COL7A1 Mutations Research Articles

Patient-derived podocyte spheroids reveal new insights into the etiopathogenesis of Alport syndrome

Alport syndrome (AS) is a rare disease characterized by defective glomerular basement membranes, caused by mutations in COL4A3, COL4A4, and COL4A5, which synthesize collagen type IV. Patients present with progressive proteinuria, hematuria and podocyte loss. There is currently no cure for Alport syndrome, and this is mainly due to its complex and variable pathogenesis, as well as the lack of models that can faithfully mimic the human phenotype. Here we have developed a novel human culture model of Alport syndrome and used it to study the effects of different mutations on podocyte development and biology. First, we established a differentiation protocol that allowed us to generate podocyte spheroids from patient-derived human induced pluripotent stem cells (hiPSCs). We have then carried out discovery proteomics and demonstrated that a total of 178 proteins were differentially expressed between Alport (AS1 and AS3) and control (LT) podocytes. GO analysis indicated alterations in several metabolic pathways, such as oxidative phosphorylation, RNA maturation, chromatin condensation, and proliferation. Although functional assays showed no changes in lactate production and mitochondrial potential compared to healthy controls, immunofluorescence and electron microscopy analysis showed key morphological changes related to the phenotypical maturation of Alport podocytes. Moreover, the studied mutations led to persistent proliferation, increased reactive oxygen species (ROS) production and the concomitant expression of peroxisome proliferator-activated receptors α and γ (PPARα and PPARγ) in podocytes. These data on patient-derived podocytes provide evidence that collagen mutations, in addition to playing a central role in the defective development of the glomerular filtration barrier, cause significant alterations in podocyte development and metabolism very early in development, even before the formation of the filtering apparatus. In conclusion, our study provides a new methodological platform for the differentiation of podocytes and to study human podocytopathies in a personalized manner, and reveals new insights into the etiopathogenesis and pathobiology of Alport syndrome.

Aortic dissection in a patient with novel frameshift COL5A1 variant of classical Ehlers-Danlos syndrome

Classical Ehlers-Danlos syndrome (cEDS) is one of the 13 subtypes of Ehlers-Danlos syndrome, which has the major clinical criteria of hyperextensibility skin, atrophic scars, and generalised joint hypermobility. The occurrence of aortic dissection has been described in some subtypes of Ehlers-Danlos, but it has a rare association with the cEDS subtype. This case report discusses a 39-year-old female with a past medical history of transposition of great arteries with a Senning repair at the age of 18 months and controlled hypertension with medication, who presents a spontaneous distal aortic dissection. The diagnosis of cEDS was made using the major criteria, and a novel frameshift mutation in COL5A1 was discovered. The reported case emphasises that in patients with cEDS, vascular fragility may be a complication.

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.

Cytosine Deaminase Base Editing to Restore COL7A1 in Dystrophic Epidermolysis Bullosa Human: Murine Skin Model

Recessive dystrophic epidermolysis bullosa is a debilitating blistering skin disorder caused by loss-of-function mutations in COL7A1, which encodes type VII collagen, the main component of anchoring fibrils at the dermal-epidermal junction. Although conventional gene therapy approaches through viral vectors have been tested in preclinical and clinical trials, they are limited by transgene size constraints and only support unregulated gene expression. Genome editing could potentially overcome some of these limitations, and CRISPR/Cas9 has already been applied in research studies to restore COL7A1 expression. The delivery of suitable repair templates for the repair of DNA cleaved by Cas9 is still a major challenge, and alternative base editing strategies may offer corrective solutions for certain mutations. We show highly targeted and efficient cytidine deamination and molecular correction of a defined recessive dystrophic epidermolysis bullosa mutation (c.425A>G), leading to restoration of full-length type VII collagen protein expression in primary human fibroblasts and induced pluripotent stem cells. Type VII collagen basement membrane expression and skin architecture were restored with de novo anchoring fibrils identified by electron microscopy in base-edited human recessive dystrophic epidermolysis bullosa grafts recovered from immunodeficient mice. The results show the potential and promise of emerging base editing technologies in tackling inherited disorders with well-defined single nucleotide mutations.

