Infarct Zone Research Articles

Electric Field-Based Dense Spatial Analysis of Unipolar Electrograms to Map Regional Activation-Repolarization Intervals

Objective: We wanted to develop a new method for processing dense spatially sampled unipolar electrograms, that yields physiological spatial distributions in activation-repolarization intervals.Background: Spatial heterogeneity in repolarization plays an important role in genesis and sustainment of cardiac arrhythmias. Reliable determination of repolarization times at high resolution on electrograms remains a difficult task. Methods: The new method describes the electrical activity on the heart's surface in terms of a physical electric field (E-field). Activation and repolarization times are calculated using an amplitude weighted average on QRS and T-waves. Activation-recovery intervals (ARI) obtained with this E-field method were validated against action potential durations (APD90) from monophasic action potential measurements. Relevance of the method was shown by calculating dense spatial distributions of beat-to-beat variability of repolarization (BVR) in myocardial infarction (MI).Results: E-field waveforms were more spatially homogeneous than the unipolar electrograms. The ARI strongly correlated with the APD90 (r2=0.94; p<0.001). Continuous activation and repolarization patterns were obtained, and the method removes non-physiological sharp spatial gradients obtained by currently adopted methods. Spatial BVR analysis revealed an increase in maximum BVR, spatial variance of BVR and spatial gradient of BVR in the border zone versus remote region of MI (all p<0.01). All BVR values were in pathophysiological range as described in other studies.Conclusion: The E-field method allows for a reliable determination of activation and repolarization times over the whole left ventricle. The new methodology confirmed that the border zone of myocardial infarction is a region with patches of increased variability of repolarization.

The short-chain fatty acid propionate improved ventricular electrical remodeling in a rat model with myocardial infarction.

The short-chain fatty acid (SCFA) propionate (C3), a microorganism metabolite produced by gut microbial fermentation, has parasympathetic-activation effects. The cardiac autonomic rebalancing strategy is considered as an important therapeutic approach to myocardial infarction (MI)-produced ventricular arrhythmias (VAs). Thus, our research was designed to clarify the potential functions of the SCFA propionate in VAs and cardiac electrophysiology in MI rats. A hundred adult Sprague-Dawley rats were allocated to four groups: the sham group (200 mM sodium chloride), the sham + C3 group (200 mM propionate), the MI group (200 mM sodium chloride) and the MI + C3 group (200 mM propionate). In comparison with the sham group, propionate significantly increased the parasympathetic components heart rate variability (HRV) and acetylcholine levels, prolonged cardiac repolarization, induced STAT3 phosphorylation and up-regulated the c-fos expression in nodose ganglia and solitary nucleus. Propionate intake reduced the susceptibility to VAs. MI induced by coronary ligation caused a significant increase in the sympathetic components HRV, abnormal repolarization, global repolarization dispersion, norepinephrine and inflammatory cytokines, reduction and redistribution of Connexin 43 in the infarcted border zone, and activation of NFκB, which were attenuated in the MI + C3 group. Oral propionate supplementation, as a nutritional intervention, protected the heart against MI-induced VAs and cardiac electrophysiology instability partly by parasympathetic activation based on the gut-brain axis.

The Influence of Remote Ischemic Conditioning on Focal Brain Ischemia in Rats

Despite obvious progress in the treatment of acute forms of ischemic stroke, the risk of this condition remains unacceptably high. Brain infarction in the middle cerebral artery basin occurs in patients with atherosclerosis. The onset of the brain infarction is facilitated by the cessation of circulation (embolism) in conditions of insufficient collateral circulation. The extent of the infarct zone is determined by neuronal death and impaired microcirculation. The development of new methods for effective targeted restorative stroke therapy is crucial for restorative treatment and reducing the risk of mortality after stroke. Remote ischemic conditioning (RIC) is an approach to limiting reperfusion injury in the ischemic region of the brain after focal ischemia. One of the most commonly used in vivo models in stroke studies is the filament model of Middle Cerebral Artery Occlusion (MCAO) in rats. In our experiment, it was performed for 30 min (J. Koizumi) with subsequent 48-hour reperfusion. Within the first 24 hours after the start of reperfusion several short episodes of ischemia in low limbs were induced. After 48 hours of reperfusion the brains were harvested and stained with TTC. Then we evaluated the effect of RIC within 24 hours ex vivo in rats’ brains, as well as syndecan-1 plasma concentration. Infarct area was assessed by means of Image-Pro program with statistical analysis. Infarct volumes in the model group (31.97% ± 2.5%) were significantly higher compared to the values in the RIC group 48 hours after ischemia-reperfusion (13.6% ± 1.3%) (*P < 0.05). A significant reduction in the area of infarction after RIC is likely due to the effect on the regulation of collateral blood flow in the ischemia area. On the second day after ischemia-reperfusion, tissue swelling was reduced in the RIC group compared to the model group. Analysis of the average concentration of Syndecan-1 revealed the difference between model and RIC groups. Syndecan-1, endothelial glycocalyx protein, might be the regulator which performs vascular control of the interaction with inflammatory cell and is responsible for mediate effect of remote ischemic conditioning on the restriction of ischemic-reperfusion injury.

