Interleukin‐38 alleviates cardiac remodelling after myocardial infarction

Excessive immune‐mediated inflammatory reaction plays a deleterious role in ventricular remodelling after myocardial infarction (MI). Interleukin (IL)‐38 is a newly characterized cytokine of the IL‐1 family and has been reported to exert a protective effect in some autoimmune diseases. However, its role in cardiac remodelling post‐MI remains unknown. In this study, we found that the expression of IL‐38 was increased in infarcted heart after MI induced in C57BL/6 mice by permanent ligation of the left anterior descending artery. In addition, our data showed that ventricular remodelling after MI was significantly ameliorated after recombinant IL‐38 injection in mice. This amelioration was demonstrated by better cardiac function, restricted inflammatory response, attenuated myocardial injury and decreased myocardial fibrosis. Our results in vitro revealed that IL‐38 affects the phenotype of dendritic cells (DCs) and IL‐38 plus troponin I (TNI)‐treated tolerogenic DCs dampened adaptive immune response when co‐cultured with CD4⁺T cells. In conclusion, IL‐38 plays a protective effect in ventricular remodelling post‐MI, one possibility by influencing DCs to attenuate inflammatory response. Therefore, targeting IL‐38 may hold a new therapeutic potential in treating MI.     

Ultrasound combined with SDF‐1α chemotactic microbubbles promotes stem cell homing in an osteoarthritis model

Osteoarthritis (OA) is a common joint disease in the middle and old age group with obvious cartilage damage, and the regeneration of cartilage is the key to alleviating or treating OA. In stem cell therapy, bone marrow stem cell (BMSC) has been confirmed to have cartilage regeneration ability. However, the role of stem cells in promoting articular cartilage regeneration is severely limited by their low homing rate. Stromal cell‐derived factor‐1α (SDF‐1α) plays a vital role in MSC migration and involves activation, mobilization, homing and retention. So, we aim to develop SDF‐1α‐loaded microbubbles MB(SDF‐1α), and to verify the migration of BMSCs with the effect of ultrasound combined with MB(SDF‐1α) in vitro and in vivo. The characteristics of microbubbles and the content of SDF‐1α were examined in vitro. To evaluate the effect of ultrasound combined with chemotactic microbubbles on stem cell migration, BMSCs were injected locally and intravenously into the knee joint of the OA model, and the markers of BMSCs in the cartilage were detected. We successfully prepared MB(SDF‐1α) through covalent bonding with impressive SDF‐1α loading efficacy loading content. In vitro study, ultrasound combined with MB(SDF‐1α) group can promote more stem cell migration with highest migrating cell counts, good cell viability and highest CXCR4 expression. In vivo experiment, more BMSCs surface markers presented in the ultrasound combined with MB(SDF‐1α) group with or without exogenous BMSCs administration. Hence, ultrasound combined with MB(SDF‐1α) could promote the homing of BMSCs to cartilage and provide a novel promising therapeutic approach for OA.     

Intramyocardial transplantation of cardiac telocytes decreases myocardial infarction and improves post‐infarcted cardiac function in rats

The midterm effects of cardiac telocytes (CTs) transplantation on myocardial infarction (MI) and the cellular mechanisms involved in the beneficial effects of CTs transplantation are not understood. In the present study, we have revealed that transplantation of CTs was able to significantly decrease the infarct size and improved cardiac function 14 weeks after MI. It has established that CT transplantation exerted a protective effect on the myocardium and this was maintained for at least 14 weeks. The cellular mechanism behind this beneficial effect on MI was partially attributed to increased cardiac angiogenesis, improved reconstruction of the CT network and decreased myocardial fibrosis. These combined effects decreased the infarct size, improved the reconstruction of the LV and enhanced myocardial function in MI. Our findings suggest that CTs could be considered as a potential cell source for therapeutic use to improve cardiac repair and function following MI, used either alone or in tandem with stem cells.     

