Bald scalp in men with androgenetic alopecia retains hair follicle stem cells but lacks CD200-rich and CD34-positive hair follicle progenitor cells

The value of immunohistochemical expression of SOX9 and CD34 in alopecia areata

BACKGROUND

Alopecia areata (AA), an immune-mediated disorder, is marked by temporary, nonscarring hair loss. The bulge area is protected from immune attacks by immune privilege; however, recent studies demonstrated immune cells infiltrating the bulge area.

OBJECTIVE

This study aims to investigate the immunohistochemical expression of the sex-determining region Y-box 9 (SOX9) and cluster of differentiation 34 (CD34) in AA patients as markers of hair follicle stem cells (HFSCs) and progenitor cells, respectively.

METHODS

Immunohistochemical staining of SOX9 and CD34 was applied on skin samples of 20 AA patients and 20 healthy controls.

RESULTS

SOX9 and CD34 were significantly lower in lesional samples of cases compared to perilesional and control skin biopsies. Furthermore, SOX9 level was negatively correlated with the severity of alopecia tool score (SALT score) among the studied AA patients. Moreover, lowered SOX9 expression was present in patients with recurrent attacks.

CONCLUSIONS

The significant reduction of stem cell markers (SOX9 and CD34) in our studied AA cases signifies the pathological affection of HFSCs and their progeny in AA. This is thought to cause a loss of competence in generating new hair in some AA cases, which needs to be validated in further research.

LIMITATIONS OF THE STUDY

This study has a small sample size.

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

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

The Effectiveness of Low-Level Light/Laser Therapy on Hair Loss

Background: A systematic review on low-level light/laser therapy (LLLT) in male pattern hair loss (MPHL) and female pattern hair loss (FPHL) has been performed. Objectives: Compare the reported effectiveness of LLLT in MPHL and FPHL with any control, through randomized controlled trials (RCTs) analysis. Methods: The protocol was developed in accordance with the Preferred Reporting for Items for Systematic Reviews and Meta-Analyses-Protocols guidelines. A multistep search of the PubMed, MEDLINE, Embase, PreMEDLINE, Ebase, Clinicaltrials.gov, Scopus database, and Cochrane databases has been performed to identify articles on MPHL and/or FPHL treatment with LLLT. Results: Of the 298 articles initially identified, 136 articles focusing on MPHL and FPHL were selected and, consequently, only 36 articles focused exclusively on LLLT. Of this amount, 23 articles were clinical trials while 13 articles were systematic reviews. Systematic reviews were excluded, and only seven articles were analyzed as RCTs. Conclusions: All the articles selected and analyzed reported a positive effect of LLLT for MPHL and/or FPHL treatment without side effects.

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

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

Autologous Stem Cell-derived Therapies for Androgenetic Alopecia: A Systematic Review of Randomized Control Trials on Efficacy, Safety, and Outcomes

Background

Androgenic alopecia (AGA), a prevalent and extensively studied condition characterized by hair loss, presents a significant global issue for both men and women. Stem cell therapy has emerged as a promising therapeutic approach for AGA due to its regenerative and immunomodulatory properties. The primary objective of this systematic review was to assess the current literature on the efficacy and safety of cellular and acellular stem cell-derived therapies in the management of AGA.

Methods

A computerized literature search was conducted in ClinicalTrials.gov, PubMed, and Cochrane Library in October 2023. The online screening process was performed by three independent reviewers with the Covidence tool. The protocol was reported using the Preferred Reporting Items for Systematic Review and Meta-Analyses, and it was registered at the International Prospective Register of Systematic Reviews of the National Institute for Health Research.

Results

The search yielded 53 articles from 2013 to 2023. Twelve randomized controlled trials were included. Stem cells and their derivatives were isolated from human adipose tissue, hair follicles, bone marrow, umbilical cord blood, and exfoliated deciduous teeth. These trials showed that stem cell-derived treatments can promote hair regeneration and density.

Conclusions

Both cellular and acellular stem cell-based therapies are safe and effective in improving hair regeneration and density in AGA patients. Although the outcomes may be temporary in some cases, regenerative treatments may become useful adjuncts in combination with traditional methods of hair transplantation. Future research should focus on protocol optimization to enhance long-term patient outcomes.

Autophagy induces hair follicle stem cell activation and hair follicle regeneration by regulating glycolysis

BACKGROUND

Hair follicle stem cells (HFSCs) typically remain quiescent and are activated only during the transition from telogen to anagen to ensure that the hair follicle enters a new cycle. The metabolic behavior of stem cells in tissues is regulated by macroautophagy/autophagy, and changes in HFSC metabolism directly affect their activation and maintenance. However, the role of autophagy in the regulation of HFSC metabolism and function remains unclear.

METHODS

Back skin samples were obtained from mice at different hair follicle cycle stages, and immunofluorescence staining was used to monitor autophagy in HFSCs. Mouse and human hair follicles were treated with rapamycin (Rapa, an autophagy activator) or 3-methyladenine (3-MA, an autophagy inhibitor). The effects of autophagy on the hair follicle cycle and HFSC were investigated by imaging, cell proliferation staining, and HFSC-specific marker staining. The influence and mechanism of autophagy on HFSC metabolism were explored using RNA sequencing, real-time polymerase chain reaction, immunohistochemical staining, and detection of lactate and glucose concentrations. Finally, the influence of autophagy-induced glycolysis on HFSC and the hair follicle cycle was verified by stem cell characteristics and in vivo functional experiments.

RESULTS

Autophagy in HFSC was highest during the transition from telogen to anagen. Inhibiting autophagy with 3-MA led to early entry into catagen and prolonged telogen, whereas Rapa promoted autophagy and hair growth. Autophagy activated HFSC by increasing the expression and activity of HFSC lactate dehydrogenase (Ldha), thereby transforming HFSC metabolism into glycolysis. Inhibition of Ldha expression counteracted the effects of autophagy.

CONCLUSIONS

Autophagy activated HFSC by promoting the transition from HFSC metabolism to glycolysis, ultimately initiating the hair follicle cycle and promoting hair growth.

Systematic review: Impact of stem cells-based therapy, and platelet-rich plasma in hair loss and telogen effluvium related to COVID-19

Background

The incidence of hair loss (HL) and telogen effluvium (TE) in COVID-19 patients has been reported in several studies.

Objectives

Evaluate both the increased incidence of HL and TE in COVID-19 and the effectiveness of Platelet-Rich Plasma (PRP), Adipose-derived Mesenchymal Stem Cells (AD-MSCs), and Human Follicle Stem Cells (HFSCs) in these patients.