Upregulation of miR-335 reduces myocardial injury following myocardial infarction via targeting MAP3K2.

Acute myocardial infarction (AMI) is a serious cardiovascular disease with a high incidence worldwide and the main cause of sudden cardiac death. The aim of this article was to study the protective role of miR-335 in myocardial infarction (MI) and the underlying molecular mechanism. Thirty Sprague Dawley (SD) rats were randomly divided into sham group, MI + NC group and MI + agomiR-335 group. The expression of miR-335 in rat myocardium was detected by quantitative Real Time-Polymerase Chain Reaction (RT-PCR). Western blot was performed to detect the expression of TNF-α, IL-6, IL-1β, Caspase-3, Cleaved Caspase-3 (C-Caspase-3) and MAP3K2 in rat myocardium. On the 7th day of the establishment of the rat MI model, a high-resolution small animal ultrasound system was utilized to detect the cardiac function of the rats, and the heart tissues and blood samples of the rats were collected. The corresponding kits were purchased to detect the contents of LDH, CK-MB, MDA and SOD in rat serum, and HE staining was employed to observe the morphology of rat myocardial tissue. The expression of miR-335 in myocardial infarcted zones and border zones of MI rats decreased significantly. The upregulation of miR-335 remarkably inhibited myocardial inflammation and apoptosis after MI, thus improving the cardiac function of MI rats. Compared with the sham group, the MAP3K2 expression in the MI + NC group was observably increased, while the overexpression of miR-335 could inhibit the expression of this protein. Through the Luciferase reporter gene experiment, we found that miR-335 could directly target MAP3K2. The expression of miR-335 decreased in myocardial tissue after MI, and the overexpression of miR-335 reduced myocardial damage by inhibiting oxidative stress, inflammation, and apoptosis via targeting MAP3K2, thereby improving the cardiac function of MI rats.

Autologous cell using for the restoration of functional defects in patients with ischemic cerebrovascular accident

Stroke is a global medical and socio-economic problem and a great demand for alternative therapies, the leading one being stem cell (SC) therapy. Pathogenetic processes in ischemic stroke (II) trigger the mechanisms of necrotic and apoptotic death of neurons with the formation of the central infarct zone («core of ischemia») and the ischemic «penumbra» zone; the severity and reversibility of the injury directly depends on the duration of ischemia. In parallel with pathogenetic processes, endogenous neurogenesis occurs – the proliferation of neurogenic stem and progenitor cells (NSC/NPC) and their migration into the ischemic focus; however, most NSCs and newly formed neurons undergo apoptosis and recovery of lost functions does not occur. Significant efforts are being made to find ways to control neurogenesis, in particular through the transplantation of exogenous SCs. The main factors preventing the use of SCs in humans are moral, ethical, religious and legal aspects related to the source and method of obtaining cells, as well as possible immunocompromised complications due to incompatibility of donor cells with the recipient of the main histocompatibility complex antigens. The safest is the use of autologous SCs (the patient’s own cells), as it does not require the use of immunosuppressive protocols. Due to the relative safety and ease of production, the most common are multipotent mesenchymal stem cells (MSCs), namely MSCs of the bone marrow (BM). Numerous preclinical studies in experimental animals with modeled II, as well as clinical trials conducted over the past 15 years, have shown the safety and feasibility of transplantation of autologous MSCs in patients with severe neurological deficits after II. Two different approaches to the use of MSCs are discussed: neuroprotection in the acute phase and neurorestoration in the chronic phase II. Proposals are currently being developed for phase II/III clinical trials in acute and chronic stroke using BM MSCs, the results of which will form the basis for certified standardized II treatment protocols.

