Genetic Disorders of the Extracellular Matrix: From Cell and Gene Therapy to Future Applications in Regenerative Medicine.

Metazoans have evolved to produce various types of extracellular matrix (ECM) that provide structural support, cell adhesion, cell-cell communication, and regulated exposure to external cues. Epithelial cells produce and adhere to a specialized sheet-like ECM, the basement membrane, that is critical for cellular homeostasis and tissue integrity. Mesenchymal cells, such as chondrocytes in cartilaginous tissues and keratocytes in the corneal stroma, produce a pericellular matrix that presents optimal levels of growth factors, cytokines, chemokines, and nutrients to the cell and regulates mechanosensory signals through specific cytoskeletal and cell surface receptor interactions. Here, we discuss laminins, collagen types IV and VII, and perlecan, which are major components of these two types of ECM. We examinegenetic defects in these components that cause basement membrane pathologies such as epidermolysis bullosa, Alport syndrome, rare pericellular matrix-related chondrodysplasias, and corneal keratoconus and discuss recent advances in cell and gene therapies being developed for some of these disorders.

Allele-specific CRISPR-Cas9 editing of dominant epidermolysis bullosa simplex in human epidermal stem cells.

Epidermolysis bullosa simplex (EBS) is a rare skin disease inherited mostly in an autosomal dominant manner. Patients display a skin fragility that leads to blisters and erosions caused by minor mechanical trauma. EBS phenotypic and genotypic variants are caused by genetic defects in intracellular proteins whose function is to provide the attachment of basal keratinocytes to the basement membrane zone and most EBS cases display mutations in keratin 5 (KRT5) and keratin 14 (KRT14) genes. Besides palliative treatments, there is still no long-lasting effective cure to correct the mutant gene and abolish the dominant negative effect of the pathogenic protein over its wild-type counterpart. Here, we propose a molecular strategy for EBS01 patient's keratinocytes carrying a monoallelic c.475/495del21 mutation in KRT14 exon 1. Through the CRISPR-Cas9 system, we perform a specific cleavage only on the mutant allele and restore a normal cellular phenotype and a correct intermediate filament network, without affecting the epidermal stem cell, referred to as holoclones, which play a crucial role in epidermal regeneration.

On- and off-target effects of paired CRISPR-Cas nickase in primary human cells.

Undesired on- and off-target effects of CRISPR-Cas nucleases remain a challenge in genome editing. While the use of Cas9 nickases has been shown to minimize off-target mutagenesis, their use in therapeutic genome editing has been hampered by a lack of efficacy. To overcome this limitation, we and others have developed double-nickase-based strategies to generate staggered DNA double-strand breaks to mediate gene disruption or gene correction with high efficiency. However, the impact of paired single-strand nicks on genome integrity has remained largely unexplored. Here, we developed a novel CAST-seq pipeline, dual CAST, to characterize chromosomal aberrations induced by paired CRISPR-Cas9 nickases at three different loci in primary keratinocytes derived from patients with epidermolysis bullosa. While targeting COL7A1, COL17A1, or LAMA3 with Cas9 nucleases caused previously undescribed chromosomal rearrangements, no chromosomal translocations were detected following paired-nickase editing. While the double-nicking strategy induced large deletions/inversions within a 10 kb region surrounding the target sites at all three loci, similar to the nucleases, the chromosomal on-target aberrations were qualitatively different and included a high proportion of insertions. Taken together, our data indicate that double-nickase approaches combine efficient editing with greatly reduced off-target effects but still leave substantial chromosomal aberrations at on-target sites.

Lentiviral expression of wild-type LAMA3A restores cell adhesion in airway basal cells from children with epidermolysis bullosa.

The hallmark of epidermolysis bullosa (EB) is fragile attachment of epithelia due to genetic variants in cell adhesion genes. We describe 16 EB patients treated in the ear, nose, and throat department of a tertiary pediatric hospital linked to the United Kingdom's national EB unit between 1992 and 2023. Patients suffered a high degree of morbidity and mortality from laryngotracheal stenosis. Variants in laminin subunit alpha-3 (LAMA3) were found in 10/15 patients where genotype was available. LAMA3 encodes a subunit of the laminin-332 heterotrimeric extracellular matrix protein complex and is expressed by airway epithelial basal stem cells. We investigated the benefit of restoring wild-type LAMA3 expression in primary EB patient-derived basal cell cultures. EB basal cells demonstrated weak adhesion to cell culture substrates, but could otherwise be expanded similarly to non-EB basal cells. In vitro lentiviral overexpression of LAMA3A in EB basal cells enabled them to differentiate in air-liquid interface cultures, producing cilia with normal ciliary beat frequency. Moreover, transduction restored cell adhesion to levels comparable to a non-EB donor culture. These data provide proof of concept for a combined cell and gene therapy approach to treat airway disease in LAMA3-affected EB.

