Sympathetic hyperinnervation drives abdominal aortic aneurysm development by promoting vascular smooth muscle cell phenotypic switching.

INTRODUCTION: Sympathetic hyperinnervation plays an important role in modulating the vascular smooth muscle cell (VSMC) phenotype and vascular diseases, but its role in abdominal aortic aneurysm (AAA) is still unknown. OBJECTIVES: This study aimed to investigate the role of sympathetic hyperinnervation in promoting AAA development and the underlying mechanism involved. METHODS: Western blotting and immunochemical staining were used to detect sympathetic hyperinnervation. We performed sympathetic denervation through coeliac ganglionectomy (CGX) and 6-OHDA administration to understand the role of sympathetic hyperinnervation in AAA and investigated the underlying mechanisms through transcriptome and functional studies. Sema4D knockout (Sema4D-/-) mice were utilized to determine the involvement of Sema4D in inducing sympathetic hyperinnervation and AAA development. RESULTS: We observed sympathetic hyperinnervation, the most important form of sympathetic neural remodeling, in both mouse AAA models and AAA patients. Elimination of sympathetic hyperinnervation by CGX or 6-OHDA significantly inhibited AAA development and progression. We further revealed that sympathetic hyperinnervation promoted VSMC phenotypic switching in AAA by releasing extracellular ATP (eATP) and activating eATP-P2rx4-p38 signaling. Moreover, single-cell RNA sequencing revealed that Sema4D secreted by osteoclast-like cells induces sympathetic nerve diffusion and hyperinnervation through binding to Plxnb1. We consistently observed that AAA progression was significantly ameliorated in Sema4D-deficient mice. CONCLUSIONS: Sympathetic hyperinnervation driven by osteoclast-like cell-derived Sema4D promotes VSMC phenotypic switching and accelerates pathological aneurysm progression by activating the eATP/P2rx4/p38 pathway. Inhibition of sympathetic hyperinnervation emerges as a potential novel therapeutic strategy for preventing and treating AAA.

Optogenetic Stimulation of the Cardiac Vagus Nerve to Promote Heart Regenerative Repair after Myocardial Infarction.

Background: It had been shown that selective cardiac vagal activation holds great potential for heart regeneration. Optogenetics has clinical translation potential as a novel means of modulating targeted neurons. This study aimed to investigate whether cardiac vagal activation via optogenetics could improve heart regenerative repair after myocardial infarction (MI) and to identify the underlying mechanism. Methods: We used an adeno-associated virus (AAV) as the vector to deliver ChR2, a light-sensitive protein, to the left nodose ganglion (LNG). To assess the effects of the cardiac vagus nerve on cardiomyocyte (CM) proliferation and myocardial regeneration in vivo, the light-emitting diode illumination (470 nm) was applied for optogenetic stimulation to perform the gain-of-function experiment and the vagotomy was used as a loss-of-function assay. Finally, sequencing data and molecular biology experiments were analyzed to determine the possible mechanisms by which the cardiac vagus nerve affects myocardial regenerative repair after MI. Results: Absence of cardiac surface vagus nerve after MI was more common in adult hearts with low proliferative capacity, causing a poor prognosis. Gain- and loss-of-function experiments further demonstrated that optogenetic stimulation of the cardiac vagus nerve positively regulated cardiomyocyte (CM) proliferation and myocardial regeneration in vivo. More importantly, optogenetic stimulation attenuated ventricular remodeling and improved cardiac function after MI. Further analysis of sequencing results and flow cytometry revealed that cardiac vagal stimulation activated the IL-10/STAT3 pathway and promoted the polarization of cardiac macrophages to the M2 type, resulting in beneficial cardiac regenerative repair after MI. Conclusions: Targeting the cardiac vagus nerve by optogenetic stimulation induced macrophage M2 polarization by activating the IL-10/STAT3 signaling pathway, which obviously optimized the regenerative microenvironment and then improved cardiac function after MI.

Advanced drive laser system for a high-brightness continuous-wave photocathode electron gun.

