Shh maintains dermal papilla identity and hair morphogenesis via a Noggin-Shh regulatory loop

Dynamic duo: Cell-extracellular matrix interactions in hair follicle development and regeneration

Ectodermal organs, such as hair follicles, originate from simple epithelial and mesenchymal sheets through a complex developmental process driven by interactions between these cell types. This process involves dermal condensation, placode formation, bud morphogenesis, and organogenesis, and all of these processes require intricate interactions among various tissues. Recent research has emphasized the crucial role of reciprocal and dynamic interactions between cells and the extracellular matrix (ECM), referred to as the "dynamic duo", in the development of ectodermal organs. These interactions provide spatially and temporally changing biophysical and biochemical cues within tissues. Using the hair follicle as an example, this review highlights two types of cell-ECM adhesion units-focal adhesion-type and hemidesmosome-type adhesion units-that facilitate communication between epithelial and mesenchymal cells. This review further explores how these adhesion units, along with other cell-ECM interactions, evolve during hair follicle development and regeneration, underscoring their importance in guiding both developmental and regenerative processes.

Glycogen Phosphorylase Inhibitor Promotes Hair Growth via Protecting from Oxidative-Stress and Regulating Glycogen Breakdown in Human Hair follicles

Hair growth cycles are mainly regulated by human dermal papilla cells (hDPCs) and human outer root sheath cells (hORSCs). Protecting hDPCs from excessive oxidative stress and hORSCs from glycogen phosphorylase (PYGL) is crucial to maintaining the hair growth phase, anagen. In this study, we developed a new PYGL inhibitor, Hydroxytrimethylpyridinyl Methylindolecarboxamide (HTPI) and assessed its potential to prevent hair loss. HTPI reduced oxidative damage, preventing cell death and restored decreased level of anagen marker ALP and its related genes induced by hydrogen peroxide in hDPCs. Moreover, HTPI inhibited glycogen degradation and induced cell survival under glucose starvation in hORSCs. In ex-vivo culture, HTPI significantly enhanced hair growth compared to the control with minoxidil showing comparable results. Overall, these findings suggest that HTPI has significant potential as a therapeutic agent for the prevention and treatment of hair loss.

Skin Development and Disease: A Molecular Perspective

Skin, the largest organ in the human body, is a crucial protective barrier that plays essential roles in thermoregulation, sensation, and immune defence. This complex organ undergoes intricate processes of development. Skin development initiates during the embryonic stage, orchestrated by molecular cues that control epidermal specification, commitment, stratification, terminal differentiation, and appendage growth. Key signalling pathways are integral in coordinating the development of the epidermis, hair follicles, and sweat glands. The complex interplay among these pathways is vital for the appropriate formation and functionality of the skin. Disruptions in multiple molecular pathways can give rise to a spectrum of skin diseases, from congenital skin disorders to cancers. By delving into the molecular mechanisms implicated in developmental processes, as well as in the pathogenesis of diseases, this narrative review aims to present a comprehensive understanding of these aspects. Such knowledge paves the way for developing innovative targeted therapies and personalised treatment approaches for various skin conditions.

Triethylene Glycol Squalene Improves Hair Regeneration by Maintaining the Inductive Capacity of Human Dermal Papilla Cells and Preventing Premature Aging

De novo hair follicle (HF) regeneration, achieved through the replenishment of the dermal papilla (DP), acknowledged as the principal orchestrator of the hair growth cycle, is emerging as a prospective therapeutic intervention for alopecia. Nonetheless, multiple attempts have shown that these cells lose key inductive properties when cultured in a two-dimensional (2D) monolayer, leading to precocious senescence engendered by oxidative stress and inflammatory processes. Consequently, the three-dimensional (3D) spheroid technique is presently widely employed for DP cell culture. Nevertheless, substantiating the regenerative potential of these cells within the hair follicle (HF) milieu remains a challenge. In this current study, we aim to find a new approach to activate the inductive properties of DP cells. This involves the application of hair-growth-stimulating agents that not only exhibit concurrent protective efficacy against the aging process but also induce HF regeneration. To achieve this objective, we initially synthesized a novel highly amphiphilic derivative derived from squalene (SQ), named triethylene glycol squalene (Tri-SQ). Squalene itself is a potent antioxidant and anti-inflammatory compound traditionally employed as a drug carrier for alopecia treatment. However, its application is limited due to its low solubility. Subsequently, we applied this newly synthesized derivative to DP cells. The data obtained demonstrated that the derivative exhibits robust antioxidant and anti-inflammatory activities while concurrently promoting the expression of genes associated with hair growth. Moreover, to further assess the hair regrowth inductive properties of DP cells, we cultured the cells and treated them with Tri-SQ within a 3D spheroid system. Subsequently, these treated cells were injected into the previously depilated dorsal area of six-week-old male C57BL/6 mice. Results revealed that 20 days postinjection, a complete regrowth of hair in the previously hairless area, particularly evident in the case of 3D spheroids treated with the derivative, was observed. Additionally, histological and molecular analyses demonstrated an upregulation of markers associated with hair growth and a concurrent decrease in aging hallmarks, specifically in the 3D spheroids treated with the compound. In summary, our approach, which involves the treatment of Tri-SQ combined with a 3D spheroid system, exhibited a notably robust stimulating effect. This effect was observed in the induction of inductive properties in DP cells, leading to HF regeneration, and concurrently, it demonstrated an inhibitory effect on cellular and follicular aging.

Shh Gene Regulates the Proliferation and Apoptosis of Dermal Papilla Cells to Affect Its Differential Expression in Secondary Hair Follicle Growth Cycle of Cashmere Goats

Sonic hedgehog (Shh) is a component of the Hedgehog signaling pathway, playing an important role in regulating cell proliferation, differentiation, apoptosis, and the repair of damaged organisms. To further clarify the expression pattern of Shh gene in the secondary hair follicle growth cycle of cashmere goats and its mechanism of action on secondary hair follicle papilla cells, and improve cashmere quality, in this study, we took Inner Mongolia Albas white cashmere goats as the research objects and collected skin samples at different growth stages to obtain secondary hair follicles, detected Shh and its gene expression by RT-qPCR, Western blot, immunohistochemistry, and other techniques, while we also cultured DPCs in vitro. Shh gene overexpression and interference vectors were constructed, and the effects of Shh gene on the proliferation and apoptosis of DPCs were studied through cell transfection technology. The results showed that there are significant differences in Shh and its gene expression in the secondary hair follicle growth cycle skins of cashmere goats, with the highest expression level in anagen, followed by catagen, and the lowest expression level in telogen. Shh was mainly expressed in the inner root sheath, outer root sheath, and secondary hair follicle papilla. After the overexpression of Shh gene, the proliferation and vitality of the hair papilla cells were enhanced compared to the interference group. After Shh gene interference, the apoptosis rate of the cells increased, indicating that Shh gene can regulate downstream Ptch, Smo, and Gli2 gene expression to promote the proliferation of DPCs, and thus form its expression pattern in the secondary hair follicle growth cycle of cashmere goats.

