Therapies for genetic extracellular matrix diseases of the skin

Gene-edited cells: novel allogeneic gene/cell therapy for epidermolysis bullosa

Epidermolysis bullosa (EB) is a group of rare genetic skin fragility disorders, which are hereditary. These disorders are associated with mutations in at least 16 genes that encode components of the epidermal adhesion complex. Currently, there are no effective treatments for this disorder. All current treatment approaches focus on topical treatments to prevent complications and infections. In recent years, significant progress has been achieved in the treatment of the severe genetic skin blistering condition known as EB through preclinical and clinical advancements. Promising developments have emerged in the areas of protein and cell therapies, such as allogeneic stem cell transplantation; in addition, RNA-based therapies and gene therapy approaches have also become a reality. Stem cells obtained from embryonic or adult tissues, including the skin, are undifferentiated cells with the ability to generate, maintain, and replace fully developed cells and tissues. Recent advancements in preclinical and clinical research have significantly enhanced stem cell therapy, presenting a promising treatment option for various diseases that are not effectively addressed by current medical treatments. Different types of stem cells such as primarily hematopoietic and mesenchymal, obtained from the patient or from a donor, have been utilized to treat severe forms of diseases, each with some beneficial effects. In addition, extensive research has shown that gene transfer methods targeting allogeneic and autologous epidermal stem cells to replace or correct the defective gene are promising. These methods can regenerate and restore the adhesion of primary keratinocytes in EB patients. The long-term treatment of skin lesions in a small number of patients has shown promising results through the transplantation of skin grafts produced from gene-corrected autologous epidermal stem cells. This article attempts to summarize the current situation, potential development prospects, and some of the challenges related to the cell therapy approach for EB treatment.

Mechanotransduction through hemidesmosomes during aging and longevity

Hemidesmosomes are structural protein complexes localized at the interface of tissues with high mechanical demand and shear forces. Beyond tissue anchoring, hemidesmosomes have emerged as force-modulating structures important for translating mechanical cues into biochemical and transcriptional adaptation (i.e. mechanotransduction) across tissues. Here, we discuss the recent insights into the roles of hemidesmosomes in age-related tissue regeneration and aging in C. elegans, mice and humans. We highlight the emerging concept of preserved dynamic mechanoregulation of hemidesmosomes in tissue maintenance and healthy aging.

10 years of extracellular matrix proteomics: Accomplishments, challenges, and future perspectives

The extracellular matrix (ECM) is a complex assembly of hundreds of proteins forming the architectural scaffold of multicellular organisms. In addition to its structural role, the ECM conveys signals orchestrating cellular phenotypes. Alterations of ECM composition, abundance, structure, or mechanics, have been linked to diseases and disorders affecting all physiological systems, including fibrosis and cancer. Deciphering the protein composition of the ECM and how it changes in pathophysiological contexts is thus the first step toward understanding the roles of the ECM in health and disease and toward the development of therapeutic strategies to correct disease-causing ECM alterations. Potentially, the ECM also represents a vast, yet untapped reservoir of disease biomarkers. ECM proteins are characterized by unique biochemical properties that have hindered their study: they are large, heavily and uniquely post-translationally modified, and highly insoluble. Overcoming these challenges, we and others have devised mass-spectrometry-based proteomic approaches to define the ECM composition, or "matrisome", of tissues. This review provides a historical overview of ECM proteomics research and presents the latest advances that now allow the profiling of the ECM of healthy and diseased tissues. The second part highlights recent examples illustrating how ECM proteomics has emerged as a powerful discovery pipeline to identify prognostic cancer biomarkers. The third part discusses remaining challenges limiting our ability to translate findings to clinical application and proposes approaches to overcome them. Last, the review introduces readers to resources available to facilitate the interpretation of ECM proteomics datasets. The ECM was once thought to be impenetrable. MS-based proteomics has proven to be a powerful tool to decode the ECM. In light of the progress made over the past decade, there are reasons to believe that the in-depth exploration of the matrisome is within reach and that we may soon witness the first translational application of ECM proteomics.

