Understanding the pathogenesis of recessive dystrophic epidermolysis bullosa squamous cell carcinoma

Melanocortin therapies to resolve fibroblast-mediated diseases

Stromal cells have emerged as central drivers in multiple and diverse diseases, and consequently, as potential new cellular targets for the development of novel therapeutic strategies. In this review we revise the main roles of fibroblasts, not only as structural cells but also as players and regulators of immune responses. Important aspects like fibroblast heterogeneity, functional specialization and cellular plasticity are also discussed as well as the implications that these aspects may have in disease and in the design of novel therapeutics. An extensive revision of the actions of fibroblasts on different conditions uncovers the existence of numerous diseases in which this cell type plays a pathogenic role, either due to an exacerbation of their 'structural' side, or a dysregulation of their 'immune side'. In both cases, opportunities for the development of innovative therapeutic approaches exist. In this regard, here we revise the existing evidence pointing at the melanocortin pathway as a potential new strategy for the treatment and management of diseases mediated by aberrantly activated fibroblasts, including scleroderma or rheumatoid arthritis. This evidence derives from studies involving models of in vitro primary fibroblasts, in vivo models of disease as well as ongoing human clinical trials. Melanocortin drugs, which are pro-resolving mediators, have shown ability to reduce collagen deposition, activation of myofibroblasts, reduction of pro-inflammatory mediators and reduced scar formation. Here we also discuss existing challenges, both in approaching fibroblasts as therapeutic targets, and in the development of novel melanocortin drug candidates, that may help advance the field and deliver new medicines for the management of diseases with high medical needs.

Reverse oblique proximal femoral fracture in dystrophic epidermolysis bullosa: challenges and recommendations

A 35-year-old woman attended the emergency department after sustaining a reverse oblique proximal femur fracture, which was amenable to intramedullary nailing. Her presentation was complicated by a background of severe generalised recessive dystrophic epidermolysis bullosa, with extensive blistering of most of her skin, including the area over the standard surgical incision sites. For the successful management of this case, extensive input from the multidisciplinary team was required, with the team facing several challenges. The whole approach to nursing and surgical management (anaesthesia, positioning, fracture reduction and wound care) had to be modified, taking great care to protect the skin at any cost, therefore reducing the risk of a surgical site infection which would be catastrophic. The management of this patient can set a framework that can be followed in similar cases, aiming for a favourable outcome of such challenging, rare conditions.

Translational perspectives to treat Epidermolysis bullosa-Where do we stand?

Epidermolysis bullosa (EB) is the prototypical example of genetic skin fragility disorders. Genotypic heterogeneity, modifier genes, epigenetic, biochemical and environmental factors alter and determine pathogenic traits and, ultimately, the wide and striking phenotypic variability in EB. Besides the primary structural-functional defect, chronic tissue damage with induction and dysregulation of inflammatory pathways is a common pathogenic mechanism in EB. In localized variants, the inflammatory aberrations may mainly affect the micromilieu of lesional skin, while a systemic inflammatory response was shown to contribute to the systemic morbidity in severe EB subtypes with extensive cutaneous involvement. Our continued understanding of the pathophysiology of EB, as well as advances in molecular technologies, has paved the way for translational therapeutic approaches. The spectrum comprises of corrective and symptom-relieving therapies that include innovative therapeutic options garnered from the bench, repurposed drugs approved for other diseases, as well as strategies for gene-, protein- and cell-based therapies. Immunological traits further define new targets of therapy, aimed at improving skin barrier restoration, microbial surveillance and infection control, wound healing and anti-neoplastic effects. Clinical availability and feasibility of these approaches for all EB patients and subtypes are currently limited, reflecting issues of efficacy, specificity, tolerability and safety. A multistep targeting approach and highly individualized, risk-stratified combinatory treatment plans will thus be essential for sustained efficacy and improved overall quality of life in EB.