In order to enhance the performance of a continuous-wave photocathode electron gun at Peking University, and to achieve electron beams with higher current and brightness, a multifunctional drive laser system named PULSE (Peking University drive Laser System for high-brightness Electron source) has been developed. This innovative system is capable of delivering an average output power of 120 W infrared laser pulse at 81.25 MHz, as well as approximately 13.8 W of green power with reliable stability. The utilization of two stages of photonic crystal fibers plays a crucial role in achieving this output. Additionally, the incorporation of two acousto-optic modulators enables the selection of macro-pulses with varying repetition frequencies and duty cycles, which is essential for effective electron beam diagnosis. Furthermore, the system employs a series of birefringent crystals for temporal pulse shaping, allowing for stacking Gaussian pulses into multiple types of distribution. Overall, the optical schematic and operating performance of PULSE are detailed in this paper.

Tricuspid isthmus ablation with pulsed-field power by linear catheter: a case report.

Background: Pulsed-field ablation using annular or petal-shaped catheters had been proven to be effective for achieving electrical isolation of pulmonary veins in patients with atrial fibrillation. However, the utilization of linear pulse-field power for treating atrial flutter has yet to been documented. Case summary: In this report, we present a case involving the successful treatment of tricuspid isthmus-dependent atrial flutter treated with a linear pulsed-field catheter. The patient, a 71-year-old male, presents with an electrocardiogram indicating atrial flutter. Subsequent electrophysiological examination reveals typical atrial flutter that is dependent on the cavo-tricuspid isthmus (CTI). This condition is successfully terminated through the application of linear pulsed-field ablation. Discussion: This case represents a pioneering instance of CTI-dependent atrial flutter ablation utilizing linear pulse-field power. The innovative approach not only effectively treats the patient but also serves as a valuable reference for future applications of linear treatment with pulsed-field ablation.

Comparisons of procedural characteristics and clinical outcomes between SMARTTOUCH SURROUNDFLOW catheter and other catheters for atrial fibrillation radiofrequency catheter ablation: a systematic literature review.

BACKGROUND: SMARTTOUCH SURROUNDFLOW (STSF) catheter is the new generation of SMARTTOUCH (ST) catheter with an upgraded irrigation system for radiofrequency catheter ablation (RFCA) in patients with atrial fibrillation (AF). METHODS: This systematic literature review searched the major English and Chinese bibliographic databases from 2016 to 2022 for any original clinical studies assessing the STSF catheter for RFCA in AF patients. Meta-analysis with a random effects model was used for evidence synthesis. RESULTS: Pooled outcomes from 19 included studies indicated that STSF catheter was associated with a significantly shorter procedure time (weighted mean difference (WMD): -17.4 min, p<0.001), shorter ablation time (WMD: -6.6 min, p<0.001) and lower catheter irrigation fluid volume (WMD: -492.7 mL, p<0.001) than ST catheter. Pooled outcomes from four included studies with paroxysmal AF patients reported that using the STSF catheter for RFCA was associated with a significantly shorter ablation time (WMD: -5.7 min, p<0.001) and a lower risk of 1-year postablation arrhythmia recurrence (rate ratio: 0.504, p<0.001) than the SURROUNDFLOW (SF) catheter. Significant reductions in procedure time and ablation time associated with the STSF catheter were also reported in the other four studies using non-ST/SF catheters as the control. Overall complications of STSF catheter and control catheters were comparable. CONCLUSIONS: Using the STSF catheter was superior to using the ST catheter to conduct RFCA for AF by significantly reducing procedure time, ablation time, fluoroscopy time and irrigation fluid volume. The superiority of the STSF catheter over the SF catheter and other non-ST/SF catheters for RFCA needs further confirmation.

Clearance of Stress-Induced Premature Senescent Cells Alleviates the Formation of Abdominal Aortic Aneurysms.

