Sebaceous gland, hair shaft, and epidermal barrier abnormalities in keratosis pilaris with and without filaggrin deficiency

Hair follicles modulate skin barrier function

Our skin provides a protective barrier that shields us from our environment. Barrier function is typically associated with the interfollicular epidermis; however, whether hair follicles influence this process remains unclear. Here, we utilize a potent genetic tool to probe barrier function by conditionally ablating a quintessential epidermal barrier gene, Abca12, which is mutated in the most severe skin barrier disease, harlequin ichthyosis. With this tool, we deduced 4 ways by which hair follicles modulate skin barrier function. First, the upper hair follicle (uHF) forms a functioning barrier. Second, barrier disruption in the uHF elicits non-cell-autonomous responses in the epidermis. Third, deleting Abca12 in the uHF impairs desquamation and blocks sebum release. Finally, barrier perturbation causes uHF cells to move into the epidermis. Neutralizing IL-17a, whose expression is enriched in the uHF, partially alleviated some disease phenotypes. Altogether, our findings implicate hair follicles as multi-faceted regulators of skin barrier function.

Hair follicles modulate skin barrier function

Our skin provides a protective barrier that shields us from our environment. Barrier function is typically associated with interfollicular epidermis; however, whether hair follicles influence this process remains unclear. Here, we utilize a potent genetic tool to probe barrier function by conditionally ablating a quintessential epidermal barrier gene, Abca12, which is mutated in the most severe skin barrier disease, harlequin ichthyosis. With this tool, we deduced 4 ways by which hair follicles modulate skin barrier function. First, the upper hair follicle (uHF) forms a functioning barrier. Second, barrier disruption in the uHF elicits non-cell autonomous responses in the epidermis. Third, deleting Abca12 in the uHF impairs desquamation and blocks sebum release. Finally, barrier perturbation causes uHF cells to move into the epidermis. Neutralizing Il17a, whose expression is enriched in the uHF, partially alleviated some disease phenotypes. Altogether, our findings implicate hair follicles as multi-faceted regulators of skin barrier function.

Trichothiodystrophy-associated MPLKIP maintains DBR1 levels for proper lariat debranching and ectodermal differentiation

The brittle hair syndrome Trichothiodystrophy (TTD) is characterized by variable clinical features, including photosensitivity, ichthyosis, growth retardation, microcephaly, intellectual disability, hypogonadism, and anaemia. TTD-associated mutations typically cause unstable mutant proteins involved in various steps of gene expression, severely reducing steady-state mutant protein levels. However, to date, no such link to instability of gene-expression factors for TTD-associated mutations in MPLKIP/TTDN1 has been established. Here, we present seven additional TTD individuals with MPLKIP mutations from five consanguineous families, with a newly identified MPLKIP variant in one family. By mass spectrometry-based interaction proteomics, we demonstrate that MPLKIP interacts with core splicing factors and the lariat debranching protein DBR1. MPLKIP-deficient primary fibroblasts have reduced steady-state DBR1 protein levels. Using Human Skin Equivalents (HSEs), we observed impaired keratinocyte differentiation associated with compromised splicing and eventually, an imbalanced proteome affecting skin development and, interestingly, also the immune system. Our data show that MPLKIP, through its DBR1 stabilizing role, is implicated in mRNA splicing, which is of particular importance in highly differentiated tissue.

A Review of the Scoring and Assessment of Keratosis Pilaris

Disease severity assessment tools play a large part in evaluating skin conditions in dermatology. Currently, there is no existing validated assessment tool for keratosis pilaris (KP), a benign yet highly prevalent follicular disorder. A range of proposed scoring tools have been used in different clinical trials for the assessment of potential treatments for KP. A literature review of the current scoring systems used for KP shows that there is a lack of consistency with most studies using varying versions of unvalidated investigator global assessment (IGA) scores and quartile grading systems. A review of these studies shows that current methods of evaluating KP in clinical trials are subjective, unreliable, and inconsistent. A standardised and validated scoring system would be significant as it could be used in clinical trials to advance the current knowledge of KP.

