MATRIX STIFFENING INDUCES ENDOTHELIAL DYSFUNCTION IN PULMONARY ARTERIAL HYPERTENSION
Thaius Boyd1, Paul Dieffenbach2, Laura Fredenburgh2, Anna Coronata2. Christina Mallarino-Haeger2.
1Haskell Indian Nations University, Lawrence, KS, 2Brigham and Women's Hospital, Boston, MA.
Pulmonary arterial hypertension (PAH) is a devastating disease characterized by progressive breathlessness, worsening hypoxemia, and right-heart failure. Pathologically, PAH leads to vascular remodeling of pulmonary arteries. Our lab has shown vessel stiffening occurs early in PAH and worsens as the diseases progresses. To understand the effect of stiffness on vascular cell phenotypes, we examined pulmonary artery endothelial cells (PAECs) in vitro on discrete matrix stiffnesses recapitulating normal and remodeled vessels. We subsequently disrupted mechanical signaling by siRNA knockdown of YAP and TAZ, key regulators of mechanotransduction, and tested for alterations in remodeling phenotypes. By preventing remodeling through disruption of mechanical signaling, we hope to identify new therapeutic targets in PAH. Human primary PAECs were plated onto discrete-stiffness polyacrylamide gels and assessed for cell proliferation, cell toxicity, gene expression, and cytoskeletal organization. SiRNA transfection was then used to knockdown YAP and TAZ, after which cells were assessed for YAP cellular localization, cell proliferation, cell toxicity, and gene expression. Results show stiff matrix conditions result in increased cell proliferation and YAP/TAZ activity. In contrast, YAP/TAZ knockdown shows reduced cell proliferation, increased cell death, and increased expression of COX-2, an important inhibitor of vascular remodeling. We conclude that matrix stiffness mimicking pathologically remodeled vessels leads to increased cellular proliferation and YAP/TAZ mechanical signaling in PAECs. Reducing YAP and TAZ gene expression reverses these phenotypic changes in stiff matrix and induces genes associated with normal vascular homeostasis. These results suggest that the YAP/TAZ pathway may be an interesting target for future PAH therapy.