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Cardiac hypertrophy and consequent contractile dysfunction continue to burden Western society. Cardiomyocyte cyclic AMP (cAMP) and calcium are driving forces behind cardiomyocyte contraction. Distortion of their balance may induce HF, but specific therapies aiming at restoring physiological cAMP/calcium signaling are lacking.We recently identified microRNA-139 (miR-139) to be downregulated in failing human hearts. MiR-139 resides in the phosphodiesterase gene PDE2A and is predicted to target several phosphodiesterase messengers. In view of the central role of phosphodiesterases in controlling cardiac cAMP and calcium signaling, we hypothesized that miR-139 may affect HF progression by fine-tuning cAMP and calcium balances.Adeno-associated virus serotype 9 (AAV9), either empty control or expressing pre-miR-139, was administered to male C57Bl/6J mice. After allowing transgene expression for 3 weeks, mice were subjected to sham treatment or 4 weeks of pressure overload by subcutaneous Angiotensin II infusion (AngII, 2,5 mg/(kg·d). MiR-139 overexpression mildly aggravated HF development upon AngII with echocardiographically measured fractional shortening decreasing by 24±7% in AAV9-control AngII and by 46±5% in AAV9-pre-miR-139 AngII (n>11/group; p=0.14). In AAV9-control mice, AngII infusion led to concentric hypertrophy with an increased relative wall thickness (RWT) of 35±6%, whereas mice overexpressing miR-139 showed a rather eccentric form of hypertrophy with an increased RWT of 14±7% (p<0.05). The fraction of unphosphorylated cardiac troponin I (cTnI), a substrate of the cAMP dependent protein kinase A (PKA), tended to increase upon AngII infusion only in mice overexpressing miR-139 (n=4/group; p=0.11), indicating a reduced relaxation rate due to increased calcium sensitivity, a feature commonly observed in HF. Complimentary to these data, in vivo knockdown of mir-139 by cholesterol-tagged antagomiRs (20mg/kg) on three consecutive days before start of AngII infusion dampened the development of pressure overload-induced cardiac hypertrophy (increase in HW/TL: ctrl: 48±10%, n=4; antagomiR: 25±7%, n=7; p=0.16).In conclusion, cardiac downregulation of miR-139 upon pressure overload is a protective response to preserve cardiac function. AAV9-mediated overexpression of miR-139 promotes cardiac dilation and predisposes to HF. Upcoming experiments will aim at defining the molecular mechanism by which miR-139/phosphodiesterase signaling affects cardiac pathophysiology. [ABSTRACT FROM PUBLISHER]

Purpose: Despite major advances in the treatment of cardiovascular diseases, heart failure (HF) remains one of the top causes of death world-wide. The implications of microRNAs in this process are well accepted but still only incompletely understood. The microRNAs 221-3p and 222-3p are processed from a common precursor and share the same seed sequence and thus form the microRNA-221/222 family (miR-221/222). Both microRNAs were found to be involved in myoblast differentiation and are upregulated after aortic banding in mice. We therefore hypothesized that the miR-221/222 family is involved in the pathophysiology of cardiac hypertrophy and failure upon pressure overload.Methods and results: In a genome wide screen for microRNAs regulated in human dilated cardiomyopathy, we found miR-222 levels to be significantly decreased (p<0.01). MiR-221/222 were also downregulated in neonatal rat cardiomyocytes (nRCMs) upon stimulation with the pro-hypertrophic compound phenylephrine (PE) (p<0.05). Interestingly, the overexpression of these miRs in nRCMs using mimics significantly blunted the induction of the hypertrophy markers Bnp and skeletal alpha actin (Acta1) in nRCMs upon stimulation with PE.To investigate the role of miR-221/222 in pressure overload-induced heart failure, we simultaneously injected anti-miR-221 and anti-miR-222 antisense oligonucleotides (ASOs) or scrambled control oligonucleotides (SCOs) in male C57BL/6 mice 3 days before implanting angiotensin II-filled osmotic minipumps (AngII, 2.5 mg/(kg d)). After 4 weeks, we assessed cardiac function and histology as well as molecular changes in the left ventricle. Surprisingly, we did not find an effect of miR-221/222 inhibition on overall cardiac hypertrophy after AngII infusion (HW/TL: 8.04 vs 7.92 mg/mm, p>0.05). However, interstitial fibrosis was significantly increased upon AngII stimulation in mice that received miR-221/222 ASOs as compared to SCOs (6.1 vs 3.7% LV area, p<0.05). On the mRNA level, these mice also showed a 2.9-fold higher induction of Anp upon AngII stimulation (p~0.10), in line with anti-hypertrophic effects of miR-221/222 mimics shown in vitro.Conclusions: Taken together, our results indicate a protective effect of the microRNA-221/222 family in the stressed heart. Inhibition of miR-221/222 prior to pressure overload in mice led to increased fibrosis indicating adverse remodeling. In vitro, a direct effect of miR-221/222 overexpression on the hypertrophic response of nRCMs could be shown. Further experiments will aim at identifying the function of the miR-221/222 family both in cardiac fibroblast and cardiomyocytes. [ABSTRACT FROM PUBLISHER]