Dermal β-Catenin Is Required for Hedgehog-Driven Hair Follicle Neogenesis

Hair follicle neogenesis (HFN) occurs after large skin excisions in mice, serving as a rare regenerative model in mammalian wound healing. Wound healing typically results in fibrosis in mice and humans. We previously showed that small skin excisions in mice result in scarring devoid of HFN, displaying features of nonregenerative healing, and hedgehog (Hh) activation in the dermis of such wounds can induce HFN. In this study, we sought to verify the role of dermal Wnt/β-catenin signaling in HFN because this pathway is essential for hair follicle development but is also paradoxically well-characterized in fibrosis of adult wounds. By deletion of β-catenin in large wound myofibroblasts, we show that Wnt/β-catenin signaling is required for endogenous mechanisms of HFN. By utilizing a combined mouse model that simultaneously induces deletion of β-catenin and constitutive activation of Smoothened in myofibroblasts, we also found that β-catenin is required for Hh-driven dermal papilla formation. Transcriptome analysis confirms that Wnt/β-catenin and Hh pathways are activated in dermal papilla cells. Our results indicate that Wnt-active fibrotic status may also create a permissive state for the regenerative function of Hh, suggesting that activation of both Wnt and Hh pathways in skin wound fibroblasts must be ensured in future strategies to promote HFN.

Modelling Human Hair Follicles-Lessons from Animal Models and Beyond

The hair follicle is a specialized appendage of the skin that is critical for multiple functions, including thermoregulation, immune surveillance, and sebum production. Mammals are born with a fixed number of hair follicles that develop embryonically. Postnatally, these hair follicles undergo regenerative cycles of regression and growth that recapitulate many of the embryonic signaling pathways. Furthermore, hair cycles have a direct impact on skin regeneration in homeostasis, cutaneous wound healing, and disease conditions such as alopecia. Here, we review the current knowledge of hair follicle formation during embryonic development and the post-natal hair cycle, with an emphasis on the molecular signaling pathways underlying these processes. We then discuss efforts to capitalize on the field's understanding of in vivo mechanisms to bioengineer hair follicles or hair-bearing skin in vitro and how such models may be further improved to develop strategies for hair regeneration.

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.

MiR-23b and miR-133 Cotarget TGFβ2/NOTCH1 in Sheep Dermal Fibroblasts, Affecting Hair Follicle Development

Wool is produced and controlled by hair follicles (HFs). However, little is known about the mechanisms involved in HF development and regulation. Sheep dermal fibroblasts (SDFs) play a key role in the initial stage of HF development. Analyzing the molecular mechanism that regulates early HF development in superfine wool sheep is of great importance for better understanding the HF morphogenesis process and for the breeding of fine wool sheep. Here, we show that two microRNAs (miRNAs) affect the development of HFs by targeting two genes that are expressed by SDFs. Meanwhile, the overexpression and inhibition of oar-miR-23b and oar-miR-133 in SDFs cells and cell proliferation, apoptosis, and migration were further detected using a CCK-8 assay, an Annexin V-FITC assay, a Transwell assay, and flow cytometry. We found that oar-miR-23b, oar-miR-133, and their cotarget genes TGFβ2 and NOTCH1 were differentially expressed during the six stages of HF development in superfine wool sheep. Oar-miR-23b and oar-miR-133 inhibited the proliferation and migration of SDFs and promoted the apoptosis of SDFs through TGFβ2 and NOTCH1. oar-miR-23b and oar-miR-133 inhibited the proliferation and migration of SDFs by jointly targeting TGFβ2 and NOTCH1, thereby inhibiting the development of superfine wool HFs. Our research provides a molecular marker that can be used to guide the breeding of ultrafine wool sheep.

The Biology and Genomics of Human Hair Follicles: A Focus on Androgenetic Alopecia

Androgenetic alopecia is a highly prevalent condition mainly affecting men. This complex trait is related to aging and genetics; however, multiple other factors, for example, lifestyle, are also involved. Despite its prevalence, the underlying biology of androgenetic alopecia remains elusive, and thus advances in its treatment have been hindered. Herein, we review the functional anatomy of hair follicles and the cell signaling events that play a role in follicle cycling. We also discuss the pathology of androgenetic alopecia and the known molecular mechanisms underlying this condition. Additionally, we describe studies comparing the transcriptional differences in hair follicles between balding and non-balding scalp regions. Given the genetic contribution, we also discuss the most significant risk variants found to be associated with androgenetic alopecia. A more comprehensive understanding of this pathology may be generated through using multi-omics approaches.

Local and systemic mechanisms that control the hair follicle stem cell niche

Hair follicles are essential appendages of the mammalian skin, as hair performs vital functions of protection, thermoregulation and sensation. Hair follicles harbour exceptional regenerative abilities as they contain multiple somatic stem cell populations such as hair follicle stem cells (HFSCs) and melanocyte stem cells. Surrounding the stem cells and their progeny, diverse groups of cells and extracellular matrix proteins are organized to form a microenvironment (called 'niche') that serves to promote and maintain the optimal functioning of these stem cell populations. Recent studies have shed light on the intricate nature of the HFSC niche and its crucial role in regulating hair follicle regeneration. In this Review, we describe how the niche serves as a signalling hub, communicating, deciphering and integrating both local signals within the skin and systemic inputs from the body and environment to modulate HFSC activity. We delve into the recent advancements in identifying the cellular and molecular nature of the niche, providing a holistic perspective on its essential functions in hair follicle morphogenesis, regeneration and ageing.

Coexpression analysis of angiogenesis, proliferation, apoptosis, autophagy and SHH pathway genes involved in skin expansion

Skin and soft tissue expansion is a widely used technique in plastic surgery. However, the regulatory mechanisms associated with cellular processes involved in skin expansion are not well elucidated. In the present study, we aimed at exploring the transcriptome changes associated with skin expansion and profiling the difference in gene expression between the skin tissue in the top of the dilator and the skin tissue in the side of the dilator. A mouse model of skin expansion was established and RNA sequencing (RNA-Seq) was performed on samples collected at different time points. Differential expression analysis was performed using the DESeq2 package while STEM was used for time series clustering profiling. The regulatory networks were established and the functions of sets of genes were analyzed. The mRNA expression levels of candidate genes were validated by the quantitative RT-PCR. Among the skin tissue in the top of the dilator and normal samples at days 1, 3, 7, 14 and 28, 53 commonly upregulated and 7 commonly downregulated genes were identified while among the skin tissue in the side of the dilator and normal samples, 98 downregulated and 255 upregulated genes were identified. Genes differentially expressed among the skin tissue in the top of the dilator and normal samples were involved in coagulation and proliferation-associated pathways while those among the skin tissue in the side of the dilator and normal samples were involved in the inflammation, immune response, and defense response. Among the skin tissue in the top of the dilator and the skin tissue in the side of the dilator samples, 161 were constantly upregulated while 27 were constantly downregulated; these genes were enriched in the biological processes of cell adhesion and regulation of cell proliferation (n = 11). Furthermore, we identified that SHH signaling genes formed a coexpression regulatory network with cellular proliferation, apoptosis, autophagy and angiogenesis-related genes in the expanded skin. In conclusion, our findings can promote research and understanding of the mechanism of skin expansion and will find application in plastic surgery.