Mitophagy‐regulated mitochondrial health strongly protects the heart against cardiac dysfunction after acute myocardial infarction

Autophagy including mitophagy serves as an important regulatory mechanism in the heart to maintain the cellular homeostasis and to protect against heart damages caused by myocardial infarction (MI). The current study aims to dissect roles of general autophagy and specific mitophagy in regulating cardiac function after MI. By using Beclin1^+/−, Fundc1 knockout (KO) and Fundc1 transgenic (TG) mouse models, combined with starvation and MI models, we found that Fundc1 KO caused more severe mitochondrial and cardiac dysfunction damages than Beclin1^+/− after MI. Interestingly, Beclin1^+/− caused notable decrease of total autophagy without detectable change to mitophagy, and Fundc1 KO markedly suppressed mitophagy but did not change the total autophagy activity. In contrast, starvation increased total autophagy without changing mitophagy while Fundc1 TG elevated total autophagy and mitophagy in mouse hearts. As a result, Fundc1 TG provided much stronger protective effects than starvation after MI. Moreover, Beclin1^+/−/Fundc1 TG showed increased total autophagy and mitophagy to a level comparable to Fundc1 TG per se, and completely reversed Beclin1^+/−‐caused aggravation of mitochondrial and cardiac injury after MI. Our results reveal that mitophagy but not general autophagy contributes predominantly to the cardiac protective effect through regulating mitochondrial function.     

Transplantation of expanded bone marrow‐derived very small embryonic‐like stem cells (VSEL‐SCs) improves left ventricular function and remodelling after myocardial infarction

Adult bone marrow‐derived very small embryonic‐like stem cells (VSEL‐SCs) exhibit a Sca‐1⁺/Lin^–/CD45^– phenotype and can differentiate into various cell types, including cardiomyocytes and endothelial cells. We have previously reported that transplantation of a small number (1 × 10⁶) of freshly isolated, non‐expanded VSEL‐SCs into infarcted mouse hearts resulted in improved left ventricular (LV) function and anatomy. Clinical translation, however, will require large numbers of cells. Because the frequency of VSEL‐SCs in the marrow is very low, we examined whether VSEL‐SCs can be expanded in culture without loss of therapeutic efficacy. Mice underwent a 30 min. coronary occlusion followed by reperfusion and, 48 hrs later, received an intramyocardial injection of vehicle (group I, n= 11), 1 × 10⁵ enhanced green fluorescent protein (EGFP)‐labelled expanded untreated VSEL‐SCs (group II, n= 7), or 1 × 10⁵ EGFP‐labelled expanded VSEL‐SCs pre‐incubated in a cardiogenic medium (group III, n= 8). At 35 days after myocardial infarction (MI), mice treated with pre‐incubated VSEL‐SCs exhibited better global and regional LV systolic function and less LV hypertrophy compared with vehicle‐treated controls. In contrast, transplantation of expanded but untreated VSEL‐SCs did not produce appreciable reparative benefits. Scattered EGFP⁺ cells expressing α‐sarcomeric actin, platelet endothelial cell adhesion molecule (PECAM)‐1, or von Willebrand factor were present in VSEL‐SC‐treated mice, but their numbers were very small. No tumour formation was observed. We conclude that VSEL‐SCs expanded in culture retain the ability to alleviate LV dysfunction and remodelling after a reperfused MI provided that they are exposed to a combination of cardiomyogenic growth factors and cytokines prior to transplantation. Counter intuitively, the mechanism whereby such pre‐incubation confers therapeutic efficacy does not involve differentiation into new cardiac cells. These results support the potential therapeutic utility of VSEL‐SCs for cardiac repair.     

Novel mechanism of cardiac protection by valsartan: synergetic roles of TGF‐β1 and HIF‐1α in Ang II‐mediated fibrosis after myocardial infarction

Transforming growth factor (TGF)‐β1 is a known factor in angiotensin II (Ang II)‐mediated cardiac fibrosis after myocardial infarction (MI). Hypoxia inducible factor‐1 (Hif‐1α) was recently demonstrated to involve in the tissue fibrosis and influenced by Ang II. However, whether Hif‐1α contributed to the Ang II‐mediated cardiac fibrosis after MI, and whether interaction or synergetic roles between Hif‐1α and TGF‐β pathways existed in the process was unclear. In vitro, cardiac cells were incubated under hypoxia or Ang II to mimic ischaemia. In vivo, valsartan was intravenously injected into Sprague–Dawley rats with MI daily for 1 week; saline and hydralazine (another anti‐hypertensive agent like valsartan) was used as control. The fibrosis‐related proteins were detected by Western blotting. Cardiac structure and function were assessed with multimodality methods. We demonstrated in vitro that hypoxia would induce the up‐regulation of Ang II, TGF‐β/Smad and Hif‐1α, which further induced collagen accumulation. By blocking with valsartan, a blocker of Ang II type I (AT1) receptor, we confirmed that the up‐regulation of TGF‐β/Smad and Hif‐1α was through the Ang II‐mediated pathway. By administering TGF‐β or dimethyloxalylglycine, we determined that both TGF‐β/Smad and Hif‐1α contributed to Ang II‐mediated collagen accumulation and a synergetic effect between them was observed. Consistent with in vitro results, valsartan significantly attenuated the expression of TGF‐β/Smad, Hif‐1α and fibrosis‐related protein in rats after MI. Heart function, infarcted size, wall thickness as well as myocardial vascularization of ischaemic hearts were also significantly improved by valsartan compared with saline and hydralazine. Our study may provide novel insights into the mechanisms of Ang II‐induced cardiac fibrosis as well as into the cardiac protection of valsartan.     

