Rapid and Efficient Production of Coronary Artery Ligation and Myocardial Infarction in Mice Using Surgical Clips.
ABSTRACT: The coronary artery ligation model in rodents mimics human myocardial infarction (MI). Normally mechanical ventilation and prolonged anesthesia period are needed. Recently, a method has been developed to create MI by popping-out the heart (without ventilation) followed by immediate suture ligation. Mortality is high due to the time-consuming suture ligation process while the heart is exposed. We sought to improve this method and reduce mortality by rapid coronary ligation using a surgical clip instead of a suture.Mice were randomized into 3 groups: clip MI (CMI), suture MI (SMI), or sham (SHAM). In all groups, heart was manually exposed without intubation through a small incision on the chest wall. Unlike the conventional SMI method, mice in the CMI group received a metal clip on left anterior descending artery (LAD), quickly dispensed by an AutoSuture Surgiclip™. The CMI method took only 1/3 of ligation time of the standard SMI method and improved post-MI survival rate. TTC staining and Masson's trichrome staining revealed a similar degree of infarct size in the SMI and CMI groups. Echocardiograph confirmed that both SMI and CMI groups had a similar reduction of ejection fraction and fraction shortening over the time. Histological analysis showed that the numbers of CD68+ macrophages and apoptotic cells (TUNEL-positive) are indistinguishable between the two groups.This new method, taking only less than 3 minutes to complete, represents an efficient myocardial infarction model in rodents.
Project description:BACKGROUND:Although silent myocardial infarction (SMI) accounts for about one-half of the total number of myocardial infarctions (MIs), the risk of heart failure (HF) among patients with SMI is not well established. OBJECTIVES:The purpose of this study was to examine the association of SMI and clinically manifested myocardial infarction (CMI) with HF, as compared with patients with no MI. METHODS:This analysis included 9,243 participants from the ARIC (Atherosclerosis Risk In Communities) study who were free of cardiovascular disease at baseline (ARIC visit 1: 1987 to 1989). SMI was defined as electrocardiographic evidence of MI without CMI after the baseline until ARIC visit 4 (1996 to 1998). HF events were ascertained starting from ARIC visit 4 until 2010 in individuals free of HF before that visit. RESULTS:Between ARIC visits 1 and 4, 305 SMIs and 331 CMIs occurred. After ARIC visit 4 and during a median follow-up of 13.0 years, 976 HF events occurred. The incidence rate of HF was higher in both CMI and SMI participants than in those without MI (incidence rates per 1,000 person-years were 30.4, 16.2, and 7.8, respectively; p < 0.001). In a model adjusted for demographics and HF risk factors, both SMI (hazard ratio [HR]: 1.35; 95% confidence interval [CI]: 1.02 to 1.78) and CMI (HR: 2.85; 95% CI: 2.31 to 3.51) were associated with increased risk of HF compared with no MI. These associations were consistent in subgroups of participants stratified by several HF risk predictors. However, the risk of HF associated with SMI was stronger in those younger than the median age (53 years) (HR: 1.66; 95% CI: 1.00 to 2.75 vs. HR: 1.19; 95% CI: 0.85 to 1.66, respectively; overall interaction p by MI type <0.001). CONCLUSIONS:SMI is associated with an increased risk of HF. Future research is needed to examine the cost effectiveness of screening for SMI as part of HF risk assessment, and to identify preventive therapies to improve the risk of HF among patients with SMI.
Project description:Recently, targeting cyclic-GMP specific phosphodiesterase-5 (PDE5) has attracted much interest in several cardiopulmonary diseases, in particular myocardial ischemia (MI). Although multiple mechanisms were postulated for these beneficial effects at cellular level, early transcriptional changes were unknown. The aim of present study was to examine gene expression profiles in response to MI after 24 h of ischemia in murine model and compare transcriptional modulation by sildenafil, a popular phosphodiesterase 5 (PDE5) inhibitor. Mice were divided into four groups: Control sham (C), Sildenafil sham (S), Control MI (CMI) and Sildenafil MI (SMI). Sildenafil was given at a dose of 0.7 mg/kg intraperitoneally 30 min before LAD occlusion. cDNA microarray analysis of peri-infarct tissue was done using a custom cloneset and employing a looped dye swap design. Replicate signals were median averaged and normalized using LOWESS algorithm. R/MAANOVA analysis was used and false discovery rate corrected permutation p-values <0.005 were employed as significance thresholds. 156 genes were identified as significantly regulated demonstrating fold difference >1.5 in at least one of the four groups. 52 genes were significantly upregulated in SMI compared to CMI. For a randomly chosen subset of genes (9), microarray data were confirmed through real time RT-PCR. The differentially expressed genes could be classified into following groups based on their function: phosphorylation/dephosphorylation, apoptosis, differentiation, ATP binding. Our results suggest that sildenafil treatment might regulate early genetic reprogramming strategy for preservation of the ischemic myocardium.
