Ectodysplasin A regulates epithelial barrier function through sonic hedgehog signalling pathway

Compartmentalized ciliation changes of oligodendrocytes in aged mouse optic nerve

Primary cilia are microtubule-based sensory organelles that project from the apical surface of most mammalian cells, including oligodendrocytes, which are myelinating cells of the central nervous system (CNS) that support critical axonal function. Dysfunction of CNS glia is associated with aging-related white matter diseases and neurodegeneration, and ciliopathies are known to affect CNS white matter. To investigate age-related changes in ciliary profile, we examined ciliary length and frequency in the retinogeniculate pathway, a white matter tract commonly affected by diseases of aging but in which expression of cilia has not been characterized. We found expression of Arl13b, a marker of primary cilia, in a small group of Olig2-positive oligodendrocytes in the optic nerve, optic chiasm, and optic tract in young and aged C57BL/6 wild-type mice. While the ciliary length and ciliated oligodendrocyte cells were constant in young mice in the retinogeniculate pathway, there was a significant increase in ciliary length in the anterior optic nerve as compared to the aged animals. Morphometric analysis confirmed a specific increase in the ciliation rate of CC1+ /Olig2+ oligodendrocytes in aged mice compared with young mice. Thus, the prevalence of primary cilia in oligodendrocytes in the visual pathway and the age-related changes in ciliation suggest that they may play important roles in white matter and age-associated optic neuropathies.

Trans-Compartmental Regulation of Tight Junction Barrier Function

Tight junctions (TJs) are the most apical components of junctional complexes in epithelial and endothelial cells. Barrier function is one of the major functions of TJ, which restricts the ions and small water-soluble molecules from passing through the paracellular pathway. Adherens junctions (AJs) play an important role in cell-cell adhesion and cell signaling. Gap junctions (GJs) are intercellular channels regulating electrical and metabolic signals between cells. It is well known that TJ integral membrane proteins, such as claudins and occludins, are the molecular building blocks responsible for TJ barrier function. However, recent studies demonstrate that proteins of other junctional complexes can influence and regulate TJ barrier function. Therefore, the crosstalk between different cell junctions represents a common means to modulate cellular activities. In this review, we will discuss the interactions among TJ, AJ, and GJ by focusing on how AJ and GJ proteins regulate TJ barrier function in different biological systems.

Submandibular gland epithelial development and the importance of junctions

Salivary glands consist of highly specialized epithelial cells that secrete the fluid, saliva, and/or transport saliva into the oral cavity. Saliva is essential to lubricate the oral cavity for food consumption and to maintain the hygiene of the oral cavity. In this review, we will focus on the formation of the epithelial cell lineage and the cell junctions that are essential for formation of saliva and maintenance of the epithelial barrier between the ducts that transport saliva and the extracellular environment.

Cilia-associated wound repair mediated by IFT88 in retinal pigment epithelium

Primary cilia are conserved organelles that integrate extracellular cues into intracellular signals and are critical for diverse processes, including cellular development and repair responses. Deficits in ciliary function cause multisystemic human diseases known as ciliopathies. In the eye, atrophy of the retinal pigment epithelium (RPE) is a common feature of many ciliopathies. However, the roles of RPE cilia in vivo remain poorly understood. In this study, we first found that mouse RPE cells only transiently form primary cilia. We then examined the RPE in the mouse model of Bardet-Biedl Syndrome 4 (BBS4), a ciliopathy associated with retinal degeneration in humans, and found that ciliation in BBS4 mutant RPE cells is disrupted early during development. Next, using a laser-induced injury model in vivo, we found that primary cilia in RPE reassemble in response to laser injury during RPE wound healing and then rapidly disassemble after the repair is completed. Finally, we demonstrated that RPE-specific depletion of primary cilia in a conditional mouse model of cilia loss promoted wound healing and enhanced cell proliferation. In summary, our data suggest that RPE cilia contribute to both retinal development and repair and provide insights into potential therapeutic targets for more common RPE degenerative diseases.