Methods

The protocol was developed by the Preferred Reporting for Items for Systematic Reviews and Meta-Analyses-Protocols (PRISMA-P) guidelines. A multistep search of PubMed, MEDLINE, Embase, Clinicaltrials. gov, Scopus, and Cochrane databases has been performed to identify papers focusing on HL and TE COVID-19 related, and papers focusing on AD-MSCs, HFSC, and PRP use.

Results

Of the 404 articles initially identified focusing on HL and TE, 44 were related to COVID-19, and finally, only 6 were analyzed. On the other way, 331 articles focusing on AD-MSCs, HFSC, and PRP were initially identified. Of these, only 6 articles PRP (n = 3), AD-MSCs, and HFSCs (n = 3) have been analyzed.

Conclusion

Collected data confirmed both an increased incidence of HL and TE in COVID-19 patients, preliminarily, the related effectiveness of AD-MSCs, HFSCs, and PRP without major side effects.

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

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

Adipose-Derived Stem Cell Exosomes Antagonize the Inhibitory Effect of Dihydrotestosterone on Hair Follicle Growth by Activating Wnt/β-Catenin Pathway

The most prevalent type of alopecia is androgenetic alopecia (AGA), which has a high prevalence but no effective treatment. Elevated dihydrotestosterone (DHT) level in the balding area was usually thought to be critical in the pathophysiology of AGA. The canonical Wnt/β-catenin signaling pathway plays a key role in promoting hair follicle development and sustaining the hair follicle cycle. Adipose-derived stem cell exosomes (ADSC-Exos) are widely used in the field of regenerative medicine due to the advantages of being cell free and immune privileged. Still, few studies have reported the therapeutic effect on hair disorders. As a result, we sought to understand how ADSC-Exos affected hair growth and explore the possibility that ADSC-Exos could counteract the hair-growth-inhibiting effects of DHT. This research using human hair follicle organs, in vitro dermal papilla cells, and in vivo animal models showed that ADSC-Exos not only encouraged healthy hair growth but also counteracted the inhibitory effects of DHT on hair growth. Additionally, we discovered that ADSC-Exos increased Ser9 phosphorylated glycogen synthase kinase-3β levels and facilitated nuclear translocation of β-catenin, which may have been blocked by the specific Wnt/β-catenin signaling pathway inhibitor dickkopf-related protein 1. Our findings suggested that ADSC-Exos are essential for hair regeneration, which is anticipated to open up new therapeutic possibilities for clinical alopecia, particularly for the treatment of AGA.

Multi-omics segregate different transcriptomic impacts of anti-IL-17A blockade on type 17 T-cells and regulatory immune cells in psoriasis skin

Durable psoriasis improvement has been reported in a subset of psoriasis patients after treatment withdrawal of biologics blocking IL-23/Type 17 T-cell (T17) autoimmune axis. However, it is not well understood if systemic blockade of the IL-23/T17 axis promotes immune tolerance in psoriasis skin. The purpose of the study was to find translational evidence that systemic IL-17A blockade promotes regulatory transcriptome modification in human psoriasis skin immune cell subsets. We analyzed human psoriasis lesional skin 6 mm punch biopsy tissues before and after systemic IL-17A blockade using the muti-genomics approach integrating immune cell-enriched scRNA-seq (n = 18), microarray (n = 61), and immunohistochemistry (n = 61) with repository normal control skin immune cell-enriched scRNA-seq (n = 10) and microarray (n = 8) data. For the T17 axis transcriptome, systemic IL-17A blockade depleted 100% of IL17A + T-cells and 95% of IL17F + T-cells in psoriasis skin. The expression of IL23A in DC subsets was also downregulated by IL-17A blockade. The expression of IL-17-driven inflammatory mediators (IL36G, S100A8, DEFB4A, and DEFB4B) in suprabasal keratinocytes was correlated with psoriasis severity and was downregulated by IL-17A blockade. For the regulatory DC transcriptome, the proportion of regulatory semimature DCs expressing regulatory DC markers of BDCA-3 (THBD) and DCIR (CLEC4A) was increased in posttreatment psoriasis lesional skin compared to pretreatment psoriasis lesional skin. In addition, IL-17A blockade induced higher expression of CD1C and CD14, which are markers of CD1c+ CD14+ dendritic cell (DC) subset that suppresses antigen-specific T-cell responses, in posttreatment regulatory semimature DCs compared to pretreatment regulatory semimature DCs. In conclusion, systemic IL-17A inhibition not only blocks the entire IL-23/T17 cell axis but also promotes regulatory gene expression in regulatory DCs in human psoriasis skin.

Topical Finasteride: A Comprehensive Review of Androgenetic Alopecia Management for Men and Women

The most prevalent kind of alopecia, androgenetic alopecia, commonly known as male or female pattern hair loss, affects both men and women, with the frequency rising with advancing years. Even though practicing dermatologists and hair experts frequently encounter it, it might be one of the most challenging disorders to treat since choosing a course of action frequently requires a comprehensive analysis of several variables and moral judgment. Effectiveness, side effect profiles, practicability, promoting compliance, and treatment cost are the most important factors to take into account, especially given the chronic nature of androgenetic alopecia. A clinician's ability to select the optimum course of treatment for each patient may be constrained and clouded by their knowledge base, experience, and financial compensation. A search was done to find research on the effectiveness of topical finasteride therapy, including clinically pertinent case reports and papers. Only topical minoxidil and oral finasteride are now approved by the Food and Drug Administration and the European Medicines Agency for the treatment of androgenetic alopecia. Despite being effective for hair regeneration, systemic use of finasteride is accompanied by adverse effects that prevent long-term use. Investigating topical finasteride as another possible treatment plan may be fruitful. Early research on the use of topical finasteride is safe and encouraging, despite its limitations. More research on drug distribution, ideal topical strength and usage regularity, adverse effects, and application for other alopecias would aid in elucidating the range of topical finasteride use.

3D multicellular micropatterning biomaterials for hair regeneration and vascularization

Hair loss caused by the abnormal functions of hair follicles in skin can seriously impact the quality of an individual's life. The development of sophisticated skin tissue-engineered constructs is required to enable the function recovery of hair follicles. However, effective hair regrowth in skin substitutes still remains a great challenge. In this study, a 3D multicellular micropattern was successfully fabricated by arranging the hair follicle-related cells orderly distributed in the interval of vascular-cell networks via bioprinting technology. By combining the stable biomimetic micropattern structure and the bio-inducing substrate incorporated with magnesium silicate (MS) nanomaterials, the 3D multicellular micropattern possessed significant follicular potential and angiogenic capacity in vitro. Furthermore, the 3D multicellular micropattern with MS incorporation contributed to efficient hair regrowth during skin tissue regeneration in both immunodeficient mice and androgenetic alopecia (AGA) mice models. Thus, this study proposes a novel 3D micropatterned multicellular system assembling a biomimetic micro-structure and modulating the cell-cell interaction for hair regeneration during skin reconstruction.