A mutational signature and significantly mutated driver genes associated with immune checkpoint inhibitor response across multiple cancers

Immune checkpoint inhibitor (ICI) treatments dramatically prolong the survival outcomes of several advanced cancers. However, as multiple studies reported, only a subset of patients could benefit from the ICI treatment. In this study, we aim to uncover novel molecular biomarkers predictive of immunotherapy efficacy across multiple cancers. Pre-treatment somatic mutational profiles and immunotherapy clinical information were obtained from 1097 samples of multiple cancers, including melanoma, non-small cell lung cancer (NSCLC), clear cell renal cell carcinoma (ccRCC), bladder carcinoma (BLCA), and head and neck squamous cell carcinoma (HNSCC). Mutational signatures, molecular subtypes, and significantly mutated genes (SMGs) were determined, and their connections with ICI response and outcome were also evaluated. We extracted a total of six mutational signatures across all samples. Among, a mutational signature featured by T > C substitutions was identified to associate with an ICI resistance. A molecular subtype determined based on mutational activities was connected with a significantly improved ICI response rate and outcome. Totaling 50 SMGs were identified, and we observed that patients with COL11A1 or COL4A6 mutations exhibited a superior ICI treatment efficacy than those without such mutations. In this study, we uncovered several novel molecular determinants of cancer immunotherapy response under a multiple-cancer setting, which provides clues for enrolling patients to receive immunotherapy and customizing personalized treatment strategies.

Natural history and genetic spectrum of the Turkish metaphyseal dysplasia cohort, including rare types caused by biallelic COL10A1, COL2A1, and LBR variants.

Metaphyseal chondrodysplasias are a heterogeneous group of diseases characterized by short and bowed long bones and metaphyseal abnormality. The aim of this study is to investigate the genetic etiology and prognostic findings in patients with metaphyseal dysplasia. Twenty-four Turkish patients were included in this study and 13 of them were followed for 2-21years. COL10A1, RMRP sequencing and whole exome sequencing were performed. Results: Seven heterozygous pathogenic variants in COL10A1 were detected in 17 patients with Schmid type metaphyseal chondrodysplasia(MCDS). The phenotype was more severe in patients with heterozygous missense variants (one in signal peptide domain at the N-terminus of the protein, the other, class-1 group mutation at NC1 domain) compared to the patients with truncating variants. Short stature and coxa vara deformity appeared after 3 and 5years of age, respectively, while large femoral head resolved after the age of 13years in MCDS group. Interestingly, one patient with severe phenotype also had a biallelic missense variant in NC1 domain of COL10A1. Three patients with biallelic mutations in RMRP had prenatal onset short stature with short limb, and typical findings of cartilage hair hypoplasia (CHH). While immunodeficiency or recurrent infections were not observed, resistant congenital anemia was detected in one. Biallelic mutation in LBR was described in a patient with prenatal onset short stature, short and curved limb and metaphyseal abnormalities. Unlike previously reported patients, this patient had ectodermal findings, similar to CHH. A biallelic COL2A1 mutation was also found in the patient with lower limb deformities and metaphyseal involvement without vertebral and epiphyseal changes. Long-term clinical characteristics are presented in a metaphyseal dysplasia cohort, including rare types caused by biallelic COL10A1, COL2A1, and LBR variants. We also point out that the domains where mutations on COL10A1 take place are important in the genotype-phenotype relationship.

Biology and Management of High-Grade Chondrosarcoma: An Update on Targets and Treatment Options.

This review provides an overview of histopathology, clinical presentation, molecular pathways, and potential new systemic treatments of high-grade chondrosarcomas (CS), including grade 2−3 conventional, dedifferentiated, and mesenchymal CS. The diagnosis of CS combines radiological and histological data in conjunction with patient clinical presentations. Conventional CS is the most frequent subtype of CS (85%) and represents about 25% of primary bone tumors in adults; they can be categorized according to their bone location into central, peripheral, and periosteal chondrosarcomas. Central and peripheral CS differ at the molecular level with either IDH1/2 mutations or EXT1/2 mutations, respectively. CDKN2A/B deletions are also frequent in conventional CS, as well as COL2A1 mutations. Dedifferentiated CS develops when low-grade conventional CS transforms into a high-grade sarcoma and most frequently exhibits features of osteosarcoma, fibrosarcoma, or undifferentiated pleomorphic sarcoma. Their molecular characteristics are similar to conventional CS. Mesenchymal CS is a totally different pathological entity exhibiting recurrent translocations. Their clinical presentation and management are different too. The standard treatment of CSs is wide en-bloc resection. CS are relatively radiotherapy resistant; therefore, doses >60 Gy are needed in an attempt to achieve local control in unresectable tumors. Chemotherapy is possibly effective in mesenchymal chondrosarcoma and is of uncertain value in dedifferentiated chondrosarcoma. Due to resistance to standard anticancer agents, the prognosis is poor in patients with metastatic or unresectable chondrosarcomas. Recently, the refined characterization of the molecular profile, as well as the development of new treatments, allow new therapeutic options for these rare tumors. The efficiency of IDH1 inhibitors in other malignancies suggests that these inhibitors will be part of IDH1/2 mutated conventional CS management soon. Other treatment approaches, such as PIK3-AKT-mTOR inhibitors, cell cycle inhibitors, and epigenetic or immune modulators based on improving our understanding of CS molecular biology, are emerging.