A multitask clustering approach for single-cell RNA-seq analysis in Recessive Dystrophic Epidermolysis Bullosa

Single-cell RNA sequencing (scRNA-seq) has been widely applied to discover new cell types by detecting sub-populations in a heterogeneous group of cells. Since scRNA-seq experiments have lower read coverage/tag counts and introduce more technical biases compared to bulk RNA-seq experiments, the limited number of sampled cells combined with the experimental biases and other dataset specific variations presents a challenge to cross-dataset analysis and discovery of relevant biological variations across multiple cell populations. In this paper, we introduce a method of variance-driven multitask clustering of single-cell RNA-seq data (scVDMC) that utilizes multiple single-cell populations from biological replicates or different samples. scVDMC clusters single cells in multiple scRNA-seq experiments of similar cell types and markers but varying expression patterns such that the scRNA-seq data are better integrated than typical pooled analyses which only increase the sample size. By controlling the variance among the cell clusters within each dataset and across all the datasets, scVDMC detects cell sub-populations in each individual experiment with shared cell-type markers but varying cluster centers among all the experiments. Applied to two real scRNA-seq datasets with several replicates and one large-scale droplet-based dataset on three patient samples, scVDMC more accurately detected cell populations and known cell markers than pooled clustering and other recently proposed scRNA-seq clustering methods. In the case study applied to in-house Recessive Dystrophic Epidermolysis Bullosa (RDEB) scRNA-seq data, scVDMC revealed several new cell types and unknown markers validated by flow cytometry. MATLAB/Octave code available at https://github.com/kuanglab/scVDMC.

scRNA-seq enables detailed profiling of heterogeneous cell populations and can be used to reveal lineage relationships or discover new cell types. In the literature, there has been little effort directed towards developing computational methods for cross-population transcriptome analysis of multiple single-cell populations. The cross-cell-population clustering problem is different from the traditional clustering problem because single-cell populations can be collected from different patients, different samples of a tissue, or different experimental replicates. The accompanying biological and technical variation tends to dominate the signals for clustering the pooled single cells from the multiple populations. In this work, we have developed a multitask clustering method to address the cross-population clustering problem. The method simultaneously clusters each individual cell population and controls variance among the cell-type cluster centers within each cell population and across the cell populations. We demonstrate that our multitask clustering method significantly improves clustering accuracy and marker discovery in three public scRNA-seq datasets and also apply the method to an in-house Recessive Dystrophic Epidermolysis Bullosa (RDEB) dataset. Our results make it evident that multitask clustering is a promising new approach for cross-population analysis of scRNA-seq data.

Wound culture isolated antibiograms and caregiver-reported skin care practices in children with epidermolysis bullosa

BACKGROUND/OBJECTIVES

Many patients with epidermolysis bullosa (EB) require intensive daily wound care and individualized treatment plans. Understanding patient's home skin care routines and emerging antibiotic resistance patterns in EB wounds is necessary to optimize treatment recommendations. The objective was to identify patterns of antimicrobial resistance in EB wounds and characterize patient's home practices of skin care and bathing.

METHODS

This was an observational study of 23 children with EB at an outpatient pediatric dermatology practice in New York City from 2012 to 2014. Information on individual bathing and skin care practices and wound cultures was collected as part of routine examinations and an institutional review board-approved antibiogram protocol.

RESULTS

Sixty wound cultures were collected from 23 patients. Eleven organisms were isolated, most commonly methicillin-susceptible Staphylococcus aureus, methicillin-resistant S. aureus, Streptococcus species, and Pseudomonas aeruginosa. Six patients (26%) were colonized with methicillin-resistant S. aureus. Over the course of the study, 13 patients (56%) were found to have mupirocin-resistant S. aureus. More than half of participants reported mupirocin or bacitracin use. Fewer than half indicated that they regularly used dilute bleach or dilute vinegar as part of their bathing routine.

CONCLUSION

Numerous organisms, including resistant bacteria, are known to colonize the wounds of individuals with EB. Mupirocin resistance was prevalent and more than half of the participants reported its use. Testing for mupirocin resistance may be considered for certain patients. These observations may help guide questions for future longitudinal multicenter studies with the goal of optimizing EB wound care recommendations.

Rapid generation of Col7a1-/- mouse model of recessive dystrophic epidermolysis bullosa and partial rescue via immunosuppressive dermal mesenchymal stem cells

Recessive dystrophic epidermolysis bullosa (RDEB) is a debilitating and ultimately lethal blistering disease caused by mutations to the Col7a1 gene. Development of novel cell therapies for the treatment of RDEB would be fostered by having immunodeficient mouse models able to accept human cell grafts; however, immunodeficient models of many genodermatoses such as RDEB are lacking. To overcome this limitation, we combined the clustered regularly interspaced short palindromic repeats and associated nuclease (CRISPR/Cas9) system with microinjection into NOD/SCID IL2rγc^null (NSG) embryos to rapidly develop an immunodeficient Col7a1^-/- mouse model of RDEB. Through dose optimization, we achieve F0 biallelic knockout efficiencies exceeding 80%, allowing us to quickly generate large numbers of RDEB NSG mice for experimental use. Using this strategy, we clearly demonstrate important strain-specific differences in RDEB pathology that could underlie discordant results observed between independent studies and establish the utility of this system in proof-of-concept human cellular transplantation experiments. Importantly, we uncover the ability of a recently identified skin resident immunomodulatory dermal mesenchymal stem cell marked by ABCB5 to reduce RDEB pathology and markedly extend the lifespan of RDEB NSG mice via reduced skin infiltration of inflammatory myeloid derivatives.