Mesenchyme governs hair follicle induction

Tissue interactions are essential for guiding organ development and regeneration. Hair follicle formation relies on inductive signalling between two tissues, the embryonic surface epithelium and the adjacent mesenchyme. Although previous research has highlighted the hair-inducing potential of the mesenchymal component of the hair follicle - the dermal papilla and its precursor, the dermal condensate - the source and nature of the primary inductive signal before dermal condensate formation have remained elusive. Here, we performed epithelial-mesenchymal tissue recombination experiments using hair-forming back skin and glabrous plantar skin from mouse embryos to unveil that the back skin mesenchyme is inductive even before dermal condensate formation. Moreover, the naïve, unpatterned mesenchyme was sufficient to trigger hair follicle formation even in the oral epithelium. Building on previous knowledge, we explored the hair-inductive ability of the Wnt agonist R-spondin 1 and a Bmp receptor inhibitor in embryonic skin explants. Although R-spondin 1 instigated precocious placode-specific transcriptional responses, it was insufficient for hair follicle induction, either alone or in combination with Bmp receptor inhibition. Our findings pave the way for identifying the hair follicle-inducing cue.

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.

Hedgehog signaling is required for endometrial remodeling and myometrial homeostasis in the cycling mouse uterus

Decades of work demonstrate that the mammalian estrous cycle is controlled by cycling steroid hormones. However, the signaling mechanisms that act downstream, linking hormonal action to the physical remodeling of the cycling uterus, remain unclear. To address this issue, we analyzed gene expression at all stages of the mouse estrous cycle. Strikingly, we found that several genetic programs well-known to control tissue morphogenesis in developing embryos displayed cyclical patterns of expression. We find that most of the genetic architectures of Hedgehog signaling (ligands, receptors, effectors, and transcription factors) are transcribed cyclically in the uterus, and that conditional disruption of the Hedgehog receptor smoothened not only elicits a failure of normal cyclical thickening of the endometrial lining but also induces aberrant deformation of the uterine smooth muscle. Together, our data shed light on the mechanisms underlying normal uterine remodeling specifically and cyclical gene expression generally.

Transcriptomic Analysis Reveals Candidate Ligand-Receptor Pairs and Signaling Networks Mediating Intercellular Communication between Hair Matrix Cells and Dermal Papilla Cells from Cashmere Goats

Hair fiber growth is determined by the spatiotemporally controlled proliferation, differentiation, and apoptosis of hair matrix cells (HMCs) inside the hair follicle (HF); however, dermal papilla cells (DPCs), the cell population surrounded by HMCs, manipulate the above processes via intercellular crosstalk with HMCs. Therefore, exploring how the mutual commutations between the cells are molecularly achieved is vital to understanding the mechanisms underlying hair growth. Here, based on our previous successes in cultivating HMCs and DPCs from cashmere goats, we combined a series of techniques, including in vitro cell coculture, transcriptome sequencing, and bioinformatic analysis, to uncover ligand-receptor pairs and signaling networks mediating intercellular crosstalk. Firstly, we found that direct cellular interaction significantly alters cell cycle distribution patterns and changes the gene expression profiles of both cells at the global level. Next, we constructed the networks of ligand-receptor pairs mediating intercellular autocrine or paracrine crosstalk between the cells. A few pairs, such as LEP-LEPR, IL6-EGFR, RSPO1-LRP6, and ADM-CALCRL, are found to have known or potential roles in hair growth by acting as bridges linking cells. Further, we inferred the signaling axis connecting the cells from transcriptomic data with the advantage of CCCExplorer. Certain pathways, including INHBA-ACVR2A/ACVR2B-ACVR1/ACVR1B-SMAD3, were predicted as the axis mediating the promotive effect of INHBA on hair growth via paracrine crosstalk between DPCs and HMCs. Finally, we verified that LEP-LEPR and IL1A-IL1R1 are pivotal ligand-receptor pairs involved in autocrine and paracrine communication of DPCs and HMCs to DPCs, respectively. Our study provides a comprehensive landscape of intercellular crosstalk between key cell types inside HF at the molecular level, which is helpful for an in-depth understanding of the mechanisms related to hair growth.

Lrig1-expressing epidermal progenitors require SCD1 to maintain the dermal papilla niche

Niche cells are widely known to regulate stem/progenitor cells in many mammalian tissues. In the hair, dermal papilla niche cells are well accepted to regulate hair stem/progenitor cells. However, how niche cells themselves are maintained is largely unknown. We present evidence implicating hair matrix progenitors and the lipid modifying enzyme, Stearoyl CoA Desaturase 1, in the regulation of the dermal papilla niche during the anagen-catagen transition of the mouse hair cycle. Our data suggest that this takes place via autocrine Wnt signalling and paracrine Hedgehog signalling. To our knowledge, this is the first report demonstrating a potential role for matrix progenitor cells in maintaining the dermal papilla niche.

Tetrathiomolybdate Decreases the Expression of Alkaline Phosphatase in Dermal Papilla Cells by Increasing Mitochondrial ROS Production

Dermal papilla cells (DPCs) play important roles in hair growth regulation. However, strategies to regrow hair are lacking. Here, global proteomic profiling identified the tetrathiomolybdate (TM)-mediated inactivation of copper (Cu) depletion-dependent mitochondrial cytochrome c oxidase (COX) as the primary metabolic defect in DPCs, leading to decreased Adenosine Triphosphate (ATP) production, mitochondrial membrane potential depolarization, increased total cellular reactive oxygen species (ROS) levels, and reduced expression of the key marker of hair growth in DPCs. By using several known mitochondrial inhibitors, we found that excessive ROS production was responsible for the impairment of DPC function. We therefore subsequently showed that two ROS scavengers, N-acetyl cysteine (NAC) and ascorbic acid (AA), partially prevented the TM- and ROS-mediated inhibition of alkaline phosphatase (ALP). Overall, these findings established a direct link between Cu and the key marker of DPCs, whereby copper depletion strongly impaired the key marker of hair growth in the DPCs by increasing excessive ROS production.