C-反应蛋白在不同程度急性心梗患者中的相关性研究

目的：探讨C-反应蛋白（CRP）在急性心肌梗死患者中的变化及与心功能之间的关系。方法：选取121例急性心肌梗死（AMI）患者和50例健康对照者,酶联免疫吸附法（ELISA）检测血清C-反应蛋白（CRP）和B型钠尿肽（BNP）。结果：AMI患者血清CRP显著高于健康对照,AMI伴心功能III,IV级者血清BNP、CRP显著高于AMI伴心功能I,II级者。结论：血清CRP对于急性心肌梗死患者的心功能重要参考指标。     

Knock‐out of MicroRNA 145 impairs cardiac fibroblast function and wound healing post‐myocardial infarction

Prevention of infarct scar thinning and dilatation and stimulation of scar contracture can prevent progressive heart failure. Since microRNA 145 (miR‐145) plays an important role in cardiac fibroblast response to wound healing and cardiac repair after an myocardial infarction (MI), using a miR‐145 knock‐out (KO) mouse model, we evaluated contribution of down‐regulation of miR‐145 to cardiac fibroblast and myofibroblast function during adverse cardiac remodelling. Cardiac function decreased more and the infarct size was larger in miR‐145 KO than that in WT mice after MI and this phenomenon was accompanied by a decrease in cardiac fibroblast‐to‐myofibroblast differentiation. Quantification of collagen I and α‐SMA protein levels as well as wound contraction revealed that transdifferentiation of cardiac fibroblasts into myofibroblasts was lower in KO than WT mice. In vitro restoration of miR‐145 induced more differentiation of fibroblasts to myofibroblasts and this effect involved the target genes Klf4 and myocardin. MiR‐145 contributes to infarct scar contraction in the heart and the absence of miR‐145 contributes to dysfunction of cardiac fibroblast, resulting in greater infarct thinning and dilatation. Augmentation of miR‐145 could be an attractive target to prevent adverse cardiac remodelling after MI by enhancing the phenotypic switch of cardiac fibroblasts to myofibroblasts.     

C - 反应蛋白在不同程度急性心梗患者中的相关性研究

目的:探讨C-反应蛋白(CRP)在急性心肌梗死患者中的变化及与心功能之间的关系。方法:选取121例急性心肌梗死(AMI)患者和50例健康对照者,酶联免疫吸附法(ELISA)检测血清C-反应蛋白(CRP)和B型钠尿肽(BNP)。结果:AMI患者血清CRP显著高于健康对照,AMI伴心功能III,IV级者血清BNP、CRP显著高于AMI伴心功能I,II级者。结论:血清CRP对于急性心肌梗死患者的心功能重要参考指标。     

miR‐499 released during myocardial infarction causes endothelial injury by targeting α7‐nAchR

The surged systemic vascular inflammation after acute myocardial infarction (AMI) aggravates the atherosclerotic endothelial injury. To explore roles of miR‐499 released from cardiomyocytes during AMI in endothelial injury. Using qPCR and ELISA, we discovered that patients with AMI had significantly increased plasma miR‐499, which was directly correlated with serum thrombomodulin, a marker for endothelial injury. Plasma of AMI patients, when incubated with human umbilical vein endothelial cells (HUVECs), significantly increased the expression of endothelial injury markers, which could be abrogated by antagomiR‐499. In vitro, neonatal rat cardiomyocytes subjected to hypoxia/reoxygenation (HX/R) released miR‐499 that could be internalized into rat pulmonary microvascular endothelial cells (RPMECs), worsening the high glucose‐induced injury. In silico analysis demonstrated that CHRNA7 encoding α7‐nAchR is a target of miR‐499, which was validated in cell lines expressing endogenous α7‐nAchR. In high glucose‐induced RPMECs injury model, miR‐499 aggravated, whereas forced CHRNA7 expression ameliorated the injury. Moreover, the perfusate from Langendorff perfused rat heart subjected to HX/R contained higher level of miR‐499 that significantly impaired the Bradykinin‐mediated endothelium‐dependent relaxation in both conduit and resistance arteries, which could be partially abrogated by antagomiR‐499. Finally, the correlation between plasma miR‐499 and endothelial injury was further confirmed in another cohort of AMI patients. We conclude that miR‐499 released from injured cardiomyocytes contributes to the endothelial injury by targeting α7‐nAchR. This study implies that miR‐499 may serve as a potential target for the treatment of the surged vascular inflammation post‐AMI.     

