Cardiac Function Post-myocardial Infarction Research Articles

Ultrasound-Targeted β-Catenin Gene Therapy Improves the Cardiac Function in Mice After Myocardial Infarction.

Gene therapy has received great attention as a therapeutic approach to improve cardiac function post-myocardial infarction (MI), but its limitation lies in the lack of targeting. This study explored the use of ultrasound-targeted microbubble destruction (UTMD) technique to deliver β-catenin gene to the myocardium, aiming to evaluate its efficacy in preventing cardiac dysfunction post-MI. A cationic microbubble solution containing β-catenin gene pcDNA3.1 plasmid was injected through the tail vein at a rate of 0.6 mL/h, and ultrasound beams were delivered to the heart using GE Vivid 7 Medical Ultrasound System M3s Transducer. Bioluminescence imaging was used to analyze the efficiency of UTMD gene transfection into the myocardium. β-catenin levels were detected by real-time polymerase chain reaction and western blot. Additionally, MI was induced in mice by surgical ligation of the left coronary artery, and cardiac function was evaluated using echocardiography at 14 and 28days post-surgery. Masson's trichrome staining was employed to determine infarct size. Blood vessel density was also measured. TUNEL assay was used to measure cardiomyocyte apoptosis. Furthermore, mouse cardiac stem cells were isolated using flow cytometry, and Giemsa stain was applied to evaluate the colony adhesion. UTMD delivered the gene to the heart with high efficiency and specificity in vivo. The β-catenin expression was significantly increased in the myocardium (P < 0.01). After MI, the β-catenin group exhibited a notable improvement in the gene therapy-induced neovascularization in the border zone (P < 0.01) and the number and function of cardiac stem cells (P < 0.01), and a significant decrease in cardiomyocyte apoptosis in the heart tissue (P < 0.01). β-catenin gene pre-treated with UTMD can reduce the impact of myocardial injury and promote cardiac self-repair after MI.

Abstract 4140122: Bioengineered Self-Adhering Electrospun Nanoscaffolds to Deliver Mitochondrial Antioxidant, JP4-039

Introduction: Treatment of pathologic remodeling and subsequent decline in cardiac function post-myocardial infarction (MI) remains limited. Our lab has previously demonstrated that the targeted mitochondrial antioxidant, JP4-039 (JP4), can abrogate post-MI remodeling and decline in cardiac function, and that JP4 released from electrospun nanoscaffolds improved proliferation and migration of coronary vascular endothelial cells in vitro . The aims of this study were to develop a suture-free, bioadhesive electrospun nanoscaffold that will adhere post-MI cardiac tissue and reliably release JP4 in a localized manner. Hypothesis: Plasma treatment of JP4-loaded biocompatible electrospun nanoscaffold will adhere to cardiac tissue and deliver active moiety of JP4. Methods: A 2% poly(l-lactide-co-glycolide) (PGLA) was electrospun with and without 1% JP4. Nanoscaffolds then underwent plasma treatment for one minute followed by a force adhesion assay. SEM imaging and electron paramagnetic resonance ( EPR ) assays before and after plasma treatment of both control and JP4-loaded patches were performed to examine patch consistency and ensure the release of the unaltered, active structure of JP4. Results: JP4 loading and plasma treatment did not affect fiber dimeter of the scaffolds (p &gt; 0.5 for all; Fig. 1B). JP4-loaded patches demonstrated similar release pattern of the antioxidant’s nitroxide moiety by displaying a characteristic triple peak both before and after plasma treatment as determined by EPR (Fig. 1C). Plasma-treated patches demonstrated significant increase in force adhesion compared to non-treated patches in both the control and JP4-loaded scaffolds (p &lt; 0.0001) (Fig. 1A.). No significant difference in force adhesion was observed between the plasma treated control and JP4 loaded patch (p &gt; 0.05) as determined by ANOVA (Fig. 1A). There was no significant difference in force adhesion between one minute and two minutes of plasma treatment (p &gt; 0.05; Fig. 1A lower panel). Conclusion: The findings demonstrate that plasma-treated biocompatible JP4-loaded patches may reliably adhere to cardiac tissue and release the bioactive component of the mitochondrial antioxidant, JP4.

Reversing metabolic reprogramming by CPT1 inhibition with etomoxir promotes cardiomyocyte proliferation and heart regeneration via DUSP1 ADP-ribosylation-mediated p38 MAPK phosphorylation

The neonatal mammalian heart has a remarkable regenerative capacity, while the adult heart has difficulty to regenerate. A metabolic reprogramming from glycolysis to fatty acid oxidation occurs along with the loss of cardiomyocyte proliferative capacity shortly after birth. In this study, we sought to determine if and how metabolic reprogramming regulates cardiomyocyte proliferation. Reversing metabolic reprogramming by carnitine palmitoyltransferase 1 (CPT1) inhibition, using cardiac-specific Cpt1a and Cpt1b knockout mice promoted cardiomyocyte proliferation and improved cardiac function post-myocardial infarction. The inhibition of CPT1 is of pharmacological significance because those protective effects were replicated by etomoxir, a CPT1 inhibitor. CPT1 inhibition, by decreasing poly(ADP-ribose) polymerase 1 expression, reduced ADP-ribosylation of dual-specificity phosphatase 1 in cardiomyocytes, leading to decreased p38 MAPK phosphorylation, and stimulation of cardiomyocyte proliferation. Our present study indicates that reversing metabolic reprogramming is an effective strategy to stimulate adult cardiomyocyte proliferation. CPT1 is a potential therapeutic target for promoting heart regeneration and myocardial infarction treatment.

