Infarcted Rat Hearts Research Articles

Activation of a GPCR, ORL1 Receptor: A Novel Therapy to Prevent Heart Failure Progression.

The number of ischemic heart failure (HF) patients is growing dramatically worldwide. However, there are at present no preventive treatments for HF. Our previous study showed that Gata4 overexpression improved cardiac function after myocardial infarction in rat hearts. We also found that Gata4 overexpression significantly increased the expression of a Pnoc gene, an endogenous ligand for the cell membrane receptor ORL1. We hypothesized that the activation of the ORL1 receptor would suppress HF in a rat ischemic heart model. Adult Sprague Dawley rats (8 weeks old, six males and six females) underwent left anterior descending coronary artery ligation. Three weeks later, normal saline or MCOPPB (ORL1 activator, 2.5 mg/kg/day) intraperitoneal injection was started, and continued 5 days a week for 3 months. Echocardiography was performed six times: pre-operative, 3 days after coronary artery ligation, pre-MCOPPB or saline injection, and 1, 2, and 3 months after saline or MCOPPB injection started. Animals were euthanized after 3 months' follow-up and the hearts were harvested for histological analysis. The ORL1 activator, MCOPPB, significantly improved cardiac function after myocardial infarction in rats (ejection fraction, MCOPPB vs. saline at euthanasia, 67 ± 3% vs. 43 ± 2%, p < 0.001). MCOPPB also decreased fibrosis and induced angiogenesis. Thus, the ORL1 activator, MCOPPB, may be a novel treatment for preventing HF progression.

Flavin-containing monooxygenase 2 confers cardioprotection in ischemia models through its disulfide-bond catalytic activity.

Myocardial infarction (MI) is characterized by massive cardiomyocytes death and cardiac dysfunction, and effective therapies to achieve cardioprotection are sorely needed. Here we reported that flavin containing monooxygenase 2 (FMO2) level was markedly increased in cardiomyocytes both in ex vivo and in vivo models of ischemia injury. Genetic deletion of FMO2 resulted in reduced cardiomyocyte survival and enhanced cardiac dysfunction, whereas cardiomyocyte-specific FMO2 overexpression exerted a protective effect in infarcted rat hearts. Mechanistically, FMO2 inhibited the activation of endoplasmic reticulum (ER) stress-induced apoptotic proteins, including caspase 12 and C/EBP homologous protein (CHOP), by down-regulating unfolded protein response (UPR) pathway. Furthermore, we identified FMO2 as a chaperone that catalyzed disulfide-bond formation in unfolded/misfolded proteins through its GVSG motif. GVSG-mutated FMO2 failed to catalyze disulfide-bond formation and lost its protection against ER stress and cardiomyocyte death. Finally, we demonstrated the protective effect of FMO2 in human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) model. Collectively, this study highlights FMO2 as a key modulator of oxidative protein folding in cardiomyocytes and underscores its therapeutic potential for treating ischemic heart disease.

Quantifying Microvascular Structure in Healthy and Infarcted Rat Hearts Using Optical Coherence Tomography Angiography.

Myocardial infarction (MI) is a life-threatening medical emergency resulting in coronary microvascular dysregulation and heart muscle damage. One of the primary characteristics of MI is capillary loss, which plays a significant role in the progression of this cardiovascular condition. In this study, we utilized optical coherence tomography angiography (OCTA) to image coronary microcirculation in fixed rat hearts, aiming to analyze coronary microvascular impairment post-infarction. Various angiographic metrics are presented to quantify vascular features, including the vessel area density, vessel complexity index, vessel tortuosity index, and flow impairment. Pathological differences identified from OCTA analysis are corroborated with histological analysis. The quantitative assessments reveal a significant decrease in microvascular density in the capillary-sized vessels and an enlargement for the arteriole/venule-sized vessels. Further, microvascular tortuosity and complexity exhibit an increase after myocardial infarction. The results underscore the feasibility of using OCTA to offer qualitative microvascular details and quantitative metrics, providing insights into coronary vascular network remodeling during disease progression and response to therapy.

Cardiac commitment driven by MyoD expression in pericardial stem cells.