Identification of COL1A1/2 Mutations and Fusions With Noncoding RNA Genes in Bizarre Parosteal Osteochondromatous Proliferation (Nora Lesion)

Bizarre parosteal osteochondromatous proliferation (BPOP) (Nora lesion) is a benign bone surface lesion, which most commonly occurs in the digits of young patients and has a high rate of recurrence. Histologically, it is composed of a mixture of disorganized bone, cartilage, and spindle cells in variable proportions and characterized by amorphous “blue bone” mineralization. Recurrent chromosomal abnormalities, including t(1;17)(q32-42;q21-23) and inv(7)(q21.1-22q31.3-32), have been reported in BPOP. However, the exact genes involved in the rearrangements remain unknown. In this study, we analyzed 8 BPOP cases affecting the fingers, toe, ulna, radius, and fibula of 5 female and 3 male patients, aged 5 to 68 years. RNA sequencing of 5 cases identified genetic fusions between COL1A2 and LINC-PINT in 3 cases and COL1A1::MIR29B2CHG fusion in 1, both validated using fluorescence in situ hybridization and reverse transcription (RT)-PCR. The remaining fusion-negative case harbored 3 COL1A1 mutations as revealed by whole-exome sequencing and confirmed using Sanger sequencing. All these genetic alterations were predicted to cause frameshift and/or truncation of COL1A1/2. The chromosomal locations of COL1A2 (7q21.3), LINC-PINT (7q32.3), COL1A1 (17q21.33), and MIR29B2CHG (1q32.2) were consistent with the breakpoints identified in the previous cytogenetic studies. Subsequent screening of 3 BPOPs using fluorescence in situ hybridization identified 1 additional case each with COL1A1 or COL1A2 rearrangement. Our findings are consistent with reported chromosomal abnormalities and implicate the disruption of type I collagen, and perhaps of either noncoding RNA gene as a tumor suppressor, in the tumorigenesis of BPOP. The prevalence and tumorigenic mechanisms of these COL1A1/2 alterations in BPOP require further investigation.

Collagen type VII α1 chain: A promising prognostic and immune infiltration biomarker of pancreatic cancer.

Pancreatic cancer (PC) is a stubborn malignancy with high lethality and a low 5-year overall survival (OS) rate. Collagen type VII α1 chain (COL7A1), a major component of the extracellular matrix, serves important roles in numerous physiological processes and various illnesses. COL7A1 protein acts as an anchoring fibril between the external epithelial cells and the underlying stroma, and mutation of COL7A1 could cause recessive dystrophic epidermolysis bullosa. Raw data for PC were acquired from The Cancer Genome Atlas and the Gene Expression Omnibus database, and raw data for the normal pancreas were obtained from the Genotype-Tissue Expression database. COL7A1 mRNA expression in PC tissues was compared with that in either paired (GSE15471 dataset) or unpaired (all other data) normal pancreas tissues. The association between COL7A1 mRNA expression and clinicopathological factors was assessed using logistic regression analysis. Cox analysis and Kaplan-Meier analysis were used to evaluate the role of COL7A1 mRNA expression in prognosis and nomograms were constructed. Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes analysis, Gene Set Enrichment Analysis (GSEA) and single-sample GSEA (ssGSEA) were performed to evaluate the relevant functions of COL7A1 and correlation with immune cell infiltration. Furthermore, reverse transcription-quantitative PCR was used to assess the mRNA expression levels of COL7A1 in PC. The present study demonstrated that COL7A1 mRNA expression was higher in PC tissues compared with in normal pancreas tissues. The Kaplan-Meier survival analysis indicated that patients with PC with high COL7A1 mRNA expression had shorter overall survival (OS), disease-specific survival (DSS) and progression-free interval (PFI) times compared with patients with PC with low COL7A1 mRNA expression. Multivariate analysis demonstrated that COL7A1 mRNA expression was an independent risk factor for OS, DSS and PFI. Nomogram and calibration plots were constructed to predict the prognosis of patients with PC. GSEA demonstrated that high mRNA expression levels of COL7A1 were associated with multiple cancer-related pathways. ssGSEA analysis indicated that COL7A1 expression was positively associated with natural killer CD56bright cells and T helper (Th)2 cells, and negatively associated with Th17 cells and eosinophils. The results of the present study suggested that COL7A1 could be an independent biomarker and an influential moderator of immune infiltration in PC.

