Guangwei Zhang

Phenotypic switching of vascular smooth muscle cells in animal model of rat thoracic aortic aneurysm

OBJECTIVES To explore if there is phenotypic switching in the vascular smooth muscle cells (vSMCs) of rat thoracic aortic aneurysms and the role it plays in the process of aneurysm formation. METHODS Male SD white rats were assigned randomly to the aneurysm group (AG) and control group (CG). The animal aneurysm model was obtained by soaking the peri-adventitia with porcine pancreatic elastase (PPE). The rats in the CG were given saline to provide contrast. A vascular ultrasound was used to monitor the diameter of the aneurysm. Specimens were stained with haematoxylin and eosin (HE), and α-SMA, SM-MHC, matrix metalloproteinase (MMP)-2 and MMP-9 were detected with immunohistochemistry staining. α-SMA, SM-MHC, MMP-2 and MMP-9 were conducted with western blot. vSMCs taken from the descending aorta of both of the CG and AG were separated and cultured until Passage 3. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method were used to analyse cell proliferation. Western blot was used to evaluate MMP-2, MMP-9 expression and flow cytometry was employed to assess cell apoptosis. RESULTS Vascular ultrasound showed obvious dilatation of soaked descending aorta. HE staining showed thickening of thoracic aorta and disarrangement of cells after soaking with PPE. Immunohistochemistry staining showed high expression of MMP-2 and MMP-9 but low expression of SM-MHC and α-SMA in the AG. Tissue western blot analysis of the AG showed that the protein gray value was high in MMP-2 and MMP-9, but low in α-SMA and SM-MHC, which had statistical differences compared with CG with a P-value of <0.05. MTT analysis showed vSMC proliferation activity was higher in the AG than in the CG. Flow cytometry analysis revealed that cell apoptosis between the control and aneurysm groups had significant statistical differences. CONCLUSIONS There is vSMC phenotypic switching in animal models as seen through the rat thoracic aortic aneurysms. This may play an important role in the formation of aneurysms. Our findings are relevant to human aneurysms and may be conducive in the research of aortic aneurysm pathology and treatment.

HGF and IGF-1 promote protective effects of allogeneic BMSC transplantation in rabbit model of acute myocardial infarction.

To explore effects of hepatocyte growth factor (HGF) combined with insulin‐like growth factor 1 (IGF‐1) on transplanted bone marrow mesenchymal stem cells (BMSCs), for treatment of acute myocardial ischaemia.

Transmyocardial drilling revascularization combined with heparinized bFGF-incorporating stent activates resident cardiac stem cells via SDF-1/CXCR4 axis ☆

OBJECTIVE To investigate whether transmyocardial drilling revascularization combined with heparinized basic fibroblast growth factor (bFGF)-incorporating degradable stent implantation (TMDRSI) can promote myocardial regeneration after acute myocardial infarction (AMI). METHODS A model of AMI was generated by ligating the mid-third of left anterior descending artery (LAD) of miniswine. After 6 h, the animals were divided into none-treatment (control) group (n=6) and TMDRSI group (n=6). For TMDRSI group, two channels with 3.5 mm in diameter were established by a self-made drill in the AMI region, into which a stent was implanted. Expression of stromal cell-derived factor-1(α) (SDF-1(α)) and CXC chemokine receptor 4 (CXCR4), cardiac stem cell (CSC)-mediated myocardial regeneration, myocardial apoptosis, myocardial viability, and cardiac function were assessed at various time-points. RESULTS Six weeks after the operation, CSCs were found to have differentiated into cardiomyocytes to repair the infarcted myocardium, and all above indices showed much improvement in the TMDRSI group compared with the control group (P<0.001). CONCLUSIONS The new method has shown to be capable of promoting CSCs proliferation and differentiation into cardiomyocytes through activating the SDF-1/CXCR4 axis, while inhibiting myocardial apoptosis, thereby enhancing myocardial regeneration following AMI and improving cardiac function. This may provide a new strategy for myocardial regeneration following AMI.

bFGF binding cardiac extracellular matrix promotes the repair potential of bone marrow mesenchymal stem cells in a rabbit model for acute myocardial infarction

To assess the effect of basic fibroblast growth factor-binding extracellular matrix (bFGF-ECM) combined with bone marrow mesenchymal stem cells (BMSCs) transplantation on acute myocardial infarction (AMI) and explore the underlying mechenisms. Rabbit hearts were processed by decellularization with sodium dodecyl sulfate (SDS) perfusion, heparin immobilization, bFGF-binding and homogenization, for preparation of bFGF-binding cardiac ECM suspension (bFGF-ECM). Thereafter, the characteristics of bFGF release were analyzed in vitro. Following ligation of the mid-third of the left anterior descending artery, the rabbits were divided into a control group (no treatment), BMSCs group (BMSCs transplantation), bFGF-ECM group (bFGF-ECM implantation), and BMSCs + bFGF-ECM group (BMSCs and bFGF-ECM implantation). Apoptosis and differentiation of implanted BMSCs, and the left ventricular (LV) remodeling and function were assessed. The ex vivo proliferation, apoptosis, migration and differentiation of BMSCs were determined after exposure to bFGF and/or ECM. The ECM could sustainably release bFGF. 24 h and 6 weeks after the operation, improved viability and differentiation of the implanted BMSCs, as well as inhibited dilatation and preserved function of the left ventricle (LV), were significant in the BMSCs  +  bFGF-ECM group compared with other groups (P < 0.05), although BMSCs and ECM-bFGF groups also showed better results than control group (P < 0.05). Additionally, ECM and bFGF showed a synergistic effect on BMSCs proliferation, viability, migration and differentiation. The combination of bFGF-binding ECM and BMSCs implantation may promote myocardial regeneration and LV function, and become a new strategy for the treatment of AMI.

