AMPKα2 deficiency exacerbates hypoxia-induced pulmonary hypertension by promoting pulmonary arterial smooth muscle cell proliferation.

Increased evidence indicates that adenosine monophosphate-activated protein kinase (AMPK) plays a vital role in vascular homeostasis, especially under hypoxia, and protects against the progression of pulmonary hypertension (PH). However, the role of AMPK in the pathogenesis of PH remains to be clarified. In the present study, we confirmed that a loss of AMPKα2 exacerbated the development of PH by using hypoxia-induced PH model in AMPKα2 -/- mice. After a 4-week period of hypoxic exposure, AMPKα2 -/- mice exhibited more severe pulmonary vascular remodeling and pulmonary vascular smooth muscle cell (SMC) proliferation when compared with wild type (WT) mice. In vitro, AMPKα2 knockdown promoted the proliferation of pulmonary arterial smooth muscle cells (PASMCs) under hypoxia. This phenomenon was accompanied by upregulated Skp2 and downregulated p27kip1 expression and was abolished by rapamycin, an inhibitor of mTOR. These results indicate that AMPKα2 deficiency exacerbates hypoxia-induced PH by promoting PASMC proliferation via the mTOR/Skp2/p27kip1 signaling axis. Therefore, enhanced AMPKα2 activity might underlie a novel therapeutic strategy for the management of PH.

KLF15 is a protective regulatory factor of heart failure induced by pressure overload.

The aim of the present study was to investigate the protective effect of Kruppel­like factor 15 (KLF15) overexpression on heart failure (HF) induced by left ventricular (LV) pressure overload in mice. Wild­type (WT) mice and cardiac­specific KLF15­overexpressed transgenic (TG) mice were selected as research subjects, and an LV pressure overload model was constructed by ascending aortic constriction surgery. Changes in cardiac morphology and function, and ultrastructure and molecular expression were observed via M­mode echocardiography, histological and immunohistochemical staining, ELISA and western blotting at 2 and 6 weeks of LV overload. WT and TG mice subjected to 2 weeks of overload displayed adaptive LV hypertrophy characterized by ventricular thickness, cardiomyocyte size, ejection fraction and fractional shortening of heart­lung weight ratio and KLF15, and increases in vascular endothelial growth factor (VEGF) expression without other pathological changes. WT mice subjected to 6 weeks of overload displayed enlargement of the LV chamber, severe interstitial remodeling, and HW/LW, cardiac capillary and heart function decline, accompanied by downregulated expression of KLF15 and VEGF, and upregulated expression of connective tissue growth factor, phosphorylated p38 (p­p38) and phosphorylated Smad3 (p­Smad3). In contrast, TG mice exhibited improved resistance to 6 weeks of overload and a slighter molecular expression response compared with WT mice. KLF15 was revealed to be a critical factor regulating the expression of CTGF, VEGF, p­p38 and p­Smad3, and could alleviate the progression from adaptive LV hypertrophy to decompensatory cardiac insufficiency.

Multinucleated polyploid cardiomyocytes undergo an enhanced adaptability to hypoxia via mitophagy.

AIMS: There is a large subpopulation of multinucleated polyploid cardiomyocytes (M*Pc CMs) in the adult mammalian heart. However, the pathophysiological significance of increased M*Pc CMs in heart disease is poorly understood. We sought to determine the pathophysiological significance of increased M*Pc CMs during hypoxia adaptation. METHODS AND RESULTS: A model of hypoxia-induced cardiomyocyte (CM) multinucleation and polyploidization was established and found to be associated with less apoptosis and less reactive oxygen species (ROS) production. Compared to mononucleated diploid CMs (1*2c CMs), tetraploid CMs (4c CMs) exhibited better mitochondria quality control via increased mitochondrial autophagy (mitophagy). RNA-seq revealed Prkaa2, the gene for AMPKα2, was the most obviously up-regulated autophagy-related gene. Knockdown of AMPKα2 increased apoptosis and ROS production and suppressed mitophagy in 4c CMs compared to 1*2c CMs. Rapamycin, an autophagy activator, alleviated the adverse effect of AMPKα2 knockdown. Furthermore, silencing PINK1 also increased apoptosis and ROS in 4c CMs and weakened the adaptive superiority of 4c CMs. Finally, AMPKα2-/- mutant mice exhibited exacerbation of apoptosis and ROS production via decreases in AMPKα2-mediated mitophagy in 4c CMs compared to 1*2c CMs during hypoxia. CONCLUSIONS: Compared to 1*2c CMs, hypoxia-induced 4c CMs exhibited enhanced mitochondria quality control and less apoptosis via AMPKα2-mediated mitophagy. These results suggest that multinucleation and polyploidization allow CM to better adapt to stress via enhanced mitophagy. In addition, activation of AMPKα2 may be a promising target for myocardial hypoxia-related diseases.