Heterozygous COL17A1 variants are a frequent cause of amelogenesis imperfecta.

BACKGROUND: Collagen XVII is most typically associated with human disease when biallelic COL17A1 variants (>230) cause junctional epidermolysis bullosa (JEB), a rare, genetically heterogeneous, mucocutaneous blistering disease with amelogenesis imperfecta (AI), a developmental enamel defect. Despite recognition that heterozygous carriers in JEB families can have AI, and that heterozygous COL17A1 variants also cause dominant corneal epithelial recurrent erosion dystrophy (ERED), the importance of heterozygous COL17A1 variants causing dominant non-syndromic AI is not widely recognised. METHODS: Probands from an AI cohort were screened by single molecule molecular inversion probes or targeted hybridisation capture (both a custom panel and whole exome sequencing) for COL17A1 variants. Patient phenotypes were assessed by clinical examination and analyses of affected teeth. RESULTS: Nineteen unrelated probands with isolated AI (no co-segregating features) had 17 heterozygous, potentially pathogenic COL17A1 variants, including missense, premature termination codons, frameshift and splice site variants in both the endo-domains and the ecto-domains of the protein. The AI phenotype was consistent with enamel of near normal thickness and variable focal hypoplasia with surface irregularities including pitting. CONCLUSION: These results indicate that COL17A1 variants are a frequent cause of dominantly inherited non-syndromic AI. Comparison of variants implicated in AI and JEB identifies similarities in type and distribution, with five identified in both conditions, one of which may also cause ERED. Increased availability of genetic testing means that more individuals will receive reports of heterozygous COL17A1 variants. We propose that patients with isolated AI or ERED, due to COL17A1 variants, should be considered as potential carriers for JEB and counselled accordingly, reflecting the importance of multidisciplinary care.

Cancer-associated fibroblast activation predicts progression, metastasis, and prognosis of cutaneous squamous cell carcinoma.

Cutaneous squamous cell carcinoma (cSCC) is the most common metastatic skin cancer and the metastatic disease is associated with poor prognosis. Cancer-associated fibroblasts (CAFs) promote progression of cancer, but their role in cSCC is largely unknown. We examined the potential of CAF markers in the assessment of metastasis risk and prognosis of primary cSCC. We utilized multiplexed fluorescence immunohistochemistry for profiling CAF landscape in metastatic and non-metastatic primary human cSCCs, in metastases, and in premalignant epidermal lesions. Quantitative high-resolution image analysis was performed with two separate panels of antibodies for CAF markers and results were correlated with clinical and histopathological parameters including disease-specific mortality. Increased stromal expression of fibroblast activation protein (FAP), α-smooth muscle actin, and secreted protein acidic and rich in cysteine (SPARC) were associated with progression to invasive cSCC. Elevation of FAP and platelet-derived growth factor receptor-ß (PDGFRß) expression was associated with metastasis risk of primary cSCCs. High expression of PDGFRß and periostin correlated with poor prognosis. Multimarker combination defined CAF subset, PDGFRα-/PDGFRß+/FAP+, was associated with invasion and metastasis, and independently predicted poor disease-specific survival. These results identify high PDGFRß expression alone and multimarker combination PDGFRα-/PDGFRß+/FAP+ by CAFs as potential biomarkers for risk of metastasis and poor prognosis.

Patients suffering from dystrophic epidermolysis bullosa are prone to developing autoantibodies against skin proteins: A longitudinal confirmational study.

Epidermolysis bullosa (EB) is a heritable skin blistering disease caused by variants in genes coding for proteins that secure cell-cell adhesion and attachment of the epidermis to the dermis. Interestingly, several proteins involved in inherited EB are also associated with autoimmune blistering diseases (AIBD). In this study, we present a long-term follow-up of 15 patients suffering from recessive dystrophic or junctional EB. From these patients, 62 sera were analysed for the presence of autoantibodies associated with AIBD. We show that patients suffering from recessive dystrophic EB (RDEB) are more susceptible to developing autoantibodies against skin proteins than patients suffering from junctional EB (70% vs. 20%, respectively). Interestingly, no correlation with age was observed. Most patients showed reactivity to Type XVII collagen/linear IgA bullous dermatosis autoantigen (n = 5; 33%), followed by BP230 (n = 4; 27%), Type VII collagen (n = 4; 27%) and laminin-332 (n = 1; 7%). The pathogenicity of these autoantibodies remains a subject for future experiments.

