Earlier studies have suggested an association between uric acid (UA) and pulmonary arterial hypertension (PAH) severity, but it remains unknown whether UA contributes to the disease pathogenesis.To study the prognostic values of circulating UA at era of current management of PAH and investigate the role of UA in the pulmonary vascular remodelling.Serum UA levels were determined in idiopathic, heritable, or anorexigen PAH at baseline and first re-evaluation in the French PAH registry. We studied protein levels of xanthine oxidase (XO) and the URATv1 transporter in lungs of control and PAH patients and of monocrotaline (MCT) and sugen/hypoxia (SuHx) rats. Functional studies were performed using human pulmonary artery smooth muscle cells (PA-SMCs) and two animal models of pulmonary hypertension (PH).High serum UA levels are associated with a poor prognosis at first follow-up, but not at baseline. Both the generating enzyme XO and URATv1 are upregulated in the wall of remodelled pulmonary arteries in iPAH patients and MCT and SuHx rats. High UA concentrations promote a mild increase in cell growth in iPAH PA-SMCs, but not in control PA-SMCs. Consistent with these observations, we demonstrate that oxonic acid-induced hyperuricemia did not aggravate MCT-induced PH in rats. Finally, we show that chronic treatments of MCT and SuHx rats with benzbromarone mildly attenuate pulmonary vascular remodelling.UA levels in iPAH patients is associated with impaired clinical and hemodynamic profile and might be used as a noninvasive indicator of clinical prognostic during follow-up. Our findings also indicate that metabolism of UA is disturbed in remodelled pulmonary vascular walls in both experimental and human PAH.