The Role of Ectodysplasin A on the Ocular Surface Homeostasis

Ectodysplasin A (EDA), a ligand of the TNF family, plays an important role in maintaining the homeostasis of the ocular surface. EDA is necessary for the development of the meibomian gland, the lacrimal gland, as well as the proliferation and barrier function of the corneal epithelium. The mutation of EDA can induce the destruction of the ocular surface resulting in keratopathy, abnormality of the meibomian gland and maturation of the lacrimal gland. Experimental animal studies showed that a prenatal ultrasound-guided intra-amniotic injection or postnatal intravenous administration of soluble recombinant EDA protein can efficiently prevent the development of ocular surface abnormalities in EDA mutant animals. Furthermore, local application of EDA could restore the damaged ocular surface to some extent. Hence, a recombinant EDA-based therapy may serve as a novel paradigm to treat ocular surface disorders, such as meibomian gland dysfunction and corneal epithelium abnormalities.

Evaluation of Personalized Skincare Through in-silico Gene Interactive Networks and Cellular Responses to UVR and Oxidative Stress

Purpose

Personalized approaches in dermatology are designed to match the specific requirements based on the individual genetic makeup. One major factor accounting for the differences in skin phenotypes is single nucleotide polymorphism (SNP) within several genes with diverse roles that extend beyond skin tone and pigmentation. Therefore, the cellular sensitivities to the environmental stress and damage linked to extrinsic aging could also underlie the individual characteristics of the skin and dictate the unique skin care requirements. This study aimed to identify the likely biomarkers and molecular signatures expressed in skin cells of different ethnic backgrounds, which could aid further the design of personalized skin products based on specific demands.

Methods

Using data mining and in-silico modeling, the association of SNP-affected genes with three major skin types of European, Asian and African origin was analyzed and compared within the structure-function gene interaction networks. Cultured dermal fibroblasts were subsequently subjected to ultraviolet radiation and oxidative stress and analyzed for DNA damage and senescent markers. The protective applications of two cosmetic ingredients, Resveratrol and Quercetin, were validated in both cellular and in-silico models.

Results

Each skin type was characterized by the presence of SNPs in the genes controlling facultative and constitutive pigmentation, which could also underlie the major differences in responses to photodamage, such as oxidative stress, inflammation, and barrier homeostasis. Skin-type-specific dermal fibroblasts cultured in-vitro demonstrated distinctive sensitivities to ultraviolet radiation and oxidative stress, which could be modulated further by the bioactive compounds with the predicted capacities to interact with some of the genes in the in-silico models.

Conclusion

Evaluation of the SNP-affected gene networks and likely sensitivities of skin cells, defined as low threshold levels to extrinsic stress factors, can provide a valuable tool for the design and formulation of personalized skin products that match more accurately diverse ethnic backgrounds.

Extended Overview of Ocular Phenotype with Recent Advances in Hypohidrotic Ectodermal Dysplasia

The term ectodermal dysplasias (EDs) describes a heterogeneous group of inherited developmental disorders that affect several tissues of ectodermal origin. The most common form of EDs is hypohidrotic ectodermal dysplasia (HED), which is characterized by hypodontia, hypotrichosis, and partial or total eccrine sweat gland deficiency. HED is estimated to affect at least 1 in 17,000 people worldwide. Patients with HED have characteristic facies with periorbital hyperpigmentation, depressed nasal bridge, malar hypoplasia, and absent or sparse eyebrows and eyelashes. The common ocular features of HED include madarosis, trichiasis, and ocular chronic surface disease due to dry eye syndrome, which manifests clinically with discomfort, photophobia, and redness. Dry eye is common in HED and results from a combination of ocular surface defects: mucus abnormalities (abnormal conjunctival mucinous glands), aqueous tear deficiency (abnormalities in the lacrimal gland) and lipid deficiency (due to the partial or total absence of the meibomian glands; modified sebaceous glands with the tarsal plate). Sight-threatening complications result from ocular surface disease, including corneal ulceration and perforation with subsequent corneal scarring and neovascularization. Rare ocular features have been reported and include bilateral or unilateral congenital cataracts, bilateral glaucoma, chorioretinal atrophy and atresia of the nasolacrimal duct. Recognition of the ocular manifestations of HED is required to perform clinical surveillance, instigate supportive and preventative treatment, and manage ocular complications.