Inhibition of B cell activation by Ibrutinib improves cardiac function in experimental myocardial infarction in mice

Abstract Background Bruton's tyrosine kinase (BTK) is a key downstream mediator of B cell receptor (BCR) signaling. Upon BCR cross-linking, phosphorylated BTK modulates B cell activation, proliferation, and differentiation. Ibrutinib, which is clinically used in B-cell malignancies, irreversibly binds to the BTK kinase domain and blunts downstream BTK signaling. Purpose Here, we aimed to monitor B cell dynamics and activation in experimental myocardial infarction (MI) in mice, and evaluate the effect of B cell inhibition by Ibrutinib in cardiac function. Methods MI was induced in male 10-week-old C57BL/6 mice by permanent LAD ligation and Ibrutinib (25 mg/kg/day) was given in the drinking water. After 3, 7, 14, and 28 days, single cell suspensions were prepared for flow cytometry from peripheral blood, spleen, mediastinal lymph nodes (MLNs), and the bone marrow, as well as from the remote and infarcted myocardium. Total B cells and B cell subsets were quantified in the different locations by flow cytometry and B cell activation was monitored by BTK551 phosphorylation. After 28 days, cardiac function was evaluated by echocardiography. Results We found that total B cell numbers decrease in blood and spleen, and increase in MLNs, while plasma cells and plasmablasts increased in the infarcted heart on day 7 and 14 after MI. In the bone marrow, hematopoietic stem cells (HSC) increase after MI, while common lymphoid progenitors (CLP) and early-stage B cell progenitors (pre-pro and pro B cells) peak at day 7 after MI. The later-stage B cell progenitors (pre and immature B cells) showed a biphasic response, with an early decrease after 7 days and a later increase on day 14. Compared to the control group (vehicle), Ibrutinib treatment decreased B cell numbers in MLN and spleen by 27% and 14%, respectively, as well as decreased mature B cells by 28% in the bone marrow on day 28 after MI. Both BTK expression and phosphorylation in pro-B cells were inhibited by Ibrutinib by 8% and 15%, respectively. The inhibition of BTK phosphorylation was also evident in MLNs and spleen. Notably, Ibrutinib-treated mice showed an improved cardiac function on day 28 after MI, with stroke volume (SV) elevated by 41%, left ventricular ejection fraction (LVEF) elevated from 20% to 36% (p &amp;lt; 0.05), and fractional shortening (FS) elevated from 8.8% to 17.59% (p &amp;lt; 0.05). Conclusion Experimental MI leads to B cell lymphopoiesis in the bone marrow, mobilization into the infarcted myocardium, and activation in peripheral lymphoid organs. Ibrutinib treatment inhibits B cell development in the bone marrow, as well as B cell activation in peripheral lymphoid organs, and improves cardiac function post MI. Our data provides a meaningful insight for targeting B cells for the clinical treatment of patients with MI.Figure

A comparative study on the effect of coronary angioplasty on left ventricular function in post myocardial infarction among patients with and without type-2 diabetes mellitus

Background and objectives. Coronary angioplasty is a common intervention for improving cardiac function postmyocardial infarction. However, the impact of this procedure in patients with type-2 diabetes mellitus (T2DM) compared to those without diabetes remains less understood. Material and methods. This study included 50 patients who underwent coronary angioplasty post-myocardial infarction. Patients were divided into two groups based on the presence (Group A) or absence (Group B) of T2DM, with 6 patients in each group. We assessed left ventricular function using echocardiography, focusing on ejection fraction and wall motion score, at baseline, and at 1, 3, and 6 months post-angioplasty. Additional data on clinical outcomes, functional status, cardiac biomarkers, medication use, comorbid condition management, and hemodynamic measurements were also collected. Results. Both groups showed improvement in left ventricular function post-angioplasty, with no significant difference in ejection fraction and wall motion score between the two groups at each follow-up. Clinical outcomes, functional status, and biomarker levels were comparable between groups. Medication compliance was high in both groups. The control of comorbid conditions and hemodynamic stability post-angioplasty were similarly maintained in both diabetic and nondiabetic patients. Conclusion. Coronary angioplasty positively impacts left ventricular function in post-myocardial infarction patients, irrespective of the presence of T2DM. Both diabetic and non-diabetic patients demonstrated similar improvements in cardiac function and overall clinical outcomes, suggesting that angioplasty is an effective intervention for post-myocardial infarction patients regardless of their diabetes status. Further studies with larger sample sizes are recommended to validate these findings.