Integrated single-cell chromatin and transcriptomic analyses of human scalp identify gene-regulatory programs and critical cell types for hair and skin diseases

Genome-wide association studies have identified many loci associated with hair and skin disease, but identification of causal variants requires deciphering of gene-regulatory networks in relevant cell types. We generated matched single-cell chromatin profiles and transcriptomes from scalp tissue from healthy controls and patients with alopecia areata, identifying diverse cell types of the hair follicle niche. By interrogating these datasets at multiple levels of cellular resolution, we infer 50-100% more enhancer-gene links than previous approaches and show that aggregate enhancer accessibility for highly regulated genes predicts expression. We use these gene-regulatory maps to prioritize cell types, genes and causal variants implicated in the pathobiology of androgenetic alopecia (AGA), eczema and other complex traits. AGA genome-wide association studies signals are enriched in dermal papilla regulatory regions, supporting the role of these cells as drivers of AGA pathogenesis. Finally, we train machine learning models to nominate single-nucleotide polymorphisms that affect gene expression through disruption of transcription factor binding, predicting candidate functional single-nucleotide polymorphism for AGA and eczema.

Male pattern hair loss: Can developmental origins explain the pattern?

Male pattern hair loss (MPHL), also referred to as male androgenetic alopecia (AGA) is the most common type of non-scarring progressive hair loss, with 80% of men suffering from this condition in their lifetime. In MPHL, the hair line recedes to a specific part of the scalp which cannot be accurately predicted. Hair is lost from the front, vertex, and the crown, yet temporal and occipital follicles remain. The visual effect of hair loss is due to hair follicle miniaturisation, where terminal hair follicles become dimensionally smaller. Miniaturisation is also characterised by a shortening of the growth phase of the hair cycle (anagen), and a prolongation of the dormant phase (kenogen). Together, these changes result in the production of thinner and shorter hair fibres, referred to as miniaturised or vellus hairs. It remains unclear why miniaturisation occurs in this specific pattern, with frontal follicles being susceptible while occipital follicles remain in a terminal state. One main factor we believe to be at play, which will be discussed in this viewpoint, is the developmental origin of the skin and hair follicle dermis on different regions of the scalp.

New insights into inflammatory memory of epidermal stem cells

Inflammatory memory, as one form of innate immune memory, has a wide range of manifestations, and its occurrence is related to cell epigenetic modification or metabolic transformation. When re-encountering similar stimuli, executing cells with inflammatory memory function show enhanced or tolerated inflammatory response. Studies have identified that not only hematopoietic stem cells and fibroblasts have immune memory effects, but also stem cells from various barrier epithelial tissues generate and maintain inflammatory memory. Epidermal stem cells, especially hair follicle stem cells, play an essential role in wound healing, immune-related skin diseases, and skin cancer development. In recent years, it has been found that epidermal stem cells from hair follicle can remember the inflammatory response and implement a more rapid response to subsequent stimuli. This review updates the advances of inflammatory memory and focuses on its mechanisms in epidermal stem cells. We are finally looking forward to further research on inflammatory memory, which will allow for the development of precise strategies to manipulate host responses to infection, injury, and inflammatory skin disease.

Innovative Approaches and Advances for Hair Follicle Regeneration

Pathological hair loss (also known as alopecia) and shortage of hair follicle (HF) donors have posed an urgent requirement for HF regeneration. With the revelation of mechanisms in tissue engineering, the proliferation of HFs in vitro has achieved more promising trust for the treatments of alopecia and other skin impairments. Theoretically, HF organoids have great potential to develop into native HFs and attachments such as sweat glands after transplantation. However, since the rich extracellular matrix (ECM) deficiency, the induction characteristics of skin-derived cells gradually fade away along with their trichogenic capacity after continuous cell passaging in vitro. Therefore, ECM-mimicking support is an essential prelude before HF transplantation is implemented. This review summarizes the status of providing various epidermal and dermal cells with a three-dimensional (3D) scaffold to support the cell homeostasis and better mimic in vivo environments for the sake of HF regeneration. HF-relevant cells including dermal papilla cells (DPCs), hair follicle stem cells (HFSCs), and mesenchymal stem cells (MSCs) are able to be induced to form HF organoids in the vitro culture system. The niche microenvironment simulated by different forms of biomaterial scaffold can offer the cells a network of ordered growth environment to alleviate inductivity loss and promote the expression of functional proteins. The scaffolds often play the role of ECM substrates and bring about epithelial-mesenchymal interaction (EMI) through coculture to ensure the functional preservation of HF cells during in vitro passage. Functional HF organoids can be formed either before or after transplantation into the dermis layer. Here, we review and emphasize the importance of 3D culture in HF regeneration in vitro. Finally, the latest progress in treatment trials and critical analysis of the properties and benefits of different emerging biomaterials for HF regeneration along with the main challenges and prospects of HF regenerative approaches are discussed.

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.

Wound-Induced Hair Neogenesis: A Portal to the Development of New Therapies for Hair Loss and Wound Regeneration

Adult mammals retain the remarkable ability to regenerate hair follicles after wounding. Wound-induced hair neogenesis (WIHN) in many ways recapitulates embryogenesis. The origin of the stem cells that give rise to a nascent hair follicle after wounding and the role of mesenchymal cells and signaling pathways responsible for this regenerative phenomenon are slowly being elucidated. WIHN provides a potential therapeutic window for manipulating cell fate by the introduction of factors during the wound healing process to enhance hair follicle formation.

Dendrobium officinale Polysaccharide (DOP) Promotes Hair Regrowth in Testosterone-Induced Bald Mice

BACKGROUND

Androgenetic alopecia can affect up to 70% of males and 40% of females; however, certain therapeutic medications offer partial and transitory improvement but with major side effects. Dendrobium officinale polysaccharide (DOP) has been reported to improve androgen-related hair loss in mice, but the molecular mechanism remains unclear.

OBJECTIVES

To explore the effects of DOP on androgenetic alopecia.

METHODS

In this study, testosterone was subcutaneously administered to shave dorsa skin of mice to establish androgenetic alopecia; the effects of DOP in androgenetic alopecia were explored by DOP administration.

RESULTS

Testosterone treatment extended the time of skin growing dark and hair growing, decreased the mean numbers of follicles in skin tissues, decreased β-catenin and cyclin D1 levels, and elevated testosterone, DHT (dihydrotestosterone), and 5α-reductase levels. In contrast, DOP administration shortened skin growing dark and hair growing times, promoted follicle cell proliferation, increased follicle numbers, increased β-catenin and cyclin D1 levels, and decreased testosterone, DHT, and 5α-reductase levels.

