ACE2 and pulmonary arterial hypertension: Zhang et al. (210) identified a role for the HIF-1-let-7b-ACE2 axis: miR-let-7b expression was elevated in rat lungs under chronic hypoxic conditions, and in vitro and in vivo experiments showed that let-7b promoted PAH by inhibiting ACE2 expression and thus inducing PASMC proliferation and migration.