Remote ischaemic preconditioning increases serum extracellular vesicle concentrations with altered micro-RNA signature in CABG patients

Emerging Trends and Research Hotspots of Remote Ischemic Preconditioning in Cardiac Surgery: A Bibliometric Analysis

BACKGROUND

Remote ischemic preconditioning (RIPC) is a key area in cardiovascular research, but inconsistent findings have made it hard to fully understand. Bibliometrics, using mathematics and statistics, can track trends and progress in research over time. This study uses bibliometrics to assess RIPC trends and hotspots in cardiac surgery, aiming to better understand future research.

METHODS AND RESULTS

Studies on RIPC were retrieved from the Web of Science Core Collection, with 104 studies included contributing countries, collaborative countries, institutions, authors, journals, keywords, research topics, citation patterns, and the current state of research. in this field were visually analyzed by using R platform, VOS viewer, and Microsoft Excel. These publications mainly came from 29 countries and 65 institutions. All experiments were clinical studies, and the type of surgery involved was cardiac surgery. A significant percentage of publications occurred during the period from 2010 to 2020 (75; 72.11%). Germany made the most significant contribution to this field with 27 (25.96%) papers and had the highest total citation count (2314). J Thorac Cardiovasc Surg published the most studies (n = 6), followed by Basic Res Cardiol (n = 5). We identified 89 authors, among which Patrick Meybohm, Juergen Peters, and Matthias Thielmann had the most studies (n = 10).

CONCLUSIONS

RIPC has significant research value and potential in cardiac surgery, mainly focusing on organ protection during adult heart surgeries, especially myocardial protection. Although Germany and China are leading, more international cooperation is needed. Large-scale, standardized randomized controlled trials on RIPC are essential to provide higher-level evidence-based medical research.

Extracellular vesicles as standard-of-care therapy: will fast-tracking the regulatory processes help achieve the goal?

Extracellular Vesicles (EVs) became a focus of clinical research when experimental and pre-clinical studies showed that they mimic their parent cells' regenerative and therapeutic effects and their cargo carries disease-specific diagnostic and prognostic biomarkers. Since the publication of data forms an endpoint of the study, this review specifically focused on the published clinical trials done with EVs. For brevity, this review was restricted to the last 10 years. Unexpectedly, the literature search showed that very few clinical trials assessing the therapeutic applications of EVs were published in this period indicating that they have not reached their desired endpoint. Conversely, most studies showed the potential of EVs present in various biofluids as a promising source of diagnostic and prognostic biomarkers for various diseases, and predictive markers to assess the effectiveness of therapy. This stark difference in the numbers could perhaps be due to the time-consuming regulatory processes involved in the clinical-grade preparation and characterization of EVs, and the determination of their safety and effective dose regimens. One wonders whether fast-tracking regulatory affairs could help accelerate the therapeutic use of EVs. This aspect needs urgent attention.

Nanomedicine: A great boon for cardiac regenerative medicine

Cardiovascular disease (CVD) represents a significant global health challenge, remaining the leading cause of illness and mortality worldwide. The adult heart's limited regenerative capacity poses a major obstacle in repairing extensive damage caused by conditions like myocardial infarction. In response to these challenges, nanomedicine has emerged as a promising field aimed at improving treatment outcomes through innovative drug delivery strategies. Nanocarriers, such as nanoparticles (NPs), offer a revolutionary approach by facilitating targeted delivery of therapeutic agents directly to the heart. This precise delivery system holds immense potential for treating various cardiac conditions by addressing underlying mechanisms such as inflammation, oxidative stress, cell death, extracellular matrix remodeling, prosurvival signaling, and angiogenic pathways associated with ischemia-reperfusion injury. In this review, we provide a concise summary of the fundamental mechanisms involved in cardiac remodeling and regeneration. We explore how nanoparticle-based drug delivery systems can effectively target the afore-mentioned mechanisms. Furthermore, we discuss clinical trials that have utilized nanoparticle-based drug delivery systems specifically designed for cardiac applications. These trials demonstrate the potential of nanomedicine in clinical settings, paving the way for future advancements in cardiac therapeutics through precise and efficient drug delivery. Overall, nanomedicine holds promise in revolutionizing the treatment landscape of cardiovascular diseases by offering targeted and effective therapeutic strategies that address the complex pathophysiology of cardiac injuries.