Protective role of 5‐azacytidine on myocardial infarction is associated with modulation of macrophage phenotype and inhibition of fibrosis

We examined whether a shift in macrophage phenotype could be therapeutic for myocardial infarction (MI). The mouse macrophage cell line RAW264.7 was stimulated with peptidoglycan (PGN), with or without 5-azacytidine (5AZ) treatment. MI was induced by ligation of the left anterior descending coronary artery in rats, and the rats were divided into two groups; a saline-injection group and a 5AZ-injection group (2.5 mg/kg/day, intraperitoneal injection). LV function was evaluated and immunohistochemical analyses were performed 2 weeks after MI. Cardiac fibrosis was induced by angiotensin II (AngII) infusion with or without 5AZ (5 mg/kg/day) in mice. Nitric oxide was produced by PGN, which was reduced by 77.87% after 5AZ treatment. Both induction of inducible nitric oxide synthase (iNOS) and iNOS promoter activity by PGN were inhibited by 5AZ. Ejection fraction (59.00 ± 8.03% versus 42.52 ± 2.58%), contractility (LV dP/dt-max, 8299.76 ± 411.56 mmHg versus 6610.36 ± 282.37 mmHg) and relaxation indices (LV dP/dt-min, −4661.37 ± 210.73 mmHg versus −4219.50 ± 162.98 mmHg) were improved after 5AZ administration. Cardiac fibrosis in the MI+5AZ was 8.14 ± 1.00%, compared with 14.93 ± 2.98% in the MI group (P < 0.05). Arginase-1(+)CD68(+) macrophages with anti-inflammatory phenotype were predominant in the infarct border zone of the MI+5AZ group, in comparison with the MI group. AngII-induced cardiac fibrosis was also attenuated after 5AZ administration. In cardiac fibroblasts, pro-fibrotic mediators and cell proliferation were increased by AngII, and these increases were attenuated after 5AZ treatment. 5AZ exerts its cardiac protective role through modulation of macrophages and cardiac fibroblasts.     

Silencing of ATP2B1‐AS1 contributes to protection against myocardial infarction in mouse via blocking NFKBIA‐mediated NF‐κB signalling pathway

Myocardial infarction (MI) is an acute coronary syndrome that refers to tissue infarction of the myocardium. This study aimed to investigate the effect of long intergenic non‐protein‐coding RNA (lincRNA) ATPase plasma membrane Ca²⁺ transporting 1 antisense RNA 1 (ATP2B1‐AS1) against MI by targeting nuclear factor‐kappa‐B inhibitor alpha (NFKBIA) and mediating the nuclear factor‐kappa‐B (NF‐κB) signalling pathway. An MI mouse model was established and idenepsied by cardiac function evaluation. It was determined that ATP2B1‐AS1 was highly expressed, while NFKBIA was poorly expressed and NF‐κB signalling pathway was activated in MI mice. Cardiomyocytes were extracted from mice and introduced with a series of mouse ATP2B1‐AS1 vector, NFKBIA vector, siRNA‐mouse ATP2B1‐AS1 and siRNA‐NFKBIA. The expression of NF‐κBp50, NF‐κBp65 and IKKβ was determined to idenepsy whether ATP2B1‐AS1 and NFKBIA affect the NF‐κB signalling pathway, the results of which suggested that ATP2B1‐AS1 down‐regulated the expression of NFKBIA and activated the NF‐κB signalling pathway in MI mice. Based on the data from assessment of cell viability, cell cycle, apoptosis and levels of inflammatory cytokines, either silencing of mouse ATP2B1‐AS1 or overexpression of NFKBIA was suggested to result in reduced cardiomyocyte apoptosis and expression of inflammatory cytokines, as well as enhanced cardiomyocyte viability. Our study provided evidence that mouse ATP2B1‐AS1 silencing may have the potency to protect against MI in mice through inhibiting cardiomyocyte apoptosis and inflammation, highlighting a great promise as a novel therapeutic target for MI.     