Clinical effect of Liyan Tongqiao acupuncture in treatment of post-stroke dysphagia: an analysis based on diffusion tensor imaging

To investigate the clinical change of post-stroke dysphagia after the intervention of Liyan Tongqiao （relieving sore-throat and dredging orifices）acupuncture using cranial diffusion tensor imaging (DTI). A total of 60 patients with post-stroke dysphagia were enrolled and randomly divided into Liyan Tongqiao acupuncture group and neurology treatment group, with 30 patients in each group. The patients in the neurology treatment group were given routine neurology treatment and swallowing rehabilitation training, and those in the Liyan Tongqiao acupuncture group received acupuncture at Sishencong (EX-HN1), Baihui (GV20), bilateral Tai-yang (EX-HN5), and bilateral Fengchi (GB20) and tongue triple acupuncture, with an electroacupuncture apparatus for EX-HN1, bilateral GB20, and tongue triple acupuncture, for a needle retaining time of 30 minutes each time, once a day and 5 times a week, in addition to the treatment in the neurology treatment group. Each course of treatment was 3 weeks, and both groups were treated for 2 courses. Swallowing function assessment and cranial DTI were performed after treatment. After 6 weeks of treatment, both groups had a marked improvement in swallowing function, a significantly greater change in video fluoroscopic swallowing study (VFSS) score and a higher mean FA value (P<0.05). Compared with the neurology treatment group, the Liyan Tongqiao acupuncture group had a marked improvement in swallowing function, a significantly greater change in VFSS score in the pharyngeal phase and a higher mean FA value (P<0.05). Liyan Tongqiao acupuncture can improve dysphagia and swallowing function in the pharyngeal phase in VFSS, possibly by promoting the remodeling of cerebral cortex and increasing the FA value of infarct zone through the stimulation of related acupoint signals.

The Histamine 3 Receptor Is Expressed in the Heart and Its Activation Opposes Adverse Cardiac Remodeling in the Angiotensin II Mouse Model.

Histamine is a basic amine stored in mast cells, with its release capable of activating one of four histamine receptors. The histamine 3 receptor (H3R) is known to be cardioprotective during acute ischemia by acting to limit norepinephrine release. However, a recent study reported that myofibroblasts isolated from the infarct zone of rat hearts responded to H3R activation by up-regulating collagen production. Thus, it is necessary to clarify the potential role of the H3R in relation to fibrosis in the heart. We identified that the mouse left ventricle (LV) expresses the H3R. Isolation of mouse cardiac fibroblasts determined that while angiotensin II (Ang II) increased levels of the H3R, these cells did not produce excess collagen in response to H3R activation. Using the Ang II mouse model of adverse cardiac remodeling, we found that while H3R blockade had little effect on cardiac fibrosis, activation of the H3R reduced cardiac fibrosis and macrophage infiltration. These findings suggest that when activated, the H3R is anti-inflammatory and anti-fibrotic in the mouse heart and may be a promising target for protecting against cardiac fibrosis.

Inhibiting the Pkm2/b-catenin axis drives in vivo replication of adult cardiomyocytes following experimental MI.

Adult mammalian cardiomyocytes (CM) are postmitotic, differentiated cells that cannot re-enter the cell cycle after any appreciable injury. Therefore, understanding the factors required to induce CM proliferation for repair is of great clinical importance. While expression of muscle pyruvate kinase 2 (Pkm2), a cytosolic enzyme catalyzing the final step in glycolysis, is high in end-stage heart failure (HF), the loss of Pkm2 promotes proliferation in some cellular systems, in vivo. We hypothesized that in the adult heart CM proliferation may require low Pkm2 activity. Thus, we investigated the potential for Pkm2 to regulate CM proliferation in a mouse model of myocardial infarction (MI) employing inducible, cardiac-specific Pkm2 gene knockout (Pkm2KOi) mice. We found a lack of cardiac hypertrophy or expression of the fetal gene program in Pkm2KOi mice post MI, as compared to vehicle control animals (P < 0.01), correlating with smaller infarct size, improved mitochondrial (mt) function, enhanced angiogenesis, reduced degree of CM apoptosis, and reduced oxidative stress post MI. There was significantly higher numbers of dividing CM in the infarct zone between 3-9 days post MI (P < 0.001). Mechanistically, we determined that Pkm2 interacts with β-catenin (Ctnnb1) in the cytoplasm of CM, inhibiting Ctnnb1 phosphorylation at serine 552 and tyrosine 333, by Akt. In the absence of Pkm2, Ctnnb1 translocates to the nucleus leading to transcriptional activation of proliferation-associated target genes. All these effects are abrogated by genetic co-deletion of Pkm2 and Ctnnb1. Collectively, this work supports a novel antiproliferative function for Pkm2 in CM through the sequestration of Ctnnb1 in the cytoplasm of CM whereas loss of Pkm2 is essential for CM proliferation. Reducing cardiac Pkm2 expression may provide a useful strategy for cardiac repair after MI in patients.