CONCLUSION

DOP application significantly improved testosterone-induced hair follicle miniaturization and hair loss, possibly through affecting the Wnt signaling and hair follicle stem cell functions.

NO LEVEL ASSIGNED

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Wnt/β-catenin signaling activator restores hair regeneration suppressed by diabetes mellitus

Diabetes mellitus is one of the most prevalent diseases in modern society. Many complicationssuch as hepatic cirrhosis, neuropathy, cardiac infarction, and so on are associated with diabetes. Although a relationship between diabetes and hair loss has been recently reported, the treatment of diabetic hair loss by Wnt/β-catenin activators has not been achieved yet. In this study, we found that the depilation-induced anagen phase was delayed in both db/db mice and high-fat diet (HFD) and streptozotocin (STZ)-induced diabetic mice. In diabetic mice, both hair regrowth and wound-induced hair follicle neogenesis (WIHN) were reduced because of suppression of Wnt/β-catenin signaling and decreased proliferation of hair follicle cells. We identified that KY19382, a small molecule that activates Wnt/β-catenin signaling, restored the capabilities of regrowth and WIHN in diabetic mice. The Wnt/β-catenin signaling activator also increased the length of the human hair follicle which was decreased under high glucose culture conditions. Overall, the diabetic condition reduced both hair regrowth and regeneration with suppression of the Wnt/β-catenin signaling pathway. Consequently, the usage of Wnt/β-catenin signaling activators could be a potential strategy to treat diabetes-induced alopecia patients. [BMB Reports 2022; 55(11): 559-564].

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.

Wnt/β-catenin signaling activator restores hair regeneration suppressed by diabetes mellitus

Diabetes mellitus is one of the most prevalent diseases in modern society. Many complicationssuch as hepatic cirrhosis, neuropathy, cardiac infarction, and so on are associated with diabetes. Although a relationship between diabetes and hair loss has been recently reported, the treatment of diabetic hair loss by Wnt/β-catenin activators has not been achieved yet. In this study, we found that the depilation-induced anagen phase was delayed in both db/db mice and high-fat diet (HFD) and streptozotocin (STZ)-induced diabetic mice. In diabetic mice, both hair regrowth and wound-induced hair follicle neogenesis (WIHN) were reduced because of suppression of Wnt/β-catenin signaling and decreased proliferation of hair follicle cells. We identified that KY19382, a small molecule that activates Wnt/β-catenin signaling, restored the capabilities of regrowth and WIHN in diabetic mice. The Wnt/β-catenin signaling activator also increased the length of the human hair follicle which was decreased under high glucose culture conditions. Overall, the diabetic condition reduced both hair regrowth and regeneration with suppression of the Wnt/β-catenin signaling pathway. Consequently, the usage of Wnt/β-catenin signaling activators could be a potential strategy to treat diabetes-induced alopecia patients. [BMB Reports 2022; 55(11): 559-564].

Investigation of hub genes and immune infiltration in androgenetic alopecia using bioinformatics analysis

Background

Androgenetic alopecia (AGA) is a type of non-scarring hair loss. Current drugs for AGA are accompanied by adverse reactions and a high recurrence rate. Thus, the discovery of diagnostic biomarkers and therapeutic targets for AGA remains imperatively warranted.

Methods

The GSE90594 dataset, which contained scalp skin biopsies from 14 male AGA cases and healthy volunteers, was used to identify the differentially expressed genes (DEGs). Functional enrichment analysis was subsequently performed. Next, the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database combined with the cytoHubba plugin of Cytoscape were used to obtain the key genes of AGA. Thereafter, the Cell-type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT) algorithm was performed to evaluate the relative abundance of immune cells between male AGA patients and healthy controls. The correlation between key genes and infiltrating immune cells was analyzed to obtain the significant immune-cell related genes (IRGs), then intersected with the DEGs between immortalized balding and non-balding human dermal papilla cells (DPCs) of the GSE93766 dataset as well as the DEGs obtained by the GSE90594 dataset, thus obtaining the hub genes of AGA. Finally, the hub genes were validated using GSE36169, which contained expression profiling of tissues biopsied from haired and bald scalps of five individuals with AGA.

Results

A total of 234 DEGs were obtained from the GSE90594 dataset, which were mainly enriched in the extracellular matrix (ECM)-related pathways and immune-related activities. The STRING database and ten algorithms in the cytoHubba plugin of Cytoscape disclosed 21 key DEGs. The results of the CIBERSORT algorithm revealed the relative abundances of 20 kinds of immune cells between diseased and healthy individuals, and yielded 15 IRGs involved in the pathogenesis of AGA. Next, the intersection analysis identified four hub genes of AGA, comprising COL1A2, PCOLCE, ITGAX, and LOX. The GSE36169 dataset validated the expression pattern of hub genes in the haired scalp of AGA patients.

Conclusions

We discovered that the hub genes identified are closely linked with the causative factors of AGA, which could be used as the viable diagnostic and therapeutic target in the clinical applications.

Influence of Nutrition, Food Supplements and Lifestyle in Hair Disorders

Genetic, androgenic, epigenetic, environmental, lifestyle, diet, and nutritional factors have influence over promoting or regulating inflammation, immunity, and genetic expression predisposing to hair loss. Oxidative stress is a major mediator for various mechanisms of hair loss, including the release of transforming growth factor-β ( TGF-β). Nutrients counter oxidative stress, repair cellular damage, support cellular functions, and restore hair growth. Nutrients can be synergistic or antagonistic. Covert subclinical nutritional deficiencies are common. Higher dose of nutrients does not mean higher efficiency but may reverse the benefits converting an antioxidant to become prooxidant. Nutrients do not work alone but are supported by accessory micronutrients which ensure biological utilization. Providing proper nutritional environment can neutralize free radicals and perpetuate active hair growth cycles.

The imbalance between Type 17 T-cells and regulatory immune cell subsets in psoriasis vulgaris

Psoriasis vulgaris is a common inflammatory disease affecting 7.5 million adults just in the US. Previously, psoriasis immunopathogenesis has been viewed as the imbalance between CD4⁺ T-helper 17 (Th17) cells and regulatory T-cells (Tregs). However, current paradigms are rapidly evolving as new technologies to study immune cell subsets in the skin have been advanced. For example, recently minted single-cell RNA sequencing technology has provided the opportunity to compare highly differing transcriptomes of Type 17 T-cell (T17 cell) subsets depending on IL-17A vs. IL-17F expression. The expression of regulatory cytokines in T17 cell subsets provided evidence of T-cell plasticity between T17 cells and regulatory T-cells (Tregs) in humans. In addition to Tregs, other types of regulatory cells in the skin have been elucidated, including type 1 regulatory T-cells (Tr1 cells) and regulatory dendritic cells. More recently, investigators are attempting to apply single-cell technologies to clinical trials of biologics to test if monoclonal blockade of pathogenic T-cells will induce expansion of regulatory immune cell subsets involved in skin homeostasis.

