Divergent progression pathways in male androgenetic alopecia and female pattern hair loss: Trichoscopic perspectives

BACKGROUND

Despite similarities in progressive miniaturization of hair follicles and transition of terminal hairs to vellus hairs, insufficient trichoscopic comparisons between male androgenetic alopecia (MAGA) and female pattern hair loss (FPHL) hinder our ability to select effective treatments.

AIM

Our study aimed to explore gender-specific trichoscopic characteristics of MAGA and FPHL, while formulating hypotheses regarding the progression of these conditions across clinical stages.

METHODS

We classified 126 male MAGA subjects using Hamilton-Norwood Classification and 57 FPHL subjects using adopted Sinclair Scale. Subsequently, we analyzed nine trichoscopic factors divided into three categories: hair-diameter related, hair-number per follicular unit related, and hair density related factors.

RESULTS

Of the nine quantitative trichoscopic factors, hair-diameter and hair-number per follicular unit showed strong correlations with clinical stages in both genders. Hair density, a common trichoscopic factor for hair loss evaluation, weakly correlated with clinical stages in FPHL, but not at all in MAGA. In addition, MAGA was characterized by a progressive reduction in hair-diameter, followed by a reduction in hair-number per follicular unit. FPHL, on the contrary, showed the opposite progression.

CONCLUSIONS

Trichoscopic factors vary with disease severity in a gender-specific manner. Our research highlights that MAGA and FPHL involve two distinct streams: hair-diameter decreasing by hair follicle miniaturization (Stream 1), and hair-number per follicular unit decreasing by hair follicle tri-lineage niche dysfunction (Stream 2). MAGA typically starts from Stream 1 to Stream 2, while FPHL starts from Stream 2. These diverse progression pathways underscore the importance of personalized treatment approaches.

The decline in cellular iron is crucial for differentiation in keratinocytes

Iron is a vital metal for most biological functions in tissues, and its concentration is exquisitely regulated at the cellular level. During the process of differentiation, keratinocytes in the epidermis undergo a noticeable reduction in iron content. Conversely, psoriatic lesions, characterized by disruptions in epidermal differentiation, frequently reveal an excessive accumulation of iron within keratinocytes that have undergone differentiation. In this study, we clarified the significance of attenuated cellular iron content in the intricate course of epidermal differentiation. We illustrated this phenomenon through the utilization of hinokitiol, an iron chelator derived from the heartwood of Taiwanese hinoki, which forcibly delivers iron into cells independent of the intrinsic iron-regulation systems. While primary cultured keratinocytes readily succumbed to necrotic cell death by this iron chelator, mild administration of the hinokitiol-iron complex modestly disrupts the process of differentiation in these cells. Notably, keratinocyte model cells HaCaT and anaplastic skin rudiments exhibit remarkable resilience against the cytotoxic impact of hinokitiol, and the potent artificial influx of iron explains a suppressive effect selectively on epidermal differentiation. Moreover, the augmentation of iron content induced by the overexpression of divalent metal transporter 1 culminates in the inhibition of differentiation in HaCaT cells. Consequently, the diminution in cellular iron content emerges as an important determinant influencing the trajectory of keratinocyte differentiation.

Efficient Generation of Skin Organoids from Pluripotent Cells via Defined Extracellular Matrix Cues and Morphogen Gradients in a Spindle-Shaped Microfluidic Device

Pluripotent stem cell-derived skin organoids (PSOs) emerge as a developmental skin model that is self-organized into multiple components, such as hair follicles. Despite their impressive complexity, PSOs are currently generated in the absence of 3D extracellular matrix (ECM) signals and have several major limitations, including an inverted anatomy (e.g., epidermis inside/dermis outside). In this work, a method is established to generate PSOs effectively in a chemically-defined 3D ECM environment. After examining various dermal ECM molecules, it is found that PSOs generated in collagen -type I (COLI) supplemented with laminin 511 (LAM511) exhibit increased growth compared to conventional free-floating conditions, but fail to induce complete skin differentiation due in part to necrosis. This problem is addressed by generating the PSOs in a 3D bioprinted spindle-shaped hydrogel device, which constrains organoid growth longitudinally. This culture system significantly reduces organoid necrosis and leads to a twofold increase in keratinocyte differentiation and an eightfold increase in hair follicle formation. Finally, the system is adapted as a microfluidic device to create asymmetrical gradients of differentiation factors and improves the spatial organization of dermal and epidermal cells. This study highlights the pivotal role of ECM and morphogen gradients in promoting and spatially-controlling skin differentiation in the PSO framework.

Cocktail Cell-Reprogrammed Hydrogel Microspheres Achieving Scarless Hair Follicle Regeneration

The scar repair inevitably causes damage of skin function and loss of skin appendages such as hair follicles (HF). It is of great challenge in wound repair that how to intervene in scar formation while simultaneously remodeling HF niche and inducing in situ HF regeneration. Here, chemical reprogramming techniques are used to identify a clinically chemical cocktail (Tideglusib and Tamibarotene) that can drive fibroblasts toward dermal papilla cell (DPC) fate. Considering the advantage of biomaterials in tissue repair and their regulation in cell behavior that may contributes to cellular reprogramming, the artificial HF seeding (AHFS) hydrogel microspheres, inspired by the natural processes of "seeding and harvest", are constructed via using a combination of liposome nanoparticle drug delivery system, photoresponsive hydrogel shell, positively charged polyamide modification, microfluidic and photocrosslinking techniques. The identified chemical cocktail is as the core nucleus of AHFS. In vitro and in vivo studies show that AHFS can regulate fibroblast fate, induce fibroblast-to-DPC reprogramming by activating the PI3K/AKT pathway, finally promoting wound healing and in situ HF regeneration while inhibiting scar formation in a two-pronged translational approach. In conclusion, AHFS provides a new and effective strategy for functional repair of skin wounds.

Generation and characterization of a Dkk4-Cre knock-in mouse line

Ectodermal appendages in mammals, such as teeth, mammary glands, sweat glands and hair follicles, are generated during embryogenesis through a series of mesenchymal-epithelial interactions. Canonical Wnt signaling and its inhibitors are implicated in the early steps of ectodermal appendage development and patterning. To study the activation dynamics of the Wnt target and inhibitor Dickkopf4 (Dkk4) in ectodermal appendages, we used CRSIPR/Cas9 to generate a Dkk4-Cre knock-in mouse (Mus musculus) line, where the Cre recombinase cDNA replaces the expression of endogenous Dkk4. Using Cre reporters, the Dkk4-Cre activity was evident at the prospective sites of ectodermal appendages, overlapping with the Dkk4 mRNA expression. Unexpectedly, a predominantly mesenchymal cell population in the embryo posterior also showed Dkk4-Cre activity. Lineage-tracing suggested that these cells are likely derived from a few Dkk4-Cre-expressing cells in the epiblast at early gastrulation. Finally, our analyses of Dkk4-Cre-expressing cells in developing hair follicle epithelial placodes revealed intra- and inter-placodal cellular heterogeneity, supporting emerging data on the positional and transcriptional cellular variability in placodes. Collectively, we propose the new Dkk4-Cre knock-in mouse line as a suitable model to study Wnt and DKK4 inhibitor dynamics in early mouse development and ectodermal appendage morphogenesis.

Modeling of solar UV-induced photodamage on the hair follicles in human skin organoids

Solar ultraviolet (sUV) exposure is known to cause skin damage. However, the pathological mechanisms of sUV on hair follicles have not been extensively explored. Here, we established a model of sUV-exposed skin and its appendages using human induced pluripotent stem cell-derived skin organoids with planar morphology containing hair follicles. Our model closely recapitulated several symptoms of photodamage, including skin barrier disruption, extracellular matrix degradation, and inflammatory response. Specifically, sUV induced structural damage and catagenic transition in hair follicles. As a potential therapeutic agent for hair follicles, we applied exosomes isolated from human umbilical cord blood-derived mesenchymal stem cells to sUV-exposed organoids. As a result, exosomes effectively alleviated inflammatory responses by inhibiting NF-κB activation, thereby suppressing structural damage and promoting hair follicle regeneration. Ultimately, our model provided a valuable platform to mimic skin diseases, particularly those involving hair follicles, and to evaluate the efficacy and underlying mechanisms of potential therapeutics.