Project description:Acute myocardial infarction (MI) is a leading cause of morbidity and mortality in the world. Traditional method to induce MI by left coronary artery (LCA) ligation is typically performed by an invasive approach that requires ventilation and thoracotomy, causing serious injuries in animals undergoing this surgery. We attempted to develop a minimally invasive method (MIM) to induce MI in mice. Under the guide of ultrasound, LCA ligation was performed in mice without ventilation and chest-opening. Compared to sham mice, MIM induced MI in mice as determined by triphenyltetrazolium chloride staining and Masson staining. Mice with MIM surgery revealed the reductions of LVEF, LVFS, E/A and ascending aorta (AAO) blood flow, and the elevations of S-T segment and serum cTn-I levels at 24 post-operative hours. The effects of MI induced by MIM were comparable to the effects of MI produced by traditional method in mice. Importantly, MIM increased the survival rates and caused less inflammation after the surgery of LCA ligation, compared to the surgery of traditional method. Further, MIM induced angiogenesis and apoptosis in ischaemic hearts from mice at postoperative 28 days as similarly as traditional method did. Finally, the MIM model was able to develop into the myocardial ischaemia/reperfusion model by using a balloon catheter with minor modifications. The MI model is able to be efficiently induced by a minimally invasive approach in mice without ventilation and chest-opening. This new model is potentially to be used in studying ischaemia-related heart diseases.
Project description:coronary artery ligation to induce myocardial infarction (MI) in mice is typically performed by an invasive and time-consuming approach that requires ventilation and chest opening (classic method), often resulting in extensive tissue damage and high mortality. We developed a novel and rapid surgical method to induce MI that does not require ventilation.the purpose of this study was to develop and comprehensively describe this method and directly compare it to the classic method.male C57/B6 mice were grouped into 4 groups: new method MI (MI-N) or sham (S-N) and classic method MI (MI-C) or sham (S-C). In the new method, heart was manually exposed without intubation through a small incision and MI was induced. In the classic method, MI was induced through a ventilated thoracotomy. Similar groups were used in an ischemia/reperfusion injury model. This novel MI procedure is rapid, with an average procedure time of 1.22 ± 0.05 minutes, whereas the classic method requires 23.2 ± 0.6 minutes per procedure. Surgical mortality was 3% in MI-N and 15.9% in MI-C. The rate of arrhythmia was significantly lower in MI-N. The postsurgical levels of tumor necrosis factor-? and myeloperoxidase were lower in new method, indicating less inflammation. Overall, 28-day post-MI survival rate was 68% with MI-N and 48% with MI-C. Importantly, there was no difference in infarct size or post-MI cardiac function between the methods.this new rapid method of MI in mice represents a more efficient and less damaging model of myocardial ischemic injury compared with the classic method.
Project description:Silent myocardial infarction (SMI) accounts for about half of the total number of MIs, and is associated with poor prognosis as is clinically documented MI (CMI). The electrocardiographic (ECG) spatial QRS/T angle has been a strong predictor of cardiovascular outcomes. Whether spatial QRS/T angle also is predictive of SMI, and the easy-to-obtain frontal QRS/T angle will show similar association are currently unknown.We examined the association between the spatial and frontal QRS/T angles, separately, with incident SMI among 9498 participants (mean age 54years, 57% women, and 20% African-American), who were free of cardiovascular disease at baseline (visit 1, 1987-1989) from the Atherosclerosis Risk in Communities (ARIC) study. Incident SMI was defined as MI occurring after the baseline until visit 4 (1996-1998) without CMI. The frontal plane QRS/T angle was defined as the absolute difference between QRS axis and T axis. Values greater than the sex-specific 95th percentiles of the QRS/T angles were considered wide (abnormal).A total of 317 (3.3%) incident SMIs occurred during a 9-year median follow-up. In a model adjusted for demographics, cardiovascular risk factors and potential confounders, both abnormal frontal (HR 2.28, 95% CI 1.58-3.29) and spatial (HR 2.10, 95% CI 1.44-3.06) QRS/T angles were associated with an over 2-fold increased risk of incident SMI. Similar patterns of associations were observed when the results were stratified by sex.Both frontal and spatial QRS/T angles are predicative of SMI suggesting a potential use for these markers in identifying individuals at risk.
