Recessive Dystrophic Epidermolysis Bullosa Skin Research Articles

O21 Raman spectroscopy for detection of squamous cell carcinoma in recessive dystrophic epidermolysis bullosa skin

Abstract Introduction and aims Recessive dystrophic epidermolysis bullosa (RDEB) is a genetic skin disorder caused by biallelic pathogenic variants in COL7A1, which encodes type VII collagen (C7). Lack of C7 leads to blistering, chronic wounds, scarring and early onset of life-shortening squamous cell carcinomas (SCCs). Currently, the suspicion of SCC is mostly determined by clinical observation of visible changes in chronic wounds, and often requires multiple biopsies for histological diagnosis. This project aims to improve clinical care by developing a new noninvasive means of detecting SCC. To achieve this, we used Raman spectroscopy, a nondestructive analytical technique to study the changes occurring in RDEB skin when SCC is present, with the goal of creating a bedside test that can aid clinicians in the early diagnosis of SCC. Methods Raman spectroscopic imaging was performed on 7-µm frozen skin sections from RDEB (n = 3), RDEB SCC (n = 3) and normal skin (n = 3) to identify signalling changes between nonlesional and lesional states. An in-depth molecular composition analysis of the samples was performed using multivariate analysis with the goal of highlighting changes in abundance of specific molecules when SCC is present. Results For both nonmalignant and RDEB SCC skin sites we found specific Raman peaks associated with protein (1004 cm−1, 1650 cm−1) or lipids (1450 cm−1). RDEB SCC indicated a relative increase in DNA and protein. High-quality Raman spectroscopic images could be acquired that showed clear correlation with histological appearances. Current work is under way to determine which specific biological compounds contribute to the Raman spectra observed. Conclusions Raman spectroscopic imaging can provide comprehensive and noninvasive molecular tissue mapping with resolution comparable to histological sections, enabling molecular-based detection of SCC. Future work will focus on characterization of the SCC molecular profile, in addition to determining whether fibre optic Raman spectroscopy can be used to guide the biopsy/resection of RDEB lesions.

Mechanism underlying pruritus in recessive dystrophic epidermolysis bullosa: Role of interleukin-31 from mast cells and macrophages.

Pruritus is a highly burdensome symptom in patients with epidermolysis bullosa, especially recessive dystrophic epidermolysis bullosa (RDEB); however, only a few studies have assessed the molecular pathogenesis of RDEB-associated pruritus. Interleukin (IL)-31 is a key cytokine implicated in pruritus associated with dermatologic diseases such as atopic dermatitis and prurigo nodularis. To investigate the role and cellular source of IL-31 in RDEB-associated pruritus. Serum and skin samples were obtained from 11 RDEB patients and 11 healthy controls. Pruritus visual analogue scale scores were determined. Serum levels of IL-31 and thymic stromal lymphopoietin (TSLP) were examined by enzyme-linked immunosorbent assay (ELISA). The expression of IL-31 and other pruritus mediators in the skin were examined through immunofluorescence staining, and their correlation with pruritus severity was analysed. Serum IL-31 and TSLP were elevated in RDEB patients. IL-31 expression was increased in RDEB skin and positively correlated with pruritus severity. Most of the IL-31-expressing cells were mast cells, and some were CD206(+) M2-like macrophages. The number of substance P(+) cells was also increased in the patients' skin, and most of them were mast cells. The number of substance P(+) mast cells was correlated with the number of IL-31(+) dermal infiltrates. The number of IL-4Rα- and IL-13-expressing cells and expression of TSLP and periostin increased in RDEB skin, but without a correlation to pruritus score. The increased production of skin IL-31 from mast cells and M2-like macrophages may be the mechanism underlying pruritus in RDEB.