Abstract We130: Novel Role of RBFox1 in Myocardial Infarction Induced Heart Failure

Introduction: Alternative mRNA splicing affects a broad spectrum of cardiac genes during pathological manifestation of heart diseases. Earlier studies from our lab have identified a muscle-specific isoform of RBFox1 to be a key RNA splicing regulator in pressure overload induced heart failure through regulating cardiac transcription factor alternative splicing. However, the physiological impact of RBFox1 in myocardial infarction (MI), and the RBFox1 downstream mRNA alternative splicing events during MI induced cardiac remodeling remains unknown. Goals: To investigate the functional impact of RBFox1 in MI induced cardiac remodeling. Method and Results: At both mRNA and protein levels, we found RBFox1 to be significantly decreased in Sprague-Dawley Rat hearts post MI. To investigate the functional impact of RBFox1 in myocardial infarction, we utilized AAV9 to achieve cardiac specific expression of RBFox1 in rats. Interestingly, expression of RBFox1 prevented cardiac dysfunction post MI characterized by improved cardiac function based on echocardiography. Expression of RBFox1 further reduced hypertrophy, cell death and fibrotic remodeling at both molecular and histological levels post MI. In vitro, expression of RBFox1 is sufficient to prevent hypoxia induced cardiac cell death based on TUNEL staining and cleaved caspase 3 level, while inactivation of RBFox1 promoted cardiac cell death. To further understand the molecular mechanism underlying RBFox1 mediated cardiac protection, we performed RNA-seq analysis to determine the transcriptome changes in vivo. RNA-seq showed insulin secretion, cAMP signaling and muscle contraction pathways to be top significantly changed pathways in RBFox1 expressed rat hearts post MI. Lastly, we have identified Mbnl1 mRNA alternative splicing to be regulated by RBFox1 through promoting a 36bp exon exclusion at the C-terminal of Mbnl1 protein, potentially affecting the function of Mbnl1. Conclusion: In summary, we have identified a previously uncharacterized role of RBFox1 in myocardial infarction injury. RBFox1 expression is critical to preserve cardiac function post MI, potentially through regulating downstream targets alternative splicing, including Mbnl1.

Design of a Zn-based nanozyme injectable multifunctional hydrogel with ROS scavenging activity for myocardial infarction therapy

The existing strategies for myocardial infarction therapy mainly focus on reinstating myocardial blood supply, often disregarding the intrinsic and intricate microenvironment created by elevated levels of reactive oxygen species (ROS) that accompanies myocardial infarction. This microenvironment entails cardiomyocytes apoptosis, substantial vascular cell death, excessive inflammatory infiltration and fibrosis. In such situation, the present study introduces a zinc-based nanozyme injectable multifunctional hydrogel, crafted from ZIF-8, to counteract ROS effects after myocardial infarction. The hydrogel exhibits both superoxide dismutase (SOD)-like and catalase (CAT)-like enzymatic activities, proficiently eliminating surplus ROS in the infarcted region and interrupting ROS-driven inflammatory cascades. Furthermore, the hydrogel's exceptional immunomodulatory ability spurs a notable transformation of macrophages into the M2 phenotype, effectively neutralizing inflammatory factors and indirectly fostering vascularization in the infarcted region. For high ROS and demanding for zinc of the infarcted microenvironment, the gradual release of zinc ions as the hydrogel degrades further enhances the bioactive and catalytic performance of the nanozymes, synergistically promoting cardiac function post myocardial infarction. In conclusion, this system of deploying catalytic nanomaterials within bioactive matrices for ROS-related ailment therapy not only establishes a robust foundation for biomedical material development, but also promises a holistic approach towards addressing myocardial infarction complexities. Statement of significanceMyocardial infarction remains the leading cause of death worldwide. However, the existing strategies for myocardial infarction therapy mainly focus on reinstating myocardial blood supply. These therapies often ignore the intrinsic and intricate microenvironment created by elevated levels of reactive oxygen species (ROS). Hence, we designed an injectable Zn-Based nanozyme hydrogel with ROS scavenging activity for myocardial infarction therapy. ALG-(ZIF-8) can significantly reduce ROS in the infarcted area and alleviate the ensuing pathological process. ALG-(ZIF-8) gradually releases zinc ions to participate in the repair process and improves cardiac function. Overall, this multifunctional hydrogel equipped with ZIF-8 makes full use of the characteristics of clearing ROS and slowly releasing zinc ions, and we are the first to test the therapeutic efficacy of Zinc-MOFs crosslinked-alginate hydrogel for myocardial infarction.