Increased abundance of Cbl E3 ligases alters PDGFR signaling in recessive dystrophic epidermolysis bullosa

In recessive dystrophic epidermolysis bullosa (RDEB), loss of collagen VII, the main component of anchoring fibrils critical for epidermal-dermal cohesion, affects several intracellular signaling pathways and leads to impaired wound healing and fibrosis. In skin fibroblasts, wound healing is also affected by platelet-derived growth factor receptor (PDGFR) signaling. To study a potential effect of loss of collagen VII on PDGFR signaling we performed unbiased disease phosphoproteomics. Whereas RDEB fibroblasts exhibited an overall weaker response to PDGF, Cbl E3 ubiquitin ligases, negative regulators of growth factor signaling, were stronger phosphorylated. This increase in phosphorylation was linked to higher Cbl mRNA and protein levels due to increased TGFβ signaling in RDEB. In turn, increased Cbl levels led to increased PDGFR ubiquitination, internalization, and degradation negatively affecting MAPK and AKT downstream signaling pathways. Thus, our results indicate that elevated TGFβ signaling leads to an attenuated response to growth factors, which contributes to impaired dermal wound healing in RDEB.

Distinct contributions of meprins to skin regeneration after injury - Meprin α a physiological processer of pro-collagen VII

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Meprins subtly support epidermal and dermal skin wound healing.

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Loss of both meprins reduces re-epithelialization and wound macrophage abundance.

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Meprin α is a physiological maturing proteinase of collagen VII.

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Meprins are reduced in recessive dystrophic epidermolysis bullosa skin.

Astacin-like proteinases (ALPs) are regulators of tissue and extracellular matrix (ECM) homeostasis. They convey this property through their ability to convert ECM protein pro-forms to functional mature proteins and by regulating the bioavailability of growth factors that stimulate ECM synthesis. The most studied ALPs in this context are the BMP-1/tolloid-like proteinases. The other subclass of ALPs in vertebrates – the meprins, comprised of meprin α and meprin β – are emerging as regulators of tissue and ECM homeostasis but have so far been only limitedly investigated. Here, we functionally assessed the roles of meprins in skin wound healing using mice genetically deficient in one or both meprins. Meprin deficiency did not change the course of macroscopic wound closure. However, subtle but distinct contributions of meprins to the healing process and dermal homeostasis were observed. Loss of both meprins delayed re-epithelialization and reduced macrophage infiltration. Abnormal dermal healing and ECM regeneration was observed in meprin deficient wounds. Our analyses also revealed meprin α as one proteinase responsible for maturation of pro-collagen VII to anchoring fibril-forming-competent collagen VII in vivo. Collectively, our study identifies meprins as subtle players in skin wound healing.

Oleogel Formulations for the Topical Delivery of Betulin and Lupeol in Skin Injuries-Preparation, Physicochemical Characterization, and Pharmaco-Toxicological Evaluation

The skin integrity is essential due to its pivotal role as a biological barrier against external noxious factors. Pentacyclic triterpenes stand as valuable plant-derived natural compounds in the treatment of skin injuries due to their anti-inflammatory, antioxidant, antimicrobial, and healing properties. Consequently, the primary aim of the current investigation was the development as well as the physicochemical and pharmaco-toxicological characterization of betulin- and lupeol-based oleogels (Bet OG and Lup OG) for topical application in skin injuries. The results revealed suitable pH as well as organoleptic, rheological, and textural properties. The penetration and permeation of Bet and Lup oleogels through porcine ear skin as well as the retention of both oleogels in the skin were demonstrated through ex vivo studies. In vitro, Bet OG and Lup OG showed good biocompatibility on HaCaT human immortalized cells. Moreover, Bet OG exerted a potent wound-healing property by stimulating the migration of the HaCaT cells. The in ovo results demonstrated the non-irritative potential of the developed formulations. Additionally, the undertaken in vivo investigation indicated a positive effect of oleogels treatment on skin parameters by increasing skin hydration and decreasing erythema. In conclusion, oleogel formulations are ideal for the local delivery of betulin and lupeol in skin disorders.

