Ultrastructure and molecular pathogenesis of epidermolysis bullosa

Long-term safety and efficacy of gene-corrected autologous keratinocyte grafts for recessive dystrophic epidermolysis bullosa

Background

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare, devastating blistering genodermatosis caused by mutations in the COL7A1 gene, which encodes for type VII collagen and is necessary for dermal-epidermal adhesion and integrity. Disease manifestations include severe and debilitating wounds, aggressive squamous cell carcinomas, and premature death; however, there are currently no approved therapies. This Phase 1/2a, open-label study evaluated the long-term efficacy and safety of gene-corrected autologous keratinocyte grafts (EB-101) for chronic RDEB wounds.

Methods

Autologous keratinocytes were harvested from participants with severe RDEB, transduced with a retrovirus containing the full-length COL7A1 gene, and grown into 5 × 7 cm (35 cm²) sheets. Gene-corrected keratinocyte sheets were then transplanted onto chronic RDEB wounds present for ≥ 12 weeks.

Results

Seven adult participants with severe RDEB were grafted with six sheets each (42 total sheets) onto wounds and followed for a mean of 5.9 years (range 4–8 years). Long-term improvements in wound healing and symptoms were observed. At year five, 70% (21/30) of treated sites demonstrated ≥ 50% wound healing compared to baseline by investigator global assessment. No sites with ≥ 50% wound healing were painful or pruritic, compared to 67% (6/9) of sites with < 50% wound healing (p < 0.001) at year five. Grafts were well-tolerated throughout long-term follow-up. No serious adverse events related to treatment were reported over a mean of 5.9 years of follow-up. No persistent systemic autoimmunity against type VII collagen or replication-competent retrovirus infections were identified, and no participants developed squamous cell carcinomas related to treatment during long-term follow-up.

Conclusions

Treatment with EB-101 appears safe and efficacious, and produces long-term improvements in wound healing, pain, and itch for RDEB patients. Results from the Phase 3 randomized controlled trial are forthcoming.

Trial registration

ClinicalTrials.gov, NCT01263379. Registered December 15, 2010. https://clinicaltrials.gov/ct2/show/NCT01263379

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02546-9.

Management of a Femur Shaft Fracture With Nancy Nail in the Setting of Dystrophic Epidermolysis Bullosa: A Case Report

Management of bone fractures must achieve both reduction and stability. However, dermatological conditions such as dystrophic epidermolysis bullosa can lead to catastrophic events when operating on the patient’s bone fracture, possibly leading to wound infections and fracture nonunion.

Here, we report the case of a 20-year-old female with dystrophic epidermolysis bullosa who had suffered from a femur fracture after a fall from the bed. The fracture management was challenging due to the severe condition; however, the use of the Nancy nail was efficient.

Due to the rarity of the disease, modifications due to the challenges faced during the patient care approach were accomplished to prevent any harm to the patient. Even though the management was challenging, the outcome was good.

Case Report: Uncommon Association of ITGB4 and KRT10 Gene Mutation in a Case of Epidermolysis Bullosa With Pyloric Atresia and Aplasia Cutis Congenita

Background: Epidermolysis bullosa is a rare form of genodermatosis produced by different gene mutations. The junctional form of the disease (JEB-PA) can associate pyloric atresia, renal abnormalities, and aplasia cutis congenita.

Case Description: A case of a male preterm newborn with suspicion of digestive tube malformation at fetal ultrasound and who was born by cesarian section. At birth, he presented extensive cutaneous aplasia on the lower limbs and bilaterally under ears; outer ear agenesis; nasal septum hypoplasia; micrognathia; multiple blisters on the face, trunk, and limbs; lower limb deformities and absence of toe nails. Pathological examination following a surgical procedure with unfavorable outcome showed pyloric atresia, junctional form of epidermolysis bullosa and aplasia cutis congenita. Homozygous variants in two genes were identified: c.3111+1G>A in ITGB4 (class 5) and c.1498G>T in KRT10 (class 3).

Conclusion: The particularity of our case is the novel finding of a coincidental occurrence in the context of consaguinity of two mutations in the ITGB4 and KRT10 genes, and clinical characteristics of epidermolysis bullosa.