P21 Tyrosine and serine STAT3 phosphorylation drives cutaneous squamous cell carcinoma in recessive dystrophic epidermolysis bullosa as demonstrated using a 3D in vitro model

Abstract The early onset of aggressive cutaneous squamous cell carcinoma (cSCC) and its rapid progression in recessive dystrophic epidermolysis bullosa (RDEB) leads to nearly 100% mortality rates in these patients. Elevated levels of phospho-STAT3 on tyrosine residue (STAT3Tyr705) have been intensively demonstrated in RDEB-derived cSCC cells, demonstrating that the constitutive activation and dysregulation of the Janus kinase (JAK)/STAT pathway plays a role in RDEB cSCC pathogenesis. We efficiently applied ruxolitinib (JAK1/2 inhibitor that blocks phosphorylation on STAT3Tyr705) to a RDEB–cSCC xenograph mouse model, reducing the size of small tumours but found that it was insufficient to reduce bigger tumours completely. Recently, phosphorylation at serine-727 (STAT3Ser727) has been shown to be relevant in the evolution of some cancers, but it has not yet been studied in RDEB cSCC. We hypothesized that phosphorylation at serine-727 of the STAT3 pathway might play a role in RDEB cSCC tumour development and progression, and could not be inhibited by ruxolitinib. To validate our hypothesis, we studied two RDEB cSCC human patient samples with different degrees of dedifferentiation (normal RDEB skin, edge of the tumour and centre of the RDEB cSCC). We demonstrated that STAT3Tyr705 was preferentially upregulated in the normal RDEB skin followed by the tumour edge skin, presenting less phosphorylation on the tumour. When we analysed STAT3 phosphorylation on STAT3Ser727, we could see that it presented the opposite phosphorylation pattern, being more phosphorylated in the tumour and less in normal RDEB skin. Furthermore, we validated the STAT3Ser727residue pattern across other cSCC cell lines and found that serine phosphorylation is present in other SCCs, demonstrating its crucial role in tumour development. To further investigate and analyse cancer progression in more detail, an easy and robust RDEB cSCC model is instrumental. Therefore, we generated RDEB cSCC spheroids in vitro, which has four key advantages over the previous models developed: (i) it is easy to generate; (ii) small amounts of cells are required; (iii) it is suitable for drug testing; and (iv) it can be used to recapitulate different stages of tumour development. We have been able to control their size and use them for drug testing, observing a 20% size decrease after 6 days of ruxolitinib treatment. Taken together, this three-dimensional RDEB cSCC in vitro model, along with analysis of human samples, will allow us to better understand RDEB cSCC progression at different stages, allowing us to investigate new treatments for RDEB cSCC.

833 Ex vivo gene therapy of recessive dystrophic epidermolysis bullosa skin cells leads to dermo-epidermal adhesion strength restoration in autologous bilayered self-assembled skin substitutes

833 Ex vivo gene therapy of recessive dystrophic epidermolysis bullosa skin cells leads to dermo-epidermal adhesion strength restoration in autologous bilayered self-assembled skin substitutes

ABCB5+ mesenchymal stromal cells facilitate complete and durable wound closure in recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a hereditary, rare, devastating and life-threatening skin fragility disorder with a high unmet medical need. In a recent international, single-arm clinical trial, treatment of 16patients (aged 6-36years) with three intravenous infusions of 2×106immunomodulatory ABCB5+ dermal mesenchymal stromal cells (MSCs)/kg on days0, 17 and 35 reduced disease activity, itch and pain. A post-hoc analysis was undertaken to assess the potential effects of treatment with ABCB5+ MSCs on the overall skin wound healing in patients suffering from RDEB. Documentary photographs of the affected body regions taken on days0, 17, 35 and at 12weeks were evaluated regarding proportion, temporal course and durability of wound closure as well as development of new wounds. Of 168baseline wounds in 14patients, 109 (64.9%) wounds had closed at week12, of which 63.3% (69wounds) had closed already by day35 or day17. Conversely, 74.2% of the baseline wounds that had closed by day17 or day35 remained closed until week12. First-closure ratio within 12weeks was 75.6%. The median rate of newly developing wounds decreased significantly (P=0.001) by 79.3%. Comparison of the findings with published data from placebo arms and vehicle-treated wounds in controlled clinical trials suggests potential capability of ABCB5+ MSCs to facilitate wound closure, prolongate wound recurrence and decelerate formation of new wounds in RDEB. Beyond suggesting therapeutic efficacy for ABCB5+ MSCs, the analysis might stimulate researchers who develop therapies for RDEB and other skin fragility disorders to not only assess closure of preselected target wounds but pay attention to the patients' dynamic and diverse overall wound presentation as well as to the durability of achieved wound closure and the development of new wounds. Clinicaltrials.gov NCT03529877; EudraCT 2018-001009-98.