The dermal papilla dilemma and potential breakthroughs in bioengineering hair follicles

The generation and growing of de novo hair follicles is the most daring hair replacement approach to treat alopecia. This approach has been explored at least since the 1960s without major success. Latest in the 1980s, the realization that the mesenchymal compartment of hair follicles, the dermal papilla (DP), is the crucial signaling center and element required for fulfilling this vision of hair follicle engineering, propelled research into the fibroblasts that occupy the DP. However, working with DP fibroblasts has been stubbornly frustrating. Decades of work in understanding the nature of DP fibroblasts in vitro and in vivo have led to the appreciation that hair follicle biology is complex, and the dermal papilla is an enigma. Functional DP fibroblasts tend to aggregate in 2D culture, while impaired DP cells do not. This fact has stimulated recent approaches to overcome the hurdles to DP cell culture by mimicking their natural habitat, such as growing DP fibroblasts in three dimensions (3D) by their self-aggregation, adopting 3D matrix scaffold, or bioprinting 3D microstructures. Furthermore, including keratinocytes in the mix to form hair follicle-like composite structures has been explored but remains a far cry from a useful and affordable method to generate human hair follicles in sufficient quantity and quality in a practical time frame for patients. This suggests that the current strategies may have reached their limitations in achieving successful hair follicle bioengineering for clinical applications. Novel approaches are required to overcome these barriers, such as focusing on embryonic cell types and processes in combination with emerging techniques.

Regulation of secondary hair follicle cycle in cashmere goats by miR-877-3p targeting IGFBP5 gene

Cashmere, a highly valuable animal product derived from cashmere goats, holds significant economic importance. MiRNAs serve as crucial regulators in the developmental processes of mammalian hair follicles. Understanding the regulation of miRNAs during the hair follicle cycle is essential for enhancing cashmere quality. In this investigation, we employed high-throughput sequencing technology to analyze the expression profiles of miRNAs in the secondary hair follicles of Jiangnan cashmere goats at different stages. Through bioinformatics analysis, we identified differentially expressed miRNAs (DE miRNAs). The regulatory relationships between miRNAs and their target genes were verified using multiple techniques, including RT-qPCR, western blot, Dual-Luciferase Reporter, and CKK-8 assays. Our findings revealed the presence of 193 DE miRNAs during various stages of the hair follicle cycle in Jiangnan cashmere goats. Based on the previously obtained mRNA data, the target genes of DE miRNA were predicted, and 1,472 negative regulatory relationships between DE miRNAs and target genes were obtained. Notably, the expression of chi-miR-877-3p was down-regulated during the telogen (Tn) phase compared to the anagen (An) and catagen (Cn) phases, while the IGFBP5 gene exhibited up-regulation. Further validation experiments confirmed that overexpression of chi-miR-877-3p in dermal papilla cells suppressed IGFBP5 gene expression and facilitated cell proliferation. The results of this study provide novel insights for analyzing the hair follicle cycle.

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.

Effect of Sox18 on the Induction Ability of Dermal Papilla Cells in Hu Sheep

Sox18 is a developmental gene that encodes transcription factors. It has been indicated as be a key gene affecting the growth and development of hair follicles, in which dermal papilla cells (DPCs) have been demonstrated to play an important role through their ability to induce the formation of hair follicles. Pre-laboratory studies have found that Sox18 is differentially expressed in the dermal papilla cells of different pattern types of Hu sheep. We speculated that Sox18 plays an important role in the dermal papilla cells of Hu sheep. In our study, we analyzed the effect of Sox18 on the induction ability of DPCs in order to elucidate the function and molecular mechanism of Sox18 in the DPCs of Hu sheep. We first identified the expression of Sox18 in the DPCs of Hu sheep by immunofluorescence staining. We then used alkaline phosphatase staining, cell morphology observations and RT-PCR to detect the effect of Sox18 on the induction of DPCs after overexpression of or interference with Sox18. We also used RT-PCR, WB and immunofluorescence staining to detect the effect of Sox18 on the Wnt/β-catenin signal pathway in DPCs. We found that Sox18 was specifically expressed in the DPCs of Hu sheep, and that Sox18 could enhance the alkaline phosphatase activity in the DPCs of Hu sheep and accelerate cell agglutination. The results of RT-PCR revealed that Sox18 promoted the mRNA expression of Versican, HHIP and FGFRI, and inhibited the mRNA expression of BMP4 and WIF1. Further studies showed that Sox18 promoted the expression of β-catenin and activated the Wnt/β-catenin signal pathway in DPCs. When the Wnt/β-catenin signal pathway of DPCs was activated, the induction ability of DPCs was enhanced. Overall, we believe that Sox18 could enhance the induction ability of DPCs in Hu sheep and regulate the induction ability of DPCs through the Wnt/β-catenin signal pathway.

Sonic Hedgehog signalling in the regulation of barrier tissue homeostasis and inflammation

Epithelial barrier tissues such as the skin and airway form an essential interface between the mammalian host and its external environment. These physical barriers are crucial to prevent damage and disease from environmental insults and allergens. Failure to maintain barrier function against such risks can lead to severe inflammatory disorders, including atopic dermatitis and asthma. Here, we discuss the role of the morphogen Sonic Hedgehog in postnatal skin and lung and the impact of Shh signalling on repair, inflammation, and atopic disease in these tissues.

Integrated analysis of miRNAs and mRNA profiling reveals the potential roles of miRNAs in sheep hair follicle development

BACKGROUND

Merino sheep exhibit high wool production and excellent wool quality. The fleece of Merino sheep is predominantly composed of wool fibers grown from hair follicles (HFs). The HF is a complex biological system involved in a dynamic process governed by gene regulation, and gene expression is regulated by microRNAs (miRNAs). miRNA inhibits posttranscriptional gene expression by specifically binding to target messenger RNA (mRNA) and plays an important role in regulating gene expression, the cell cycle and biological development sequences. The purpose of this study was to examine mRNA and miRNA binding to identify key miRNAs and target genes related to HF development. This will provide new and important insights into fundamental mechanisms that regulate cellular activity and cell fate decisions within and outside of the skin.

RESULTS

We analyzed miRNA data in skin tissues collected from 18 Merino sheep on four embryonic days (E65, E85, E105 and E135) and two postnatal days (D7 and D30) and identified 87 differentially expressed miRNAs (DE-miRNAs). These six stages were further divided into two longer developmental stages based on heatmap cluster analysis, and the results showed that DE-mRNAs in Stage A were closely related to HF morphogenesis. A coanalysis of Stage A DE-mRNAs and DE-miRNAs revealed that 9 DE-miRNAs and 17 DE-mRNAs presented targeting relationships in Stage A. We found that miR-23b and miR-133 could target and regulate ACVR1B and WNT10A. In dermal fibroblasts, the overexpression of miR-133 significantly reduced the mRNA and protein expression levels of ACVR1B. The overexpression of miR-23b significantly reduced the mRNA and protein expression levels of WNT10A.

CONCLUSION

This study provides a new reference for understanding the molecular basis of HF development and lays a foundation for further improving sheep HF breeding. miRNAs and target genes related to hair follicular development were found, which provided a theoretical basis for molecular breeding for the culture of fine-wool sheep.

