Wnt7b is an important intrinsic regulator of hair follicle stem cell homeostasis and hair follicle cycling

Frizzled 6 endows high-grade serous ovarian cancer with stem-like properties and chemoresistance

Stem-like properties contribute to tumor growth, metastasis, and chemoresistance. High-grade serous ovarian cancer (HGSOC) exhibits a very aggressive phenotype characterized by extensive metastasis, rapid progression, and therapy resistance. Frizzled 6 (FZD6) is overexpressed in HGSOC, and higher levels of FZD6 have been associated with shorter survival times in patients with HGSOC. Functionally, FZD6 promotes HGSOC growth and peritoneal metastasis. It endues HGSOC cells with stem-like properties by modulating POU5F1, ALDH1, and EPCAM. It can also desensitize HGSOC cells to certain chemical drugs. As a putative ligand for FZD6, WNT7B is also implicated in cell proliferation, stem-like properties, invasion and migration, and chemoresistance. SMAD7 is a downstream component of FZD6 signaling that is thought to mediate FZD6-associated phenotypes, at least in part. Therefore, FZD6/WNT7B-SMAD7 can be considered a tumor-promoting signaling pathway in HGSOC that may be responsible for tumor growth, peritoneal metastasis, and chemoresistance.

Deconvolving organogenesis in space and time via spatial transcriptomics in thick tissues

Organ development is guided by a space-time landscape that constraints cell behavior. This landscape is challenging to characterize for the hair follicle - the most abundant mini organ - due to its complex microscopic structure and asynchronous development. We developed 3DEEP, a tissue clearing and spatial transcriptomic strategy for characterizing tissue blocks up to 400 µm in thickness. We captured 371 hair follicles at different stages of organogenesis in 1 mm 3 of skin of a 12-hour-old mouse with 6 million transcripts from 81 genes. From this single time point, we deconvoluted follicles by age based on whole-organ molecular pseudotimes to animate a stop-motion 3D atlas of follicle development along its trajectory. We defined molecular stages for hair follicle organogenesis and characterized the order of emergence for its structures, differential signaling dynamics at its top and bottom, morphogen shifts preceding and accompanying structural changes, and series of structural changes leading to the formation of its canal and opening. We further found that hair follicle stem cells and their niche are established and stratified early in organogenesis, before the formation of the hair bulb. Overall, this work demonstrates the power of increased depth of spatial transcriptomics to provide a four-dimensional analysis of organogenesis.

The overexpression of R-spondin 3 affects hair morphogenesis and hair development along with the formation and maturation of the hair follicle stem cells

Mice hair follicles (HFs) are a valuable model for studying various aspects of hair biology, including morphogenesis, development, and regeneration due to their easily observable phenotype and genetic manipulability. The initiation and progression of hair follicle morphogenesis, as well as the hair follicle cycle, are regulated by various signaling pathways, of which the main role is played by the Wingless-type MMTV integration site family (Wnt) and the Bone Morphogenic Protein (BMP). During the hair follicle cycle, the BMP pathway maintains hair follicle stem cells (HFSCs) in a dormant state while the Wnt pathway activates them for hair growth. Given the pivotal role of the Wnt pathway in hair biology and HFSCs regulation, we investigated the influence of the Wnt modulator - R-spondin 3 (Rspo3), in these processes. For this purpose, we developed a transgenic mice model with the overexpression of Rspo3 (Rspo3GOF) in the whole ectoderm and its derivatives, starting from early morphogenesis. Rspo3GOF mice exhibited a distinct phenotype with sparse hair and visible bald areas, caused by reduced proliferation and increased apoptosis of hair matrix progenitor cells, which resulted in a premature anagen-to-catagen transition with a shortened growth phase and decreased overall length of all hair types. In addition, Rspo3GOF promoted induction of auchene and awl, canonical Wnt-dependent hair type during morphogenesis, but the overall hair amount remained reduced. We also discovered a delay in the pre-bulge formation during morphogenesis and prolonged immaturity of the HFSC population in the bulge region postnatally, which further impaired proper hair regeneration throughout the mice's lifespan. Our data supported that Rspo3 function observed in our model works in HFSCs' formation of pre-bulge during morphogenesis via enhancing activation of the canonical Wnt pathway, whereas in contrast, in the postnatal immature bulge, activation of canonical Wnt signaling was attenuated. In vitro studies on keratinocytes revealed changes in proliferation, migration, and colony formation, highlighting the inhibitory effect of constitutive overexpression of Rspo3 on these cellular processes. Our research provides novel insights into the role of Rspo3 in the regulation of hair morphogenesis and development, along with the formation and maturation of the HFSCs, which affect hair regeneration.

Molecular insights into Pashmina fiber production: comparative skin transcriptomic analysis of Changthangi goats and sheep

Ladakh, one of the highest inhabited regions globally, hosts the unique Changthangi goat, renowned for producing Pashmina, the world's most luxurious natural fiber. In comparison, the fiber derived from Changthangi sheep is considered next only to Pashmina. This research endeavors to compare the skin transcriptome profiles of Changthangi goats and Changthangi sheep, aiming to discern the molecular determinants behind the recognition of Changthangi goats as the source of Pashmina. Drawing upon previously conducted studies, a collective of 225 genes correlated with fiber characteristics were extracted from the differentially expressed genes noticed between the two species (p-value of ≤ 0.05 and a log2 fold change of ≥ 1.5). These genes were analyzed using DAVID software to understand their biological functions and to identify enriched KEGG and Reactome pathways. The protein-protein interaction networks were constructed using Cytoscape, cytoHubba, and STRING to focus on key genes and infer their biological significance. Comparative transcriptome analysis revealed significantly higher expression of genes involved in signaling pathways like Wnt, MAPK, PI3K-Akt, Hedgehog, associated with fiber development and quality in Changthangi goats. These pathways play crucial roles in hair follicle (HF) formation, maintenance of epidermal stem cells, and fiber characteristics. Findings also highlight the enrichment of cell adhesion molecules and ECM-receptor interaction, emphasizing their roles in HF structure, growth, and signaling. This investigation offers an in-depth understanding of the molecular intricacies governing Pashmina production in Changthangi goats, providing valuable insights into their unique genetic makeup and underlying mechanisms influencing the exceptional quality of Pashmina fibers.

Dab2 (Disabled-2), an adaptor protein, regulates self-renewal of hair follicle stem cells

Disabled 2 (Dab2), an adaptor protein, is up regulated in the hair follicle stem cells (HFSCs); however, its role in any tissue stem cells has not been studied. In the present study, we have reported that Dab2 conditional knockout (Dab2-cKO) mice exhibited a delay in the HF cycle due to perturbed activation of HFSCs. Further, Dab2-cKO mice showed a reduction in the number of HFSCs and reduced colony forming ability of HFSCs. Dab2-cKO mice showed extended quiescence of HFSCs concomitant with an increased expression of Nfatc1. Dab2-cKO mice showed a decreased expression of anti-aging genes such as Col17a1, decorin, Sirt2 and Sirt7. Dab2-cKO mice did not show full hair coat recovery in aged mice thereby suggesting an accelerated aging process. Overall, we unveil for the first time, the role of Dab2 that regulate activation and self-renewal of HFSCs.

