Evaluation of Phosphodiesterase 9A as a Novel Biomarker in Heart Failure with Preserved Ejection Fraction

AIMS: Murine models implicate phosphodiesterase 9A (PDE9A) as a nitric oxide-independent regulator of cyclic guanosine monophosphate and promising novel therapeutic target in heart failure (HF) with preserved ejection fraction (HFpEF). This study describes PDE9A expression in endomyocardial biopsies (EMBs) and peripheral blood mononuclear cells (PBMNCs) from patients with different HF phenotypes. METHODS AND RESULTS: Endomyocardial biopsies and PBMNCs were obtained from patients with HFpEF (n = 24), HF with reduced ejection fraction (n = 22), and inflammatory cardiomyopathy (n = 24) and patients without HF (n = 7). PDE9A expression was increased in EMBs and PBMNCs from patients with HFpEF as compared with other HF phenotypes or subjects without HF. Endomyocardial PDE9A expression in HFpEF correlated with the inflammatory cell count in EMBs, but not with cardiac fibrosis or left ventricular diastolic wall stress. PDE9A expression in PBMNCs was increased in HFpEF patients with higher high-sensitivity C-reactive protein levels and in response to pro-inflammatory stimulation. As a validation cohort, 719 patients with HFpEF and 1106 subjects without HF were identified from the LIFE-Heart study. PDE9A expression in PBMNCs was obtained from array data and displayed an age-dependent distribution. PDE9A levels were elevated and conferred increased risk for HFpEF in middle-aged subjects, but not in elderly HFpEF patients. Following age adjustment, lower PDE9A expression in PBMNCs was associated with worse survival in patients with HFpEF (log-rank test P-value <0.001). CONCLUSION: Expression profiling indicates an up-regulation of endomyocardial PDE9A in different HF phenotypes with the most robust increase in EMBs and PBMNCs from patients with HFpEF. An exclusive risk effect of PDE9A expression on HFpEF in middle-aged patients and an unexpected association with survival calls for further studies to better characterize the role of PDE9A as a treatment target.