Abstract GS.09: Interleukin 13 Signaling To Macrophages Promotes Recovery After Myocardial Infarction In Mice

Introduction: There is great interest in identifying signaling pathways that promote pro-reparative macrophage phenotypes in the heart. Considering the remarkable cardiac healing potential of neonatal mice, we employ this model to identify pro-reparative mechanisms that can be applied to promote cardiac repair in adults after myocardial infarction (MI). We show that IL13/IL4Rα signaling specifically on macrophages mediates neonatal heart regeneration and activation of this pathway in adult mice promotes cardiac functional recovery in post-MI. Results: We developed IL4Rα fl/fl ;CX3CR1 Cre mice (IL4Rα MacKO ) to delete IL4Rα specifically in macrophages. Neonatal IL4Rα MacKO and control mice were subjected to MI on postnatal day 1 (P1). Following injury, IL4Rα MacKO mice had significantly larger scars at 8 days post injury (dpi) and lower ejection fraction and capillary density at 21 dpi. Thus, macrophage IL4Rα expression is critical for cardiac functional recovery following injury in neonates. Using fluorescent reporter mice, we found that IL13, a ligand for IL4Rα, is produced almost exclusively by type 2 innate lymphoid cells in the neonatal heart. Interestingly, we didn’t find any cellular source of IL13 in the adult mouse heart. Considering the decline in cardiac production of IL13 from neonatal to adult stages, we postulated that reactivation of IL4Rα in the adult heart would improve cardiac healing post MI in adults. Indeed, daily IL13 administration significantly improved cardiac function post MI in adult mice, and this improvement was mediated entirely by IL4Rα expression on macrophages as IL4Rα MacKO mice showed no functional improvement with IL13 administration. Intriguingly, while IL13 administration to control mice improved cardiac function, administration to IL4Rα MacKO mice further exacerbated post MI mortality and scar size compared to animals receiving PBS, suggesting multiple cardiac cell types respond to IL13 resulting in beneficial or detrimental outcomes. Conclusions: Our data elucidates a strongly pro-reparative role for IL13 signaling directly to macrophages. While this signaling pathway is active in neonatal stages, we demonstrate that re-activation by IL13 administration is required to promote cardiac repair in adults.

Abstract P2014: Knockout Of Prostaglandin E2 Ep3 Receptor Improves Cardiac Function In Both Sexes In A Mouse Model Of Myocardial Infarction

Prostaglandin E 2 is an autacoid that acts through 4 G-protein-coupled receptors (EP1-EP4). We previously reported that expression of the EP3 receptor increases after myocardial infarction (MI) and mediates reduced cardiac function. This effect was exacerbated in mice that overexpress EP3 in the cardiomyocytes. Furthermore, we reported that the EP3 receptor antagonist, L798106 reduced blood pressure in the Angiotensin II hypertension model and improved cardiac function. We therefore hypothesized that cardiomyocyte specific knock-out of EP3 (EP3 KO) and/or pharmacological antagonism of EP3 protects the heart from cardiac dysfunction after MI. To test our hypothesis, we created a cardiomyocyte specific (αMHC promoter), tamoxifen inducible CM-EP3 KO mouse. Fifteen-week-old male and female EP3 KO and floxed controls underwent sham or MI surgery. After 2 wks, echocardiography was performed, and all statistical analysis was performed by a biostatistician at Henry Ford Health. There were no significant differences in cardiac function between strains after sham operation. After 2 wks MI, male floxed control mice showed significant reductions in ejection fraction (EF;68 ± 5.6 % sham vs 49.1 ± 5.2 % MI; p&lt;0.05), coupled with increased left ventricle dimension at systole (LVDs;1.12 ± 0.08 mm sham vs 2.08 ± 0.34 mm MI; p&lt;0.05). Remarkably, however, these changes were not observed for EP3 KO mice post-MI. EF was 73.1 ± 0.68% in sham vs 69.0 ± 0.81% for MI; and LVDs was 1.09 ± 0.05 in sham vs 1.09 ± 0.04 for MI. Similarly, EF was 66.3 ± 2.4% in female sham mice and remained unchanged after MI (EF; 62.7 ± 2.3% in EP3 KO MI). To investigate a more translational and therapeutic approach, we examined whether daily administration of L798106 improves cardiac function post MI. Male C57BL/6 mice were subject to MI and assigned to vehicle or L798106 treatment (40 μg/Kg/day, s.c.) beginning 3 days post-surgery. After 2 wks, EF was substantially improved from 36.0 ± 2.6% in vehicle vs 49.4 ± 3.0% in L798106, p&lt;0.01. Similar improvements were observed in fractional shortening. Altogether, these data suggest that EP3 may play a direct role in regulating cardiac function and future experiments are warranted to investigate the use of an EP3 antagonist as a potential therapeutic in heart failure.