Cellular therapy holds immense promise to remuscularize the damaged myocardium but is practically hindered by limited allogeneic sources of cardiac-committed cells that engraft stably in the recipient heart after transplantation. Here, we demonstrate that the pericardial tissue harbors myogenic stem cells (pSCs) that are activated in response to inflammatory signaling after myocardial infarction (MI). The pSCs derived from the MI rats (MI-pSCs) show in vivo and in vitro cardiac commitment characterized by cardiac-specific Tnnt2 expression and formation of rhythmic contraction in culture. Bulk RNA-seq analysis reveals significant upregulation of a panel of genes related to cardiac/myogenic differentiation, paracrine factors, and extracellular matrix in the activated pSCs compared to the control pSCs (Sham-pSCs). Notably, we define MyoD as a key factor that governs the process of cardiac commitment, as siRNA-mediated MyoD gene silencing results in a significant reduction of myogenic potential. Injection of the cardiac-committed cells into the infarcted rat heart leads to long-term survival and stable engraftment in the recipient myocardium. Therefore, these findings point to pericardial myogenic progenitors as an attractive candidate for cardiac cell-based therapy to remuscularize the damaged myocardium.

Methotrexate associated with nanoparticles decreases NLRC4 inflammasome expression in infarcted rat hearts

Abstract Abstract: Following myocardial infarction (MI), molecules released from necrotic myocytes sensitize nucleotide-binding receptors (NLRs), activate inflammasome complex, and initiate acute inflammatory process and interleukin (IL)-1β production, essential for tissue damage resolution. However, excessive IL-1β production impairs cardiac remodeling. After MI, IL-1β is released by the NLRP3 inflammasome; involvement of the NLRC4 inflammasome in post-MI remodeling has not been established. Methotrexate (MTX) carried by lipid core nanoparticles in low density emulsion (MTX-LDE) reduces post-MI inflammatory process and improves cardiac function in rodents. Purpose To evaluate the influence of early treatment with MTX-LDE on myocardial expression of NLRP3 and NLRC4 inflammasomes in infarcted rats. Methods Male Wistar rats were divided into three groups: control (Sham, n=6); MI (n=6); and MI treated with MTX-LDE (MI-MTX, n=6). MI was induced by ligation of the left anterior descending coronary artery. Twenty-four hours later, the MI-MTX group was treated with 1 mg/kg of MTX-LDE, intraperitoneally. Euthanasia was performed 72 hours after surgery under anaesthesia with ketamine and xylazine. Infarct size was assessed by histology. Myocardial expression of NLRC4, NLRP3, ASC, pro-caspase-1, caspase-1, pro-IL-1β and IL-1β was quantified by Western blotting. IL-1β concentration in serum and heart macerate supernatant was analyzed by ELISA. Statistical: ANOVA or Kruskal-Wallis; 5% significance level. Results Rats with MI lower than 30% of the left ventricle total area were excluded. Infarct size was larger in the MI-MTX group (43,8 ± 5,4) than MI (36,2 ± 6,22). NLRC4 and caspase-1 expression and IL-1β serum concentration were higher in MI than Sham and MI-MTX. Myocardial IL-1β concentration was higher in MI and MI-MTX than Sham and lower in MI-MTX than MI. NLRP3, ASC, pro-caspase-1, and IL-1β protein expression did not differ between groups. Conclusion Our study shows for the first time that NLRC4 inflammasome protein expression increases acutely after myocardial infarction in rats. Early treatment with nanoparticles-derived methotrexate reduces myocardial NLRC4 inflammasome expression and myocardial and serum IL-1β concentration.

Mature human induced pluripotent stem cell-derived cardiomyocytes promote angiogenesis through alpha-B crystallin