Sleep deprivation induces corneal epithelial progenitor cell over-expansion through disruption of redox homeostasis in the tear film

Sleep deficiency, a common public health problem, causes ocular discomfort and affects ocular surface health. However, the underlying mechanism remains unclear. Herein, we identified that short-term sleep deprivation (SD) resulted in hyperproliferation of corneal epithelial progenitor cells (CEPCs) in mice. The expression levels of p63 and Keratin 14, the biomarkers of CEPCs, were upregulated in the corneal epithelium after short-term SD. In addition, SD led to elevated levels of reactive oxygen species (ROS), and subsequent decrease in antioxidant capacity, in the tear film. Exogenous hydrogen peroxide (H₂O₂) could directly stimulate the proliferation of CEPCs in vivo and in vitro. Topical treatment of antioxidant L-glutathione preserved the over-proliferation of CEPCs and attenuated corneal epithelial defects in SD mice. Moreover, the activation of the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway is essential to ROS-stimulated cell proliferation in CEPCs. However, long-term SD ultimately led to early manifestation of limbal stem cell deficiency.

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Sleep deprivation induces the over-expansion of corneal epithelial progenitor cells (CEPCs)

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Sleep deprivation disrupts redox homeostasis in the tear film

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PI3K/AKT signaling pathway activation is essential to ROS-stimulated CEPC over-proliferation

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Topical L-glutathione treatment attenuates CEPC over-proliferation

Shhedding New Light on the Role of Hedgehog Signaling in Corneal Wound Healing

The cornea, an anterior ocular tissue that notably serves to protect the eye from external insults and refract light, requires constant epithelium renewal and efficient healing following injury to maintain ocular homeostasis. Although several key cell populations and molecular pathways implicated in corneal wound healing have already been thoroughly investigated, insufficient/impaired or excessive corneal wound healing remains a major clinical issue in ophthalmology, and new avenues of research are still needed to further improve corneal wound healing. Because of its implication in numerous cellular/tissular homeostatic processes and oxidative stress, there is growing evidence of the role of Hedgehog signaling pathway in physiological and pathological corneal wound healing. Reviewing current scientific evidence, Hedgehog signaling and its effectors participate in corneal wound healing mainly at the level of the corneal and limbal epithelium, where Sonic Hedgehog-mediated signaling promotes limbal stem cell proliferation and corneal epithelial cell proliferation and migration following corneal injury. Hedgehog signaling could also participate in corneal epithelial barrier homeostasis and in pathological corneal healing such as corneal injury-related neovascularization. By gaining a better understanding of the role of this double-edged sword in physiological and pathological corneal wound healing, fascinating new research avenues and therapeutic strategies will undoubtedly emerge.

Increased risk of chronic fatigue and hair loss following COVID-19 in individuals with hypohidrotic ectodermal dysplasia

BACKGROUND

Hypohidrotic ectodermal dysplasia (HED) is a group of genodermatoses in which deficient ectodysplasin A signalling leads to maldevelopment of skin appendages, various eccrine glands, and teeth. Individuals with HED often have disrupted epithelial barriers and, therefore, were suspected to be more susceptible to coronavirus infection.

METHODS

56 households with at least one member who had coronavirus disease of 2019 (COVID-19) were enrolled in a longitudinal study to compare the course of illness, immune responses, and long-term consequences of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection in HED patients (n = 15, age 9-52 years) and control subjects of the same age group (n = 149).

RESULTS

In 14 HED patients, mild or moderate typical COVID-19 symptoms were observed that lasted for 4-45 days. Fever during the first days sometimes required external cooling measures. The course of COVID-19 was similar to that in control subjects if patients developed antibodies blocking the SARS-CoV-2 spike protein. Five out of six HED patients with completely abrogated ectodysplasin A signalling (83%) suffered from chronic, in two cases very severe fatigue following COVID-19, while only 25% of HED patients with residual activity of this pathway and 21% of control subjects recovering from COVID-19 experienced postinfectious fatigue. Hair loss after COVID-19 was also more frequent among HED patients (64%) than in the control group (13%).