Abstract P313: Knockout Or Antagonism Of The Prostaglandin E2 Ep3 Receptor Is Protective In A Mouse Model Of Myocardial Infarction

Prostaglandin E 2 is an autacoid that acts through 4 G-protein-coupled receptors (EP1-EP4). We previously reported that expression of the EP3 receptor increases after myocardial infarction (MI) and mediates reduced cardiac function. Moreover, we reported that a selective EP3 antagonist (L798,106) prevents reduced cardiac function in Angiotensin II hypertension. We therefore hypothesized that cardiomyocyte specific knock-out and/or pharmacological inhibition of EP3 protects the heart from cardiac dysfunction after MI. To test our hypothesis, we created a conditional cardiomyocyte-specific EP3 knockout mouse (EP3 KO) by crossing EP3 fl / fl mice with a tamoxifen-inducible αMHC-MerCreMer mouse. Fifteen-week-old male EP3 KO and EP3 fl / fl underwent sham or MI surgery. After 2 wks cardiac function was assessed by echo and western blot was performed. There were no significant differences in cardiac function between strains after sham operation. After MI, EP3 fl/fl mice showed significant reductions in ejection fraction (EF;68 ± 5.6 % sham vs 49.1 ± 5.2 % MI; p&lt;0.05), coupled with increased left ventricle dimension at systole (LVDs;1.12 ± 0.08 mm sham vs 2.08 ± 0.34 mm MI; p&lt; 0.05). However, these changes were not observed for EP3 KO mice post-MI. EF was 73.1 ± 0.68% in sham vs 69.0 ± 0.81% for MI; and LVDs was 1.09 ± 0.05 in sham vs 1.09 ± 0.04 for MI. Additionally, phosphorylated phospholamban protein levels were significantly reduced after MI in EP3 fl/fl mice (1.14 ± 0.2 A.U. in sham to 0.42 ± 0.2 A.U. in MI; p&lt;0.05) whereas they were not altered after MI in EP3 KO mice (1.37 ± 0.5 A.U. in sham to 1.55 ± 0.4 A.U. in MI). We next determined whether daily treatment with L798, 106 would improve cardiac function post MI. C57BL/6 mice were subject to MI and assigned to vehicle or L798,106 treatment groups (40 μg/Kg/day, s.c.) 3 days post-surgery. After 2 wks, EF was improved from 36.4 ± 4.6 % in vehicle-treated mice to 47.3 ± 5.1% in mice receiving L798,106. Fractional shortening also was improved from 17.6 ± 2.5 % in vehicle-treated mice to 24.0 ± 2.9% in L798,106 -treated mice. Altogether, these data suggest that EP3 may play a direct role in regulating cardiac function and future experiments are warranted to investigate the use of an EP3 antagonist as a potential therapeutic in heart failure.

Abstract P1140: Scaling Up Engineered Cardiac Tissue For Clinical Translation As A Regenerative Therapy

Advances in cardiovascular interventions have significantly decreased mortality due to acute myocardial infarction (MI). However, heart failure (HF) as a main sequela remains a major and devastating health burden. Globally, ~13 million people suffer from HF with systolic dysfunction and have no clinically available treatment to remuscularize their failing heart. Regenerative therapies using cardiomyocytes derived from embryonic or human-induced pluripotent stem cells (hiPSC-CMs) have emerged in large animal models and clinical trials to stabilize cardiac function post MI. Delivery of CMs through epicardially-implanted engineered cardiac tissues (ECTs) is advantageous as increased CM maturity, improved engraftment and increased mechanical support of the cardiac wall have been reported as compared to intramuscular CM injection. To date, however, the lack of rigorous studies exploring ECTs scaled to clinically relevant size (&gt;3x3cm) poses an immense hurdle to their use in clinical trials. To this end, we are focused on understanding how such ECT scale up impacts the electromechanical function of the tissue. Our work details the differentiation and proliferative expansion of hiPSC-CMs to achieve the quantity and quality of hiPSC-CMs required for clinically scaled ECTs. We fabricate ECTs by mixing hiPSC-CMs with 5% human cardiac fibroblasts in a collagen-1 hydrogel with electromechanical function assessed through optical mapping of action potential and tensile mechanical testing. We report compromised electromechanical function and structural organization of ECTs with scale up, which is ameliorated by maturation of hiPSC-CMs using drug and metabolic interventions. Because larger animals will require higher CM density in implants, we evaluated the impact of CM density on ECT formation and function. Increasing CM density (30x10 6 vs 5x10 6 hiPSC-CMs/mL) decreased ECT compaction by 70% while increasing active force generation by 5.5-fold and contractile upstroke velocity by 4.3-fold. In conclusion, we have identified the design space for fabricating ECT of clinically relevant size. By understanding the space and its functional impact, this work supports the translational feasibility of ECTs as a regenerative treatment for the failing heart.

Impaired regulation of MMP2/16-MLCK3 by miR-146a-5p increased susceptibility to myocardial ischaemic injury in aging mice.