BackgroundHuman induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) can be used to treat heart diseases; however, the optimal maturity of hiPSC-CMs for effective regenerative medicine remains unclear. We aimed to investigate the benefits of long-term cultured mature hiPSC-CMs in injured rat hearts.MethodsCardiomyocytes were differentiated from hiPSCs via monolayer culturing, and the cells were harvested on day 28 or 56 (D28-CMs or D56-CMs, respectively) after differentiation. We transplanted D28-CMs or D56-CMs into the hearts of rat myocardial infarction models and examined cell retention and engraftment via in vivo bioluminescence imaging and histological analysis. We performed transcriptomic sequencing analysis to elucidate the genetic profiles before and after hiPSC-CM transplantation.ResultsUpregulated expression of mature sarcomere genes in vitro was observed in D56-CMs compared with D28-CMs. In vivo bioluminescence imaging studies revealed increased bioluminescence intensity of D56-CMs at 8 and 12 weeks post-transplantation. Histological and immunohistochemical analyses showed that D56-CMs promoted engraftment and maturation in the graft area at 12 weeks post-transplantation. Notably, D56-CMs consistently promoted microvessel formation in the graft area from 1 to 12 weeks post-transplantation. Transcriptomic sequencing analysis revealed that compared with the engrafted D28-CMs, the engrafted D56-CMs enriched genes related to blood vessel regulation at 12 weeks post-transplantation. As shown by transcriptomic and western blot analyses, the expression of a small heat shock protein, alpha-B crystallin (CRYAB), was significantly upregulated in D56-CMs compared with D28-CMs. Endothelial cell migration was inhibited by small interfering RNA-mediated knockdown of CRYAB when co-cultured with D56-CMs in vitro. Furthermore, CRYAB overexpression enhanced angiogenesis in the D28-CM grafts at 4 weeks post-transplantation.ConclusionsLong-term cultured mature hiPSC-CMs promoted engraftment, maturation and angiogenesis post-transplantation in infarcted rat hearts. CRYAB, which was highly expressed in D56-CMs, was identified as an angiogenic factor from mature hiPSC-CMs. This study revealed the benefits of long-term culture, which may enhance the therapeutic potential of hiPSC-CMs.

Stacking thick perfusable human microvascular grafts enables dense vascularity and rapid integration into infarcted rat hearts

Fabrication of large-scale engineered tissues requires extensive vascularization to support tissue survival and function. Here, we report a modular fabrication approach, by stacking of patterned collagen membranes, to generate thick (2 mm and beyond), large, three-dimensional, perfusable networks of endothelialized vasculature. In vitro, these perfusable vascular networks exhibit remodeling and evenly distributed perfusion among layers, while maintaining their patterned, open-lumen architecture. Compared to non-perfusable, self-assembled vasculature, constructs with perfusable vasculature demonstrated increased gene expression indicative of vascular development and angiogenesis. Upon implantation onto infarcted rat hearts, perfusable vascular networks attain greater host vascular integration than self-assembled controls, indicated by 2.5-fold greater perfused vascular density measured by histological analysis and 5-fold greater perfusion rate measured by optical microangiography. Together, the success of fabricating thick, perfusable tissues with dense vascularity and rapid anastomoses represents an important step forward for vascular bioengineering, and paves the way towards more complex, large scale, highly metabolic engineered tissues.

Rapamycin treatment unmasks a sex-specific pattern of scar expansion of the infarcted rat heart: The relationship between mTOR and KATP channel.

Inhibition of the mammalian target of rapamycin (mTOR) with the macrolide rapamycin or pharmacological suppression of KATP channel opening translated to scar expansion of the myocardial infarcted (MI) adult female rodent heart. The present study tested the hypotheses that rapamycin-mediated scar expansion was sex-specific and that mTOR signaling directly influenced KATP channel subunit expression/activity. Scar size was significantly larger in post-MI male rats as compared to the previous data reported in post-MI female rats. The reported scar expansion of rapamycin-treated post-MI female rats was not observed following the administration of the macrolide to post-MI male rats. Protein levels of the KATP channel subunits Kir6.2 and SUR2A and phosphorylation of the serine2448 residue of mTOR were similar in the normal heart of adult male and female rats. By contrast, greater tuberin inactivation characterized by the increased phosphorylation of the threonine1462 residue and reduced raptor protein levels were identified in the normal heart of adult female rats. Rapamycin pretreatment of phorbol 12,13-dibutyrate (PDBu)-treated neonatal rat ventricular cardiomyocytes (NNVMs) suppressed hypertrophy, inhibited p70S6K phosphorylation, and attenuated SUR2A protein upregulation. In the presence of low ATP levels, KATP channel activity detected in untreated NNVMs was significantly attenuated in PDBu-induced hypertrophied NNVMs via a rapamycin-independent pathway. Thus, rapamycin administration to post-MI rats unmasked a sex-specific pattern of scar expansion and mTOR signaling in PDBu-induced hypertrophied NNVMs significantly increased SUR2A protein levels. However, the biological advantage associated with SUR2A protein upregulation was partially offset by an mTOR-independent pathway that attenuated KATP channel activity in PDBu-induced hypertrophied NNVMs.