Sebaceous immunobiology - skin homeostasis, pathophysiology, coordination of innate immunity and inflammatory response and disease associations

This review presents several aspects of the innovative concept of sebaceous immunobiology, which summarizes the numerous activities of the sebaceous gland including its classical physiological and pathophysiological tasks, namely sebum production and the development of seborrhea and acne. Sebaceous lipids, which represent 90% of the skin surface lipids in adolescents and adults, are markedly involved in the skin barrier function and perifollicular and dermal innate immune processes, leading to inflammatory skin diseases. Innovative experimental techniques using stem cell and sebocyte models have clarified the roles of distinct stem cells in sebaceous gland physiology and sebocyte function control mechanisms. The sebaceous gland represents an integral part of the pilosebaceous unit and its status is connected to hair follicle morphogenesis. Interestingly, professional inflammatory cells contribute to sebocyte differentiation and homeostasis, whereas the regulation of sebaceous gland function by immune cells is antigen-independent. Inflammation is involved in the very earliest differentiation changes of the pilosebaceous unit in acne. Sebocytes behave as potent immune regulators, integrating into the innate immune responses of the skin. Expressing inflammatory mediators, sebocytes also contribute to the polarization of cutaneous T cells towards the Th17 phenotype. In addition, the immune response of the perifollicular infiltrate depends on factors produced by the sebaceous glands, mostly sebaceous lipids. Human sebocytes in vitro express functional pattern recognition receptors, which are likely to interact with bacteria in acne pathogenesis. Sex steroids, peroxisome proliferator-activated receptor ligands, neuropeptides, endocannabinoids and a selective apoptotic process contribute to a complex regulation of sebocyte-induced immunological reaction in numerous acquired and congenital skin diseases, including hair diseases and atopic dermatitis.

Follicular Keratosis in Adolescents: Diagnostic Features and Cosmetological Aspects of Therapy

Follicular keratosis (FK) is one of the most common dermatological diseases in children. FK manifests usually in early childhood and worsen frequently, thus, symptoms are more prominent during puberty. The skin of proximal extensors of upper and lower limbs is mainly affected, while skin of cheeks, back and buttocks is affected more rarely. FK is just a cosmetic defect which significantly affects adolescents’ self-esteem and emotional state up to the development of severe depressive syndrome and obsessive conditions accompanied by pathomimia. FK can be associated with other nosologies such as: atopic dermatitis, vulgar ichthyosis, obesity, diabetes mellitus, and even aggravate Down and Noonan syndromes. Spontaneous improvement is still possible with age. We can use topical therapy with emollient, keratolytic, anti-inflammatory drugs, as well as various types of laser and phototherapy to alleviate the disease symptoms. This article provides basic information on etiology, pathogenesis, and treatment of FK with clinical case description.

Bioinformatic Analyzes of the Association Between Upregulated Expression of JUN Gene via APOBEC-Induced FLG Gene Mutation and Prognosis of Cervical Cancer

Globally, cervical cancer (CC) is the most common malignant tumor of the female reproductive system and its incidence is only second after breast cancer. Although screening and advanced treatment strategies have improved the rates of survival, some patients with CC still die due to metastasis and drug resistance. It is considered that cancer is driven by somatic mutations, such as single nucleotide, small insertions/deletions, copy number, and structural variations, as well as epigenetic changes. Previous studies have shown that cervical intraepithelial neoplasia is associated with copy number variants (CNVs) and/or mutations in cancer-related genes. Further, CC is also related to genetic mutations. The present study analyzed the data on somatic mutations of cervical squamous cell carcinoma (CESC) in the Cancer Genome Atlas database. It was evident that the Apolipoprotein B mRNA editing enzyme-catalyzed polypeptide-like (APOBEC)-related mutation of the FLG gene can upregulate the expression of the JUN gene and ultimately lead to poor prognosis for patients with CC. Therefore, the findings of the current study provide a new direction for future treatment of CC.