Elevated expression of interleukin-6 (IL-6) and serum amyloid A (SAA) in the skin and the serum of recessive dystrophic epidermolysis bullosa: Skin as a possible source of IL-6 through Toll-like receptor ligands and SAA.

The effect of persistent skin inflammation on extracutaneous organs and blood is not well studied. Patients with recessive dystrophic epidermolysis bullosa (RDEB), a severe form of the inherited blistering skin disorder, have widespread and persistent skin ulcers, and they develop various complications including anaemia, hyperglobulinaemia, hypoalbuminaemia and secondary amyloidosis. These complications are associated with the bioactivities of IL-6, and the development of secondary amyloidosis requires the persistent elevation of serum amyloid A (SAA) level. We found that patients with RDEB had significantly higher serum levels of IL-6 and SAA compared to healthy volunteers and patients with psoriasis or atopic dermatitis. Both IL-6 and SAA were highly expressed in epidermal keratinocytes and dermal fibroblasts of the skin ulcer lesions. Keratinocytes and fibroblasts surrounding the ulcer lesions are continuously exposed to Toll-like receptor (TLR) ligands, pathogen-associated and damage-associated molecular pattern molecules. In vitro, TLR ligands induced IL-6 expression via NF-κB in normal human epidermal keratinocytes (NHEKs) and dermal fibroblasts (NHDFs). SAA further induced the expression of IL-6 via TLR1/2 and NF-κB in NHEKs and NHDFs. The limitation of this study is that NHEKs and NHDFs were not derived from RDEB patients. These observations suggest that TLR-mediated persistent skin inflammation might increase the risk of IL-6-related systemic complications, including RDEB.

Stop codon readthrough as a treatment option for epidermolysis bullosa-Where we are and where we are going.

In the context of rare genetic diseases caused by nonsense mutations, the concept of induced stop codon readthrough (SCR) represents an attractive avenue in the ongoing search for improved treatment options. Epidermolysis bullosa (EB)-exemplary for this group of diseases-describes a diverse group of rare, blistering genodermatoses. Characterized by extreme skin fragility upon minor mechanical trauma, the most severe forms often result from nonsense mutations that lead to premature translation termination and loss of function of essential proteins at the dermo-epidermal junction. Since no curative interventions are currently available, medical care is mainly limited to alleviating symptoms and preventing complications. Complementary to attempts of gene, cell and protein therapy in EB, SCR represents a promising medical alternative. While gentamicin has already been examined in several clinical trials involving EB, other potent SCR inducers, such as ataluren, may also show promise in treating the hitherto non-curative disease. In addition to the extensively studied aminoglycosides and their derivatives, several other substance classes-non-aminoglycoside antibiotics and non-aminoglycoside compounds-are currently under investigation. The extensive data gathered in numerous in vitro experiments and the perspectives they reveal in the clinical setting will be discussed in this review.

Self-improving dystrophic epidermolysis bullosa with a novel heterozygous missense variant in the COL7A1 gene in a Taiwanese family.

Self-improving dystrophic epidermolysis bullosa (DEB) is a genodermatosis that is inherited autosomal dominantly or recessively, and its clinical symptoms may improve or subside spontaneously. Herein, we report a case of self-improving DEB with COL7A1 p.Gly2025Asp variant. The diagnosis was made through histopathological, electron microscopic examination, and genetic testing. The same variant is also noted on his father, who presents with dystrophic toenails without any blisters. This study highlights that idiopathic nail dystrophy could be linked to congenital or hereditary disease. Furthermore, we conducted a review of the literature on the characteristics of reported cases of self-improving DEB with a personal or family history of nail dystrophy. The results supported our findings that nail dystrophy may be the sole manifestation in some family members. We suggest that individuals suffering from idiopathic nail dystrophy may seek genetic counselling when planning pregnancy to early evaluate the potential risk of hereditary diseases.

Functional genotype-phenotype associations in recessive dystrophic epidermolysis bullosa.