Abdominal aortic aneurysm (AAA) is a multifactorial disease characterized by various pathophysiological processes, including chronic inflammation, oxidative stress, and proteolytic activity in the aortic wall. Stress-induced premature senescence (SIPS) has been implicated in regulating these pathophysiological processes, but whether SIPS contributes to AAA formation remains unknown. Here, we detected SIPS in AAA from patients and young mice. The senolytic agent ABT263 prevented AAA development by inhibiting SIPS. Additionally, SIPS promoted the transformation of vascular smooth muscle cells (VSMCs) from a contractile phenotype to a synthetic phenotype, whereas inhibition of SIPS by the senolytic drug ABT263 suppressed VSMC phenotypic switching. RNA sequencing and single-cell RNA sequencing analysis revealed that fibroblast growth factor 9 (FGF9), secreted by stress-induced premature senescent VSMCs, was a key regulator of VSMC phenotypic switching and that FGF9 knockdown abolished this effect. We further showed that the FGF9 level was critical for the activation of PDGFRß/ERK1/2 signaling, facilitating VSMC phenotypic change. Taken together, our findings demonstrated that SIPS is critical for VSMC phenotypic switching through the activation of FGF9/PDGFRß/ERK1/2 signaling, promoting AAA development and progression. Thus, targeting SIPS with the senolytic agent ABT263 may be a valuable therapeutic strategy for the prevention or treatment of AAA.

Extracellular vesicle-derived CircWhsc1 promotes cardiomyocyte proliferation and heart repair by activating TRIM59/STAT3/Cyclin B2 pathway.

INTRODUCTION: Extracellular vesicles (EVs)-mediated cell-to-cell communication is crucial for hypoxia-induced cell proliferation and tissue repair, but its function in endogenous cardiac regeneration is still unknown. OBJECTIVES: Herein, we aimed to determine whether hypoxia-inducible circWhsc1 in endothelial EVs promoted cardiomyocyte (CM) proliferation and cardiac regeneration. METHODS: RNA-sequence data was used to identify EV circRNAs that were involved into endogenous cardiac regeneration. Quantitative polymerase chain reactions were conducted to determine circRNA expression in tissue, cells and EVs. Gain- and loss-of-function assays were performed to explore the function of EV-derived circWhsc1 during cardiac regeneration. Western blotting and RNA pulldown assays were used to investigate its underlying mechanism. RESULTS: We found that circWhsc1 was enriched in neonatal mouse hearts, particularly in cardiac ECs, and was further upregulated both in ECs and EC-derived EVs under hypoxic conditions. When cocultured with hypoxia-preconditioned neonatal ECs or their secreted EVs, both neonatal and adult CMs exhibited an increased proliferation rate and G2/M ratio, which could be attenuated by knockdown of circWhsc1 in ECs. In vivo, EC-restricted overexpression of circWhsc1 and EV-mediated delivery of circWhsc1 induced CM proliferation, alleviated cardiac fibrosis and restored cardiac function following myocardial infarction in adult mice. Mechanistic studies revealed that EV-derived circWhsc1 activated TRIM59 by enhancing its phosphorylation, thereby reinforcing the binding of TRIM59 to STAT3, phosphorylating STAT3 and inducing CM proliferation. CONCLUSION: The current study demonstrated that hypoxia-inducible circWhsc1 in EC-derived EVs induces CM proliferation and heart regeneration. EC-CM communication mediated by EV-derived circWhsc1 might represent a prospective therapeutic target for inducing cardiac repair post-myocardial infarction.

CircRNA Samd4 induces cardiac repair after myocardial infarction by blocking mitochondria-derived ROS output.

Reactive oxygen species (ROS) derived from oxygen-dependent mitochondrial metabolism are the essential drivers of cardiomyocyte (CM) cell-cycle arrest in adulthood. Mitochondria-localized circular RNAs (circRNAs) play important roles in regulating mitochondria-derived ROS production, but their functions in cardiac regeneration are still unknown. Herein, we investigated the functions and underlying mechanism of mitochondria-localized circSamd4 in cardiac regeneration. We found that circSamd4 was selectively expressed in fetal and neonatal CMs. The transcription factor Nrf2 controlled circSamd4 expression by binding to the promoter of circSamd4 host gene. CircSamd4 overexpression reduced while circSamd4 silenced increased mitochondrial oxidative stress and subsequent oxidative DNA damage. Moreover, circSamd4 overexpression induced CM proliferation and prevented CM apoptosis, which reduced the size of the fibrotic area and improved cardiac function after myocardial infarction (MI). Mechanistically, circSamd4 reduced oxidative stress generation and maintained mitochondrial dynamics by inducing the mitochondrial translocation of the Vcp protein, which downregulated Vdac1 expression and prevented the mitochondrial permeability transition pore (mPTP) from opening. Our findings suggest that circSamd4 is a novel therapeutic target for heart failure after MI.