Preparing the hair follicle canal for hair shaft emergence

The emergence of hair is a defining event during mammalian skin development, but the cellular mechanisms leading to the opening of the hair follicle canal remain poorly characterized. Our previous studies have shown that early hair buds possess a central column of differentiated keratinocytes expressing Keratin 79 (K79), which marks the future hair follicle opening. Here, we report that during late embryogenesis and early postnatal development, K79+ cells at the distal tips of these columns downregulate E-cadherin, change shape, recede and undergo cell death. These changes likely occur independently of sebaceous glands and the growing hair shaft, and serve to create an orifice for hair to subsequently emerge. Defects in this process may underlie phenomena such as ingrown hair or may potentially contribute to upper hair follicle pathologies including acne, hidradenitis suppurativa and infundibular cysts.

Acne in the first three decades of life: An update of a disorder with profound implications for all decades of life

Acne vulgaris is a chronic, inflammatory, skin condition that involves the pilosebaceous follicles and is influenced by a variety of factors including genetics, androgen-stimulation of sebaceous glands with abnormal keratinization, colonization with Cutibacterium acnes (previously called Propionibacterium acnes), and pathological immune response to inflammation. Acne can occur at all ages and this discussion focuses on the first three decades of life. Conditions that are part of the differential diagnosis and/or are co-morbid with acne vulgaris are also considered. Acne in the first year of life includes neonatal acne (acne neonatorum) that presents in the first four weeks of life and infantile acne that usually presents between 3 and 6 months of the first year of life with a range of 3 to 16 months after birth. Acne rosacea is a chronic, inflammatory, skin condition that is distinct from acne vulgaris, typically presents in adults, and has four main types: erythemato-telangiectatic, papulopustular, phymatous and ocular. Treatment options for acne vulgaris include topical retinoids, topical benzoyl peroxide, antibiotics (topical, oral), oral contraceptive pills, isotretinoin, and others. Management must consider the increasing impact of antibiotic resistance in the 21st century. Psychological impact of acne can be quite severe and treatment of acne includes awareness of the potential emotional toll this disease may bring to the person with acne as well as assiduous attention to known side effects of various anti-acne medications (topical and systemic). Efforts should be directed at preventing acne-caused scars and depigmentation on the skin as well as emotional scars within the person suffering from acne.

Functional and proteomic analysis of a full thickness filaggrin-deficient skin organoid model

Background: Atopic eczema is an itchy inflammatory disorder characterised by skin barrier dysfunction. Loss-of-function mutations in the gene encoding filaggrin ( FLG) are a major risk factor, but the mechanisms by which filaggrin haploinsufficiency leads to atopic inflammation remain incompletely understood. Skin as an organ that can be modelled using primary cells in vitro provides the opportunity for selected genetic effects to be investigated in detail.

Methods: Primary human keratinocytes and donor-matched primary fibroblasts from healthy individuals were used to create skin organoid models with and without siRNA-mediated knockdown of FLG. Biological replicate sets of organoids were assessed using histological, functional and biochemical measurements.

Results:FLG knockdown leads to subtle changes in histology and ultrastructure including a reduction in thickness of the stratum corneum and smaller, less numerous keratohyalin granules. Immature organoids showed some limited evidence of barrier impairment with FLG knockdown, but the mature organoids showed no difference in transepidermal water loss, water content or dye penetration. There was no difference in epidermal ceramide content. Mass spectrometry proteomic analysis detected >8000 proteins per sample. Gene ontology and pathway analyses identified an increase in transcriptional and translational activity but a reduction in proteins contributing to terminal differentiation, including caspase 14, dermokine, AKT1 and TGF-beta-1. Aspects of innate and adaptive immunity were represented in both the up-regulated and down-regulated protein groups, as was the term ‘axon guidance’.     