Methionine can subside hair follicle development prejudice of heat-stressed rex rabbits

In the present experiment, we study the function of methionine on hair follicle development in heat-stressed Rex Rabbits and its potential molecular mechanism. Rex rabbits were randomly divided into 5 groups (30 replicates per group): control group (20-25°C, fed basic diet), heat stress group (30-34°C, fed basic diet), heat stress + methionine group (30-34°C, fed 0.15% methionine in addition to the basic diet). fed basic diet (control), heat stress + methionine group (30-34°C, fed 0.3% methionine in addition to the basic diet), heat stress + methionine group (30-34°C, fed 0.45% methionine in addition to the basic diet). The results show that heat stress decreases the hair follicle density of Rex rabbits, and the diet methionine addition significantly increases the hair follicle density of heat-stressed Rabbits (p < .05). Heat stress increased serum HSP70 concentration and skin HSP70 gene expression, 0.15%-0.3% methionine but not 0.45% addition alleviated the effect of heat stress. Dietary 0.15% methionine addition significantly increases the gene expression of Wnt10b, β-catenin, LEF, FZD4, LRP6, Shh, HGF, EGF, and Noggin in heat-stressed Rex rabbits and observably decreases the gene expression of BMP2/4 and TGFb. There was no significant effect of methionine on the expression of IGF1 and FGF5/7 gene expression. In conclusion, methionine maybe promotes hair follicle development via TGFβ-BMP/Shh-Noggin, Wnt10b/β-catenin, EGF, and HGF signaling pathways in heat-stressed rabbits.

Hedgehog signaling reprograms hair follicle niche fibroblasts to a hyper-activated state

Hair follicle stem cells are regulated by dermal papilla fibroblasts, their principal signaling niche. Overactivation of Hedgehog signaling in the niche dramatically accelerates hair growth and induces follicle multiplication in mice. On single-cell RNA sequencing, dermal papilla fibroblasts increase heterogeneity to include new Wnt5a^high states. Transcriptionally, mutant fibroblasts activate regulatory networks for Gli1, Alx3, Ebf1, Hoxc8, Sox18, and Zfp239. These networks jointly upregulate secreted factors for multiple hair morphogenesis and hair-growth-related pathways. Among these is non-conventional TGF-β ligand Scube3. We show that in normal mouse skin, Scube3 is expressed only in dermal papillae of growing, but not in resting follicles. SCUBE3 protein microinjection is sufficient to induce new hair growth, and pharmacological TGF-β inhibition rescues mutant hair hyper-activation phenotype. Moreover, dermal-papilla-enriched expression of SCUBE3 and its growth-activating effect are partially conserved in human scalp hair follicles. Thus, Hedgehog regulates mesenchymal niche function in the hair follicle via SCUBE3/TGF-β mechanism.

Building and Maintaining the Skin

The skin forms a crucial, dynamic barrier between an animal and the external world. In mammals, three stem cell populations possess robust regenerative potential to maintain and repair the body's protective surface: epidermal stem cells, which maintain the stratified epidermis; hair follicle stem cells, which power the cyclic growth of the hair follicle; and melanocyte stem cells, which regenerate pigment-producing melanocytes to color the skin and hair. These stem cells reside in complex microenvironments ("niches") comprising diverse cellular repertoires that enable stem cells to rejuvenate tissues during homeostasis and regenerate them upon injury. Beyond their niches, skin stem cells can also sense and respond to fluctuations in organismal health or changes outside the body. Here, we review these diverse cellular interactions and highlight how far-reaching signals can be transmitted at the local level to enable skin stem cells to tailor their actions to suit the particular occasion and optimize fitness.

Morphogenesis, Growth Cycle and Molecular Regulation of Hair Follicles

As one of the main appendages of skin, hair follicles play an important role in the process of skin regeneration. Hair follicle is a tiny organ formed by the interaction between epidermis and dermis, which has complex and fine structure and periodic growth characteristics. The hair growth cycle is divided into three continuous stages, growth (anagen), apoptosis-driven regression (catagen) and relative quiescence (telogen). And The Morphogenesis and cycle of hair follicles are regulated by a variety of signal pathways. When the signal molecules in the pathways are abnormal, it will affect the development and cycle of hair follicles, which will lead to hair follicle-related diseases.This article will review the structure, development, cycle and molecular regulation of hair follicles, in order to provide new ideas for solving diseases and forming functional hair follicle.

Decomposing a deterministic path to mesenchymal niche formation by two intersecting morphogen gradients

Organ formation requires integrating signals to coordinate proliferation, specify cell fates, and shape tissue. Tracing these events and signals remains a challenge, as intermediate states across many critical transitions are unresolvable over real time and space. Here, we designed a unique computational approach to decompose a non-linear differentiation process into key components to resolve the signals and cell behaviors that drive a rapid transition, using the hair follicle dermal condensate as a model. Combining scRNA sequencing with genetic perturbation, we reveal that proliferative Dkk1+ progenitors transiently amplify to become quiescent dermal condensate cells by the mere spatiotemporal patterning of Wnt/β-catenin and SHH signaling gradients. Together, they deterministically coordinate a rapid transition from proliferation to quiescence, cell fate specification, and morphogenesis. Moreover, genetically repatterning these gradients reproduces these events autonomously in "slow motion" across more intermediates that resolve the process. This analysis unravels two morphogen gradients that intersect to coordinate events of organogenesis.

Ciliary signaling in stem cells in health and disease: Hedgehog pathway and beyond

The primary cilium is a hair-like sensory compartment that protrudes from the cellular surface. The primary cilium is enriched in a variety of signaling molecules that regulate cellular activities. Stem cells have primary cilia. They reside in a specialized environment, called the stem cell niche. This niche contains a variety of secreted factors, and some of their receptors are localized in the primary cilia of stem cells. Here, we summarize the current understanding of the function of cilia in compartmentalized signaling in stem cells. We describe how ciliary signaling regulates stem cells and progenitor cells during development, tissue homeostasis and tumorigenesis. We summarize our understanding of cilia regulated signaling -primary involving the hedgehog pathway- in stem cells in diverse settings that include neuroepithelial cells, radial glia, cerebellar granule neuron precursors, hematopoietic stem cells, hair follicle stem cells, bone marrow mesenchymal stem cells and mammary gland stem cells. Overall, our review highlights a variety of roles that ciliary signaling plays in regulating stem cells throughout life.

Time-course RNA-seq analysis reveals stage-specific and melatonin-triggered gene expression patterns during the hair follicle growth cycle in Capra hircus

Background

Cashmere goat is famous for its high-quality fibers. The growth of cashmere in secondary hair follicles exhibits a seasonal pattern arising from circannual changes in the natural photoperiod. Although several studies have compared and analyzed the differences in gene expression between different hair follicle growth stages, the selection of samples in these studies relies on research experience or morphological evidence. Distinguishing hair follicle growth cycle according to gene expression patterns may help to explore the regulation mechanisms related to cashmere growth and the effect of melatonin from a molecular level more accurately.