Age affects the association of red blood cell indices with efficacy of remote ischemic conditioning in patients with acute moderate ischemic stroke

We conducted a post hoc analysis of Remote Ischemic Conditioning for Acute Moderate Ischemic Stroke (RICAMIS) to investigate whether red blood cell (RBC) indices are associated with efficacy of remote ischemic conditioning (RIC), and whether the association is affected by age. In this post hoc analysis, patients with RBC indices at admission were enrolled. RBC indices including RBC count, hematocrit (HCT), mean corpuscular volume (MCV), hemoglobin (HB), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) were analyzed. According to the median of these RBC indices, eligible patients were divided into high and low groups, which were further subdivided into RIC and control subgroups. Primary endpoint was excellent functional outcome defined as a modified Rankin Scale score of 0-1 at 90 days, which was used to evaluate RIC efficacy. RIC efficacy as well as effect of age on RIC efficacy were analyzed across the high and low groups of different RBC indices, and the interaction effects of RBC indices on RIC efficacy were evaluated. A total of 1640 patients were enrolled in the final analysis. In overall patients, no significant interaction effects of RIC intervention by all RBC indices were found, although there was a trend in interaction effect of RIC intervention by MCH (p = 0.116). However, we found an effect of age on the association of MCH with RIC efficacy. In patients over 60 years old, MCH significantly affected RIC efficacy (p = 0.006) and RIC significantly produced a higher proportion of primary outcome in high MCH (72.6% vs. 59.1%, P < 0.001) vs. low MCH group (61.2% vs. 62%, P = 0.829), which was not identified in patients under 60 years old. Furthermore, RIC efficacy decreased with increasing age in patients with low MCH with significant interaction effect (p = 0.012), while RIC efficacy increased with increasing age in patients with high MCH although no significant interaction (p = 0.126). No significant interaction effects of RIC intervention by RBC count, HCT, MCV, HB, and MCHC were found regardless of age. This secondary analysis of RICAMIS suggested that RIC exhibited more obvious benefit in AIS patients over 60 years old with high MCH compared with those with low MCH group, but RBC count, HCT, MCV, HB, and MCHC were not associated with the efficacy of RIC treatment regardless of age.

Influence of Anesthetic Regimes on Extracellular Vesicles following Remote Ischemic Preconditioning in Coronary Artery Disease

Remote ischemic preconditioning (RIPC) reduces ischemia-reperfusion injury in aortocoronary bypass surgery, potentially via extracellular vesicles (EVs) and their micro-RNA content. Clinical data implicate that propofol might inhibit the cardioprotective RIPC effect. This prospective, randomized study investigated the influence of different anesthetic regimes on RIPC efficacy and EV micro-RNA signatures. We also assessed the impact of propofol on cell protection after hypoxic conditioning and EV-mediated RIPC in vitro. H9c2 rat cardiomyoblasts were subjected to hypoxia, with or without propofol, and subsequent simulated ischemia-reperfusion injury. Apoptosis was measured by flow cytometry. Blood samples of 64 patients receiving anesthetic maintenance with propofol or isoflurane, along with RIPC or sham procedures, were analyzed, and EVs were enriched using a polymer-based method. Propofol administration corresponded with increased Troponin T levels (4669 ± 435.6 pg/mL), suggesting an inhibition of the cardioprotective RIPC effect. RIPC leads to a notable rise in miR-21 concentrations in the group receiving propofol anesthesia (fold change 7.22 ± 6.6). In vitro experiments showed that apoptosis reduction was compromised with propofol and only occurred in an EV-enriched preconditioning medium, not in an EV-depleted medium. Our study could clinically and experimentally confirm propofol inhibition of RIPC protection. Increased miR-21 expression could provide evidence for a possible inhibitory mechanism.