Abstract 14921: Sulfated Dextran-coated Iron Oxide Nanoparticles Detect Inflammation in the Acute Phase of Myocardialsulfated Dextran-coated Iron Oxide Nanoparticles Detect Inflammation in the Acute Phase of Myocardial Infarction

Introduction: We investigated whether the negatively-charged sulfated dextran-coated iron oxide (SDIO) nanoparticles with higher affinity with macrophage can delineate inflammation more efficiently compared to non-sulfated dextran-coated iron oxide (DIO) nanoparticles in mice LAD ligation model. Methods: After mice were induced with LAD ligation, SDIO or DIO nanoparticles (15mg/kg) were injected intravenously at either day 1, day 3, day 5, and day 7. MRI was performed pre- and post-24 hours later. Dephasing signal loss caused by iron-oxide nanoparticles was detected by gradient echo sequence. Iron uptake was quantified by T2* mapping and calculated as delta R2* (=1/T2*(post)-1/T2*(post)) in the region of interest in the infarct, peri-infarct, and remote zones. Results: SDIO injection produced clear signal voids in the peri-infarct zone at day 3 (n=8), which extend into the infarct zone at day 5 (n=3) (figure). The signal was remarkably decreased at day 7 (n=7). Iron uptake represented by delta R2* in the peri-infarct (80.6±35.7 s -1 ) was significantly higher than that in the infarct (32.3±32.6 s -1 , p&lt;0.001) and the remote (5.1±16.7 s -1 , p&lt;0.0001) at day 3. At day 5, delta R2* in the infarct (91.6±5.4 s -1 , p&lt;0.001) and the peri-infarct (41.0±33.3 s -1 ,p=0.04) were significantly higher than the remote (4.2±14.1 s -1 , p&lt;0.001). DIO did not produce significant change in delta R2* in the peri-infarct or infarct at each time phase. The MRI signals of SDIO corresponded with the area of enhanced vascular permeability peaking at day 3-5, which precedes the macrophage infiltration. Conclusions: SDIO can detect inflammation in the peri-infarct region in the early phase of acute myocardial infarction.

Abstract 16665: Intracoronary Administration of Neonatal Cardiac Mesenchymal Cells Promotes Cardiac Functional Recovery in a Porcine Model of Acute Myocardial Infarction

Background: The strong regenerative potential of neonatal mesenchymal stem cells (nMSCs) in animal MI models when compared to adult MSCs have been attributed to their paracrine secretions. This study determines the therapeutic potential of nMSC-based therapies in a translationally relevant animal large model. Methods: Yorkshire Pigs underwent a 60-minute coronary occlusion followed by reperfusion. Pigs were randomized for intracoronary administration of 10 million nMSCs (n=4), 20 million nMSCs (n=4), 2 mg/kg of TCM (n=4), 10 million nMSCs plus 2 mg/kg TCM (n=5), or placebo (n=4). The infarct size was quantified 48 hours post-infarction. Separate (10 million nMSCs plus 2 mg TCM treated and control) groups were allowed to survive for 28 days, and cardiac MRI (cMR) was performed on post- operative days 7 and 28. Results: After 48hrs, increasing the dose of nMSCs (20 million vs 10 million nMSCs) showed more decrease in infarct size (74+0.03% vs 83.2+0.05%, p =0.25). 2 mg TCM reduced the infarct size in comparison to control (60.8+ 0.09% vs 91+0.03%, p= 0.02). Combination of 10 million nMSCs plus 2 mg TCM achieved the greater reduction of infarct size from 91+ 0.03% to 56+0.02% ( p =0.0002). At 28 days, infarct percent mass to the left ventricle mass was significantly smaller in the combination of 10 million nMSCs and 2mg TCM than control group (3.98+1.7 % vs 13.63 + 3.9%, p =0.003). These combination treated animals showed an increase in stroke volume (+ 10 mL vs - 1.7 mL, p= 0.002) and preserved LV dimensions and ejection fraction by day 28 as compared to day 7. None of the treatment groups showed any end-organ damage. The infarct zone for treated animals showed enhanced angiogenesis and reduced fibrosis, inflammation and apoptosis. Anti-apoptotic signaling molecules related to MAPK pathway are being investigated. Conclusions: Intracoronary infusion of nMSCs-TCM is safe, promotes the strongest cardiac and vascular regeneration by decreasing scar and improving LV function in pigs after AMI. These results provide the rationale for a subsequent translation of a combination allogenic product of nMSCs-TCM to clinical trials.

Systemic Mesenchymal Stem Cell-Derived Exosomes Reduce Myocardial Infarct Size: Characterization With MRI in a Porcine Model.