Injectable biodegradable hydrogels for embryonic stem cell transplantation: improved cardiac remodelling and function of myocardial infarction

In this study, an injectable, biodegradable hydrogel composite of oligo[poly(ethylene glycol) fumarate] (OPF) was investigated as a carrier of mouse embryonic stem cells (mESCs) for the treatment of myocardial infarction (MI). The OPF hydrogels were used to encapsulate mESCs. The cell differentiation in vitro over 14 days was determined via immunohistochemical examination. Then, mESCs encapsulated in OPF hydrogels were injected into the LV wall of a rat MI model. Detailed histological analysis and echocardiography were used to determine the structural and functional consequences after 4 weeks of transplantation. With ascorbic acid induction, mESCs could differentiate into cardiomyocytes and other cell types in all three lineages in the OPF hydrogel. After transplantation, both the 24-hr cell retention and 4-week graft size were significantly greater in the OPF + ESC group than that of the PBS + ESC group (P < 0.01). Four weeks after transplantation, OPF hydrogel alone significantly reduced the infarct size and collagen deposition and improved the cardiac function. The heart function and revascularization improved significantly, while the infarct size and fibrotic area decreased significantly in the OPF + ESC group compared with that of the PBS + ESC, OPF and PBS groups (P < 0.01). All treatments had significantly reduced MMP2 and MMP9 protein levels compared to the PBS control group, and the OPF + ESC group decreased most by Western blotting. Transplanted mESCs expressed cardiovascular markers. This study suggests the potential of a method for heart regeneration involving OPF hydrogels for stem cell encapsulation and transplantation.     

Suppression of lysosomal-associated protein transmembrane 5 ameliorates cardiac function and inflammatory response by inhibiting the nuclear factor-kappa B (NF-κB) pathway after myocardial infarction in mice

Myocardial infarction (MI) as the remarkable presentation of coronary artery disease is still a reason for morbidity and mortality in worldwide. Lysosomal-associated protein transmembrane 5 (LAPTM5) is a lysosomal-related protein found in hematopoietic tissues and has been confirmed as a positive regulator of pro-inflammatory pathways in macrophages. However, the role of LAPTM5 in MI remains unknown. In this study, we found that both mRNA and protein expression levels of LAPTM5 were significantly elevated in MI mice. Suppression of LAPTM5 in myocardial tissues decreased cardiac fibrosis and improved cardiac function after MI. At the molecular level, downregulated LAPTM5 dramatically suppressed the macrophage activation and inflammatory response via inhibiting the activation of the nuclear factor-kappa B (NF-κB) pathway. Collectively, suppression of LAPTM5 in myocardial tissues inhibits the pro-inflammatory response and the cardiac dysfunction caused by MI. This study indicated that LAPTM5 as a pro-inflammatory factor plays a crucial role in MI disease.     

miR‐155‐5p inhibition rejuvenates aged mesenchymal stem cells and enhances cardioprotection following infarction

Aging impairs the functions of human mesenchymal stem cells (MSCs), thereby severely reducing their beneficial effects on myocardial infarction (MI). MicroRNAs (miRNAs) play crucial roles in regulating the senescence of MSCs; however, the underlying mechanisms remain unclear. Here, we investigated the significance of miR‐155‐5p in regulating MSC senescence and whether inhibition of miR‐155‐5p could rejuvenate aged MSCs (AMSCs) to enhance their therapeutic efficacy for MI. Young MSCs (YMSCs) and AMSCs were isolated from young and aged donors, respectively. The cellular senescence of MSCs was evaluated by senescence‐associated β‐galactosidase (SA‐β‐gal) staining. Compared with YMSCs, AMSCs exhibited increased cellular senescence as evidenced by increased SA‐β‐gal activity and decreased proliferative capacity and paracrine effects. The expression of miR‐155‐5p was much higher in both serum and MSCs from aged donors than young donors. Upregulation of miR‐155‐5p in YMSCs led to increased cellular senescence, whereas downregulation of miR‐155‐5p decreased AMSC senescence. Mechanistically, miR‐155‐5p inhibited mitochondrial fission and increased mitochondrial fusion in MSCs via the AMPK signaling pathway, thereby resulting in cellular senescence by repressing the expression of Cab39. These effects were partially reversed by treatment with AMPK activator or mitofusin2‐specific siRNA (Mfn2‐siRNA). By enhancing angiogenesis and promoting cell survival, transplantation of anti‐miR‐155‐5p‐AMSCs led to improved cardiac function in an aged mouse model of MI compared with transplantation of AMSCs. In summary, our study shows that miR‐155‐5p mediates MSC senescence by regulating the Cab39/AMPK signaling pathway and miR‐155‐5p is a novel target to rejuvenate AMSCs and enhance their cardioprotective effects.