A Rare Pathogenic Variant in the SERPINF1 Gene in Association with Early-Onset Severe Presentation of Autosomal Recessive Type of Osteogenesis Imperfecta VI: A Case Report

Osteogenesis imperfecta (OI) refers to a group of genetic disorders with the typical clinical presentation of increased bone fragility. More than 90% of OI cases have an underlying genetic mutation in the collagen genes COL1A1 or COL1A2. However, there are now 22 different recognized OI subtypes based on the underlying gene implicated. OI type VI is caused by pathogenic variants in the serine proteinase inhibitor clade F (SERPINF1) gene. In this case study, the patient was a 4-year-old female, born in a consanguineous family, with a history of delayed gross motor milestones and recurrent fractures after trivial trauma since the age of 8 months. The results of skeletal surveys and bone scans indicated that the patient suffered from OI. To confirm the diagnosis, we performed a next-generation sequencing (NGS) analysis of genes implicated in OI using the TruSight One NGS Panel. Bioinformatics analysis showed the presence of a rare pathogenic variant in exon 7 of the SERPINF1 gene in a homozygous state (NM_002615.5:c.907C>T; NP_002606.3:p.Arg303Ter; ClinVar submission ID: SUB10491966). The variant results in the termination of the polypeptide chain at position 303. Targeted capillary sequencing confirmed the presence of this variant in a homozygous state in the patient and in heterozygous state for both parents. Additionally, the patient’s younger sibling, aged 10 months, harbored the variant in a homozygous state. The sibling started bisphosphonate therapy and did not suffer any fractures in over 2 years after initiating the therapy. The etiological genetic diagnosis helped provide genetic counseling to the family. This highlights the utility of NGS for the confirmation of a clinical analysis in cases where alterations in multiple genes can result in similar clinical presentation.

A Case of Bilateral Cochlear Implantation for Congenital Visual-Auditory Dual Disability Associated with Wolfram Syndrome and Osteogenesis Imperfecta

We report a case of bilateral cochlear implant surgery performed for profound sensorineural hearing loss in a 2-year-old girl with Wolfram syndrome and osteogenesis imperfecta type I. Wolfram syndrome is a rare autosomal-recessive genetic disorder characterized by juvenile diabetes mellitus and visual impairment. The hearing loss in Wolfram syndrome is typically a slowly progressive sensorineural hearing loss, primarily in the high-frequency range. Genetic testing of our patient showed mutations in WFS1 and COL1A1. Bilateral cochlear implant surgery was performed, because adequate wearing thresholds could not be achieved with hearing aids. This report is the first case of a patient with Wolfram syndrome with profound congenital hearing loss who benefited from cochlear implant surgery. The patient had a visual-auditory dual disability and lacked external stimuli. The cochlear implant provided valuable auditory compensation to ensure auditory stimulation. In the future, it is necessary to continue comprehensive rehabilitation for the patient with collaboration among the parents, speech-language pathologists, and rehabilitation facilities.