CircRNA Chordc1 protects mice from abdominal aortic aneurysm by contributing to the phenotype and growth of vascular smooth muscle cells.

Circular RNAs (circRNAs) have important potential in modulating vascular smooth muscle cell (VSMC) activity, but their roles in abdominal aortic aneurysm (AAA) are unknown. We performed in situ hybridization and immunohistochemistry and determined that circChordc1 (cysteine and histidine-rich domain containing 1) was markedly downregulated in aneurysm tissue compared with normal arteries. A gene gain and loss strategy was used to confirm that circChordc1 transformed VSMCs into a contracted phenotype and improved their growth, which significantly suppressed aneurysm formation and reduced the risk of rupture in mouse models of angiotensin (Ang) II- and CaCl2-induced AAA. RNA pull-down, immunoprecipitation, and immunoblotting indicated that circChordc1 facilitated the VSMC phenotype and growth determination by binding to vimentin and ANXA2 (annexin A2), which not only increased vimentin phosphorylation to promote its degradation but also promoted the interaction between ANXA2 and glycogen synthase kinase 3 beta (GSK3ß) to induce the nuclear entry of ß-catenin. Thus, our present study revealed that circChordc1 optimized the VSMC phenotype and improved their growth by inducing vimentin degradation and increasing the activity of the GSK3ß/ß-catenin pathway, thereby extenuating vascular wall remodeling and reversing pathological aneurysm progression.

High power drive laser system for photocathode at IHEP.

The photocathode drive laser system in the Institute of High Energy Physics (IHEP) has been upgraded. An all-fiber drive laser system has been developed using photonic crystal fibers and photonic crystal rods as the main gain medium. This system has been operated stably. The output infrared (IR) power reaches 116.2 W. The pulse width and maximum output power of the green laser generated by the second harmonic generation (SHG) are less than 2 ps and about 39.4 W, respectively. The SHG efficiency exceeds 60%. This paper introduces the development of the drive laser system and reports the measurement results of the performance test.

LncRNA Snhg1-driven self-reinforcing regulatory network promoted cardiac regeneration and repair after myocardial infarction.

Rationale: Most current cardiac regeneration approaches result in very limited cell division and little new cardiomyocyte (CM) mass. Positive feedback loops are vital for cell division, but their role in CM regeneration remains unclear. We aimed to determine whether the lncRNA small nucleolar RNA host gene 1 Snhg1 (Snhg1) could form a positive feedback loop with c-Myc to induce cardiac regeneration. Methods: Quantitative PCR and in situ hybridization experiments were performed to determine the Snhg1 expression patterns in fetal and myocardial infarction (MI) hearts. Gain- and Loss-of-function assays were conducted to explore the effect of Snhg1 on cardiomyocyte (CM) proliferation and cardiac repair following MI. We further constructed CM-specific Snhg1 knockout mice to confirm the proliferative effect exerted by Snhg1 using CRISPR/Cas9 technology. RNA sequencing and RNA pulldown were performed to explore how Snhg1 mediated cardiac regeneration. Chromatin immunoprecipitation and luciferase reporter assays were used to demonstrate the positive feedback loop between Snhg1 and c-Myc. Results: Snhg1 expression was increased in human and mouse fetal and myocardial infarction (MI) hearts, particularly in CMs. Overexpression of Snhg1 promoted CM proliferation, angiogenesis, and inhibited CM apoptosis after myocardial infarction, which further improved post-MI cardiac function. Antagonism of Snhg1 in early postnatal mice inhibited CM proliferation and impaired cardiac repair after MI. Mechanistically, Snhg1 directly bound to phosphatase and tensin homolog (PTEN) and induced PTEN degradation, activating the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway to promote CM proliferation. The c-Myc protein, one of downstream targets of PI3K/AKT signaling, functioned as a transcription factor by binding to the promoter regions of Snhg1. Perturbation of the positive feedback between Snhg1 and c-Myc by mutation of the binding sequence significantly affected Snhg1-induced CM proliferation. Conclusions: Snhg1 effectively elicited CM proliferation and improved cardiac function post-MI by forming a positive feedback loop with c-Myc to sustain PI3K/Akt signaling activation, and thus may be a promising cardiac regeneration strategy in treating heart failure post-MI.

