Experimental Models and Molecular Pathogenesis: An Integrated Review of Alopecia

Fibroblast bioelectric signaling can promote hair growth and may help treat hair loss.

This study found that Ageratum conyzoides extract enhanced hair growth in mice and human follicle cells, showing potential for hormonal modulation, pathway activation, and antioxidant protection; however, further clinical studies are needed to confirm efficacy in humans.

This study found that exosomes from human umbilical cord mesenchymal stem cells significantly promoted hair follicle growth and enhanced the transition to the growth phase in a model of androgenetic alopecia, by enriching specific microRNAs that activate key pathways involved in hair regeneration.

This study presents male pattern androgenetic alopecia (mpAGA) as a natural physiological process involving reversible transformation of hair follicles, but notes unresolved links with androgen mechanisms and highlights potential research avenues beyond androgen receptor signaling for treatment exploration.

UVA exposure worsens hair loss by activating a specific cell pathway.

This study found that administering adipose-derived stem cells with ATP improved hair regrowth in male mice with androgenetic alopecia, while the combination was less effective in female mice.

This review discusses the mechanisms regulating wound-induced hair-follicle neogenesis and highlights potential treatments, like Wnt signaling activators, for enhancing this process in humans, yet reports no new clinical results.

In this study using a mouse model, RIPK1 inhibitors were found to delay the onset of alopecia areata, reduce immune cell numbers in affected skin, and increase hair length, indicating a potential therapeutic role in preventing alopecia areata.

This systematic review and meta-analysis reports a significant familial risk of autoimmune and related conditions among relatives of individuals with Alopecia Areata, highlighting the importance of comprehensive family monitoring and genetic counseling.

In this study, researchers found that specific genetic variations at loci rs1160312, rs6113491, and rs1041668 are independent risk factors for androgenetic alopecia in men, and these risks can be influenced by diet.

This study found that umbilical cord mesenchymal stem cell-derived exosomes improved hair growth in mice with androgenetic alopecia by promoting hair follicle stem cell stemness through the RAS/ERK pathway, suggesting a potential new treatment strategy for this condition.

In this study, patients with androgenetic alopecia experiencing stress had higher cortisol levels and altered neurotrophic factors compared to non-stressed patients, which correlated with more severe hair loss progression even after minoxidil treatment.

This study reports that Hair RiseTM microemulsion, made from plant extracts, significantly enhanced hair follicle cell growth and improved hair growth signaling pathways, suggesting it as a plant-based alternative for androgenetic alopecia treatment.

This study observed that patients with post-COVID telogen effluvium had lower serum ferritin levels than controls, but the levels were not indicative of nonanemic iron deficiency.

This meta-analysis suggests that combining platelet-rich plasma with minoxidil enhances hair growth and patient satisfaction more effectively than using either treatment alone for androgenetic alopecia.

In this review, an association was reported between early-onset androgenetic alopecia and several health conditions like obesity and cardiovascular disease, with genetic and therapeutic research ongoing to improve treatment.

The researchers reported that disrupting ATRA signaling by deleting RDHE genes in the hair follicle led to altered hair follicle cycles, composition, and gene expression, indicating RDHEs' role in hair follicle signaling coordination.

Ganoderma lucidum extract may help treat stress-related hair loss.

This study observed that pilose antler extract promoted hair growth in mice with androgenetic alopecia by stimulating the hair follicle growth cycle via the SHH/GLI pathway activation and BMP/Smad pathway suppression.

This retrospective study of 500 female patients with telogen effluvium found that those with hypothyroidism had more severe hair loss compared to those with normal thyroid function or hyperthyroidism, highlighting the importance of thyroid function testing in these cases.

This review discusses anticoagulant and antihypertensive medications as potential contributors to medication-induced telogen effluvium and reports no new clinical results.

This review covers medication-induced telogen effluvium with a focus on systemic retinoids, antifungal agents, and psychotropic medications, and reports no new clinical results.

JAK inhibitors and platelet-rich plasma show promise for treating alopecia areata.

This comprehensive review analyzes androgenetic alopecia treatments, discussing the mechanisms, costs, efficacy, and safety of FDA-approved drugs like minoxidil and finasteride, as well as newer non-FDA-approved options that have shown effectiveness across various studies.

In this study, Allium hookeri extract increased viability and size of dermal papilla cell spheroids and reduced oxidative stress effects, potentially promoting hair growth by regulating specific protein signaling pathways in human cells.

This study found that exosomes from adipose mesenchymal stromal cells, particularly those carrying miR-122-5p, may enhance hair follicle regeneration in androgenic alopecia by targeting the TGF-β/SMAD3 axis.

In this study, miR-221 was identified as a key factor in androgenetic alopecia pathogenesis due to its role in suppressing hair growth by interacting with androgen receptors and affecting related pathways.