The observations that mesenchymal stem cells (MSCs) exert cardiac protection and repair via their secretome with the active component(s) identified as exosomes underpinned our test of the efficacy of MSC exosomes in a porcine model of myocardial infarction (MI) when administered systemically by the convenient method of intravenous (IV) bolus injection. Results show that 7 days of IV exosomes results in clear reduction (30–40%) of infarct size measured at both 7 and 28 days post-MI, despite near identical release of hs Troponin T. Together with reduced infarct size, exosome treatment reduced transmurality and lessened wall thinning in the infarct zone. Exosome treated pigs showed relative preservation of LV function with significant amelioration of falls in fractional wall thickening compared with control. However, global measures of LV function were less protected by exosome treatment. It is possible that greater preservation of global LV function may have been attenuated by increased cardiac fibrosis, as T1 values showed significant increase in the exosome pigs compared to control particularly in the infarct related segments. Taken together, these results show clear effects of IV exosomes administered over 7 days to reduce infarct size with relatively preserved cardiac function compared to control treated infarct pigs.

Evolution of left ventricular function after Wharton's jelly mesenchymal stem cells transcoronary administration: 5-year follow up in a pilot cohort of CIRCULATE-AMI Randomized Trial

Abstract Introduction CIRCULATE-Acute Myocardial Infarction is a double-blind controlled trial randomizing (RCT) in 105 consecutive patients with their first, large AMI (cMRI-LVEF ≤45% and/or cMRI-infarct size ≥10% of LV) with successful infarct-related artery (IRA) primary percutaneous coronary intervention (pPCI) to transcoronary administration of Wharton's Jelly Mesenchymal Stem Cells (WJMSCs) vs. placebo (2:1). The pilot study cohort (PSC) preceded the RCT. Aim To evaluate WJMSCs long-term safety, and evolution of left-ventricular (LV) function in CIRCULATE-AMI PSC. Material and methods 30 000 000 WJMSCs (50% labelled with 99mTc-exametazime) were administered via IRA in a ten-patient PCS (age 32–65 years, peak hs-Troponin T 17.3±9.1ng/mL and peak CK-MB 533±89U/L, cMRI-LVEF 40.3±2.7% and infarct size 20.1±2.8%) at ≈5–7 days after AMI using a cell delivery-dedicated, coronary-non-occlusive method. Other treatments were per guidelines. WJMSCs showed an unprecedented high myocardial uptake (30.2±5.3%; 95% CI 26.9–33.5%), corresponding to ≈9×10 000 000 cells retention in the infarct zone – in absence of epicardial flow or myocardial perfusion impairment (TIMI-3 in all; cTFC 45±8 vs. 44±9, p=0.51) or any hs-Troponin T elevation. Five-year follow up included cardiac Magnetic Resonance Imaging (cMRI) (at baseline, 1 year and 3 years) and detailed echocardiography (echo) at baseline, 1 year, 3 years and 5 years. Results By 5 years, one patient died from a new, non-index territory AMI. There were no other cardiovascular events and MACCE that might be related to WJMSCs transplantation. On echo (Fig), there was an increase in left ventricular ejection fraction (LVEF) between WJMSCs administration point and 1 year (37.7±2.9% vs. 48.3±2.5%, p=0.002) that was sustained at 3 years (47.2±2.6%, p=0.005 vs. baseline) and at 5 years: (44.7±3.2%, p=0.039 vs. baseline). LVEF reached a peak at 1 year after the AMI and WJMSCs transfer (Fig). cMRI data (obtained up to 3 years; 1 year 41.9±2.6% vs. 51.0±3.3%, p&amp;lt;0.01; 3 years 52.2±4.0%, p&amp;lt;0.01 vs. baseline) were consistent with the echo LVEF assessment. Conclusions 5-year follow up in CIRCULATE-AMI PSC indicates that WJMSC transcoronary application is safe and may be associated with an LVEF improvement. The magnitude of LV increase appears to peak at 1 year, suggesting a potential role for repeated WJMSCs administration(s). Currently running double-blind RCT will provide placebo-controlled insights into the WJMSCs effect(s) on changes in LV function, remodelling, scar reduction and clinical outcomes. Echo-LVEF evolution Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): STRATEGMED 265761 “CIRCULATE” National Centre for Research and Development/Poland/ZDS/00564 Jagiellonian University Medical College