Notch-ing up knowledge on molecular mechanisms of skin fibrosis: focus on the multifaceted Notch signalling pathway

Fibrosis can be defined as an excessive and deregulated deposition of extracellular matrix proteins, causing loss of physiological architecture and dysfunction of different tissues and organs. In the skin, fibrosis represents the hallmark of several acquired (e.g. systemic sclerosis and hypertrophic scars) and inherited (i.e. dystrophic epidermolysis bullosa) diseases. A complex series of interactions among a variety of cellular types and a wide range of molecular players drive the fibrogenic process, often in a context-dependent manner. However, the pathogenetic mechanisms leading to skin fibrosis are not completely elucidated. In this scenario, an increasing body of evidence has recently disclosed the involvement of Notch signalling cascade in fibrosis of the skin and other organs. Despite its apparent simplicity, Notch represents one of the most multifaceted, strictly regulated and intricate pathways with still unknown features both in health and disease conditions. Starting from the most recent advances in Notch activation and regulation, this review focuses on the pro-fibrotic function of Notch pathway in fibroproliferative skin disorders describing molecular networks, interplay with other pro-fibrotic molecules and pathways, including the transforming growth factor-β1, and therapeutic strategies under development.

Exposed CendR Domain in Homing Peptide Yields Skin-Targeted Therapeutic in Epidermolysis Bullosa

Systemic skin-selective therapeutics would be a major advancement in the treatment of diseases affecting the entire skin, such as recessive dystrophic epidermolysis bullosa (RDEB), which is caused by mutations in the COL7A1 gene and manifests in transforming growth factor-β (TGF-β)-driven fibrosis and malignant transformation. Homing peptides containing a C-terminal R/KXXR/K motif (C-end rule [CendR] sequence) activate an extravasation and tissue penetration pathway for tumor-specific drug delivery. We have previously described a homing peptide CRKDKC (CRK) that contains a cryptic CendR motif and homes to angiogenic blood vessels in wounds and tumors, but it cannot penetrate cells or tissues. In this study, we demonstrate that removal of the cysteine from CRK to expose the CendR sequence confers the peptide novel ability to home to normal skin. Fusion of the truncated CRK (tCRK) peptide to the C terminus of an extracellular matrix protein decorin (DCN), a natural TGF-β inhibitor, resulted in a skin-homing therapeutic molecule (DCN-tCRK). Systemic DCN-tCRK administration in RDEB mice led to inhibition of TGF-β signaling in the skin and significant improvement in the survival of RDEB mice. These results suggest that DCN-tCRK has the potential to be utilized as a novel therapeutic compound for the treatment of dermatological diseases such as RDEB.

Skin proteomics - analysis of the extracellular matrix in health and disease

INTRODUCTION

The skin protects the human body from external insults and regulates water and temperature homeostasis. A highly developed extracellular matrix (ECM) supports the skin and instructs its cell functions. Reduced functionality of the ECM is often associated with skin diseases that cause physical impairment and also have implications on social interactions and quality of life of affected individuals.

AREAS COVERED

With a focus on the skin ECM we discuss how mass spectrometry (MS)-based proteomic approaches first contributed to establishing skin protein inventories and then facilitated elucidation of molecular functions and disease mechanisms.

EXPERT OPINION

MS-based proteomic approaches have significantly contributed to our understanding of skin pathophysiology, but also revealed the challenges in assessing the skin ECM. The numerous posttranslational modifications of ECM proteins, like glycosylation, crosslinking, oxidation, and proteolytic maturation in disease settings can be difficult to tackle and remain understudied. Increased ease of handling of LC-MS/MS systems and automated/streamlined data analysis pipelines together with the accompanying increased usage of LC-MS/MS approaches will ensure that in the coming years MS-based proteomic approaches will continue to play a vital part in skin disease research. They will facilitate the elucidation of molecular disease mechanisms and, ultimately, identification of new druggable targets.

Bovine Decellularized Amniotic Membrane: Extracellular Matrix as Scaffold for Mammalian Skin

Decellularized membranes (DM) were obtained from bovine amniotic membranes (BAM) using four different decellularization protocols, based on physical, chemical, and mechanical treatment. The new material was used as a biological scaffold for in vitro skin cell culture. The DM were characterized using hematoxylin-eosin assay, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR-ATR), and differential scanning calorimetry (DSC). The in vitro cytotoxicity of DM was evaluated using MTT. The efficacy of decellularization process was assessed through DNA quantification and electrophoresis. All the used protocols showed a high effectiveness in terms of elimination of native cells, confirmed by DNA extraction and quantification, electrophoresis, and SEM, although protocol IV removes the cellular contents and preserve the native extracellular matrix (ECM) architecture which it can be considered as the most effective in terms of decellularization. FTIR-ATR and DSC on the other hand, revealed the effects of decellularization on the biochemical composition of the matrices. There was no cytotoxicity and the biological matrices obtained were a source of collagen for recellularization. The matrices of protocols I, II, and III were degraded at day 21 of cell culture, forming a gel. The biocompatibility in vitro was demonstrated; hence these matrices may be deemed as potential scaffold for epithelial tissue regeneration.

