Advances in understanding and treating dystrophic epidermolysis bullosa

The Molecular Revolution in Cutaneous Biology: Emerging Landscape in Genomic Dermatology: New Mechanistic Ideas, Gene Editing, and Therapeutic Breakthroughs

Stunning technological advances in genomics have led to spectacular breakthroughs in the understanding of the underlying defects, biological pathways and therapeutic targets of skin diseases leading to new therapeutic interventions. Next-generation sequencing has revolutionized the identification of disease-causing genes and has a profound impact in deciphering gene and protein signatures in rare and frequent skin diseases. Gene addition strategies have shown efficacy in junctional EB and in recessive dystrophic EB (RDEB). TALENs and Cripsr/Cas9 have emerged as highly efficient new tools to edit genomic sequences to creat new models and to correct or disrupt mutated genes to treat human diseases. Therapeutic approaches have not been limited to DNA modification and strategies at the mRNA, protein and cellular levels have also emerged, some of which have already proven clinical efficacy in RDEB. Improved understanding of the pathogenesis of skin disorders has led to the development of specific drugs or repurposing of existing medicines as in basal cell nevus syndrome, alopecia areata, melanoma and EB simplex. These discoveries pave the way for improved targeted personalized medicine for rare and frequent diseases. It is likely that a growing number of orphan skin diseases will benefit from combinatory new therapies in a near future.

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.

Case Report: Whole exome sequencing reveals a novel frameshift deletion mutation p.G2254fs in COL7A1 associated with autosomal recessive dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa simplex (DEB) is a phenotypically diverse inherited skin fragility disorder. It is majorly manifested by appearance of epidermal bullae upon friction caused either by physical or environmental trauma. The phenotypic manifestations also include appearance of milia, scarring all over the body and nail dystrophy. DEB can be inherited in a recessive or dominant form and the recessive form of DEB (RDEB) is more severe. In the present study, we identify a novel p.G2254fs mutation in COL7A1 gene causing a sporadic case of RDEB by whole exome sequencing (WES). Apart from adding a novel frameshift Collagen VII mutation to the repertoire of known mutations reported in the disease, to the best of our knowledge, this is the first report of a genetically characterized case of DEB from India.

Analysis of the functional consequences of targeted exon deletion in COL7A1 reveals prospects for dystrophic epidermolysis bullosa therapy

Genetically evoked deficiency of collagen VII causes dystrophic epidermolysis bullosa (DEB)-a debilitating disease characterized by chronic skin fragility and progressive fibrosis. Removal of exons carrying frame-disrupting mutations can reinstate protein expression in genetic diseases. The therapeutic potential of this approach is critically dependent on gene, protein, and disease intrinsic factors. Naturally occurring exon skipping in COL7A1, translating collagen VII, suggests that skipping of exons containing disease-causing mutations may be feasible for the treatment of DEB. However, despite a primarily in-frame arrangement of exons in the COL7A1 gene, no general conclusion of the aptitude of exon skipping for DEB can be drawn, since regulation of collagen VII functionality is complex involving folding, intra- and intermolecular interactions. To directly address this, we deleted two conceptually important exons located at both ends of COL7A1, exon 13, containing recurrent mutations, and exon 105, predicted to impact folding. The resulting recombinantly expressed proteins showed conserved functionality in biochemical and in vitro assays. Injected into DEB mice, the proteins promoted skin stability. By demonstrating functionality of internally deleted collagen VII variants, our study provides support of targeted exon deletion or skipping as a potential therapy to treat a large number of individuals with DEB.

