Molecular control of epithelial-mesenchymal interactions during hair follicle cycling

Small molecule agents against alopecia: Potential targets and related pathways

Alopecia has emerged as a global concern, extending beyond the middle-aged and elderly population and increasingly affecting younger individuals. Despite its growing prevalence, the treatment options and effective drugs for alopecia remain limited due to the incomplete understanding of its underlying mechanisms. Therefore, it is urgent to explore the pathogenesis of alopecia and discover novel and safer therapeutic agents. This review provided an overview of the prevailing clinical disorders of alopecia, and the key pathways and targets involved in hair growth process. Additionally, it discusses FDA-approved drugs and clinical candidates for the treatment of alopecia, and explores small molecule compounds with anti-alopecia potential in the drug discovery phase. These endeavors are expected to provide researchers with valuable scientific insights and practical information for anti-alopecia drug discovery.

Improvement of androgenic alopecia by extracellular vesicles secreted from hyaluronic acid-stimulated induced mesenchymal stem cells

BACKGROUND

Androgenetic alopecia (AGA) is a common form of hair loss. Androgens, such as testosterone and dihydrotestosterone, are the main causes of AGA. Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) can reduce AGA. However, preparing therapeutic doses of MSCs for clinical use is challenging. Induced pluripotent stem cell-derived MSCs (iMSCs) are homogenous and easily expandable, enabling scalable production of EVs. Hyaluronic acid (HA) can exert various functions including free radical scavenging, immune regulation, and cell migration. Herein, we examined whether hyaluronic acid (HA) stimulation of iMSCs could produce EVs with enhanced therapeutic outcomes for AGA.

METHODS

EVs were collected from iMSCs primed with HA (HA-iMSC-EVs) or without HA (iMSC-EVs). The characteristics of EVs were examined using dynamic light scattering, cryo-transmission electron microscopy, immunoblotting, flow cytometry, and proteomic analysis. In vitro, we compared the potential of EVs in stimulating the survival of hair follicle dermal papilla cells undergoing testosterone-mediated AGA. Additionally, the expression of androgen receptor (AR) and relevant growth factors as well as key proteins of Wnt/β-catenin signaling pathway (β-catenin and phosphorylated GSK3β) was analyzed. Subsequently, AGA was induced in male C57/BL6 mice by testosterone administration, followed by repeated injections of iMSC-EVs, HA-iMSC-EVs, finasteride, or vehicle. Several parameters including hair growth, anagen phase ratio, reactivation of Wnt/β-catenin pathway, and AR expression was examined using qPCR, immunoblotting, and immunofluorescence analysis.

RESULTS

Both types of EVs showed typical characteristics for EVs, such as size distribution, markers, and surface protein expression. In hair follicle dermal papilla cells, the mRNA levels of AR, TGF-β, and IL-6 increased by testosterone was blocked by HA-iMSC-EVs, which also contributed to the augmented expression of trophic genes related to hair regrowth. However, no notable changes were observed in the iMSC-EVs. Re-activation of Wnt/β-catenin was observed in HA-iMSC-EVs but not in iMSC-EVs, as shown by β-catenin stabilization and an increase in phosphorylated GSK3β. Restoration of hair growth was more significant in HA-iMSC-EVs than in iMSC-EVs, and was comparable to that in mice treated with finasteride. Consistently, the decreased anagen ratio induced by testosterone was reversed by HA-iMSC-EVs, but not by iMSC-EVs. An increased expression of hair follicular β-catenin protein, as well as the reduction of AR was observed in the skin tissue of AGA mice receiving HA-iMSC-EVs, but not in those treated with iMSC-EVs.

CONCLUSIONS

Our results suggest that HA-iMSC-EVs have potential to improve AGA by regulating growth factors/cytokines and stimulating AR-related Wnt/β-catenin signaling.

Deep Hair Phenomics: Implications in Endocrinology, Development, and Aging

Hair quality is an important indicator of health in humans and other animals. Current approaches to assess hair quality are generally non-quantitative or are low throughput due to technical limitations of 'splitting hairs'. We developed a deep learning-based computer vision approach for the high throughput quantification of individual hair fibers at a high resolution. Our innovative computer vision tool can distinguish and extract overlapping fibers for quantification of multivariate features including length, width, and color to generate single-hair phenomes (shPhenome) of diverse conditions across the lifespan of mice. Using our tool, we explored the effects of hormone signaling, genetic modifications, and aging on hair follicle output. Our analyses revealed hair phenotypes resultant of endocrinological, developmental, and aging-related alterations in the fur coats of mice. These results demonstrate the efficacy of our deep hair phenomics tool for characterizing factors that modulate the hair follicle and developing new diagnostic methods for detecting disease through the hair fiber. Finally, we have generated a searchable, interactive web tool for the exploration of our hair fiber data at skinregeneration.org.

Chitinase 3-Like 1 and C-X-C motif chemokine ligand 5 proteins and the hair cycle

Dermal papilla cells (DPCs) exhibit self-recovery ability, which may be involved in hair growth. Therefore, we tested whether DPCs subjected to temporary growth-inhibiting stress (testosterone, 17β-estradiol, mitomycin C, or undernutrition) treatments exhibit self-recovery behavior that can activate hair follicle growth, and examined the changes in cell proliferation capacity and gene expression. Related proteins were identified and their relationships with the hair cycle was examined using a mouse model. Recovery-period DPCs (i.e., from day 3 after loading) were subjected to microarray analysis to detect genetic variations common to each stress treatment. Co-culture of recovery-period DPCs and outer root sheath cells (ORSCs) confirmed the promotion of ORSC proliferation, suggesting that the activation of hair follicle growth is promoted via signal transduction. Chitinase 3-like 1 (CHI3L1) and C-X-C motif chemokine 5 (CXCL5) exhibited ORSC proliferation-promoting effects. Measurement of protein content in the skin during each phase of the hair cycle in mice revealed that CHI3L1 and CXCL5 secretion increased immediately after anagen transition. In a hair-loss mouse model treated with testosterone or 17β-estradiol, CHI3L1 and CXCL5 secretion was lower in treated telogen skin than in untreated skin. Our results suggest that CHI3L1 and CXCL5 secreted by recovery-state DPCs promote hair growth.

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.

Melatonin promotes hair regeneration by modulating the Wnt/β-catenin signalling pathway

Melatonin (MLT) is a circadian hormone that reportedly influences the development and cyclic growth of secondary hair follicles; however, the mechanism of regulation remains unknown. Here, we systematically investigated the role of MLT in hair regeneration using a hair depilation mouse model. We found that MLT supplementation significantly promoted hair regeneration in the hair depilation mouse model, whereas supplementation of MLT receptor antagonist luzindole significantly suppressed hair regeneration. By analysing gene expression dynamics between the MLT group and luzindole-treated groups, we revealed that MLT supplementation significantly up-regulated Wnt/β-catenin signalling pathway-related genes. In-depth analysis of the expression of key molecules in the Wnt/β-catenin signalling pathway revealed that MLT up-regulated the Wnt/β-catenin signalling pathway in dermal papillae (DP), whereas these effects were facilitated through mediating Wnt ligand expression levels in the hair follicle stem cells (HFSCs). Using a DP-HFSCs co-culture system, we verified that MLT activated Wnt/β-catenin signalling in DPs when co-cultured with HFSCs, whereas supplementation of DP cells with MLT alone failed to activate Wnt/β-catenin signalling. In summary, our work identified a critical role for MLT in promoting hair regeneration and will have potential implications for future hair loss treatment in humans.