Controlling Hair Loss by Regulating Apoptosis in Hair Follicles: A Comprehensive Overview

Apoptosis is a physiological process that occurs in all cell types of the human body, and it profoundly changes the fate of hair by affecting hair follicle cells. This review outlines the cellular changes, intrinsic biochemical characteristics, and mechanisms underlying apoptosis and summarizes the hair follicle life cycle, including development, cycle stages, and corresponding cellular changes. Finally, the relationship between apoptosis and the hair cycle is discussed and the significance of apoptosis in hair loss conditions and drug treatments is highlighted. Apoptosis induces cellular changes and exhibits distinctive properties through intricate signaling pathways. Hair follicles undergo cyclic periods of growth, regression, and dormancy. Apoptosis is closely correlated with the regression phase by triggering hair follicle cell death and shedding. Regulation of apoptosis in hair follicles plays an essential role in hair loss due to maladies and drug treatments. Mitigating apoptosis can enhance hair growth and minimize hair loss. A comprehensive understanding of the correlation between apoptosis and the hair cycle can facilitate the development of novel treatments to prevent hair loss and stimulate hair regeneration.

Multi-Stage Transcriptome Analysis Revealed the Growth Mechanism of Feathers and Hair Follicles during Induction Molting by Fasting in the Late Stage of Egg Laying

Induced molting is a common method to obtain a new life in laying hens, in which periodic changes in feathers are the prominent feature. Nevertheless, its precise molecular mechanism remains unclear. In this study, feather and hair follicle samples were collected during fasting-induced physiological remodeling for hematoxylin-eosin staining, hormone changes and follicle traits, and transcriptome sequencing. Feather shedding was observed in F13 to R25, while newborns were observed in R3 to R32. Triiodothyronine and tetraiodothyronine were significantly elevated during feather shedding. The calcium content was significantly higher, and the ash content was significantly lower after the changeover. The determination of hair follicle traits revealed an increasing trend in pore density and a decrease in pore diameter after the resumption of feeding. According to RNA-seq results, several core genes were identified, including DSP, CDH1, PKP1, and PPCKB, which may have an impact on hair follicle growth. The focus was to discover that starvation may trigger changes in thyroid hormones, which in turn regulate feather molting through thyroid hormone synthesis, calcium signaling, and thyroid hormone signaling pathways. These data provide a valuable resource for the analysis of the molecular mechanisms underlying the cyclical growth of hair follicles in the skin during induced molting.

Follicle-Targeted Delivery of Betamethasone and Minoxidil Co-Entrapped in Polymeric and Lipid Nanoparticles for Topical Alopecia Areata Treatment

Alopecia areata is managed with oral corticosteroids, which has known side effects for patients. Given that a topical application of formulations containing a corticoid and a substance controlling hair loss progression could reduce or eliminate such adverse effects and increase the patient's adherence to the treatment, this study prepares polymeric and lipidic nanoparticles (PNPs and NLCs) to co-entrap minoxidil and betamethasone and compares the follicular drug delivery provided by topical application of these nanoparticles. The prepared PNPs loaded 99.1 ± 13.0% minoxidil and 70.2 ± 12.8% betamethasone, while the NLCs entrapped 99.4 ± 0.1 minoxidil and 80.7 ± 0.1% betamethasone. PNPs and NLCs presented diameters in the same range, varying from 414 ± 10 nm to 567 ± 30 nm. The thermal analysis revealed that the production conditions favor the solubilization of the drugs in the nanoparticles, preserving their stability. In in vitro permeation studies with porcine skin, PNPs provided a 2.6-fold increase in minoxidil penetration into the follicular casts compared to the control and no remarkable difference in terms of betamethasone; in contrast, NLCs provided a significant (specifically, a tenfold) increase in minoxidil penetration into the hair follicles compared to the control, and they delivered higher concentrations of betamethasone in hair follicles than both PNPs and the control. Neither PNPs nor NLCs promoted transdermal permeation of the drugs to the receptor solution, which should favor a topical therapy. Furthermore, both nanoparticles targeted approximately 50% of minoxidil delivery to the follicular casts and NLCs targeted 74% of betamethasone delivery to the hair follicles. In conclusion, PNPs and NLCs are promising drug delivery systems for enhancing follicular targeting of drugs, but NLCs showed superior performance for lipophilic drugs.

Potential Natural Products Regulation of Molecular Signaling Pathway in Dermal Papilla Stem Cells

Stem cells have demonstrated significant potential for tissue engineering and repair, anti-aging, and rejuvenation. Hair follicle stem cells can be found in the dermal papilla at the base of the follicle and the bulge region, and they have garnered increased attention because of their potential to regenerate hair as well as their application for tissue repair. In recent years, these cells have been shown to affect hair restoration and prevent hair loss. These stem cells are endowed with mesenchymal characteristics and exhibit self-renewal and can differentiate into diverse cell types. As research in this field continues, it is probable that insights regarding stem cell maintenance, as well as their self-renewal and differentiation abilities, will benefit the application of these cells. In addition, an in-depth discussion is required regarding the molecular basis of cellular signaling and the influence of nature-derived compounds in stimulating the stemness properties of dermal papilla stem cells. This review summarizes (i) the potential of the mesenchymal cells component of the hair follicle as a target for drug action; (ii) the molecular mechanism of dermal papilla stem cells for maintenance of their stem cell function; and (iii) the positive effects of the natural product compounds in stimulating stemness in dermal papilla stem cells. Together, these insights may help facilitate the development of novel effective hair loss prevention and treatment.

Hypoxia Treatment of Adipose Mesenchymal Stem Cells Promotes the Growth of Dermal Papilla Cells via HIF-1α and ERK1/2 Signaling Pathways

Dermal papilla cells (DPCs) cultured in vitro induce hair follicle formation. Using a hypoxic microenvironment to culture adipose mesenchymal stem cells (ADSCs) can promote hair follicle growth. However, the exact molecular mechanisms underlying this process remain unclear. In this study, ADSCs and DPCs from Arbas Cashmere goats were used. A hypoxic microenvironment promoted the proliferation of ADSCs and increased the pluripotency of ADSCs. The growth factors vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF) were upregulated in ADSCs in the hypoxia-conditioned medium (Hypo-cm). Hypo-cm also enhanced the ability of DPCs to induce hair follicle formation. Inhibitors of the ERK1/2 signaling pathway caused the expressions of growth factors that increased in hypoxic microenvironments to decrease; moreover, hypoxia-inducible factor-1α (HIF-1α) increased the expression levels of VEGF, bFGF, and PDGF and inhibited the expression of bone morphogenic protein 7 (BMP7). In conclusion, these findings improve the theoretical basis for the development of gene therapy drugs for the treatment of alopecia areata and hair thinning.

Diagnosis and differential diagnosis of tertiary androgenetic alopecia with severe alopecia areata based on high-resolution MRI

BACKGROUND AND AIM

No previous study investigated the anatomical changes of the scalp and hair follicles between tertiary androgenetic alopecia and severe alopecia areata using high-resolution magnetic resonance imaging (HR-MRI). This study aimed to explore the value of HR-MRI in assessing alopecia.

MATERIALS AND METHODS

Forty-eight people were included in this study. The imaging indicators of the vertex and occipital scalp were recorded and compared. The logistic regression model was developed for the indicators that differed between tertiary androgenetic alopecia and severe alopecia areata. The receiver-operating characteristic (ROC) curve was used to assess the diagnostic efficacy of the model for tertiary androgenetic alopecia and severe alopecia areata.

RESULTS

At the vertex, the thickness of the subcutaneous tissue layer, follicle depth, relative follicle depth, total number of follicles within a 2-cm distance, and number of strands reaching the middle and upper third of the subcutaneous fat layer within a 2-cm distance were statistically different between patients with tertiary androgenetic alopecia, those with severe alopecia areata, and healthy volunteers (p < 0.05). The logistic regression model suggested that the subcutaneous tissue layer thickness was important in discriminating tertiary androgenetic alopecia from severe alopecia areata. The ROC curve showed that the area under the curve, sensitivity, specificity, and best cutoff values of the subcutaneous tissue layer were 0.886, 94.4%, 70%, and 4.31 mm, respectively.