BACKGROUND: Genotype-phenotype associations in recessive dystrophic epidermolysis bullosa (RDEB) have been difficult to elucidate. OBJECTIVE: To investigate RDEB genotype-phenotype associations and explore a functional approach to genotype classification. METHODS: Clinical examination and genetic testing of RDEB subjects, including assessment of clinical disease by RDEB subtype and extent of blistering. Genotypes were evaluated according to each variant's effect on type VII collagen function per updated literature and subsequently categorized by degree of impact on VII collagen function as low-impact (splice/missense, missense/missense), medium-impact (premature termination codon [PTC]/missense, splice/splice), and high-impact (PTC/PTC, PTC/splice). Genotype-phenotype associations were investigated using Kruskal-Wallis and Fisher's exact tests, and age-adjusted regressions. RESULTS: Eighty-three participants were included. High-impact variants were associated with worse RDEB subtype and clinical disease, including increased prevalence of generalized blistering (55.6% for low-impact vs 72.7% medium-impact vs 90.4% high-impact variants, P = .002). In age-adjusted regressions, participants with high-impact variants had 40.8-fold greater odds of squamous cell carcinoma compared to low-impact variants (P = .02), and 5.7-fold greater odds of death compared to medium-impact variants (P = .05). LIMITATIONS: Cross-sectional design. CONCLUSION: Functional genotype categories may stratify RDEB severity; high-impact variants correlated with worse clinical outcomes. Further validation in larger cohorts is needed.

Inpatient management of epidermolysis bullosa: Consensus-based hands-on instructions for neonates and postneonates.

BACKGROUND: Epidermolysis bullosa (EB), characterized by skin fragility and blistering, often requires hospitalization. Training for inpatient management of EB is limited, with no unified recommendations available in North America. OBJECTIVE: To develop consensus-derived best practices for hands-on inpatient management of EB in both the neonatal and postneonatal period. METHODS: A modified Delphi method (expert-based input via 2 surveys and a final review) was implemented. Available guidelines from EB Clinical Research Consortium centers were analyzed to determine areas of focus and formulate statements to be voted on by EB Clinical Research Consortium members, experienced EB nurses, and select family members. Study participants evaluated statements using a Likert scale: statements with at least 70% agreement were accepted; statements with 30% or more disagreement were rejected. RESULTS: Ten areas of focus were identified. Delphi participants included 15 dermatologists, 8 nurses, and 6 nonhealth care caregivers. Consensus was established on 103/119 neonatal statements and 105/122 postneonatal statements; no statements were rejected. Most recommendations applied to both age groups. LIMITATIONS: Recommendations may require adjustment based on individual patient's clinical context. CONCLUSION: Using the Delphi method, a consensus-derived resource for hospital-based health care professionals who manage patients with EB has been developed to improve the quality of inpatient care.

Epidermolysis Bullosa in Spain: A Qualitative Analysis of Its Social Impact on Families With Diagnosed Minors.

BACKGROUND: Epidermolysis bullosa (EB) comprises a group of rare types of genodermatoses characterized by extreme mucocutaneous fragility, leading to blistering and/or erosions, even with minimal trauma. Continuous care through wound management is an integral part of daily life for the families and individuals affected. The aim of this study was to assess the social reality and impacts on families of having minor members diagnosed with EB in Spain. METHODS: A qualitative methodology was employed, utilizing four focus groups entailing participation by 24 parents (19 mothers and five fathers) of minors diagnosed with EB in Spain. RESULTS: Negative impacts on the family nucleus were evident in four priority areas of analysis: sociorelational, economic-labour, physical and psychoemotional, with significant differences observed based on the severity of the symptoms. CONCLUSION: Impacts on the family nucleus are noticeable from birth, influencing all other daily life routines and complicating family planning and organization. There is an imperative need to enhance the availability of sociohealth resources and to adopt an interdisciplinary approach to address their biopsychosocial needs. PATIENT OR PUBLIC CONTRIBUTION: The active participation of relatives of minors diagnosed with Epidermolysis Bullosa (EB) is invaluable to sociohealth professionals, legislators and researchers. A team member conducts their professional activities at DEBRA España (national patient association dedicated to enhancing the quality of life for individuals with EB and their families), actively engaging in all study phases.

Epidermolysis Bullosa: Two rare case reports of COL7A1 and EBS-GEN SEV KRT14 variants with review of literature.