The development of anin vitrohuman hair follicle organoid with a complexity similar to thatin vivo

In vitrohair follicle (HF) models are currently limited toex vivoHF organ cultures (HFOCs) or 2D models that are of low availability and do not reproduce the architecture or behavior of the hair, leading to poor screening systems. To resolve this issue, we developed a technology for the construction of a humanin vitrohair construct based on the assemblage of different types of cells present in the hair organ. First, we demonstrated that epithelial cells, when isolatedin vitro, have similar genetic signatures regardless of their dissection site, and their trichogenic potential is dependent on the culture conditions. Then, using cell aggregation techniques, 3D spheres of dermal papilla (DP) were constructed, and subsequently, epithelial cells were added, enabling the production and organization of keratins in hair, similar to what is seenin vivo. These reconstructed tissues resulted in the following hair compartments: K71 (inner root-sheath), K85 (matrix region), K75 (companion layer), and vimentin (DP). Furthermore, the new hair model was able to elongate similarly toex vivoHFOC, resulting in a shaft-like shape several hundred micrometers in length. As expected, when the model was exposed to hair growth enhancers, such as ginseng extract, or inhibitors, such as TGF-B-1, significant effects similar to thosein vivowere observed. Moreover, when transplanted into skin biopsies, the new constructs showed signs of integration and hair bud generation. Owing to its simplicity and scalability, this model fully enables high throughput screening of molecules, which allows understanding of the mechanism by which new actives treat hair loss, finding optimal concentrations, and determining the synergy and antagonism among different raw materials. Therefore, this model could be a starting point for applying regenerative medicine approaches to treat hair loss.

Single-Cell Transcriptome Sequence Profiling on the Morphogenesis of Secondary Hair Follicles in Ordos Fine-Wool Sheep

The Ordos fine-wool sheep is a high-quality breed in China that produces superior natural textiles and raw materials such as wool and lamb meat. However, compared to the Australian Merino sheep, there is still a gap in terms of the wool fiber fineness and wool yield. The hair follicle is the main organ that controls the type of wool fiber, and the morphological changes in the secondary hair follicle are crucial in determining wool quality. However, the process and molecular mechanisms of hair follicle morphogenesis in Ordos fine-wool sheep are not yet clear. Therefore, analyzing the molecular mechanisms underlying the process of follicle formation is of great significance for improving the fiber diameter and wool production of Ordos fine-wool sheep. The differential expressed genes, APOD, POSTN, KRT5, and KRT15, which related to primary hair follicles and secondary hair follicles, were extracted from the dermal papillae. Based on pseudo-time analysis, the differentiation trajectories of dermal lineage cells and epidermal lineage cells in the Ordos fine-wool sheep were successfully constructed, providing a theoretical basis for breeding research in Ordos fine-wool sheep.

Dermal papilla cell-secreted biglycan regulates hair follicle phase transit and regeneration by activating Wnt/β-catenin

Alopecia is a prevalent problem of cutaneous appendages and lacks effective therapy. Recently, researchers have been focusing on mesenchymal components of the hair follicle, i.e. dermal papilla cells, and we previously identified biglycan secreted by dermal papilla cells as the key factor responsible for hair follicle-inducing ability. In this research, we hypothesized biglycan played an important role in hair follicle cycle and regeneration through regulating the Wnt signalling pathway. To characterize the hair follicle cycle and the expression pattern of biglycan, we observed hair follicle morphology in C57BL/6 mice on Days 0, 3, 5, 12 and 18 post-depilation and found that biglycan is highly expressed at both mRNA and protein levels throughout anagen in HFs. To explore the role of biglycan during the phase transit process and regeneration, local injections were administered in C57BL/6 and nude mice. Results showed that local injection of biglycan in anagen HFs delayed catagen progression and involve activating the Wnt/β-catenin signalling pathway. Furthermore, local injection of biglycan induced HF regeneration and up-regulated expression of key Wnt factors in nude mice. In addition, cell analyses exhibited biglycan knockdown inactivated the Wnt signalling pathway in early-passage dermal papilla cell, whereas biglycan overexpression or incubation activated the Wnt signalling pathway in late-passage dermal papilla cells. These results indicate that biglycan plays a critical role in regulating HF cycle transit and regeneration in a paracrine and autocrine fashion by activating the Wnt/β-catenin signalling pathway and could be a potential treatment target for hair loss diseases.

Interpretation of the Yak Skin Single-Cell Transcriptome Landscape

The morphogenesis of hair follicle structure is accompanied by the differentiation of skin tissue. Mammalian coats are produced by hair follicles. The formation of hair follicles requires signal transmission between the epidermis and dermis. However, knowledge of the transcriptional regulatory mechanism is still lacking. We used single-cell RNA sequencing to obtain 26,573 single cells from the scapular skin of yaks at hair follicle telogen and anagen stages. With the help of known reference marker genes, 11 main cell types were identified. In addition, we further analyzed the DP cell and dermal fibroblast lineages, drew a single-cell map of the DP cell and dermal fibroblast lineages, and elaborated the key genes, signals, and functions involved in cell fate decision making. The results of this study provide a very valuable resource for the analysis of the heterogeneity of DP cells and dermal fibroblasts in the skin and provide a powerful theoretical reference for further exploring the diversity of hair follicle cell types and hair follicle morphogenesis.

Establishment and characterization of matched immortalized human frontal and occipital scalp dermal papilla cell lines from androgenetic alopecia

Androgenetic alopecia (AGA), also known as male pattern baldness, is a common hair loss condition influenced by genetic and hormonal factors. Variations in gene expression and androgen responsiveness have been observed between the frontal and occipital regions of AGA patients. However, obtaining and cultivating frontal hair follicles is challenging. Therefore, no matched frontal and occipital dermal papilla (DP) cell lines have been reported yet. This study aimed to establish matched immortalized human frontal and occipital scalp DP cell lines from AGA patients. Simian virus 40 large T antigen (SV40T-Ag) and human telomerase reverse transcriptase (hTERT) were introduced into primary human DP cells. The obtained cell lines were characterized by assessing their gene expression patterns, androgen receptor (AR) levels, and the presence of 5-alpha reductase (5αR). Additionally, we examined their response to dihydrotestosterone (DHT) and evaluated cell viability. The conditioned medium from the frontal DP cell line inhibited human hair follicle growth, leading to reduced keratinocyte proliferation and increased apoptosis. Furthermore, when the cells were cultured in a 3D environment mimicking in vivo conditions, the 3D cultured frontal DP cell line exhibited weaker sphere aggregation than the occipital DP cell line due to the increased expression of matrix metalloproteinase 1 (MMP1), MMP3, and MMP9. Additionally, the expression of DP signature genes was inhibited in the 3D cultured frontal DP cell line. These matched frontal and occipital DP cell lines hold significant potential as valuable resources for research on hair loss. Their establishment allows us to investigate the differences between frontal and occipital DP cells, contributing to a better understanding of the molecular mechanisms underlying AGA. Furthermore, these cell lines may be valuable for developing targeted therapeutic approaches for hair loss conditions.

Establishment and functional characterization of immortalized rabbit dermal papilla cell lines

Hair follicle (HF) undergo periodic growth and development in mammals, which regulated by dermal papilla cells (DPCs) are reported to play an important role in HF morphogenesis and development. However, primary DPCs have low proliferative activity, age quickly, and fresh cell isolation is both time-consuming and laborious. In this study, we introduced the SV40 large T antigen (SV40T) into dissociated early passage rabbit vibrissae DPCs with lentiviral vectors and established seven immortalized DPC lines (R-1, R-2, R-3, R-4, R-5, R-6 and R-7). These cell lines displayed early passage morphology and high alkaline phosphatase activity. RT-PCR and immunofluorescence staining showed that all the immortalized cell lines expressed the DPC markers (α-SMA, IGF1, ALPL, FGF2, BMP2 and TGFβ2), but α-SMA was only expressed well in R-3, R-4, and R-7. Furthermore, it was found that R-7 was the only line to survive beyond 50 passages. Compared to melanoma cells, R-7 did not undergo malignant transformation. Karyotyping and cell growth viability analysis illustrated that the R-7 cell line preserved the basic characteristics of primary DPCs. The R-7 DPCs established have potential application for future hair research. The study provides the theoretical basis in the cell research of HF growth and development.