CONCLUSIONS

HR-MRI can observe the changes in anatomical structures of the scalp and hair follicles in patients with alopecia. HR-MRI can be applied to the differential diagnosis of tertiary androgenetic alopecia and severe alopecia areata.

Erratum: Corrigendum: Water extract of cacumen platycladi promotes hair growth through the Akt/GSK3β/β-catenin signaling pathway

[This corrects the article DOI: 10.3389/fphar.2023.1038039.].

Confocal microscopy and optical coherence tomography of inflammatory skin diseases in hairs and pilosebaceous units: A systematic review

Common skin disorders such as acne vulgaris, rosacea and folliculitis are bothersome prevalent inflammatory diseases of hair follicles that can easily be investigated bedside using optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) with micrometre resolution, opening a novel era for high-resolution hair follicle diagnostics and quantitative treatment evaluation. EMBASE, PubMed and Web of Science were searched until 5 January 2023 to identify all studies imaging hair follicle characteristics by RCM and OCT for diagnosis and monitoring of treatment in hair follicle-based skin disorders. This study followed PRISMA guidelines. After inclusion of articles, methodological quality was assessed using the QUADAS-2 critical appraisal checklist. Thirty-nine in vivo studies (33 RCM and 12 OCT studies) were included. The studies focused on acne vulgaris, rosacea, alopecia areata, hidradenitis suppurativa, folliculitis, folliculitis decalvans, lichen planopilaris, discoid lupus erythemasus, frontal fibrosing alopecia and keratosis pilaris. Inter- and perifollicular morphology including number of demodex mites, hyperkeratinization, inflammation and vascular morphology could be assessed by RCM and OCT in all included skin disorders. Methodological study quality was low, and interstudy outcome variability was high. Quality assessment showed high or unclear risk of bias in 36 studies. Both RCM and OCT visualize quantitative features as size, shape, content and abnormalities of hair follicles, and have potential to support clinical diagnosis and evaluate treatment effects. However, larger studies with better methodological quality are needed to implement RCM and OCT directly into clinical practice.

Cytotoxicity, Dermal Toxicity, and In Vivo Antifungal Effect of Griseofulvin-Loaded Vaterite Carriers Administered via Sonophoresis

The search for novel therapeutic strategies to treat fungal diseases is of special importance nowadays given the emerging threat of drug resistance. Various particulate delivery systems are extensively being developing to enhance bioavailability, site-specific penetration, and therapeutic efficacy of antimycotics. Recently, we have designed a novel topical formulation for griseofulvin (Gf) drug, which is currently commercially available in oral dosage forms due to its limited skin permeation. The proposed formulation is based on vaterite carriers that enabled effective incorporation and ultrasonically assisted delivery of Gf to hair follicles improving its dermal bioavailability. Here, we evaluated the effect of ultrasound on the viability of murine fibroblasts co-incubated with either Gf-loaded carriers or a free form of Gf and investigated the influence of both forms on different subpopulations of murine blood cells. The study revealed no sufficient cyto- and hemotoxicity of the carriers, even at the highest investigated concentrations. We also conducted a series of in vivo experiments to assess their multi-dose dermal toxicity and antifungal efficiency. Visual and histological examinations of the skin in healthy rabbits showed no obvious adverse effects after US-assisted application of the Gf-loaded carriers. At the same time, investigation of therapeutic efficiency for the designed formulation in comparison with free Gf and isoconazole drugs in a guinea pig model of trichophytosis revealed that the vaterite-based form of Gf provided the most rapid and effective cure of infected animals together with the reduction in therapeutic procedure number. These findings pave the way to improving antifungal therapy of superficial mycoses and justifying further preclinical studies.

Advanced Skin Antisepsis: Application of UVA-Cleavable Hydroxyethyl Starch Nanocapsules for Improved Eradication of Hair Follicle-Associated Microorganisms

Hair follicles constitute important drug delivery targets for skin antisepsis since they contain ≈25% of the skin microbiome. Nanoparticles are known to penetrate deeply into hair follicles. By massaging the skin, the follicular penetration process is enhanced based on a ratchet effect. Subsequently, an intrafollicular drug release can be initiated by various trigger mechanisms. Here, we present novel ultraviolet A (UVA)-responsive nanocapsules (NCs) with a size between 400 and 600 nm containing hydroxyethyl starch (HES) functionalized by an o-nitrobenzyl linker. A phase transfer into phosphate-buffered saline (PBS) and ethanol was carried out, during which an aggregation of the particles was observed by means of dynamic light scattering (DLS). The highest stabilization for the target medium ethanol as well as UVA-dependent release of ethanol from the HES-NCs was achieved by adding 0.1% betaine monohydrate. Furthermore, sufficient cytocompatibility of the HES-NCs was demonstrated. On ex vivo porcine ear skin, a strong UVA-induced release of the model drug sulforhodamine 101 (SR101) could be demonstrated after application of the NCs in cyclohexane using laser scanning microscopy. In a final experiment, a microbial reduction comparable to that of an ethanol control was demonstrated on ex vivo porcine ear skin using a novel UVA-LED lamp for triggering the release of ethanol from HES-NCs. Our study provides first indications that an advanced skin antisepsis based on the eradication of intrafollicular microorganisms could be achieved by the topical application of UVA-responsive NCs.

Skin-specific transgenic overexpression of ovine β-catenin in mice

β-catenin is a conserved molecule that plays an important role in hair follicle development. In this study, we generated skin-specific overexpression of ovine β-catenin in transgenic mice by pronuclear microinjection. Results of polymerase chain reaction (PCR) testing and Southern blot showed that the ovine β-catenin gene was successfully transferred into mice, and the exogenous β-catenin gene was passed down from the first to sixth generations. Furthermore, real-time fluorescent quantitative PCR (qRT-PCR) and western blot analysis showed that β-catenin mRNA was specifically expressed in the skin of transgenic mice. The analysis of F6 phenotypes showed that overexpression of β-catenin could increase hair follicle density by prematurely promoting the catagen-to-anagen transition. The results showed that ovine β-catenin could also promote hair follicle development in mice. We, therefore, demonstrate domestication traits in animals.

The Philippines stingless bee propolis promotes hair growth through activation of Wnt/β-catenin signaling pathway

Although hair loss is not a horrible disease, it sometimes reduces the patients' quality of life (QOL) and increases their mental stress. Currently, there is no effective treatment for hair loss. It is known that honeybee propolis has various biological activities, including stimulating the proliferation of hair matrix keratinocytes. However, little is known with the hair promoting activity of stingless bee propolis. Hence, this study investigates the hair growth-promoting activity of Philippines stingless bee propolis extract and the underlying a molecular mechanism of promoting hair growth. For the evaluation of hair growth stimulating activity, 99.5% ethanolic extract of Philippines stingless bee propolis is examined using the simple shaving model in C57BL/6N mice. Melaninization of dorsal skin and histological analysis of hair follicles (HFs) revealed that propolis promotes hair growth by stimulating HFs development. The expression of mRNA (Wnt3a, Ctnnb1/β-catenin, Lef1, and Bmp2) and protein (WNT3A and β-catenin) of selected Wnt/β-catenin associated genes explains Philippines stingless bee propolis promoting HFs development by activating Wnt/β-catenin signaling pathway. These results suggest that the treatment of propolis strongly promotes hair growth by stimulating the development of HFs via activation of Wnt/β-catenin signaling pathway. This further indicates the potential of Philippines stingless bee propolis as a novel promising agricultural product for hair growth.

Evaluation of Herbal Hair Lotion loaded with Rosemary for Possible Hair Growth in C57BL/6 Mice

Background

Rosmarinus officinalis (rosemary) is a common household plant with needle-like leaves and white flowers that belongs to the family Lamiaceae and has various medicinal properties including ailments of hair and scalp, cardiovascular, nervous disorders, etc., In the current work, we have focused on formulation and evaluation of 1% hair lotion incorporated with methanolic extract of R. officinalis.