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

Phloroglucinol Enhances Anagen Signaling and Alleviates H2O2-Induced Oxidative Stress in Human Dermal Papilla Cells

Phloroglucinol (PG) is one of the abundant isomeric benzenetriols in brown algae. Due to its polyphenolic structure, PG exhibits various biological activities. However, the impact of PG on anagen signaling and oxidative stress in human dermal papilla cells (HDPCs) is unknown. In this study, we investigated the therapeutic potential of PG for improving hair loss. A non-cytotoxic concentration of PG increased anagen-inductive genes and transcriptional activities of β-Catenin. Since several anagen-inductive genes are regulated by β-Catenin, further experiments were performed to elucidate the molecular mechanism by which PG upregulates anagen signaling. Various biochemical analyses revealed that PG upregulated β-Catenin signaling without affecting the expression of Wnt. In particular, PG elevated the phosphorylation of protein kinase B (AKT), leading to an increase in the inhibitory phosphorylation of glycogen synthase kinase 3 beta (GSK3β) at serine 9. Treatment with the selective phosphoinositide 3-kinase/AKT inhibitor, LY294002, restored the increased AKT/GSK3β/β-Catenin signaling and anagen-inductive proteins induced by PG. Moreover, conditioned medium from PG-treated HDPCs promoted the proliferation and migration of human epidermal keratinocytes via the AKT signaling pathway. Subsequently, we assessed the antioxidant activities of PG. PG ameliorated the elevated oxidative stress markers and improved the decreased anagen signaling in hydrogen peroxide (H2O2)-induced HDPCs. The senescence-associated β-galactosidase staining assay also demonstrated that the antioxidant abilities of PG effectively mitigated H2O2-induced senescence. Overall, these results indicate that PG potentially enhances anagen signaling and improves oxidative stress-induced cellular damage in HDPCs. Therefore, PG can be employed as a novel therapeutic component to ameliorate hair loss symptoms.

Effect of overexpression of KLF4 on the growth and development of hair follicles in mice

Hair follicle growth is cyclical, and hair cycle dysfunction can lead to hair follicle-related disorders, including alopecia and hirsutism. The objective was to investigate the influence and underlying mechanism of Krüppel-like factor 4 (KLF4) overexpression on hair follicle growth and development in C57BL/6 mice. To provide a theoretical basis for the biological functions of KLF4 gene in hair follicle development and hair follicle cycle, mice were assigned to three groups: experimental, overexpressing KLF4 (Ad-KLF4); control, expressing green fluorescent protein (Ad-NC); and blank, no treatment. Fur was removed from the dorsal surface, and the mice were intradermally injected with 25 μL 1 × 1010 PFU/mL adenovirus vector (Ad-KLF4 or Ad-NC) at three points. Samples were collected for molecular biological and histological analysis. It was found that mRNA and protein levels of Wnt pathway-associated factors β-catenin, LEF1, hair follicle cell proliferation-related factor Ki67, and hair follicle inner caledrin marker AE15 were all significantly greater in the Ad-NC and blank groups than in Ad-KLF4 mice (P < 0.01). These findings were confirmed by immunohistochemical analysis. Hair growth was monitored photographically for 14 days, showing an absence of growth in the injected region of the KLF4-overexpressing mice in contrast to non-overexpressing areas where hair growth was normal. HE staining showed that hair follicles in the blank and Ad-NC mice were normal, while those in the KLF4-overexpressing areas remained in telogen or early anagen with spherical dermal papillae situated at the edge of the dermis and subcutaneous tissue without an inner heel sheath. In conclusion, it was found that KLF4 downregulated key Wnt/β-catenin-associated factors during follicular regeneration in mice, reducing both follicular development and growth.

VDR is an essential regulator of hair follicle regression through the progression of cell death

Vitamin D receptor (VDR) is essential for hair follicle homeostasis as its deficiency induces hair loss, although the mechanism involved remains unknown. Our research shows that, in Vdr-knockout mice, the hair cycle is halted during the catagen stage, preceding alopecia. In addition, in Vdr-knockout hair follicles, epithelial strands that normally regress during the catagen phase persist as "surviving epithelial strands." Single-cell RNA sequencing analysis suggests that these surviving epithelial strands are formed by cells in the lower part of the hair follicle. These findings emphasize the importance of the regression phase in hair follicle regeneration and establish VDR as a regulator of the catagen stage.

Bioactive Compound-Loaded Nanocarriers for Hair Growth Promotion: Current Status and Future Perspectives

Hair loss (alopecia) has a multitude of causes, and the problem is still poorly defined. For curing alopecia, therapies are available in both natural and synthetic forms; however, natural remedies are gaining popularity due to the multiple effects of complex phytoconstituents on the scalp with fewer side effects. Evidence-based hair growth promotion by some plants has been reported for both traditional and advanced treatment approaches. Nanoarchitectonics may have the ability to evolve in the field of hair- and scalp-altering products and treatments, giving new qualities to hair that can be an effective protective layer or a technique to recover lost hair. This review will provide insights into several plant and herbal formulations that have been reported for the prevention of hair loss and stimulation of new hair growth. This review also focuses on the molecular mechanisms of hair growth/loss, several isolated phytoconstituents with hair growth-promoting properties, patents, in vivo evaluation of hair growth-promoting activity, and recent nanoarchitectonic technologies that have been explored for hair growth.

Wnt4 increases the thickness of the epidermis in burn wounds by activating canonical Wnt signalling and decreasing the cell junctions between epidermal cells

Background

Burn wound healing is a complex process and the role of Wnt ligands varies in this process. Whether and how Wnt4 functions in burn wound healing is not well understood. In this study, we aim to reveal the effects and potential mechanisms of Wnt4 in burn wound healing.

Methods

First, the expression of Wnt4 during burn wound healing was determined by immunofluorescence, Western blotting and qPCR. Then, Wnt4 was overexpressed in burn wounds. The healing rate and healing quality were analysed by gross photography and haematoxyline and eosin staining. Collagen secretion was observed by Masson staining. Vessel formation and fibroblast distribution were observed by immunostaining. Next, Wnt4 was knocked down in HaCaT cells. The migration of HaCaT cells was analysed by scratch healing and transwell assays. Next, the expression of β-catenin was detected by Western blotting and immunofluorescence. The binding of Frizzled2 and Wnt4 was detected by coimmunoprecipitation and immunofluorescence. Finally, the molecular changes induced by Wnt4 were analysed by RNA sequencing, immunofluorescence, Western blotting and qPCR in HaCaT cells and burn wound healing tissues.

Results

The expression of Wnt4 was enhanced in burn wound skin. Overexpression of Wnt4 in burn wound skin increased the thickness of epidermis. Collagen secretion, vessel formation and fibroblast distribution were not significantly impacted by Wnt4 overexpression. When Wnt4 was knocked down in HaCaT cells, the ratio of proliferating cells decreased, the ratio of apoptotic cells increased and the ratio of the healing area in the scratch healing assay to the number of migrated cells in the transwell assay decreased. The nuclear translocation of β-catenin decreased in shRNA of Wnt4 mediated by lentivirus-treated HaCaT cells and increased in Wnt4-overexpressing epidermal cells. RNA-sequencing analysis revealed that cell junction-related signalling pathways were significantly impacted by Wnt4 knockdown. The expression of the cell junction proteins was decreased by the overexpression of Wnt4.

Conclusions

Wnt4 promoted the migration of epidermal cells. Overexpression of Wnt4 increased the thickness of the burn wound. A potential mechanism for this effect is that Wnt4 binds with Frizzled2 and increases the nuclear translocation of β-catenin, thus activating the canonical Wnt signalling pathway and decreasing the cell junction between epidermal cells.

A Comprehensive Review of Mammalian Pigmentation: Paving the Way for Innovative Hair Colour-Changing Cosmetics

The natural colour of hair shafts is formed at the bulb of hair follicles, and it is coupled to the hair growth cycle. Three critical processes must happen for efficient pigmentation: (1) melanosome biogenesis in neural crest-derived melanocytes, (2) the biochemical synthesis of melanins (melanogenesis) inside melanosomes, and (3) the transfer of melanin granules to surrounding pre-cortical keratinocytes for their incorporation into nascent hair fibres. All these steps are under complex genetic control. The array of natural hair colour shades are ascribed to polymorphisms in several pigmentary genes. A myriad of factors acting via autocrine, paracrine, and endocrine mechanisms also contributes for hair colour diversity. Given the enormous social and cosmetic importance attributed to hair colour, hair dyeing is today a common practice. Nonetheless, the adverse effects of the long-term usage of such cosmetic procedures demand the development of new methods for colour change. In this context, case reports of hair lightening, darkening and repigmentation as a side-effect of the therapeutic usage of many drugs substantiate the possibility to tune hair colour by interfering with the biology of follicular pigmentary units. By scrutinizing mammalian pigmentation, this review pinpoints key targetable processes for the development of innovative cosmetics that can safely change the hair colour from the inside out.

