Cell Cycle Re-Entry and Mitochondrial Defects in Myc-Mediated Hypertrophic Cardiomyopathy and Heart Failure

While considerable evidence supports the causal relationship between increases in c-Myc (Myc) and cardiomyopathy as a part of a “fetal re-expression” pattern, the functional role of Myc in mechanisms of cardiomyopathy remains unclear. To address this, we developed a bitransgenic mouse that inducibly expresses Myc under the control of the cardiomyocyte-specific MHC promoter. In adult mice the induction of Myc expression in cardiomyocytes in the heart led to the development of severe hypertrophic cardiomyopathy followed by ventricular dysfunction and ultimately death from congestive heart failure. Mechanistically, following Myc activation, cell cycle markers and other indices of DNA replication were significantly increased suggesting that cell cycle-related events might be a primary mechanism of cardiac dysfunction. Furthermore, pathological alterations at the cellular level included alterations in mitochondrial function with dysregulation of mitochondrial biogenesis and defects in electron transport chain complexes I and III. These data are consistent with the known role of Myc in several different pathways including cell cycle activation, mitochondrial proliferation, and apoptosis, and indicate that Myc activation in cardiomyocytes is an important regulator of downstream pathological sequelae. Moreover, our findings indicate that the induction of Myc in cardiomyocytes is sufficient to cause cardiomyopathy and heart failure, and that sustained induction of Myc, leading to cell cycle re-entry in adult cardiomyocytes, represents a maladaptive response for the mature heart

Stem Cell Therapy with Overexpressed VEGF and PDGF Genes Improves Cardiac Function in a Rat Infarct Model

Therapeutic potential was evaluated in a rat model of myocardial infarction using nanofiber-expanded human cord blood derived hematopoietic stem cells (CD133+/CD34+) genetically modified with VEGF plus PDGF genes (VIP).Myocardial function was monitored every two weeks up to six weeks after therapy. Echocardiography revealed time dependent improvement of left ventricular function evaluated by M-mode, fractional shortening, anterior wall tissue velocity, wall motion score index, strain and strain rate in animals treated with VEGF plus PDGF overexpressed stem cells (VIP) compared to nanofiber expanded cells (Exp), freshly isolated cells (FCB) or media control (Media). Improvement observed was as follows: VIP>Exp> FCB>media. Similar trend was noticed in the exercise capacity of rats on a treadmill. These findings correlated with significantly increased neovascularization in ischemic tissue and markedly reduced infarct area in animals in the VIP group. Stem cells in addition to their usual homing sites such as lung, spleen, bone marrow and liver, also migrated to sites of myocardial ischemia. The improvement of cardiac function correlated with expression of heart tissue connexin 43, a gap junctional protein, and heart tissue angiogenesis related protein molecules like VEGF, pNOS3, NOS2 and GSK3. There was no evidence of upregulation in the molecules of oncogenic potential in genetically modified or other stem cell therapy groups.Regenerative therapy using nanofiber-expanded hematopoietic stem cells with overexpression of VEGF and PDGF has a favorable impact on the improvement of rat myocardial function accompanied by upregulation of tissue connexin 43 and pro-angiogenic molecules after infarction

Colchicine for prevention of postpericardiotomy syndrome and postoperative atrial fibrillation : the COPPS-2 randomized clinical trial