Conditioned media-integrated microneedles for hair regeneration through perifollicular angiogenesis

Androgenetic alopecia (AGA), the most prevalent type of hair loss in clinic, is induced partly by insufficient perifollicular vascularization. Here we designed a dissolvable microneedles (MNs) patch that was loaded with conditioned media (CM) derived from hypoxia-pretreated mesenchymal stem cells, which contained elevated HIF-1α. The CM-integrated MNs patch (designated as CM-MNs) can puncture the stratum corneum and deliver the pro-angiogenic factors directly into skin in a one-step and minimally invasive manner. Meanwhile, the administration of CM-MNs induced a certain mechanical stimulation on the skin, which can also promote neovascularization. With the combined effects of the pro-angiogenic factors in CM and the mechanical stimulation induced by MNs, CM-MNs successfully boosted perifollicular vascularization, and activated hair follicle stem cells, thereby inducing notably faster hair regeneration at a lower administration frequency on AGA mouse model compared with minoxidil. Furthermore, we proved that the inhibition of perifollicular angiogenesis restrained the awakening of hair follicle stem cells, elucidating the tight correlation between perifollicular angiogenesis and the activation of hair follicle stem cells. The innovative integration of CM and MNs holds great promise for clinical AGA treatment and indicates that boosting angiogenesis around hair follicles is an effective strategy against AGA.

Hair Loss and Telogen Effluvium Related to COVID-19: The Potential Implication of Adipose-Derived Mesenchymal Stem Cells and Platelet-Rich Plasma as Regenerative Strategies

The diffusion of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inducing coronavirus disease 2019 (COVID-19) has increased the incidence of several dermatological disorders, including hair loss (HL). This article aims to review the literature regarding the incidence of HL and telogen effluvium (TE) in COVID-19 patients and critically appraise the available evidence regarding the role of regenerative strategies like Platelet-Rich Plasma (PRP) and Human Follicle Stem Cells (HFSCs). A literature review regarding the correlation of HL and TE in COVID-19 patients analyzing the biomolecular pathway involved and the role of regenerative strategies was performed using PubMed, MEDLINE, Embase, PreMEDLINE, Scopus, and the Cochrane databases. Observational studies revealed an escalated incidence of pattern HL and TE in COVID-19 patients. Psychological stress, systemic inflammation, and oxidative stress are potential culprits. Proinflammatory cytokines and stress hormones negatively affect the normal metabolism of proteoglycans. Reduced anagenic expression of proteoglycans is a potential mediating mechanism that connects HL to COVID-19. Currently, only one study has been published on PRP against HL in COVID-19 patients. Further controlled trials are required to confirm PRP and HFSCs efficacy in COVID-19 patients.

Regulation and dysregulation of hair regeneration: aiming for clinical application

Hair growth and regeneration represents a remarkable example of stem cell function. Recent progress emphasizes the micro- and macro- environment that controls the regeneration process. There is a shift from a stem cell-centered view toward the various layers of regulatory mechanisms that control hair regeneration, which include local growth factors, immune and neuroendocrine signals, and dietary and environmental factors. This is better suited for clinical application in multiple forms of hair disorders: in male pattern hair loss, the stem cells are largely preserved, but androgen signaling diminishes hair growth; in alopecia areata, an immune attack is targeted toward the growing hair follicle without abrogating its regeneration capability. Genome-wide association studies further revealed the genetic bases of these disorders, although the precise pathological mechanisms of the identified loci remain largely unknown. By analyzing the dysregulation of hair regeneration under pathological conditions, we can better address the complex interactions among stem cells, the differentiated progeny, and mesenchymal components, and highlight the critical role of macroenvironment adjustment that is essential for hair growth and regeneration. The poly-genetic origin of these disorders makes the study of hair regeneration an interesting and challenging field.

LGR5 is a conserved marker of hair follicle stem cells in multiple species and is present early and throughout follicle morphogenesis

Hair follicle stem cells are key for driving growth and homeostasis of the hair follicle niche, have remarkable regenerative capacity throughout hair cycling, and display fate plasticity during cutaneous wound healing. Due to the need for a transgenic reporter, essentially all observations related to LGR5-expressing hair follicle stem cells have been generated using transgenic mice, which have significant differences in anatomy and physiology from the human. Using a transgenic pig model, a widely accepted model for human skin and human skin repair, we demonstrate that LGR5 is a marker of hair follicle stem cells across species in homeostasis and development. We also report the strong similarities and important differences in expression patterns, gene expression profiles, and developmental processes between species. This information is important for understanding the fundamental differences and similarities across species, and ultimately improving human hair follicle regeneration, cutaneous wound healing, and skin cancer treatment.

Single-cell transcriptomics reveals lineage trajectory of human scalp hair follicle and informs mechanisms of hair graying

Hair conditions, such as hair loss and graying, are prevalent human conditions. But they are often poorly controlled due to our insufficient understanding of human scalp hair follicle (hsHF) in health and disease. Here we describe a comprehensive single-cell RNA-seq (scRNA-seq) analysis on highly purified black and early-stage graying hsHFs. Based on these, a concise single-cell atlas for hsHF and its early graying changes is generated and verified using samples from multiple independent individuals. These data reveal the lineage trajectory of hsHF in unprecedented detail and uncover its multiple unexpected features not found in mouse HFs, including the presence of an innerbulge like compartment in the growing phase, lack of a discrete companion layer, and enrichment of EMT features in HF stem cells (HFSCs). Moreover, we demonstrate that besides melanocyte depletion, early-stage human hair graying is also associated with specific depletion of matrix hair progenitors but not HFSCs. The hair progenitors' depletion is accompanied by their P53 pathway activation whose pharmaceutical blockade can ameliorate hair graying in mice, enlightening a promising therapeutic avenue for this prevalent hair condition.

Clinical Use of Extracellular Vesicles in the Management of Male and Female Pattern Hair Loss: A Preliminary Retrospective IRB Safety and Efficacy Study

Background

Pattern hair loss is a common disorder in female and male subjects that may benefit from the use of cell-free XoFlo (Direct Biologics, LLC, Austin, TX) therapy.

Objectives

To assess the safety, efficacy and satisfaction of a single extracellular vesicle (EV) treatment over 6 months.

Methods

A retrospective open-label study among 22 female and 9 male subjects who demonstrated early stages of alopecia or were in remission from prior medical and surgical treatments. The amount of undiluted or diluted volumes of EV solution used was determined by extent and degree of alopecia. Global photography, SGAIS and IGAIS questionnaires, and trichoscan measurements were compared at baseline and six months in three response categories.