Activation of mitochondrial aldehyde dehydrogenase 2 promotes hair growth in human hair follicles

INTRODUCTION

Hair loss is a common phenomenon associated with various environmental and genetic factors. Mitochondrial dysfunction-induced oxidative stress has been recognized as a crucial determinant of hair follicle (HF) biology. Aldehyde dehydrogenase 2 (ALDH2) mitigates oxidative stress by detoxifying acetaldehyde. This study investigated the potential role of ALDH2 modulation in HF function and hair growth promotion.

OBJECTIVES

To evaluate the effects of ALDH2 activation on oxidative stress in HFs and hair growth promotion.

METHODS

The modulatory role of ALDH2 on HFs was investigated using an ALDH2 activator. ALDH2 expression in human HFs was evaluated through in vitro immunofluorescence staining. Ex vivo HF organ culture was employed to assess hair shaft elongation, while the fluorescence probe 2',7'- dichlorodihydrofluorescein diacetate was utilized to detect reactive oxygen species (ROS). An in vivo mouse model was used to determine whether ALDH2 activation induces anagen.

RESULTS

During the anagen phase, ALDH2 showed significantly higher intensity than that in the telogen phase, and its expression was primarily localized along the outer layer of HFs. ALDH2 activation promoted anagen phase induction by reducing ROS levels and enhancing reactive aldehyde clearance, which indicated that ALDH2 functions as a ROS scavenger within HFs. Moreover, ALDH2 activation upregulated Akt/GSK 3β/β-catenin signaling in HFs.

CONCLUSIONS

Our findings highlight the hair growth promotion effects of ALDH2 activation in HFs and its potential as a promising therapeutic approach for promoting anagen induction.

Fabrication and evaluation of a bi-layered gelatin based scaffold with arrayed micro-pits for full-thickness skin construct

There is an unmet need for a reliable and reproducible method for incorporating hair follicle derived stem cells in tissue engineered skin models to reconstitute hair follicles. This study discloses a novel method for introducing hair follicle derived stem cells in microneedle embossed micro-pits of a bilayer skin equivalent fabricated from a gelatin based scaffold. The microneedles are hard and strong enough to penetrate the upper layer of the bilayer gelatin based scaffold that corresponds to the epidermis and permeates down to lower layer that corresponds to dermal layer. This strategic location will mimic the natural niche of hair follicle stem cells for picking up signals from both the epidermis and dermis. Hair follicle stem cells are trapped in to these micro-pits by vacuum assisted cell seeding. The bilayer system consists of two distinct electrospun layers in a single processing step, representing outer epidermal layer and inner dermal layer with hair follicle stem cells in embedded pits, resulting in the formation of a closed representation of a complete skin.

Expression of miRNA-1-3p and its target gene in hair follicle cycle development of Liaoning Cashmere goat

MicroRNA exerts an important regulatory role in almost all the biological process, including hair follicle development in Liaoning Cashmere goat. In order to improve the Cashmere performance of goat, the regulatory role of microRNA in hair follicle cycle has drawn hotspot attention. However, the molecular mechanisms of miRNA-1-3p involved in hair follicle development are poorly understood. In this study, we found that miRNA-1-3p was less expressed in anagen stage of hair follicle cycle of Cashmere goat than that in telogen stage by using RT-qPCR and immunoblotting analysis, in contrast to the expression pattern of FGF14. The Dual-Luciferase reporter assay was employed to verify the relationship between miRNA-1-3p and FGF14. The results showed that miRNA-1-3p specifically binds to the 3'UTR of FGF14 mRNA, and FGF14 is the target gene of miR-1-3p. In conclusion, this study shows that miRNA-1-3p may regulate hair follicle development in Liaoning Cashmere goats by targeting FGF14.

Collagen Hydrolysate from the Scales of Mozambique Tilapia (Oreochromis mossambicus) Improve Hair and Skin Health by Alleviating Oxidative Stress and Inflammation and Promoting Hair Growth and Extracellular Matrix Factors

Fish-derived collagen hydrolysate (CH) has shown promise in improving hair and skin health. Therefore, this study sought to comprehensively assess the effects of CH extracted from Mozambique tilapia (Oreochromis mossambicus) scales on hair and skin using in vitro and in vivo models. Human dermal papilla cells (hDPCs) were used for antioxidant and gene expression analyses, while C57BL/6 mice were orally administered CH for six weeks to assess hair growth patterns. The mice were divided into four groups: negative control (NC; distilled water), positive control (PC; 1 mg/kg finasteride), CH500 (500 mg/kg BW CH), and CH1000 (1000 mg/kg BW CH). CH mitigated catalase activity reduction in hDPCs, increased IGF-1 and VEGF levels, and decreased TGF-β1, TNF-α, and IL-1β expression. In vivo, CH treatment improved hair growth index, length, diameter, weight, and density. Scanning electron microscopy revealed reduced hair damage. Moreover, CH up-regulated IGF-1, VEGF, Elastin, and HAS2 mRNA expression while down-regulating TNF-α and IL-1β. CH enhanced hair shine, growth, and skin health while alleviating inflammation. These findings demonstrate the potential of CH in alleviating oxidative stress, promoting hair growth, and enhancing skin health, both in vitro and in vivo. Fish-derived CH offers a cost-effective and bioavailable option for improving hair and skin health.

Hdac1 and Hdac2 regulate the quiescent state and survival of hair-follicle mesenchymal niche

While cell division is essential for self-renewal and differentiation of stem cells and progenitors, dormancy is required to maintain the structure and function of the stem-cell niche. Here we use the hair follicle to show that during growth, the mesenchymal niche of the hair follicle, the dermal papilla (DP), is maintained quiescent by the activity of Hdac1 and Hdac2 in the DP that suppresses the expression of cell-cycle genes. Furthermore, Hdac1 and Hdac2 in the DP promote the survival of DP cells throughout the hair cycle. While during growth and regression this includes downregulation of p53 activity and the control of p53-independent programs, during quiescence, this predominantly involves p53-independent mechanisms. Remarkably, Hdac1 and Hdac2 in the DP during the growth phase also participate in orchestrating the hair cycle clock by maintaining physiological levels of Wnt signaling in the vicinity of the DP. Our findings not only provide insight into the molecular mechanism that sustains the function of the stem-cell niche in a persistently changing microenvironment, but also unveil that the same mechanism provides a molecular toolbox allowing the DP to affect and fine tune the microenvironment.

Vitamin A regulates dermal papilla cell proliferation and apoptosis under heat stress via IGF1 and Wnt10b signaling

Heat stress (HS) negatively affects the development of hair follicles. The present study investigated the effect of vitamin A (VA) on the development of rabbit dermal papilla cells (DPCs) under HS and the underlying regulatory mechanisms. Addition of 0.4 mg/L VA to the culture medium significantly enhanced cell proliferation (P < 0.001) and inhibited the apoptosis of DPCs (P < 0.01). VA decreased the proportion of DPCs in G0/G1 stage of the cell cycle under HS along with the expression of caspase 3, heat shock protein 70 (HSP70), and microRNA 195 (miR-195) (P < 0.05). VA also activated the insulin-like growth factor 1 (IGF1) and Wnt10b/β-catenin signaling pathways. The results of the dual luciferase reporter assay showed that IGF1 expression was modulated by miR-195-5p. Over-expression of miR-195-5p in DPCs with HS+VA treatment significantly reduced cell viability and IGF1 signaling (P < 0.01) and increased apoptosis (P < 0.01) compared with the HS+VA group. The positive effects of VA on proliferation and apoptosis of DPCs under HS were significantly attenu-ated by blocking Wnt10b and β-catenin signaling with IWP-2 and XAV-939, respectively. These results demonstrate that VA can promote hair follicle development following HS via modulation of miR-195/IGF1 and Wnt10b/β-catenin signaling pathways.