Cardioprotection in cardiovascular surgery

Since the invention of cardiopulmonary bypass, cardioprotective strategies have been investigated to mitigate ischemic injury to the heart during aortic cross-clamping and reperfusion injury with cross-clamp release. With advances in cardiac surgical and percutaneous techniques and post-operative management strategies including mechanical circulatory support, cardiac surgeons are able to operate on more complex patients. Therefore, there is a growing need for improved cardioprotective strategies to optimize outcomes in these patients. This review provides an overview of the basic principles of cardioprotection in the setting of cardiac surgery, including mechanisms of cardiac injury in the context of cardiopulmonary bypass, followed by a discussion of the specific approaches to optimizing cardioprotection in cardiac surgery, including refinements in cardiopulmonary bypass and cardioplegia, ischemic conditioning, use of specific anesthetic and pharmaceutical agents, and novel mechanical circulatory support technologies. Finally, translational strategies that investigate cardioprotection in the setting of cardiac surgery will be reviewed, with a focus on promising research in the areas of cell-based and gene therapy. Advances in this area will help cardiologists and cardiac surgeons mitigate myocardial ischemic injury, improve functional post-operative recovery, and optimize clinical outcomes in patients undergoing cardiac surgery.

Anti-angiogenic effect of exo-LncRNA TUG1 in myocardial infarction and modulation by remote ischemic conditioning

The successful use of exosomes in therapy after myocardial infarction depends on an improved understanding of their role in cardiac signaling and regulation. Here, we report that exosomes circulating after myocardial infarction (MI) carry LncRNA TUG1 which downregulates angiogenesis by disablement of the HIF-1α/VEGF-α axis and that this effect can be counterbalanced by remote ischemic conditioning (RIC). Rats with MI induced through left coronary artery ligation without (MI model) and with reperfusion (ischemia/reperfusion I/R model) were randomized to RIC, or MI (I/R) or sham-operated (SO) control. Data from one cohort study and one randomized-controlled trial of humans with MI were also utilized, the former involving patients who had not received percutaneous coronary intervention (PCI) and the latter patients with PCI. Exosome concentrations did not differ between intervention groups (RIC vs. control) in rats (MI and I/R model) as well as humans (with and without PCI). However, MI and I/R exosomes attenuated HIF-1α, VEGF-α, and endothelial function. LncRNA TUG1 was increased in MI and I/R exosomes, but decreased in SO and RIC exosomes. HIF-1α expression was downregulated with MI and I/R exosomes but increased with RIC exosomes. Exosome inhibition suppressed HIF-1α upregulation through RIC exosomes. VEGF-α was identified as HIF-1α-regulated target gene. Knockdown of HIF-1α decreased VEGF-α, endothelial cell capability, and tube formation. Overexpression of HIF-1α exerted opposite effects. Transfection and co-transfection of 293 T cells with exosome-inhibitor GW4869 and HIF-1α inhibitor si-HIF-1α confirmed the exosomal-LncRNA TUG1/HIF-1α/VEGF-α pathway. LncRNA TUG1 is a potential therapeutic target after MI with or without reperfusion through PCI.

Late plasma exosome microRNA-21-5p depicts magnitude of reverse ventricular remodeling after early surgical repair of primary mitral valve regurgitation

Introduction

Primary mitral valve regurgitation (MR) results from degeneration of mitral valve apparatus. Mechanisms leading to incomplete postoperative left ventricular (LV) reverse remodeling (Rev-Rem) despite timely and successful surgical mitral valve repair (MVR) remain unknown. Plasma exosomes (pEXOs) are smallest nanovesicles exerting early postoperative cardioprotection. We hypothesized that late plasma exosomal microRNAs (miRs) contribute to Rev-Rem during the late postoperative period.

Methods

Primary MR patients (n = 19; age, 45-71 years) underwent cardiac magnetic resonance imaging and blood sampling before (T0) and 6 months after (T1) MVR. The postoperative LV Rev-Rem was assessed in terms of a decrease in LV end-diastolic volume and patients were stratified into high (HiR-REM) and low (LoR-REM) LV Rev-Rem subgroups. Isolated pEXOs were quantified by nanoparticle tracking analysis. Exosomal microRNA (miR)-1, -21-5p, -133a, and -208a levels were measured by RT-qPCR. Anti-hypertrophic effects of pEXOs were tested in HL-1 cardiomyocytes cultured with angiotensin II (AngII, 1 μM for 48 h).