Effect of biomaterial stiffness on cardiac mechanics in a biventricular infarcted rat heart model with microstructural representation of in situ intramyocardial injectate.

Intramyocardial delivery of biomaterials is a promising concept for treating myocardial infarction. The delivered biomaterial provides mechanical support and attenuates wall thinning and elevated wall stress in the infarct region. This study aimed at developing a biventricular finite element model of an infarcted rat heart with a microstructural representation of an in situ biomaterial injectate, and a parametric investigation of the effect of the injectate stiffness on the cardiac mechanics. A three-dimensional subject-specific biventricular finite element model of a rat heart with left ventricular infarct and microstructurally dispersed biomaterial delivered 1 week after infarct induction was developed from ex vivo microcomputed tomography data. The volumetric mesh density varied between 303 mm-3 in the myocardium and 3852 mm-3 in the injectate region due to the microstructural intramyocardial dispersion. Parametric simulations were conducted with the injectate's elastic modulus varying from 4.1 to 405,900 kPa, and myocardial and injectate strains were recorded. With increasing injectate stiffness, the end-diastolic median myocardial fibre and cross-fibre strain decreased in magnitude from 3.6% to 1.1% and from -6.0% to -2.9%, respectively. At end-systole, the myocardial fibre and cross-fibre strain decreased in magnitude from -20.4% to -11.8% and from 6.5% to 4.6%, respectively. In the injectate, the maximum and minimum principal strains decreased in magnitude from 5.4% to 0.001% and from -5.4% to -0.001%, respectively, at end-diastole and from 38.5% to 0.06% and from -39.0% to -0.06%, respectively, at end-systole. With the microstructural injectate geometry, the developed subject-specific cardiac finite element model offers potential for extension to cellular injectates and in silico studies of mechanotransduction and therapeutic signalling in the infarcted heart with an infarct animal model extensively used in preclinical research.

Exosomes derived from mir-214-3p overexpressing mesenchymal stem cells promote myocardial repair

AimsExosomes are known as nanovesicles that are naturally secreted, playing an essential role in stem-mediated cardioprotection. This study mainly focused on investigating if exosomes derived from miR-214 overexpressing mesenchymal stem cells (MSCs) show more valid cardioprotective ability in a rat model of acute myocardial infarction (AMI) and its potential mechanisms.MethodsExosomes were isolated from control MSCs (Ctrl-Exo) and miR-214 overexpressing MSCs (miR-214OE-Exo) and then they were delivered to cardiomyocytes and endothelial cells in vitro under hypoxia and serum deprivation (H/SD) condition or in vivo in an acutely infarcted Sprague-Dawley rat heart. Regulated genes and signal pathways by miR-214OE-Exo treatment were explored using western blot analysis and luciferase assay.Results in vitro, miR-214OE-Exo enhanced migration, tube-like formation in endothelial cells. In addition, miR-214OE-Exo ameliorated the survival of cardiomyocytes under H/SD. In the rat AMI model, compared to Ctrl-Exo, miR-214OE-Exo reduced myocardial apoptosis, and therefore reduced infarct size and improved cardiac function. Besides, miR-214OE-Exo accelerated angiogenesis in peri-infarct region. Mechanistically, we identified that exosomal miR-214-3p promoted cardiac repair via targeting PTEN and activating p-AKT signal pathway.ConclusionExosomes derived from miR-214 overexpressing MSCs have greatly strengthened the therapeutic efficacy for treatment of AMI by promoting cardiomyocyte survival and endothelial cell function.Graphical abstract

Cardiac injection of USSC boosts remuscularization of the infarcted heart by shaping the T-cell response