This review discusses the potential of JAK inhibitors as a promising treatment strategy for alopecia areata, highlighting their mechanism and recent FDA approval based on clinical trial efficacy.

This study reports that the global age-standardized incidence and disability-adjusted life-year rates of alopecia areata decreased from 1990 to 2019, with the highest increases in incidence seen in some low SDI regions and countries like Kuwait and South Sudan.

This study found an association between sleep disturbances and androgenetic alopecia in men, with severe AGA linked to shorter sleep duration, poorer sleep quality, and higher STOP-BANG scores.

This study demonstrated that a 3D bioprinting technique using a gelatin/alginate hydrogel scaffold can regenerate entire hair follicles in mice, offering potential advancements in hair loss treatment.

This study found that nutritional supplementation with hydrolyzed collagen, amino acids, vitamins, and minerals significantly improved hair anagen/telogen ratios and hair density in telogen effluvium patients.

This study found that patients with telogen effluvium had a higher rate of acute hair loss and lower monocyte counts if they had contracted COVID-19 prior to hair loss onset.

This study identified KRT82 as a significant Alopecia Areata risk gene, finding that rare damaging variants are linked to elevated immune cell infiltration around hair follicles in affected individuals.

This article discusses hormonal mechanisms underlying androgenetic alopecia but does not report any new findings; it reviews the roles of dihydrotestosterone and available FDA-approved treatments.

This study reports that persistent chemotherapy-induced alopecia in breast cancer patients frequently resembles androgenetic alopecia, and treatment with minoxidil, alone or with antiandrogens, improved hair density in many cases.

This study observed that inflammation in androgenetic alopecia samples was similar to alopecia areata controls, but infundibular and isthmic inflammation were significantly more common in androgenetic alopecia cases.

This study found that telogen effluvium and trichodynia are common in patients after COVID-19, and their severity may be influenced by the severity of the COVID-19 infection.

This study found that acute telogen effluvium after COVID-19 typically began about 1.5 months post-infection and resolved sooner than typical cases, with most resolving in under two months.

In this study, selective inhibition of JAK3 signaling effectively prevented and reversed alopecia areata in a mouse model, while JAK2 inhibitors did not restore hair growth.

This review evaluates laboratory models used in androgenetic alopecia research but reports no new findings, emphasizing the potential of human-derived 3-D models for future studies.

This study found that dihydrotestosterone induced hair loss and changes in hair morphology in male C57BL/6 mice, effects that could be partially reversed by the AR antagonist bicalutamide.

This review describes the diagnosis and management challenges of telogen effluvium, a type of hair loss triggered by physiological stress, and summarizes current understanding of its mechanisms and treatments while recommending future research directions.

This study suggests that COVID-19 infection may trigger telogen effluvium, a condition of hair shedding, though medication side effects and pandemic-related stress cannot be excluded as contributing factors.

This study observed that telogen effluvium, or acute hair loss, often occurs 1 to 3 months after SARS-CoV-2 infection, earlier than classic telogen effluvium.

This article discusses SARS-CoV-2-induced telogen effluvium in a multicentric study and reports no new clinical results.

This review discusses immune privilege in anagen hair follicles and its collapse in alopecia areata, emphasizing the importance of restoring this function for effective management and disease relapse prevention.

This review discusses the causes, diagnosis, and treatment of telogen effluvium and reports no new clinical findings; the authors underscore the importance of identifying and eliminating causative factors.

In this study, researchers found that caffeine can counteract stress-induced damage in ex vivo human androgenetic alopecia hair follicles, suggesting it may help prevent stress-related hair loss.

This abstract discusses the efficacy of spironolactone, cyproterone acetate, and flutamide in treating female pattern hair loss, noting that flutamide use requires caution due to potential liver toxicity, especially at high doses.

This review discusses female androgenetic alopecia, highlighting its diagnostic challenges and management strategies, but it reports no new results.

This study found that vascular endothelial growth factor may protect hair follicle stem cells from androgen-induced apoptosis in androgenic alopecia patients via the PI3K/Akt pathway.

In this study, researchers found that alkylating chemotherapy causes hair follicle stem cells to lose their regenerative ability by initially triggering proliferation followed by apoptosis, leading to permanent regeneration loss.

This study found a significant reduction in Treg cell frequency in alopecia areata compared to other autoimmune and non-autoimmune skin diseases using immunohistochemical staining.

This study found that trichoscopic examination is useful for diagnosing and monitoring systemic lupus erythematosus, with severe diffuse non-scarring alopecia indicating active disease.

Hair loss can happen after a fever caused by Rickettsia conorii infection.

In this study, dermal papilla cell-derived exosomes accelerated hair follicle growth in mice, suggesting potential for treating hair loss by modulating key signaling pathways.