Characterization of Embryonic Skin Transcriptome in Anser cygnoides at Three Feather Follicles Developmental Stages

In order to enrich the Anser cygnoides genome and identify the gene expression profiles of primary and secondary feather follicles development, de novo transcriptome assembly of skin tissues was established by analyzing three developmental stages at embryonic day 14, 18, and 28 (E14, E18, E28). Sequencing output generated 436,730,608 clean reads from nine libraries and de novo assembled into 56,301 unigenes. There were 2,298, 9,423 and 12,559 unigenes showing differential expression in three stages respectively. Furthermore, differentially expressed genes (DEGs) were functionally classified according to genes ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and series-cluster analysis. Relevant specific GO terms such as epithelium development, regulation of keratinocyte proliferation, morphogenesis of an epithelium were identified. In all, 15,144 DEGs were clustered into eight profiles with distinct expression patterns and 2,424 DEGs were assigned to 198 KEGG pathways. Skin development related pathways (mitogen-activated protein kinase signaling pathway, extra-cellular matrix -receptor interaction, Wingless-type signaling pathway) and genes (delta like canonical Notch ligand 1, fibroblast growth factor 2, Snail family transcriptional repressor 2, bone morphogenetic protein 6, polo like kinase 1) were identified, and eight DEGs were selected to verify the reliability of transcriptome results by real-time quantitative PCR. The findings of this study will provide the key insights into the complicated molecular mechanism and breeding techniques underlying the developmental characteristics of skin and feather follicles in Anser cygnoides.

Generation of rabbit polyclonal human and murine collagen VII monospecific antibodies: A useful tool for dystrophic epidermolysis bullosa therapy studies

High conservation of extracellular matrix proteins often makes the generation of potent species-specific antibodies challenging. For collagen VII there is a particular preclinical interest in the ability to discriminate between human and murine collagen VII. Deficiency of collagen VII causes dystrophic epidermolysis bullosa (DEB) – a genetic skin blistering disease, which in its most severe forms is highly debilitating. Advances in gene and cell therapy approaches have made curative therapies for genetic diseases a realistic possibility. DEB is one disorder for which substantial progress has been made toward curative therapies and improved management of the disease. However, to increase their efficacy further preclinical studies are needed. The early neonatal lethality of complete collagen VII deficient mice, have led researches to resort to using models maintaining residual collagen VII expression or grafting of DEB model skin on wild-type mice for preclinical therapy studies. These approaches are challenged by collagen VII expression by the murine host. Thus, the ability to selectively visualize human and murine collagen VII would be a substantial advantage. Here, we describe a novel resource toward this end. By immunization with homologous peptides we generated rabbit polyclonal antibodies that recognize either human or murine collagen VII. Testing on additional species, including rat, sheep, dog, and pig, combined sequence alignment and peptide competition binding assays enabled identification of the major antisera recognizing epitopes. The species-specificity was maintained after denaturation and the antibodies allowed us to simultaneously, specifically visualize human and murine collagen VII in situ.

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High sequence conservation of murine and human collagen VII makes development of species-specific antibodies challenging.

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Divergence in the immune epitope of a conserved peptide allowed for generation of species-specific collagen VII antibodies.

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The antibodies allow strong, simultaneous visualization of human and murine collagen VII in immunocompetent hosts.

Basement membrane collagens and disease mechanisms

Basement membranes (BMs) are specialised extracellular matrix (ECM) structures and collagens are a key component required for BM function. While collagen IV is the major BM collagen, collagens VI, VII, XV, XVII and XVIII are also present. Mutations in these collagens cause rare multi-systemic diseases but these collagens have also been associated with major common diseases including stroke. Developing treatments for these conditions will require a collective effort to increase our fundamental understanding of the biology of these collagens and the mechanisms by which mutations therein cause disease. Novel insights into pathomolecular disease mechanisms and cellular responses to these mutations has been exploited to develop proof-of-concept treatment strategies in animal models. Combined, these studies have also highlighted the complexity of the disease mechanisms and the need to obtain a more complete understanding of these mechanisms. The identification of pathomolecular mechanisms of collagen mutations shared between different disorders represent an attractive prospect for treatments that may be effective across phenotypically distinct disorders.