Aging impairs cardiac function and increases susceptibility to myocardial ischaemic injury. Cardiac myosin light chain kinase (MLCK3) phosphorylates cardiac myosin regulatory light chain (MLC2), controlling sarcomere organization and cardiomyocyte contraction. Dysregulation of MLCK3 and phosphorylated MLC2 (p-MLC2) contributes to heart failure after myocardial infarction (MI). We aimed at exploring how the MLCK3-p-MLC2 axis changes in aging hearts post MI and at investigating the underlying regulatory mechanisms. We generated adult (3 months) and aged (30 months) MI mouse models to compare their cardiac performance, and then detected MLCK3 expression and MLC2 activity. Aging increased the size of MI-induced infarctions and promoted cardiac contractile dysfunction. Furthermore, MLCK3 expression and MLC2 activity increased in adult hearts after MI, but not in aged hearts. miR-146a was found consistently increased in adult and aged hearts post MI. Mechanistic analyses performed in vitro demonstrated that miR-146a-5p down-regulated matrix metalloprotease (MMP)2/16 expression in cardiomyocytes. This down-regulation in turn increased MLCK3 expression and MLC2 activity. However, miR-146a-5p failed to regulate the MMP2/16-MLCK3-p-MLC2 axis in senescent cardiomyocytes or in cardiac miR-146a conditional knockout mice, with the latter experiencing an exacerbated deterioration of cardiac function post MI. These results suggest that an increase of MLCK3 and p-MLC2 contents through decreasing MMP2/16 by miR-146a-5p represents a compensatory mechanism that can protect cardiac contractile function after MI. Aging impairs this miR-146a-5p-regulated MMP2/16-MLCK3-p-MLC2 contractile axis, leading to compromised contractile function and increased susceptibility to heart failure.

Mdivi-1 alleviates cardiac fibrosis post myocardial infarction at infarcted border zone, possibly via inhibition of Drp1-Activated mitochondrial fission and oxidative stress

Mitochondrial division inhibitor 1(Mdivi-1) has been shown to play a beneficial role in a variety of diseases, mainly by inhibiting Drp1-mediated mitochondrial fission. The effects of Mdivi-1 on cardiac fibrosis at infarcted border zone area and its possible mechanism remain unclear. This study aimed to investigate the effects of Mdivi-1 on reactive cardiac fibrosis and cardiac function post myocardial infarction and its potential mechanisms. Mice were randomly divided into six groups (n = 9 for each group): Sham; Mdivi-1; MI 7d; MI 14d; MI 28d; MI 28d + Mdivi-1. The MI model was induced by ligation of LAD coronary artery. Mdivi-1 (1 mg/kg) was administered to mice every other day at a time from the second day until the sacrifice of the mice (total 14 injection of Mdivi-1). In vitro experiments, the effect of Mdivi-1 on TGF-β1-induced fibrosis-related pathophysiological changes of fibroblasts was examined in NIH3T3 cells. We found that Mdivi-1 significantly attenuated fibroblast activation, collagen production and fibrosis at infarcted border zone after MI, improved impaired heart function. Mechanistically, we observed that Mdivi-1 reduced the protein expression of P-Drp1-S616 and abnormal mitochondrial fission of cardiac fibroblasts in the infarcted border zone area. In addition, we found that the effects of Mdivi-1 partially relied on increasing the expression of Hmox1 and inhibiting oxidative stress. In conclusion, Mdivi-1 could attenuate cardiac fibrosis at infarcted border zone and improve impaired heart function partially through attenuation of Drp1-mediated mitochondrial fission. Moreover, inhibition of oxidative stress, which is possible due to the up-regulation of Hmox1, may be another potential mechanism of action of Mdivi-1.

CTRP1 Aggravates Cardiac Dysfunction Post Myocardial Infarction by Modulating TLR4 in Macrophages.

CTRP1 (C1q/TNF-α [tumour necrosis factor-α]-related protein 1), an adiponectin paralog, is associated with diabetes and adverse events in cardiovascular disease. However, its effect on cardiac function post myocardial infarction (MI) is unclear. Our study aimed to explore the role of CTRP1 in cardiac function post MI. CTRP1 global knockout mice were subjected to left anterior descending ligation to establish the MI model. C57BL6J mice were also administered recombinant CTRP1 protein (200 μg/kg) 7 days post MI. As a result, mice with CTRP1 deficiency exhibited an increased survival rate, a reduced infarct area, improved cardiac function and decreased inflammation and oxidative stress levels at 4 weeks post MI compared with those of mice receiving the CRTP1 injection, whose conditions deteriorated. However, cardiomyocytes with either CTRP1 silencing or CTRP1 treatment showed few differences in inflammation and oxidative stress levels compared with those of the control under hypoxic conditions. The activation of macrophages isolated from CTRP1-deficient mice was decreased in response to interferon-γ, while CTRP1 enhanced the activation of macrophages in response to interferon-γ. Macrophage scavengers and clodronate liposomes antagonized the effects of CTRP1 injection in mice. We also found that CTRP1 regulated macrophage activation via adiponectin receptor 1, which binds to TLR4 on the macrophage membrane. TLR4 knockout also antagonized the effects of the CTRP1 protein on mice with MI. Taken together, these data indicate that CTRP1 supresses cardiac function post MI via TLR4 on macrophages. Targeting CTRP1 may become a promising therapeutic approach to cardiac dysfunction post MI.