Results

In this study, we applied RNA-sequencing to the hair follicles of three normal and three melatonin-treated Inner Mongolian cashmere goats sampled every month during a whole hair follicle growth cycle. A total of 3559 and 988 genes were subjected as seasonal changing genes (SCGs) in the control and treated groups, respectively. The SCGs in the normal group were divided into three clusters, and their specific expression patterns help to group the hair follicle growth cycle into anagen, catagen and telogen stages. Some canonical pathways such as Wnt, TGF-beta and Hippo signaling pathways were detected as promoting the hair follicle growth, while Cell adhesion molecules (CAMs), Cytokine-cytokine receptor interaction, Jak-STAT, Fc epsilon RI, NOD-like receptor, Rap1, PI3K-Akt, cAMP, NF-kappa B and many immune-related pathways were detected in the catagen and telogen stages. The PI3K-Akt signaling, ECM-receptor interaction and Focal adhesion were found in the transition stage between telogen to anagen, which may serve as candidate biomarkers for telogen-anagen regeneration. A total of 16 signaling pathways, 145 pathway mRNAs, and 93 lncRNAs were enrolled to construct the pathway-mRNA-lncRNA network, which indicated the function of lncRNAs through interacting with their co-expressed mRNAs. Pairwise comparisons between the control and melatonin-treated groups also indicated 941 monthly differentially expressed genes (monthly DEGs). These monthly DEGs were mainly distributed from April and September, which revealed a potential signal pathway map regulating the anagen stage triggered by melatonin. Enrichment analysis showed that Wnt, Hedgehog, ECM, Chemokines and NF-kappa B signaling pathways may be involved in the regulation of non-quiescence and secondary shedding under the influence of melatonin.

Conclusions

Our study decoded the key regulators of the whole hair follicle growth cycle, laying the foundation for the control of hair follicle growth and improvement of cashmere yield.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08331-z.

The global regulatory logic of organ regeneration: circuitry lessons from skin and its appendages

In organ regeneration, the regulatory logic at a systems level remains largely unclear. For example, what defines the quantitative threshold to initiate regeneration, and when does the regeneration process come to an end? What leads to the qualitatively different responses of regeneration, which restore the original structure, or to repair which only heals a wound? Here we discuss three examples in skin regeneration: epidermal recovery after radiation damage, hair follicle fate choice after chemotherapy damage, and wound-induced feather regeneration. We propose that the molecular regulatory circuitry is of paramount significance in organ regeneration. It is conceivable that defects in these controlling pathways may lead to failed regeneration and/or organ renewal, and understanding the underlying logic could help to identify novel therapeutic strategies.

The Roles of Non-coding RNA in the Development and Regeneration of Hair Follicles: Current Status and Further Perspectives

Alopecia is a common problem that affects almost every age group and is considered to be an issue for cosmetic or psychiatric reasons. The loss of hair follicles (HFs) and hair caused by alopecia impairs self-esteem, thermoregulation, tactile sensation and protection from ultraviolet light. One strategy to solve this problem is HF regeneration. Many signalling pathways and molecules participate in the morphology and regeneration of HF, such as Wnt/β-catenin, Sonic hedgehog, bone morphogenetic protein and Notch. Non-coding RNAs (ncRNAs), especially microRNAs and long ncRNAs, have significant modulatory roles in HF development and regeneration via regulation of these signalling pathways. This review provides a comprehensive overview of the status and future prospects of ncRNAs in HF regeneration and could prompt novel ncRNA-based therapeutic strategies.

Basal epidermis collective migration and local Sonic hedgehog signaling promote skeletal branching morphogenesis in zebrafish fins

Teleost fish fins, like all vertebrate limbs, comprise a series of bones laid out in characteristic pattern. Each fin's distal bony rays typically branch to elaborate skeletal networks providing form and function. Zebrafish caudal fin regeneration studies suggest basal epidermal-expressed Sonic hedgehog (Shh) promotes ray branching by partitioning pools of adjacent pre-osteoblasts. This Shh role is distinct from its well-studied Zone of Polarizing Activity role establishing paired limb positional information. Therefore, we investigated if and how Shh signaling similarly functions during developmental ray branching of both paired and unpaired fins while resolving cellular dynamics of branching by live imaging. We found shha is expressed uniquely by basal epidermal cells overlying pre-osteoblast pools at the distal aspect of outgrowing juvenile fins. Lateral splitting of each shha-expressing epidermal domain followed by the pre-osteoblast pools precedes overt ray branching. We use ptch2:Kaede fish and Kaede photoconversion to identify short stretches of shha+basal epidermis and juxtaposed pre-osteoblasts as the Shh/Smoothened (Smo) active zone. Basal epidermal distal collective movements continuously replenish each shha+domain with individual cells transiently expressing and responding to Shh. In contrast, pre-osteoblasts maintain Shh/Smo activity until differentiating. The Smo inhibitor BMS-833923 prevents branching in all fins, paired and unpaired, with surprisingly minimal effects on caudal fin initial skeletal patterning, ray outgrowth or bone differentiation. Staggered BMS-833923 addition indicates Shh/Smo signaling acts throughout the branching process. We use live cell tracking to find Shh/Smo restrains the distal movement of basal epidermal cells by apparent 'tethering' to pre-osteoblasts. We propose short-range Shh/Smo signaling promotes these heterotypic associations to couple instructive basal epidermal collective movements to pre-osteoblast repositioning as a unique mode of branching morphogenesis.

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.

The anti-apoptotic Bcl-2 protein regulates hair follicle stem cell function

Maintaining the architecture, size and composition of an intact stem cell (SC) compartment is crucial for tissue homeostasis and regeneration throughout life. In mammalian skin, elevated expression of the anti‐apoptotic Bcl‐2 protein has been reported in hair follicle (HF) bulge SCs (BSCs), but its impact on SC function is unknown. Here, we show that systemic exposure of mice to the Bcl‐2 antagonist ABT‐199/venetoclax leads to the selective loss of suprabasal BSCs (sbBSCs), thereby disrupting cyclic HF regeneration. RNAseq analysis shows that the pro‐apoptotic BH3‐only proteins BIM and Bmf are upregulated in sbBSCs, explaining their addiction to Bcl‐2 and the marked susceptibility to Bcl‐2 antagonism. In line with these observations, conditional knockout of Bcl‐2 in mouse epidermis elevates apoptosis in BSCs. In contrast, ectopic Bcl‐2 expression blocks apoptosis during HF regression, resulting in the accumulation of quiescent SCs and delaying HF growth in mice. Strikingly, Bcl‐2‐induced changes in size and composition of the HF bulge accelerate tumour formation. Our study identifies a niche‐instructive mechanism of Bcl‐2‐regulated apoptosis response that is required for SC homeostasis and tissue regeneration, and may suppress carcinogenesis.