circRNA Hipk3 Induces Cardiac Regeneration after Myocardial Infarction in Mice by Binding to Notch1 and miR-133a.

The synergism between cardiomyogenesis and angiogenesis is essential for cardiac regeneration. Circular RNAs (circRNAs) play pivotal roles in cell growth and angiogenesis, but their functions in cardiac regeneration are not yet known. In this study, we investigated the role and underlying mechanisms of circRNA Hipk3 (circHipk3) in both cardiomyogenesis and angiogenesis during cardiac regeneration. We found that circHipk3 was overexpressed in the fetal or neonatal heart of mice. The transcription factor Gata4 bound to the circHipk3 promoter and increased circHipk3 expression. Cardiomyocyte (CM) proliferation in vitro and in vivo was inhibited by circHipk3 knockdown and increased by circHipk3 overexpression. Moreover, circHipk3 overexpression promoted coronary vessel endothelial cell proliferation, migration, and tube-forming capacity and subsequent angiogenesis. More importantly, circHipk3 overexpression attenuated cardiac dysfunction and decreased fibrotic area after myocardial infarction (MI). Mechanistically, circHipk3 promoted CM proliferation by increasing Notch1 intracellular domain (N1ICD) acetylation, thereby increasing N1ICD stability and preventing its degradation. In addition, circHipk3 acted as a sponge for microRNA (miR)-133a to promote connective tissue growth factor (CTGF) expression, which activated endothelial cells. Our findings suggested that circHipk3 might be a novel therapeutic target for preventing heart failure post-MI.

Sirt1-inducible deacetylation of p21 promotes cardiomyocyte proliferation.

Inducing cardiomyocyte proliferation is a hopeful approach for cardiac regeneration following myocardial infarction. Previous studies have shown that p21 inhibits the cardiomyocyte proliferation and cardiac regeneration. Deacetylation of p21 by Sirt1 deacetylase may reduce p21 abundance and remove p21-induced cell cycle arrest. However, whether p21 deacetylation and Sirt1 deacetylate control cardiomyocyte proliferation is unclear. Here, we show that acetylation of p21 induces cardiomyocyte proliferation arrest, whereas blocking the acetylation of p21 increases cardiomyocyte proliferation. P21 can be acetylated by Sirt1, and Sirt1 activate p21 ubiquitination through deacetylation. Additionally, overexpression of Sirt1 induces EdU-, pH3-, and Aurora B-positive cardiomyocytes in neonatal and adult mice. In contrast, depletion of Sirt1 reduces cardiomyocyte proliferation in vitro and in vivo. Moreover, Sirt1 protects cardiac function, reduces cardiac remodeling, inhibits cardiomyocyte apoptosis, and attenuates cardiomyocyte hypertrophy post-myocardial infarction. These results suggest that Sirt1-induced p21 deacetylation plays an essential role in cardiomyocyte proliferation and that it could be a novel therapeutic strategy for myocardial infarction.

Long noncoding RNA GAS5 induces abdominal aortic aneurysm formation by promoting smooth muscle apoptosis.