COL7A1 Editing via RNA Trans-Splicing in RDEB-Derived Skin Equivalents

Mutations in the COL7A1 gene lead to malfunction, reduction or complete absence of type VII collagen (C7) in the skin's basement membrane zone (BMZ), impairing skin integrity. In epidermolysis bullosa (EB), more than 800 mutations in COL7A1 have been reported, leading to the dystrophic form of EB (DEB), a severe and rare skin blistering disease associated with a high risk of developing an aggressive form of squamous cell carcinoma. Here, we leveraged a previously described 3'-RTMS6m repair molecule to develop a non-viral, non-invasive and efficient RNA therapy to correct mutations within COL7A1 via spliceosome-mediated RNA trans-splicing (SMaRT). RTM-S6m, cloned into a non-viral minicircle-GFP vector, is capable of correcting all mutations occurring between exon 65 and exon 118 of COL7A1 via SMaRT. Transfection of the RTM into recessive dystrophic EB (RDEB) keratinocytes resulted in a trans-splicing efficiency of ~1.5% in keratinocytes and ~0.6% in fibroblasts, as confirmed on mRNA level via next-generation sequencing (NGS). Full-length C7 protein expression was primarily confirmed in vitro via immunofluorescence (IF) staining and Western blot analysis of transfected cells. Additionally, we complexed 3'-RTMS6m with a DDC642 liposomal carrier to deliver the RTM topically onto RDEB skin equivalents and were subsequently able to detect an accumulation of restored C7 within the basement membrane zone (BMZ). In summary, we transiently corrected COL7A1 mutations in vitro in RDEB keratinocytes and skin equivalents derived from RDEB keratinocytes and fibroblasts using a non-viral 3'-RTMS6m repair molecule.

Anchoring Cords: A Distinct Suprastructure in the Developing Skin

AMACO (VWA2 protein) is a basement membrane-associated protein secreted by epithelial cells. It is strongly expressed when invagination or budding occurs during development. AMACO associates with the Fraser complex, which when mutated causes Fraser syndrome, characterized by subepidermal blistering, cryptophthalmos, and syndactyly. The core Fraser complex proteins FRAS1, FREM1, and FREM2 localize at the dermal‒epidermal junction and mediate adhesion to the underlying dermis during embryonic development. Earlier transmission electron microscopy studies of adult mouse skin showed clustered AMACO deposition below the lamina densa. In this study, we report a distinct cord-like suprastructure in the neonate dermis to which AMACO- and Fraser complex‒associated proteins contribute. We propose anchoring cords to designate the suprastructure. Anchoring cords have a diameter of 60 nm when immunolabeled, originate from the basement membrane, and extend several microns into the dermis. In normal skin, they are evident after immunogold electron microscopy and are strikingly appreciated in thicker sections. In recessive dystrophic epidermolysis bullosa skin, they are directly visible where collagen VII anchoring fibrils are ablated. Immunofluorescence and coimmunoprecipitation of skin extracts identify a direct interaction of FREM2 and AMACO.

Restoring type VII collagen in skin

New therapeutic hope is emerging for people with the rare inherited blistering skin disease recessive dystrophic epidermolysis bullosa (RDEB). Gurevich etal.1 have reported early-phase clinical trial data evaluating a topical herpes simplex virus 1 vector to restore missing type VII collagen in RDEB skin and heal wounds.

In vivo topical gene therapy for recessive dystrophic epidermolysis bullosa: a phase 1 and 2 trial

Recessive dystrophic epidermolysis bullosa (RDEB) is a lifelong genodermatosis associated with blistering, wounding, and scarring caused by mutations in COL7A1, the gene encoding the anchoring fibril component, collagen VII (C7). Here, we evaluated beremagene geperpavec (B-VEC), an engineered, non-replicating COL7A1 containing herpes simplex virus type 1 (HSV-1) vector, to treat RDEB skin. B-VEC restored C7 expression in RDEB keratinocytes, fibroblasts, RDEB mice and human RDEB xenografts. Subsequently, a randomized, placebo-controlled, phase 1 and 2 clinical trial (NCT03536143) evaluated matched wounds from nine RDEB patients receiving topical B-VEC or placebo repeatedly over 12 weeks. No grade 2 or above B-VEC-related adverse events or vector shedding or tissue-bound skin immunoreactants were noted. HSV-1 and C7 antibodies sometimes presented at baseline or increased after B-VEC treatment without an apparent impact on safety or efficacy. Primary and secondary objectives of C7 expression, anchoring fibril assembly, wound surface area reduction, duration of wound closure, and time to wound closure following B-VEC treatment were met. A patient-reported pain–severity secondary outcome was not assessed given the small proportion of wounds treated. A global assessment secondary endpoint was not pursued due to redundancy with regard to other endpoints. These studies show that B-VEC is an easily administered, safely tolerated, topical molecular corrective therapy promoting wound healing in patients with RDEB.