Pseudosyndactyly - an inflammatory and fibrotic wound healing disorder in recessive dystrophic epidermolysis bullosa

BACKGROUND

A genetic blistering skin disease, recessive dystrophic epidermolysis bullosa (RDEB), is marked by severe wound healing defects and finger contractures. The purpose of this investigation was to elucidate the mechanisms of impaired wound healing and pseudosyndactyly occurring in RDEB patients by studying the role of known inflammation and fibrosis markers in RDEB pseudosyndactyly tissue.

PATIENTS AND METHODS

We studied the expression of the fibrosis and/or inflammation markers tenascin-C, α-smooth muscle actin, transforming growth factor-β1, interleukin-1β, and interleukin-6 in scarring and nonscarring tissue from healthy donors and RDEB patients by semiquantitative real time-PCR and, where applicable, by immunoblots. Furthermore, the distribution pattern of α-smooth muscle actin and tenascin-C were assessed by immunofluorescence microscopy.

RESULTS

Based on mRNA and protein analysis, we found upregulation of tenascin-C, interleukin-1β, and interleukin-6 - but not of transforming growth factor-β1 - in recessive dystrophic epidermolysis bullosa scar samples taken from pseudosyndactyly hands. Unexpectedly, α-smooth muscle actin was not upregulated.

CONCLUSIONS

Our results confirm inflammation and fibrosis in recessive dystrophic epidermolysis bullosa, especially in scars, suggesting major roles for these processes in pseudosyndactyly. Our data therefore suggests the potential use of antiinflammatory and antifibrotic drugs in the prevention of pseudosyndactyly.

Molecular pathology of the basement membrane zone in heritable blistering diseases:: The paradigm of epidermolysis bullosa

Epidermolysis bullosa (EB), a phenotypically heterogeneous group of skin fragility disorders, is characterized by blistering and erosions with considerable morbidity and mortality. Mutations in as many as 18 distinct genes expressed at the cutaneous basement membrane zone have been shown to be associated with the blistering phenotype, attesting to the role of the corresponding proteins in providing stable association of the epidermis to the dermis through adhesion at the dermo-epidermal basement membrane zone. Thus, different forms of EB have been highly instructive in providing information on the physiological functions of these proteins as integral components of the supramolecular adhesion complexes. In addition, precise information of the underlying genes and distinct mutations in families with EB has been helpful in subclassification of the disease with prognostic implications, as well as for prenatal testing and preimplantation genetic diagnosis. Furthermore, knowledge of the types of mutations is a prerequisite for application of allele-specific treatment approaches that have been recently developed, including read-through of premature termination codon mutations and chaperone-facilitated intracellular transport of conformationally altered proteins to proper physiologic subcellular location. Collectively, EB serves as a paradigm of heritable skin diseases in which significant progress has been made in identifying the underlying genetic bases and associated aberrant pathways leading from mutations to the phenotype, thus allowing application of precision medicine for this, currently intractable group of diseases.

IL-13 from intraepithelial lymphocytes regulates tissue homeostasis and protects against carcinogenesis in the skin

The skin is under constant renewal and exposure to environmental challenges. How homeostasis is maintained alongside protective mechanisms against damage is unclear. Among the basal epithelial cells (ECs) is a population of resident intraepithelial lymphocytes (IELs) that provide host-protective immune surveillance. Here we show that IELs cross-communicate with ECs via the production of IL-13. Skin ECs are activated by IEL-derived IL-13, enabling a canonical EC stress response. In the absence of IL-13, or canonical IEL, the skin has decreased ability to repair its barrier and increased susceptibility to cutaneous carcinogenesis. IL-13 controls the rate of EC movement through the epidermis, which might explain the importance of IL-13 for epidermal integrity and its suppressive effect on skin carcinogenesis. These findings show that IL-13 acts as a molecular bridge between IELs and ECs, and reveal a critical host-defensive role for type-2 immunity in regulating EC tissue homeostasis and carcinogenesis.