Advances in gene therapy and their application to skin diseases: A review

With recent advances in genetic engineering technology, gene therapy is now being considered as a treatment not only for congenital diseases but also acquired diseases, such as cancer. Gene therapeutic agents for hereditary immune disorders, haemophilia, retinal diseases, neurodegenerative diseases, and lymphoma have been approved in the United States and Europe. In the field of dermatology, clinical trials of gene therapy have been conducted, because the skin is an easily accessible organ that represents an attractive tissue for gene therapy. In recent years, gene therapy has been attempted for a variety of skin diseases, such as genodermatoses (including epidermolysis bullosa and Netherton syndrome), cutaneous lymphoma, and malignant melanoma. As a result, it is difficult to grasp the current status of gene therapy in dermatology. This review focuses on each of the gene-transfer techniques currently in use and describes the current status of gene therapy for skin diseases using each technology.

Efficacy of allogeneic cord blood platelet gel on wounds of dystrophic epidermolysis bullosa patients after pseudosyndactyly surgery

Epidermolysis bullosa (EB) is a rare genetic disorder characterized by the formation of blisters and wounds in skin and mucous membranes; it is classified into four types and has various methods of treatment. Management of previous wounds and prevention of formation of new lesions are the most important strategies in the course of therapy to improve patient's quality of life; lack of wound management can lead to further complications such as infection. The current study investigated the therapeutic effects of allogeneic platelet gel (prepared from umbilical cord blood) in a group of children diagnosed with dystrophic epidermolysis bullosa (DEB) eligible for surgical correction of pseudosyndactyly in the hand. The post-surgical clinical outcome in this group was compared with the clinical outcomes of DEB patients receiving the standard treatment (paraffin gauze wound dressing and topical antibiotics) after corrective surgery. The current study results showed an increase in the rate of recovery and promotion of tissue granulation, complete wound healing, and a decrease in pain level and treatment period. The application of cord blood platelet gel topical dressing was not a conventional method of treatment in patients with DEB wounds and blisters. However, the current study results demonstrated that this gel dressing could effectively accelerate epithelialization and healing of the wounds and decrease patients' pain and post-surgical recovery period, which altogether leads to improvements in patients' overall quality of life.

Surgical management of hand deformities in patients with recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a congenital disease caused by a mutation in the COL7A1 gene and frequently results in hand contractures and pseudosyndactyly. Although multiple treatments exist that can improve the hand malformations, there are currently still no radical cures for this disease because of its high recurrence rate. The present study reports our experiences on how to improve hand deformities in 11 RDEB patients with surgical management and postoperative skin dressings. Hand function was substantially improved after complete release of pseudosyndactyly and achievement of favorable digital web spaces. Patients were followed up for two years, and nine of which showed slight decrease in hand function characterized by re-narrowed web spaces, digit adhesion and flexed metacarpophalangeal (MP) and interphalangeal (IP) joints, while the last two patients underwent hand reoperation one year after their initial surgery because of recurrence. In conclusion, our results show that surgical correction followed by skin dressing changes is an effective approach to improving mitten-hand malformations in RDEB patients.

Genome Editing in Induced Pluripotent Stem Cells using CRISPR/Cas9

The development of the reprogramming technology led to generation of induced Pluripotent Stem Cells (iPSC) from a variety of somatic cells. Ever since, fast growing knowledge of different efficient protocols enabled the differentiation of these iPSCs into different cells types utilized for disease modeling. Indeed, iPSC-derived cells have been increasingly used for investigating molecular and cellular pathophysiological mechanisms underlying inherited diseases. However, a major barrier in the field of iPSC-based disease modeling relies on discriminating between the effects of the causative mutation and the genetic background of these cells. In the past decade, researchers have made great improvement in genome editing techniques, with one of the latest being CRISPR/Cas9. Using a single non-sequence specific protein combined with a small guiding RNA molecule, this state-of-the-art approach enables modifications of genes with high efficiency and accuracy. By so doing, this technique enables the generation of isogenic controls or isogenic mutated cell lines in order to focus on the pathologies caused by a specific mutation. In this article, we review the latest studies combining iPSC and CRISPR/Cas9 technologies for the investigation of the molecular and cellular mechanisms underlying inherited diseases including immunological, metabolic, hematological, neurodegenerative and cardiac diseases.