IMPORTANCE: Postpericardiotomy syndrome, postoperative atrial fibrillation (AF), and postoperative effusions may be responsible for increased morbidity and health care costs after cardiac surgery. Postoperative use of colchicine prevented these complications in a single trial. OBJECTIVE: To determine the efficacy and safety of perioperative use of oral colchicine in reducing postpericardiotomy syndrome, postoperative AF, and postoperative pericardial or pleural effusions. DESIGN, SETTING, AND PARTICIPANTS: Investigator-initiated, double-blind, placebo-controlled, randomized clinical trial among 360 consecutive candidates for cardiac surgery enrolled in 11 Italian centers between March 2012 and March 2014. At enrollment, mean age of the trial participants was 67.5 years (SD, 10.6 years), 69% were men, and 36% had planned valvular surgery. Main exclusion criteria were absence of sinus rhythm at enrollment, cardiac transplantation, and contraindications to colchicine. INTERVENTIONS: Patients were randomized to receive placebo (n=180) or colchicine (0.5 mg twice daily in patients 6570 kg or 0.5 mg once daily in patients <70 kg; n=180) starting between 48 and 72 hours before surgery and continued for 1 month after surgery. MAIN OUTCOMES AND MEASURES: Occurrence of postpericardiotomy syndrome within 3 months; main secondary study end points were postoperative AF and pericardial or pleural effusion. RESULTS: The primary end point of postpericardiotomy syndrome occurred in 35 patients (19.4%) assigned to colchicine and in 53 (29.4%) assigned to placebo (absolute difference, 10.0%; 95% CI, 1.1%-18.7%; number needed to treat\u2009=\u200910). There were no significant differences between the colchicine and placebo groups for the secondary end points of postoperative AF (colchicine, 61 patients [33.9%]; placebo, 75 patients [41.7%]; absolute difference, 7.8%; 95% CI, -2.2% to 17.6%) or postoperative pericardial/pleural effusion (colchicine, 103 patients [57.2%]; placebo, 106 patients [58.9%]; absolute difference, 1.7%; 95% CI, -8.5% to 11.7%), although there was a reduction in postoperative AF in the prespecified on-treatment analysis (placebo, 61/148 patients [41.2%]; colchicine, 38/141 patients [27.0%]; absolute difference, 14.2%; 95% CI, 3.3%-24.7%). Adverse events occurred in 21 patients (11.7%) in the placebo group vs 36 (20.0%) in the colchicine group (absolute difference, 8.3%; 95% CI; 0.76%-15.9%; number needed to harm\u2009=\u200912), but discontinuation rates were similar. No serious adverse events were observed. CONCLUSIONS AND RELEVANCE: Among patients undergoing cardiac surgery, perioperative use of colchicine compared with placebo reduced the incidence of postpericardiotomy syndrome but not of postoperative AF or postoperative pericardial/pleural effusion. The increased risk of gastrointestinal adverse effects reduced the potential benefits of colchicine in this setting. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT0155218

Influence of acute right ventricular dysfunction on cardiac tamponade

AbstractEchocardiographic and hemodynamic data were measured in nine closed chest dogs during graded cardiac tamponade (pericardial pressure 5, 10, 15 mm Hg) before and after production of diffuse acute ischemic right ventricular dysfunction. Right ventricular dysfunction was produced by intracoronary injection of nonradioactive microspheres (mean diameter ± SD 54 ± 4 μm) and caused a significant increase in right atrial pressure (7.6 ± 1.4 vs. 1.6 ± 1 mm Hg, p < 0.001) and cross-sectional areas of both the right atrium (8.3 ± 0.3 vs. 5.6 ± 0.2 cm2, p < 0.001) and right ventricle (8.8 ± 0.4 vs. 5.7 ± 0.4 cm2, p < 0.001).Right atrial and ventricular collapse required a significantly larger pericardial effusion and pericardial pressure after light ventricular infarction than before. Mean aortic pressure had fallen 1.9 ± 2% and 6.5 ± 6.9% at the time of right atrial collapse (p = NS before vs. after right ventricular dysfunction) and 3 ± 4.1% and 20.1 ± 20.8% at the time of right ventricular collapse (p < 0.03) before and after right ventricular dysfunction, respectively.In the presence of ischemic right ventricular dysfunction, echocardiographic signs of cardiac tamponade are less sensitive and occur later in the hemodynamic progression of cardiac tamponade. Pulsus paradoxus with cardiac tamponade was not prevented by coexisting ischemic right ventricular dysfunction