A Polypeptide from Circular RNA CDYL2 Accelerates Apoptosis via Stabilizing APAF1 in Cardiomyocytes

CircRNA, mainly derived from exons, lacks coding ability for the absence of 5’ Cap and 3’ poly (A) tail. Increasing evidence indicated that circRNA is closely associated with cardiovascular diseases via sponging miRNAs. However, few studies focused on the role of polypeptides from circRNA in heart. Here, we identified a circRNA (circ-Cdyl2) from CDYL2 (Chromodomain Y-like 2) increasing remarkably in vitro (hypoxia and low-glucose treated cardiomyocytes) or in vivo (failing heart post MI (myocardial infarction)) and coding a polypeptide termed Cdyl2-60aa for the presence of IRES (Internal Ribosomal Entry Sites). Cdyl2-60aa could stabilize the APAF1 (apoptotic protease activating factor-1) via blocking its interaction with HSP70 (heated shock protein 70) and in turn accelerated cell apoptosis. Results in vivo showed that the reduction of circ-Cdyl2 could significantly slow the deterioration of cardiac function post MI. In conclusion, our work discovered that circ-Cdyl2 promotes cell apoptosis via Cdyl2-60aa/APAF1 axis.

The role of nutritional additives in prevention: dietary supplementation with Spirulina reduces myocardial damage and improves cardiac function post-myocardial infarction in swine

Abstract Introduction The outcome of acute ST-elevation myocardial infarction depends, to a large extent, on the size of the infarct. Myocardial damage due to infarction involves several pathogenic mechanisms among which excessive generation of reactive oxygen species and an exacerbated inflammatory reaction play a critical role. Spirulina is a dietary supplement made from blue-green algae (Arthrospira platensis) used to manage weight loss and metabolic syndrome disorders. In addition, Spirulina has experimentally shown to exert anti-oxidant and anti-inflammatory properties because its composition rich in antioxidants, polyunsaturated fatty acids, essential amino-acids, and minerals. Purpose The purpose of the present study was to investigate whether dietary supplementation with Spirulina may serve as a cardioprotective agent by attenuating cardiac damage and ventricular dysfunction due to myocardial infarction in a highly translatable animal model. Methods Pigs (n=10) were fed a normocholesterolemic diet supplemented with Spirulina (1 gr/animal/bid; n=5) or placebo (n=5) for 10 days and then they were subjected to myocardial infarction by means of 1.5h balloon occlusion of the mid left anterior descending coronary artery. Thereafter animals were reperfused for 2.5h and then sacrificed. Infarct size was assessed by TTC staining and ischemic and non-ischemic myocardial tissue was obtained for molecular analysis of cardioprotective kinases, anti-apoptotic- and anti-inflammatory- related markers. Biochemical analyses (lipid levels, kidney and liver parameters) and weight gain were monitored throughout the study. Results Supplementation with Spirulina led to an absolute significant reduction in infarct size of 10±1% of the left ventricle (LV) as compared to control animals (p&amp;lt;0.05). At a functional level, all animals displayed comparable LV ejection fraction (LVEF) prior-MI induction (control: 64.5±2.6%; Spirulina: 61.5±2.6%). However, after 2.5h of reperfusion control animals showed a worsening of 18.2±2.0% LVEF whereas it was only of 7.2±2.5% in Spirulina-administered pigs (60% relative improvement vs. controls; p&amp;lt;0.05). At a molecular level, Spirulina administered animals showed higher expression of PI3K, Bcl-2, and Cox-2 and reduced content of MCP-1 in the jeopardized myocardium. Supplementation with Spirulina for 10 days markedly reduced total- cholesterol by 25% (p&amp;lt;0.04), LDL- cholesterol by 47% (p&amp;lt;0.05), enhanced HDL-cholesterol concentration by 79% (p&amp;lt;0.03) and limited weight gain (p&amp;lt;0.05) as compared to controls. Kidney and liver enzymes were found to be within the physiological range. Conclusion Supplementation with Spirulina, beyond its proven benefits in weight loss and lipid profile, exerts cardioprotection by inducing myocardial survival kinases, and triggering cytoprotective and anti-inflammatory mechanisms, thereby limiting cardiac damage and improving ventricular contractility post-MI. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Ministerio de Ciencia Innovacion y Universidades / Instituto de Salud Carlos III

Effects of exercise on BDNF-TrkB signaling in the paraventricular nucleus and rostral ventrolateral medulla in rats post myocardial infarction

