Abstract 397: Analysis of Cell Phenotype in Relation to TGFβ Treatment of Aortic Smooth Muscle Cells and Myofibroblasts Isolated from Aortas and Valves of Thoracic Aortic Aneurysm Patients with a Tricuspid or a Bicuspid Valve

Abstract

Background Thoracic aortic aneurysm (TAA) is a pathological widening of the aorta, due to degeneration of extracellular matrix (ECM) and loss of smooth muscle cells (SMCs). Bicuspid aortic valve (BAV) is a congenital disorder present in 1-2 % of the population which makes TAA associated with BAV a common complication. Previously we showed that aortas isolated from BAV and normal tricuspid aortic valve (TAV) patients are different both at gene and protein levels. Particularly, differences in the TGFβ pathway seem to be crucial players in aneurysm development, affecting matrix remodeling and wound healing. Since SMCs and myofibroblasts are the critical cells responsible for these activities, we evaluated different properties of the cells focusing on fibronectin (FN) and its spliced versions, a target gene of TGFβ. Interestingly, extra domain A of FN (EDA) was previously described for its roles in vascular morphogenesis, as well as in processes like migration and proliferation. Methods and results Biopsies from the thoracic aorta and Aortic valves were collected during Elective Aortic Valve Replacement Surgery. mRNA expression was analyzed in the ascending aorta by Affymetrix Exon arrays in patients with TAV (n=46) and BAV (n=77). Expression of EDA was found increased only in dilated aortas from TAV patients but not in BAV patients. Primary SMCs were isolated with the explant outgrowth technique from aortas of BAV and TAV patients (n=15). Myofibroblasts were isolated by collagenase digestion from BAV and TAV valves (n=30). Cells were cultured and treated with TGFβ at a concentration of 20 ng/ml for 6h. TGFβ treatment influenced the splicing of FN and enhanced the formation of EDA-containing FN in SMCs from TAV patients but not in cells derived from BAV patients. We have not observed clear differences in SMC proliferation and migration. Myofibrolasts analysis is ongoing. Conclusions So far, our results suggest that despite a decreased EDA-fibronectin expression in BAV cells, the phenotype of SMCs isolated from BAV and TAV patients in culture does not differ. However, impaired TGFβ signaling that may result in the increased susceptibility of BAV patients to develop TAA could be due to effects on other cell types.