Materials and Methods

The aerial parts of the plant were extracted with methanol and then the nature of phytochemicals were identified by chemical tests. It showed the presence of proteins, amino acids, fats and oils, steroids, glycosides, phenolic compounds, flavonoids, volatile oil, and vitamins. The extract was formulated to a suitable hair lotion and then evaluated for its various quality control parameters. Finally, the lotion was evaluated for hair growth promoting activity on C57BL/6 mice, using water as control and 2% minoxidil hair lotion as standard.

Results

It was observed that the formulated 1% herbal hair lotion passed all the evaluation parameters and showed a significant hair growth promoting activity than the standard drug-treated animals.

Conclusion

Although several researches have been carried out on the rosemary, an investigation on formulation of hair lotion adding the extract of the aerial part of the plant is for the first time. Since our formulation exhibited an excellent activity, it can be well thought out to be an alternative to the commercially available hair growth promoters with a lot of unwanted effects.

Water extract of cacumen platycladi promotes hair growth through the Akt/GSK3β/β-catenin signaling pathway

Cacumen Platycladi (CP) consists of the dried needles of Platycladus orientalis L.) Franco. It was clinically demonstrated that it effectively regenerates hair, but the underlying mechanism remains unknown. Thus, we employed shaved mice to verify the hair growth-promoting capability of the water extract of Cacumen Platycladi (WECP). The morphological and histological analyses revealed that WECP application could significantly promote hair growth and hair follicles (HFs) construction, in comparison to that of control group. Additionally, the skin thickness and hair bulb diameter were significantly increased by the application of WECP in a dose-dependent manner. Besides, the high dose of WECP also showed an effect similar to that of finasteride. In an in vitro assay, WECP stimulated dermal papilla cells (DPCs) proliferation and migration. Moreover, the upregulation of cyclins (cyclin D1, cyclin-dependent kinase 2 (CDK2), and cyclin-dependent kinase 4 (CDK4)) and downregulation of P21 in WECP-treated cell assays have been evaluated. We identified the ingredients of WECP using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS) and endeavored to predict their relevant molecular mechanisms by network analysis. We found that the Akt (serine/threonine protein kinase) signaling pathway might be a crucial target of WECP. It has been demonstrated that WECP treatment activated the phosphorylation of Akt and glycogen synthase kinase-3-beta (GSK3β), promoted β-Catenin and Wnt10b accumulation, and upregulated the expression of lymphoid enhancer-binding factor 1 (LEF1), vascular endothelial growth factor (VEGF), and insulin-like growth factor 1 (IGF1). We also found that WECP significantly altered the expression levels of apoptosis-related genes in mouse dorsal skin. The enhancement capability of WECP on DPCs proliferation and migration could be abrogated by the Akt-specific inhibitor MK-2206 2HCl. These results suggested that WECP might promote hair growth by modulating DPCs proliferation and migration through the regulation of the Akt/GSK3β/β-Catenin signaling pathway.

Comparative Analysis of mRNA and miRNA Expression between Dermal Papilla Cells and Hair Matrix Cells of Hair Follicles in Yak

The interaction between the dermal papilla cells (DPCs) and epidermal hair matrix cells (HMCs) of hair follicles (HFs) is crucial for the growth and development of HFs, but the molecular mechanism is complex and remains unclear. MicroRNAs (miRNAs) are the key signaling molecules for cellular communication. In this study, the DPCs and HMCs of yak were isolated and cultured, and the differentially expressed mRNA and miRNA were characterized to analyze the molecular basis of the interaction between DPCs and HMCs during hair follicle (HF) development in yak. The mRNA differential expression and functional enrichment analysis revealed that there were significant differences between DPCs and HMCs, and they showed the molecular functional characteristics of dermal cells and epidermal cells, respectively. Multiple KEGG pathways related to HF development were enriched in the highly expressed genes in DPCs, while the pathways associated with microbiota and immunity were significantly enriched in the highly expressed genes in HMCs. By combining analysis with our previous 10× genomics single-cell transcriptome data, 39 marker genes of DPCs of yak were identified. A total of 123 relatively specifically expressed miRNAs were screened; among these, the miRNAs associated with HF development such as miR-143, miR-214, miR-125b, miR-31, and miR-200 were presented. In conclusion, the large changes in yak DPCs and HMCs for both mRNA and miRNA expression were revealed, and numerous specifically expressed mRNAs and miRNAs in DPCs or HMCs were identified, which may contribute to the interaction and cellular communication between DPCs and HMCs during HF development in yak.

Scalable and high-throughput production of an injectable platelet-rich plasma (PRP)/cell-laden microcarrier/hydrogel composite system for hair follicle tissue engineering

Background

Tissue engineering of hair follicles (HFs) has enormous potential for hair loss treatment. However, certain challenges remain, including weakening of the dermal papilla cell (DPC) viability, proliferation, and HF inducibility, as well as the associated inefficient and tedious preparation process required to generate extracellular matrix (ECM)-mimicking substrates for biomolecules or cells. Herein, we utilized gelatin methacryloyl (GelMA) and chitosan hydrogels to prepare scalable, monodispersed, and diameter-controllable interpenetrating network GelMA/chitosan-microcarriers (IGMs) loaded with platelet-rich plasma (PRP) and seeded with DPCs, on a high-throughput microfluidic chip.

Results

The ECM-mimicking hydrogels used for IGMs exhibited surface nano-topography and high porosity. Mass production of IGMs with distinct and precise diameters was achieved by adjusting the oil and aqueous phase flow rate ratio. Moreover, IGMs exhibited appropriate swelling and sustained growth factor release to facilitate a relatively long hair growth phase. DPCs seeded on PRP-loaded IGMs exhibited good viability (> 90%), adhesion, spreading, and proliferative properties (1.2-fold greater than control group). Importantly, PRP-loaded IGMs presented a higher hair inducibility of DPCs in vitro compared to the control and IGMs group (p < 0.05). Furthermore, DPC/PRP-laden IGMs were effectively mixed with epidermal cell (EPC)-laden GelMA to form a PRP-loaded DPC/EPC co-cultured hydrogel system (DECHS), which was subcutaneously injected into the hypodermis of nude mice. The PRP-loaded DECHS generated significantly more HFs (~ 35 per site) and novel vessels (~ 12 per site) than the other groups (p < 0.05 for each).

Conclusion

Taken together, these results illustrate that, based on high-throughput microfluidics, we obtained scalable and controllable production of ECM-mimicking IGMs and DECHS, which simulate an effective micro- and macro-environment to promote DPC bioactivity and hair regeneration, thus representing a potential new strategy for HF tissue engineering.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01671-8.

Bioengineering of Hair Follicle-like Structure for Validation of Hair Growth Promoting Compounds

We aimed to establish screening and efficacy test techniques for use in the development of hair-promoting agents. To this end, we used the dermal papilla cell (DPc)-derived immortalized cell line (SV40T-hTERT DPc) and neonatal foreskin-derived keratinocyte cell line (Ker-CT) to form an immortalized cell-based hair follicle-like structure. The SV40T-hTERT DPc spheroids exhibited a higher cell ratio in the spheroids than primary DPc spheroids, and SV40T-hTERT DPc aggregated with spheroids larger in diameter than primary DPc when the same cell number was seeded into the low-adhesion plate. Microscopic imaging and fluorescence staining results indicated that both primary and immortalized cell combinations form a hair follicle-like structure with a long-stretched keratinocyte layer under the condition that the spheroids have the same diameter as that of in vivo dermal papillary tissue in the hair follicle. The hair follicle-like structure elongation was increased upon treatment with three known hair follicle growth-promoting compounds (minoxidil, tofacitinib, and ascorbic acid) compared with that in the control group. Therefore, using immortalized cells to generate a coherent follicle-like structure, we have developed models for screening and evaluating hair-care materials commonly used in the industry.