Transcriptome and ultrastructural changes in dystrophic Epidermolysis bullosa resemble skin aging

The aging process of skin has been investigated recently with respect to mitochondrial function and oxidative stress. We have here observed striking phenotypic and clinical similarity between skin aging and recessive dystrophic Epidermolysis bullosa (RDEB), which is caused by recessive mutations in the gene coding for collagen VII, COL7A1. Ultrastructural changes, defects in wound healing, and inflammation markers are in part shared with aged skin. We have here compared the skin transcriptomes of young adults suffering from RDEB with that of sex‐ and age‐matched healthy probands. In parallel we have compared the skin transcriptome of healthy young adults with that of elderly healthy donors. Quite surprisingly, there was a large overlap of the two gene lists that concerned a limited number of functional protein families. Most prominent among the proteins found are a number of proteins of the cornified envelope or proteins mechanistically involved in cornification and other skin proteins. Further, the overlap list contains a large number of genes with a known role in inflammation. We are documenting some of the most prominent ultrastructural and protein changes by immunofluorescence analysis of skin sections from patients, old individuals, and healthy controls.

From marrow to matrix: novel gene and cell therapies for epidermolysis bullosa

Epidermolysis bullosa encompasses a group of inherited connective tissue disorders that range from mild to lethal. There is no cure, and current treatment is limited to palliative care that is largely ineffective in treating the systemic, life-threatening pathology associated with the most severe forms of the disease. Although allogeneic cell- and protein-based therapies have shown promise, both novel and combinatorial approaches will undoubtedly be required to totally alleviate the disorder. Progress in the development of next-generation therapies that synergize targeted gene-correction and induced pluripotent stem cell technologies offers exciting prospects for personalized, off-the-shelf treatment options that could avoid many of the limitations associated with current allogeneic cell-based therapies. Although no single therapeutic avenue has achieved complete success, each has substantially increased our collective understanding of the complex biology underlying the disease, both providing mechanistic insights and uncovering new hurdles that must be overcome.

Beneficial autoimmunity at body surfaces - immune surveillance and rapid type 2 immunity regulate tissue homeostasis and cancer

Epithelial cells (ECs) line body surface tissues and provide a physicochemical barrier to the external environment. Frequent microbial and non-microbial challenges such as those imposed by mechanical disruption, injury or exposure to noxious environmental substances including chemicals, carcinogens, ultraviolet-irradiation, or toxins cause activation of ECs with release of cytokines and chemokines as well as alterations in the expression of cell-surface ligands. Such display of epithelial stress is rapidly sensed by tissue-resident immunocytes, which can directly interact with self-moieties on ECs and initiate both local and systemic immune responses. ECs are thus key drivers of immune surveillance at body surface tissues. However, ECs have a propensity to drive type 2 immunity (rather than type 1) upon non-invasive challenge or stress – a type of immunity whose regulation and function still remain enigmatic. Here, we review the induction and possible role of type 2 immunity in epithelial tissues and propose that rapid immune surveillance and type 2 immunity are key regulators of tissue homeostasis and carcinogenesis.

A new component of the Fraser complex

In embryos, the Fraser Complex (FC) mediates epithelial-connective tissue interactions. Loss of expression of FC components leads to Fraser Syndrome (FS) in which cohesion of epithelial tissues and stroma is perturbed. Using zebrafish, Richardson et al (in this issue) identified the protein AMACO in the FC. We discuss the utility of zebrafish in determining FC functions and identifying FS targets.

Advances in understanding and treating dystrophic epidermolysis bullosa

Epidermolysis bullosa is a group of inherited disorders that can be both systemic and life-threatening. Standard treatments for the most severe forms of this disorder, typically limited to palliative care, are ineffective in reducing the morbidity and mortality due to complications of the disease. Emerging therapies—such as the use of allogeneic cellular therapy, gene therapy, and protein therapy—have all shown promise, but it is likely that several approaches will need to be combined to realize a cure. For recessive dystrophic epidermolysis bullosa, each particular therapeutic approach has added to our understanding of type VII collagen (C7) function and the basic biology surrounding the disease. The efficacy of these therapies and the mechanisms by which they function also give us insight into developing future strategies for treating this and other extracellular matrix disorders.