Re-enforcing hypoxia-induced polyploid cardiomyocytes enter cytokinesis through activation of ß-catenin.

Cardiomyocyte (CM) loss is a characteristic of various heart diseases, including ischaemic heart disease. Cardiac regeneration has been suggested as a promising strategy to address CM loss. Although many studies of regeneration have focused mainly on mononucleated or diploid CM, the limitations associated with the cytokinesis of polyploid and multinucleated CMs remain less well known. Here, we show that ß-catenin, a key regulator in heart development, can increase cytokinesis in polyploid multinucleated CMs. The activation of ß-catenin increases the expression of the cytokinesis-related factor epithelial cell transforming 2 (ECT2), which regulates the actomyosin ring and thus leads to the completion of cytokinesis in polyploid CMs. In addition, hypoxia can induce polyploid and multinucleated CMs by increasing factors related to the G1-S-anaphase of the cell cycle, but not those related to cytokinesis. Our study therefore reveals that the ß-catenin can promote the cytokinesis of polyploid multinucleated CMs via upregulation of ECT2. These findings suggest a potential field of polyploid CM research that may be exploitable for cardiac regeneration therapy.

Effects of Preoperative Risk Stratification on Direct In-hospital Costs for Chinese Patients with Coronary Artery Bypass Graft: A Single Center Analysis.

The purpose of this study was to analyze the components of inpatient costs for coronary artery bypass graft (CABG) according to preoperative risk stratification and to provide evidence for improvement of diagnosis-related groups (DRGs) payment. All patients (n=458) receiving an isolated CABG between January 2014 and December 2016 in a tertiary referral center, in southwest China, were analyzed. Hospital mortality was predicted by the EuroSCORE II for each patient. The patients were subdivided into two groups according to the observed mortality (1.97%, 9/458): a high-risk group (group H, predicted mortality ≥1.97%) and a low-risk group (group L, predicted mortality <1.97%). Clinical outcomes, resource use, in-hospital direct costs, and reimbursement expenses were compared between the two groups. Significant differences existed between group L and group H in postoperative mortality (0.4% vs. 3.4%; P=0.02), postoperative complications (10.6% vs. 45.7%; P<0.001), postoperative length of hospital stay (17.5±4.9 days vs. 18.8±6.5 days, P=0.01), in-hospital costs ($20 256±3096 vs. $23 334±6332; P<0.001), and reimbursement expenses ($7775±2627 vs. $9639±3917; P<0.001). In general, a higher EuroSCORE II was significantly associated with a worse clinical outcome and increased costs. The CABG cost data provide evidence for improvement of DRGs payment.

Cardiac resident macrophages are involved in hypoxia­induced postnatal cardiomyocyte proliferation.

Induction of cardiomyocyte proliferation, the most promising approach to reverse myocardial attrition, has been gaining importance as a therapy for cardiovascular disease. Hypoxia and macrophages were previously independently reported to promote cardiomyocyte proliferation in mice. However, whether hypoxia promotes cardiomyocyte proliferation in humans, and the association between hypoxia and macrophages in cardiomyocyte proliferation, have not to the best of our knowledge been previously investigated. The present study investigated the cardiomyocyte proliferation in 22 acyanotic and 29 cyanotic patients. Cardiomyocyte proliferation in a hypoxic mouse model (15% O2) was subsequently performed and the macrophage subsets were analyzed. A C­C chemokine receptor type 2 (CCR2) inhibitor was used to increase the number of resident macrophages in order to investigate the effect of macrophages on cardiomyocyte proliferation. The results demonstrated that cardiomyocyte proliferation in the cyanotic infant group was significantly increased compared with the acyanotic infant group and the hypoxia­treated C57BL/6J neonates confirmed the hypoxia­induced cardiomyocyte proliferation. However, hypoxia did not induce the proliferation of isolated cardiomyocytes. Notably, hypoxia treatment increased the number of cardiac resident macrophages in neonate hearts. Furthermore, increasing the number of resident macrophages significantly enhanced cardiomyocyte proliferation. In conclusion, postnatal hypoxia promoted cardiomyocyte proliferation in humans and animals, and cardiac resident macrophages may be involved in this process. Therefore, this novel mechanism may provide a promising strategy for cardiovascular disease treatment.

Risk Factors for Acute Kidney Injury after Cardiovascular Surgery: Evidence from 2,157 Cases and 49,777 Controls - A Meta-Analysis.

