Generation and characterization of Induced Pluripotent Stem Cell models with SMAD3 mutations to study the molecular mechanism of Loeys-Dietz Syndrome Type III aneurysm formation

Loeys-Dietz Syndrome type 3 (LDS3) is caused by pathogenic (P)/likely pathogenic (LP) variants in the SMAD3 gene and is characterized by aneurysm formation and arterial tortuosity, which can lead to life-threatening complications. There is an unmet need for suitable cell models to study LDS3 at a cellular and molecular level. Induced pluripotent stem (iPS) cells offer a promising approach because they can be genetically modified using CRISPR/Cas9 technology and differentiated into disease-relevant cell types. As it is difficult to obtain aortic vascular smooth muscle cells (VSMCs) from patients, iPS cells differentiated into VSMCs provide an ideal model to study cellular aneurysmal phenotypes. In this study, we generated iPS cell models carrying (P/LP) SMAD3 variants. These cell models were generated either by using CRISPR/Cas9 mediated introduction of indels and deletions to introduce SMAD3 variants, or by reprogramming of fibroblasts derived from SMAD3 patients. These iPS cell lines were characterized for SMAD3 expression by Western blotting and validated for pluripotency through immunofluorescence and qPCR. Moreover, the patient-derived iPS cell lines were shown to differentiate into smooth muscle cells (SMCs), which are relevant to study the molecular mechanisms underlying aneurysm formation in LDS3 patients. Our findings highlight the potential of these iPS-based models to investigate the pathophysiology of LDS3 and facilitate the development of therapeutic strategies for aortic aneurysms.