Skin-on-a-chip strategies for human hair follicle regeneration

The number of hair loss patients increases every year, and hair loss treatment has several limitations, so research on hair is attracting attention recently. However, most current hair follicle research models are limited by their inability to replicate several key functions of the hair follicle microenvironment. To complement this, an in vitro culture system similar to the in vivo environment must be constructed. It is necessary to develop a hair-on-a-chip that implements a fully functional hair follicle model by reproducing the main characteristics of hair follicle morphogenesis and cycle. In this review, we summarize the gradation of hair follicle morphogenesis and the roles and mechanisms of molecular signals involved in the hair follicle cycle. In addition, we discuss research results of various in vitro organoid products and organ-on-a-chip-based hair follicle tissue chips for the treatment of alopecia and present future research and development directions.

Transcriptome Analysis Reveals Genes Contributed to Min Pig Villi Hair Follicle in Different Seasons

The Min pig, a local pig breed in China, has a special trait which has intermittent villus and coat hair regeneration. However, the regulation and mechanism of villus in Min pigs have not yet been described. We observed and described the phenotype of Min pig dermal villi in detail and sequenced the mRNA transcriptome of Min pig hair follicles. A total of 1520 differentially expressed genes (DEG) were obtained.K-means hierarchical clustering showed that there was a significant expression pattern difference in winter compared with summer. Gene enrichment and network analysis results showed that the hair growth in Min pigs was closely related to the composition of desmosomes and regulated by an interaction network composed of eight core genes, namely DSP, DSC3, DSG4, PKP1, TGM1, KRT4, KRT15, and KRT84. Methylation analysis of promoters of target genes showed that the PKP1 gene was demethylated. Our study will help to supplement current knowledge of the growth mechanism of different types of hair.

Vitamin A in Skin and Hair: An Update

Vitamin A is a fat-soluble micronutrient necessary for the growth of healthy skin and hair. However, both too little and too much vitamin A has deleterious effects. Retinoic acid and retinal are the main active metabolites of vitamin A. Retinoic acid dose-dependently regulates hair follicle stem cells, influencing the functioning of the hair cycle, wound healing, and melanocyte stem cells. Retinoic acid also influences melanocyte differentiation and proliferation in a dose-dependent and temporal manner. Levels of retinoids decline when exposed to ultraviolet irradiation in the skin. Retinal is necessary for the phototransduction cascade that initiates melanogenesis but the source of that retinal is currently unknown. This review discusses new research on retinoids and their effects on the skin and hair.

The stem cell quiescence and niche signaling is disturbed in the hair follicle of the hairpoor mouse, an MUHH model mouse

BACKGROUND

Hair follicle stem cells (HFSC) play an essential role in the maintenance of hair homeostasis; during the hair cycle, HFSC remain quiescent for most of its duration. The hairpoor mouse (+ /Hr^Hp), an animal model of Marie-Unna hypotrichosis (MUHH), overexpresses hairless in the bulge, inner root sheath, and outer root sheath of HF and shows the same phenotype as in MUHH patients manifesting sparse hair with progression to alopecia with age. The aim of this study was to gain an understanding of the hair cycle and the status of HFSC during the hair cycle of the hairpoor mouse in order to delineate the pathogenesis of MUHH.

METHODS

H&E staining was performed in order to define the state of the hair follicle. FACS analysis and immunostaining were performed at the 1st and 2nd telogen stages for observation of the HFSC. A label retaining assay was performed to determine the quiescent state of hair follicles. qRT-PCR was performed to determine expression of factors involved in niche signaling and Wnt signaling.

RESULTS

We observed a drastic decrease in the number of hair follicles after the 1st telogen, followed by an intensified disturbance in the hair cycle with shorter anagen as well as 2nd telogen in the hairpoor mouse. A dramatic reduction in the number of CD34 expressing bulges as well as cells was observed at the telogen of the HFs, with prominent high proliferation of bulge cells, suggesting the loss of HFSC quiescence in the hairpoor mouse. The increased cell proliferation in HF was reiterated following the synchronization of the hair cycle, leading to acceleration of HF cycling. Reduced expression of Fgf18 and Bmp6, the factors involved in HFSC quiescence, was observed in the HFSC niche of the hairpoor mouse. In addition, disturbed expression of Wnt signaling molecules including Wnt7b, Wnt10b, and Sfrp1 was observed, which induced the telogen-to-anagen transition of HFs in the hairpoor mouse.

CONCLUSIONS

These results indicate that the quiescent state of HFSC is not properly maintained in the hairpoor mouse, consequently leading HFs to the completely disarrayed hair cycle. These findings may provide an understanding of an underlying mechanism for development of alopecia with age in MUHH patients.

Sostdc1 Secreted from Cutaneous Lymphatic Vessels Acts as a Paracrine Factor for Hair Follicle Growth

In our previous study, we found that lymphatic vessels stimulate hair follicle growth through paracrine effects on dermal papilla cells. However, the paracrine factors secreted from cutaneous lymphatic vessels that can activate dermal papilla cells are still unknown. In this study, we investigated whether lymphatic endothelial cells might secrete paracrine factors that activate dermal papilla cells in vitro. We found that Sostdc1 was more expressed in lymphatic endothelial cells compared with blood vascular endothelial cells. In addition, Sostdc1 expression levels were significantly increased during the anagen phase in the back skin of C57BL/6J mice, as compared to the telogen phase. We also observed that incubation of dermal papilla cells with 200 ng/mL Sostdc1 for 72 h induced the expression levels of Lef-1, a downstream target of Wnt signaling. Taken together, our results reveal that Sostdc1, a BMP antagonist, secreted from cutaneous lymphatic vessels, may act as a paracrine factor for hair follicle growth.

Functional Differentiation of BMP7 Genes in Zebrafish: bmp7a for Dorsal-Ventral Pattern and bmp7b for Melanin Synthesis and Eye Development

Bone morphogenetic protein 7 (BMP7) belongs to the transforming growth factor β (TGF-β) family, which not only induces cartilage and bone formation, but also regulates eye development and melanoma tumorigenesis in mammals. In teleosts, BMP7 differentiates into two subtypes, bmp7a and bmp7b, which have clearly differentiated structures. To fully understand the functional differentiation of bmp7a and bmp7b in fish species, we successfully constructed bmp7a and bmp7b gene deletion mutants in zebrafish using CRISPR/Cas9-mediated gene editing technology. Our results showed that bmp7a mutation caused abnormal development of the embryo’s dorsal-ventral pattern that led to death; bmp7b mutation induced growth inhibition and increased melanin production in the skin and eye of mutants. Histological analysis revealed that melanin in the retina of the eyes in bmp7b mutants increased, and behavioral observation showed that the vision and sensitivity to food of the mutants were reduced. Transcriptome analysis of the skin and eye tissues showed that the expression changes of wnt7ba and gna14 in bmp7b mutants might promote the increase of melanin. Additionally, the eye transcriptome analysis indicated that changes in the structure of the eyes in bmp7b mutants led to defects in phototransduction, and seven DEGs (rgs9a, rgs9b, rcvrn2, guca1d, grk1b, opn1mw4, and gc2) were identified as key candidate genes that affected the photonic response of the eyes. The study revealed the functional differentiation of bmp7a and bmp7b in teleosts and the first report about the inhibitory effect of bmp7b on melanogenesis may provide useful information for the future research on human melanoma-related diseases.