This study found that patients with androgenetic alopecia had a higher prevalence of metabolic syndrome compared to healthy controls.

This review discusses the role of Hedgehog signaling in epidermal and hair follicle development and its involvement in basal cell carcinoma, without reporting new empirical findings.

This study established an androgen-responsive human organ culture model using hair follicles, demonstrating that women's intermediate facial follicles grow more hair in response to men's higher androgen levels.

In this study, women with chronic telogen effluvium experienced reduced hair shedding after being treated with once daily oral minoxidil for 12 months, but facial hypertrichosis was a reported side effect, suggesting the need for further placebo-controlled research.

This review noted that alopecia areata is an autoimmune disease impacting hair follicles and offered insights into its complex pathogenesis involving immune responses, while highlighting ongoing research into new treatments such as Janus kinase inhibitors and other immunomodulatory drugs.

This study suggests that the interaction between CXXC5 and Dishevelled is a potential target for promoting hair regrowth and hair follicle formation, offering a new approach to treat hair loss.

This review summarizes the genetic studies on female pattern hair loss, highlighting the lack of clearly identified susceptibility loci and suggesting distinct aetiological differences from male pattern hair loss.

This article details laboratory methods for isolating and culturing human dermal papilla cells but provides no new experimental results.

This proposal reviews current knowledge and suggests actions for managing chemotherapy‐induced alopecia but reports no new clinical results, highlighting the need for evidence‐based guidelines.

This article addresses the need to screen for nutrient deficiencies in patients with hair loss but reports no new findings, noting that supplementation without deficiency may not be beneficial and could pose risks.

This study found that DKK1 and WNT10b are paracrine factors that modulate hair follicle stem cell differentiation inhibition, contributing to androgenetic alopecia by affecting Wnt signaling in androgen-sensitive dermal papilla cells after dihydrotestosterone stimulation.

This study found that activating Nrf2 in human hair follicles significantly reduced oxidative stress, lipid peroxidation, and protected against hair growth inhibition, suggesting a protective role for Nrf2 against redox insult in this context.

This study suggests that crosstalk between Wnt/β-catenin and TGF-β signaling pathways may contribute to the development of androgenetic alopecia.

This review discusses diagnostic strategies for pediatric hair loss, emphasizing the importance of thorough examinations and dermoscopy for accurate diagnosis, and reports no new research findings.

This study observed that applying JAK-STAT pathway inhibitors to mouse and human skin led to rapid hair growth by inducing the anagen phase of hair follicles.

This study found that dihydrotestosterone (DHT) may shorten the hair growth cycle through mechanisms like cell-cycle arrest and β-catenin downregulation in rat hair follicle cells.

This letter to the editor on postpartum telogen effluvium does not include new research findings or data.

This study found that scalp cooling significantly reduced the risk of chemotherapy-induced alopecia in breast cancer patients, while topical minoxidil and other interventions did not show significant efficacy.

This study found that doxorubicin induces hair follicle apoptosis through TRAIL receptor signaling, providing insights for managing chemotherapy-induced hair loss.

This study developed an animal model that recreates alopecia areata by injecting healthy human skin grafts in immunocompromised mice with peripheral blood mononuclear cells enriched for NKG2D+ and CD56+ cells.

This review highlights the need for a deeper understanding of the genetic mechanisms in alopecia areata to develop evidence-based treatments, but it provides no new experimental results.

This review discusses the molecular mechanisms involved in hair follicle development and regeneration, highlighting findings from mouse genetic studies, and reports no new experimental results.

This study found that androgens inhibit hair follicle stem cell differentiation by disrupting the Wnt signalling pathway in dermal papilla cells, but Wnt activation can restore differentiation.

This study reports the development of the first rodent model for androgenetic alopecia, demonstrating that overexpression of androgen receptors in mice delays hair regeneration and can be used to test new treatments.

In this study, androgen did not affect keratinocyte growth in coculture with androgenetic alopecia-derived dermal papilla cells, but did significantly suppress keratinocyte growth when androgen receptor was overexpressed in the papilla cells.

Inflammation may be linked to hair loss, and targeting specific enzymes could help treat it.

This study observed that alopecia areata can be induced and serially transferred in C3H/HeJ mice using skin grafts, providing a useful model for studying the disease in humans.

This study found that the non-steroidal antiandrogen RU58841 increased hair growth rates and promoted hair cycle initiation in balding human scalp grafts on testosterone-conditioned nude mice, indicating a positive effect on hair growth.

This study found that combining adult germinative epidermal cells with non-inductive dermal cells can stimulate hair follicle neogenesis, effectively altering the cells' status to enhance induction.

This study found that a non-scarring alopecia in C3H/HeJ mice resembles human alopecia areata and may serve as a valuable model for studying specific subtypes of the human condition.

Minoxidil promotes hair growth but stops working when discontinued.