Use of Activated Platelet-Rich Plasma (A-PRP) on Alopecia: A Systematic Review and Meta-Analysis

Alopecia affects perceptions of age, beauty, success, and adaptability. Hair loss can be caused by genetic, physiological, environmental, and immunologic factors. The current treatment for alopecia is varied. This systematic review and meta-analysis evaluates activated platelet rich plasma (A-PRP) for alopecia treatment. The objective of this review was to assess the clinical efficacy and safety of A-PRP injections in alopecia patients. We compared the safety, limitations, and outcomes of A-PRP use with those of previous research on alopecia. We searched PubMed, EMBASE, the Cochrane Database, and Google Scholar for relevant articles. We included all primary clinical studies involving patients that evaluated A-PRP. Twenty-nine articles, which included 864 patients, met the eligibility criteria and were analyzed for qualitative review. Our review found 27 studies that indicated A-PRP was significantly effective in treating alopecia, especially for improving hair density before and after therapy (n = 184, mean difference [MD] = 46.5, I2 = 88%, 95% CI: 29.63, 63.37, P < .00001), as well as when comparison was made between treatment and control groups (n = 88, MD = 31.61, I2 = 80%, 95% CI: 6.99, 56.22, P = .01), and of terminal hair density between treatment and control groups (n = 55, MD = 26.03, I2 = 25%, 95% CI: 8.08, 43.98, P = .004); hair counts after therapy (n = 85, MD = 12.79, I2 = 83%, 95% CI: -5.53, 31.12, P = .0006); promoting hair regrowth; folliculogenesis; reducing hair loss; combining with follicular unit extraction (FUE) surgery; and initiating the hair cycle. Two studies did not report significant results. This is the first systematic review and meta-analysis of A-PRP as a treatment option for alopecia. A-PRP appears to be a promising and safe method for treating alopecia.

LEVEL OF EVIDENCE: 4

Gellan gum-based hydrogels support the recreation of the dermal papilla microenvironment

The dermal papilla (DP), a specialized compartment within the hair follicle, regulates hair growth. However, human DP cells rapidly lose their inductivity in 2D-culture given the loss of positional and microenvironmental cues. Spheroids have been capable of recreating the 3D intercellular organization of DP cells, however, DP cell-matrix interactions are poorly represented. Considering the specific nature of the DP's extracellular matrix (ECM), we functionalized gellan gum (GG) with collagen IV-(HepIII) or fibronectin-(cRGDfC) derived peptide sequences to generate a 3D environment in which the phenotype and physiological functions of DP cells are restored. We further tuned the stiffness of the microenvironments by varying GG amount. Biomimetic peptides in stiffer hydrogels promoted the adhesion of DP cells, while each peptide and amount of polymer independently influenced the type and quantity of ECM proteins deposited. Furthermore, although peptides did not seem to have an influence, stiffer hydrogels improved the inductive capacity of DP cells after short term culture. Interestingly, independently of the peptide, these hydrogels supported the recapitulation of basic hair morphogenesis-like events when incorporated in an organotypic human skin in vitro model. Our work demonstrates that tailored GG hydrogels support the generation of a microenvironment in which both cell-ECM and cell-cell interactions positively influence DP cells towards the creation of an artificial DP.

Cold atmospheric microwave plasma (CAMP) stimulates dermal papilla cell proliferation by inducing β-catenin signaling

Hair loss or alopecia is an unpleasant symptom that exacerbates an individual's self-esteem and requires appropriate treatment. The Wnt/β-catenin signaling is a central pathway that promotes dermal papilla induction and keratinocyte proliferation during hair follicle renewal. GSK-3β inactivated by its upstream Akt and ubiquitin-specific protease 47 (USP47) has been shown to inhibit β-catenin degradation. The cold atmospheric microwave plasma (CAMP) is microwave energy enriched with mixtures of radicals. CAMP has been reported to have antibacterial and antifungal activities with wound healing activity against skin infection; however, the effect of CAMP on hair loss treatment has not been reported. We aimed to investigate the effect of CAMP on promoting hair renewal in vitro and to elucidate the molecular mechanism, targeting β-catenin signaling and YAP/TAZ, the co-activators in the Hippo pathway, in human dermal papilla cells (hDPCs). We also evaluated plasma effects on the interaction between hDPCs and HaCaT keratinocytes. The hDPCs were treated with plasma-activating media (PAM) or gas-activating media (GAM). The biological outcomes were determined by MTT assay, qRT-PCR, western blot analysis, immunoprecipitation, and immunofluorescence. We found that β-catenin signaling and YAP/TAZ were significantly increased in PAM-treated hDPCs. PAM treatment also induced β-catenin translocation and inhibited β-catenin ubiquitination by activating Akt/GSK-3β signaling and upregulating USP47 expression. In addition, hDPCs were more aggregated with keratinocytes in PAM-treated cells compared with control. HaCaT cells cultured in a conditioned medium derived from PAM-treated hDPCs exhibited an enhancing effect on activating YAP/TAZ and β-catenin signaling. These findings suggested that CAMP may be a new therapeutic alternative for alopecic treatment.

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 stem cell fate by HSPGs: implication in hair follicle cycling

Heparan sulfate proteoglycans (HSPGs) are part of proteoglycan family. They are composed of heparan sulfate (HS)-type glycosaminoglycan (GAG) chains covalently linked to a core protein. By interacting with growth factors and/or receptors, they regulate numerous pathways including Wnt, hedgehog (Hh), bone morphogenic protein (BMP) and fibroblast growth factor (FGF) pathways. They act as inhibitor or activator of these pathways to modulate embryonic and adult stem cell fate during organ morphogenesis, regeneration and homeostasis. This review summarizes the knowledge on HSPG structure and classification and explores several signaling pathways regulated by HSPGs in stem cell fate. A specific focus on hair follicle stem cell fate and the possibility to target HSPGs in order to tackle hair loss are discussed in more dermatological and cosmeceutical perspectives.

Construction of transcriptome atlas of white yak hair follicle during anagen and catagen using single-cell RNA sequencing

BACKGROUND

As the direct organ of villus, hair follicles have obvious seasonal cycles. The hair follicle cycle is orchestrated by multiple cell types that together direct cell renewal and differentiation. But the regulation property of hair follicle cells from anagen to catagen in yak is still unknown.

RESULTS

In this study, single-cell RNA sequencing was performed on 24,124 single cells of the scapular skin from white yak. Based on tSNE cluster analysis, the cell types of IFE-DC, epidermal cell lines, fibroblasts, keratinocytes, IRS, DS, INFU, and other cells in yak hair follicles during anagen and catagen were successfully identified, and the gene expression profiles were described. The GO enrichment analysis indicated the different cells characteristic genes to be mainly enriched in the epidermal development, epithelial cell differentiation and wound healing pathways. The pseudotime trajectory analysis described the differentiation trajectory of the epidermal lineage and dermal lineage of the hair follicle during anagen and catagen. Moreover, the dynamic changes of the genes like LHX2, KRT25, and KRT71 were found to be highly expressed in HS and IRS, but not in the IFE-DC, INFU, and keratinocyte during differentiation.