Thyroid Hormone Receptor Agonist Promotes Hair Growth in Mice

Background

Thyroxine is important to maintain the normal operation of the body. Both clinical and experimental results show thyroxine is closely related to hair growth, the mechanism of which is not fully understood.

Purpose

Investigate the effect of thyroxine receptor agonist, TDM10842, for dorsal hair growth in C3H mice and explore its underlying mechanism.

Methods

Depilated mice were applied with the TDM10842, vehicle of this drug and without any materials on dorsal skin. RNA-sequencing (RNA-seq) was employed to identify the change in gene expression of skin tissues. Quantitative real-time PCR (rt-PCR) and immunoblotting were conducted to validate key differentially expressed genes (DEGs) between different groups.

Results

The TDM group showed early induction of anagen. 857, 782, and 276 differentially expressed genes were identified between 3 groups. As a critical DEG in group TDM, Pclaf was positively related to the motivation of Wnt/beta-catenin and Hedgehog signaling pathways, with a high expression of Ki67 and cyclinD1.

Conclusion

TDM10842 accelerates the anagen entrance and the potential mechanism might be the activation of Wnt/beta-catenin and Hedgehog pathways. Pclaf serves as a critical molecule involved in pathway activation, and cyclinD1 is an important effector protein downstream of the pathways.

miR-1 Regulates Differentiation and Proliferation of Goat Hair Follicle Stem Cells by Targeting IGF1R and LEF1 Genes

Hair follicle stem cells (HFSCs) play a significant role in hair development. miR-1 has been reported as an important regulatory factor that affects hair follicle growth and development, but its regulatory mechanism on HFSC development remains unknown. In this study, the molecular mechanism of miR-1 in regulating HFSC proliferation and differentiation was investigated. High-throughput RNA-seq and integrated analysis were performed to identify differentially transcribed mRNAs and microRNAs (miRNAs) in HFSCs co-cultured with dermal papilla cells (named dHFSCs) and control HFSCs. We then determined the molecular function of miR-1 in HFSCs. Compared with HFSCs, 13 differentially transcribed miRNAs were identified in dHFSCs. The in vitro results indicated that the overtranscription of miR-1 inhibited HFSC proliferation, but enhanced HFSC differentiation by targeting IGF1R and LEF1 genes. This study provides new insights into the molecular mechanisms of HFSC development. Approval ID (2014ZX08008-002).

Establishment of Angora rabbits' whisker hair follicle model and optimal culture conditions

To establish the model of whisker hair follicle culture in vitro and explore the best culture conditions, the whisker hair follicles of Angora rabbits were separated with stereomicroscope and cultured in William's E, DMEM, MEM media. The surface of the cultured whisker hair follicles was not damaged due to manual operation, resulting in the hair shaft's growth. This indicated the success of the in vitro whisker hair follicle model. The hair shaft grew at the fastest rate in the William's E culture (p < 0.05), which was significantly higher than that in the DMEM and MEM media. The hematoxylin-eosin results showed that compared to the William's E group, the atrophy of whisker hair follicles in the DMEM and MEM media was evident, especially in the MEM medium. PCNA immunofluorescence staining was employed to detect the expression of whisker hair follicles. The results showed that the PCNA positive expression of the William's E group was significantly stronger than that of the DMEM and MEM groups. Furthermore, CCK-8 and Annexin V-FITC/PI methods were used to detect the proliferation and apoptosis of the dermal papilla cells (DPCs). The results of this study provide a model for studying the hair growth of fur animals.

A systematic summary of survival and death signalling during the life of hair follicle stem cells

Hair follicle stem cells (HFSCs) are among the most widely available resources and most frequently approved model systems used for studying adult stem cells. HFSCs are particularly useful because of their self-renewal and differentiation properties. Additionally, the cyclic growth of hair follicles is driven by HFSCs. There are high expectations for the use of HFSCs as favourable systems for studying the molecular mechanisms that contribute to HFSC identification and can be applied to hair loss therapy, such as the activation or regeneration of hair follicles, and to the generation of hair using a tissue-engineering strategy. A variety of molecules are involved in the networks that critically regulate the fate of HFSCs, such as factors in hair follicle growth and development (in the Wnt pathway, Sonic hedgehog pathway, Notch pathway, and BMP pathway), and that suppress apoptotic cues (the apoptosis pathway). Here, we review the life cycle, biomarkers and functions of HFSCs, concluding with a summary of the signalling pathways involved in HFSC fate for promoting better understanding of the pathophysiological changes in the HFSC niche. Importantly, we highlight the potential mechanisms underlying the therapeutic targets involved in pathways associated with the treatment of hair loss and other disorders of skin and hair, including alopecia, skin cancer, skin inflammation, and skin wound healing.

Overexpression and Activation of αvβ3 Integrin Differentially Affects TGFβ2 Signaling in Human Trabecular Meshwork Cells

Studies from our laboratory have suggested that activation of αvβ3 integrin-mediated signaling could contribute to the fibrotic-like changes observed in primary open angle glaucoma (POAG) and glucocorticoid-induced glaucoma. To determine how αvβ3 integrin signaling could be involved in this process, RNA-Seq analysis was used to analyze the transcriptomes of immortalized trabecular meshwork (TM) cell lines overexpressing either a control vector or a wild type (WT) or a constitutively active (CA) αvβ3 integrin. Compared to control cells, hierarchical clustering, PANTHER pathway and protein-protein interaction (PPI) analysis of cells overexpressing WT-αvβ3 integrin or CA-αvβ3 integrin resulted in a significant differential expression of genes encoding for transcription factors, adhesion and cytoskeleton proteins, extracellular matrix (ECM) proteins, cytokines and GTPases. Cells overexpressing a CA-αvβ3 integrin also demonstrated an enrichment for genes encoding proteins found in TGFβ2, Wnt and cadherin signaling pathways all of which have been implicated in POAG pathogenesis. These changes were not observed in cells overexpressing WT-αvβ3 integrin. Our results suggest that activation of αvβ3 integrin signaling in TM cells could have significant impacts on TM function and POAG pathogenesis.

Photobiomodulation therapy for hair regeneration: A synergetic activation of β-CATENIN in hair follicle stem cells by ROS and paracrine WNTs

Photobiomodulation therapy (PBMT) has shown encouraging results in the treatment of hair loss. However, the mechanism by which PBMT controls cell behavior to coordinate hair cycle is unclear. Here, PBMT is found to drive quiescent hair follicle stem cell (HFSC) activation and alleviate hair follicle atrophy. Mechanistically, PBMT triggers a new hair cycle by upregulating β-CATENIN expression in HFSCs. Loss of β-Catenin (Ctnnb1) in HFSCs blocked PBMT-induced hair regeneration. Additionally, we show PBMT-induced reactive oxygen species (ROS) activate the PI3K/AKT/GSK-3β signaling pathway to inhibit proteasome degradation of β-CATENIN in HFSCs. Furthermore, PBMT promotes the expression and secretion of WNTs in skin-derived precursors (SKPs) to further activate the β-CATENIN signal in HFSCs. By contrast, eliminating ROS or inhibiting WNT secretion attenuates the activation of HFSCs triggered by PBMT. Collectively, our work suggests that PBMT promotes hair regeneration through synergetic activation of β-CATENIN in HFSCs by ROS and paracrine WNTs by SKPs.

Functional hair follicle regeneration: an updated review

The hair follicle (HF) is a highly conserved sensory organ associated with the immune response against pathogens, thermoregulation, sebum production, angiogenesis, neurogenesis and wound healing. Although recent advances in lineage-tracing techniques and the ability to profile gene expression in small populations of cells have increased the understanding of how stem cells operate during hair growth and regeneration, the construction of functional follicles with cycling activity is still a great challenge for the hair research field and for translational and clinical applications. Given that hair formation and cycling rely on tightly coordinated epithelial-mesenchymal interactions, we thus review potential cell sources with HF-inducive capacities and summarize current bioengineering strategies for HF regeneration with functional restoration.