EPIDERMOLYSIS: Bullosa is a rare hereditary skin condition that causes blisters. Genes encoding structural proteins at or near the dermal-epidermal junction are mutated recessively or dominantly, and this is the primary cause of EB. Herein, two Chinese boys were diagnosed with the condition, each with a different variant in a gene that serves as a reference for EB genetic counseling. Skincare significantly impacted their prognosis and quality of life. CASE PRESENTATION: Two Chinese boys, with phenotypically normal parents, have been diagnosed with distinct blister symptoms, one with Dominant Dystrophic Epidermolysis Bullosa and the other with a severe form of Epidermolysis Bullosa Simplex. The first patient had a G-to-A variant in the COL7A1 allele, at nucleotide position 6163 which was named "G2055A". The proband is heterozygous for Dystrophic Epidermolysis Bullosa due to a COL7A1 allele with a glycine substitution at the triple helix domain. A similar variant has been discovered in his mother, indicating its potential transmission to future generations. Another patient had severe Epidermolysis Bullosa Simplex with a rare c.377T > A  variant resulting in substitution of amino acid p.Leu126Arg (NM_000526.5 (c.377T > G, p.Leu126Arg) in the Keratin 14 gene. In prior literature, Keratin 14 has been associated with an excellent prognosis. However, our patient with this infrequent variant tragically died from sepsis at 21 days old. There has been a reported occurrence of the variant only once. CONCLUSION: Our study reveals that Epidermolysis Bullosa patients with COL7A1 c.6163G > A and KRT14 c.377T>A variants have different clinical presentations, with dominant forms of Dystrophic EB having milder phenotypes than recessive ones. Thus, the better prognosis in the c.6163G > A patient. Furthermore, c.377T>A patient was more prone to infection than the patient with c.6163G>A gene variant. Genetic testing is crucial for identifying the specific variant responsible and improving treatment options.

Online, home-based dystrophic epidermolysis bullosa registry.

Genetic testing is the gold standard for diagnosing different epidermolysis bullosa (EB) subtypes; however, testing rates are low. We conducted a pilot study to test feasibility of a novel, home-based registry that involved patients with EB submitting self-reported clinical symptoms using secure, online surveys (REDCap) and submitting buccal swabs for exome sequencing of EB-related genes (GeneDx). In total, 50 EB participants were enrolled, with an average age of 17 years and an average distance of 198 miles from EB specialty centers. All buccal swabs (N = 24) provided sufficient DNA for sequencing without causing mucosal trauma and 80% of participants were found to have pathogenic variants in COL7A1, the gene mutated in DEB. Participants with recessive dystrophic EB (RDEB) reported a higher prevalence of esophageal dilations (65.7% vs. 0%, p = .009) and mitten deformities of the feet (57.1% vs. 0%, p = .047) compared to non-RDEB participants.

Bone marrow transplantation and bone marrow-derived mesenchymal stem cell therapy in epidermolysis bullosa: A systematic review.

Epidermolysis bullosa (EB) is a genodermatosis that lacks effective treatments and requires supportive care for its severe, life-threatening manifestations. Bone marrow transplantation (BMT) and its derived cells have been suggested to improve clinical symptoms and quality of life. A comprehensive search was conducted for publications evaluating BMT and bone marrow-derived mesenchymal stem cell (BM-MSC) therapy for EB in PubMed/MEDLINE, Google Scholar, and Cochrane databases from inception until June 2023. A total of 55 participants with severe forms of EB had BMT and/or BM-MSCs, with recessive dystrophic EB as the most common EB type; 53 (96.4%) patients had better wound healing, and 3 (5.5%) patients died of sepsis. The most common adverse events reported were graft failure, sepsis, graft-versus-host disease, and renal insufficiency. Allogeneic BMT is a high-risk procedure with possible benefits and adverse events. BM-MSCs revealed favorable outcomes to improve the safety of EB cell-based therapy by minimizing the risk of serious adverse events, reducing blisters, and accelerating wound healing. Further studies are needed to assess the treatment's long-term effects and clarify the risk/benefit ratio of procedure versus conventional therapy.

Osteoporosis and bone health in pediatric patients with epidermolysis bullosa: A scoping review.

Nutritional compromise, low levels of vitamin D, chronic inflammation, abnormal growth, and physical inactivity affect bone metabolism and compromise long-term bone health in individuals with epidermolysis bullosa (EB). The result is a high risk for osteopenia, osteoporosis, and pathologic fractures, but this important consequence of EB has been the focus of few investigations. Our scoping review found 21 publications that assessed the current understanding and clinical practices for monitoring of osteoporosis and its treatment in EB. Recommendations summarized from 13 of these publications include early nutritional and weight assessments before 2 years of age; bloodwork every 6-12 months starting at birth; Tanner stage assessments every 6 months to detect any pubertal delay; DEXA scans starting at age 6 years with repeated scans every 1-2 years, except in mild cases; and vitamin D supplementation of 80-320 IU daily for children 0-7 years and 720 IU for patients >8 years.