The Emergent Power of Human Cellular vs Mouse Models in Translational Hair Research

Different animal models have been used for hair research and regeneration studies based on the similarities between animal and human skins. Primary knowledge on hair follicle (HF) biology has arisen from research using mouse models baring spontaneous or genetically engineered mutations. These studies have been crucial for the discovery of genes underlying human hair cycle control and hair loss disorders. Yet, researchers have become increasingly aware that there are distinct architectural and cellular features between the mouse and human HFs, which might limit the translation of findings in the mouse models. Thus, it is enticing to reason that the spotlight on mouse models and the unwillingness to adapt to the human archetype have been hampering the emergence of the long-awaited human hair loss cure. Here, we provide an overview of the major limitations of the mainstream mouse models for human hair loss research, and we underpin a future course of action using human cell bioengineered models and the emergent artificial intelligence.

Application of Cell-Derived Extracellular Vesicles and Engineered Nanovesicles for Hair Growth: From Mechanisms to Therapeutics

Hair loss is one of the most common disorders that affect both male and female patients. Cell-derived nanovesicles (CDVs) are natural extracellular vesicles and engineered nanovesicles that can carry various biologicals materials such as proteins, lipids, mRNA, miRNA, and DNA. These vesicles can communicate with local or distant cells and are capable of delivering endogenous materials and exogenous drugs for regenerative therapies. Recent studies revealed that CDVs can serve as new treatment strategies for hair growth. Herein, we review current knowledge on the role of CDVs in applications to hair growth. The in-depth understanding of the mechanisms by which CDVs enable therapeutic effects for hair growth may accelerate successful clinical translation of these vesicles for treating hair loss.

Preparation of topical bimatoprost with enhanced skin infiltration and in vivo hair regrowth efficacy in androgenic alopecia

To prepare a topical formulation of bimatoprost (BIM) with high skin permeability, we designed a solvent mixture system composed of ethanol, diethylene glycol monoethyl ether, cyclomethicone, and butylated hydroxyanisole, serving as a volatile solvent, nonvolatile co-solvent, spreading agent, and antioxidant, respectively. The ideal topical BIM formulation (BIM–TF#5) exhibited 4.60-fold higher human skin flux and a 529% increase in dermal drug deposition compared to BIM in ethanol. In addition, compared to the other formulations, BIM–TF#5 maximally activated human dermal papilla cell proliferation at a concentration of 5 μM BIM, equivalent to 10 μM minoxidil. Moreover, BIM–TF#5 (0.3% [w/w] BIM) significantly promoted hair regrowth in the androgenic alopecia mouse model and increased the area covered by hair at 10 days by 585% compared to the vehicle-treated mice, indicating that entire telogen area transitioned into the anagen phase. Furthermore, at day 14, the hair weight of mice treated with BIM–TF#5 (5% [w/w] BIM) was 8.45- and 1.30-fold greater than in the 5% (w/w) BIM in ethanol and 5% (w/v) minoxidil treated groups, respectively. In the histological examination, the number and diameter of hair follicles in the deep subcutis were significantly increased in the BIM–TF#5 (0.3 or 5% [w/w] BIM)-treated mice compared to the mice treated with vehicle or 5% (w/w) BIM in ethanol. Thus, our findings suggest that BIM–TF#5 is an effective formulation to treat scalp alopecia, as part of a novel therapeutic approach involving direct prostamide F2α receptor-mediated stimulation of dermal papilla cells within hair follicles.

Network Pharmacology Study and Experimental Confirmation Revealing the Ameliorative Effects of Decursin on Chemotherapy-Induced Alopecia

Decursin, a pyranocoumarin compound from the root of Angelica gigas Nakai as a main constituent, has been reported to have various biological activities, including anti-inflammatory, anticancer, and antioxidant effects. This study aimed to predict and confirm the pharmacological relevance of Decursin on chemotherapy-induced alopecia (CIA) with the underlying molecular mechanisms. Decursin-targeted genes were compared with the gene set of alopecia and investigated through functional enrichment analysis. CIA was induced in C57BL/6J mice by injection of cyclophosphamide, and 1, 10, and 100 μM of Decursin were topically treated to depilated dorsal skin. KGF⁺ expression was detected in the dorsal skin tissues. Based on the predicted results, caspase, PIK3/AKT, and MAPKs protein expressions by Decursin were analyzed in the TNF-α-induced keratinocytes. The Decursin network had 60.20% overlapped genes with the network of alopecia. Biological processes, such as cellular response to chemical stimulus, apoptosis, PI3K-AKT signaling pathway, and MAPK signaling pathway, were derived from the Decursin network. In the Decursin-treated skin, there was morphological hair growth and histological restoration of hair follicles in the CIA mice. The KGF⁺ fluorescence and protein expressions were significantly increased by Decursin treatment. In addition, caspase-3, -7, and -8 expressions, induced by TNF-α, were dose-dependently decreased along with the inhibition of PI3K, AKT, ERK, and p38 expressions in Decursin-treated keratinocytes. These findings indicated that Decursin would be a potent therapeutic option for hair loss, in response to chemotherapy.

Disruption of the endopeptidase ADAM10-Notch signaling axis leads to skin dysbiosis and innate lymphoid cell-mediated hair follicle destruction

Hair follicles (HFs) function as hubs for stem cells, immune cells, and commensal microbes, which must be tightly regulated during homeostasis and transient inflammation. Here we found that transmembrane endopeptidase ADAM10 expression in upper HFs was crucial for regulating the skin microbiota and protecting HFs and their stem cell niche from inflammatory destruction. Ablation of the ADAM10-Notch signaling axis impaired the innate epithelial barrier and enabled Corynebacterium species to predominate the microbiome. Dysbiosis triggered group 2 innate lymphoid cell-mediated inflammation in an interleukin-7 (IL-7) receptor-, S1P receptor 1-, and CCR6-dependent manner, leading to pyroptotic cell death of HFs and irreversible alopecia. Double-stranded RNA-induced ablation models indicated that the ADAM10-Notch signaling axis bolsters epithelial innate immunity by promoting β-defensin-6 expression downstream of type I interferon responses. Thus, ADAM10-Notch signaling axis-mediated regulation of host-microbial symbiosis crucially protects HFs from inflammatory destruction, which has implications for strategies to sustain tissue integrity during chronic inflammation.

Structural characterization of human peptidyl-arginine deiminase type III by X-ray crystallography

The Ca2+-dependent enzyme peptidyl-arginine deiminase type III (PAD3) catalyses the deimination of arginine residues to form citrulline residues in proteins such as keratin, filaggrin and trichohyalin. This is an important post-translation modification that is required for normal hair and skin formation in follicles and keratocytes. The structure of apo human PAD3 was determined by X-ray crystallography to a resolution of 2.8 Å. The structure of PAD3 revealed a similar overall architecture to other PAD isoforms: the N-terminal and middle domains of PAD3 show sequence and structural variety, whereas the sequence and structure of the C-terminal catalytic domain is highly conserved. Structural analysis indicates that PAD3 is a dimer in solution, as is also the case for the PAD2 and PAD4 isoforms but not the PAD1 isoform.

Recent Progress in the Understanding of the Effect of Sympathetic Nerves on Hair Follicle Growth

Clinical observation and experimental studies have long suggested that the perifollicular nerves have nutritional and regulatory effects on the growth, development, and physiological cycle of hair follicles (HFs), even though the concrete mechanism remains obscure. Recently, with the progress of immunohistochemistry and molecular biology techniques, more innovation has been made in the study of the follicular sympathetic nerves and its nerve-effect factor norepinephrine affecting hair follicle stem cells. This review highlights the progress in the regulation of the sympathetic nervous system toward the growth of HFs.

Ergonomics in follicular unit excision surgery

BACKGROUND

Concentration and physical strength are essential for the long duration of hair transplant surgery. Because both the patient and the doctor must maintain certain postures for long periods, the importance of ergonomics cannot be understated.

AIMS

To review the devices, instruments, and techniques developed for ergonomic follicular unit excision surgery, to present our experience with various ergonomic modifications, and to evaluate the effectiveness of the related devices, novel concepts, and methods.

METHODS

We evaluated the scientific evidence supporting the ideas, methods, devices, and systems to help create a better ergonomic environment, and we investigated how these elements can be fine-tuned to improve efficiency when performing follicular unit excision graft harvesting.

RESULTS

Through innovative methods, ideas, devices, and instruments, the authors achieved a high-quality ergonomic environment for performing follicular unit excision.