A PDZ Protein GIPC3 Positively Modulates Hedgehog Signaling and Melanoma Growth

The Hedgehog (Hh) pathway is essential for animal development but aberrant activation promotes cancer growth. Here we show that GIPC3, a PDZ domain-containing protein with putative adaptor protein function, positively modulates Hh target gene expression in normal fibroblasts and melanoma cells and supports melanoma tumor growth. Using overexpression and epistasis studies, we show that Gipc3 potentiates Hh transcriptional output and it modulates GLI-dependent transcription independently of Sufu. While we find GIPC3 protein does not interact with Hh pathway components, Ingenuity Pathway Analyses of GIPC3-interacting proteins identified by co-immunoprecipitation and mass spectrometry show an association with cancer pathogenesis. Subsequent interrogation of TCGA and The Human Protein Atlas databases reveals GIPC3 upregulation in many cancers. Using expression screens in selected groups of GIPC3-upregulated cancers with reported Hh pathway activation, we find a significant positive correlation of GIPC3 expression with Hh pathway components GLI1, GLI2, and GPR161, in melanoma lines. Consistently, GIPC3 knockdown in melanoma lines significantly reduces GLI1 and GLI2 expression, cell viability, colony formation, and allograft tumor growth. Our findings highlight previously unidentified roles of Gipc3 in potentiating Hh response and melanoma tumorigenesis, and suggest that GIPC3 modulation on Hh signaling may be targeted to reduce melanoma growth.

Identification of Key Pathways and Genes Related to the Development of Hair Follicle Cycle in Cashmere Goats

The development of hair follicle in cashmere goats shows significant periodic change, as with mice and humans. However, for cashmere goat with double-coat, the periodic change may be due to other regulatory molecules and signal pathways. To understand the mechanism of periodic development of hair follicle, we performed a weighted gene coexpression network analysis (WGCNA) to mine key genes and establish an interaction network by utilizing the NCBI public dataset. Ten coexpression modules, including 7689 protein-coding genes, were constructed by WGCNA, six of which are considered to be significantly related to the development of the hair follicle cycle. A functional enrichment analysis for each model showed that they are closely related to ECM- receptor interaction, focal adhesion, PI3K-Akt signaling pathway, estrogen signaling pathway, and so on. Combined with the analysis of differential expressed genes, 12 hub genes from coexpression modules were selected as candidate markers, i.e., COL1A1, C1QTNF6, COL1A2, AQP3, KRTAP3-1, KRTAP11-1, FA2H, NDUFS5, DERL2, MRPL14, ANTKMT and XAB2, which might be applied to improve cashmere production.

Development and Maintenance of Epidermal Stem Cells in Skin Adnexa

The skin surface is modified by numerous appendages. These structures arise from epithelial stem cells (SCs) through the induction of epidermal placodes as a result of local signalling interplay with mesenchymal cells based on the Wnt–(Dkk4)–Eda–Shh cascade. Slight modifications of the cascade, with the participation of antagonistic signalling, decide whether multipotent epidermal SCs develop in interfollicular epidermis, scales, hair/feather follicles, nails or skin glands. This review describes the roles of epidermal SCs in the development of skin adnexa and interfollicular epidermis, as well as their maintenance. Each skin structure arises from distinct pools of epidermal SCs that are harboured in specific but different niches that control SC behaviour. Such relationships explain differences in marker and gene expression patterns between particular SC subsets. The activity of well-compartmentalized epidermal SCs is orchestrated with that of other skin cells not only along the hair cycle but also in the course of skin regeneration following injury. This review highlights several membrane markers, cytoplasmic proteins and transcription factors associated with epidermal SCs.

Overexpression of Fgf8 in the epidermis inhibits hair follicle development

The hair follicle is a classical model for studying epithelial-mesenchymal interactions. Given the critical role of fibroblast growth factor 8 (Fgf8) in embryonic development, we generated a mouse model that overexpresses Fgf8 specifically in the epidermis. Interestingly, these mutant mice exhibited stunted, smaller bodies and severe hypotrichosis. Histological analysis showed that the hair follicles in the mutants were arrested at stage 2 of hair development. The density of hair follicles in the mutant mice was also lower compared to that in the control mice. Overexpression of Fgf8 inhibited the proliferation of epidermal cells and simultaneously promoted apoptosis, leading to the arrest of hair follicle development. Further analysis showed that sonic hedgehog (Shh) and bone morphogenetic protein 4 (Bmp4) were downregulated and upregulated, respectively. To summarize, our study demonstrates that FGF signalling plays an important role in the regulation of hair follicle development.

Maintaining Hair Inductivity in Human Dermal Papilla Cells: A Review of Effective Methods

The dermal papilla comprises mesenchymal cells in hair follicles, which play the main role in regulating hair growth. Maintaining the potential hair inductivity of dermal papilla cells (DPCs) and dermal sheath cells during cell culture is the main factor in in vitro morphogenesis and regeneration of hair follicles. Using common methods for the cultivation of human dermal papilla reduces the maintenance requirements of the inductive capacity of the dermal papilla and the expression of specific dermal papilla biomarkers. Optimizing culture conditions is therefore crucial for DPCs. Moreover, exosomes appear to play a key role in regulating the hair follicle growth through a paracrine mechanism and provide a functional method for treating hair loss. The present review investigated the biology of DPCs, the molecular and cell signaling mechanisms contributing to hair follicle growth in humans, the properties of the dermal papilla, and the effective techniques in maintaining hair inductivity in DPC cultures in humans as well as hair follicle bioengineering.

VGLL4 promotes osteoblast differentiation by antagonizing TEADs-inhibited Runx2 transcription

VGLL4 has been identified as a YAP inhibitor. However, the exact function of VGLL4 in bone development and bone homeostasis remains unclear. In this study, we demonstrated that VGLL4 breaks TEADs-mediated transcriptional inhibition of RUNX2 to promote osteoblast differentiation and bone development. We found that knockout of VGLL4 in mesenchymal stem cells and preosteoblasts showed osteoporosis and a cleidocranial dysplasia-like phenotype due to osteoblast differentiation disorders. Mechanistically, we showed that the TEAD transcriptional factors severely inhibited osteoblast differentiation in a YAP binding-independent manner. TEADs interacted with RUNX2 to repress RUNX2 transcriptional activity. Furthermore, VGLL4 relieved the transcriptional inhibition of TEADs by directly competing with RUNX2 to bind TEADs through its two TDU domains. Collectively, our studies demonstrate that VGLL4 plays an important role in regulating osteoblast differentiation and bone development, and that TEADs regulate the transcriptional activity of RUNX2, which may shed light on treatment of cleidocranial dysplasia and osteoporosis.

Tissue Stem Cells: Architects of Their Niches

Stem cells (SCs) maintain tissue homeostasis and repair wounds. Despite marked variation in tissue architecture and regenerative demands, SCs often follow similar paradigms in communicating with their microenvironmental "niche" to transition between quiescent and regenerative states. Here we use skin epithelium and skeletal muscle-among the most highly-stressed tissues in our body-to highlight similarities and differences in niche constituents and how SCs mediate natural tissue rejuvenation and perform regenerative acts prompted by injuries. We discuss how these communication networks break down during aging and how understanding tissue SCs has led to major advances in regenerative medicine.

