Abstract 13105: The Effect of Mechanical Stress on Cardiac Fibroblasts in Pulmonary Arterial Hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a rare fatal disease with vascular remodeling leading to increased right ventricular pressure followed by fibrosis. To study PAH-induced cardiac fibrosis we develop an in vitro model of the failing right ventricle, for which cardiac fibroblasts (cFBs) were generated from healthy subjects’ and PAH patients’ induced pluripotent stem cells (iPSC). Methods: Confluent iPSC were induced to differentiate by adding 12 μM CHIR99021 for 24h to RPMI supplemented with B27 without insulin. Next, cells recovered for 24 h in RPMI supplemented with B27 without insulin, followed by stimulation with 75 ng/ml FGF2 up to day 20. Finally, the differentiated cells were reseeded and submitted to 10% cyclic stretch at 1 Hz for 4 days using the Flexcell FX-6000 system. Control and PAH cFBs were characterized at gene and protein levels. Results: The differentiated cells had a spindle morphology typical of FBs. Furthermore, the presence of cardiac ( GATA4, TCF21 ) and fibroblast ( VIM, PDGFRα, COL1A1 ) markers at gene and protein levels confirmed the cFB identity. Comparable expression of fibroblast related genes was observed in PAH cFBs as well as controls. Over 4 weeks of culture, iPSC-cFBs increasingly expressed markers of activated FBs ( ACTA2 and POSTN) over time, similar to in vitro adult cFBs. When exposed to mechanical stretch, cell aligned to the stretch direction. Surprisingly, no increase in gene expression of extracellular matrix ( COL1A1, COL3A1 ) or activated fibroblasts ( ACTA2, POSTN ) markers was observed . Interestingly, under static and stretch conditions expression of these genes was increased in PAH cFBs compared to healthy cells. Conclusion: The cellular morphology after differentiation as well as the gene and protein analyses indicate that cFBs were successfully generated. Furthermore, cyclic stretch induced alignment of the cells but was not sufficient to stimulate fibroblast activation in either PAH or healthy cFBs.