Seminars

February 20 2018

1:00 pm 1100 TLSB

Mingxia Gu
Department of Pediatrics Cardiology
Stanford University

Summary

Pulmonary Arterial Hypertension (PAH) is a progressive disorder characterized by endothelial cell (EC) apoptosis, loss of distal vessels, and occlusive vascular remodeling. Current PAH therapies only improve symptoms by amplifying pulmonary arterial (PA) EC-derived vasodilatory mediators, but do not reverse the pathological changes that underlie PAH. Induced pluripotent stem cell (iPSC) derived vascular cells provide a new opportunity to further understand the disease mechanisms and develop novel therapies in a personalized manner. Loss of function mutations in bone morphogenetic protein receptor (BMPR)2 occur in over 70% of familial cases of PAH (FPAH). Intriguingly, only 20% of the mutation carriers develop clinical symptoms, indicating that the mutation is necessary but not sufficient for the disease. Using iPSC-ECs from three families with unaffected mutation carriers (UMC), FPAH patients, and gender-matched controls, we identified patient-specific features of improved function in UMC iPSC-EC attributed to the regulators of BMPR2 signaling or to differentially expressed genes revealed by RNA-Seq analyses. Interestingly, although different families have different compensatory mechanisms, they all lead to the common ‘rescued’ endothelial cell function, which could then be targeted to develop novel therapy for all PAH patients. We therefore carried out a high throughput screen that would assess drug efficacy in reversing PAH EC and smooth muscle cell (SMC) phenotypes. Total of 4,500 bioactive compounds were tested for their ability to improve cell survival in six PAH iPSC-EC lines following serum withdrawal, using a luminescence and/or fluorescence assay measuring Caspase 3/7 activity, an indicator of the cell apoptosis. We identified 3 compounds, an antioxidant, a chloride channel inhibitor, and a tyrosine kinase inhibitor (TKI) not previously tested in PAH, that could be repurposed as they significantly reduced EC apoptosis under serum deprivation in iPSC-EC from all six PAH patients. The 13 compounds that were effective in PAH iPSC-EC from two-five patients included a GSK3β inhibitor, calcineurin inhibitor, SIRT1 activator and another TKI. One of these compounds also improved angiogenesis, activated cell survival pathways, and reduced SMC proliferation. Our study suggests that patient-specific iPSCs serve as a promising platform to identify novel therapies in a variety of vascular pathologies in addition to PAH, where different mechanisms lead to the same phenotypic abnormality.