Objective: Long noncoding RNAs (lncRNAs) may serve as specific targets for the treatment of abdominal aortic aneurysms (AAAs). LncRNA GAS5, functionally associated with smooth muscle cell (SMC) apoptosis and proliferation, is likely involved in AAA formation, but the exact role of GAS5 in AAA is unknown. We thus explored the contribution of GAS5 to SMC-regulated AAA formation and its underlying mechanisms. Methods: Human specimens were used to verify the diverse expression of GAS5 in normal and AAA tissues. The angiotensin II (Ang II)-induced AAA model in ApoE-/- mice and the CaCl2-induced AAA model in wild-type C57BL/6 mice were used. RNA pull-down and luciferase reporter gene assays were performed in human aortic SMCs to detect the interaction between GAS5 and its downstream targets of protein or microRNA (miR). Results: GAS5 expression was significantly upregulated in human AAA specimens and two murine AAA models compared to human normal aortas and murine sham-operated controls. GAS5 overexpression induced SMC apoptosis and repressed its proliferation, thereby promoting AAA formation in two murine AAA models. Y-box-binding protein 1 (YBX1) was identified as a direct target of GAS5 while it also formed a positive feedback loop with GAS5 to regulate the downstream target p21. Furthermore, GAS5 acted as a miR-21 sponge to release phosphatase and tensin homolog from repression, which blocked the activation and phosphorylation of Akt to inhibit proliferation and promote apoptosis in SMCs. Conclusion: The LncRNA GAS5 contributes to SMC survival during AAA formation. Thus, GAS5 might serve as a novel target against AAA.

Loss of Super-Enhancer-Regulated circRNA Nfix Induces Cardiac Regeneration After Myocardial Infarction in Adult Mice.

BACKGROUND: circRNAs (circular RNAs) are emerging as powerful regulators of cardiac development and disease, but their roles in cardiac regeneration are still unknown. This study used superenhancers to distinguish key circRNAs in the regulation of cardiac regeneration and explored the mechanisms underlying circRNA functions. METHODS: We used integrated bioinformatics analysis of RNA sequencing data and superenhancer catalogs to identify superenhancer-associated circRNAs. Quantitative polymerase chain reactions and in situ hybridization were performed to determine the circRNA expression patterns in hearts. Gain- and loss-of-function assays were conducted to detect the role of circRNAs in cardiomyocyte proliferation and cardiac repair after myocardial infarction. Chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assays were used to determine the binding of Meis1 (Meis homeobox 1) on circNfix-associated superenhancers. RNA pulldown and luciferase reporter assays were used to study circRNA interactions with proteins and miRNAs (micro RNAs). RESULTS: We identified a circRNA, Nfix circRNA (circNfix), that was regulated by a superenhancer and overexpressed in the adult heart in humans, rats, and mice. The transcription factor Meis1 bound to the superenhancer at the circNfix locus, and increased its expression. In vitro and in vivo, cardiomyocyte proliferation was increased by knockdown of circNfix, whereas it was inhibited by circNfix overexpression. Moreover, circNfix downregulation promoted cardiomyocyte proliferation and angiogenesis and inhibited cardiomyocyte apoptosis after myocardial infarction, attenuating cardiac dysfunction and improving the prognosis. Mechanistically, circNfix reinforced the interaction of Ybx1 (Y-box binding protein 1) with Nedd4l (an E3 ubiquitin ligase), and induced Ybx1 degradation through ubiquitination, repressing cyclin A2 and cyclin B1 expression. In addition, circNfix acted as a sponge for miR-214 to promote Gsk3ß (glycogen synthase kinase 3 ß) expression and repress ß-catenin activity. CONCLUSIONS: Loss of superenhancer-regulated circNfix promotes cardiac regenerative repair and functional recovery after myocardial infarction by suppressing Ybx1 ubiquitin-dependent degradation and increasing miR-214 activity and thus may be a promising strategy for improving the prognosis after MI.

Generation of picosecond pulses with variable temporal profiles and linear polarization by coherent pulse stacking in a birefringent crystal shaper.