Regenerating the injured heart remains one of the most vexing challenges in cardiovascular medicine. Cell therapy has shown potential for treatment of myocardial infarction, but low cell retention so far has limited its success. Here we show that intramyocardial injection of highly apoptosis-resistant unrestricted somatic stem cells (USSC) into infarcted rat hearts resulted in an unprecedented thickening of the left ventricular wall with cTnT+/BrdU+ cardiomyocytes that was paralleled by progressively restored ejection fraction. USSC induced significant T-cell enrichment in ischemic tissue with enhanced expression of T-cell related cytokines. Inhibition of T-cell activation by anti-CD28 monoclonal antibody, fully abolished the regenerative response which was restored by adoptive T-cell transfer. Secretome analysis of USSC and lineage tracing studies suggest that USSC secrete paracrine factors over an extended period of time which boosts a T-cell driven endogenous regenerative response mainly from adult cardiomyocytes.

Generation of mature compact ventricular cardiomyocytes from human pluripotent stem cells

Abstract Introduction Compact cardiomyocytes that make up the ventricular wall of the adult heart represent an important therapeutic target population for modeling and treating cardiovascular diseases. Although human pluripotent stem cell (hPSC) represents a promising source to generate target cells in vitro, there has been no optimal protocols to generate mature compact cardiomyocytes derived from hPSCs. Purpose To establish the protocol to generate mature compact ventricular cardiomyocytes derived from hPSCs. Methods By mimicking the early ventricular development and postnatal maturation process observed in the heart in vivo, we searched for the specific factors to induce compact lineage and promote their maturation level. Results We established a differentiation strategy that promotes the specification, proliferation and maturation of compact ventricular cardiomyocytes from hPSCs. The treatment of Wnt signaling activator, CHIR, and IGF2 significantly increased the expression level of a compact marker, MYCN (p=0.006), and suppressed the trabecular markers, NPPA (p=0.0117) and BMP10 (p=0.0032). Those factors induced a proliferation of compact cardiomyocytes by two folds (p&amp;lt;0.0001). Additionally, we identified that the combination of PPARα agonist, dexamethasone, T3 hormone, and palmitate in the low glucose containing media following the compact specification period significantly induced the fatty acid transporter, CD36, in the compact cardiomyocytes (p&amp;lt;0.0001). The CD36-positive compact cardiomyocytes generated under these conditions displayed the ability to use fatty acids as an energy source, a high mitochondrial mass, well-defined sarcomere structures and enhanced contraction force. These mature compact cardiomyocytes showed metabolic changes indicative of those associated with heart failure when challenged in vitro with pathological stimuli and were found to generate grafts consisting of more mature cells than those derived from immature cardiomyocytes following transplantation into infarcted rat hearts. Conclusions We successfully generated the mature compact cardiomyocytes derived from hPSCs. These findings highlight the power of recapitulating key aspects of embryonic and postnatal development for generating therapeutically relevant cell types from hPSCs. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Canadian Institutes of Health Research (CIHR)

Influence of the SGLT2 inhibitor empagliflozin on post myocardial infarction rat hearts