Recessive dystrophic epidermolysis bullosa results in painful small fibre neuropathy

Small fibres in the skin are vulnerable to damage in metabolic or toxic conditions such as diabetes mellitus or chemotherapy resulting in small fibre neuropathy and associated neuropathic pain. Whether injury to the most distal portion of sensory small fibres due to a primary dermatological disorder can cause neuropathic pain is still unclear. Recessive dystrophic epidermolysis bullosa (RDEB) is a rare condition in which mutations of proteins of the dermo-epidermal junction lead to cycles of blistering followed by regeneration of the skin. Damage is exclusive to the skin and mucous membranes, with no known direct compromise of the nervous system. It is increasingly recognized that most RDEB patients experience daily pain, the aetiology of which is unclear but may include inflammation (in the wounds), musculoskeletal (due to atrophy and retraction scars limiting movement) or neuropathic pain. In this study we investigated the incidence of neuropathic pain and examined the presence of nerve dysfunction in RDEB patients. Around three quarters of patients presented with pain of neuropathic characteristics, which had a length-dependent distribution. Quantitative sensory testing of the foot revealed striking impairments in thermal detection thresholds combined with an increased mechanical pain sensitivity and wind up ratio (temporal summation of noxious mechanical stimuli). Nerve conduction studies showed normal large fibre sensory and motor nerve conduction; however, skin biopsy showed a significant decrease in intraepidermal nerve fibre density. Autonomic nervous system testing revealed no abnormalities in heart rate and blood pressure variability however the sympathetic skin response of the foot was impaired and sweat gland innervation was reduced. We conclude that chronic cutaneous injury can lead to injury and dysfunction of the most distal part of small sensory fibres in a length-dependent distribution resulting in disabling neuropathic pain. These findings also support the use of neuropathic pain screening tools in these patients and treatment algorithms designed to target neuropathic pain.

[Current approaches to the morphologic diagnosis of different types of congenital epidermolysis bullosa]

Congenital epidermolysis bullosa (CEB) is an extensive group of hereditary skin diseases, the differential diagnosis of which is a challenge due to the rarity of this pathology and the diversity of its clinical manifestations. The determination of the type of CEB makes it possible to estimate its prognosis and to facilitate a prenatal diagnosis.

AIM

to optimize the morphological diagnosis of different types of CEB.

MATERIAL AND METHODS

28 skin biopsies from 14 patients with different types of CEB were investigated. The investigators performed routine histological examination of skin fragments taken from a bullous area and immunofluorescence antigen mapping using the indirect immunofluorescence test (IIFT) with antibodies against structural proteins of the dermal-epidermal junction (laminin α3, β3, and γ2 chains, keratins 5 and 14, types VII and XVII collagen, α6 and β4 integrin subunits, desmoplakin, plectin, kindlin-1, and plakophillin) of the apparently unaffected skin. The intact skin of healthy individuals, which had been obtained during cosmetic operations, was used as controls in IIFT.

RESULTS

Immunofluorescence antigen mapping could determine the type of CEB in all cases and in 86% of cases identify the protein, the impaired production of which was responsible for the development of the disease.

CONCLUSION

Immunofluorescence antigen mapping is an integral part of the comprehensive morphological diagnosis of CEB, acting as an intermediate between the morphological verification of CEB diagnosis and the targeted search for mutations by a molecular genetic method.

Homocysteine metabolism in children and adolescents with epidermolysis bullosa

Background

Epidermolysis bullosa (EB) belongs to a family of rare heterogeneous, genetic disorders characterized by blistering of the skin and mucous membranes in response to minor mechanical trauma. The involvement of the oral mucosa and oesophagus stenosis is suggested to be responsible for severe nutritional deficiencies, but few studies have till now considered this aspect. This observational study aimed to evaluate homocysteine status in children and adolescents with EB by assessing total plasma homocysteine (tHcy) and metabolically related vitamins (B₆, B₁₂, folate) concentrations.

Methods

Twenty EB patients (12 M; age range 0.5−19 years) were evaluated for: plasma tHcy, serum B₁₂ and holotranscobalamin (HoloTC, the active fraction of B₁₂), serum and erythrocyte folate (s-F and Ery-F, respectively), plasma B₆ and serum high sensitive C-reactive-protein (hsCRP) levels. Clinical severity was also evaluated through the Birmingham Epidermolysis Bullosa Severity (BEBS) score. A sex and age well-matched population was also enrolled.