Tendon properties in a mouse model of severe osteogenesis imperfecta

ABSTRACT Purpose/Aim of the study Osteogenesis imperfecta is a heritable bone disorder that is usually caused by mutations in collagen type I encoding genes. The impact of such mutations on tendons, a structure with high collagen type I content, remains largely unexplored. We hypothesized that tendon properties are abnormal in the context of a mutation affecting collagen type I. The main purpose of the study was to assess the anatomical, mechanical, and material tendon properties of Col1a1 Jrt/+ mice, a model of severe dominant OI. Materials and Methods The Flexor Digitorum Longus (FDL) tendon of Col1a1 Jrt/+ mice and wild-type littermates (WT) was assessed with in vitro mechanical testing. Results The results showed that width and thickness of FDL tendons were about 40% larger in WT (p < 0.01) than in Col1a1 Jrt/+ mice, whereas the cross-sectional area was 138% larger (p < 0.001). The stiffness, peak- and yield-force were between 160% and 194% higher in WT vs. Col1a1 Jrt/+ mice. The material properties did not show significant differences between mouse strains with differences <15% between WT and Col1a1 Jrt/+ (p > 0.05). Analysis of the Achilles tendon collagen showed no difference between mice strains for the content but collagen solubility in acetic acid was 66% higher in WT than in Col1a1 Jrt/+ (p < 0.001). Conclusions This study shows that the FDL tendon of Col1a1 Jrt/+ mice has reduced mechanical properties but apparently normal material properties. It remains unclear whether the tendon phenotype of Col1a1 Jrt/+ mice is secondary to muscle weakness or a direct effect of the Col1a1 mutation or a combination of both.

Trial of Beremagene Geperpavec (B-VEC) for Dystrophic Epidermolysis Bullosa

BackgroundDystrophic epidermolysis bullosa is a rare genetic blistering skin disease caused by mutations in COL7A1, which encodes type VII collagen (C7). Beremagene geperpavec (B-VEC) is a topical investigational herpes simplex virus type 1 (HSV-1)–based gene therapy designed to restore C7 protein by delivering COL7A1.MethodsWe conducted a phase 3, double-blind, intrapatient randomized, placebo-controlled trial involving patients 6 months of age or older with genetically confirmed dystrophic epidermolysis bullosa. For each patient, a primary wound pair was selected, with the wounds matched according to size, region, and appearance. The wounds within each pair were randomly assigned in a 1:1 ratio to receive weekly application of either B-VEC or placebo for 26 weeks. The primary end point was complete wound healing of treated as compared with untreated wounds at 6 months. Secondary end points included complete wound healing at 3 months and the change from baseline to weeks 22, 24, and 26 in pain severity during changes in wound dressing, assessed with the use of a visual analogue scale (scores range from 0 to 10, with higher scores indicating greater pain).ResultsPrimary wound pairs were exposed to B-VEC and placebo in 31 patients. At 6 months, complete wound healing occurred in 67% of the wounds exposed to B-VEC as compared with 22% of those exposed to placebo (difference, 46 percentage points; 95% confidence interval [CI], 24 to 68; P=0.002). Complete wound healing at 3 months occurred in 71% of the wounds exposed to B-VEC as compared with 20% of those exposed to placebo (difference, 51 percentage points; 95% CI, 29 to 73; P<0.001). The mean change from baseline to week 22 in pain severity during wound-dressing changes was −0.88 with B-VEC and −0.71 with placebo (adjusted least-squares mean difference, −0.61; 95% CI, −1.10 to −0.13); similar mean changes were observed at weeks 24 and 26. Adverse events with B-VEC and placebo included pruritus and chills.ConclusionsComplete wound healing at 3 and 6 months in patients with dystrophic epidermolysis bullosa was more likely with topical administration of B-VEC than with placebo. Pruritus and mild systemic side effects were observed in patients treated with B-VEC. Longer and larger trials are warranted to determine the durability and side effects of B-VEC for this disease. (Funded by Krystal Biotech; GEM-3 ClinicalTrials.gov number, NCT04491604.)

302 Availability of mRNA Obtained from Peripheral Blood Mononuclear Cells for Mutational Analysis in Dystrophic Epidermolysis Bullosa

Dystrophic epidermolysis bullosa (DEB) is an inheritable blistering disease caused by mutations in COL7A1, which encodes type VII collagen. To address the issue of genotype-phenotype correlations in DEB, analyzing the consequences of COL7A1 mutations using mRNA is indispensable. Herein we established a novel method for testing the effect of mutations in DEB using COL7A1 mRNA extracted from peripheral blood mononuclear cells (PBMCs). We investigated the consequences of four COL7A1 mutations (c.6573 + 1G > C, c.6216 + 5G > T, c.7270C > T and c.2527C > T) in three Japanese individuals with recessive DEB.