Interrogation of RDEB Epidermal Allografts after BMT Reveals Coexpression of Collagen VII and Keratin 15 with Proinflammatory Immune Cells and Fibroblasts

Recessive dystrophic epidermolysis bullosa (RDEB) is a devastating genodermatosis characterized by dysfunctional collagen VII protein resulting in epithelial blistering of the skin, mucosa, and gastrointestinal tract. There is no cure for RDEB, but improvement of clinical phenotype has been achieved with bone marrow transplantation and subsequent epidermal allografting from the bone marrow transplant donor. Epidermal allografting of these patients has decreased wound surface area for up to 3 years after treatment. This study aimed to determine the phenotype of the epidermal allograft cells responsible for durable persistence of wound healing and skin integrity. We found that epidermal allografts provide basal keratinocytes coexpressing collagen VII and basal stem cell marker keratin 15. Characterization of RDEB full-thickness skin biopsies with single-cell RNA sequencing uncovered proinflammatory immune and fibroblast phenotypes potentially driven by the local environment of RDEB skin. This is further highlighted by the presence of a myofibroblast population, which has not been described in healthy control human skin. Finally, we found inflammatory fibroblasts expressing profibrotic gene POSTN, which may have implications in the development of squamous cell carcinoma, a common, lethal complication of RDEB that lacks curative treatment. In conclusion, this study provides insights into and targets for future RDEB studies and treatments.

Development of Minicircle Vectors Encoding COL7A1 Gene with Human Promoters for Non-Viral Gene Therapy for Recessive Dystrophic Epidermolysis Bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare autosomal inherited skin disorder caused by mutations in the COL7A1 gene that encodes type VII collagen (C7). The development of an efficient gene replacement strategy for RDEB is mainly hindered by the lack of vectors able to encapsulate and transfect the large cDNA size of this gene. To address this problem, our group has opted to use polymeric-based non-viral delivery systems and minicircle DNA. With this approach, safety is improved by avoiding the usage of viruses, the absence of bacterial backbone, and the replacement of the control viral cytomegalovirus (CMV) promoter of the gene with human promoters. All the promoters showed impressive C7 expression in RDEB skin cells, with eukaryotic translation elongation factor 1 α (EF1α) promoter producing higher C7 expression levels than CMV following minicircle induction, and COL7A1 tissue-specific promoter (C7P) generating C7 levels similar to normal human epidermal keratinocytes. The improved system developed here has a high potential for use as a non-viral topical treatment to restore C7 in RDEB patients efficiently and safely, and to be adapted to other genetic conditions.

Impaired Wound Healing, Fibrosis, and Cancer: The Paradigm of Recessive Dystrophic Epidermolysis Bullosa.

Recessive Dystrophic Epidermolysis Bullosa (RDEB) is a devastating skin blistering disease caused by mutations in the gene encoding type VII collagen (C7), leading to epidermal fragility, trauma-induced blistering, and long term, hard-to-heal wounds. Fibrosis develops rapidly in RDEB skin and contributes to both chronic wounds, which emerge after cycles of repetitive wound and scar formation, and squamous cell carcinoma—the single biggest cause of death in this patient group. The molecular pathways disrupted in a broad spectrum of fibrotic disease are also disrupted in RDEB, and squamous cell carcinomas arising in RDEB are thus far molecularly indistinct from other sub-types of aggressive squamous cell carcinoma (SCC). Collectively these data demonstrate RDEB is a model for understanding the molecular basis of both fibrosis and rapidly developing aggressive cancer. A number of studies have shown that RDEB pathogenesis is driven by a radical change in extracellular matrix (ECM) composition and increased transforming growth factor-beta (TGFβ) signaling that is a direct result of C7 loss-of-function in dermal fibroblasts. However, the exact mechanism of how C7 loss results in extensive fibrosis is unclear, particularly how TGFβ signaling is activated and then sustained through complex networks of cell-cell interaction not limited to the traditional fibrotic protagonist, the dermal fibroblast. Continued study of this rare disease will likely yield paradigms relevant to more common pathologies.