Collagen VII Half-Life at the Dermal-Epidermal Junction Zone: Implications for Mechanisms and Therapy of Genodermatoses

The tissue half-life of proteins largely determines treatment frequency of non-gene-editing-based therapies targeting the cause of genodermatoses. Surprisingly, such knowledge is missing for a vast number of proteins involved in pathologies. The dermal-epidermal junction zone is believed to be a rather static structure, but to our knowledge no detailed analysis of the stability of proteins within this zone has been performed. Here, we addressed the in vivo half-life of collagen type VII using genetic ablation of its expression and therapeutic introduction of exogenous collagen VII in a preclinical model. A similar in vivo stability of collagen VII was observed in the skin, tongue, and esophagus, with a half-life of about 1 month. Collagen VII expressed by intradermally injected mesenchymal stromal cells also exhibited a similar half-life. Our study provides key information needed for the development of protein replacement or cell-based therapies for dystrophic epidermolysis bullosa caused by genetic deficiency of collagen VII. Moreover, by showing what we define as an intermediate half-life of collagen VII, our study challenges the view of the dermal-epidermal junction zone as a static structure with very slow turnover.

Lysyl Hydroxylase 3 Localizes to Epidermal Basement Membrane and Is Reduced in Patients with Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is caused by mutations in COL7A1 resulting in reduced or absent type VII collagen, aberrant anchoring fibril formation and subsequent dermal-epidermal fragility. Here, we identify a significant decrease in PLOD3 expression and its encoded protein, the collagen modifying enzyme lysyl hydroxylase 3 (LH3), in RDEB. We show abundant LH3 localising to the basement membrane in normal skin which is severely depleted in RDEB patient skin. We demonstrate expression is in-part regulated by endogenous type VII collagen and that, in agreement with previous studies, even small reductions in LH3 expression lead to significantly less secreted LH3 protein. Exogenous type VII collagen did not alter LH3 expression in cultured RDEB keratinocytes and we show that RDEB patients receiving bone marrow transplantation who demonstrate significant increase in type VII collagen do not show increased levels of LH3 at the basement membrane. Our data report a direct link between LH3 and endogenous type VII collagen expression concluding that reduction of LH3 at the basement membrane in patients with RDEB will likely have significant implications for disease progression and therapeutic intervention.

Medical cell technologies for treatment of patients suffering from recessive dystrophic epidermolysis bullosa. Method of intracutaneous administration of fibroblasts

Recessive dystrophic epidermolysis bullosa (RDEB) is a severe inherited disease developing due to genetic abnormalities in the synthesis of Type VII collagen by fibroblasts. A low production rate of Type VII collagen and abnormalities related to the formation of anchoring fibrils weaken the epidermis and derma adhesion strength, which results in the formation of blisters or erosions in case of any mechanical injury. Fibroblasts and keratinocytes belong to the key sources of Type VII collagen in the skin. Application of allogeneic fibroblasts is a promising cell technique for treating RDEB patients. The therapeutic effect of fibroblasts intradermal administration is stipulated by high stability of newly synthesized Type VII collagen and its ability to form anchoring fibrils in the area of the dermoepidermal junction. According to experimental and clinical studies, it is possible to boost the content of Type VII collagen in the dermoepidermal junction area and heal long-term skin defects in RDEB patients by means of intradermal administration of allogeneic fibroblasts.

Dystrophic epidermolysis bullosa: a review

Dystrophic epidermolysis bullosa is a rare inherited blistering disorder caused by mutations in the COL7A1 gene encoding type VII collagen. The deficiency and/or dysfunction of type VII collagen leads to subepidermal blistering immediately below the lamina densa, resulting in mucocutaneous fragility and disease complications such as intractable ulcers, extensive scarring, malnutrition, and malignancy. The disease is usually diagnosed by immunofluorescence mapping and/or transmission electron microscopy and subsequently subclassified into one of 14 subtypes. This review provides practical knowledge on the disease, including new therapeutic strategies.

Innovative therapeutic strategies for recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is among the most serious rare skin diseases. It is also the rare skin disease for which most effort has been expended in developing advanced therapeutic interventions. RDEB is caused by collagen VII deficiency resulting from COL7A1 mutations. Therapeutic approaches seek to replenish collagen VII and thus restore dermal-epidermal adhesion. Therapeutic options under development include protein therapy and different cell-based and gene-based therapies. In addition to treating skin defects, some of these therapies may also target internal mucosa. In the coming years, these novel therapeutic approaches should substantially improve the quality of life of patients with RDEB.