Results

Frequent growth responses were observed: older aged females and younger aged males, shorter history of alopecia; earlier stages of hair loss; larger and undiluted volumes of XoFlo; prior positive responses to medical and surgical treatments; and absence or control of disease factors affecting hair. The benefit of micro-needling to therapy was indeterminate. Global photography, trichoscan for density, follicle diameter, terminal: vellus ratio, and SGAIS/IGAIS satisfaction questionnaires at baseline and six months were useful in assessing clinical efficacy. No significant adverse reactions were observed.

Conclusions

Intradermal injections with varying doses of EVs were safe and effective among indicated alopecic female and male subjects. Findings suggest that the presence of positive factors, absence of conditions known to negatively affect hair growth, and administration of larger volumes of XoFlo may have a significant influence on the use of this new cell-free therapy. FDA-approved biologic, multi-centered IRB/ Investigational New Drug (IND) trials are clearly required to determine its future in the management of hair loss.

Minoxidil Nanoparticles Targeting Hair Follicles Enhance Hair Growth in C57BL/6 Mice

We previously found that 1% minoxidil (MXD) nanoparticles prepared using a bead mill method led to an increase I n hair follicle delivery and hair growth in C57BL/6 mice. In the present study, we designed a nanoparticle formulation containing 5% MXD (MXD-NPs) using the bead mill method and investigated the hair-growth effect of MXD-NPs and a commercially available MXD solution (CA-MXD). Hair growth and in vivo permeation studies were conducted using C57BL/6 mice. Moreover, we examined the MXD contents in the upper (hair bulge) and the lower hair follicle (hair bulb) and observed the hair follicle epithelial stem cells (HFSC) by immunohistochemical staining using the CD200 antibody. The mean particle size of the MXD in the MXD-NPs was 139.8 nm ± 8.9 nm. The hair-growth effect of the MXD-NPs was higher than that of CA-MXD, and the MXD content in the hair bulge of mice treated with MXD-NPs was 7.4-fold that of the mice treated with CA-MXD. In addition, the activation of HFSC was observed around the bulge in the MXD-NPs-treated mice. We showed that MXD-NPs enable the accumulation of MXD in the upper hair follicles more efficiently than CA-MXD, leading the activation of HFSC and the hair growth.

Depilatory laser miniaturizes hair by inducing bystander dermal papilla cell necrosis through thermal diffusion

OBJECTIVES

Depilatory laser targeting melanin has been widely applied for the treatment of hypertrichosis. Both selective photothermolysis and thermal diffusion have been proposed for its effect, but the exact mechanism of permanent hair reduction remains unclear. In this study, we explore the role of thermal diffusion in depilatory laser-induced permanent hair loss and determine whether nonpigmented cells are injured by thermal diffusion.

MATERIALS AND METHODS

C57BL/6 mice in anagen and telogen were treated with alexandrite laser (wavelength 755 nm, pulse duration 3 milliseconds, fluence 12 J/cm² , spot size 12 mm), respectively. Histological analysis, terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and transmission electron microscopic imaging were employed to evaluate the injury to hair follicle (HF) cells. The proliferation status of HF cells was examined by 5-bromo-2'-deoxyuridine pulse labeling. The number of HF stem cells was quantified by fluorescence-activated cell sorting. The size of the regenerated hair was determined by measuring its length and width.

RESULTS

We found that irradiating C57BL/6 mice in anagen with alexandrite laser led to hair miniaturization in the next anagen. In addition to thermal disruption of melanin-containing cells in the precortex region, we also detected necrosis of the adjacent nonpigmented dermal papilla cells due to thermal diffusion. Dermal papilla cells decreased by 24% after laser injury, while the number of bulge stem cells remained unchanged. When the laser was delivered to telogen HFs where no melanin was present adjacent to the dermal papilla, thermal necrosis and cell reduction were not detected in the dermal papilla and no hair miniaturization was observed.

CONCLUSION

Our results suggest that depilatory laser miniaturizes hair by inducing thermal necrosis of dermal papilla cells due to secondary thermal diffusion from melanin-containing precortex cells in the anagen hair bulbs.

Advancing Regenerative Cellular Therapies in Non-Scarring Alopecia

Alopecia or baldness is a common diagnosis in clinical practice. Alopecia can be scarring or non-scarring, diffuse or patchy. The most prevalent type of alopecia is non-scarring alopecia, with the majority of cases being androgenetic alopecia (AGA) or alopecia areata (AA). AGA is traditionally treated with minoxidil and finasteride, while AA is treated with immune modulators; however, both treatments have significant downsides. These drawbacks compel us to explore regenerative therapies that are relatively devoid of adverse effects. A thorough literature review was conducted to explore the existing proven and experimental regenerative treatment modalities in non-scarring alopecia. Multiple treatment options compelled us to classify them into growth factor-rich and stem cell-rich. The growth factor-rich group included platelet-rich plasma, stem cell-conditioned medium, exosomes and placental extract whereas adult stem cells (adipose-derived stem cell-nano fat and stromal vascular fraction; bone marrow stem cell and hair follicle stem cells) and perinatal stem cells (umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs), Wharton jelly-derived MSCs (WJ-MSCs), amniotic fluid-derived MSCs (AF-MSCs), and placental MSCs) were grouped into the stem cell-rich group. Because of its regenerative and proliferative capabilities, MSC lies at the heart of regenerative cellular treatment for hair restoration. A literature review revealed that both adult and perinatal MSCs are successful as a mesotherapy for hair regrowth. However, there is a lack of standardization in terms of preparation, dose, and route of administration. To better understand the source and mode of action of regenerative cellular therapies in hair restoration, we have proposed the "À La Mode Classification". In addition, available evidence-based cellular treatments for hair regrowth have been thoroughly described.

Comprehensive Analysis of LncRNA AC010789.1 Delays Androgenic Alopecia Progression by Targeting MicroRNA-21 and the Wnt/β-Catenin Signaling Pathway in Hair Follicle Stem Cells

Background: Androgen alopecia (AGA), the most common type of alopecia worldwide, has become an important medical and social issue. Accumulating evidence indicates that long noncoding RNAs (lncRNAs) play crucial roles in the progression of various human diseases, including AGA. However, the potential roles of lncRNAs in hair follicle stem cells (HFSCs) and their subsequent relevance for AGA have not been fully elucidated. The current study aimed to explore the function and molecular mechanism of the lncRNA AC010789.1 in AGA progression.

Methods: We investigated the expression levels of AC010789.1 in AGA scalp tissues compared with that in normal tissues and explored the underlying mechanisms using bioinformatics. HFSCs were then isolated from hair follicles of patients with AGA, and an AC010789.1-overexpressing HFSC line was produced and verified. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were performed to verify the molecular mechanisms involved.