Brain-derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) signaling in the paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) is associated with cardiovascular regulation. Exercise increases plasma BDNF and attenuates activation of central pathways in the PVN and RVLM post myocardial infarction (MI). The present study assessed whether MI alters BDNF-TrkB signaling and intracellular factors Ca2+/calmodulin-dependent protein kinase II (CaMKII) and Akt in the PVN and RVLM of male Wistar rats with or without exercise or treatment with the TrkB blocker ANA-12. A 4-week period of treadmill exercise training was performed in MI rats. A separate experiment was conducted with 2.5 mg/kg ANA-12 in sedentary MI rats. At 5 weeks post MI, in both the PVN and RVLM, the ratio of full-length TrkB (TrkB.FL) and truncated TrkB (TrkB.T1) was decreased. 0.5 mg/kg ANA-12 did not affect BDNF-TrkB signaling and cardiac function post MI, but 2.5 mg/kg ANA-12 further decreased ejection fraction (EF). Exercise increased mature BDNF (mBDNF) and decreased Akt activity in the PVN, whereas in the RVLM, exercise did not affect mBDNF but lowered p-CaMKIIβ. ANA-12 prevented the exercise-induced increase in mBDNF in the PVN and decrease in p-CaMKIIβ in the RVLM. In conclusion, exercise decreases Akt activity in the PVN and decreases p-CaMKIIβ in the RVLM post MI. BDNF-TrkB signaling only mediates the decrease in p-CaMKIIβ in the RVLM. The exercise-induced decreases in Akt activity in the PVN and p-CaMKIIβ in the RVLM may contribute to the attenuation of the decrease in EF and sympathetic hyperactivity post MI.

Augmentation of Zinc Concentration in Blood has a Favorable Effect on Cardiac Function Post-Myocardial Infarction

Background: We have recently reported that polaprezinc which is a zinc delivery has an anti-inflammatory effect and improves cardiac function after acute myocardial infarction (AMI). As a secondary analysis, the aim of the present study was to evaluate if zinc concentration in blood affects anti-inflammatory effect and cardiac function after AMI. Methods: The primary study population included 50 patients with AMI. We equally divided the patients into two groups between the high group (H) and the low group (L) by blood concentration of zinc without relating to polaprezinc medication. The two groups were analyzed about cardiac function, cardiac enzymes, and the levels of the inflammation marker interleukin-6 (IL-6) as similar to the primary study. Results: The urine zinc levels of the H group were prominently higher than those of the L group at 8 days after PCI. The mean IL-6 level was strongly reduced in the H group (44.7(7.15-107.7) pg/mL vs. 130(19.6-384.25) pg/mL, respectively; p&lt;0.05). As for the days of decline of both CRP and WBC, there were significant differences between the two groups (Figure 2). In addition, echocardiography indicated that the EF of the H group was clearly increased between day 3 and 9 months post-MI (54.5(50.5-59.75)% vs. 62(55-70)%, respectively; p&lt;0.01). Conclusions: The present study suggests that high concentration of zinc has an anti-inflammatory effect and improves cardiac function after AMI.

Effects of intramyocardial injection of human neonatal cardiac progenitor cells on cardiac function, circulating biomarkers and scar size post myocardial infarction in nude rats

Effects of intramyocardial injection of human neonatal cardiac progenitor cells on cardiac function, circulating biomarkers and scar size post myocardial infarction in nude rats

Abstract 491: Small Gtpase Rhoe Regulates Inflammatory Response in Myocardial Infarction

Background: Myocardial infarction (MI) is a severe clinical condition caused by coronary artery thrombotic occlusion. An acute inflammatory response to MI is essential for cardiac healing, while excessive and prolonged inflammation causes cytotoxic damages and provokes adverse cardiac remodeling. In the present study, we demonstrate a novel inflammatory mediator, RhoE, and its cardioprotective role in MI. Methods: We use three genetic mouse lines in this study: global RhoE knockout, cardiac-specific RhoE haploinsufficient, and cardiac-specific RhoE overexpression mice. Cardiac function and inflammation in the first week post MI are assessed in mice receiving left anterior descending artery (LAD) ligation. Mechanistic study is conducted through a set of molecular signaling experiments including bimolecular fluorescence complementation (BiFC), immunoprecipitation, electrophoretic mobility shift assay and mRNA microarray analysis. Finally, we investigate the expression and clinical significance of RhoE in MI patients. Results: RhoE is upregulated in mouse post MI. RhoE deletion leads to upregulation of pro-inflammatory genes in mouse embryo heart. RhoE haploinsufficiency causes excessive inflammatory response with deleterious cardiac function post MI, while RhoE overexpression restrains post-MI inflammation and preserves cardiac function and survival. Mechanistically, RhoE specifically inhibits NF- κB activation in vivo and in vitro. RhoE binds to p65 and p50 individually in cytosol, blocking their dimerization and nuclear translocation. Consistent with findings in the mouse MI model, MI patients with higher RhoE expression show diminished cardiac inflammation and consequently a better prognosis. Conclusions: This study identified RhoE as a fine-tuning factor modulating post-MI inflammation. RhoE expression level in heart positively correlates with the outcomes of MI patients. Impact: The discovery of RhoE provides a potential therapeutic target for MI. RhoE abundance in the heart post-MI might be used for prognosis assessment.