CXCR7 in cardiomyocytes prevents cardiac dysfunction after myocardial infarction

Abstract Background Beta blockers and angiotensin II receptor blockers take effect through G protein-coupled receptors (GPCRs) and their protective roles in heart failure are partially attributable to beta-arrestin biased agonism. CXCR7, a chemokine receptor, is beta-arrestin biased receptor and one of the most expressing GPCRs in the heart. CXCL12 is a common ligand of CXCR4 and CXCR7 and is known to ameliorate myocardial infarction (MI), reportedly through CXCR4 dependent mechanisms. However, the role of another receptor, CXCR7 and its downstream target including beta-arrestin is not fully elucidated in MI. Purpose The aim of this study is to uncover the role of CXCR7 in cardiomyocytes after MI. Methods First, we quantified CXCR7 mRNA expressions in neonate rat cardiomyocytes (NRCM) in a dish by qRT-PCR. NRCMs were treated with CXCR7 agonist: TC14012 and phosphorylation of extracellular signal regulated kinase (ERK) was measured as readout of the downstream of CXCR7, with immunoblotting. Second, MI was induced by left anterior descending artery (LAD) ligation in male 12-week-old mice. We explored spatial expressions of CXCR7 by qRT-PCR in infarct, peri-infarct and remote zones of wild-type MI mice. Finally, we developed cardiomyocyte-specific CXCR7 knockout mice (cKO) by the Cre/loxP system and analyzed CXCR7 expression in cKO by qRT-PCR. LAD ligation was also performed in cKO and littermate controls (Ctl). Heart weight (HW) was measured and systolic function was examined by echocardiography 4 weeks after ligation. Phosphorylated ERK was evaluated with immunoblotting one-day after ligation. Results First, we found that CXCR7 expression was significantly higher in NRCM than neonatal rat fibroblasts (NRFB) and ERK was phosphorylated by CXCR7 stimulation in NRCM. Second, CXCR7 expression was higher in infarct and peri-infarct zones than remote zones. Finally, cardiomyocyte-specific knockout of CXCR7 resulted in 78±21% reduction of CXCR7 expression in the whole heart. HW and left ventricular area was significantly greater (HW: Ctl 190.7±18.4, cKO 220.3±26.4 mg) and fractional area change of left ventricle was significantly lower in cKO than those in Ctl 4 weeks after MI (LV FAC: Ctl 20.6±4.9%, cKO 13.9±5.4%), indicating that loss of CXCR7 in cardiomyocytes caused left ventricle enlargement and systolic dysfunction. One day after MI of Ctl heart, ERK was more phosphorylated in peri-infarct zone than remote zone. However, this ERK phosphorylation in peri-infarct zone was reduced in cKO MI heart. Conclusion We revealed that CXCR7 is expressed in cardiomyocytes and deletion of this chemokine receptor in cardiomyocytes resulted in ventricle enlargement and systolic dysfunction possibly through ERK phosphorylation in peri-infarct zone. Therefore, CXCR7 in cardiomyocytes could prevent cardiac dysfunction after myocardial infarction, which may be another pathway of CXCL12 dependent-protective effect. Figure 1 Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): JSPS KAKENHI

Cardiac magnetic resonance T1 mapping allows for predicting adverse left ventricular remodeling post-reperfused st-elevation myocardial infarction

Abstract Background Cardiac magnet resonance (CMR) T1 mapping allows the quantitative characterization of the severity of tissue injury and predict functional recovery in acute myocardial infarction (AMI). Purpose The study aimed to investigate whether native T1 and ECV of infarct myocardium are influenced by microvascular obstruction (MVO) and have predictive value for adverse left ventricular (LV) remodeling post-infarction. Method A cohort of 54 patients with successfully reperfused STEMI underwent CMR imaging at a 3T scanner in AMI and 3 months post-infarction. Native T1 data was acquired using a modified Look-Locker inversion recovery (MOLLI) sequence, and ECV maps were calculated using blood sampled hematocrit. Manual regions-of-interest were drawn within the infarct myocardium to measure native T1 and ECV (native T1infarct and ECVinfarct, respectively). MVO identified as a low-intensity area within the infarct zone on LGE was eliminated. Results MVO was present in 36 patients (66.67%) in AMI. ECVinfarct in patients with MVO was different from those without (58.66±8.71% vs. 49.64±8.82%, P=0.001), while no significant difference in T1infarct was observed between patients with and without MVO (1474.7±63.5ms vs. 1495.4±98.0ms, P=0.352). ECV correlated well with the change in end-diastolic volume (all patients: r=0.564, P&amp;lt;0.001) and predicted LV remodeling in patients with and without MVO (rMVO absent = 0.626, P=0.005; rMVO present = 0.686, P&amp;lt;0.001; all patients: r=0.622, P&amp;lt;0.001); Native T1 was only associated with a 3-month change in LV end-diastolic volume (rMVO absent= 0.483, P=0.042) and predicted LV remodeling in patients without MVO (rMVO absent = 0.659, P=0.003). Furthermore, ECV had an association with LV remodeling (β=0.312, P=0.007) in multivariable logistic analysis. Conclusion Absolute native T1 in infarct myocardium might be affected by MVO but ECV isn't. ECV could predict LV remodeling in MI patients with and without MVO, while native T1 predict it in MI with MVO absent. Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): 1·3·5 project for disciplines of excellence, West China Hospital, Sichuan University

Systemic mesenchymal stem cell-derived exosomes reduce myocardial infarct size: characterization with MRI in a porcine model