CONCLUSIONS

HED appears to be associated with an increased risk of long-term consequences of a SARS-CoV-2 infection. Preventive vaccination against COVID-19 should be recommended for individuals affected by this rare genetic disorder.

[Detection of EDA gene mutation and phenotypic analysis in patients with hypohidrotic ectodermal dysplasia]

OBJECTIVE

To detect the ectodysplasin A (EDA) gene mutation in patients with hypohidro-tic ectodermal dysplasia (HED), and to analyze the distribution pattern of missing permanent teeth and the systemic manifestation of HED patients with EDA gene mutation.

METHODS

Twelve HED families were enrolled from clinic for genetic history collection, systemic physical examination and oral examination. Peripheral blood or saliva samples were collected from the probands and the family members to extract genomic DNA. PCR amplification and Sanger sequencing were utilized to detect the EDA gene variations, which were compared with the normal sequence (NM_001399.5). The functional impact of EDA gene variants was then evaluated by functional prediction of mutation, conservation analysis and protein structure prediction. The pathogenicity of each EDA gene variation was assessed according to the stan-dards and guidelines of the American College of Medical Genetics and Genomics (ACMG). The systemic phenotype and missing permanent tooth sites of HED patients with EDA gene mutations were summarized, and the missing rate of each tooth position was analyzed and compared.

RESULTS

Eight out of twelve HED families were identified to carry EDA gene mutations, including: c.164T>C(p.Leu55Pro); c.457C>T (p.Arg153Cys); c.466C>T(p.Arg156Cys); c. 584G>A(p.Gly195Glu); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys). Among them, c.164T>C(p.Leu55Pro); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys) were novel mutations. The HED patients with EDA gene mutations in this study were all male. Our results showed that the average number of missing permanent teeth was 13.86±4.49, the average number of missing permanent teeth in the upper jaw was 13.14±5.76, the missing rate was 73.02%. And in the lower jaw, the average number of missing permanent teeth was 14.57±3.05, the missing rate was 80.95%. There was no significant difference in the number of missing teeth between the left and right sides of the permanent dentition (P>0.05). Specifi-cally, the maxillary lateral incisors, the maxillary second premolars and the mandibular lateral incisors were more likely to be missing, while the maxillary central incisors, the maxillary and mandibular first molars had higher possibility of persistence.

CONCLUSION

This study detected novel EDA gene pathogenic variants and summarized the distribution pattern of missing permanent teeth of HED patients, thus enriched the variation and phenotype spectrum of EDA gene, and provided new clinical evidence for genetic diagnosis and prenatal consultation.

Shared inflammatory and skin-specific gene signatures reveal common drivers of discoid lupus erythematosus in canines, humans and mice

Autoimmune skin diseases are complex and are thought to arise from a combination of genetics and environmental exposures, which trigger an ongoing immune response against self-antigens. Companion animals including cats and dogs are known to develop inflammatory skin conditions similar to humans and share the same environment, providing opportunities to study spontaneous disease that encompasses genetic and environmental factors with a One Health approach. A strength of comparative immunology approaches is that immune profiles may be assessed across different species to better identify shared or conserved pathways that might drive inflammation. Here, we performed a comparative study of skin from canine discoid lupus erythematosus (DLE) using NanoString nCounter technology. We compared these gene expression patterns to those of human DLE and a mouse model of cutaneous lupus. We found strong interferon signatures, with CXCL10, ISG15, and an S100 gene family member among the highest, most significant DEGs upregulated across species. Cell type analysis revealed marked T-cell and B-cell infiltration. Interestingly, canine DLE samples also recapitulated downregulated skin homeostatic genes observed in human DLE. We conclude that spontaneous DLE in dogs captures many features that are present in human disease and may serve as a more complete model for conducting further genomic and/or transcriptomic studies.

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Canine DLE lesions express known drivers of pathogenesis including CXCL10, IFNG, FAS.

