siRNA-mediated knockdown of HES5 in PAH sPASMCs also displayed evidence of increased expression of the vSMC contractile markers MYH11 (encoding myosin heavy chain) and SMTN (encoding smoothelin) [39] compared to untreated or scrambled siRNA-treated PAH sPASMCs [8]. Here, HES5 is linked to pulmonary arterial hypertension.