A Review of Acquired Autoimmune Blistering Diseases in Inherited Epidermolysis Bullosa: Implications for the Future of Gene Therapy

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.

Absence of NC14A Domain of COLXVII/BP180 in Mice Results in IL-17‒Associated Skin Inflammation

The deletion of exon 18 from Col17a1 in transgenic ΔNC14A mice results in the absence of the NC14A domain. NC14A corresponds to the human NC16A domain, the immunodominant epitope in bullous pemphigoid. Before the age of 1 year, 84% of ΔNC14A mice have developed severe itch and skin erosion. Further characterization of mice with mutated CoLXVII (Bp180) revealed acanthosis; subepidermal blistering; and inflammatory cell infiltrates, especially neutrophils, eosinophils, and mast cells in the lesional skin. Direct immunofluorescence analysis detected linear complement C3, IgG, and/or IgA deposition in the dermo‒epidermal junction of symptomatic ΔNC14A mice. Elevated gene expression of IL-17‒associated cytokines was detected in the lesional skin. An increased proportion of dendritic cells, myeloid-derived suppressor cells, and NK cells and a decrease of T cells were found in both the spleen and lymph nodes of symptomatic ΔNC14A mice. The proportions of B cells and regulatory T cells were increased in lymph nodes. An 8-week treatment with an anti‒IL-17A decreased the expression of Il6, Il23a, and Cxcl1 in the nonlesional skin. Our results suggest that the absence of the NC14A domain of CoLXVII in mice causes an autoimmune response against the cutaneous basement membrane and manifests as an IL-17‒associated inflammation in the skin.

Case Report: Diagnostic and Therapeutic Challenges in Severe Mechanobullous Epidermolysis Bullosa Acquisita

Collagen VII is the main constituent of the anchoring fibrils, important adhesive structures that attach the epidermis to the dermal extracellular matrix. Two disorders are caused by dysfunction of collagen VII, both characterized by skin and mucosa fragility, epidermolysis bullosa acquisita (EBA) and dystrophic epidermolysis bullosa (DEB). EBA and DEB share high clinical similarities with significant difference in patients’ age of onset and pathogenesis. Our patients presented with severe and recalcitrant mechanobullous EBA with characteristic DIF, IIF and ELISA diagnostics. But in both women recessive COL7A1 variants were also found, in a monoallelic state. Collagen VII from EBA keratinocytes of our cases was significantly more vulnerable to proteolytic degradation than control keratinocytes, hinting that the heterozygous pathogenic variants were sufficient to destabilize the molecule in vitro. Thus, even if the amount and functionality of mutant and normal type VII collagen polypeptides is sufficient to assure dermal-epidermal adhesion in healthy individuals, the functionally-impaired proteins are probably more prone to development of autoantibodies against them. Our work suggests that testing for COL7A1 genetic variants should be considered in patients with EBA, which either have a patient history hinting towards underlying dystrophic epidermolysis bullosa or pose therapeutic challenges.

Inborn errors of immunity and immunodeficiencies: antibody-mediated pathology and autoimmunity as a consequence of impaired immune reactions

B cell tolerance to self-antigen is an active process that requires the temporal and spatial integration of signals of defined intensity. In common variable immune deficiency disorders (CVID), CTLA-4 deficiency, autoimmune lymphoproliferative syndrome (ALPS), or in collagen VII deficiency, genetic defects in molecules regulating development, activation, maturation and extracellular matrix composition alter the generation of B cells, resulting in immunodeficiency. Paradoxically, at the same time, the defective immune processes favor autoantibody production and immunopathology through impaired establishment of tolerance. The development of systemic autoimmunity in the framework of defective BCR signaling is relatively unusual in genetic mouse models. In sharp contrast, such reduced signaling in humans is clearly linked to pathological autoimmunity. The molecular mechanisms by which tolerance is broken in these settings are only starting to be explored resulting in novel therapeutic interventions. For instance, in CTLA-4 deficiency, homeostasis can be restored by CTLA-4 Ig treatment. Following this example, the identification of the molecular targets causing the reduced signals and their restoration is a visionary way to reestablish tolerance and develop novel therapeutic avenues for immunopathologies. This article is protected by copyright. All rights reserved.

A Familial Form of Epidermolysis Bullosa Simplex Associated with a Pathogenic Variant in KRT5

Epidermolysis bullosa simplex is a disease that belongs to a group of genodermatoses characterised by the formation of superficial bullous lesions caused by minor mechanical trauma to the skin. The skin fragility observed in the EBS is mainly caused by pathogenic variants in the KRT5 and KRT14 genes that compromise the mechanical stability of epithelial cells. By performing DNA sequencing in a female patient with EBS, we found the pathogenic variant c.967G>A (p.Val323Met) in the KRT5 gene. This variant co-segregated with EBS in the family pedigree and was transmitted in an autosomal dominant inheritance manner. This is the first report showing a familial form of EBS due to this pathogenic variant.