Biallelic KRT5 mutations in autosomal recessive epidermolysis bullosa simplex, including a complete human keratin 5 "knock-out"

Epidermolysis bullosa simplex (EBS) is usually inherited as an autosomal dominant disease due to monoallelic gain-of-function mutations in KRT5 or KRT14. Although autosomal recessive forms of EBS have been associated with mutations in at least 10 genes, recessive EBS due to homozygous biallelic KRT5 mutations has not been reported previously; it has been hypothesized that it would result in prenatal lethality. We sought the genetic causes of EB in a cohort of 512 distinct EB families by performing whole exome sequencing (WES) and using an EB-targeting next-generation sequencing (NGS) panel of 21 genes. The pathogenicity and consequences of the mutations were determined by expression profiling and at tissue and ultrastructural levels. Two pathogenic, homozygous missense variants of KRT5 in two patients with generalized EBS and a homozygous null mutation in a patient who died as a neonate from complications of EB were found. The two missense mutations disrupted keratin 5 expression on immunofluorescence microscopy, and the human "knock-out" of KRT5 showed no RNA and protein expression. Collectively, these findings identify biallelic KRT5 mutations with a phenotypic spectrum varying from mild, localized and generalized to perinatal lethal, expanding the genotypic profile of autosomal recessive EBS.

Newer Treatment Modalities in Epidermolysis Bullosa

The term epidermolysis bullosa (EB) refers to a group of hereditary skin blistering diseases. The group is clinically and genetically heterogeneous, but all EB forms are associated with mechanically induced skin blistering and fragility. The causative gene mutations of most EB types are known. The current international consensus classification contains four main types: EB simplex (EBS), junctional EB (JEB), dystrophic EB (DEB), and Kindler syndrome (KS). The classification is based on the morphological level of blister formation. In EBS, the split is intra-epidermal, in JEB along the basement membrane and in DEB below the basement membrane. In Kindler syndrome, the dermal-epidermal junction is disorganized, and blisters can occur on all three levels. Each major EB type has further subtypes which may differ in terms of their genetic, biological or clinical characteristics. Traditionally, EB treatments have been symptomatic, but increasing understanding of disease etio-pathogenesis is facilitating development of novel evidence-based therapy approaches. First gene- and cell-based therapies are being tested at preclinical level and in clinical trials. New knowledge on secondary disease mechanisms has led to development and clinical testing of urgently needed symptom-relief therapies using small molecules and biologicals.

Cloning and Mutagenesis Strategies for Large Collagens

The size and relatively high GC content of cDNAs are challenges for efficient targeted engineering of large collagens. There are both basic biological and therapeutic interests in the ability to modify collagens, as this would allow for studies precisely describing interactions of collagens with specific interaction partners, addressing consequences of individual disease-causing mutations, and assessing therapeutic applicability of precision medicine approaches. Using collagen VII as an example, we will here describe a strategy for rapid and simple modification of cDNAs encoding large collagens. The method is flexible and can be used for the creation of point mutations, small or large deletions, and insertion of DNA.

Basal pharmacokinetic parameters of topically applied diacerein in pediatric patients with generalized severe epidermolysis bullosa simplex

Abstract

Generalized severe epidermolysis bullosa simplex (EBS-gen sev) is caused by mutations within either the KRT5 or KRT14 gene, phenotypically resulting in blistering and wounding of the skin and mucous membranes after minor mechanical friction. In a clinical phase 2/3 trial, diacerein has recently been shown to significantly reduce blister numbers upon topical application. In this study we addressed basic pharmacokinetic parameters of locally applied diacerein in vitro and in vivo.

Ex vivo experiments using a Franz diffusion cell confirmed the uptake and bio-transformation of diacerein to rhein in a porcine skin model. Rhein, the active metabolite of diacerein, was also detected in both urine and serum samples of two EBS-gen sev patients who topically applied a 1% diacerein ointment over a period of 4 weeks. The accumulated systemic levels of rhein in EBS-gen sev patients were lower than reported levels after oral application.

These preliminary findings point towards the uptake and prolonged persistance of diacerein / rhein within the intended target organ - the skin. Further, they imply an acceptable safety profile at the systemic level.

Trial registration

DRKS. DRKS00005412. Registered 6 November 2013.