Conclusions: This work provides further evidence for keratinocyte-specific mechanisms contributing to immune and neurological, as well as structural, aspects of skin barrier dysfunction. Individuals with filaggrin deficiency may derive benefit from future therapies targeting keratinocyte-immune crosstalk and neurogenic pruritus.

Innovative 1064-nm Nd:YAG Laser Significantly Improves Keratosis Pilaris, A Randomized, Double-Blind, Sham-Irradiation-Controlled Trial

BACKGROUND AND OBJECTIVE

Keratosis pilaris (KP) is a common follicular disorder for which various topical agents and energy-based devices have been used with some efficacy. To evaluate the efficacy of a novel 1064-nm Nd:YAG laser for the reduction of skin roughness, erythema, and hyperpigmentation in KP subjects.

STUDY DESIGN/MATERIALS AND METHODS

Twenty-three subjects with untreated KP on the upper outer arms participated in a randomized, single-blind fashion. One arm of each subject was divided into upper and lower parts. One part was randomized to be treated with an innovative 1064-nm Nd:YAG laser, while the other part received sham irradiation. Subjects received four consecutive treatments at 4-week intervals. Antera3D was used to measure skin roughness, erythema, and hyperpigmentation at baseline and 4 weeks after the last treatment. Moreover, clinical outcomes were also evaluated by subjects' Global Improvement Score (GIS) and subjects' satisfaction grading scores.

RESULTS

Twenty-three subjects completed the study. There was statistically significant reduction of skin roughness measured by Antera3D compared with control group (P < 0.001). There were statistically significant improvements of skin roughness, erythema, hyperpigmentation, and overall appearances graded by subjects' Global Improvement Score (P < 0.001 all). Subjects' satisfaction scores were graded significantly better in treatment parts (P < 0.001). No adverse events including burning, bulla, erosion, post-inflammatory hyper/hypopigmentation, and scar formation developed in any subjects throughout the study period.

CONCLUSION

This innovative 1064-nm Nd:YAG laser has proved to significantly and safely reduce skin roughness in Thai KP subjects compared with control after four sessions. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Intense Pulsed-light Therapy Significantly Improves Keratosis Pilaris: A Randomized, Double-blind, Sham Irradiation-controlled Trial

Background: Keratosis pilaris (KP) is a common benign follicular disorder for which various topical and laser treatments have been used, with limited efficacy. Objective: We evaluated the efficacy of intense pulsed light (IPL) therapy for the reduction of skin roughness, erythema, and hyperpigmentation in Thai subjects with KP. Material and Methods: Twenty-four Thai patients with untreated KP on the upper outer arms were enrolled in a randomized, double-blind study. Only one arm of each subject was included and divided into upper and lower parts (25 cm² per each part). One part was randomized to be treated with IPL using 645 to 950-nm cutoff filter and fluences of 15 to 18 J/cm², while the other part was treated with sham irradiation. Subjects received four consecutive treatments at four-week intervals. Antera3D was used to measure skin roughness, erythema, and hyperpigmentation at baseline and four weeks after the last treatment. Moreover, clinical outcomes were also evaluated by subject Global Improvement Scores (GIS) and subject satisfaction grading scores. Results: Twenty-three subjects completed the study. There was statistically significant reduction of skin roughness, measured by Antera3D, compared to control group (p<0.001). However, the reduction of skin erythema was not significantly different between two groups (p=0.660). Skin hyperpigmentation significantly increased in the control group compared with intervention group (p=0.01). There were statistically significant improvements in skin roughness, erythema, hyperpigmentation, and overall appearance, graded by subject Global Improvement Scores (p<0.001). Subject satisfaction scores were significantly better in treatment parts (p<0.001). No adverse events, including burning, bulla, erosion, postinflammatory hyper/hypopigmentation, and scar formation developed in any subjects throughout study period. Conclusion: IPL has demonstrated the ability to significantly and safely reduce skin roughness in subjects with KP compared to control after four sessions.