Fludarabine modulates expression of type VII collagen during haematopoietic stem cell transplantation for recessive dystrophic epidermolysis bullosa.

Recessive dystrophic epidermolysis bullosa (RDEB) is a severe, complicated inherited blistering skin disease with few treatment options currently available. Recently, haematopoietic stem cell transplantation (HCT) has been used as an alternative therapy that can improve skin integrity, but it is not known if the preparative HCT regimen also contributes to the therapeutic response. To determine whether chemotherapy drugs used in the HCT preparative regimen influence type VII collagen (C7) expression, which is inherently reduced or absent in RDEB skin, and to explore the pathomechanisms of such responses, if present. Drugs from the HCT preparative regimen (busulfan, cyclophosphamide, ciclosporin A, fludarabine and mycophenolate) with inhibitors (PD98059, U0126, LY294002, SR11302, SIS3 and N-acetyl-l-cysteine) were added to normal human dermal and human RDEB fibroblasts. C7 expression was measured using reversetranscription polymerase chain reaction and immunoblotting. We uncovered a previously unknown consequence of fludarabine whereby dermal fibroblasts exposed to fludarabine upregulate C7. This effect is mediated, in part, through activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinase/protein kinase B and transforming growth factor-β pathways. Activation of these pathways leads to activation of downstream transcription factors, including activator protein 1 (AP-1) and SMAD. Subsequently, both AP-1 and SMAD bind the COL7A1 promoter and increase COL7A1 expression. Fludarabine influences the production of type VII collagen in RDEB fibroblasts.

QR-313, an Antisense Oligonucleotide, Shows Therapeutic Efficacy for Treatment of Dominant and Recessive Dystrophic Epidermolysis Bullosa: A Preclinical Study

Dystrophic epidermolysis bullosa (DEB) is a blistering skin disease caused by mutations in the gene COL7A1 encoding collagen VII. DEB can be inherited as recessive DEB (RDEB) or dominant DEB (DDEB) and is associated with a high wound burden. Perpetual cycles of wounding and healing drive fibrosis in DDEB and RDEB, as well as the formation of a tumor-permissive microenvironment. Prolonging wound-free episodes by improving the quality of wound healing would therefore confer substantial benefit for individuals with DEB. The collagenous domain of collagen VII is encoded by 82 in-frame exons, which makes splice-modulation therapies attractive for DEB. Indeed, antisense oligonucleotide-based exon skipping has shown promise for RDEB. However, the suitability of antisense oligonucleotides for treatment of DDEB remains unexplored. Here, we developed QR-313, a clinically applicable, potent antisense oligonucleotide specifically targeting exon 73. We show the feasibility of topical delivery of QR-313 in a carbomer-composed gel for treatment of wounds to restore collagen VII abundance in human RDEB skin. Our data reveal that QR-313 also shows direct benefit for DDEB caused by exon 73 mutations. Thus, the same topically applied therapeutic could be used to improve the wound healing quality in RDEB and DDEB.

MicroRNA‐145‐5p regulates fibrotic features of recessive dystrophic epidermolysis bullosa skin fibroblasts