CONCLUSION

Follicular unit excision is a widely used technique in hair restoration surgery. However, follicular unit excision is a very laborious and time-consuming procedure and mandates the best ergonomic conditions for both the surgeon and the patient. Therefore, it is crucial that the physician understands and appropriately adopts the various means and techniques to provide an ergonomic environment.

Expression Profiling and Functional Analysis of Circular RNAs in Inner Mongolian Cashmere Goat Hair Follicles

Background

Inner Mongolian cashmere goats have hair of excellent quality and high economic value, and the skin hair follicle traits of cashmere goats have a direct and important effect on cashmere yield and quality. Circular RNA has been studied in a variety of tissues and cells.

Result

In this study, high-throughput sequencing was used to obtain the expression profiles of circular RNA (circRNA) in the hair follicles of Inner Mongolian cashmere goats at different embryonic stages (45, 55, 65, and 75 days). A total of 21,784 circRNAs were identified. At the same time, the differentially expressed circRNA in the six comparison groups formed in the four stages were: d75vsd45, 59 upregulated and 33 downregulated DE circRNAs; d75vsd55, 61 upregulated and 102 downregulated DE circRNAs; d75vsd65, 32 upregulated and 33 downregulated DE circRNAs; d65vsd55, 67 upregulated and 169 downregulated DE circRNAs; d65vsd45, 96 upregulated and 63 downregulated DE circRNAs; and d55vsd45, 76 upregulated and 42 downregulated DE circRNAs. Six DE circRNA were randomly selected to verify the reliability of the sequencing results by quantitative RT-PCR. Subsequently, the circRNA corresponding host genes were analyzed by the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. The results showed that the biological processes related to hair follicle growth and development enriched by GO mainly included hair follicle morphogenesis and cell development, and the signaling pathways related to hair follicle development included the Notch signaling pathway and NF-κB signaling pathway. We combined the DE circRNA of d75vsd45 with miRNA and mRNA databases (unpublished) to construct the regulatory network of circRNA–miRNA–mRNA, and formed a total of 102 pairs of circRNA–miRNA and 126 pairs of miRNA–mRNA interactions. The binding relationship of circRNA3236–chi-miR-27b-3p and circRNA3236–chi-miR-16b-3p was further verified by dual-luciferase reporter assays, and the results showed that circRNA3236 and chi-miR-27b-3p, and circRNA3236 and chi-miR-16b-3p have a targeted binding relationship.

Conclusion

To summarize, we established the expression profiling of circRNA in the fetal skin hair follicles of cashmere goats, and found that the host gene of circRNA may be involved in the development of hair follicles of cashmere goats. The regulatory network of circRNA–miRNA–mRNA was constructed and preliminarily verified using DE circRNAs.

Regional Variation in Epidermal Susceptibility to UV-Induced Carcinogenesis Reflects Proliferative Activity of Epidermal Progenitors

To better understand the influence of ultraviolet (UV) irradiation on the initial steps of skin carcinogenesis, we examine patches of labeled keratinocytes as a proxy for clones in the interfollicular epidermis (IFE) and measure their size variation upon UVB irradiation. Multicolor lineage tracing reveals that in chronically irradiated skin, patches near hair follicles (HFs) increase in size, whereas those far from follicles do not change. This is explained by proliferation of basal epidermal cells within 60 μm of HF openings. Upon interruption of UVB, patch size near HFs regresses significantly. These anatomical differences in proliferative behavior have significant consequences for the cell of origin of basal cell carcinomas (BCCs). Indeed, a UV-inducible murine BCC model shows that BCC patches are more frequent, larger, and more invasive near HFs. These findings have major implications for the prevention of field cancerization in the epidermis.

Investigating the Safety and Efficacy of Platelet-Rich Plasma (PRP) Treatment for Female Androgenetic Alopecia: Review of the Literature

Background: female androgenetic alopecia (FAGA) is a common cause of non-scarring alopecia in women, affecting approximately 40% of women by age 50, bearing a significant psychosocial burden on affected patients. Platelet-rich plasma (PRP) has been widely investigated as a potential effective treatment for several dermatological conditions, including male androgenetic alopecia (MAGA). However, few studies have been conducted focusing on the use of PRP in FAGA. The aim of this review was to identify reports that investigated the use of PRP for the treatment of FAGA. Methods: Electronic databases of MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) from inception to September 2020 have been searched using different combinations of the following terms: “androgenetic alopecia,” “FAGA,” “female pattern hair loss,” “platelet-rich fibrin,” “platelet-rich plasma,” and “PRP”. Results and conclusions: Eight (n = 8) clinical studies consistent with our research were identified. A total of 197 subjects has been enrolled in the included studies. All of them were adult female patients (mean age: 38.9) affected by female pattern hair loss. PRP is a well-tolerated procedure which showed promising results in males-only and mixed populations of AGA patients. PRP showed to produce high levels of satisfaction and improvement in the quality of life in patients affected by FAGA. In the light of this evidence, PRP may be proposed in patients who did not respond or did not tolerate topical minoxidil, as well as in combination with topical and oral treatments.

Wnt10b promotes hair follicles growth and dermal papilla cells proliferation via Wnt/β-Catenin signaling pathway in Rex rabbits

Wnt signaling plays an important role in the growth and development of hair follicles (HFs). Among the signaling molecules, Wnt10b was shown to promote the differentiation of primary skin epithelial cells toward the hair shaft and inner root sheath of the HF cells in mice in vitro. Whisker HFs were isolated from Rex rabbits and cultured in vitro to measure hair shaft growth. Meanwhile, dermal papilla cells (DPCs) were isolated and cultured in vitro. Treatment with AdWnt10b or the Wnt/β-Catenin Pathway inhibitor, XAV939, assessed the DPCs proliferation by CCK-8 assay. And the cell cycle was also analyzed by flow cytometry. We found that Wnt10b could promote elongation of the hair shaft, whereas XAV-939 treatment could eliminated this phenomenon. AdWnt10b treatment promoted the proliferation and induced G1/S transition of DPCs. AdWnt10b stimulation up-regulated β-Catenin protein in DPCs. Inhibition of Wnt/β-Catenin signaling by XAV-939 could decreased the basal and Wnt10b-enhanced proliferation of DPCs. And could also suppress the cell cycle progression in DPCs. In summary, our study demonstrates that Wnt10b could promote HFs growth and proliferation of DPCs via the Wnt/β-Catenin signaling pathway in Rex rabbits.

Stress-associated ectopic differentiation of melanocyte stem cells and ORS amelanotic melanocytes in an ex vivo human hair follicle model

Hair greying depends on the altered presence and functionality of hair follicle melanocytes. Melanocyte stem cells (MelSCs) reside in the bulge of hair follicles and give rise to migrating and differentiating progeny during the anagen phase. Ageing, genotoxic stress, redox stress and multiple behaviour-associated acute stressors have been seen to induce hair greying by depleting the MelSC pool, a phenomenon which is accompanied by ectopic pigmentation of these cells, followed by their depletion from the stem cell niche. This aberrant differentiation produces a state from which a return to stem cell-like quiescence appears to be lost. The cellular features of stress-induced hair greying have been extensively studied in murine models. Here, we describe a method to assess and quantify human hair follicle MelSC differentiation by measuring ectopically pigmented MelSCs in isolated human hair follicles exposed to specific stress signal mediators. Ionizing radiation, hydrogen peroxide and noradrenaline have been shown to cause hair greying in mice. We demonstrate here that isolated, ex vivo cultured human hair follicles exposed to these treatments display similar ectopic pigmentation within the bulge area which is accompanied by induction of differentiated melanocytic markers. This study suggests that as in murine models, stress signalling induces closely matching phenotypic changes in human hair follicles which can be monitored and studied as a surrogate model for early steps in human hair greying.