Proteomic analysis of a filaggrin-deficient skin organoid model shows evidence of increased transcriptional-translational activity, keratinocyte-immune crosstalk and disordered axon guidance

Background:Atopic eczema is an itchy inflammatory disorder characterised by skin barrier dysfunction. Loss-of-function mutations in the gene encoding filaggrin (FLG) are a major risk factor, but the mechanisms by which filaggrin haploinsufficiency leads to atopic inflammation remain incompletely understood. Skin as an organ that can be modelled using primary cellsin vitroprovides the opportunity for selected genetic effects to be investigated in detail.Methods:Primary human keratinocytes and donor-matched primary fibroblasts from healthy individuals were used to create skin organoid models with and without siRNA-mediated knockdown ofFLG. Biological replicate sets of organoids were assessed using histological, functional and biochemical measurements.Results:FLGknockdown leads to subtle changes in histology and ultrastructure including a reduction in thickness of the stratum corneum and smaller, less numerous keratohyalin granules. Immature organoids showed evidence of barrier impairment withFLGknockdown, but the mature organoids showed no difference in transepidermal water loss, water content or dye penetration. There was no difference in epidermal ceramide content. Mass spectrometry proteomic analysis detected >8000 proteins per sample. Gene ontology and pathway analyses identified an increase in transcriptional and translational activity but a reduction in proteins contributing to terminal differentiation, including caspase 14, dermokine, AKT1 and TGF-beta-1. Aspects of innate and adaptive immunity were represented in both the up-regulated and down-regulated protein groups, as was the term ‘axon guidance’.     Conclusions:This work provides further evidence for keratinocyte-specific mechanisms contributing to immune and neurological, as well as structural, aspects of skin barrier dysfunction. Individuals with filaggrin deficiency may derive benefit from future therapies targeting keratinocyte-immune crosstalk and neurogenic pruritus.

Keratosis pilaris rubra with mucin deposition

Keratosis pilaris (KP) is a benign cutaneous disorder characterized by folliculocentric hyperkeratotic papules most often occurring on the proximal extremities. Erythema is usually limited to perifollicular skin, but when keratosis pilaris presents on a background of confluent erythema, the term keratosis pilaris rubra (KPR) is used. The histological findings associated with KP have not been well described in the literature. Herein, we present a case of a 14-year-old male with a 7-year history of erythema and follicular-based papules over his bilateral cheeks, consistent with KPR. Histological examination revealed abundant mucin, keratotic follicular plugging, and periadnexal lymphocytosis. Our novel finding of abundant dermal mucin expands the histopathologic description of KPR.

Keratosis Pilaris and its Subtypes: Associations, New Molecular and Pharmacologic Etiologies, and Therapeutic Options

Keratosis pilaris is a common skin disorder comprising less common variants and rare subtypes, including keratosis pilaris rubra, erythromelanosis follicularis faciei et colli, and the spectrum of keratosis pilaris atrophicans. Data, and critical analysis of existing data, are lacking, so the etiologies, pathogeneses, disease associations, and treatments of these clinical entities are poorly understood. The present article aims to fill this knowledge gap by reviewing literature in the PubMed, EMBASE, and CINAHL databases and providing a comprehensive, analytical summary of the clinical characteristics and pathophysiology of keratosis pilaris and its subtypes through the lens of disease associations, genetics, and pharmacologic etiologies. Histopathologic, genomic, and epidemiologic evidence points to keratosis pilaris as a primary disorder of the pilosebaceous unit as a result of inherited mutations or acquired disruptions in various biomolecular pathways. Recent data highlight aberrant Ras signaling as an important contributor to the pathophysiology of keratosis pilaris and its subtypes. We also evaluate data on treatments for keratosis pilaris and its subtypes, including topical, systemic, and energy-based therapies. The effectiveness of various types of lasers in treating keratosis pilaris and its subtypes deserves wider recognition.