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Enrichment of key cell types, including T, B, NK cells, is observed in canine DLE.

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Canine, mouse and human DLE share similar proinflammatory profiles.

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Canine DLE exhibits downregulated skin homeostatic and immune regulatory genes.

Fluid-electrolyte homeostasis requires histone deacetylase function

Histone deacetylase (HDAC) enzymes regulate transcription through epigenetic modification of chromatin structure, but their specific functions in the kidney remain elusive. We discovered that the human kidney expresses class I HDACs. Kidney medulla-specific inhibition of class I HDACs in the rat during high-salt feeding results in hypertension, polyuria, hypokalemia, and nitric oxide deficiency. Three new inducible murine models were used to determine that HDAC1 and HDAC2 in the kidney epithelium are necessary for maintaining epithelial integrity and maintaining fluid-electrolyte balance during increased dietary sodium intake. Moreover, single-nucleus RNA-sequencing determined that epithelial HDAC1 and HDAC2 are necessary for expression of many sodium or water transporters and channels. In performing a systematic review and meta-analysis of serious adverse events associated with clinical HDAC inhibitor use, we found that HDAC inhibitors increased the odds ratio of experiencing fluid-electrolyte disorders, such as hypokalemia. This study provides insight on the mechanisms of potential serious adverse events with HDAC inhibitors, which may be fatal to critically ill patients. In conclusion, kidney tubular HDACs provide a link between the environment, such as consumption of high-salt diets, and regulation of homeostatic mechanisms to remain in fluid-electrolyte balance.

Fetal gene therapy and pharmacotherapy to treat congenital hearing loss and vestibular dysfunction

Disabling hearing loss is expected to affect over 900 million people worldwide by 2050. The World Health Organization estimates that the annual economic impact of hearing loss globally is US$ 750 billion. The inability to hear may complicate effective interpersonal communication and negatively impact personal and professional relationships. Recent advances in the genetic diagnosis of inner ear disease have keenly focused attention on strategies to restore hearing and balance in individuals with defined gene mutations. Mouse models of human hearing loss serve as the primary approach to test gene therapies and pharmacotherapies. The goal of this review is to articulate the rationale for fetal gene therapy and pharmacotherapy to treat congenital hearing loss and vestibular dysfunction. The differential onset of hearing in mice and humans suggests that a prenatal window of therapeutic efficacy in humans may be optimal to restore sensory function. Mouse studies demonstrating the utility of early fetal intervention in the inner ear show promise. We focus on the modulation of gene expression through two strategies that have successfully treated deafness in animal models and have had clinical success for other conditions in humans: gene replacement and antisense oligonucleotide-mediated modulation of gene expression. The recent establishment of effective therapies targeting the juvenile and adult mouse provide informative counterexamples where intervention in the maturing and fully functional mouse inner ear may be effective. Distillation of the current literature leads to the conclusion that novel therapeutic strategies to treat genetic deafness and imbalance will soon translate to clinical trials.

Ectodysplasin-A signaling is a key integrator in the lacrimal gland-cornea feedback loop

A lack of ectodysplasin-A (Eda) signaling leads to dry eye symptoms, which have so far only been associated with altered Meibomian glands. Here, we used loss-of-function (Eda ^-/-) mutant mice to unravel the impact of Eda signaling on lacrimal gland formation, maturation and subsequent physiological function. Our study demonstrates that Eda activity is dispensable during lacrimal gland embryonic development. However, using a transcriptomic approach, we show that the Eda pathway is necessary for proper cell terminal differentiation in lacrimal gland epithelium and correlated with modified expression of secreted factors commonly found in the tear film. Finally, we discovered that lacrimal glands present a bilateral reduction of Eda signaling activity in response to unilateral corneal injury. This observation hints towards a role for the Eda pathway in controlling the switch from basal to reflex tears, to support corneal wound healing. Collectively, our data suggest a crucial implication of Eda signaling in the cornea-lacrimal gland feedback loop, both in physiological and pathophysiological conditions. Our findings demonstrate that Eda downstream targets could help alleviate dry eye symptoms.