the Cashmere goat (Capra hircus)

Dermal papilla is considered the control center of hair follicle growth and hair cycle. The secondary hair follicle (producing cashmere) growth cycle of the Cashmere goat (Capra hircus) is circannual, and each growth phase can be easily distinguished by its long duration. To identify gene expression patterns and differences of the dermal papilla cell (DPC) between the anagen and telogen phases, we established two DPC lines: ana-DPCs (DPCs derived from the anagen secondary hair follicle) and tel-DPCs (DPCs derived from the telogen secondary hair follicle). Compared with the ana-DPCs, the tel-DPCs lost the capacity to form cell aggregates and showed lower cell proliferation rate. Transcriptome sequencing revealed that 825 genes were differentially expressed by at least threefold between the two DPC lines. These genes were significantly enriched in cell cycle control, cell division, and chromosome partitioning from the Eukaryotic Orthologous Groups of proteins (KOG) database and in cell cycle, cell adhesion molecules, cytokine-cytokine receptor interaction, and p53 signaling pathway from the Kyoto Encyclopedia of Gene and Genomes (KEGG) database. Enrichment analyses revealed that in the middle of the telogen the DPCs of secondary hair follicles (SHFs) seemed on the one hand to promote the degeneration of SHFs and cessation of cashmere growth, while on the other hand to resist self-apoptosis and prepare for the regeneration or revivification of fully functional dermal papillae. These findings provide a better understanding of hair follicle growth and will be useful for identification of novel molecules associated with the control of hair growth cycle.

Epidermal development in mammals: key regulators, signals from beneath, and stem cells

Epidermis is one of the best-studied tissues in mammals that contain types of stem cells. Outstanding works in recent years have shed great light on behaviors of different epidermal stem cell populations in the homeostasis and regeneration of the epidermis as well as hair follicles. Also, the molecular mechanisms governing these stem cells are being elucidated, from genetic to epigenetic levels. Compared with the explicit knowledge about adult skin, embryonic development of the epidermis, especially the early period, still needs exploration. Furthermore, stem cells in the embryonic epidermis are largely unstudied or ambiguously depicted. In this review, we will summarize and discuss the process of embryonic epidermal development, with focuses on some key molecular regulators and the role of the sub-epidermal mesenchyme. We will also try to trace adult epidermal stem cell populations back to embryonic development. In addition, we will comment on in vitro derivation of epidermal lineages from ES cells and iPS cells.