Abstract 288: Development Of A Phenotypic Screen With 56 Marfan Syndrome Patient-derived Fibroblasts

Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in the extracellular matrix gene coding for fibrillin-1 (FBN1). MFS leads to aortic aneurysms as key feature. Due to the high genetic diversity within the MFS patient population, genotype-phenotype predictions on disease progression and response to therapy remain challenging. Furthermore, current preclinical murine models represent only a subset of FBN1 mutations, which limits translational studies. In this study, we developed a preclinical model using primary cells of MFS patients that represent genetic and clinical variability in order to develop improved drug strategies. Human primary fibroblasts were isolated from skin biopsies derived from MFS patients (n=56) participating in the COMPARE trial. Human aortic smooth muscle cells (AoSMCs) were isolated from aortic tissue derived from MFS patients undergoing prophylactic aortic surgery (n=4). Long-term cultures in 384-well plates were assessed for the extracellular matrix and disease associated pathways. Analysis of all MFS fibroblasts showed either a reduced or abolished fibrillin-1 extracellular matrix network. Moreover, substantially reduced secretion of fibrillin-1 and asprosin in the culture medium was measured, as compared to healthy control fibroblasts. MFS fibroblasts with an abolished fibrillin-1 matrix were associated with patients with more rapid aortic root diameter growth. Exploring disease-relevant pathways revealed reduced nuclear localization of transcription factor KLF4 in MFS fibroblasts, which associated with the level of fibrillin-1 matrix. As a marker for myofibroblasts, α-smooth muscle actin (ASMA) staining was increased in these MFS fibroblasts. These findings were validated in AoSMC cultures, showing similar MFS fibrillin-1 matrix, nuclear KLF4, and ASMA expression profiles. In conclusion, phenotypic screening of patient-derived cells contributes to improved understanding of disease development and is valuable as preclinical tool for risk assessment and drug development for MFS and related conditions.