PURPOSE: Cardiovascular surgery-associated acute kidney injury (AKI-CS) contributes to mortality and morbidity. However, risk factors accelerating its development are unclear. We identified risk factors for AKI-CS in patients with cardiopulmonary bypass in the hospital surgical intensive care unit to predict and minimize renal complication in future cardiac surgery. METHODS: We analyzed data from 14 case-control studies published prior to June 2014 and indexed in Science Citation Index, PubMed, and other databases to determine the major risk factors for AKI-CS. RESULTS: Analyzed risk factors were divided into three groups: preoperative, intraoperative and postoperative. Preoperative factors included: age (OR, 4.87; 95% CI, 3.50-6.24), NYHA class III/IV (OR, 2.53; 95% CI, 1.32-4.86), hypertension (OR, 1.68; 95% CI, 1.44-1.97), preoperative creatinine (OR, 0.66; 95% CI, 0.18-1.14), peripheral vascular disease (OR, 1.31 95% CI, 1.09-1.57), respiratory system disease (OR, 1.29; 95% CI, 1.10-1.50), diabetes mellitus (OR, 1.52; 95% CI, 1.07-2.16), and cerebrovascular disease (OR, 2.13; 95% CI, 1.11-4.09). Intraoperative factors were: cardiopulmonary bypass time (OR, 33.78; 95% CI, 23.15-44.41), aortic clamping time (OR, 13.24; 95% CI, 7.78-18.69), use of intra-aortic balloon pump (OR, 4.44; 95% CI, 2.37-8.30), and type of surgery (OR, 1.01; 95% CI, 0.43-2.39). Postoperative factors were: infection (OR, 3.58; 95% CI, 1.43-8.97), redo operation (OR, 2.57; 95% CI, 1.75-3.78), emergency surgery (OR, 4.76; 95% CI, 3.05-7.43), and low cardiac output (OR, 2.30; 95% CI, 1.05-5.04). CONCLUSIONS: Our results support that preoperative, intraoperative, and postoperative factors are associated with AKI-CS. Ejection fraction, BMI, acute myocardial infarction, type of surgery, and congestive heart failure were not absolutely associated with AKI.

rs10263935 and rs6045676 identified by genome-wide association study were associated with aortic dissection in a Chinese population.

Aortic dissection (AD) is a disease characterized by a tear in the aortic intimal layer and separation of the arterial wall. Some risk factors, such as hypertension and Marfan syndrome, are well known in AD, but the role of genetic factor is largely unknown. In this study, we investigated the relation between two single nucleotide polymorphisms (SNPs) identified by genome-wide association study and AD. Approximately 177 patients diagnosed with AD through clinical evaluation and imaging techniques and 183 age- and sex-matched control subjects who were suffering from chest pain but without AD were included in the study. Genotyping of rs10263935 and rs6045676 was performed in both patients and control subjects using the TaqMan(®) method [Life Technologies (AB & Invitrogen), Carlsbad, CA]. The frequency of the AA and AG genotype in rs10263935 was significantly higher in the AD patients (0.085 and 0.435, respectively) than in the control subjects (0.033 and 0.355, respectively). The rs10263935 A allele frequency in the AD patients was higher than that in the control subjects [0.302 vs 0.210, odds ratio (OR) = 1.62, 95% confidence interval (CI): 1.26-2.28, P = 0.005]. Similarly, the frequency of the GG genotype in rs6045676 was significantly higher in the AD patients than in the control subjects (0.107 vs 0.038, P = 0.015). The rs6045676 G allele frequency in the AD patients was higher than that in the control subjects (0.282 vs 0.191, OR = 1.67, 95% CI: 1.18-2.50, P = 0.004). After adjustment of the confounding factors, such as smoking, sex, and age, the differences remain significant in several models (rs10263935: GG vs AA: OR = 3.13, 95% CI: 1.15-8.33, P = 0.025; GG vs AG: OR = 1.57, 95% CI: 1.01-2.44, P = 0.045; rs6045676: GG vs CC: OR = 3.30, 95% CI: 1.32-8.25, P = 0.011). rs10263935 on chromosome 7 and rs6045676 on chromosome 20 are associated with AD. Further studies are warranted to elucidate the functional role of these two variants.

Emergent endovascular vs. open surgery repair for ruptured abdominal aortic aneurysms: a meta-analysis.