An updated classification of hair follicle morphogenesis

Hair follicle (HF) formation in developing embryonic skin requires stepwise signalling between the epithelial epidermis and mesenchymal dermis, and their specialized derivatives, the placode/germ/peg and dermal condensate/papilla, respectively. Classically, distinct stages of HF morphogenesis have been defined, in the mouse model, based on (a) changes in cell morphology and aggregation; (b) expression of few known molecular markers; (c) the extent of follicle downgrowth; and (d) the presence of differentiating cell types. Refined genetic strategies and recent emerging technologies, such as live imaging and transcriptome analyses of isolated cell populations or single cells, have enabled a closer dissection of the signalling requirements at different stages of HF formation, particularly early on. They have also led to the discovery of precursor cells for placode, dermal condensate and future bulge stem cells that, combined with molecular insights into their fate specification and subsequent formation, serve as novel landmarks for early HF morphogenetic events and studies of the signalling networks mediating these processes. In this review, we integrate the emergence of HF precursor cell states and novel molecular markers of fate and formation to update the widely used 20-year-old seminal classification guide of HF morphogenetic stages by Paus et al. We then temporally describe the latest insights into the early cellular and molecular events and signalling requirements for HF morphogenesis in relation to one another in a holistic manner.

m6A RNA methylation impacts fate choices during skin morphogenesis

N6-methyladenosine is the most prominent RNA modification in mammals. Here, we study mouse skin embryogenesis to tackle m6A's functions and physiological importance. We first landscape the m6A modifications on skin epithelial progenitor mRNAs. Contrasting with in vivo ribosomal profiling, we unearth a correlation between m6A modification in coding sequences and enhanced translation, particularly of key morphogenetic signaling pathways. Tapping physiological relevance, we show that m6A loss profoundly alters these cues and perturbs cellular fate choices and tissue architecture in all skin lineages. By single-cell transcriptomics and bioinformatics, both signaling and canonical translation pathways show significant downregulation after m6A loss. Interestingly, however, many highly m6A-modified mRNAs are markedly upregulated upon m6A loss, and they encode RNA-methylation, RNA-processing and RNA-metabolism factors. Together, our findings suggest that m6A functions to enhance translation of key morphogenetic regulators, while also destabilizing sentinel mRNAs that are primed to activate rescue pathways when m6A levels drop.

Expression profile analysis to identify circular RNA expression signatures in hair follicle of Hu sheep lambskin

CircRNAs are involved in the regulation of various cellular and biological processes, but none of the studies have focused on hair follicle in sheep. In this study, the expression profile of circRNAs between small waves (SM) and straight wool (ST) groups was investigated using RNA-Seq. The results showed that a total of 5,527 circRNAs were identified and 114 of them were differentially expressed between two groups. Enrichment analysis revealed that the host genes with DE circRNAs were mainly enriched in TGF-beta pathway, Notch pathway. Miranda software was used to found that 129 miRNAs might be binding to 114 DE circRNAs, including miR-10a, miR-143, miR-let-7a, miR-199a-3p, miR-200a, which also had important influence on hair follicle morphogenesis. Furthermore, the coding potential of circRNAs was predicted, and 11 circRNAs were simultaneously identified with coding potential. In summary, circRNAs have important effects on hair follicle growth and development, and these results will provide a basis for molecular mechanism of pattern formation.

Cell Types Promoting Goosebumps Form a Niche to Regulate Hair Follicle Stem Cells

Piloerection (goosebumps) requires concerted actions of the hair follicle, the arrector pili muscle (APM), and the sympathetic nerve, providing a model to study interactions across epithelium, mesenchyme, and nerves. Here, we show that APMs and sympathetic nerves form a dual-component niche to modulate hair follicle stem cell (HFSC) activity. Sympathetic nerves form synapse-like structures with HFSCs and regulate HFSCs through norepinephrine, whereas APMs maintain sympathetic innervation to HFSCs. Without norepinephrine signaling, HFSCs enter deep quiescence by down-regulating the cell cycle and metabolism while up-regulating quiescence regulators Foxp1 and Fgf18. During development, HFSC progeny secretes Sonic Hedgehog (SHH) to direct the formation of this APM-sympathetic nerve niche, which in turn controls hair follicle regeneration in adults. Our results reveal a reciprocal interdependence between a regenerative tissue and its niche at different stages and demonstrate sympathetic nerves can modulate stem cells through synapse-like connections and neurotransmitters to couple tissue production with demands.

Ectopic expression of SOX18 in Basal cell carcinoma negatively regulates tumour progression

BACKGROUND

Basal Cell Carcinoma is the most common tumour and yet much remains to be determined regarding the molecular mechanisms that leads to its development. Hedgehog signal activation is sufficient for BCC induction, but the molecular mediators of BCC growth are not well understood. SoxF transcription factor Sox18 has been identified in human BCC, but its role in growth of the tumour is as yet unknown.

OBJECTIVE

To determine if Sox18 is involved in the regulation of Basal Cell Carcinoma growth.

METHODS

We analysed the function of Sox18 by combining a dominant negative Sox18 mouse model, Sox18^+/OP with murine BCC RESULTS: We determine that Sox18 is ectopically expressed in the epidermal cells of a murine model of Basal Cell Carcinoma. We then show that dominant negative mutation of Sox18 increases the severity of murine Basal Cell Carcinoma. Finally, decreased Hey1 in Sox18^+/OP BCC suggests Sox18 may negatively regulate BCC progression via Notch signaling.

CONCLUSIONS

These data suggest that Sox18 is a hedgehog regulated mediator of tumour suppression within Basal Cell Carcinoma epidermis.

LncRNA-XIST promotes dermal papilla induced hair follicle regeneration by targeting miR-424 to activate hedgehog signaling

BACKGROUND

Alopecia is a highly prevalent disease characterizing by the loss of hair. Dermal papilla (DP) cells are the inducer of hair follicle regeneration, and in vitro three-dimensional (3D) culturing DP cells have been proven to induce hair follicle regeneration. However, the molecular mechanisms behind the regulation of 3D culturing DP cells remain unclear.

METHODS

3D-cultivated DP cells were used as in vitro cell model. DP sphere xenograft to nude mice was performed for in vivo study of hair follicle regeneration. qRT-PCR, Western blotting, and immunofluorescence were used for detecting the level of XIST, miR-424 and Hedgehog pathway-related proteins, respectively. H&E staining was used to examine hair neogenesis. Cell viability, proliferation and ALP activity were measured by MTT, CCK-8 and ELISA assays, respectively. Luciferase assays were used for studying molecular regulation between XIST, miR-424 and Shh 3'UTR.

RESULTS

XIST and Shh were up-regulated, and miR-424 was down-regulated in 3D DP cells. Molecular regulation studies suggested that XIST sponged miR-424 to promote Shh expression. Knockdown of XIST suppressed DP cell activity, cell proliferation, ALP activity and the expression of other DP markers by sponging miR-424. Knockdown of XIST suppressed Shh mediated hedgehog signaling by targeting miR-424. Moreover, the knockdown of XIST inhibited DP sphere induced in vivo hair follicle regeneration and hair development.

CONCLUSION

XIST sponges miR-424 to promote Shh expression, thereby activating hedgehog signaling and facilitating DP mediated hair follicle regeneration.