Dietary Vitamin A Impacts Refractory Telogen

Hair follicles cycle through periods of growth (anagen), regression (catagen), rest (telogen), and release (exogen). Telogen is further divided into refractory and competent telogen based on expression of bone morphogenetic protein 4 (BMP4) and wingless-related MMTV integration site 7A (WNT7A). During refractory telogen hair follicle stem cells (HFSC) are inhibited. Retinoic acid synthesis proteins localized to the hair follicle and this localization pattern changed throughout the hair cycle. In addition, excess retinyl esters arrested hair follicles in telogen. The purpose of this study was to further define these hair cycle changes. BMP4 and WNT7A expression was also used to distinguish refractory from competent telogen in C57BL/6J mice fed different levels of retinyl esters from two previous studies. These two studies produced opposite results; and differed in the amount of retinyl esters the dams consumed and the age of the mice when the different diet began. There were a greater percentage of hair follicles in refractory telogen both when mice were bred on an unpurified diet containing copious levels of retinyl esters (study 1) and consumed excess levels of retinyl esters starting at 12 weeks of age, as well as when mice were bred on a purified diet containing adequate levels of retinyl esters (study 2) and remained on this diet at 6 weeks of age. WNT7A expression was consistent with these results. Next, the localization of vitamin A metabolism proteins in the two stages of telogen was examined. Keratin 6 (KRT6) and cellular retinoic acid binding protein 2 (CRABP2) localized almost exclusively to refractory telogen hair follicles in study 1. However, KRT6 and CRABP2 localized to both competent and refractory telogen hair follicles in mice fed adequate and high levels of retinyl esters in study 2. In mice bred and fed an unpurified diet retinol dehydrogenase SDR16C5, retinal dehydrogenase 2 (ALDH1A2), and cytochrome p450 26B1 (CYP26B1), enzymes and proteins involved in RA metabolism, localized to BMP4 positive refractory telogen hair follicles. This suggests that vitamin A may contribute to the inhibition of HFSC during refractory telogen in a dose dependent manner.

miR-140-5p in Small Extracellular Vesicles From Human Papilla Cells Stimulates Hair Growth by Promoting Proliferation of Outer Root Sheath and Hair Matrix Cells

The application of dermal papilla cells to hair follicle (HF) regeneration has attracted a great deal of attention. However, cultured dermal papilla cells (DPCs) tend to lose their capacity to induce hair growth during passage, restricting their usefulness. Accumulating evidence indicates that DPCs regulate HF growth mainly through their unique paracrine properties, raising the possibility of therapies based on extracellular vesicles (EVs). In this study, we explored the effects of EVs from high- and low-passage human scalp follicle dermal papilla cells (DP-EVs) on activation of hair growth, and investigated the underlying mechanism. DP-EVs were isolated by ultracentrifugation and cultured with human scalp follicles, hair matrix cells (MxCs), and outer root sheath cells (ORSCs), and we found low-passage DP-EVs accelerated HF elongation and cell proliferation activation. High-throughput miRNA sequencing and bioinformatics analysis identified 100 miRNAs that were differentially expressed between low- (P3) and high- (P8) passage DP-EVs. GO and KEGG pathway analysis of 1803 overlapping target genes revealed significant enrichment in the BMP/TGF-β signaling pathways. BMP2 was identified as a hub of the overlapping genes. miR-140-5p, which was highly enriched in low-passage DP-EVs, was identified as a potential regulator of BMP2. Direct repression of BMP2 by miR-140-5p was confirmed by dual-luciferase reporter assay. Moreover, overexpression and inhibition of miR-140-5p in DP-EVs suppressed and increased expression of BMP signaling components, respectively, indicating that this miRNA plays a critical role in hair growth and cell proliferation. DP-EVs transport miR-140-5p from DPCs to epithelial cells, where it downregulates BMP2. Therefore, DPC-derived vesicular miR-140-5p represents a therapeutic target for alopecia.

An Intrinsic Oscillation of Gene Networks Inside Hair Follicle Stem Cells: An Additional Layer That Can Modulate Hair Stem Cell Activities

This article explores and summarizes recent progress in and the characterization of main players in the regulation and cyclic regeneration of hair follicles. The review discusses current views and discoveries on the molecular mechanisms that allow hair follicle stem cells (hfSCs) to synergistically integrate homeostasis during quiescence and activation. Discussion elaborates on a model that shows how different populations of skin stem cells coalesce intrinsic and extrinsic mechanisms, resulting in the maintenance of stemness and hair regenerative potential during an organism’s lifespan. Primarily, we focus on the question of how the intrinsic oscillation of gene networks in hfSCs sense and respond to the surrounding niche environment. The review also investigates the existence of a cell-autonomous mechanism and the reciprocal interactions between molecular signaling axes in hfSCs and niche components, which demonstrates its critical driving force in either the activation of whole mini-organ regeneration or quiescent homeostasis maintenance. These exciting novel discoveries in skin stem cells and the surrounding niche components propose a model of the intrinsic stem cell oscillator which is potentially instructive for translational regenerative medicine. Further studies, deciphering of the distribution of molecular signals coupled with the nature of their oscillation within the stem cells and niche environments, may impact the speed and efficiency of various approaches that could stimulate the development of self-renewal and cell-based therapies for hair follicle stem cell regeneration.

Knockdown of FOXA2 Impairs Hair-Inductive Activity of Cultured Human Follicular Keratinocytes

Reciprocal interactions between hair-inductive dermal cells and epidermal cells are essential for de novo genesis of hair follicles. Recent studies have shown that outer root sheath (ORS) follicular keratinocytes can be expanded in vitro, but the cultured cells often lose receptivity to hair-inducing dermal signals. In this study, we first investigated whether the hair-inductive activity (trichogenicity) of cultured human ORS follicular keratinocytes was correlated with the cultivation period. ORS follicular keratinocytes from the scalp were cultured for 3, 4, 5, or 6 weeks and were then implanted into nude mice along with freshly isolated neonatal mouse dermal cells. We observed that the trichogenicity of the implanted ORS cells was inversely correlated with their cultivation period. These initial findings prompted us to investigate the differentially expressed genes between the short-term (20 days) and long-term (42 days) cultured ORS cells, trichogenic and non-trichogenic, respectively, by microarray analysis. We found that forkhead box protein A2 (FOXA2) was the most up-regulated transcription factor in the trichogenic ORS cells. Thus, we investigated whether the trichogenicity of the cells was affected by FOXA2 expression. We found a significant decrease in the number of induced hair follicles when the ORS cells were transfected with a FOXA2 small interfering RNA versus control small interfering RNA. Taken together, our data strongly suggest that FOXA2 significantly influences the trichogenicity of human ORS cells.

Chi-miR-30b-5p inhibits dermal papilla cells proliferation by targeting CaMKIIδ gene in cashmere goat

Background

During goat embryonic morphogenesis and postnatal initiation of hair follicle (HF) regeneration, dermal papilla (DP) cells play a vital role in hair formation. Growing evidence shows that microRNAs (miRNAs) participate in HF development and DP cell proliferation. However, the molecular mechanisms have not been thoroughly investigated.

Result

In this study, we utilized miRNA sequencing (miRNA-Seq) to identify differentially expressed miRNAs at different HF cycling stages (anagen and telogen). MiRNA-Seq has identified 411 annotated miRNAs and 130 novel miRNAs in which 29 miRNAs were up-regulated and 32 miRNAs were down-regulated in the anagen phase compared to the telogen phase. Target gene prediction and functional enrichment analysis indicated some major biological pathways related to hair cycling, such as Wnt signaling pathways, ECM-receptor interaction, VEGF signaling pathway, biosynthesis of amino acids, metabolic pathways, ribosome and oxidative phosphorylation. Also, we explored the function of chi-miR-30b-5p in regulating hair growth cycle. Similar to the HF cycling, DP cells were isolated from skin and used to investigate miRNA functions. The MTT and EdU assays showed that the viability and proliferation of DP cells were inhibited or promoted after the transfection of chi-miR-30b-5p mimic or inhibitor, respectively. Bioinformatics analysis revealed CaMKIIδ as a candidate target gene of chi-miR-30b-5p, and the dual-luciferase and western blot assay demonstrated that chi-miR-30b-5p bound to the 3’UTR of CaMKIIδ and further inhibited its translation.