Abstract Studies have shown that inhibition of the sodium glucose transporter protein 2 (SGLT2) reduces cardiovascular death in patients with heart failure and reduced ejection fraction. However, the mechanisms involved in the benefits of SGLT2 inhibitors are poorly understood. Objective To evaluate the effects of empagliflozin (EMP) on normal and post-myocardial infarction (MI) rat hearts. Methods Male Wistar rats (n=80) were assigned into four groups: Sham; Sham treated with EMP (Sham-EMP); myocardial infarction (MI); and MI treated with EMP (MI-EMP). EMP added to rat chow (5 mg/kg/day) was initiated 10 days after MI induction and maintained for 12 weeks. Echocardiogram was performed at the end of the experimental period. Markers of oxidative stress, energy metabolism, and respiratory complex activity were analyzed in left ventricular myocardium. Statistical analysis: ANOVA. Results Histological evaluation showed that EMP did not change infarct size. Cardiac structural and functional parameters did not differ between MI-EMP and MI groups. Myocardial oxidative stress, evaluated by lipid hydroperoxide concentration, was lower in MI-EMP than MI group (Sham 143±26; Sham-EMP 123±20; MI 183±29; MI-EMP 137±11 nmol/g tissue). Glutathione peroxidase was lower in the infarcted groups and did not differ between MI-EMP and MI (Sham 37.6±6.14; Sham-EMP 40.8±10.1; MI 27.7±6.61; MI-EMP 26.5±6.80 μmol/g tissue). Activity of the energy metabolism enzymes lactate dehydrogenase (Sham 45.2±6.65; Sham-EMP 41.1±9.33; MI 58.4±14.4; MI-EMP 55.7±10.1 nmol/mg protein) and citrate synthase (Sham 30.4±4.25; Sham-EMP 37.2±4.85; MI 45.8±8.47; MI-EMP 46.5±9.95 nmol/mg protein) was higher, and β-hydroxyacyl-CoA dehydrogenase (Sham 24.0±3.12; Sham-EMP 20.4±4.84; MI 16.9±4.81; MI-EMP 14.4±4.58 nmol/mg protein) lower in the infarcted groups with no differences between MI-EMP and MI. Respiratory complexes I and II, and ATP synthase did not differ between the infarcted groups. Conclusion Empagliflozin reduces myocardial oxidative stress independent of changes in antioxidant enzymes activity, energy metabolism, and respiratory complex activity in the myocardium of infarcted rats. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Fapesp, CNPq

Effect of Low Level Laser Irradiation Preconditioning On Infarct Size and Ventricular Remodeling in the Rat Heart

Objectives: To investigate the effects of Low level laser irradiation (LLLI) preconditioning on the infarct size and ventricular remodeling in the rat heart. Background: LLLI can reduce the inflammatory reaction, attenuate the infarct size and formation of scar tissue, promote cardiomyocyte proliferation in the rat heart after myocardial infarction (MI). The effects of LLLI preconditioning on myocardium in the infarcted rat heart were rarely reported. Greater understanding of LLLI’s underlying photobiomodulative mechnisms would be helpful in translating photobiomodulation (PBM) therapy into the clinic. Methods: 3 days before establishing the model of rat MI, the LLLI was applied for the heart through the intercostal muscles in the chest in the LLLI group. The models of rat MI were induced by ligation of the left anterior descending coronary artery (LAD). At 4 weeks post MI, the hearts were harvested for histological analysis to determine the infarct size , the left ventricular wall thickness and the percentage of collagen fibers in the infarcted area. Results: In laser preconditioning group, the infarct size reduced significantly (15±9% to 35±10%, p&lt;0.05), the left ventricular wall thickness increased (0.64±0.0 2mm to 0.31±0.0 3mm, p&lt;0.05) and the percentage of collagen fibers in the infarcted area attenuated (35.67±2. 40% to 64.34±2. 20%) than that in the control group. Conclusion: LLLI preconditioning could markedly attenuate infact size formation, increase ventricular wall thickness and attenuate the formation of collagen fibers. LLLI has benefits on improving ventricular remodeling after MI. This found may have an important beneficial effect on preventing ischemic heart disease.

IFN-γ enhances the efficacy of mesenchymal stromal cell-derived exosomes via miR-21 in myocardial infarction rats

BackgroundMesenchymal stromal cells (MSCs) activated with IFN-γ elicit stronger physical effects. Exosomes (Exos) secreted from MSCs show protective effects against myocardial injury. This study aimed to determine whether Exos derived from IFN-γ-treated MSCs exhibit more potent cardioprotective function and the underlying mechanisms.MethodsH9c2 cells or human umbilical vein endothelial cells (HUVECs) were treated with Exos isolated from MSCs (Ctrl-Exo) or IFN-γ-primed MSCs (IFN-γ-Exo) under oxygen and glucose deprivation (OGD) conditions in vitro and in vivo in an infarcted rat heart. RNA sequencing was used to identify differentially expressed functional transcription factors (TFs). Quantitative reverse transcription-PCR (qPCR) was used to confirm the upregulated TFs and miRNA in IFN-γ-primed MSCs. Dual-luciferase reporter gene assay was used to analyze the transcriptional regulation of miRNAs by STAT1. The target of miR-21-5p (miR-21) was determined by luciferase reporter assays and qPCR. The function of BTG2 was verified in vitro under OGD conditions.ResultIFN-γ-Exo accelerated migration and tube-like structure formation and prevented OGD-induced apoptosis in H9c2. Similarly, IFN-γ-Exo treatment caused a decrease in fibrosis, reduced cardiomyocyte apoptosis, and improved cardiac function compared to Ctrl-Exo treatment. MiR-21 was significantly upregulated in IFN-γ-primed MSCs and IFN-γ-Exo. STAT1 transcriptionally induced miR-21 expression. Up-regulated miR-21 could inhibit BTG anti-proliferation factor 2 (BTG2) expressions. BTG2 promoted H9c2 cell apoptosis and reversed the protective effects of miR-21 under OGD conditions.ConclusionIFN-γ-Exo showed enhanced therapeutic efficacy against acute MI, possibly by promoting angiogenesis and reducing apoptosis by upregulating miR-21, which directly targeted BTG2.