Type VII collagen regulates expression of OATP1B3, promotes front-to-rear polarity and increases structural organisation in 3D spheroid cultures of RDEB tumour keratinocytes

Type VII collagen is the main component of anchoring fibrils, structures that are integral to basement membrane homeostasis in skin. Mutations in the gene encoding type VII collagen COL7A1 cause recessive dystrophic epidermolysis bullosa (RDEB) an inherited skin blistering condition complicated by frequent aggressive cutaneous squamous cell carcinoma (cSCC). OATP1B3, which is encoded by the gene SLCO1B3, is a member of the OATP (organic anion transporting polypeptide) superfamily responsible for transporting a wide range of endogenous and xenobiotic compounds. OATP1B3 expression is limited to the liver in healthy tissues, but is frequently detected in multiple cancer types and is reported to be associated with differing clinical outcome. The mechanism and functional significance of tumour-specific expression of OATP1B3 has yet to be determined. Here, we identify SLCO1B3 expression in tumour keratinocytes isolated from RDEB and UV-induced cSCC and demonstrate that SLCO1B3 expression and promoter activity are modulated by type VII collagen. We show that reduction of SLCO1B3 expression upon expression of full-length type VII collagen in RDEB cSCC coincides with acquisition of front-to-rear polarity and increased organisation of 3D spheroid cultures. In addition, we show that type VII collagen positively regulates the abundance of markers implicated in cellular polarity, namely ELMO2, PAR3, E-cadherin, B-catenin, ITGA6 and Ln332.

Cutaneous squamous cell carcinoma developing from recessive dystrophic epidermolysis bullosa: a case report and an immunohistochemical study

We describe a 49-year-old Japanese woman with cutaneous squamous cell carcinoma (SCC) developing from recessive dystrophic epidermolysis bullosa (RDEB). Interestingly, immunohistochemical staining revealed dense infiltration of CD163⁺ M2 macrophages and numerous Foxp3⁺ regulatory T cells (Tregs) around the tumor. Since the contribution of immunosuppressive factors (e.g. TGFβ) to the carcinogenesis of SCC from RDEB was recently reported, our present findings suggest one of the possible contributions of immunosuppressive cells, such as CD163⁺ M2 macrophages and Tregs, to the carcinogenesis of SCC from RDEB.

Fibroblast-derived dermal matrix drives development of aggressive cutaneous squamous cell carcinoma in patients with recessive dystrophic epidermolysis bullosa

Patients with the genetic skin blistering disease recessive dystrophic epidermolysis bullosa (RDEB) develop aggressive cutaneous squamous cell carcinoma (cSCC). Metastasis leading to mortality is greater in RDEB than in other patient groups with cSCC. Here we investigate the dermal component in RDEB using mRNA expression profiling to compare cultured fibroblasts isolated from individuals without cSCC and directly from tumor matrix in RDEB and non-RDEB samples. Although gene expression of RDEB normal skin fibroblasts resembled that of cancer-associated fibroblasts, RDEB cancer-associated fibroblasts exhibited a distinct and divergent gene expression profile, with a large proportion of the differentially expressed genes involved in matrix and cell adhesion. RDEB cancer-associated fibroblasts conferred increased adhesion and invasion to tumor and nontumor keratinocytes. Reduction of COL7A1, the defective gene in RDEB, in normal dermal fibroblasts led to increased type XII collagen, thrombospondin-1, and Wnt-5A, while reexpression of wild type COL7A1 in RDEB fibroblasts decreased type XII collagen, thrombospondin-1, and Wnt-5A expression, reduced tumor cell invasion in organotypic culture, and restricted tumor growth in vivo. Overall, our findings show that matrix composition in patients with RDEB is a permissive environment for tumor development, and type VII collagen directly regulates the composition of matrix proteins secreted by dermal and cancer-associated fibroblasts.

Epithelial stem cells, wound healing and cancer

It is well established that tissue repair depends on stem cells and that chronic wounds predispose to tumour formation. However, the association between stem cells, wound healing and cancer is poorly understood. Lineage tracing has now shown how stem cells are mobilized to repair skin wounds and how they contribute to skin tumour development. The signalling pathways, including WNT and Hedgehog, that control stem cell behaviour during wound healing are also implicated in tumour formation. Furthermore, tumorigenesis and wound repair both depend on communication between epithelial cells, mesenchymal cells and bone marrow-derived cells. These studies suggest ways to harness stem cells for wound repair while minimizing cancer risk.