Project description:Late-gadolinium-enhanced (LGE) cardiac MRI (CMR) is a powerful method for characterizing myocardial infarction (MI), but the requisite gadolinium infusion is estimated to be contraindicated in ?20% of patients with MI because of end-stage chronic kidney disease. The purpose of this study is to investigate whether T1 CMR obtained without contrast agents at 3 T could be an alternative to LGE CMR for characterizing chronic MIs using a canine model of MI.Canines (n=29) underwent CMR at 7 days (acute MI [AMI]) and 4 months (chronic MI [CMI]) after MI. Infarct location, size, and transmurality measured by using native T1 maps and LGE images at 1.5 T and 3 T were compared. Resolution of edema between AMI and CMI was examined with T2 maps. T1 maps overestimated infarct size and transmurality relative to LGE images in AMI (P=0.016 and P=0.007, respectively), which was not observed in CMI (P=0.49 and P=0.81, respectively) at 3 T. T1 maps underestimated infarct size and transmurality relative to LGE images in AMI and CMI (P<0.001) at 1.5 T. Relative to the remote territories, T1 of the infarcted myocardium was increased in CMI and AMI (P<0.05), and T2 of the infarcted myocardium was increased in AMI (P<0.001) but not in CMI (P>0.20) at both field strengths. Histology showed extensive replacement fibrosis within the CMI territories. CMI detection sensitivity and specificity of T1 CMR at 3 T were 95% and 97%, respectively.Native T1 maps at 3 T can determine the location, size, and transmurality of CMI with high diagnostic accuracy. Patient studies are necessary for clinical translation.
Project description:Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have recently been shown to express key cardiac proteins and improve in vivo cardiac function when administered following myocardial infarction. However, the efficacy of hiPSC-derived cell therapies, in direct comparison to current, well-established stem cell-based therapies, is yet to be elucidated. The goal of the current study was to compare the therapeutic efficacy of human mesenchymal stem cells (hMSCs) with hiPSC-CMs in mitigating myocardial infarction (MI).Male athymic nude hyrats were subjected to permanent ligation of the left-anterior-descending (LAD) coronary artery to induce acute MI. Four experimental groups were studied: 1) control (non-MI), 2) MI, 3) hMSCs (MI+MSC), and 4) hiPSC-CMs (MI+hiPSC-derived cardiomyocytes). The hiPSC-CMs and hMSCs were labeled with superparamagnetic iron oxide (SPIO) in vitro to track the transplanted cells in the ischemic heart by high-field cardiac MRI. These cells were injected into the ischemic heart 30-min after LAD ligation. Four-weeks after MI, cardiac MRI was performed to track the transplanted cells in the infarct heart. Additionally, echocardiography (M-mode) was performed to evaluate the cardiac function. Immunohistological and western blot studies were performed to assess the cell tracking, engraftment and cardiac fibrosis in the infarct heart tissues.Echocardiography data showed a significantly improved cardiac function in the hiPSC-CMs and hMSCs groups, when compared to MI. Immunohistological studies showed expression of connexin-43, ?-actinin and myosin heavy chain in engrafted hiPSC-CMs. Cardiac fibrosis was significantly decreased in hiPSC-CMs group when compared to hMSCs or MI groups. Overall, this study demonstrated improved cardiac function with decreased fibrosis with both hiPSC-CMs and hMSCs groups when compared with MI group.