Conclusion

Chi-miR-30b-5p was found to be highly expressed in the telogen than that in the anagen phase and could inhibit the proliferation of DP cells by targeting CaMKIIδ. Our study provides new information on the regulatory functions of miRNAs during HF development.

Macrophage-Derived Extracellular Vesicle Promotes Hair Growth

Hair loss is a common medical problem affecting both males and females. Dermal papilla (DP) cells are the ultimate reservoir of cells with the potential of hair regeneration in hair loss patients. Here, we analyzed the role of macrophage-derived Wnts (3a and 7b) and macrophage extracellular vesicles (MAC-EVs) in promoting hair growth. We studied the proliferation, migration, and expression of growth factors of human-DP cells in the presence or absence of MAC-EVs. Additionally, we tested the effect of MAC-EV treatment on hair growth in a mouse model and human hair follicles. Data from western blot and flow cytometry showed that MAC-EVs were enriched with Wnt3a and Wnt7b, and more than 95% were associated with their membrane. The results suggest that Wnt proteins in MAC-EVs activate the Wnt/β-catenin signaling pathways, which leads to activation of transcription factors (Axin2 and Lef1). The MAC-EVs significantly enhanced the proliferation, migration, and levels of hair-inductive markers of DP cells. Additionally, MAC-EVs phosphorylated AKT and increased the levels of the survival protein Bcl-2. The DP cells treated with MAC-EVs showed increased expression of vascular endothelial growth factor (VEGF) and keratinocyte growth factor (KGF). Treatment of Balb/c mice with MAC-EVs promoted hair follicle (HF) growth in vivo and also increased hair shaft size in a short period in human HFs. Our findings suggest that MAC-EV treatment could be clinically used as a promising novel anagen inducer in the treatment of hair loss.

Molecular Mechanisms of Hair Growth and Regeneration: Current Understanding and Novel Paradigms

Hair is a defining feature of mammals and has critical functions, including protection, production of sebum, apocrine sweat and pheromones, social and sexual interactions, thermoregulation, and provision of stem cells for skin homeostasis, regeneration, and repair. The hair follicle (HF) is considered a "mini-organ," consisting of intricate and well-organized structures which originate from HF stem and progenitor cells. Dermal papilla cells are the main components of the mesenchymal compartments in the hair bulb and are instrumental in generating signals to regulate the behavior of neighboring epithelial cells during the hair cycle. Mesenchymal-epithelial interactions within the dermal papilla niche drive HF embryonic development as well as the postnatal hair growth and regeneration cycle. This review summarizes the current understanding of HF development, repair, and regeneration, with special focus on cell signaling pathways governing these processes. In particular, we discuss emerging paradigms of molecular signaling governing the dermal papilla-epithelial cellular interactions during hair growth and maintenance and the recent progress made towards tissue engineering of human hair follicles.

Wnt activator FOXB2 drives the neuroendocrine differentiation of prostate cancer

Aberrant activation of the homeostatic Wnt signaling pathway is a hallmark of various types of cancer. In many cases, it is unclear how elevated Wnt levels are maintained in the absence of activating pathway mutations. Here we find that the uncharacterized transcription factor FOXB2, whose expression is usually restricted to the developing brain, is induced in aggressive prostate cancer. FOXB2 strongly activates Wnt signaling via the induction of multiple pathway agonists, particularly the neurogenic ligand WNT7B. Accordingly, our analyses suggest that FOXB2 imposes a neuronal differentiation program on prostate cancer cells, which is associated with treatment failure and poor prognosis. Thus, our work identifies FOXB2 as a tissue-specific Wnt activator that may play a role in prostate cancer progression.

The Wnt signaling pathway is of paramount importance for development and disease. However, the tissue-specific regulation of Wnt pathway activity remains incompletely understood. Here we identify FOXB2, an uncharacterized forkhead box family transcription factor, as a potent activator of Wnt signaling in normal and cancer cells. Mechanistically, FOXB2 induces multiple Wnt ligands, including WNT7B, which increases TCF/LEF-dependent transcription without activating Wnt coreceptor LRP6 or β-catenin. Proximity ligation and functional complementation assays identified several transcription regulators, including YY1, JUN, and DDX5, as cofactors required for FOXB2-dependent pathway activation. Although FOXB2 expression is limited in adults, it is induced in select cancers, particularly advanced prostate cancer. RNA-seq data analysis suggests that FOXB2/WNT7B expression in prostate cancer is associated with a transcriptional program that favors neuronal differentiation and decreases recurrence-free survival. Consistently, FOXB2 controls Wnt signaling and neuroendocrine differentiation of prostate cancer cell lines. Our results suggest that FOXB2 is a tissue-specific Wnt activator that promotes the malignant transformation of prostate cancer.

Roles of Wnt7a in embryo development, tissue homeostasis, and human diseases

Human Wnt family comprises 19 proteins which are critical to embryo development and tissue homeostasis. Binding to different frizzled (FZD) receptor, Wnt7a initiates both β-catenin dependent pathway, and β-catenin independent pathways such as PI3K/Akt, RAC/JNK, and extracellular signal-regulated kinase 5/peroxisome proliferator-activated receptor-γ. In the embryo, Wnt7a plays a crucial role in cerebral cortex development, synapse formation, and central nervous system vasculature formation and maintenance. Wnt7a is also involved in the development of limb and female reproductive system. Wnt7a mutation leads to human limb malformations and animal female reproductive system defects. Wnt7a is implicated in homeostasis maintenance of skeletal muscle, cartilage, cornea and hair follicle, and Wnt7a treatment may be potentially applied in skeletal muscle dystrophy, corneal damage, wound repair, and hair follicle regeneration. Wnt7a plays dual roles in human tumors. Wnt7a is downregulated in lung cancers, functioning as a tumor suppressor, however, it is upregulated in several other malignancies such as ovarian cancer, breast cancer, and glioma, acting as a tumor promoter. Moreover, Wnt7a overexpression is associated with inflammation and fibrosis, but its roles need to be further investigated.

Exosomal Micro RNAs Derived from Dermal Papilla Cells Mediate Hair Follicle Stem Cell Proliferation and Differentiation

Recent studies have demonstrated that dermal papilla cell-derived exosomes (DPC-Exos) promote the anagen stage of hair follicle (HF) growth and delay the catagen stage. However, the roles of DPC-Exos in regulating hair follicle stem cell (HFSC) quiescence and activation remain unknown. Here, we found that HFSC differentiation was induced by co-culture with DPCs, and that DPC-Exos attached to the surface of HFSCs. Using micro RNA (miRNA) high-throughput sequencing, we identified 111 miRNAs that were significantly differentially expressed between DPC-Exos and DPCs, and the predicted target genes of the top 34 differentially expressed miRNAs indicated that DPC-Exos regulate HFSCs proliferation and differentiation via genes involved in cellular signal transduction, fatty acid expression regulation, and cellular communication. The overexpression of miR-22-5p indicated that it negatively regulates HFSC proliferation and LEF1 was revealed as the direct target gene of miR-22-5p. We therefore propose the miR-22-5p-LEF1 axis as a novel pathway regulating HFSC proliferation.

