Background-Left internal mammary arteries (LIMAs) synthesize endothelium-derived hyperpolarizing factor (EDHF), a short-lived K ϩ channel activator that persists after inhibition of nitric oxide (NO) and prostaglandin synthesis. EDHF hyperpolarizes and relaxes smooth muscle cells (SMCs). The identity of EDHF in humans is unknown. We hypothesized that EDHF (1) is 11,12-epoxyeicosatrienoic acid (11,12-EET); (2) is generated by cytochrome P450-2C, CYP450-2C; and (3)

Background-Alveolar hypoxia acutely elicits pulmonary vasoconstriction (HPV). Chronic hypoxia (CH), despiteattenuating HPV, causes pulmonary hypertension (CH-PHT). HPV results, in part, from inhibition of O 2 -sensitive, voltage-gated potassium channels (Kv) in pulmonary artery smooth muscle cells (PASMCs). CH decreases Kv channel current/expression and depolarizes and causes Ca 2ϩ overload in PASMCs. We hypothesize that Kv gene transfer would normalize the pulmonary circulation (restore HPV and reduce CH-PHT), despite ongoing hypoxia. Methods and Results-Adult male Sprague-Dawley rats were exposed to normoxia or CH for 3 to 4 weeks and then nebulized orotracheally with saline or adenovirus (Ad5) carrying genes for the reporter, green fluorescent protein reporterϮhuman Kv1.5 (cloned from normal PA). HPV was assessed in isolated lungs. Hemodynamics, including Fick and thermodilution cardiac output, were measured in vivo 3 and 14 days after gene therapy by use of micromanometer-tipped catheters. Transgene expression, measured by quantitative RT-PCR, was confined to the lung, persisted for 2 to 3 weeks, and did not alter endogenous Kv1.5 levels. Ad5-Kv1.5 caused no mortality or morbidity, except for sporadic, mild elevation of liver transaminases. Ad5-Kv1.5 restored the O 2 -sensitive K ϩ current of PASMCs, normalized HPV, and reduced pulmonary vascular resistance. Pulmonary vascular resistance decreased at day 2 because of increased cardiac output, and remained reduced at day 14, at which time there was concomitant regression of right ventricular hypertrophy and PA medial hypertrophy. Conclusions-Kv1.5 is an important O 2 -sensitive channel and potential therapeutic target in PHT. Kv1.5 gene therapy restores HPV and improves PHT. This is, to the best of our knowledge, the first example of K ϩ channel gene therapy for a vascular disease.

Background— Glutaraldehyde fixation (G-F) decreases but likely does not eliminate the antigenicity of bioprosthetic heart valves. Rejection (with secondary dystrophic calcification) may be why G-F xenograft valves fail, especially in young patients, who are more immunocompetent than the elderly. Therefore, we sought to determine whether rejection of G-F xenograft occurs and to correlate this with graft calcification. Methods and Results— Ascending aortas/valves (from rats [syngeneic] or guinea pigs [xenogeneic]) were transplanted (fresh or after 48 hour of G-F) into the infrarenal aortas of young rat recipients for 20 days. A xenogeneic group was also treated with steroids until graft harvest. The valves and media/adventitia were scored blindly for inflammation (0 to 4). Percent graft infiltration by T cells/macrophages was determined (immunohistochemistry), and rat IgG ELISAs were performed. There was >3 times more valve inflammation, >10 times more valve T-cell/macrophage infiltrate, and >3 times antibody rise in the G-F xenogeneic groups compared with the fresh syngeneic or the G-F syngeneic groups ( P <0.05). There was >2 times more adventitial inflammation and T-cell/macrophage infiltrate in the xenogeneic groups ( P <0.05). Steroid treatment decreased inflammation and antibody rise in the xenogeneic groups ( P <0.05). Correlation analysis revealed media/adventitia inflammation ( P =0.02) and percent macrophage ( P =0.01) infiltration to be predictors of calcification. Conclusions— G-F xenografts have cellular/humoral rejection and calcify secondarily.