Results: AC010789.1 overexpression promoted the proliferation and differentiation of HFSCs. Mechanistically, we demonstrated that AC010789.1 overexpression promotes the biological function of HFSCs by downregulating miR-21-5p and TGF-β1 expression but upregulating the Wnt/β-catenin signaling pathway.

Conclusion: These results reveal that overexpression of AC010789.1 suppresses AGA progression via downregulation of hsa-miR-21-5p and TGF-β1 and promotion of the Wnt/β-catenin signaling pathway, highlighting a potentially promising strategy for AGA treatment.

Thymic stromal lymphopoietin controls hair growth

Skin tissue regeneration after injury involves the production and integration of signals by stem cells residing in hair follicles (HFSCs). Much remains unknown about how specific wound-derived factors modulate stem cell contribution to hair growth. We demonstrate that thymic stromal lymphopoietin (TSLP) is produced in response to skin injury and during the anagen phase of the hair cycle. Intradermal injection of TSLP promoted wound-induced hair growth (WIHG), whereas neutralizing TSLP receptor (TSLPR) inhibited WIHG. Using flow cytometry and fluorescent immunostaining, we found that TSLP promoted proliferation of transit-amplifying cells. Lgr5^CreER-mediated deletion of Tslpr in HFSCs inhibited both wound-induced and exogenous TSLP-induced hair growth. Our data highlight a novel function for TSLP in regulation of hair follicle activity during homeostasis and wound healing.

Tissue Engineering and Regeneration of the Human Hair Follicle in Androgenetic Alopecia: Literature Review

Androgenetic alopecia (AGA) is an androgen-dependent process and represents the most frequent non-scarring alopecia. Treatments for AGA do not always achieve a satisfactory result for the patient, and sometimes cause side effects that lead to discontinuation of treatment. AGA therapeutics currently includes topical and oral drugs, as well as follicular unit micro-transplantation techniques. Tissue engineering (TE) is postulated as one of the possible future solutions to the problem and aims to develop fully functional hair follicles that maintain their cyclic rhythm in a physiological manner. However, despite its great potential, reconstitution of fully functional hair follicles is still a challenge to overcome and the knowledge gained of the key processes in hair follicle morphogenesis and biology has not yet been translated into effective replacement therapies in clinical practice. To achieve this, it is necessary to research and develop new approaches, techniques and biomaterials. In this review, present and emerging hair follicle bioengineering strategies are evaluated. The current problems of these bioengineering techniques are discussed, as well as the advantages and disadvantages, and the future prospects for the field of TE and successful hair follicle regeneration.

Androgen receptor-mediated paracrine signaling induces regression of blood vessels in the dermal papilla in androgenetic alopecia

Androgenetic alopecia (AGA), also known as male pattern baldness, is associated with androgen and androgen receptor (AR) signaling; however, the pathogenesis of AGA remains largely unknown. Here, we demonstrate that nuclear localization of androgen receptor is elevated in the dermal papilla (DP) of balding scalp from patients with AGA. Transcriptome analysis identifies microvascular abnormalities in the DP of balding scalp compared to non-balding scalp of AGA patients. We provide further evidence that blood vessels regress in the DP of balding scalp at the early stage of hair follicle miniaturization in AGA development. Consistently, we find that microvascular vessels accumulate around the dermal papilla upon anagen initiation, and angiogenesis is required for hair regeneration in mice. Mechanistically, we show that AR-mediated paracrine signaling, mainly TGF-β signaling, from DP cells induces apoptosis of microvascular endothelial cells in the DP of balding scalp of AGA. These findings define a role of AR-mediated regression of blood vessels in DP in AGA and support the notion that early anti-AR treatment is better than late treatment.

Regenerative Medicine Treatments for Androgenetic Alopecia

Regenerative medicine and the role of stem cells are being studied for applications in nearly every field of medicine. The pluripotent nature of stem cells underlies their vast potential for treatment of androgenic alopecia. Several advances in recent years have heightened interest in this field, chief among them are the evolution of simpler techniques to isolate regenerative elements and stems cells. These techniques are easy, outpatient procedures with immediate injection, often single session with harvest, and minimal manipulation (usually physical). This paper seeks to critically review the existing data and determine the current evidence and their role in practice.

Recreation of a hair follicle regenerative microenvironment: Successes and pitfalls

The hair follicle (HF) is an exquisite skin appendage endowed with cyclical regenerative capacity; however, de novo follicle formation does not naturally occur. Consequently, patients suffering from extensive skin damage or hair loss are deprived of the HF critical physiological and/or aesthetic functions, severally compromising skin function and the individual's psychosocial well-being. Translation of regenerative strategies has been prevented by the loss of trichogenic capacity that relevant cell populations undergo in culture and by the lack of suitable human-based in vitro testing platforms. Here, we provide a comprehensive overview of the major difficulties associated with HF regeneration and the approaches used to overcome these drawbacks. We describe key cellular requirements and discuss the importance of the HF extracellular matrix and associated signaling for HF regeneration. Finally, we summarize the strategies proposed so far to bioengineer human HF or hair-bearing skin models and disclose future trends for the field.

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

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

Is There a Histone Code for Cellular Quiescence?

Many of the cells in our bodies are quiescent, that is, temporarily not dividing. Under certain physiological conditions such as during tissue repair and maintenance, quiescent cells receive the appropriate stimulus and are induced to enter the cell cycle. The ability of cells to successfully transition into and out of a quiescent state is crucial for many biological processes including wound healing, stem cell maintenance, and immunological responses. Across species and tissues, transcriptional, epigenetic, and chromosomal changes associated with the transition between proliferation and quiescence have been analyzed, and some consistent changes associated with quiescence have been identified. Histone modifications have been shown to play a role in chromatin packing and accessibility, nucleosome mobility, gene expression, and chromosome arrangement. In this review, we critically evaluate the role of different histone marks in these processes during quiescence entry and exit. We consider different model systems for quiescence, each of the most frequently monitored candidate histone marks, and the role of their writers, erasers and readers. We highlight data that support these marks contributing to the changes observed with quiescence. We specifically ask whether there is a quiescence histone “code,” a mechanism whereby the language encoded by specific combinations of histone marks is read and relayed downstream to modulate cell state and function. We conclude by highlighting emerging technologies that can be applied to gain greater insight into the role of a histone code for quiescence.

Systematic review: The platelet-rich plasma use in female androgenetic alopecia as effective autologous treatment of regenerative plastic surgery

BACKGROUND

The number of clinical trials evaluating platelet-rich plasma (PRP) efficacy in female androgenetic alopecia (F-AGA) has exponentially increased during the last five years. A systematic review focused on this specific field has been performed by assessing the local infiltrations of PRP compared with any control for F-AGA in the selected studies.