CONCLUSIONS

Our results analyzed the time-varying process of gene expression in the dermal cell lineage and epidermal cell lineage of hair follicles during anagen and catagen during fate differentiation was expounded at the single cell level, revealing the law of fate specialization of different types of cells. In addition, based on the enrichment analysis, the transcriptional regulatory factors involved in the different cell fates were also revealed. These results will help to enhance our understanding of yak hair follicle cycle and promote the development and utilization of yak villus.

The Molecular Mechanism of Natural Products Activating Wnt/β-Catenin Signaling Pathway for Improving Hair Loss

Hair loss, or alopecia, is a dermatological disorder that causes psychological stress and poor quality of life. Drug-based therapeutics such as finasteride and minoxidil have been clinically used to treat hair loss, but they have limitations due to their several side effects in patients. To solve this problem, there has been meaningful progress in elucidating the molecular mechanisms of hair growth and finding novel targets to develop therapeutics to treat it. Among various signaling pathways, Wnt/β-catenin plays an essential role in hair follicle development, the hair cycle, and regeneration. Thus, much research has demonstrated that various natural products worldwide promote hair growth by stimulating Wnt/β-catenin signaling. This review discusses the functional role of the Wnt/β-catenin pathway and its related signaling molecules. We also review the molecular mechanism of the natural products or compounds that activate Wnt/β-catenin signaling and provide insights into developing therapeutics or cosmeceuticals that treat hair loss.

The physiological and pharmacological roles of prostaglandins in hair growth

Hair loss is a common status found among people of all ages. Since the role of hair is much more related to culture and individual identity, hair loss can have a great influence on well-being and quality of life. It is a disorder that is observed in only scalp patients with androgenetic alopecia (AGA) or alopecia areata caused by stress or immune response abnormalities. Food and Drug Administration (FDA)-approved therapeutic medicines such as finasteride, and minoxidil improve hair loss temporarily, but when they stop, they have a limitation in that hair loss occurs again. As an alternative strategy for improving hair growth, many studies reported that there is a relationship between the expression levels of prostaglandins (PGs) and hair growth. Four major PGs such as prostaglandin D2 (PGD₂), prostaglandin I2 (PGI₂), prostaglandin E2 (PGE₂), and prostaglandin F2 alpha (PGF₂α) are spatiotemporally expressed in hair follicles and are implicated in hair loss. This review investigated the physiological roles and pharmacological interventions of the PGs in the pathogenesis of hair loss and provided these novel insights for clinical therapeutics for patients suffering from alopecia.

The Hair Growth-Promoting Effect of Gardenia florida Fruit Extract and Its Molecular Regulation

As a herbal medicine, the extract from the fruits of Gardenia florida has been widely used for its antioxidative, hypoglycemic, and anti-inflammatory properties. However, whether G. florida fruit extract (GFFE) regulates hair growth has been rarely studied. This study was the first application of GFFE on hair growth both in vitro (human dermal papilla cells, hDPCs) and in vivo (C57BL/6 mice). The effects of GFFE on cell proliferation and hair growth-associated gene expression in hDPCs were examined. Moreover, GFFE was applied topically on the hair-shaved skin of male C57BL/6 mice, the hair length was measured, and the skin histological profile was investigated. GFFE promoted the proliferation of hDPCs and significantly stimulated hair growth-promoting genes, including vascular endothelial growth factor (VEGF) and Wnt/β-catenin signals, but suppressed the expression of the hair loss-related gene transforming growth factor-β1 (TGF-β). Furthermore, GFFE treatment resulted in a significant increase in the number, size, and depth of cultured hair follicles and stimulated the growth of hair with local effects in mice. In summary, the results provided the preclinical data to support the much potential use of the natural product GFFE as a promising agent for hair growth.

Lef1 and Dlx3 May Facilitate the Maturation of Secondary Hair Follicles in the Skin of Gansu Alpine Merino

Lymphatic enhancer factor 1 (Lef1) and distal-less homeobox 3 (Dlx3) are the transcription factors involved in regulating hair follicle development in mice, goats, and other animals. Their deletion can lead to hair follicle deficiency. In this study, hematoxylin−eosin staining (HE), real-time quantitative PCR (RT-qPCR), immunohistochemistry, and immunofluorescence were used to analyze the expression, location, and biological functions of Lef1 and Dlx3 in the lateral skin of Gansu Alpine Merino aged 1, 30, 60, and 90 days. The results revealed that the number of hair follicles decreased with age and was significantly higher at 1 day than in the other three age groups (p < 0.05). The mRNA levels of Lef1 and Dlx3 in the skin of 30-day old Gansu Alpine Merino were significantly higher than those in the other three age groups (p < 0.05). Protein expression of Lef1 and Dlx3 was lowest at 1 day (p < 0.05) and peaked at 60 days. Lef1 and Dlx3 exhibited a high density and strong positive expression in the dermal papillae; additionally, Dlx3 exhibited a high density and strong positive expression in the inner and outer root sheaths. Collectively, Lef1 and Dlx3 may facilitate the maturation of secondary hair follicles, which is mainly achieved through the dermal papillae and inner and outer root sheaths.

Regulation of signaling pathways in hair follicle stem cells

Hair follicle stem cells (HFSCs) reside in the bulge region of the outer root sheath of the hair follicle. They are considered slow-cycling cells that are endowed with multilineage differentiation potential and superior proliferative capacity. The normal morphology and periodic growth of HFSCs play a significant role in normal skin functions, wound repair and skin regeneration. The HFSCs involved in these pathophysiological processes are regulated by a series of cell signal transduction pathways, such as lymphoid enhancer factor/T-cell factor, Wnt/β-catenin, transforming growth factor-β/bone morphogenetic protein, Notch and Hedgehog. The mechanisms of the interactions among these signaling pathways and their regulatory effects on HFSCs have been previously studied, but many mechanisms are still unclear. This article reviews the regulation of hair follicles, HFSCs and related signaling pathways, with the aims of summarizing previous research results, revealing the regulatory mechanisms of HFSC proliferation and differentiation and providing important references and new ideas for treating clinical diseases.

Epithelial-Mesenchymal Interaction in Hair Regeneration and Skin Wound Healing

Interactions between epithelial and mesenchymal cells influence hair follicles (HFs) during embryonic development and skin regeneration following injury. Exchanging soluble molecules, altering key pathways, and extracellular matrix signal transduction are all part of the interplay between epithelial and mesenchymal cells. In brief, the mesenchyme contains dermal papilla cells, while the hair matrix cells and outer root sheath represent the epithelial cells. This study summarizes typical epithelial–mesenchymal signaling molecules and extracellular components under the control of follicular stem cells, aiming to broaden our current understanding of epithelial–mesenchymal interaction mechanisms in HF regeneration and skin wound healing.

Vitamin A alleviates heat stress-induced damage to hair follicle development in Rex rabbits

BACKGROUND

Rex rabbits are important fur rabbits. Heat stress severely reduces the fur quality of Rex rabbits. The aim of this study was to experimentally investigate the effect of dietary vitamin A (VA) addition on hair follicle development and related signal pathways in Rex rabbits under heat stress.

RESULTS

In the experiment, 90 Rex rabbits were randomly divided into three groups: control group (20-25 °C, fed basic diet), heat stress group (30-34 °C, fed basic diet), and heat stress + VA group (20-25 °C, fed 12 000 IU/kg VA in addition to the basic diet). VA could significantly increase the hair follicle density (P < 0.01), hair length (P < 0.05), and the ratio of secondary to primary hair follicles (P < 0.05). In addition, VA could significantly inhibit the expression of BMP2, BMP4, FGF5, TGF-β1, and miR-214 in heat-stressed Rex rabbits and significantly increase the expression of noggin, IGF1, IGF1R, Wnt10b, CTNNB1, SHH, and miR-203 and the levels of Wnt10b and p-β-catenin; however, there was no significant effect of VA on the expression of EGF and miR-205.