Mesenchymal stem cells encapsulated in a reactive oxygen species-scavenging and O2-generating injectable hydrogel for myocardial infarction treatment

Stem cell especially mesenchymal stem cell (MSC) transplantation is a promising therapeutic strategy for myocardial infarction (MI) repair. However, major obstacles remain due to the poor retention and survival rate of transplanted MSCs in the harmful MI microenvironment (e.g., oxidative stress and hypoxia). Here, a novel injectable hydrogel (RCGel) with dual functions of reactive oxygen species (ROS)-scavenging and O2-generating was employed to encapsulate MSCs for MI treatment. The RCGel encapsulating exhibited anti-ROS protection through inhibiting JNK/p38 apoptosis signaling pathway to improve the viability of MSCs under oxidative stress conditions in vitro. The survival of cardiomyocytes was also improved both in the oxidative stress and hypoxia environments when being co-cultured with MSCs-encapsulated RCGel (MSC/RCGel). The RCGel encapsulating boosted the engraftment of transplanted MSCs in vivo. More viable MSCs endowed with regenerative abilities in the infarcted rat heart along with the ameliorated MI microenvironment (decreased oxidative stress and hypoxia) by the RCGel substantially inhibited cardiac apoptosis, enhanced cardiomyocyte viability, promoted angiogenesis and reduced fibrosis to improve the cardiac functions. The encapsulation of MSCs in RCGel, which exhibits beneficial effects in resisting harsh environments, provides a new way in MI repair and stem cell delivery, and has great potential in cell-based regenerative medicine.

Differential effects of EPA and DHA on PPARγ-mediated sympathetic innervation in infarcted rat hearts by GPR120-dependent and -independent mechanisms

The ω-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to attenuate inflammation processes, whereas the molecular mechanisms remain unclear. This study was aimed at figuring out the differential effects of EPA and DHA on fatal arrhythmias and whether the signaling pathway could be a target after myocardial infarction, an inflammatory status. Male Wistar rats after ligating coronary artery were randomized to either vehicle, EPA, or DHA for 4 weeks. Postinfarction was associated with increased myocardial norepinephrine levels and sympathetic innervation. Furthermore, infarction was associated with the activation of NLRP3 inflammasomes and increased the protein and expression of IL-1β and nerve growth factor (NGF). These changes were blunted after adding either EPA or DHA with a greater extent of EPA than DHA. Immunoblotting and immunohistochemical analysis showed that EPA had significantly lower phosphorylation of PPARγ at Ser 112 compared with DHA. Arrhythmic severity during programmed stimulation in the infarcted rats treated with EPA was significantly lower than those treated with DHA. Specific inhibition of GPR120 by AH-7614 and PPARγ by T0070907 reduced the EPA-or DHA-related attenuation of IL-1β and NGF release. Besides, AH-7614 treatment partially reduced the PPARγ levels, whereas T0070907 administration did not affect the GPR120 levels. These results suggest that EPA was more effective than DHA in prevention of fatal arrhythmias by inhibiting NLRP3 inflammasome and sympathetic innervation through activation of PPARγ-mediated GPR120-dependent and -independent signaling pathways in infarcted hearts.