OBJECTIVES: To systematically review studies comparing peri-operative mortality and length of hospital stay in patients with ruptured abdominal aortic aneurysms (rAAAs) who underwent endovascular aneurysm repair (EVAR) to patients who underwent open surgical repair (OSR). METHODS: The Medline, Cochrane, EMBASE, and Google Scholar databases were searched until Apr 30, 2013 using keywords such as abdominal aortic aneurysm, emergent, emergency, rupture, leaking, acute, endovascular, stent, graft, and endoscopic. The primary outcome was peri-operative mortality and the secondary outcome was length of hospital stay. RESULTS: A total of 18 studies (2 randomized controlled trials, 5 prospective studies, and 11 retrospective studies) with a total of 135,734 rAAA patients were included. rAAA patients who underwent EVAR had significantly lower peri-operative mortality compared to those who underwent OSR (overall OR = 0.62, 95% CI = 0.58 to 0.67, P<0.001). rAAA patients with EVAR also had a significantly shorter mean length of hospital stay compared to those with OSR (difference in mean length of stay ranged from -2.00 to -19.10 days, with the overall estimate being -5.25 days (95% CI = -9.23 to -1.26, P = 0.010). There was no publication bias and sensitivity analysis showed good reliability. CONCLUSIONS: EVAR confers significant benefits in terms of peri-operative mortality and length of hospital stay. There is a need for more randomized controlled trials to compare outcomes of EVAR and OSR for rAAA.

The application of on-pump beating-heart surgery for partial atrioventricular septal defect: a report of 87 cases.

BACKGROUND: Partial atrioventricular septal defect (P-AVSD) is a common congenital heart disease. Because of the presence of left and right atrioventricular valve deformities and the shift in the atrioventricular node and cardiac conduction bundle, the surgical repair of P-AVSD is difficult. This study was performed to compare the effects on the coronary sinus septum in the left versus the right atrium during surgical treatment for P-AVSD and report our experiences regarding the application of on-pump beating heart surgery under mild hypothermia for patients with P-AVSD. MATERIALS AND METHODS: The effects of on-pump beating heart surgery were analyzed retrospectively in 87 P-AVSD patients. Of the 87 total patients, 84 with anterior mitral leaflet cleft underwent valvuloplasty and 3 underwent mitral valve replacement. Seventy-seven patients underwent tricuspid valve annuloplasty, 2 underwent tricuspid valve replacement, and 1 underwent left superior vena cava ligation, and 3 patients with atrial fibrillation were treated with radiofrequency ablation. Patients with an ostium primum atrial septal defect underwent autologous pericardial modified Kirklin repair. Of these, 46 patients had their coronary sinus septum separated into the left atrium and 41 had their coronary sinus retained in the right atrium. Fingertip oxygen saturation was compared between patients in whom the coronary sinus was separated to the left atrium and those in whom the coronary sinus was retained in the right atrium. RESULTS: There was 1 postoperative early death (1.15%) due to respiratory failure, and 1 patient had a III degree atrioventricular block (1.15%) and underwent implantation of a permanent pacemaker. The fingertip oxygen saturation levels of the left atrium group were 96.81 ± 3.17 preoperatively, 95.37 ± 4.62 at 7 days postoperatively, and 94.53 ± 4.95 at 3 months postoperatively. Those of the right atrium group were 98.53 ± 2.84 preoperatively, 97.19 ± 3.57 at 7 days postoperatively, and 96.89 ± 4.19 at 3 months postoperatively. During the follow-up period, which ranged from 3 months to 7 years, the cardiac function was adequately restored. CONCLUSIONS: On-pump beating heart surgery under mild hypothermia is a safe and feasible method. The retention of the coronary sinus in the right atrium might maintain oxygen saturation.

Increased expression of connective tissue growth factor and transforming growth factor-beta-1 in atrial myocardium of patients with chronic atrial fibrillation.

OBJECTIVES: This study aimed to investigate the roles of connective tissue growth factor (CTGF) and transforming growth factor-ß1 (TGF-ß1) in atrial fibrosis in patients with chronic atrial fibrillation. METHODS: Up to 40 cases involving simple mitral valve replacement surgery were divided into 2 groups: the chronic atrial fibrillation (cAF) group (n = 28) and the sinus rhythm group (n = 12). Echocardiography was used to measure the cardiac cavity size and analyze the cardiac function. Right atrial specimens were obtained during the operation. The collagen volume fraction in the atrial specimens was examined. The mRNA and protein levels of TGF-ß1, Smad3 and CTGF were also investigated. RESULTS: Compared with the sinus rhythm group, the cAF group had higher collagen content in the right atrial tissues. The mRNA and protein levels of TGF-ß1, Smad3 and CTGF were also significantly elevated in the cAF group (p < 0.05). The mRNA and protein levels of TGF-ß1 and CTGF in the cAF group correlated positively with the collagen volume fraction. The positive correlation between the expression of TGF-ß1 and CTGF was also demonstrated. CONCLUSIONS: CTGF is upregulated via the TGF-ß1/Smad pathway in the atrial myocardium of cAF patients. Furthermore, the TGF-ß1/Smad pathway may play an important role in the structural remodeling during atrial fibrosis.