CONCLUSION

The dietary addition of VA can increase the hair follicle density and fur quality of heat-stressed Rex rabbits. Wnt10/β-catenin, insulin-like growth factor 1 (IGF1), fibroblast growth factor 5 (FGF5), noggin-BMP, and sonic hedgehog (SHH) signaling were associated with VA regulation under heat stress. It is possible that miR-205 and miR-194 contribute to the regulation of Wnt10/β-catenin and bone morphogenetic protein (BMP) signaling. © 2021 Society of Chemical Industry.

Potential of Colostrum-Derived Exosomes for Promoting Hair Regeneration Through the Transition From Telogen to Anagen Phase

Human hair dermal papillary (DP) cells comprising mesenchymal stem cells in hair follicles contribute critically to hair growth and cycle regulation. The transition of hair follicles from telogen to anagen phase is the key to regulating hair growth, which relies heavily on the activation of DP cells. In this paper, we suggested exosomes derived from bovine colostrum (milk exosomes, Milk-exo) as a new effective non-surgical therapy for hair loss. Results showed that Milk-exo promoted the proliferation of hair DP cells and rescued dihydrotestosterone (DHT, androgen hormones)-induced arrest of follicle development. Milk-exo also induced dorsal hair re-growth in mice at the level comparable to minoxidil treatment, without associated adverse effects such as skin rashes. Our data demonstrated that Milk-exo accelerated the hair cycle transition from telogen to anagen phase by activating the Wnt/β-catenin pathway. Interestingly, Milk-exo has been found to stably retain its original properties and efficacy for hair regeneration after freeze-drying and resuspension, which is considered critical to use it as a raw material applied in different types of alopecia medicines and treatments. Overall, this study highlights a great potential of an exosome from colostrum as a therapeutic modality for hair loss.

Hair Growth-Promoting Activities of Glycosaminoglycans Extracted from the Tunics of Ascidian (Halocynthia roretzi)

Throughout the ages, hair has had psychological and sociological importance in framing the personality and general appearance of an individual. Despite efforts to solve this problem, no groundbreaking measures have been proposed. Glycosaminoglycans (GAGs) and associated proteoglycans have important functions in homeostatic maintenance and regenerative processes of the skin. However, little is known about the role of these molecules in the regulation of the hair follicle cycle. Three fractions (F1, F2 and F3) were obtained after separation and purification of GAGs from ascidian tunics. F1 was observed to contain a small amount of amino sugar while high contents of galactose and N-acetylglucosamine were noted in F2 and F3. 2-acetamido-2-deoxy-3-O-(β-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose (∆Di-6S) and 2-acetamido-2-deoxy-3-O-(β-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose (∆Di-4S) were the main disaccharide components. F3 exhibited the highest proliferation activity on human follicle dermal papilla (HFDP) cells. In addition, mixed samples (FFM) of F2 and F3 at different concentrations showed peak activities for five days. After cell culture at a concentration of 10 mg/mL and dihydrotestosterone (DHT), the inhibition effect was higher than that for Minoxidil. Application of 10 mg of FFM to the hair of mice for 28 days resulted in a hair growth effect similar to that of Minoxidil, a positive control.

Exosomes Secreted from Adipose-Derived Stem Cells Are a Potential Treatment Agent for Immune-Mediated Alopecia

Background

Alopecia has become an exceedingly prevalent dermatological disorder. Etiologically, infection (bacterial and fungal infection), inflammation, and immune dysregulation are the main causes of immune-mediated hair loss. Treating hair loss has remained challenging as the available therapies are limited. Exosomes from adipose-derived stem cells (ADSC-Exos) have been used for treating neurodegenerative diseases and autoimmune diseases and in wound-healing treatments. However, the function and mechanism of ADSC-Exos in alopecia treatment remain unclear. This study is aimed at investigating the effects of ADSC-Exos on hair growth in vitro and in vivo for potentially treating immune-mediated alopecia and further exploring the underlying mechanism.

Methods

Cell proliferation, migration, and apoptosis of dermal papilla cells (DPCs) that were treated with ADSC-Exos were detected using the cell counting kit-8 (CCK-8) assay, scratch wound-healing assay, and flow cytometry assay, respectively. A C57BL/6 hair-depilated mouse model was established in vivo; then, ADSC-Exos were subcutaneously injected alone or in combined with minoxidil. The effects of ADSC-Exos on hair growth, pathological changes, and the related mechanism were investigated by HE staining, quantitative real‐time PCR (qRT-PCR), western blotting, and RNA sequencing (RNA-seq).

Results

ADSC-Exos significantly promoted DPC proliferation and migration while also reducing apoptosis. In addition, compared with the control group, ADSC-Exos-treated mice had better hair growth, more hair follicles (HFs) and thicker dermis. RNA-seq revealed that the miR-22 and TNF-α signaling pathways were markedly downregulated in DPCs after ADSC-Exos treatment. In addition, according to qRT-PCR and western blotting results, the Wnt/β-catenin signaling pathway was activated in the skin of ADSC-Exos-treated mice.

Conclusion

ADSC-Exos therapy positively affected the promotion of hair regrowth by regulating miR-22, the Wnt/β-catenin signaling pathway, and the TNF-α signaling pathway, implying that ADSC-Exos could be a promising cell-free therapeutic strategy for immune-mediated alopecia.

Tectoridin Stimulates the Activity of Human Dermal Papilla Cells and Promotes Hair Shaft Elongation in Mouse Vibrissae Hair Follicle Culture

To search hair growth-promoting herbal extract, a screening platform of having HEK293T fibroblast being transfected with pTOPFLASH DNA construct was developed over a thousand of herbal extracts and phytochemicals were screened. One of the hits was ethanolic extract of Rhizoma Belamcandae, the rhizome of Belamcanda chinensis (L.) DC. Tectoridin, an isoflavone from Rhizoma Belamcandae, was shown to be responsible for this activation of promoter construct, inducing the transcription of pTOPFLASH in the transfected fibroblasts in a dose-dependent manner. The blockage by DKK-1 suggested the action of tectoridin could be mediated by the Wnt receptor. The hair growth-promoting effects of tectoridin were illustrated in human follicular dermal papilla cells and mouse vibrissae organ cultures. In tectoridin-treated dermal papilla cultures, an activation of Wnt signaling was demonstrated by various indicative markers, including TCF/LEF1 transcriptional activity, nuclear translocation of β-catenin, expressions level of mRNAs encoding axin-related protein, (AXIN2), β-catenin, lymphoid enhancer-binding factor-1 (LEF-1), insulin-like growth factor 1 (IGF-1) and alkaline phosphatase (ALP). In addition, an increase of hair shaft elongation was observed in cultured mouse vibrissae upon the treatment of tectoridin. Tectoridin, as well as the herbal extract of Rhizoma Belamcandae, possesses hair promoting activity, which deserves further development.

Systems for intricate patterning of the vertebrate anatomy

Periodic patterns form intricate arrays in the vertebrate anatomy, notably the hair and feather follicles of the skin, but also internally the villi of the gut and the many branches of the lung, kidney, mammary and salivary glands. These tissues are composite structures, being composed of adjoined epithelium and mesenchyme, and the patterns that arise within them require interaction between these two tissue layers. In embryonic development, cells change both their distribution and state in a periodic manner, defining the size and relative positions of these specialized structures. Their placement is determined by simple spacing mechanisms, with substantial evidence pointing to a variety of local enhancement/lateral inhibition systems underlying the breaking of symmetry. The nature of the cellular processes involved, however, has been less clear. While much attention has focused on intercellular soluble signals, such as protein growth factors, experimental evidence has grown for contributions of cell movement or mechanical forces to symmetry breaking. In the mesenchyme, unlike the epithelium, cells may move freely and can self-organize into aggregates by chemotaxis, or through generation and response to mechanical strain on their surrounding matrix. Different modes of self-organization may coexist, either coordinated into a single system or with hierarchical relationships. Consideration of a broad range of distinct biological processes is required to advance understanding of biological pattern formation. This article is part of the theme issue 'Recent progress and open frontiers in Turing's theory of morphogenesis'.