Recessive dystrophic epidermolysis bullosa (RDEB) is a skin fragility disorder caused by mutations in the COL7A1 gene encoding type VII collagen, a cutaneous basement membrane component essential for epidermal-dermal adhesion. Hallmarks of the disease are unremitting blistering and chronic wounds with severe inflammation and fibrosis. MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression also implicated in fibrotic processes. However, the role of miRNAs in RDEB fibrosis is almost unexplored. Our study aimed to identify miRNAs deregulated in primary RDEB skin fibroblasts (RDEBFs) and to characterize their function in RDEB fibrosis. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to screen RDEBFs for expression levels of a group of miRNAs deregulated in hypertrophic scars and keloids, pathological conditions with abnormal wound healing and fibrosis. Contractility, proliferation and migration rate were evaluated by different invitro assays in RDEBFs transfected with a miR-145-5p inhibitor. Expression levels of fibrotic markers and miR-145-5p targets were measured using qRT-PCR and western blot. The miR-143/145 cluster was upregulated in RDEBFs compared with fibroblasts from healthy subjects. RDEBFs transfected with a miR-145-5p inhibitor showed attenuated fibrotic traits of contraction, proliferation and migration, accompanied by reduced expression of the contractile proteins α-smooth muscle actin and transgelin. These effects were associated with upregulation of Krüppel-like factor 4 transcriptional repressor and downregulation of Jagged1, a known inducer of fibrosis. Our results highlight the profibrotic role of miR-145-5p and its regulatory networks in RDEB, shedding light on novel disease pathomechanisms and targets for future therapeutic approaches. What's already known about this topic? Recessive dystrophic epidermolysis bullosa (RDEB) is a highly disabling genetic skin disease caused by mutations in the collagen VII gene and characterized by unremitting blistering and defective wound healing, leading to inflammation and fibrosis. MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression in health and disease, and their deregulation has been implicated in fibrotic skin conditions. To date, only miR-29 has been associated with injury-driven fibrosis in RDEB. What does this study add? In patients with RDEB, miR-145-5p is overexpressed in RDEB skin fibroblasts (RDEBFs), where it plays a profibrotic role, as its inhibition reduces RDEBF fibrotic traits (contraction, proliferation and migration). miR-145-5p inhibition in RDEBFs determines the reduction of contractile markers α-smooth muscle actin and transgelin through upregulation of Krüppel-like factor 4, a transcriptional repressor of contractile proteins, and downregulation of Jagged1 (JAG1), an inducer of fibrosis. What is the translational message? Our findings expand the knowledge on miRNA-driven pathomechanisms implicated in RDEB fibrosis. miR-145-5p and its targets (e.g. JAG1) could represent relevant molecules for the development of novel therapeutic strategies to counteract fibrosis progression in patients with RDEB.

Human Mesenchymal Stromal Cells Engineered to Express Collagen VII Can Restore Anchoring Fibrils in Recessive Dystrophic Epidermolysis Bullosa Skin Graft Chimeras

Recessive dystrophic epidermolysis bullosa (RDEB) is a debilitating genodermatosis caused by loss-of-function mutations in COL7A1 encoding type VII collagen (C7), the main component of anchoring fibrils at the dermal-epidermal junction. With no curative treatments presently available, retrovirally transduced autologous epidermal grafts and intradermal lentivirally engineered fibroblast injections are being investigated. Alternative approaches aim to infuse allogeneic mesenchymal stromal cells (MSCs) to provide a more generalized treatment for RDEB. We investigated whether healthy human MSCs could be engineered to overexpress C7 and correct RDEB in a human:murine chimeric model. Initially, engineered MSCs incorporated exvivo into RDEB grafts, their presence confirmed by fluorescence in situ hybridization, revealed recovery of function of the dermal-epidermal junction with no signs of blister formation. Importantly, the detection of anchoring fibrils by transmission electron microscopy corroborated structural recovery. Next, MSCs cotransduced to express C7 and luciferase were delivered intradermally into grafted RDEB skin, resulting in localized MSC persistence with deposition of de novo C7 at the site. Notably, C7 expression was sufficient to restore anchoring fibril density to normal levels. In contrast, intravenously injected engineered MSCs were undetectable within grafts and lacked anchoring fibril reconstitution. Our data suggest that although localized correction may be achievable using engineered MSCs, strategies for systemic administration require further modeling.

Murine type VII collagen distorts outcome in human skin graft mouse model for dystrophic epidermolysis bullosa

Human skin graft mouse models are widely used to investigate and develop therapeutic strategies for the severe generalized form of recessive dystrophic epidermolysis bullosa (RDEB), which is caused by biallelic null mutations in COL7A1 and the complete absence of type VII collagen (C7). Most therapeutic approaches are focused on reintroducing C7. Therefore, C7 and anchoring fibrils are widely used as readouts in therapeutic research with skin graft models. In this study, we investigated the expression pattern of human and murine C7 in a grafting model, in which human skin is reconstituted out of in vitro cultured keratinocytes and fibroblasts. The model revealed that murine C7 was deposited in both human healthy control and RDEB skin grafts. Moreover, we found that murine C7 is able to form anchoring fibrils in human grafts. Therefore, we advocate the use of human‐specific antibodies when assessing the reintroduction of C7 using RDEB skin graft mouse models.