A rabbit model to study regression of ventricular hypertrophy.

BACKGROUND: The purpose of this study is to develop and characterise a reproducible rabbit model of LVH regression following pressure-induced myocardial hypertrophy. MATERIALS AND METHODS: Without endotracheal intubation and mechanical ventilation, a median sternotomy was performed. The median incision was made exactly along the midline of the sternum. Ascending aortic diameter was reduced 50% above the aortic valve, which lead to an approximate 75% reduction in crosssectional area. The sham-operated rabbits underwent the same procedures without actual ligation of the aorta. The animals of early DB group and late DB group were subjected to the second operation for removing the ligation eight weeks or 16 weeks after the initial banding surgery, respectively. Echocardiography, haemodynamic assessment, histology, and electron microscopy were used to assess functional and structural aspects of myocardial hypertrophy at each time point. RESULTS: The pressure overload resulted in robust LVH assessed by echocardiography, haemodynamic assessment, LV weight/body weight ratios, histology, and electron microscopy. Ascending aortic debanding completely or partially reversed LVH. The degree of LVH regression was association with the duration of pressure overload, proved by the fact that restoration of LV structure and function was complete in animals subjected to eight weeks of aortic banding but incomplete in animals subjected to 16 weeks of aortic banding. The animals did not experience severe mechanical ventilatory impairment. CONCLUSIONS: These results demonstrate an efficient and reproducible method of promoting LVH regression in rabbits without endotracheal intubation and mechanical ventilation.

Endovascular stent graft placement in the treatment of a ruptured tuberculous pseudoaneurysm of the descending thoracic aorta secondary to Pott's disease of the spine.

Ruptured thoracic aortic tuberculous pseudoaneurysms as a complication of mycobacterium tuberculosis infection of the spine are rare. Conventional treatment of a ruptured tuberculous pseudoaneurysm involves surgery with graft interposition or patch repair. We report successful repair of a ruptured tuberculous pseudoaneurysm of the descending thoracic aorta by endovascular stent graft placement and provide a literature review of such entities.

A 23-year-old male with Uhl's anomaly.

We report a case of a 23-year-old male with Uhl's anomaly who presented with nonparoxysmal atrioventricular junctional tachycardia with Mobitz I. The patient underwent successful total cavopulmonary conversion.

Toll-like receptor 4/nuclear factor-kappa B pathway is involved in myocardial injury in a rat chronic stress model.

Chronic stress is considered to predispose to various cardiovascular events such as coronary artery disease, hypertension, and even heart failure. In this study, rats were exposed to stress for 1 day, 1, 2, 3, and 4 weeks to establish a chronic stress model. A specific toll-like receptor 4 (TLR4) antagonist eritoran was used to block the activity of TLR4. On the second day after the last stress exposure, the animals were killed. The expression of TLR4 mRNA and nuclear factor-kappa B (NF-κB) DNA-binding activity in the myocardium were measured using reverse transcriptase polymerase chain reaction and electrophoretic mobility shift assay. The proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL-6) in myocardium were assayed by enzyme-linked immunosorbent assay. Myocardial injury was evident after chronic stress for 2 weeks. The TLR4 mRNA expression reached a peak after stress for 1 week. It was sustained at a stable level after stress exposure for 3 weeks and was restored to a nearly normal level in the fourth week. NF-κB DNA-binding activity was significantly enhanced after the stress for 1 day and markedly enhanced again after a 2-week stress exposure. It was weakened and reached a normal level after stress exposure for 4 weeks. The levels of TNF-α and IL-6 gradually increased and reached peaks after stress for 4 weeks. Meanwhile, eritoran significantly decreased the TLR4 mRNA expression and NF-κB activity in rats from the 2-week stress group. However, it did not downregulate the levels of TNF-α and IL-6. Importantly, it significantly improved the myocardial injury induced by the chronic stress. In conclusion, TLR4/NF-κB participates in myocardial injury during chronic stress.

Primary fibrosarcoma of the mitral valve.

A case of primary fibrosarcoma of the mitral valve is reported, which was resected and the valve was replaced. Adjuvant chemotherapy was admisinistered, and at one year the patient remains symptom free without evidence of recurrent disease.