We found that TGF‐betaR1 and smad4 were possible downstream targets of miR‐140‐5p, reduction in miR‐140‐5p in PAH might stimulate TGF‐beta1/Smad4 pathway by upregulating TGF‐betaR1 and smad4. Here, SMAD4 is linked to pulmonary arterial hypertension.