Electrical activity in exercise trained infarcted rat hearts

Myocardial infarction (MI) is a major cause of cardiac arrhythmias. The aim of the study was to determine if exercise training changes the electrical conduction into, within and emerging from an infarcted area of a rat heart. Rats were divided into three groups: sedentary sham, sedentary MI, and exercise training MI. The impact of MI and exercise training on susceptibility to ventricular tachycardias (VTs) was evaluated by in vivo intra-cardiac pacing. Rats with sustained VTs were converted before sacrifice and electrophysiological experiments and optical imaging with voltage-sensitive dye were performed on perfused hearts.

Improved myocardial performance in infarcted rat heart by injection of disulfide-cross-linked chitosan hydrogels loaded with basic fibroblast growth factor.

Myocardial infarction (MI) has been considered as the leading cause of cardiovascular-related deaths worldwide. Basic fibroblast growth factor (bFGF) is a member of the fibroblast growth factor family that promotes angiogenesis after MI; however, it has poor clinical efficacy due to proteolytic degradation, low drug accumulation, and severe drug-induced side effects. In this study, an injectable disulfide-cross-linked chitosan hydrogel loaded with bFGF was prepared via a thiol-disulfide exchange reaction for MI treatment. The thiol-disulfide exchange reaction between pyridyl disulfide-modified carboxymethyl chitosan (CMCS-S-S-Py) and reduced BSA (rBSA) was carried out under physiological conditions (37 °C and pH 7.4). The mechanical properties of the disulfide-cross-linked chitosan hydrogel were evaluated based on the molar ratio of the pyridyl disulfide groups of CMCS-S-S-Py and the thiol groups of rBSA. The disulfide-cross-linked chitosan hydrogel showed good swelling performance, rapid glutathione-triggered degradation behavior and well-defined cell proliferation towards NIH 3T3 fibroblast cells. In the process of establishing a rat MI model, the squeezing heart method was used to make the operation more accurate and the mortality of rats was decreased by using a ventilator. The disulfide-cross-linked chitosan hydrogel loaded with bFGF (bFGF-hydrogel) was injected into a peri-infarcted area of cardiac tissue immediately following MI. Echocardiography demonstrated that the left ventricular functions were improved by the bFGF-hydrogel after 28 days of treatment. Histological results revealed that the hydrogel significantly reduced the fibrotic area of MI, and this was further improved by the bFGF-hydrogel treatment. TUNEL and immunohistochemical staining results showed that the bFGF-hydrogel had a more synergistic effect on antiapoptosis and proangiogenesis than using either bFGF or the hydrogel alone.

Amniotic stromal stem cell-loaded hydrogel repairs cardiac tissue in infarcted rat hearts via paracrine mediators.

The use of stem cells to repair the heart after a myocardial infarction (MI) remains promising, yet clinical trials over the past 20years suggest that cells fail to integrate into the native tissue, resulting in limited improvements in cardiac function. Here, we demonstrate the cardioprotective potential of a composite inserting human amniotic stromal mesenchymal stem cells (ASMCs) in a chitosan and hyaluronic acid (C/HA) based hydrogel in a rat MI model. Mechanical characterization of the C/HA platform indicated a swift elastic conversion at 40°C and a rapid sol-gel transition time at 37°C. Cell viability assay presented active and proliferating AMSCs in the C/HA. The ASMCs+C/HA injected composite significantly increased left ventricular ejection fraction, fractional shortening, and neovessel formation. The encapsulated AMSCs were abundantly detected in the infarcted myocardium 6weeks post-administration and co-expressed cardiac proteins and notably proliferative markers. Proteomic profiling revealed that extracellular vesicles released from hypoxia preconditioned ASMCs contained proteins involved in cytoprotection, angiogenesis, cardiac differentiation and non-canonical Wnt-signaling. Independent activation of non-canonical Wnt-signaling pathways in ASMCs induced cardiogenesis. Despite a low injected cellular density at baseline, the encapsulated AMSCs were abundantly retained and increased cardiac function. Furthermore, the C/HA hydrogel provided an active milieu for the AMSCs to proliferate, co-express cardiac proteins, and induce new vessel formation. Hence, this novel composite of AMSCs+C/HA scaffold is a conceivable candidate that could restore cardiac function and reduce remodeling.