Mutation and expression of ABCA12 in keratosis pilaris and nevus comedonicus

Keratosis pilaris (KP) and nevus comedonicus (NC) are congenital keratinized dermatoses; however, the exact etiology of these two diseases is unclear. The objective of the present study was to identify the disease-causing genes and their association with functional alterations in the development of KP and NC. Peripheral blood samples of one KP family, two NC families and 100 unrelated healthy controls were collected. The genomic sequences of 147 genes associated with 143 genetic skin diseases were initially analyzed from the KP proband using a custom-designed GeneChip. A novel heterozygous missense mutation in the ATP-binding cassette sub-family A member 12 (ABCA12) gene, designated c.6694G>T (p.Asp2232Tyr), was identified in the KP proband and confirmed by Sanger sequencing. The same mutation was also present in the affected family members but not in the healthy family members, the two patients with NC or population-matched controls. The predictions provided by PolyPhen-2 and SIFT analyses suggested that the mutation may produce a damaged protein. The region surrounding the mutation is the extra-membrane domain, which is conserved among particular species, as suggested by ClustalX; however, no ABCA12 mutations were reported in the patients with NC. As observed by immunofluorescence, ABCA12 expression was upregulated in the sebaceous glands of the patients with NC compared with that of normal controls. In summary, ABCA12-associated mutations or alterations in expression may exhibit causative or contributive effects to the development of keratinized dermatoses, including KP and NC.

Skin diseases associated with atopic dermatitis

Atopic dermatitis is a common chronic pruritic inflammatory skin disorder, characterized by an abnormal skin barrier, immune dysfunction, and an altered skin microbiome. Atopic dermatitis may be seen in conjunction with a variety of other skin disorders due to the complex pathogenesis of atopic dermatitis, involving genetic and environmental factors that are associated with immune dysfunction, barrier defects, and altered skin microbiomes. Skin disorders associated with atopic dermatitis include diseases sharing similar genetic origins like ichthyosis vulgaris, infectious diseases such as impetigo, and eczema herpeticum, in addition to the cutaneous autoimmune diseases, alopecia areata, and vitiligo. Atopic dermatitis is also often linked to such benign conditions as pityriasis alba and keratosis pilaris. This review discusses the cutaneous comorbidities of atopic dermatitis and their relationship via their occurrence in conjunction with atopic dermatitis.

Filaggrin loss-of-function mutations, atopic dermatitis and risk of actinic keratosis: results from two cross-sectional studies

BACKGROUND

Common loss-of-function mutations in filaggrin gene (FLG) represent a strong genetic risk factor for atopic dermatitis (AD). Homozygous mutation carriers typically display ichthyosis vulgaris (IV) and many have concomitant AD. Previously, homozygous, but not heterozygous, filaggrin gene mutations have been associated with squamous cell carcinomas.

OBJECTIVE

The first objective was to examine the association between FLG mutations and actinic keratosis (AK). The second objective was to investigate the occurrence of AK in patients with IV and AD, respectively.

METHODS

FLG mutation status in patients with AK was compared with controls from the general population. Furthermore, based on nationwide data from Danish registers, we compared the risk of AK in patients with IV, AD and psoriasis, respectively.

RESULTS

The prevalence of homozygous FLG mutations was significantly higher in the AK group (n = 4, 0.8%) in comparison with the control group (n = 18, 0.2%), whereas the prevalence of heterozygous FLG mutations was lower. In hospital registry data, patients with AD exhibited an increased risk of AK than did psoriasis controls (adjusted OR 1.46; [95% CI 1.12-1.90]), whereas no difference in risk was observed between patients with IV and AD.

CONCLUSIONS

This study indicates an increased susceptibility to AK in individuals with homozygous, but not heterozygous, FLG mutations and in patients with AD compared to psoriasis. Whether a reduction or absence of epidermal filaggrin could contribute to the susceptibility to AK in patients with IV and AD is unknown and additional research is needed to further explore this relationship.