296 Nanoneedles for gene editing in Epidermolysis Bullosa

Recessive Dystrophic Epidermolysis Bullosa is an autosomal recessive disorder caused by loss of function mutations in COL7A1 causing mucocutaneous blistering and scarring, with considerable morbidity and mortality. A few early phase gene therapy trials have been reported as potential therapeutic approaches. The targeted nature of base editing is well suited to restore COL7A1 functionality in RDEB, if supported by an effective delivery strategy. Nanoneedles are a “bed of nail” substrate that interface tightly with cells for gene transfer in primary, hard to transfect cells and exposed tissue layers.

128 Characteristics of anemia and its relationship with disease severity in a Spanish cohort of 84 patients with recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa(RDEB), due to mutations in COL7A1 encoding collagen 7, is a rare incurable skin fragility disease accompanied by multiple complications being chronic anemia one of the main. The multifactorial etiology of anemia makes it challenging to diagnose and treat. However, data from representative cohort about the exact course of anemia and associated parameters are scarce. Thus, a non-interventional, analytical, observational and cross-sectional study was performed by recruiting 84 patients (1-67 years:40 women, 44 men), genetically diagnosed with RDEB, under follow-up at the Spanish EB reference unit in Madrid, since March 2021 until March 2022.

283 Optimising specificity and applicability of base editing for COL7A1 mutations in recessive dystrophic epidermolysis bullosa

Base and prime editors are novel CRISPR variants that reduce the risk of off-target effects by avoiding double-stranded DNA cleavage, bypassing the need for homology-directed repair. As such, these tools offer great therapeutic potential for inherited skin diseases such as recessive dystrophic epidermolysis bullosa (RDEB), a severe blistering skin disorder caused by bi-allelic loss-of-function mutations in COL7A1, which encodes type VII collagen (C7) the major component of anchoring fibrils in skin basement membrane.

299 High efficiency and safe base editor correction of recurrent COL7A1 mutations underlying dominant dystrophic epidermolysis bullosa

Dominant dystrophic epidermolysis bullosa (DDEB) is an inherited blistering skin disease caused by heterozygous mutations in COL7A1, which encodes type VII collagen (C7), the major component of anchoring fibrils that maintain the integrity of the dermal-epidermal junction. Most COL7A1 mutations in DDEB are single nucleotide variants, resulting in glycine substitutions within the C7 triple helix. Functionally, such mutations cause impaired assembly or secretion of C7 and result in dominant-negative interference through faulty C7 assembly of wild-type and mutant chains into anchoring fibrils.

290 Strategies to improve in vivo survival of Mesenchymal Stromal Cells after injection in immunodeficient mice

Recessive dystrophic epidermolysis bullosa (RDEB) is one of the most severe skin diseases and is caused by loss-of-function mutations in COL7A1 encoding type VII collagen (C7). Patients with RDEB suffer since birth from skin and mucosal blistering and develop severe local and systemic complications resulting in a poor prognosis. Mesenchymal stromal cells (MSC) have been shown to have therapeutic potential to improve wound healing and skin inflammation in RDEB patients due to their capacity to express C7 and their anti-inflammatory properties.

Abstract 14124: Acute Mitral Regurgitation With Chronic Endocarditis in Type I Osteogenesis Imperfecta

Case Presentation: A 45-year-old man with history of Type I osteogenesis imperfecta (OI) presented with severe shortness of breath and worsening bilateral lower extremity edema for 6 weeks. Paternal family history was significant for Type I OI with early deaths in affected females. Physical examination revealed a distressed man with blue - gray sclerae and jugular venous distention. Cardiopulmonary examination was remarkable for tachycardia, grade IV holosystolic murmur radiating to the axilla, bilateral lung crackles with decreased air entry on the lower lung fields and pitting pedal edema up to mid thighs. TTE and TEE were significant for severe eccentric posterior MR with multiple vegetations versus ruptured chordae and normal systolic function. He underwent an emergency mitral valve replacement complicated by post-operative severe AR requiring redo sternotomy with aortic valve replacement. Histologically, aortic valve leaflets were suggestive of chronic endocarditis with dual negative sets of blood cultures drawn since admission. He was eventually discharged home after an intense cardiac rehabilitation with appropriate follow ups. Discussion: OI is a rare hereditary connective tissue disorder affecting the production of Type I collagen due to mutations in COL1A1 and COL1A2 genes. Although lesser known, OI valvulopathy is typically limited to the left sided structures, for unknown reasons, with the most common valvular anomaly being AR followed by MR. Despite the dramatic cardiac involvement in our patient and known mortality risk associated with surgical intervention, prompt evaluation and early intervention led to a successful outcome.