Gross motor development in children with epidermolysis bullosa.

BACKGROUND: Epidermolysis bullosa (EB) is a group of rare, congenital skin disorders, characterized by skin fragility and formation of blisters. The gross motor outcomes of children with EB are not known. OBJECTIVES: The primary objective of the study was to measure the proportion of gross motor delay in children with EB. The secondary objectives were to measure the difference in gross motor outcomes between EB sub-types and change in gross motor outcomes over time. METHODS: Children with EB, aged between one month and five and a half years of age, attending the Sydney Children's Hospital, Epidermolysis Bullosa Clinic, were eligible. Carers completed Ages and Stages Questionnaires, Third Edition, on behalf of their children. Questionnaires were scored, and outcomes were compared to age-expected norms. RESULTS: There were 24 participants to complete a questionnaire. Eleven participants completed additional questionnaires over the 24 month study duration. The proportion of children with EB with gross motor delay was greater than age-expected norms (29.17% vs. 2.5%). The delay occurred in children with recessive dystrophic (80%) and epidermolysis bullosa simplex (33.33%) sub-types, but not dominant dystrophic (0%). No children with Junctional EB or Kindler EB joined this study. CONCLUSIONS: This study demonstrates a difference in gross motor outcomes in children with EB. Children with recessive dystrophic and epidermolysis bullosa simplex should be prioritized for monitoring of, and intervention for, gross motor outcomes through multidisciplinary care. Further research investigating long-term outcomes for children with EB and the effectiveness of interventions would be beneficial.

A neutral comparison of statistical methods for analyzing longitudinally measured ordinal outcomes in rare diseases.

Ordinal data in a repeated measures design of a crossover study for rare diseases usually do not allow for the use of standard parametric methods, and hence, nonparametric methods should be considered instead. However, only limited simulation studies in settings with small sample sizes exist. Therefore, starting from an Epidermolysis Bullosa simplex trial with the above-mentioned design, a rank-based approach using the R package nparLD and different generalized pairwise comparisons (GPC) methods were compared impartially in a simulation study. The results revealed that there was not one single best method for this particular design, because a trade-off exists between achieving high power, accounting for period effects, and for missing data. Specifically, nparLD as well as the unmatched GPC approaches do not address crossover aspects, and the univariate GPC variants partly ignore the longitudinal information. The matched GPC approaches, on the other hand, take the crossover effect into account in the sense of incorporating the within-subject association. Overall, the prioritized unmatched GPC method achieved the highest power in the simulation scenarios, although this may be due to the specified prioritization. The rank-based approach yielded good power even at a sample size of N = 6 $N=6$ , whereas the matched GPC method could not control the type I error.

Splicing Modulation via Antisense Oligonucleotides in Recessive Dystrophic Epidermolysis Bullosa.

Antisense oligonucleotides (ASOs) represent an emerging therapeutic platform for targeting genetic diseases by influencing various aspects of (pre-)mRNA biology, such as splicing, stability, and translation. In this study, we investigated the potential of modulating the splicing pattern in recessive dystrophic epidermolysis bullosa (RDEB) patient cells carrying a frequent genomic variant (c.425A > G) that disrupts splicing in the COL7A1 gene by using short 2'-O-(2-Methoxyethyl) oligoribo-nucleotides (2'-MOE ASOs). COL7A1-encoded type VII collagen (C7) forms the anchoring fibrils within the skin that are essential for the attachment of the epidermis to the underlying dermis. As such, gene variants of COL7A1 leading to functionally impaired or absent C7 manifest in the form of extensive blistering and wounding. The severity of the disease pattern warrants the development of novel therapies for patients. The c.425A > G variant at the COL7A1 exon 3/intron 3 junction lowers the efficiency of splicing at this junction, resulting in non-functional C7 transcripts. However, we found that correct splicing still occurs, albeit at a very low level, highlighting an opportunity for intervention by modulating the splicing reaction. We therefore screened 2'-MOE ASOs that bind along the COL7A1 target region ranging from exon 3 to the intron 3/exon 4 junction for their ability to modulate splicing. We identified ASOs capable of increasing the relative levels of correctly spliced COL7A1 transcripts by RT-PCR, sqRT-PCR, and ddPCR. Furthermore, RDEB-derived skin equivalents treated with one of the most promising ASOs exhibited an increase in full-length C7 expression and its accurate deposition along the basement membrane zone (BMZ).