OBJECTIVES

The aim of this study was to evaluate the safety and efficacy of the use of PRP in F-AGA.

METHODS

The protocol was developed in accordance with the Preferred Reporting for Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) guidelines. A multistep search of PubMed, MEDLINE, Embase, PreMEDLINE, Ebase, CINAHL, PsycINFO, Clinicaltrials.gov, Scopus database, and Cochrane databases has been performed to identify papers on female pattern hair loss (FPHL) treatment with PRP. Of the 63 articles initially identified, 11 articles focusing on AGA were selected and, consequently, only 5 articles focused exclusively on F-AGA were analyzed. Of this amount, 3 articles were randomized-controlled trials (RCTs), 1 clinical trial, and 1 double-blind placebo-controlled pilot study (DBPCPS). The studies included had to match predetermined criteria according to the PICOS (patients, intervention, comparator, outcomes, and study design) approach.

RESULTS

Eight percent of the articles selected and analyzed, reported a positive effect of PRP for F-AGA treatment. The information analyzed highlights the positive effects of PRP on F-AGA, without major side effects and thus, it may be considered as a safe and effective alternative procedure to treat hair loss compared with traditional drugs as Minoxidil® and Finasteride®.

CONCLUSIONS

The use of PRP in F-AGA was safe and effective for F-AGA.

Clinicopathologic Characteristics and Response to Treatment of Persistent Chemotherapy-Induced Alopecia in Breast Cancer Survivors

Importance

Alopecia induced by classic chemotherapy affects up to 65% of patients and is usually reversible. However, there are increasing reports of persistent chemotherapy-induced alopecia (pCIA), especially for patients treated with taxane-containing chemotherapy regimens.

Objective

To analyze the clinicopathologic characteristics and response to treatment of patients with pCIA after chemotherapy for breast cancer.

Design, Setting, and Participants

In this case series, a retrospective evaluation was performed of patients with a diagnosis of pCIA after chemotherapy for breast cancer in 4 specialist hair clinics from November 1, 2011, to February 29, 2020.

Main Outcomes and Measures

Clinical, trichoscopic, and histopathologic characteristics and treatment outcomes were analyzed. For patients who presented with diffuse alopecia or diffuse rarefaction of hair over the midfrontal scalp with widening of the central part line and preservation of the frontal hairline, the Sinclair scale (grades 1-5, where 1 indicates normal hair density and 5 indicates the most severe stage of hair loss, with little or no hair in the centroparietal region) was used to assess severity.

Results

One hundred patients (99 women [99%]; mean age at presentation, 54.0 years [range, 29.0-74.1 years]) were included. Most patients had diffuse nonscarring alopecia (n = 39), female pattern hair loss (n = 55), or male pattern hair loss (n = 6). Six patients developed cicatricial alopecia. Taxane-containing regimens were used for most patients (92 [92%]) and were associated with more severe alopecia than regimens that did not contain taxanes (median Sinclair grade, 4 [IQR, 3-5] vs 2 [IQR, 2-2.5]; P < .001). A total of 76 of 86 patients (88%) had trichoscopic signs indistinguishable from those of androgenetic alopecia. Of 18 patients who had biopsies, 14 had androgenetic alopecia-like features, 2 had cicatricial alopecia, and 2 had features of both. Both topical and oral minoxidil, sometimes combined with antiandrogen therapy, were associated with an improvement in hair density (median Sinclair grade, 4 [IQR, 3-5] before treatment vs 3 [IQR, 2-4] after treatment; P < .001).

Conclusions and Relevance

This case series outlines previously unreported features of pCIA in patients with breast cancer, including a trichoscopic description. Cosmetically significant regrowth was achieved for a significant proportion of patients with topical or systemic treatments, suggesting that pCIA may be at least partly reversible.

Human hair follicles operate an internal Cori cycle and modulate their growth via glycogen phosphorylase

Hair follicles (HFs) are unique, multi-compartment, mini-organs that cycle through phases of active hair growth and pigmentation (anagen), apoptosis-driven regression (catagen) and relative quiescence (telogen). Anagen HFs have high demands for energy and biosynthesis precursors mainly fulfilled by aerobic glycolysis. Histochemistry reports the outer root sheath (ORS) contains high levels of glycogen. To investigate a functional role for glycogen in the HF we quantified glycogen by Periodic-Acid Schiff (PAS) histomorphometry and colorimetric quantitative assay showing ORS of anagen VI HFs contained high levels of glycogen that decreased in catagen. qPCR and immunofluorescence microscopy showed the ORS expressed all enzymes for glycogen synthesis and metabolism. Using human ORS keratinocytes (ORS-KC) and ex vivo human HF organ culture we showed active glycogen metabolism by nutrient starvation and use of a specific glycogen phosphorylase (PYGL) inhibitor. Glycogen in ORS-KC was significantly increased by incubation with lactate demonstrating a functional Cori cycle. Inhibition of PYGL significantly stimulated the ex vivo growth of HFs and delayed onset of catagen. This study defines translationally relevant and therapeutically targetable new features of HF metabolism showing that human scalp HFs operate an internal Cori cycle, synthesize glycogen in the presence of lactate and modulate their growth via PYGL activity.

Dexpanthenol Promotes Cell Growth by Preventing Cell Senescence and Apoptosis in Cultured Human Hair Follicle Cells

Dexpanthenol (D-panthenol) is a precursor of vitamin B5 (pantothenic acid) and is widely used for dietary supplements and topical applications. D-panthenol has long been used in hair care products for the purpose of anti-hair loss, its effects and the underlying mechanisms, however, were barely reported. In this study, the effects of D-panthenol on human hair follicle cells, including dermal papilla cells (hDPCs) and outer root sheath cells (hORSCs), were investigated. D-panthenol enhanced the cell viability, increasing the cellular proliferation marker Ki67 in cultured hDPCs. The markers for apoptosis (Caspase3/9) and cell senescence (p21/p16), reported to be expressed in aged or resting phase follicles, were significantly reduced by D-panthenol. Anagen-inducing factors (ALP; β-catenin; versican), which trigger or elongate the anagen phase, were stimulated by D-panthenol. On the other hand, D-panthenol reduced TGF-β1 expressions in both mRNA and protein levels. The expression of VEGF, which is important for peripheral blood vessel activation; was up-regulated by D-panthenol treatment. In cultured hORSCs, cell proliferation and viability were enhanced, while the mRNA expression of cell senescence markers (p21/p16) was significantly down-regulated. The expressions of both VEGF and its receptor (VEGFR) were up-regulated by D-panthenol. In conclusion, our data suggest that the hair growth stimulating activity of D-panthenol was exerted by increasing the cell viability, suppressing the apoptotic markers, and elongating the anagen phase in hair follicles.