Protection of the rat brain from hypothermic circulatory arrest injury by a chipmunk protein

Objectives The study objectives were to test the hypothesis that special protein exists in hibernating chipmunk albumin and whether this protein has a neuroprotective effect in Sprague–Dawley rats during deep hypothermia circulatory arrest. Methods Forty chipmunks were allocated into a hibernation group and an active group (20 chipmunks in each group). Special protein was detected and isolated from hibernating chipmunk albumin. Forty Sprague–Dawley rats were randomly divided into a sham group, deep hypothermia circulatory arrest group, special protein group, and naloxone group (10 rats in each group). Special protein that was detected and collected from hibernating chipmunks were injected in rats in the special protein group for 3 consecutive days before operation, and naloxone was given at the same time in the naloxone group. Rats were subjected to cardiopulmonary bypass and 60‐minute deep hypothermia circulatory arrest. Tumor necrosis factor‐&agr; and interleukin‐6 levels were detected. Animals received neurologic testing. Relative protein expression, malondialdehyde, and superoxide dismutase of hippocampus were detected. The brain was fixed for histopathologic assessment. Results The rats that received special protein displayed ischemic tolerance after deep hypothermia circulatory arrest. The neuroprotective effect could be reversed by naloxone. The inflammation response was attenuated in the special protein group (P < .008, compared with the deep hypothermia circulatory arrest and naloxone groups). The mature brain‐derived neurotrophic factor and SIRT1 levels were higher in the special protein group (P < .01, compared with the deep hypothermia circulatory arrest and naloxone groups). Histopathologic assessment showed that the injury in the special protein group was attenuated (pathological score, P < .05; surviving hippocampal CA1 neurons, P < .01; TUNEL‐positive neurons, P < .01; compared with deep hypothermia circulatory arrest and naloxone groups). Intravenous injection of special protein significantly improved neurologic recovery. Conclusions We found that a specific protein existed in hibernating chipmunk albumin and could play an important neuroprotective role in rats.

Neuregulin 1 Attenuates Neuronal Apoptosis Induced by Deep Hypothermic Circulatory Arrest Through ErbB4 Signaling in Rats.

Abstract: Mounting evidence suggests that neurological injury occurs after deep hypothermic circulatory arrest (DHCA), a protocol widely used in surgery for congenital heart diseases and aortic repair. Neuregulin 1 (NRG1), a neurotrophic factor highly expressed in the central nervous system, is crucial for neuronal survival. However, whether NRG1 is protective against apoptosis induced by DHCA is still unclear, as are the putative mechanisms involved. In this study, exogenous human NRG1 pretreatment (2.5 and 3.75 ng/kg, intracarotid injection) significantly inhibited neuronal apoptosis in DHCA-treated male rats, and notably, endogenous NRG1 expression was also increased. Bcl-2, as well as phosphorylated phosphatidylinositol-3-kinase, Akt, and cAMP-response element binding protein, were all increased, resulting in phosphorylation and subsequent activation of the ErbB4 receptor. Finally, expression of the apoptosis-related protein cleaved-caspase-3 was decreased, resulting in the inhibition of neuronal apoptosis induced by DHCA. Thus, our data indicate that NRG1 treatment inhibited DHCA-induced neuronal apoptosis by activating ErbB4 signaling, providing a potential therapeutic pathway for the prevention of neurological injury induced by DHCA.

Losartan affects the substrate for atrial fibrillation maintenance in a rabbit model

BACKGROUND Atrial fibrosis causes abnormal conduction through the atria, creating a substrate for atrial fibrillation (AF). In a rabbit model, rapid atrial pacing produces significant atrial fibrosis and the substrate for AF maintenance. This atrial remodeling is a potential therapeutic target. OBJECTIVE To evaluate the effects of the losartan on atrial fibrosis. METHODS Thirty rabbit AF models were produced by rapid atrial stimulation. They were randomly divided into three groups: sham group, rapid atrial pacing group, and rapid atrial pacing with losartan group. We performed AF vulnerability studies, atrial histologic, and molecular analyses after 4 weeks. RESULTS Only rabbits in the rapid atrial pacing group developed sustained AF (30 min, 4of 10 rabbits). Treatment with losartan resulted in a significant reduction in left atrial fibrosis and AF duration (P<.01). real-time polymerase chain reaction analyses demonstrated the drugs effects on the expression of Collagen I, Collagen III, and TGF-β/Smads signaling pathway. CONCLUSIONS The treatment of losartan results in significantly reduced atrial fibrosis and AF vulnerability. Pharmacological therapy targeted at the fibrotic substrate itself may play an important role in the management of AF.

