TGFB1 and pulmonary arterial hypertension: Using this methodology, we next investigated whether EV-mediated communication from HPASMC-to-HPAEC was altered by excessive TGF-β signalling, as well as by other cytokines involved in PAH including IL-1β, TNF-α and VEGFA, which have been found increased in the serum of PAH patients [30, 31].