SFRP1 and pulmonary arterial hypertension: Expression of Wnt ligands (Wnt1, Wnt3a, and Wnt5a) and Wnt signaling upstream regulator genes (Frizzled1 and 2 receptors and sFRP-1) and intracellular effectors (Axin1 and GSK3β) were investigated in pulmonary hypertensive rat lungs, 3 and 5 weeks after MCT injury.