Stem Cells from Human Exfoliated Deciduous teeth Promote Hair Regeneration in Mouse

Stem cells in different types may interact with each other to maintain homeostasis or growth and the interactions are complicated and extensive. There is increasing evidence that mesenchymal-epithelial interactions in early morphogenesis stages of both tooth and hair follicles show many similarities. In order to explore whether stem cells from one tissue could interact with cells from another tissue, a series of experiments were carried out. Here we successfully extracted and identified stem cells from human exfoliated deciduous teeth (SHED) of 8–12 years old kids, and then found that SHED could promote hair regeneration in a mouse model. In vitro, SHED shortened the hair regeneration cycle and promoted the proliferation and aggregation of dermal cells. In vivo, when SHED and skin cells of C57 mice were subcutaneously co-transplanted to nude mice, more hair was formed than skin cells without SHED. To further explore the molecular mechanism, epidermal and dermal cells were freshly extracted and co-cultured with SHED. Then several signaling molecules in hair follicle regeneration were detected and we found that the expression of Sonic Hedgehog (Shh) and Glioma-associated oncogene 1 (Gli1) was up-regulated. It seems that SHED may boost the prosperity of hairs by increase Shh/Gli1 pathway, which brings new perspectives in tissue engineering and damaged tissue repairing.

Hair-follicle mesenchymal stem-cell activity during homeostasis and wound healing

The mesenchymal components of the hair follicle, the dermal papilla (DP) and dermal sheath (DS), are maintained by hair-follicle dermal stem cells (hfDSCs), but the position of this stem cell population throughout the hair cycle, its contribution to the maintenance of the dermis and the existence of a migratory axis from the DP to the dermis remain unclear. Here we show that during homeostasis DP and DS cells are confined to their compartments, and during the regression phase of the hair cycle, some undergo apoptosis and subsequently are internalized by nearby adipocytes. In contrast, during wound healing, DP/DS cells move towards the wound, but do not directly participate in follicle neogenesis. Furthermore, hfDSCs, driving the cyclic renewal of the DS during the hair cycle, are heterogeneous and housed during the growth phase within the most proximal part of the DS. Our analysis provides insight into the mechanisms of tissue maintenance and unravels a previously-unknown potential function of adipocytes in phagocytosis.

Argan (Argania Spinosa) press cake extract enhances cell proliferation and prevents oxidative stress and inflammation of human dermal papilla cells

BACKGROUND

Hair follicle undergoes a growth cycle under the regulation of dermal papilla cells. Due to their enormous roles, these fibroblast cells have been used in various in vitro studies as a screening model to evaluate the effect of hair growth regulating agents.

OBJECTIVE

In the current study, we aim to check the hair growth potential effect of Argan press cake (APC) extracted using 50 or 80 % aqueous ethanol on human hair follicle dermal papilla cells (HFDPCs) and to determine the molecular mechanism.

METHODS

APC were applied to HFDPCs, then cell proliferation assays, mitochondrial biogenesis assay, and oxidative stress assay were assessed. DNA microarray was performed from the cells treated with our samples and minoxidil. Validation of the results was done using Quantitative Real-Time PCR with primers for hair-growth related genes. GC/MS analysis was used to determine the compounds contained in APC 50 and 80 %.

RESULTS

APC enhanced cell proliferation along with the stimulation of the ATP content. Additionally, APC had an anti-oxidant activity against H₂O₂ mediated oxidative stress preventing dermal papilla cell senescence. Consistent with this, global gene profiling analysis showed an activation of hair growth-related pathway, and a downregulation of inflammation- and oxidative stress-related genes by APC extracts. GC/MS analysis revealed that these extracts contained pure fatty acids, derived sugar chains, and pure compounds including tocopherols, squalene, and spinasterol.

CONCLUSION

Taken together, here we showed that APC extracts had an effect on stimulating hair growth while inhibiting the inflammation and the oxidative stress of HFDPCs and thus can potentially contribute to an anti-hair loss drug development.

KY19382, a novel activator of Wnt/β-catenin signalling, promotes hair regrowth and hair follicle neogenesis

Background and Purpose

The promotion of hair regeneration and growth heavily depends on the activation of Wnt/β‐catenin signalling in the hair follicle, including dermal papilla (DP). KY19382, one of the newly synthesized analogues of indirubin‐3′‐monoxime (I3O), was identified as a Wnt/β‐catenin signalling activator via inhibition of the interaction between CXXC‐type zinc finger protein 5 (CXXC5) and dishevelled (Dvl). Given the close relationship between the Wnt/β‐catenin signalling and hair regeneration, we investigated the effect of KY19382 on hair regrowth and hair follicle neogenesis.

Experimental Approach

In vitro hair induction effects of KY19382 were performed in human DP cells. The hair elongation effects of KY19382 were confirmed through the human hair follicle and vibrissa culture system. In vivo hair regeneration abilities of KY19382 were identified in three models: hair regrowth, wound‐induced hair follicle neogenesis (WIHN) and hair patch assays using C57BL/6 mice. The hair regeneration abilities were analysed by immunoblotting, alkaline phosphatase (ALP) and immunohistochemical staining.

Key Results

KY19382 activated Wnt/β‐catenin signalling and elevated expression of ALP and the proliferation marker PCNA in DP cells. KY19382 also increased hair length in ex vivo‐cultured mouse vibrissa and human hair follicles and induced hair regrowth in mice. Moreover, KY19382 significantly promoted the generation of de novo hair follicles as shown by WIHN and hair patch assays.

Conclusion and Implications

These results indicate that KY19382 is a potential therapeutic drug that exhibits effective hair regeneration ability via activation of the Wnt/β‐catenin signalling for alopecia treatments.

Detecting the Mechanism behind the Transition from Fixed Two-Dimensional Patterned Sika Deer (Cervus nippon) Dermal Papilla Cells to Three-Dimensional Pattern

The hair follicle dermal papilla is critical for hair generation and de novo regeneration. When cultured in vitro, dermal papilla cells from different species demonstrate two distinguishable growth patterns under the conventional culture condition: a self-aggregative three dimensional spheroidal (3D) cell pattern and a two dimensional (2D) monolayer cell pattern, correlating with different hair inducing properties. Whether the loss of self-aggregative behavior relates to species-specific differences or the improper culture condition remains unclear. Can the fixed 2D patterned dermal papilla cells recover the self-aggregative behavior and 3D pattern also remains undetected. Here, we successfully constructed the two growth patterns using sika deer (Cervus nippon) dermal papilla cells and proved it was the culture condition that determined the dermal papilla growth pattern. The two growth patterns could transit mutually as the culture condition was exchanged. The fixed 2D patterned sika deer dermal papilla cells could recover the self-aggregative behavior and transit back to 3D pattern, accompanied by the restoration of hair inducing capability when the culture condition was changed. In addition, the global gene expressions during the transition from 2D pattern to 3D pattern were compared to detect the potential regulating genes and pathways involved in the recovery of 3D pattern and hair inducing capability.

