Functional analysis of cell lines derived from SMAD3-related Loeys-Dietz syndrome patients provides insights into genotype-phenotype relation.

RATIONALE: Pathogenic (P)/likely pathogenic (LP) SMAD3 variants cause Loeys-Dietz syndrome type 3 (LDS3), which is characterized by arterial aneurysms, dissections and tortuosity throughout the vascular system combined with osteoarthritis. OBJECTIVES: Investigate the impact of P/LP SMAD3 variants with functional tests on patient-derived fibroblasts and vascular smooth muscle cells (VSMCs), to optimize interpretation of SMAD3 variants. METHODS: A retrospective analysis on clinical data from individuals with a P/LP SMAD3 variant and functional analyses on SMAD3 patient-derived VSMCs and SMAD3 patient-derived fibroblasts, differentiated into myofibroblasts. RESULTS: Individuals with dominant negative (DN) SMAD3 variant in the MH2 domain exhibited more major events (66.7% vs. 44.0%, P = 0.054), occurring at a younger age compared to those with haploinsufficient (HI) variants. The age at first major event was 35.0 years [IQR 29.0-47.0] in individuals with DN variants in MH2, compared to 46.0 years [IQR 40.0-54.0] in those with HI variants (P = 0.065). Fibroblasts carrying DN SMAD3 variants displayed reduced differentiation potential, contrasting with increased differentiation potential in HI SMAD3 variant fibroblasts. HI SMAD3 variant VSMCs showed elevated SMA expression and altered expression of alternative MYH11 isoforms. DN SMAD3 variant myofibroblasts demonstrated reduced extracellular matrix formation compared to control cell lines. CONCLUSION: Distinguishing between P/LP HI and DN SMAD3 variants can be achieved by assessing differentiation potential, and SMA and MYH11 expression. The differences between DN and HI SMAD3 variant fibroblasts and VSMCs potentially contribute to the differences in disease manifestation. Notably, myofibroblast differentiation seems a suitable alternative in vitro test system compared to VSMCs.

Expanding the genetic and phenotypic spectrum of ACTA2-related vasculopathies in a Dutch cohort.

PURPOSE: Heterozygous pathogenic/likely pathogenic (P/LP) variants in the ACTA2 gene confer a high risk for thoracic aortic aneurysms and aortic dissections. This retrospective multicenter study elucidates the clinical outcome of ACTA2-related vasculopathies. METHODS: Index patients and relatives with a P/LP variant in ACTA2 were included. Data were collected through retrospective review of medical records using a standardized questionnaire. RESULTS: A total of 49 individuals from 28 families participated in our study. In total, 20 different ACTA2 variants were detected. Aortic events occurred in 65% of the cases (78.6% index patients and 47.6% relatives). Male sex and hypertension emerged as significantly associated with aortic events. Of 20 individuals, 5 had an aortic diameter of <45 mm (1.77 inches) at the time of the type A dissection. Mean age at first aortic event was 49.0 ± 12.4 years. Severe surgical complications for type A and type B dissection occurred in 25% and 16.7% of the cases and in-hospital mortality rates were 9.5% and 0%, respectively. CONCLUSION: P/LP ACTA2 variants are associated with an increased risk for an aortic event and age-related penetrance, which emphasizes the importance of early recognition of the disease. Caregivers should be aware of the risk for aortic dissections, even in individuals with aortic diameters within the normal range.

Vascular Ehlers-Danlos Syndrome: A Comprehensive Natural History Study in a Dutch National Cohort of 142 Patients.

BACKGROUND: Vascular Ehlers-Danlos syndrome (vEDS) is a rare connective tissue disorder with a high risk for arterial, bowel, and uterine rupture, caused by heterozygous pathogenic variants in COL3A1. The aim of this cohort study is to provide further insights into the natural history of vEDS and describe genotype-phenotype correlations in a Dutch multicenter cohort to optimize patient care and increase awareness of the disease. METHODS: Individuals with vEDS throughout the Netherlands were included. The phenotype was charted by retrospective analysis of molecular and clinical data, combined with a one-time physical examination. RESULTS: A total of 142 individuals (50% female) participated the study, including 46 index patients (32%). The overall median age at genetic diagnosis was 41.0 years. More than half of the index patients (54.3%) and relatives (53.1%) had a physical appearance highly suggestive of vEDS. In these individuals, major events were not more frequent (P=0.90), but occurred at a younger age (P=0.01). A major event occurred more often and at a younger age in men compared with women (P<0.001 and P=0.004, respectively). Aortic aneurysms (P=0.003) and pneumothoraces (P=0.029) were more frequent in men. Aortic dissection was more frequent in individuals with a COL3A1 variant in the first quarter of the collagen helical domain (P=0.03). CONCLUSIONS: Male sex, type and location of the COL3A1 variant, and physical appearance highly suggestive of vEDS are risk factors for the occurrence and early age of onset of major events. This national multicenter cohort study of Dutch individuals with vEDS provides a valuable basis for improving guidelines for the diagnosing, follow-up, and treatment of individuals with vEDS.