We report the study and demonstration of a new laser pulse shaping system capable of generating linearly polarized picosecond laser pulses with variable temporal profiles including symmetric intensity distributions, as well as non-symmetric distributions, which are highly desired by various applications. It is found that both high transmittance and high stability of the shaped pulse can be achieved simultaneously when crystals are set at a specific phase delay through fine control of the crystal temperature. Although multi-crystal pulse stacking with different configurations was reported before particularly for flattop pulse generation, this new configuration leads to new opportunities for many potential applications over a wide range of laser wavelengths, pulse repetition rate, time structures and power levels. A practical double-pass temporal shaping configuration that significantly reduces the number of crystals is also proposed in this paper as a result of present study.

Long Non-coding RNA ECRAR Triggers Post-natal Myocardial Regeneration by Activating ERK1/2 Signaling.

Reactivating post-natal myocardial regeneration potential may be a feasible strategy to regenerate the injured adult heart. Long non-coding RNAs (lncRNAs) have been implicated in regulating cellular differentiation, but whether they can elicit a regenerative response in the post-natal heart remains unknown. In this study, by characterizing the lncRNA transcriptome in human hearts during the fetal-to-adult transition, we found that 3,092 lncRNAs were differentially expressed, and we further identified a novel upregulated fetal lncRNA that we called endogenous cardiac regeneration-associated regulator (ECRAR), which promoted DNA synthesis, mitosis, and cytokinesis in post-natal day 7 and adult rat cardiomyocytes (CMs). Overexpression of ECRAR markedly stimulated myocardial regeneration and induced recovery of cardiac function after myocardial infarction (MI). Knockdown of ECRAR inhibited post-natal day 1 CM proliferation and prevented post-MI recovery. ECRAR was transcriptionally upregulated by E2F transcription factor 1 (E2F1). In addition, ECRAR directly bound to and promoted the phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), resulting in downstream targets of cyclin D1 and cyclin E1 activation, which, in turn, activated E2F1. The E2F1-ECRAR-ERK1/2 signaling formed a positive feedback loop to drive cell cycle progression, and, therefore, it promoted CM proliferation. These findings indicated that our newly discovered ECRAR may be a valuable therapeutic target for heart failure.

Inhibition of AZIN2-sv induces neovascularization and improves prognosis after myocardial infarction by blocking ubiquitin-dependent talin1 degradation and activating the Akt pathway.

BACKGROUND: We previously found that loss of lncRNA-AZIN2 splice variant (AZIN2-sv) increases cardiomyocyte (CM) proliferation and attenuates adverse ventricular remodelling post-myocardial infarction (MI). However, whether inhibition of AZIN2-sv can simultaneously induce angiogenesis and thus improve prognosis after MI is unclear. METHODS: We used in situ hybridization and quantitative PCR to determine AZIN2-sv expression in endothelial cells. Knockdown and overexpression were performed to detect the role of AZIN2-sv in endothelial cell function, angiogenesis and prognosis after MI. RNA pulldown, RNA immunoprecipitation and luciferase reporter assays were used to determine the interaction with talin1 (Tln1) protein and miRNA-214 (miR-214). DNA pulldown and chromatin immunoprecipitation (ChIP) assays were used to study AZIN2-sv binding to upstream transcription factors. FINDINGS: AZIN2-sv was enriched in cardiac endothelial cells. The loss of AZIN2-sv reduced endothelial cell apoptosis and promoted endothelial sprouting and capillary network formation in vitro. Moreover, in vivo, the loss of AZIN2-sv induced angiogenesis and improved cardiac function after MI. Mechanistically, AZIN2-sv reduced Tln1 and integrin ß1 (ITGB1) protein levels to inhibit neovascularization. AZIN2-sv activated the ubiquitination-dependent degradation of Tln1 mediated by proteasome 26S subunit ATPase 5 (PSMC5). In addition, AZIN2-sv could bind to miR-214 and suppress the phosphatase and tensin homologue (PTEN)/Akt pathway to inhibit angiogenesis. With regard to the upstream mechanism, Bach1, a negative regulator of angiogenesis, bound to the promoter of AZIN2-sv and increased its expression. INTERPRETATION: Bach1-activated AZIN2-sv could participate in angiogenesis by promoting the PSMC5-mediated ubiquitination-dependent degradation of Tln1 and blocking the miR-214/PTEN/Akt pathway. Inhibition of AZIN2-sv induced angiogenesis and myocardial regeneration simultaneously, thus, AZIN2-sv could be an ideal therapeutic target for improving myocardial repair after MI. FUND: National Natural Science Foundations of China.