A novel augmented venous-drainage model of cardiopulmonary bypass for deep hypothermic circulatory arrest without blood priming

Objective: Cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) are commonly used in cardiac surgery. However, the mortality and morbidity are still high in practice. Developing novel protective stategies and elucidating the underlying mechanisms for the pathophysiological consequences of DHCA have been hampered because of the absence of a satisfactory recovery animal model. The aim of this study was to establish a novel and safe DHCA model without blood priming in rats to study the pathophysiology of potential complications. Methods: Ten adult male Sprague-Dawley rats (age, 14-16 weeks; weight, 200-300g) were used. The entire CPB circuit consisted of a modified reservoir, a custom-designed small-volume membrane oxygenator, a roller pump and a home-made heat exchanger, all of which were connected via silicon tubing. The volume of the priming solution was less than 10 ml. The right jugular vein, right carotid artery and left femoral artery were cannulated. The blood was drained from the right atrium through the right jugular vein and fed back to the rat via the left femoral artery. CPB was commenced at a full flow rate. The animals were cooled to a pericranial temperature of 18°C and then subjected to 45 minutes of DHCA with global ischemia. Circulatory arrest was followed by rewarming and over 60 minutes of reperfusion. CPB was terminated carefully. Blood in the circuit was centrifuged and slowly transfused to achieve optimal hematocrit. Blood gas and hemodynamic parameters were recorded at each time point before CPB, during CPB and after CPB. Results: All CPB and DHCA processes were achieved successfully. No rat died in our research. Blood gas analyses at different times were normal. Cardiac function and blood pressure were stable after the operation. The vital signs of all the rats were stable. Conclusion: The novel augmented venous-drainage CPB and DHCA model in rats could be established successfully without blood priming.

Antegrade Versus Continuous Retrograde del Nido Cardioplegia in the David I Operation

BACKGROUND The efficacy of continuous retrograde del Nido cardioplegia for myocardial protection is still controversial. We hypothesised that antegrade and retrograde cardioplegia offer equivalent safety for myocardial protection in the David I procedure. METHODS We retrospectively reviewed 33 patients undergoing the David I operation with antegrade or retrograde del Nido solution from June 2014 to January 2016. The outcomes were compared. The follow-up was 1 month to 15 months. RESULTS There was no hospital mortality or reoperation in both groups. Cardiopulmonary bypass, and aortic clamp times were similar. Troponin I level (TnI), creatine kinase level (CKMB), left ventricular ejection fraction (LVEF), ventilation times, intensive care unit (ICULOS) and hospital stay times (THLOS) were similar between the two groups. The lactate level was slightly higher (9.26±2.56 vs 7.17±1.58, p=0.01) in the antegrade group compared with the retrograde group. The incidence of heart block was higher (four patients) in the retrograde group (26.7% vs 0%, p=0.019). Only one patient (6.7%) required implantation of a permanent cardiac pacemaker. CONCLUSION Antegrade and continuous retrograde del Nido cardioplegia can be used safely and effectively in the David I operation. The continuous retrograde del Nido cardioplegia is associated with a higher rate of temporary AV block which does not require permanent pacing, and a lower lactate level.

Endothelial factors after selective retrograde coronary venous bypass under different pressures.

Abstract Background. Selective retrograde coronary venous bypass (SRCVB) may be a promising treatment for patients with advanced coronary artery disease (CAD). The aim of this study is to investigate the effect of SRCVB on plasma endothelial factor levels in dog myocardial ischemic model, and explore the possible mechanisms. Methods. 24 crossbreed dogs were randomly divided into three groups: (1) control group; (2) SRCVB group with 60 mmHg perfusion pressure; (3) SRCVB group with 90 mmHg perfusion pressure. The posterior descending coronary artery (PDA) was ligated in all groups, and SRCVB was performed in the last two groups. The levels of plasma nitric oxide (NO) and endothelin (ET) at different time points were determined in each group. In SRCVB groups, ink and imaging agent were injected to the heart through SVG graft for assessment of vein perfusion. Results. At the acute period, there were significant increase in the plasma levels of NO and decrease in ET in SRCVB 90 mmHg group compared with the control (P < 0. 01), and a further improvement were found in SRCVB 60 mmHg group (P < 0. 01). The ink or imaging agent was found in the myocardial tissue and flowed back to right atrium through contralateral coronary vein. Conclusions. SRCVB with low level of perfusion pressure could provide effective perfusion for ischemic myocardium and alleviate the myocardial endothelial cell injury. It may be a new therapeutic strategy for severe CAD.