Abstract Background Mesenchymal stem cells (MSCs) have been shown to exert cardiac protection and repair via their secretome with the active component(s) identified as exosomes. Purpose To determine whether MSC-derived exosomes administered systemically by the convenient method of intravenous (IV) bolus injection reduce infarct size and improve cardiac function in an established porcine model of myocardial infarction (MI). Methods A total of 20 pigs underwent experimental MI by permanent ligation of the left circumflex coronary artery (LCX). Ten pigs (exosome treated) received twice daily IV injection of exosomes (1000ug protein equivalent) for 7 days. The remaining 10 pigs received vehicle control injections. Cardiac structure and function were measured by MRI which was performed at baseline (pre-MI) and repeated on days 7 and 28 post-MI. Infarct size was also confirmed post-mortem. Blood samples were drawn over first 7 days for measurement of hs Troponin T. The study followed the principles of laboratory animal care and was approved by our institution's IACUC. Results All LCX ligations resulted in permanent ischaemia with MI as evidenced by pallor of the myocardium, ECG changes including ST segment elevation and increases in plasma hs Troponin T. Exosomes administered IV for 7 days resulted in clear reduction (30–40%) of infarct size measured at both 7 (p&amp;lt;0.05) and 28 days (p&amp;lt;0.01) post-MI, despite near identical release of hs Troponin T. Together with reduced infarct size, exosome treatment reduced transmurality and lessened wall thinning (p&amp;lt;0.01) in the infarct zone. Exosome treated pigs showed relative preservation of LV function with significant amelioration of falls in fractional wall thickening (p&amp;lt;0.01) compared with control. However, global measures of LV function were less protected by exosome treatment. It is possible that greater preservation of global LV function may have been attenuated by increased cardiac fibrosis, as T1 values showed significant increase in the exosome pigs compared to control particularly in the infarct related segments. Conclusion Taken together, our results show clear effects of IV exosomes administered over 7 days to reduce infarct size with relatively preserved cardiac function compared to control treated infarct pigs. Figure 1 Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): STaR Award (AM Richards), National Medical Research Council, Singapore. IAF-ICP, National Research Foundation, Singapore (RC Lai and SK Lim).

CaMKII inhibition reduces electrical activation heterogeneities caused by mechanical stretch in the myocardium

Abstract Introduction Ca2+/calmodulin-dependant protein kinase II (CaMKII) activity in cardiomyocytes plays a crucial role in their contractility. Increased CaMKII signalling has been associated with mechanical stretch, often caused in the border zone of myocardial infarction. CaMKII upregulation causes a mishandling of intracellular calcium, a precursor of multiple pro-arrhythmic mechanisms, such as early afterdepolarisations. Purpose In this study, we aim to quantify the effects of KN-93 -a CaMKII inhibitor- on wave dynamics, in order to investigate its effectiveness as an anti-arrhythmic agent. Methods An isolated Langendorff model was constructed based on rabbit hearts (n=18) and posteriorly induced to fibrillation. An epicardial multielectrode array (121 electrodes) was used for recording the electrical activity. Mechanical stretch was induced by pushing the anterior myocardial wall from the left-ventricular cavity. Then, a frequency analysis was conducted for the following conditions: before drug infusion, during infusion, during infusion plus stretch, and during infusion post-stretch. Nine hearts represented the untreated group, and the other nine were infused with KN-93 at a concentration of 10 nM (less than 3% of the IC50 value). Results Prior to stretch induction, KN-93 caused no effects in the spectral concentration (SC) and average dominant frequency (ADF) calculated on the infused rabbit hearts. Nevertheless, intrasubject measurements revealed statistically significant differences (p&amp;lt;0.05) between hearts infused with KN-93 and the untreated ones when stretch was induced. Changes in SC were milder in the treated than the untreated group (−6% vs −33%). Also, the stretch-induced increase in ADF was more limited in the treated group (+17% vs +40%). Hearts infused with KN-93 shown a higher resistance to stretch-induced electrical abnormalities, potentially due to better regulated intracellular calcium dynamics. Conclusion CaMKII inhibitors show cardioprotective potential, even at very low concentrations. Further research is required to investigate the therapeutic use of these compounds in conditions of intracellular calcium mishandling and its concomitant life-threatening consequences, such as heart failure or Torsade de Pointes. KN-93 reduces stretch-induced changes Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): Universitat de València; Generalitat Valenciana - Prometeo; Carlos III, CIBERCV

Measuring Post-Stroke Cerebral Edema, Infarct Zone and Blood-Brain Barrier Breakdown in a Single Set of Rodent Brain Samples.