Results

Surgery zeroed out volume regurgitation in all patients. Although preoperative pEXOs were similar in both groups, pEXO levels increased after MVR in HiR-REM patients (+0.75-fold, p = 0.016), who showed lower cardiac mass index (-11%, p = 0.032). Postoperative exosomal miR-21-5p values of HiR-REM patients were higher than other groups (p < 0.05). In vitro, T1-pEXOs isolated from LoR-REM patients boosted the AngII-induced cardiomyocyte hypertrophy, but not postoperative exosomes of HiR-REM. This adaptive effect was counteracted by miR-21-5p inhibition.

Summary/Conclusion

High levels of miR-21-5p-enriched pEXOs during the late postoperative period depict higher LV Rev-Rem after MVR. miR-21-5p-enriched pEXOs may be helpful to predict and to treat incomplete LV Rev-Rem after successful early surgical MVR.

Remote ischemic preconditioning protects against cerebral ischemia injury in rats by upregulating miR-204-5p and activating the PINK1/Parkin signaling pathway

Remote ischemic preconditioning (RiPC) is the process where preconditioning ischemia protects the organs against the subsequent index ischemia. RiPC is a protective method for brain damage. This study is to explore the effect and mechanism of RiPC in cerebral ischemia injury in rats through regulation of miR-204-5p/BRD4 expression. Middle cerebral artery occlusion (MCAO) rat model and glucose deprivation (OGD) neuron model were established. The effect of RiPC on neurological deficits, cerebral infarct size, autophagy marker, inflammatory cytokines and apoptosis was evaluated. miR-204-5p expression was analyzed using RT-qPCR, and then downregulated using miR-204-5p antagomir to estimate its effect on MCAO rats. The downstream mechanism of miR-204-5p was explored. RiPC promoted autophagy, reduced cerebral infarct volume and neurological deficit score, and alleviated apoptosis and cerebral ischemia injury in rats, with no significant effects on healthy rat brains. RiPC up-regulated miR-204-5p expression in MCAO rats. miR-204-5p knockdown partially reversed the effect of RiPC. RiPC promoted autophagy in OGD cells, and attenuated inflammation and apoptosis. miR-204-5p targeted BRD4, which partially reversed the effect of miR-204-5p on OGD cells. RiPC activated the PINK1/Parkin pathway via the miR-204-5p/BRD4 axis. In conclusion, RiPC activated the PINK1/Parkin pathway and prevented cerebral ischemia injury by up-regulating miR-204-5p and inhibiting BRD4.

Sufentanil alleviates cerebral ischemia-reperfusion injury by inhibiting inflammation and protecting the blood-brain barrier in rats

Stroke is a brain system disease with a high fatality rate and disability rate. About 80% of strokes are ischemic strokes. Cerebral ischemia-reperfusion injury (CIRI) caused by ischemic stroke seriously affects the prognosis of stroke patients. The purpose of this study is to investigate the effect of sufentanil (SUF) on CIRI model rats. We used middle cerebral artery occlusion (MCAO) to make the CIRI model in rats and monitored region cerebral blood flow (rCBF) to ensure that blood flow was blocked and recanalized. We used ELISA and RT-PCR to detect the expression of inflammatory factors in rat serum and brain tissue. In addition, we detected the expression of metalloproteinase (MMP) 2, MMP9 and collagen IV in brain tissues and performed Evans blue (EB) assay to determine the permeability of the blood-brain barrier (BBB). Finally, we clarified the apoptosis of brain tissue through the TUNEL staining and the detection of caspase3, Bcl2 and Bax. Various concentrations of SUF, especially 5, 10 and 25 μg/kg of SUF, all alleviated the infarct size, neurological function and brain edema of MCAO rats. SUF pretreatment also effectively reduced the expression of inflammatory cytokines in MCAO rats, including interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10 and tumor necrosis factor (TNF)-α. In addition, SUF also inhibited MMP2 and MMP9 and promoted the expression of collagen IV, indicating that SUF attenuated the destruction of the BBB. SUF also inhibited caspase3 and Bax rats and promoted Bcl2 in MCAO rats, thus inhibiting cell apoptosis. SUF pretreatment effectively improved the neurological function and cerebral infarction of MCAO rats, inhibited excessive inflammation in rats, protected the BBB, and inhibited cell apoptosis in brain tissue.