A natural WNT signaling variant potently synergizes with Cdkn2ab loss in skin carcinogenesis

Cdkn2ab knockout mice, generated from 129P2 ES cells develop skin carcinomas. Here we show that the incidence of these carcinomas drops gradually in the course of backcrossing to the FVB/N background. Microsatellite analyses indicate that this cancer phenotype is linked to a 20 Mb region of 129P2 chromosome 15 harboring the Wnt7b gene, which is preferentially expressed from the 129P2 allele in skin carcinomas and derived cell lines. ChIPseq analysis shows enrichment of H3K27-Ac, a mark for active enhancers, in the 5' region of the Wnt7b 129P2 gene. The Wnt7b 129P2 allele appears sufficient to cause in vitro transformation of Cdkn2ab-deficient cell lines primarily through CDK6 activation. These results point to a critical role of the Cdkn2ab locus in keeping the oncogenic potential of physiological levels of WNT signaling in check and illustrate that GWAS-based searches for cancer predisposing allelic variants can be enhanced by including defined somatically acquired lesions as an additional input.

Dynamic Nestin expression during hair follicle maturation and the normal hair cycle

Nestin, a type-VI intermediate filament protein, serves as a marker for neural stem cells, and is also known to be expressed in follicle stem cells. Hair follicles go through repeated cycles of anagen (growth), catagen (regression) and telogen (quiescence) throughout the life of mammals following morphogenesis. In the present study it was demonstrated that in mice, the maturation of hair follicles includes the period between morphogenesis and the first anagen (4 weeks of age). Skin samples from Nestin‑green fluorescent protein (GFP)+ mice at different hair follicle stages were collected, and immunostaining for Nestin and Ki67 was performed. It was identified that during morphogenesis, Nestin‑GFP expression was rarely detected and it gradually increased during maturation (0‑4 weeks) in hair follicle dermal cells. In mature hair follicle dermal cells, Nestin and the proliferation marker Ki67 were highly expressed in anagen, while during telogen, they were markedly decreased. Additionally, lineage tracing data demonstrated that peri‑follicular Nestin+ cells during morphogenesis differentiated into cluster of differentiation 31+ cells.

Flexible fate determination ensures robust differentiation in the hair follicle

Tissue homeostasis is sustained by stem cell self-renewal and differentiation. How stem cells coordinately differentiate into multiple cell types is largely unclear. Recent studies underline the heterogeneity among stem cells or common progenitors, suggesting that coordination occurs at the stem cell/progenitor level^1-4. Here, by tracking and manipulating the same stem cells and their progeny at the single-cell level in live mice, we uncover an unanticipated flexibility of homeostatic stem cell differentiation in hair follicles. Although stem cells have been shown to be flexible upon injury, we demonstrate that hair germ stem cells at the single-cell level can flexibly establish all of the differentiation lineages even in uninjured conditions. Furthermore, stem cell-derived hair progenitors in the structure called matrix, previously thought to be unipotent, flexibly change differentiation outcomes as a consequence of unexpected dynamic relocation. Finally, the flexible cell fate determination mechanism maintains normal differentiation and tissue architecture against an ectopic differentiation stimulus induced by Wnt activation. This work provides a model of continual fate channelling and late commitment of stem cells to achieve coordinated differentiation and robust tissue architecture.

Suppression of Wnt/β-catenin signaling by EGF receptor is required for hair follicle development

Mice that lack the epidermal growth factor receptor (EGFR) fail to develop a hair coat, but the mechanism responsible for this deficit is not completely understood. Here, we show that EGFR plays a critical role to attenuate wingless-type MMTV integration site family member (Wnt)/β-catenin signaling during postnatal hair follicle development. Genetic ablation of EGFR in mice resulted in increased mitotic activity in matrix cells, apoptosis in hair follicles, and impaired differentiation of epithelial lineages that form hair. EGFR is activated in wild-type hair follicle stem cells marked with SOX9 or NFATc1 and is essential to restrain proliferation and support stem cell numbers and their quiescence. We observed elevated levels of Wnt4, 6, 7b, 10a, 10b, and 16 transcripts and hyperactivation of the β-catenin pathway in EGFR knockout follicles. Using primary keratinocytes, we linked ligand-induced EGFR activation to suppression of nascent mRNA synthesis of Wnt genes. Overexpression of the Wnt antagonist sFRP1 in mice lacking EGFR demonstrated that elevated Wnts are a major cause for the hair follicle defects. Colocalization of transforming growth factor α and Wnts regulated by EGFR in stem cells and progeny indicates that EGFR autocrine loops control Wnts. Our findings define a novel mechanism that integrates EGFR and Wnt/β-catenin pathways to coordinate the delicate balance between proliferation and differentiation during development.

Knockdown of FOXA2 enhances the osteogenic differentiation of bone marrow-derived mesenchymal stem cells partly via activation of the ERK signalling pathway

Forkhead box protein A2 (FOXA2) is a core transcription factor that controls cell differentiation and may have an important role in bone metabolism. However, the role of FOXA2 during osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) remains largely unknown. In this study, decreased expression of FOXA2 was observed during osteogenic differentiation of rat BMSCs (rBMSCs). FOXA2 knockdown significantly increased osteoblast-specific gene expression, the number of mineral deposits and alkaline phosphatase activity, whereas FOXA2 overexpression inhibited osteogenesis-specific activities. Moreover, extracellular signal-regulated protein kinase (ERK) signalling was upregulated following knockdown of FOXA2. The enhanced osteogenesis due to FOXA2 knockdown was partially rescued by an ERK inhibitor. Using a rat tibial defect model, a rBMSC sheet containing knocked down FOXA2 significantly improved bone healing. Collectively, these findings indicated that FOXA2 had an essential role in osteogenic differentiation of BMSCs, partly by activation of the ERK signalling pathway.

Therapeutic Potential of Stem Cells in Follicle Regeneration

Alopecia is caused by a variety of factors which affect the hair cycle and decrease stem cell activity and hair follicle regeneration capability. This process causes lower self-acceptance, which may result in depression and anxiety. However, an early onset of androgenic alopecia is associated with an increased incidence of the metabolic syndrome and an increased risk of the cardiac ischaemic disease. The ubiquity of alopecia provides an encouragement to seek new, more effective therapies aimed at hair follicle regeneration and neoregeneration. We know that stem cells can be used to regenerate hair in several therapeutic strategies: reversing the pathological mechanisms which contribute to hair loss, regeneration of complete hair follicles from their parts, and neogenesis of hair follicles from a stem cell culture with isolated cells or tissue engineering. Hair transplant has become a conventional treatment technique in androgenic alopecia (micrografts). Although an autologous transplant is regarded as the gold standard, its usability is limited, because of both a limited amount of material and a reduced viability of cells obtained in this way. The new therapeutic options are adipose-derived stem cells and stem cells from Wharton's jelly. They seem an ideal cell population for use in regenerative medicine because of the absence of immunogenic properties and their ease of obtainment, multipotential character, ease of differentiating into various cell lines, and considerable potential for angiogenesis. In this article, we presented advantages and limitations of using these types of cells in alopecia treatment.

Emerging nonmetabolic functions of skin fat

Although the major white adipose depots evolved primarily to store energy, secrete hormones and thermo-insulate the body, multiple secondary depots developed additional specialized and unconventional functions. Unlike any other fat tissue, dermal white adipose tissue (dWAT) evolved a large repertoire of novel features that are central to skin physiology, which we discuss in this Review. dWAT exists in close proximity to hair follicles, the principal appendages of the skin that periodically grow new hairs. Responding to multiple hair-derived signals, dWAT becomes closely connected to cycling hair follicles and periodically cycles itself. At the onset of new hair growth, hair follicles secrete activators of adipogenesis, while at the end of hair growth, a reduction in the secretion of activators or potentially, an increase in the secretion of inhibitors of adipogenesis, results in fat lipolysis. Hair-driven cycles of dWAT remodelling are uncoupled from size changes in other adipose depots that are controlled instead by systemic metabolic demands. Rich in growth factors, dWAT reciprocally signals to hair follicles, altering the activation state of their stem cells and modulating the pace of hair regrowth. dWAT cells also facilitate skin repair following injury and infection. In response to wounding, adipose progenitors secrete repair-inducing activators, while bacteria-sensing adipocytes produce antimicrobial peptides, thus aiding innate immune responses in the skin.

