Cardiomyocyte-specific RXFP1 overexpression protects against pressure overload-induced cardiac dysfunction independently of relaxin.

Heart failure (HF) prevalence is rising due to reduced early mortality and demographic change. Relaxin (RLN) mediates protective effects in the cardiovascular system through Relaxin-receptor 1 (RXFP1). Cardiac overexpression of RXFP1 with additional RLN supplementation attenuated HF in the pressure-overload transverse aortic constriction (TAC) model. Here, we hypothesized that robust transgenic RXFP1 overexpression in cardiomyocytes (CM) protects from TAC-induced HF even in the absence of RLN. Hence, transgenic mice with a CM-specific overexpression of human RXFP1 (hRXFP1tg) were generated. Receptor functionality was demonstrated by in vivo hemodynamics, where the administration of RLN induced positive inotropy strictly in hRXFP1tg. An increase in phospholamban-phosphorylation at serine 16 was identified as a molecular correlate. hRXFP1tg were protected from TAC without additional RLN administration, presenting not only less decline in systolic left ventricular (LV) function but also abrogated LV dilation and pulmonary congestion compared to WT mice. Molecularly, transgenic hearts exhibited not only a significantly attenuated fetal and fibrotic gene activation but also demonstrated less fibrotic tissue and CM hypertrophy in histological sections. These protective effects were evident in both sexes. Similar cardioprotective effects of hRXFP1tg were detectable in a RLN-knockout model, suggesting an alternative mechanism of receptor activation through intrinsic activity, alternative endogenous ligands or crosstalk with other receptors. In summary, CM-specific RXFP1 overexpression provides protection against TAC even in the absence of endogenous RLN. This suggests RXFP1 overexpression as a potential therapeutic approach for HF, offering baseline protection with optional RLN supplementation for specific activation.

[Cardiomyopathy in a 22-year-old man with a long history of methamphetamine abuse]. / Kardiomyopathie bei einem 22-Jährigen mit langjährigem Methamphetaminkonsum.

This article presents the case of a 22-year-old male patient with cardiomyopathy associated with a long history of methamphetamine abuse. Echocardiography revealed a dilated cardiomyopathy with highly reduced systolic pump function and severe mitral valve regurgitation. Inotropic treatment and MitraClip® (Abbott Vascular, Santa Clara, CA, USA) implantation resulted in enhancement of hemodynamics. The rising prevalence of methamphetamine abuse should give reason to raise awareness for the diagnostic work-up and patient history particularly in cases of unexplained cardiomyopathy in young patients.

Transient elevation of high-sensitive troponin T after Cardioband implantation.

BACKGROUND: The Cardioband system enables percutaneous surgical-like direct mitral valve annuloplasty and, thereby, repair of severe functional mitral valve regurgitation (MR) in patients with advanced systolic heart failure (HF) and dilation of the left ventricular (LV) annulus. Since the device is anchored by screws in the LV annulus, limited myocardial injury is likely to occur. METHODS AND RESULTS: Five patients (Society of Thoracic Surgeons score: 2.7 ± 0.7%) with severe HF (LV ejection fraction [LVEF]: 17 ± 1%; LV end-diastolic diameter [LVEDD]: 71 ± 3 mm) were treated with the Cardioband (sizes C-F) receiving 14-17 screws in the LV annulus region. Myocardial injury was monitored by measuring high-sensitive cardiac troponin T (hsTnT) levels and by echocardiography. All patients showed significant periprocedural increase in hsTnT levels. Peak hsTnT concentration was reached between day 1 and day 6 (593 ± 141 pg/ml). None of the patients showed clinical signs of myocardial infarction, ST-segment elevation, new onset of deteriorated myocardial wall motion, or new ventricular tachycardia. hsTnT levels normalized in all patients after 14 days (hsTnT on day 0: 34 ± 6 pg/ml vs. hsTnT on day 14: 36 ± 6 pg/ml; p = 0.604). This nonischemic hsTnT kinetics was compared to a sixth patient who experienced proximal damage of the left circumflex artery (LCX) and ST-segment elevation during the Cardioband procedure, followed by immediate repair of the LCX, avoiding structural damage of the LV. CONCLUSION: Cardioband implantation is accompanied by significant elevation of hsTnT without causing structural myocardial damage or clinical symptoms such as worsening of LV function, new-onset LV regions exhibiting reduced wall motion, or ventricular tachycardia.