One of the most common causes of morbidity and mortality worldwide is ischemic stroke. Historically, an animal model used to stimulate ischemic stroke involves middle cerebral artery occlusion (MCAO). Infarct zone, brain edema and blood-brain barrier (BBB) breakdown are measured as parameters that reflect the extent of brain injury after MCAO. A significant limitation to this method is that these measurements are normally obtained in different rat brain samples, leading to ethical and financial burdens due to the large number of rats that need to be euthanized for an appropriate sample size. Here we present a method to accurately assess brain injury following MCAO by measuring infarct zone, brain edema and BBB permeability in the same set of rat brains. This novel technique provides a more efficient way to evaluate the pathophysiology of stroke.

Measuring Post-Stroke Cerebral Edema, Infarct Zone and Blood-Brain Barrier Breakdown in a Single Set of Rodent Brain Samples

Measuring Post-Stroke Cerebral Edema, Infarct Zone and Blood-Brain Barrier Breakdown in a Single Set of Rodent Brain Samples

Inflammatory Cytokines Alter Mesenchymal Stem Cell Mechanosensing and Adhesion on Stiffened Infarct Heart Tissue After Myocardial Infarction.

Mesenchymal stem cell (MSC) transplantation has demonstrated its potential in repairing infarct heart tissue and recovering heart function after myocardial infarction (MI). However, its therapeutic effect is still limited due to poor MSC engraftment at the injury site whose tissue stiffness and local inflammation both dynamically and rapidly change after MI. Whether and how inflammatory cytokines could couple with stiffness change to affect MSC engraftment in the infarct zone still remain unclear. In this study, we characterized dynamic stiffness changes of and inflammatory cytokine expression in the infarct region of rat heart within a month after MI. We found that the tissue stiffness of the heart tissue gradually increased and peaked 21 days after MI along with the rapid upregulation of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in the first 3 days, followed by a sharp decline. We further demonstrated in vitro that immobilized inflammatory cytokine IL-6 performed better than the soluble form in enhancing MSC adhesion to stiffened substrate through IL-6/src homology 2 (SH2) domain-containing tyrosine phosphatase-2 (SHP2)/integrin signaling axis. We also confirmed such mechano-immune coupling of tissue stiffness and inflammatory cytokines in modulating MSC engraftment in the rat heart after MI in vivo. Our study provides new mechanistic insights of mechanical–inflammation coupling to improve MSC mechanosensing and adhesion, potentially benefiting MSC engraftment and its clinical therapy for MI.

A Unique Population of Regulatory T Cells in Heart Potentiates Cardiac Protection From Myocardial Infarction.

Regulatory T cells (Tregs), traditionally recognized as potent suppressors of immune response, are increasingly attracting attention because of a second major function: residing in parenchymal tissues and maintaining local homeostasis. However, the existence, unique phenotype, and function of so-called tissue Tregs in the heart remain unclear. In mouse models of myocardial infarction (MI), myocardial ischemia/reperfusion injury, or cardiac cryoinjury, the dynamic accumulation of Tregs in the injured myocardium was monitored. The bulk RNA sequencing was performed to analyze the transcriptomic characteristics of Tregs from the injured myocardium after MI or ischemia/reperfusion injury. Photoconversion, parabiosis, single-cell T-cell receptor sequencing, and adoptive transfer were applied to determine the source of heart Tregs. The involvement of the interleukin-33/suppression of tumorigenicity 2 axis and Sparc (secreted acidic cysteine-rich glycoprotein), a molecule upregulated in heart Tregs, was further evaluated in functional assays. We showed that Tregs were highly enriched in the myocardium of MI, ischemia/reperfusion injury, and cryoinjury mice. Transcriptomic data revealed that Tregs isolated from the injured hearts had plenty of differentially expressed transcripts in comparison with their lymphoid counterparts, including heart-draining lymphoid nodes, with a phenotype of promoting infarct repair, indicating a unique characteristic. The heart Tregs were accumulated mainly because of recruitment from the circulating Treg pool, whereas local proliferation also contributed to their expansion. Moreover, a remarkable case of repeatedly detected T-cell receptor of heart Tregs, more than that of spleen Tregs, suggests a model of clonal expansion. Besides, HelioshighNrp-1high phenotype proved the mainly thymic origin of heart Tregs, with a small contribution of phenotypic conversion of conventional CD4+ T cells, proved by the analysis of T-cell receptor repertoires and conventional CD4+ T cells adoptive transfer experiments. The interleukin-33/suppression of tumorigenicity 2 axis was essential for sustaining heart Treg populations. Last, we demonstrated that Sparc, which was highly expressed by heart Tregs, acted as a critical factor to protect the heart against MI by increasing collagen content and boosting maturation in the infarct zone. We identified and characterized a phenotypically and functionally unique population of heart Tregs that may lay the foundation to harness Tregs for cardioprotection in MI and other cardiac diseases.