Hair Follicle Transplantation for Wound Repair

Significance: Hair follicles are complex miniorgans that reside in the dermal layer of the skin. When the skin is wounded, epidermal stem cells in the hair follicle activate and start migrating into the wound site, differentiating into epidermal cells. and contributing to the reepithelialization of the wound. The hair follicles represent the deepest epidermal elements in the skin, which are extremely beneficial in partial-thickness burns and abrasions where the skin can regenerate from the hair follicles. Recent Advances: Advanced animal models have demonstrated that the contribution of epidermal stem cells in the hair follicle bulge and isthmus regions is important for wound healing. In addition, several clinical studies have shown successful harvesting and transplantation of hair follicles as a treatment modality to accelerate wound healing. Critical Issues: Deep and large wounds require hospitalization and, without exception, surgical treatment. Harvesting and direct transplantation of hair follicles could provide a great source of autologous epidermal stem cells for wound healing. The procedure can be done in an outpatient setting, quickly and without creating a large donor site wound. Future Directions: Transplantation of hair follicles in a combination with novel biomaterials could provide advantageous treatment possibilities for both chronic wounds and burns. There is a substantial amount of molecular signaling data available on the role of hair follicles during wound repair, but almost all the data are derived from rodent models, and thus, more information from large animals and most importantly from humans would be beneficial and help to advance this promising treatment further.

Rabbits - their domestication and molecular genetics of hair coat development and quality

The European rabbit (Oryctolagus cuniculus) is the only representative of its genus living in present-day Europe and North Africa, and all domestic rabbits are descendants of this one species, which is native to the Iberian Peninsula. There are over 300 breeds of rabbits that differ in size, coat color, length of ears and type of fur. Rabbits are bred for various reasons, such as for laboratory animals and a source of meat, wool and fur, as well as for pets and exhibition animals. The hair coat is a important economic trait of rabbits. Its development and quality are influenced by various factors, both environmental and genetic. The genetic mechanisms underlying its development have not been thoroughly researched. The aim of this review is to discuss the domestication of rabbits and the different aspects of rabbit genetics. A brief review of the properties of rabbit hair coat, hair coat development and hair cycle will be provided, followed by discussion of the factors regulating hair coat development, molecular control of hair coat development and the role of non-coding RNAs in the regulation of gene expression in the hair follicles of rabbits. Information about genetic regulation of pathways could provide useful tools for improving hair coat quality and be of practical use in rabbit breeding.

Mammalian-specific ectodermal enhancers control the expression of Hoxc genes in developing nails and hair follicles

Vertebrate Hox genes are critical for the establishment of structures during the development of the main body axis. Subsequently, they play important roles either in organizing secondary axial structures such as the appendages, or during homeostasis in postnatal stages and adulthood. Here, we set up to analyze their elusive function in the ectodermal compartment, using the mouse limb bud as a model. We report that the HoxC gene cluster was co-opted to be transcribed in the distal limb ectoderm, where it is activated following the rule of temporal colinearity. These ectodermal cells subsequently produce various keratinized organs such as nails or claws. Accordingly, deletion of the HoxC cluster led to mice lacking nails (anonychia), a condition stronger than the previously reported loss of function of Hoxc13, which is the causative gene of the ectodermal dysplasia 9 (ECTD9) in human patients. We further identified two mammalian-specific ectodermal enhancers located upstream of the HoxC gene cluster, which together regulate Hoxc gene expression in the hair and nail ectodermal organs. Deletion of these regulatory elements alone or in combination revealed a strong quantitative component in the regulation of Hoxc genes in the ectoderm, suggesting that these two enhancers may have evolved along with the mammalian taxon to provide the level of HOXC proteins necessary for the full development of hair and nail.

Histological and Immunohistochemical Features of Trichoblastoma in a Sarda Breed Sheep

Simple Summary

Skin tumors in ruminants are occasionally reported and are mostly associated with the presence of oncogenic viruses, such as papillomavirus, or to direct skin exposure to solar radiation. Spontaneous tumors with adnexal differentiation, originating from the hair follicle or its associated glands, are even more rarely reported in these species. Investigation of the histological and immunohistochemical features of a trichoblastoma (tumor arising from the hair follicle) detected in the ear of a Sarda breed sheep, allowed for the study of comparative aspects of this tumor with other domestic species in which this neoplasm is commonly reported, such as in dogs and cats, and in human beings. This work contributed to the deepening of the knowledge of ovine spontaneous tumors unrelated to the presence of papillomaviruses.

Abstract

Skin tumors with adnexal differentiation are commonly reported in dogs and cats, while only anecdotal evidence is available in sheep. Here we illustrate the macroscopic, histologic, and immunohistochemical features of a cutaneous lesion with adnexal differentiation in a 6-year-old female Sarda breed sheep, surgically treated for a horn-like mass located in the left pinna. Additionally, we investigate a possible contribution of Ovine Papillomaviruses (OaPVs). Histologically, the dermis was expanded by an expansive and unencapsulated multilobulated nodule composed of cuboidal to spindle basaloid cells arranged in variably-sized cytokeratins (CK) AE1-AE3, CK 5/6 and CK 34 beta E12, p63—positive winding cords with a characteristic palisade arrangement of neoplastic cells in the periphery of the tumor. Based on these results, the cutaneous neoplasm was diagnosed as a trabecular trichoblastoma with spindle cells and rare structures resembling papillary mesenchymal bodies. Additionally, multiple enlarged sebaceous lobules clustered around dilated ducts suggestive of sebaceous gland hyperplasia were detected near the trichoblastoma. No PV DNA was found in the examined tissues, suggesting that ovine PVs are not involved in the pathogenesis of the present skin tumors with adnexal differentiation. Further investigations and efforts are required to elucidate the prevalence of skin tumors with adnexal differentiation in this species.

Clinical Study to Evaluate the Efficacy and Safety of a Hair Serum Product in Healthy Adult Male and Female Volunteers with Hair Fall

Background

Hair fall is a widespread problem among all genders, ages, and ethnicity with both physical and psychological effects.

Objective

This clinical study was designed to evaluate the efficacy and safety of a hair serum formulation containing amla extract, freeze-dried coconut water, and the micronutrient selenium along with sandalwood odorant and peanut shell extract in healthy male and female volunteers with hair fall.

Methods

A total of 42 subjects were enrolled and completed the study and they used the test product daily for 90 days. TrichoScan^® was used to evaluate the efficacy of the test product for improving hair growth rate, hair density, anagen hair, telogen hair, and the density of vellus and terminal hair. Hair thinning and hair fall reduction were compared to its basline by both dermatologists and subject self-assessment questionnaires.

Result and Discussion

After 90 days of test product application, there was a significant improvement in hair growth rate (<0.0001), hair density (<0.0001), vellus hair density (<0.0001), and terminal hair density (<0.0001) in comparison to baseline. There was a significant reduction in hair fall with bulb (<0.0001) and without bulb (<0.0001), and hair thinning (<0.0001) compared to the baseline measurement. Adverse events were not recorded during the study. No skin intolerance was reported during the study, and the test product was considered dermatologically safe to use.

Photoacoustic Imaging as a Tool for Assessing Hair Follicular Organization

Follicular unit extraction (FUE) and follicular unit transplantation (FUT) account for 99% of hair transplant procedures. In both cases, it is important for clinicians to characterize follicle density for treatment planning and evaluation. The existing gold-standard is photographic examination. However, this approach is insensitive to subdermal hair and cannot identify follicle orientation. Here, we introduce a fast and non-invasive imaging technique to measure follicle density and angles across regions of varying density. We first showed that hair is a significant source of photoacoustic signal. We then selected regions of low, medium, and high follicle density and showed that photoacoustic imaging can measure the density of follicles even when they are not visible by eye. We performed handheld imaging by sweeping the transducer across the imaging area to generate 3D images via maximum intensity projection. Background signal from the dermis was removed using a skin tracing method. Measurement of follicle density using photoacoustic imaging was highly correlated with photographic determination (R² = 0.96). Finally, we measured subdermal follicular angles-a key parameter influencing transection rates in FUE.

The first comprehensive classification of hair transection: A step forward

There has been an increase in the hair transplant surgeries especially FUE all over the world during last two decades. The more the number of grafts being harvested result in increase in transection. Unfortunately, there is no classification dealing with the hair transection. The authors have proposed the first comprehensive classification for document different levels of hair transections.