Targeting GRK2 by gene therapy for heart failure: benefits above ß-blockade.

Heart failure (HF) is a common pathological end point for several cardiac diseases. Despite reasonable achievements in pharmacological, electrophysiological and surgical treatments, prognosis for chronic HF remains poor. Modern therapies are generally symptom oriented and do not currently address specific intracellular molecular signaling abnormalities. Therefore, new and innovative therapeutic approaches are warranted and, ideally, these could at least complement established therapeutic options if not replace them. Gene therapy has potential to serve in this regard in HF as vectors can be directed toward diseased myocytes and directly target intracellular signaling abnormalities. Within this review, we will dissect the adrenergic system contributing to HF development and progression with special emphasis on G-protein-coupled receptor kinase 2 (GRK2). The levels and activity of GRK2 are increased in HF and we and others have demonstrated that this kinase is a major molecular culprit in HF. We will cover the evidence supporting gene therapy directed against myocardial as well as adrenal GRK2 to improve the function and structure of the failing heart and how these strategies may offer complementary and synergistic effects with the existing HF mainstay therapy of ß-adrenergic receptor antagonism.

Gene therapy targets in heart failure: the path to translation.

Heart failure (HF) is the common end point of cardiac diseases. Despite the optimization of therapeutic strategies and the consequent overall reduction in HF-related mortality, the key underlying intracellular signal transduction abnormalities have not been addressed directly. In this regard, the gaps in modern HF therapy include derangement of ß-adrenergic receptor (ß-AR) signaling, Ca(2+) disbalances, cardiac myocyte death, diastolic dysfunction, and monogenetic cardiomyopathies. In this review we discuss the potential of gene therapy to fill these gaps and rectify abnormalities in intracellular signaling. We also examine current vector technology and currently available vector-delivery strategies, and we delineate promising gene therapy structures. Finally, we analyze potential limitations related to the transfer of successful preclinical gene therapy approaches to HF treatment in the clinic, as well as impending strategies aimed at overcoming these limitations.

Cardio-specific long-term gene expression in a porcine model after selective pressure-regulated retroinfusion of adeno-associated viral (AAV) vectors.

Cornerstone for an efficient cardiac gene therapy is the need for a vector system, which enables selective and long-term expression of the gene of interest. In rodent animal models adeno-associated viral (AAV) vectors like AAV-6 have been shown to efficiently transduce cardiomyocytes. However, since significant species-dependent differences in transduction characteristics exist, large animal models are of imminent need for preclinical evaluations. We compared gene transfer efficiencies of AAV-6 and heparin binding site-deleted AAV-2 vectors in a porcine model. Application of the AAVs was performed by pressure-regulated retroinfusion of the anterior interventricular cardiac vein, which has been previously shown to efficiently deliver genes to the myocardium (3.5 x 10(10) viral genomes per animal; n=5 animals per group). All vectors harbored a luciferase reporter gene under control of a cytomegalovirus (CMV)-enhanced 1.5 kb rat myosin light chain promoter (CMV-MLC2v). Expression levels were evaluated 4 weeks after gene transfer by determining luciferase activities. To rule out a systemic spillover peripheral tissue was analyzed by PCR for the presence of vector genomes. Selective retroinfusion of AAV serotype 6 vectors into the anterior cardiac vein substantially increased reporter gene expression in the targeted distal left anterior descending (LAD) territory (65 943+/-31 122 vs control territory 294+/-69, P<0.05). Retroinfusion of AAV-2 vectors showed lower transgene expression, which could be increased with coadministration of recombinant human vascular endothelial growth factor (1365+/-707 no vascular endothelial growth factor (VEGF) vs 38 760+/-2448 with VEGF, P<0.05). Significant transgene expression was not detected in other organs than the heart, although vector genomes were detected also in the lung and liver. Thus, selective retroinfusion of AAV-6 into the coronary vein led to efficient long-term myocardial reporter gene expression in the targeted LAD area of the porcine heart. Coapplication of VEGF significantly increased transduction efficiency of AAV-2.