Results

EB patients showed tHcy levels higher (p = 0.04) and B₆ levels lower (p = 0.03) than controls. B₁₂, HoloTC, s-F and ery-F concentrations did not differ between patients and controls. Multiple linear regression analysis showed that tHcy levels were independent of the metabolically related vitamins levels. In addition, serum hsCRP levels were higher in EB patients than in controls (p = 0.003) and correlated negatively with B₆ concentrations (r = -0.6; p = 0.009). BEBS score correlated negatively with HoloTC (p = 0.022) and B₆ (p = 0.005) levels and positively with age (p = 0.031) and hsCRP levels (p < 0.001).

Conclusions

The assessment of tHcy and metabolically related vitamin levels describes an important aspect of EB patients’ nutritional status which can result essential for their long term care. Monitoring B₆ levels in EB patients could be particularly important in order to prevent several complications associated with B₆ deficiency and to avoid a B₆ excess which sustains an inflammatory condition.

Site-specific genome editing for correction of induced pluripotent stem cells derived from dominant dystrophic epidermolysis bullosa

Genome editing with engineered site-specific endonucleases involves nonhomologous end-joining, leading to reading frame disruption. The approach is applicable to dominant negative disorders, which can be treated simply by knocking out the mutant allele, while leaving the normal allele intact. We applied this strategy to dominant dystrophic epidermolysis bullosa (DDEB), which is caused by a dominant negative mutation in the COL7A1 gene encoding type VII collagen (COL7). We performed genome editing with TALENs and CRISPR/Cas9 targeting the mutation, c.8068_8084delinsGA. We then cotransfected Cas9 and guide RNA expression vectors expressed with GFP and DsRed, respectively, into induced pluripotent stem cells (iPSCs) generated from DDEB fibroblasts. After sorting, 90% of the iPSCs were edited, and we selected four gene-edited iPSC lines for further study. These iPSCs were differentiated into keratinocytes and fibroblasts secreting COL7. RT-PCR and Western blot analyses revealed gene-edited COL7 with frameshift mutations degraded at the protein level. In addition, we confirmed that the gene-edited truncated COL7 could neither associate with normal COL7 nor undergo triple helix formation. Our data establish the feasibility of mutation site-specific genome editing in dominant negative disorders.

Extracellular cleavage of collagen XVII is essential for correct cutaneous basement membrane formation

In skin, basal keratinocytes in the epidermis are tightly attached to the underlying dermis by the basement membrane (BM). The correct expression of hemidesmosomal and extracellular matrix (ECM) proteins is essential for BM formation, and the null-expression of one molecule may induce blistering diseases associated with immature BM formation in humans. However, little is known about the significance of post-translational processing of hemidesmosomal or ECM proteins in BM formation. Here we show that the C-terminal cleavage of hemidesmosomal transmembrane collagen XVII (COL17) is essential for correct BM formation. The homozygous p.R1303Q mutation in COL17 induces BM duplication and blistering in humans. Although laminin 332, a major ECM protein, interacts with COL17 around p.R1303, the mutation leaves the binding of both molecules unchanged. Instead, the mutation hampers the physiological C-terminal cleavage of COL17 in the ECM. Consequently, non-cleaved COL17 ectodomain remnants induce the aberrant deposition of laminin 332 in the ECM, which is thought to be the major pathogenesis of the BM duplication that results from this mutation. As an example of impaired cleavage of COL17, this study shows that regulated processing of hemidesmosomal proteins is essential for correct BM organization in skin.