Identification and Characterization of Hair Follicle Stem Cells

Hair follicle stem cells (HFSCs) are epithelial cells that inhabit in the bulge region of hair follicles. They govern development of hair follicle as well as periodically regeneration of hair follicle. Under special condition, they also play roles in homeostasis of skin and other skin appendages. To characterize HFSCs in vitro, HFSCs must be isolated and cultured. In this chapter, we introduce a mechanical method to isolate HFSCs from mouse vibrissa hair follicle, and a modified method to culture isolated HFSCs. We also describe methods to characterize HFSCs, including clone formation assay and chamber graft assay.

Structural Characterization and Association of Ovine Dickkopf-1 Gene with Wool Production and Quality Traits in Chinese Merino

Dickkopf-1 (DKK1) is an inhibitor of canonical Wnt signaling pathway and regulates hair follicle morphogenesis and cycling. To investigate the potential involvement of DKK1 in wool production and quality traits, we characterized the genomic structure of ovine DKK1, performed polymorphism detection and association analysis of ovine DKK1 with wool production and quality traits in Chinese Merino. Our results showed that ovine DKK1 consists of four exons and three introns, which encodes a protein of 262 amino acids. The coding sequence of ovine DKK1 and its deduced amino acid sequence were highly conserved in mammals. Eleven single nucleotide polymorphisms (SNPs) were identified within the ovine DKK1 genomic region. Gene-wide association analysis showed that SNP5 was significantly associated with mean fiber diameter (MFD) in the B (selected for long wool fiber and high-quality wool), PW (selected for high reproductive capacity, high clean wool yield and high-quality wool) and U (selected for long wool fiber with good uniformity, high wool yield and lower fiber diameter) strains (p < 4.55 × 10-3 = 0.05/11). Single Nucleotide Polymorphisms wide association analysis showed that SNP8 was significantly associated with MFD in A strain and fleece weight in A (selected for large body size), PM (selected for large body size, high reproductive capacity and high meat yield) and SF (selected for mean fiber diameter less than 18 μm and wool fiber length between 5 and 9 cm) strains (p < 0.05), SNP9 was significantly associated with curvature in B and U strains (p < 0.05) and SNP10 was significantly associated with coefficient of variation of fiber diameter in A, PW and PM strains and standard deviation of fiber diameter in A and PM strains (p < 0.05). The haplotypes derived from these 11 identified SNPs were significantly associated with MFD (p < 0.05). In conclusion, our results suggest that DKK1 may be a major gene controlling wool production and quality traits, also the identified SNPs (SNPs5, 8, 9 and 10) might be used as potential molecular markers for improving sheep wool production and quality in sheep breeding.

Integrated analysis of coding genes and non-coding RNAs during hair follicle cycle of cashmere goat (Capra hircus)

Background

Cashmere growth is a seasonal and cyclic phenomenon under the control of photoperiod and multiple stimulatory and inhibitory signals. Beyond relevant coding genes, microRNA (miRNA) and long non coding RNA (lncRNA) play an indispensable role in hair follicle (HF) development and skin homeostasis. Furthermore, the influence of lncRNA upon miRNA function is also rapidly emerging. However, little is known about miRNAs, lncRNAs and their functions as well as their interactions on cashmere development and cycling.

Result

Here, based on lncRNA and miRNA high-throughput sequencing and bioinformatics analysis, we have identified 1108 lncRNAs and 541 miRNAs in cashmere goat skin during anagen and telogen. Compared with telogen, 1388 coding genes, 41 lncRNAs and 15 miRNAs were upregulated, while 1104 coding genes, 157 lncRNAs and 8 miRNAs were downregulated in anagen (adjusted P-value ≤0.05 and relative fold-change ≥2). Subsequently, we investigated the impact of lncRNAs on their target genes in cis and trans, indicating that these lncRNAs are functionally conserved during HF development and cycling. Furthermore, miRNA-mRNA and miRNA-lncRNA interaction were identified through the bioinformatics algorithm miRanda, then the ceRNA networks, miR-221-5p-lnc_000679-WNT3, miR-34a-lnc_000181-GATA3 and miR-214-3p-lnc_000344-SMAD3, were constructed under defined rules, to illustrate their roles in cashmere goat HF biology.

Conclusion

The present study provides a resource for lncRNA, miRNA and mRNA studies in cashmere cycling and development. We also demonstrate potential ceRNA regulatory networks in cashmere goat HF cycling for the first time. It expands our knowledge about lncRNA and miRNA biology as well as contributes to the annotation of the goat genome.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4145-0) contains supplementary material, which is available to authorized users.

Aging in hair follicle stem cells and niche microenvironment

Hair graying and hair loss are prominent and common characteristics of the elderly population. In some individuals these processes can significantly impact their quality of life, leading to depression, anxiety and other serious mental health problems. Accordingly, there has been much interest in understanding the complex physiological changes within the hair follicle in the aging individual. It is now known that hair follicles represent a prototypical stem cell niche, where both micro- and macroenvironmental influences are integrated alongside stem cell-stem cell and stem cell-stem niche interactions to determine hair growth or hair follicle senescence. Recent studies have identified imbalanced stem cell differentiation and altered stem cell activity as important factors during hair loss, indicating new avenues for the development of therapeutic agents to stimulate hair growth. Here, we pull together the latest findings on the hair follicle stem cell niche and the multifactorial interactions underlying the various forms of hair loss.

After Skin Wounding, Noncoding dsRNA Coordinates Prostaglandins and Wnts to Promote Regeneration

In a rare example akin to organogenesis in adult mammals, large wounds in mice lead to de novo morphogenesis of hair follicles. It is still not fully clear what controls this process, known as wound-induced hair neogenesis (WIHN). In other tissues, prostaglandin E₂ is an important effector of regeneration and has been shown to stimulate the Wnt/β-catenin pathway, which in turn is known to control WIHN. Previously, our group has shown that noncoding double-stranded RNA (dsRNA) released during wounding is both necessary and sufficient to stimulate WIHN through toll-like receptor 3. Here, we hypothesized that dsRNA similarly induces the β-catenin pathway through prostaglandin E₂. We found that WIHN levels correlate closely with Wnt7b production in vivo and that dsRNA potently induces Wnt7b in a manner that requires Ptgs2. The Ptgs2 inhibitor celecoxib reduces dsRNA-induced WIHN and Wnt7b, and exogenous prostaglandin E₂ can rescue WIHN and Wnt7b. Although other Wnts and pathways likely contribute, these results highlight noncoding dsRNA as an upstream coordinator of prostaglandin and Wnt levels in regeneration.

A multi-scale model for hair follicles reveals heterogeneous domains driving rapid spatiotemporal hair growth patterning

The control principles behind robust cyclic regeneration of hair follicles (HFs) remain unclear. Using multi-scale modeling, we show that coupling inhibitors and activators with physical growth of HFs is sufficient to drive periodicity and excitability of hair regeneration. Model simulations and experimental data reveal that mouse skin behaves as a heterogeneous regenerative field, composed of anatomical domains where HFs have distinct cycling dynamics. Interactions between fast-cycling chin and ventral HFs and slow-cycling dorsal HFs produce bilaterally symmetric patterns. Ear skin behaves as a hyper-refractory domain with HFs in extended rest phase. Such hyper-refractivity relates to high levels of BMP ligands and WNT antagonists, in part expressed by ear-specific cartilage and muscle. Hair growth stops at the boundaries with hyper-refractory ears and anatomically discontinuous eyelids, generating wave-breaking effects. We posit that similar mechanisms for coupled regeneration with dominant activator, hyper-refractory, and wave-breaker regions can operate in other actively renewing organs.