HIF-1α mediates the protective effect of plasma extracellular particles induced by remote ischaemic preconditioning on oxidative stress injury in human umbilical vein endothelial cells

Remote ischaemic preconditioning (RIPC) is considered to alleviate myocardial ischaemia/reperfusion (I/R) injury. The present study explored whether blood plasma particulate matter, which is termed extracellular particles (EPs), and is released from cells during RIPC, could reduce H₂O₂-induced damage in human umbilical vein endothelial cells (HUVECs). Firstly, EPs were derived from volunteers who did or did not undergo RIPC. To induce RIPC in volunteers, a blood pressure cuff was alternatively inflated for 5 min and deflated for the same duration for four successive cycles. HUVECs were assigned to two groups: i) Group 1 was preincubated for 24 h with EPs from volunteers after sham-RIPC, then treated with H₂O₂ (1 mM; 6 h) to mimic the in vivo conditions of I/R-induced oxidative stress; and ii) group 2 was preincubated for 24 h with EPs from volunteers after RIPC, then treated with H₂O₂. Subsequently, EPs were derived from rats received sham-RIPC or RIPC and/or cadmium (Cd) pre-treatment. To induce RIPC in rats, a remote hind limb preconditioning stimulus was delivered using a blood pressure cuff attached at the inguinal level of the rat. The blood pressure cuff was alternatively inflated for 5 min and deflated for the same time period for four successive cycles. HUVECs were assigned to six groups: i) Group 1 was untreated; ii) group 2 received only H₂O₂ treatment (1 mM; 6 h); iii) group 3 was preincubated for 24 h with EPs from rats exposed to sham-RIPC, then treated with H₂O₂; iv) group 4 was preincubated for 24 h with EPs from rats that received an intraperitoneal injection of 1 mg/kg Cd [a pharmacological inhibitor of hypoxia-inducible factor 1-α (HIF-1α) in vivo] 180 min before sham-RIPC, then treated with H₂O₂; v) group 5 was preincubated for 24 h with EPs from rats exposed to RIPC, then treated with H₂O₂; and vi) group 6 was preincubated for 24 h with EPs from rats that received an intraperitoneal injection of 1 mg/kg Cd 180 min before RIPC, then treated with H₂O₂. Cell viability and cytotoxicity were monitored using Cell Counting Kit-8 and lactate dehydrogenase assays. Cell apoptosis and necrosis were assessed via flow cytometry and western blot analysis. A notable increase in EP concentration in the plasma of volunteers after RIPC compared with that in the plasma of volunteers after sham-RIPC was observed. RIPC-associated EPs (RIPC-EPs) from volunteers could improve cell viability and reduce cytotoxicity, cell apoptosis and necrosis in HUVECs treated with H₂O₂in vitro. Furthermore, RIPC caused a significant increase in HIF-1α expression in the rat limb musculature. The apoptosis-reducing effect of RIPC-EPs was demonstrated to be counteracted by an intraperitoneal injection of Cd before RIPC in rats. A significant decrease in the EP levels precipitated from the plasma of rats that received Cd treatment before RIPC was observed compared with rats that did not receive Cd treatment. The present study suggested that HIF-1α mediated at least partly the protective effect of plasma RIPC-EPs on oxidative stress injury in HUVECs.

Immune Modulation as a Key Mechanism for the Protective Effects of Remote Ischemic Conditioning After Stroke

Remote ischemic conditioning (RIC), which involves a series of short cycles of ischemia in an organ remote to the brain (typically the limbs), has been shown to protect the ischemic penumbra after stroke and reduce ischemia/reperfusion (IR) injury. Although the exact mechanism by which this protective signal is transferred from the remote site to the brain remains unclear, preclinical studies suggest that the mechanisms of RIC involve a combination of circulating humoral factors and neuronal signals. An improved understanding of these mechanisms will facilitate translation to more effective treatment strategies in clinical settings. In this review, we will discuss potential protective mechanisms in the brain and cerebral vasculature associated with RIC. We will discuss a putative role of the immune system and circulating mediators of inflammation in these protective processes, including the expression of pro-and anti-inflammatory genes in peripheral immune cells that may influence the outcome. We will also review the potential role of extracellular vesicles (EVs), biological vectors capable of delivering cell-specific cargo such as proteins and miRNAs to cells, in modulating the protective effects of RIC in the brain and vasculature.