Molecular architecture and function of the hemidesmosome

Hemidesmosomes are multiprotein complexes that facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane. The mechanical stability of hemidesmosomes relies on multiple interactions of a few protein components that form a membrane-embedded tightly-ordered complex. The core of this complex is provided by integrin α6β4 and P1a, an isoform of the cytoskeletal linker protein plectin that is specifically associated with hemidesmosomes. Integrin α6β4 binds to the extracellular matrix protein laminin-332, whereas P1a forms a bridge to the cytoplasmic keratin intermediate filament network. Other important components are BPAG1e, the epithelial isoform of bullous pemphigoid antigen 1, BPAG2, a collagen-type transmembrane protein and CD151. Inherited or acquired diseases in which essential components of the hemidesmosome are missing or structurally altered result in tissue fragility and blistering. Modulation of hemidesmosome function is of crucial importance for a variety of biological processes, such as terminal differentiation of basal keratinocytes and keratinocyte migration during wound healing and carcinoma invasion. Here, we review the molecular characteristics of the proteins that make up the hemidesmosome core structure and summarize the current knowledge about how their assembly and turnover are regulated by transcriptional and post-translational mechanisms.

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.

Molecular architecture and function of the hemidesmosome

Hemidesmosomes are multiprotein complexes that facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane. The mechanical stability of hemidesmosomes relies on multiple interactions of a few protein components that form a membrane-embedded tightly-ordered complex. The core of this complex is provided by integrin α6β4 and P1a, an isoform of the cytoskeletal linker protein plectin that is specifically associated with hemidesmosomes. Integrin α6β4 binds to the extracellular matrix protein laminin-332, whereas P1a forms a bridge to the cytoplasmic keratin intermediate filament network. Other important components are BPAG1e, the epithelial isoform of bullous pemphigoid antigen 1, BPAG2, a collagen-type transmembrane protein and CD151. Inherited or acquired diseases in which essential components of the hemidesmosome are missing or structurally altered result in tissue fragility and blistering. Modulation of hemidesmosome function is of crucial importance for a variety of biological processes, such as terminal differentiation of basal keratinocytes and keratinocyte migration during wound healing and carcinoma invasion. Here, we review the molecular characteristics of the proteins that make up the hemidesmosome core structure and summarize the current knowledge about how their assembly and turnover are regulated by transcriptional and post-translational mechanisms.

Herlitz junctional epidermolysis bullosa with a novel mutation in LAMB3

Herlitz junctional epidermolysis bullosa (H-JEB) is a rare, heritable mechanobullous disease that affects infants at birth and causes early death. This disease is primarily caused by compound heterozygous or homozygous mutations in one of three genes affecting the function of one of the three chains of the laminin-332 (formerly laminin-5) protein. Here we report a case of H-JEB with a novel heterozygous mutation in LAMB3,c.1597G>A (p.Ala533Thr). These findings attest to the molecular heterogeneity of JEB and emphasize the importance of genetic analysis to help make an accurate diagnosis, predict clinical prognosis, and identify phenotypic-genotypic relationships that may aid in prenatal diagnosis and genetic counseling for the future.

Antibodies to pathogenic epitopes on type XVII collagen cause skin fragility in a complement-dependent and -independent manner

In bullous pemphigoid (BP), the most prevalent autoimmune blistering disease, type XVII collagen (COL17) is targeted by circulating autoantibodies. BP is thought to be an autoantibody-mediated complement-fixing blistering disease, and a juxtamembranous noncollagenous 16A (NC16A) domain spanning Glu(490) to Arg(566) was proved to be the main pathogenic region on COL17, although precise pathogenic epitopes within NC16A have not been elucidated. In this study, we showed that injection of rabbit IgG Abs targeting Asp(522) to Gln(545) induced skin fragility associated with in vivo deposition of IgG and complement in neonatal COL17-humanized mice. Notably, immunoadsorption of rabbit anti-NC16A IgG Ab with this epitope (Asp(522) to Gln(545)) or the anti-NC16A IgG administered together with the peptides of this epitope as a decoy ameliorated skin fragility in the injected neonatal COL17-humanized mice compared with the anti-NC16A IgG alone even though all of the mice showed both IgG and complement deposition. These results led us to investigate an additional, complement-independent mechanism of skin fragility in the mice injected with anti-COL17 Abs. The rabbit anti-NC16A IgG depleted the expression of COL17 in cultured normal human keratinocytes, whereas immunoadsorption of the same IgG with this epitope significantly suppressed the depletion effect. Moreover, passive transfer of F(ab')(2) fragments of the human BP or rabbit IgG Abs against COL17 demonstrated skin fragility in neonatal COL17-humanized mice. In summary, this study reveals the importance of Abs directed against distinct epitopes on COL17, which induce skin fragility in complement-dependent as well as complement-independent ways.