Plasma Zinc Levels in Males with Androgenetic Alopecia as Possible Predictors of the Subsequent Conservative Therapy's Effectiveness

Androgenic alopecia (AGA) is the most common type of progressive hair loss in man. The search for reliable predictors of the conservative treatment’s effectiveness is an urgent problem today. Forty-eight patients with AGA, stages I–IV by the Norwood–Hamilton scale, were treated for 4 months with 5% topical minoxidil joints with corrections for trace element and vitamin imbalances. In most cases, the positive therapy’s effect was shown in the parietal but not in the occipital area, whereas that effect was observed in others. The attempts to associate the therapy’s effectiveness with initially defined genetic, hormonal, and metabolic parameters showed the absence of differences between groups with positive and negative outcomes. Among the studied nutrient parameters (Zn, Cu, Mg, Ca, Fe, and Se, as well as vitamins B12, E, D, and folic acid), differences between these groups was shown in zinc content only. The starting point from a zinc plasma level above 10 µmol/L likely provides the success of the subsequent conservative therapy and correlates with an increase in the hair density and diameter in the parietal area. The integral predictive value of the Zn plasma level was assessed as 72.3% (positive predictive value: −88%; and negative predictive value: −55%).

Molecular Analysis of the ABCA4 Gene Mutations in Patients with Stargardt Disease Using Human Hair Follicles

ABCA4 gene mutations are the cause of a spectrum of ABCA4 retinopathies, and the most common juvenile macular degeneration is called Stargardt disease. ABCA4 has previously been observed almost exclusively in the retina. Therefore, studying the functional consequences of ABCA4 variants has required advanced molecular analysis techniques. The aim of the present study was to evaluate whether human hair follicles may be used for molecular analysis of the ABCA4 gene splice-site variants in patients with ABCA4 retinopathies. We assessed ABCA4 expression in hair follicles and skin at mRNA and protein levels by means of real-time PCR and Western blot analyses, respectively. We performed cDNA sequencing to reveal the presence of full-length ABCA4 transcripts and analyzed ABCA4 transcripts from three patients with Stargardt disease carrying different splice-site ABCA4 variants: c.5312+1G>A, c.5312+2T>G and c.5836-3C>A. cDNA analysis revealed that c.5312+1G>A, c.5312+2T>G variants led to the skipping of exon 37, and the c.5836-3C>A variant resulted in the insertion of 30 nucleotides into the transcript. Our results strongly argue for the use of hair follicles as a model for the molecular analysis of the pathogenicity of ABCA4 variants in patients with ABCA4 retinopathies.

High Flexible and Broad Antibacterial Nanodressing Induces Complete Skin Repair with Angiogenic and Follicle Regeneration

Complete skin reconstruction is a hierarchically physiological assembly involving epidermis, dermis, vasculature, innervation, hair follicles, and sweat glands. Despite various wound dressings having been developed for skin regeneration, few works refer to the complete skin regeneration, particularly lacking for vasculatures and hair follicles. Herein, an instructive wound dressing that integrates the antibacterial property of quaternized chitin and the mechanical strength and biological multifunction of silk fibroin through layer-by-layer electrostatic self-assembly is designed and reported. The resultant dressings exhibit a nanofibrous structure ranging from 471.5 ± 212.1 to 756.9 ± 241.8 nm, suitable flexibility with tensile strength up to 4.47 ± 0.29 MPa, and broad-spectrum antibacterial activity against Escherichia coli and Staphylococcus aureus. More interestingly, the current dressing system remarkably accelerates in vivo vascular reconstruction within 15 days, and the number of regenerated hair follicles reaches up to 22 ± 4 mm-2 , which is comparable to the normal tissue (27 ± 2 mm-2 ). Those crucial functions might originate from the combination between quaternized chitin and silk fibroin and the hierarchical structure of electrospun nanofiber. This work establishes an easy but effective pathway to design a multifunctional wound dressing for the complete skin regeneration.

A Novel Effect of Acyclovir on Hair Growth in BALB/c Mice: A Promising Future for Finding a New Topical Drug for the Treatment of Hirsutism

PURPOSE

Hirsutism (ie, terminal hair growth on the face and body in a male-like pattern in women) is a common dermatological disorder in women, with psychosocial implications. Consequently, there is demand for finding novel pharmacological treatments and agents that can safely reduce hair growth. This study aimed to investigate the potential effect of topical acyclovir on hair growth in mice.

METHODS

In this study, twenty-four female BALB/c mice were randomly divided into three groups in order to evaluate the hair growth-reducing effects of acyclovir (control group, vehicle group, and acyclovir group). Topical acyclovir 5% was applied on the shaved denuded skin of mice. Topical application onto the backs of the animals was performed twice daily for 28 consecutive days. The time (in days) required for hair growth initiation as well as completion of hair growth in dorsal skin of animals were recorded. On day 28, horizontally cut biopsy samples were removed and the numbers of hair follicles were counted, and the diameter of hair follicles was measured under high-field microscopy by a specialist blinded to the treatments.

RESULTS

Hair growth initiation time was significantly increased with acyclovir, as compared to control and vehicle groups. The time required for complete hair growth in control and vehicle groups were 18±0.68 and 19±1.41 days, respectively; however, the hair growth completion in acyclovir-treated animals was not observed at the end of the experiment. Furthermore, the length of hairs in treatment group was significantly shorter than the control group at the end of the study (P < 0.001). In histologic examination, the count and the diameter of hair follicles in deep subcutis were significantly decreased.

CONCLUSION

The results of this study, for the first time, showed that topical administration of acyclovir might have inhibitory effects on hair growth in experimental animals; however, further studies are required to understand its mechanism.

Hypertrichotic patches as a mosaic manifestation of Proteus syndrome

BACKGROUND

Proteus syndrome is an overgrowth disorder caused by a mosaic activating AKT1 variant. Hair abnormalities in Proteus syndrome have rarely been reported, and frequencies of such findings have not been elucidated.

OBJECTIVE

To define the types and frequencies of hair findings in individuals with Proteus syndrome.

METHODS

A cross-sectional study was conducted of individuals with clinical features of Proteus syndrome and a confirmed pathogenic variant in AKT1 evaluated between November 1996 and June 2019 at the National Institutes of Health Clinical Center. Medical records were reviewed for patterning, density, and color of hair on the body and scalp.

RESULTS

Of 45 individuals evaluated, 29 (64%) had asymmetric hypertrichosis on the body. This included unilateral blaschkoid hypertrichotic patches overlying normal skin or epidermal nevi in 16 (36%), unilateral nonblaschkoid hypertrichotic patches in 11 (24%), and unilateral limb hypertrichosis in 10 (22%). Diffuse, scattered, or patchy changes in scalp hair density or color were present in 11 individuals (24%).

LIMITATIONS

The retrospective, observational design, and limited longitudinal follow-up.

CONCLUSIONS

Asymmetric variations in hair distribution, thickness, length, and color contribute to the overall mosaic appearance of the skin in Proteus syndrome, an observation that provides novel insights into the role of phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling in skin appendage development.

The skin structures and their role in the thermoregulation of the South American fur seal (Arctocephalus australis)

The skin of the South American fur seal (Arctocephalus australis) is important for animal thermoregulation in both terrestrial and aquatic environments. Skin tissue samples were collected from A. australis for microscopic analysis and were related to anatomical references. The aim of this study was to describe the skin morphology, as well as to suggest the major anatomical regions and skin components involved in the thermoregulation of this species. Using light microscopy, the skin of six animals was examined based on histological, morphometric, and immunohistochemical criteria. Hair follicle morphology was examined using scanning electron microscopy. The skin was classified as either thick or thin based on its epidermal thickness. The thin epidermis regions had more abundant hair follicles, as well as high pigmentation, whereas the thick epidermis regions had very pigmented epidermal layers. Pigmentation of hair and skin is fundamental for protection against ultraviolet rays; moreover, hair is important in preventing abrasion, and provides an insulating layer against the external environment, which can be much colder than body temperature. Furthermore, the dermis is well vascularized, especially the superficial dermis. All regions of the skin have adaptations for maintaining the animal's condition in both terrestrial and aquatic environments. Among the studied regions, the interdigital region from hindflipper showed important morphological characteristics related to thermoregulation, such as having an epidermis of intermediate thickness, a dermis with a small number of hairs, a large amount of blood vessels, and sweat glands with large lumens, indicating that heat exchange in this region may be faster.