Measurement of skin adhesion in recessive dystrophic epidermolysis bullosa patients

To the Editor: Recessive dystrophic epidermolysis bullosa (RDEB) is a subtype of inherited epidermolysis bullosa. RDEB is a mechanobullous disease due to the lack of functional type VII collagen, which forms anchoring fibrils that are essential to dermal-epidermal adhesion. One method to measure dermal-epidermal adhesion strength is to induce suction blisters.1 For healthy and RDEB participants, suction blister time (SBT) can vary greatly, but previous studies have shown that the necessary time to induce a blister in RDEB skin is less than in normal skin.

Epidermolysis bullosa acquisita and anti-p200 pemphigoid as major subepidermal autoimmune bullous diseases diagnosed by floor binding on indirect immunofluorescence microscopy using human salt-split skin.

Subepidermal autoimmune bullous diseases are a diverse group of diseases with overlapping clinical and immunopathological features. Indirect immunofluorescence microscopy on artificially split skin helps to classify these conditions into those with staining on the epidermal side of the split ("roof-binding") and those with staining on the dermal side ("floor-binding"). Epidermolysis bullosa acquisita is the prototype of "floor-binding" subepidermal autoimmune bullous diseases. However, not all floor-binding sera are associated with epidermolysis bullosa acquisita. The aim of this study was to evaluate the clinical and immunological profile of patients with floor-binding subepidermal autoimmune bullous disease by indirect immunofluorescence microscopy and to identify the target antigens in them. Ten patients who showed a floor-binding pattern were studied with regard to their clinical and immunopathological characteristics. Target antigens were identified by modified indirect immunofluorescence microscopy using recessive dystrophic epidermolysis bullosa skin, enzyme linked immunosorbent assay, and immunoblotting. Diagnosis of epidermolysis bullosa acquisita was confirmed in six patients. Three patients with an inflammatory subepidermal autoimmune bullous disease mimicking bullous pemphigoid reacted with a 200 kDa protein on immunoblotting with dermal extract, as is characteristic of anti-p200 pemphigoid. One serum showed both roof and floor binding, and reacted with the BP180 antigen. We could not perform serration pattern analysis in our patients. In this study, we report three cases of anti-p200 pemphigoid from India. These cases, though indistinguishable clinically from bullous pemphigoid, revealed a floor-binding pattern on indirect immunofluorescence using salt-split skin.

Targeted Exon Skipping Restores Type VII Collagen Expression and Anchoring Fibril Formation in an In Vivo RDEB Model

Dystrophic epidermolysis bullosa is a group of orphan genetic skin diseases dominantly or recessively inherited, caused by mutations in COL7A1 encoding type VII collagen, which forms anchoring fibrils. Individuals with recessive dystrophic epidermolysis bullosa develop severe skin and mucosal blistering after mild trauma. The exon skipping strategy consists of modulating splicing of a pre-mRNA to induce skipping of a mutated exon. We have targeted COL7A1 exons 73 and 80, which carry recurrent mutations and whose excision preserves the open reading frame. We first showed the dispensability of these exons for type VII collagen function invivo. We then showed that transfection of primary recessive dystrophic epidermolysis bullosa keratinocytes and fibroblasts carrying null mutations in exon 73 and/or 80, with 2'-O-methyl antisense oligoribonucleotides, led to efficient exvivo skipping of these exons (50-95%) and resulted in a significant level (upto 36%) of type VII collagen re-expression. Finally, one or two subcutaneous injections of antisense oligoribonucleotides at doses ranging from 400 μg up to 1 mg restored type VII collagen expression and anchoring fibril formation invivo in a xenograft model of recessive dystrophic epidermolysis bullosa skin equivalent. This work provides a proof of principle for the treatment of patients with recessive dystrophic epidermolysis bullosa by exon skipping using subcutaneous administration of antisense oligoribonucleotides.