Project description:Pulmonary hypertension due to left heart disease is associated with poor outcomes. This study investigated the beneficial effects of isosorbide dinitrate (ISDN) inhalation on pulmonary pressure and ventricular remodeling in a rat model of heart failure (HF) following myocardial infarction (MI). To assess the effect of ISDN on pulmonary pressure, 20 male Sprague-Dawley (SD) rats were randomized to four groups: Normal saline (NS) 1 ml/kg, ISDN 1 mg/kg, NS 3 ml/kg or ISDN 3 mg/kg following coronary ligation. Assessments included pulmonary and systemic artery pressure alterations, lung weight/body weight and plasma nitric oxide (NO) concentration. To assess the effect of ISDN on ventricular remodeling, 30 SD rats were randomized to three groups: Sham surgery, MI-NS (intratracheal NS 3 ml/kg for 13 days following coronary ligation), and MI-ISDN (intratracheal ISDN 3 mg/kg for 13 days following coronary ligation). On day 15, all rats underwent echocardiogram and hemodynamic assessments. The area affected by MI was evaluated using microscopy and vascular endothelial growth factor (VEGF) expression was examined using immunohistochemistry. Plasma epinephrine, norepinephrine and brain natriuretic peptide (BNP) levels were assessed by ELISA. Intratracheal ISDN reduced pulmonary and systematic artery pressure without pulmonary edema when compared with NS. The reduction was associated with increased plasma NO levels. ISDN inhalation for 14 days reduced MI size and alleviated left and right ventricular remodeling following MI. These hemodynamic and morphological improvements were associated with decreased plasma epinephrine, norepinephrine and BNP levels, and an increased VEGF positive area at the border of MI region. In conclusion, intratracheal administration of ISDN was effective in improving ventricular remodeling and cardiac function in a rat model of HF following MI.
Project description:Purpose:To evaluate the potential value of microscope-integrated optical coherence tomography (MI-OCT) in anterior segment surgical maneuvers. Methods:Twenty-four ophthalmology residents, who were randomly and evenly divided into two groups, performed four anterior segment surgical maneuvers (corneal tunnel, scleral tunnel, simple corneal suture, and corneal laceration repair) on porcine eyes with (group B) or without (group A) real-time MI-OCT feedback. All residents performed the maneuvers again without MI-OCT. Results:Compared with group A, group B (with MI-OCT) showed better accuracy in the length/depth of the corneal tunnel and the length of the scleral tunnel. However, both groups showed similar performances in the depth of both the simple corneal suture and the corneal laceration suture. When both groups performed the maneuvers again without MI-OCT, group B still showed better results than group A for the length of both the corneal and scleral tunnels. Conclusions:Primary results suggest that real-time MI-OCT images are valuable for some anterior segment surgical maneuvers and could be helpful in surgical training. Translational Relevance:MI-OCT systems can be valuable in improving accuracy and decision making during anterior segment surgery and will be useful in surgical training.
Project description:Interferon regulatory factor 3 (IRF3) and type I interferons (IFNs) protect against infections1 and cancer2, but excessive IRF3 activation and type I IFN production cause autoinflammatory conditions such as Aicardi?Goutières syndrome3,4 and STING-associated vasculopathy of infancy (SAVI)3. Myocardial infarction (MI) elicits inflammation5, but the dominant molecular drivers of MI-associated inflammation remain unclear. Here we show that ischemic cell death and uptake of cell debris by macrophages in the heart fuel a fatal response to MI by activating IRF3 and type I IFN production. In mice, single-cell RNA-seq analysis of 4,215 leukocytes isolated from infarcted and non-infarcted hearts showed that MI provokes activation of an IRF3?interferon axis in a distinct population of interferon-inducible cells (IFNICs) that were classified as cardiac macrophages. Mice genetically deficient in cyclic GMP-AMP synthase (cGAS), its adaptor STING, IRF3, or the type I IFN receptor IFNAR exhibited impaired interferon-stimulated gene (ISG) expression and, in the case of mice deficient in IRF3 or IFNAR, improved survival after MI as compared to controls. Interruption of IRF3-dependent signaling resulted in decreased cardiac expression of inflammatory cytokines and chemokines and decreased inflammatory cell infiltration of the heart, as well as in attenuated ventricular dilation and improved cardiac function. Similarly, treatment of mice with an IFNAR-neutralizing antibody after MI ablated the interferon response and improved left ventricular dysfunction and survival. These results identify IRF3 and the type I IFN response as a potential therapeutic target for post-MI cardioprotection. Overall design: We report the application of inDrop single cell RNA-Seq profiling to the analysis of the infarcted mouse heart 4 days after permanent coronary ligation in wild type (Sample 1) and IRf3-/- mice (Sample 2) as well as comparable section of wild type mouse heart with no myocardial infarction (Sample 3) Wild type mice and IRF3-/- mice underwent left anterior descending coronary artery occlusion by permanent suture ligation. After 4 days, hearts were flushed with cold saline, and infarct tissue was collected, stained with DAPI, flow sorted to isolate single cells, and subjected to inDrop barcoding per published protocol (Zilionis et al, Nature Protocols 2016, doi:10.1038/nprot.2016.154)