The effects of ultrasound exposure on P-glycoprotein-mediated multidrug resistance in vitro and in vivo.

BACKGROUND: Multidrug resistance (MDR) is often responsible for the failure of chemotherapy treatment, and current strategies for cancer MDR are not adequately satisfying as to their efficacy and safety. In this study, we sought to determine the anti-MDR effects of ultrasound (US) irradiation and its underlying mechanisms against drug-resistance. METHODS: MDR variant MCF-7/ADR cell lines and endothelial cell lines were used to determine the appropriate ultrasound intensity for in vitro experiments. MCF-7/ADR cell and HEPG2/ADM cells were used to assess the anti-MDR effect of US irradiation. Intracellular adriamycin (ADM) accumulation, Cell viability, cell proliferation and cell apoptosis were evaluated after ADM + US treatment or ADM treatment alone. MCF-7/ADR xenograft mice were used to investigate the appropriate ultrasound intensity for in vivo experiments and its effect on the long-term prognosis. Underlining mechanisms by which ultrasound exposure reversing MDR phenotype were investigated both in vitro and in vivo. RESULTS: Combination of ADM and 0.74 W/cm2 US irradiation enhanced ADM intracellular concentration and nuclear accumulation in MCF-7/ADR and HEPG2/ADM cells, compared to those treated with ADM alone. Enhanced cellular ADM uptake and nuclei localization was associated with increased cytotoxicity of ADM to ADM-resistant cells, lower ADM-resistant cell viability and proliferative cell ratio, and higher apoptotic cell ratio. More importantly, US exposure increased the effectiveness of ADM to inhibit tumor growth in MCF-7/ADR xenograft mice. Mechanistically, US exposure promoted ADM accumulation in MDR cells mainly through down-regulation of P-glycoprotein (P-gp), which is dependent on US-induced intracellular reactive oxygen species (ROS) production. US-induced oxidative stress promoted miR-200c-3p and miR-34a-3p expression by forming miR-200c/34a/ZEB1 double-negative feedback loop. Finally, US-induced miR-200c/34a overexpression decreased P-gp expression and reversed MDR phenotype. CONCLUSION: US irradiation could reverse MDR phenotype by activating ROS-ZEB1-miR200c/34a-P-gp signal pathway. Our findings offer a new and promising strategy for sensitizing cells to combat MDR and to improve the therapeutic index of chemotherapy.

Loss of long non-coding RNA CRRL promotes cardiomyocyte regeneration and improves cardiac repair by functioning as a competing endogenous RNA.

Long noncoding RNAs (lncRNAs) play critical roles in the development of myocardial hypertrophy and may stimulate endogenous myocardial regeneration to prevent heart failure after myocardial infarction (MI). However, whether lncRNAs are involved in regulating myocardial regeneration after MI remains unclear. The present study aimed to identify human-derived lncRNAs that are involved in endogenous cardiomyocyte (CM) regeneration. By analyzing publicly available RNA-seq data of human fetal and normal adult cardiac tissues, we identified a novel human-derived adult upregulated lncRNA designated cardiomyocyte regeneration-related lncRNA (CRRL). Bioinformatics analysis indicated that CRRL is involved in the negative regulation of CM proliferation. First, we observed that the loss of CRRL attenuates post-MI remodeling and preserves cardiac function in adult rats. Through loss-of-function approaches, we found that CRRL knockdown promotes neonatal rat CM proliferation both in vivo and in vitro. Furthermore, we demonstrated that CRRL acts as a competing endogenous RNA (ceRNA) by directly binding to miR-199a-3p and thereby increasing the expression of Hopx, a target gene of miR-199a-3p and a critical negative regulatory factor of CM proliferation. Thus, CRRL suppresses cardiomyocyte regeneration by directly binding to miR-199a-3p, indicating that loss of CRRL facilitates myocardial regeneration and may be a new potential therapeutic strategy for heart failure.