Impact of the Main Cardiovascular Risk Factors on Plasma Extracellular Vesicles and Their Influence on the Heart's Vulnerability to Ischemia-Reperfusion Injury

The majority of cardiovascular deaths are associated with acute coronary syndrome, especially ST-elevation myocardial infarction. Therapeutic reperfusion alone can contribute up to 40 percent of total infarct size following coronary artery occlusion, which is called ischemia-reperfusion injury (IRI). Its size depends on many factors, including the main risk factors of cardiovascular mortality, such as age, sex, systolic blood pressure, smoking, and total cholesterol level as well as obesity, diabetes, and physical effort. Extracellular vesicles (EVs) are membrane-coated particles released by every type of cell, which can carry content that affects the functioning of other tissues. Their role is essential in the communication between healthy and dysfunctional cells. In this article, data on the variability of the content of EVs in patients with the most prevalent cardiovascular risk factors is presented, and their influence on IRI is discussed.

Circulating platelet-derived extracellular vesicles are decreased after remote ischemic preconditioning in patients with coronary disease: A randomized controlled trial

BACKGROUND

Brief nonharmful ischemia, remote ischemic preconditioning (RIPC) has been proposed to confer benefit to patients with coronary artery disease via unknown mechanisms.

OBJECTIVES

We aimed to investigate the effect of RIPC on circulating levels of extracellular vesicles (EVs) and global coagulation and fibrinolytic factors in patients with coronary disease.

PATIENTS/METHODS

Blood samples were taken from 60 patients presenting for coronary angiography enrolled in a randomized, controlled trial before and after RIPC (3 × 5 min administration of 200 mmHg sphygmomanometer on the arm, n = 31) or sham (n = 29) treatment. Most patients (n = 48) had significant coronary artery disease and all were taking at least one antiplatelet agent.

RESULTS

Remote ischemic preconditioning significantly decreased circulating levels of EVs expressing platelet markers CD41 and CD61 detected by flow cytometry in plasma, whereas no such effect was found on EVs expressing phosphatidylserine, CD62P, CD45, CD11b, CD144, CD31+ /CD41- , or CD235a. RIPC had no effect on the overall hemostatic potential assay or circulating antigen levels of tissue plasminogen activator, urokinase, plasminogen activator inhibitor-1, or plasminogen. Sham treatment had no effect on any studied parameter. Statin use inhibited the effect of RIPC on CD61+ EVs, diabetes modified the effect of RIPC on CD45+ and CD11b+ EVs, and hypertension modified the effect of RIPC on CD235a+ EVs.

CONCLUSIONS

Remote ischemic preconditioning decreased circulating levels of platelet-derived EVs in patients with coronary disease taking conventional antiplatelet therapy. This may reflect increased EV clearance/uptake or change in production. Clinical variables may alter the effectiveness of RIPC.

Percutaneous Coronary Intervention (PCI) Reprograms Circulating Extracellular Vesicles from ACS Patients Impairing Their Cardio-Protective Properties

Extracellular vesicles (EVs) are promising therapeutic tools in the treatment of cardiovascular disorders. We have recently shown that EVs from patients with Acute Coronary Syndrome (ACS) undergoing sham pre-conditioning, before percutaneous coronary intervention (PCI) were cardio-protective, while EVs from patients experiencing remote ischemic pre-conditioning (RIPC) failed to induce protection against ischemia/reperfusion Injury (IRI). No data on EVs from ACS patients recovered after PCI are currently available. Therefore, we herein investigated the cardio-protective properties of EVs, collected after PCI from the same patients. EVs recovered from 30 patients randomly assigned (1:1) to RIPC (EV-RIPC) or sham procedures (EV-naive) (NCT02195726) were characterized by TEM, FACS and Western blot analysis and evaluated for their mRNA content. The impact of EVs on hypoxia/reoxygenation damage and IRI, as well as the cardio-protective signaling pathways, were investigated in vitro (HMEC-1 + H9c2 co-culture) and ex vivo (isolated rat heart). Both EV-naive and EV-RIPC failed to drive cardio-protection both in vitro and ex vivo. Consistently, EV treatment failed to activate the canonical cardio-protective pathways. Specifically, PCI reduced the EV-naive Dusp6 mRNA content, found to be crucial for their cardio-protective action, and upregulated some stress- and cell-cycle-related genes in EV-RIPC. We provide the first evidence that in ACS patients, PCI reprograms the EV cargo, impairing EV-naive cardio-protective properties without improving EV-RIPC functional capability.