Human fibroblast-derived extracellular vesicles promote hair growth in cultured human hair follicles

Hair loss is a prevalent medical condition affecting both genders. In this study, we investigate the effects of a specific class of extracellular vesicles (EVs), namely human normal fibroblast-derived EVs (hFB-EVs), on human dermal papilla (DP) and outer root sheath (ORS) cells and examine the molecular mechanisms responsible for hair growth in hair follicles (HFs). We find that Wnt3a, which maintains the hair-generating activity of DP cells, is enriched and more strongly associated with hFB-EVs than with fibroblasts. Furthermore, hFB-EV-associated Wnt3a mediated receptor activation in cultured DP cells, leading to an increase in β-catenin in the cytoplasm and its translocation into the nucleus, thereby elevating expression of the target genes Axin2 and Lef1. Additionally, hFB-EVs promoted the migration, proliferation, and differentiation of ORS cells and elongation of the hair shaft in human HFs. These findings revealed a novel mechanism by which hFB-EVs influence hair growth.

Investigating PEGDA and GelMA Microgel Models for Sustained 3D Heterotypic Dermal Papilla and Keratinocyte Co-Cultures

Hair follicle morphogenesis is heavily dependent on reciprocal, sequential, and epithelial-mesenchymal interaction (EMI) between epidermal stem cells and the specialized cells of the underlying mesenchyme, which aggregate to form the dermal condensate (DC) and will later become the dermal papilla (DP). Similar models were developed with a co-culture of keratinocytes and DP cells. Previous studies have demonstrated that co-culture with keratinocytes maintains the in vivo characteristics of the DP. However, it is often challenging to develop three-dimensional (3D) DP and keratinocyte co-culture models for long term in vitro studies, due to the poor intercellular adherence between keratinocytes. Keratinocytes exhibit exfoliative behavior, and the integrity of the DP and keratinocyte co-cultured spheroids cannot be maintained over prolonged culture. Short durations of culture are unable to sufficiently allow the differentiation and re-programming of the keratinocytes into hair follicular fate by the DP. In this study, we explored a microgel array approach fabricated with two different hydrogel systems. Using poly (ethylene glycol) diacrylate (PEGDA) and gelatin methacrylate (GelMA), we compare their effects on maintaining the integrity of the cultures and their expression of important genes responsible for hair follicle morphogenesis, namely Wnt10A, Wnt10B, and Shh, over prolonged duration. We discovered that low attachment surfaces such as PEGDA result in the exfoliation of keratinocytes and were not suitable for long-term culture. GelMA, on the hand, was able to sustain the integrity of co-cultures and showed higher expression of the morphogens overtime.

Acellular dermal matrix in skin wound healing in rabbits - histological and histomorphometric analyses

OBJECTIVES

To analyze the histology and histomorphometry of healing associated with acellular dermal matrix in skin wounds in rabbits.

METHODS

Twelve male rabbits were divided into two groups: the control group (CG) and the matrix group (MG). Three skin wounds with a total area of 20 × 20 mm were created on the dorsal region of each animal. Photographic records of the lesions taken over a 21-day period and use of the ImageJ program allowed calculation of the wound contraction rate. The lesions were biopsied on days 3, 14 and 21 for histomorphometric analysis to define the thicknesses of the dermis and epidermis (hematoxylin-eosin) and calculate the densities of type I and type III collagen (picrosirius).

RESULTS

No significant difference in the healing rate was found between the groups (p>0.05). The MG presented greater epidermal thickness on day 3 (p<0.05) and on days 14 and 21 (p<0.001). The MG presented greater dermal thickness throughout the study period (p<0.05). The type I collagen density was higher in the MG throughout the study period (p<0.05), and the type III collagen density was higher in the MG on days 3 and 14 (p<0.05) and on day 21 (p<0.001).

CONCLUSION

The use of acellular dermal matrix increased the thickness of the dermal and epidermal layers and the amount of type I and III collagen during skin wound healing and did not alter the rate of wound contraction.

Hair growth potential of Salvia plebeia extract and its associated mechanisms

Context: Although Salvia plebeia (SP) R. Brown (Labiatae) is known to possess various biological activities, the effects of SP on hair growth have not been elucidated.Objective: To investigate the hair growth potential of SP extract by using human dermal papilla cells (hDPCs) and C57BL/6 mice.Materials and methods: The entire SP plant sample was ground into powder and extracted with 99.9% methyl alcohol. Various concentrations of SP extract were added to hDPCs to evaluate the proliferation, migration, and factors related to hair growth and cycling. Effect of topical SP administration on hair regrowth was tested in vivo in male C57BL/6 mice for 21 days.Results: SP extract significantly increased the proliferation of cultured hDPCs at doses of 15.6 and 31.3 μg/mL compared to control group by 123% and 132%, respectively. Expression of hepatocyte growth factor increased while the level of TGF-β1 and SMAD2/3 decreased when treated with SP extract. At the molecular level, the extract activated Wnt/β-catenin signalling by raising β-catenin and phospho-GSK3β expression. SP extract also exerted anti-apoptotic and proliferative effects in hDPCs by increasing the Bcl-2/Bax ratio and activating cell proliferation-related proteins, ERK and Akt. Finally, the extract caused an induction of the anagen phase leading to significantly enhanced hair growth in treated male mice.Discussion and conclusion: Our results indicate that SP extract has the capacity to activate hDPCs into a proliferative state to promote hair growth. Further research is necessary to determine the bioactive components and their mechanisms of action responsible for SP-related hair growth effect.

Amelioration of Androgenetic Alopecia by Algal Oligosaccharides Prepared by Deep-Sea Bacterium Biodegradation

Androgenetic alopecia (AGA) is a dihydrotestosterone (DHT)-mediated hair loss disorder characterized by shortened anagen hair cycle. Oligosaccharides derived from seaweeds possess diverse biological functions. However, little is known about their effects on AGA. In this study, algal oligosaccharide (AOS) was characterized for its mitigation effects on key features involved in AGA pathogenesis, such as DHT- mediated cellular signaling and shortened anagen hair cycle. AOS with varying degrees of polymerization (DP), namely, AOS (DP2), AOS (DP4-6), and AOS (DP8-12), were prepared by agar biodegradation with Flammeovirga pacifica WPAGA1, an agarolytic bacterium isolated from deep-sea sediments. In vitro results showed that AOS with varying DPs significantly ameliorated the DHT-induced alterations of regulatory factors in human hair follicle dermal papilla cells in a dose- and DP-dependent manner, as revealed by the normalization of several hair-growth-stimulating or inhibitory factors. In vivo studies showed that AOS (DP2) extended the anagen phase and thereby delayed catagen progression in mice. Furthermore, AOS (DP2) stimulated dorsal hair growth in mice by increasing hair length, density, and thickness. Therefore, our findings indicated that AOS antagonized key factors involved in AGA pathogenesis, suggesting the potential application of AOS in the prevention and the treatment of AGA.

Fgf and Wnt signaling interaction in the mesenchymal niche regulates the murine hair cycle clock

Tissue growth in the adult is an orchestrated process that often requires biological clocks to time stem cell and progenitor activity. Here, we employed the hair follicle, which cycles between growth and regression in a timely-restricted mode, to show that some components of the hair cycle clock reside within the mesenchymal niche of the hair follicle, the dermal papilla (DP), and both Fgf and Wnt signaling pathways interact within the DP to regulate the expression of these components that include Wnt agonists (Rspondins) and antagonists (Dkk2 and Notum). The levels of Wnt agonists and antagonists in the DP are progressively reduced and elevated during the growth phase, respectively. Consequently, Wnt signaling activity in the overlying epithelial progenitor cells decreases, resulting in the induction of the regression phase. Remarkably, DP properties allow Wnt activity in the DP to persist despite the Wnt-inhibiting milieu and consequently synchronize the induction and progression of the regression phase. This study provides insight into the importance of signaling crosstalk in coupling progenitors and their niche to regulate tissue growth.

The underlying mechanisms regulating the mouse hair cycle remain poorly understood. Here, the authors find that Fgf and Wnt signaling pathways interact in the mesenchymal niche of the hair follicle to regulate the molecular clock that dictates the duration of hair growth.