Remote ischemic preconditioning improves tissue oxygenation in a porcine model of controlled hemorrhage without fluid resuscitation

Remote ischemic preconditioning (RIPC) involves deliberate, brief interruptions of blood flow to increase the tolerance of distant critical organs to ischemia. This study tests the effects of limb RIPC in a porcine model of controlled hemorrhage without replacement therapy simulating an extreme field situation of delayed evacuation to definitive care. Twenty-eight pigs (47 ± 6 kg) were assigned to: (1) control, no procedure (n = 7); (2) HS = hemorrhagic shock (n = 13); and (3) RIPC + HS = remote ischemic preconditioning followed by hemorrhage (n = 8). The animals were observed for 7 h after bleeding without fluid replacement. Survival rate between animals of the RIPC + HS group and those of the HS group were similar (HS, 6 of 13[46%]-vs-RIPC + HS, 4 of 8[50%], p = 0.86 by Chi-square). Animals of the RIPC + HS group had faster recovery of mean arterial pressure and developed higher heart rates without complications. They also had less decrease in pH and bicarbonate, and the increase in lactate began later. Global oxygen delivery was higher, and tissue oxygen extraction ratio lower, in RIPC + HS animals. These improvements after RIPC in hemodynamic and metabolic status provide essential substrates for improved cellular response after hemorrhage and reduction of the likelihood of potentially catastrophic consequences of the accompanying ischemia.

Cardioprotection by remote ischemic conditioning is transferable by plasma and mediated by extracellular vesicles

BACKGROUND

Remote ischemic conditioning (RIC) by brief periods of limb ischemia and reperfusion protects against ischemia-reperfusion injury. We studied the cardioprotective role of extracellular vesicles (EV)s released into the circulation after RIC and EV accumulation in injured myocardium.

METHODS

We used plasma from healthy human volunteers before and after RIC (pre-PLA and post-PLA) to evaluate the transferability of RIC. Pre- and post-RIC plasma samples were separated into an EV enriched fraction (pre-EV + and post-EV +) and an EV poor fraction (pre-EV- and post-EV-) by size exclusion chromatography. Small non-coding RNAs from pre-EV + and post-EV + were purified and profiled by NanoString Technology. Infarct size was compared in Sprague-Dawley rat hearts perfused with isolated plasma and fractions in a Langendorff model. In addition, fluorescently labeled EVs were used to assess homing in an in vivo rat model. (ClinicalTrials.gov, number: NCT03380663) RESULTS: Post-PLA reduced infarct size by 15% points compared with Pre-PLA (55 ± 4% (n = 7) vs 70 ± 6% (n = 8), p = 0.03). Post-EV + reduced infarct size by 16% points compared with pre-EV + (53 ± 15% (n = 13) vs 68 ± 12% (n = 14), p = 0.03). Post-EV- did not affect infarct size compared to pre-EV- (64 ± 3% (n = 15) and 68 ± 10% (n = 16), p > 0.99). Three miRNAs (miR-16-5p, miR-144-3p and miR-451a) that target the mTOR pathway were significantly up-regulated in the post-EV + group. Labelled EVs accumulated more intensely in the infarct area than in sham hearts.

CONCLUSION

Cardioprotection by RIC can be mediated by circulating EVs that accumulate in injured myocardium. The underlying mechanism involves modulation of EV miRNA that may promote cell survival during reperfusion.

Does remote ischaemic conditioning reduce inflammation? A focus on innate immunity and cytokine response

The benefits of remote ischaemic conditioning (RIC) have been difficult to translate to humans, when considering traditional outcome measures, such as mortality and heart failure. This paper reviews the recent literature of the anti-inflammatory effects of RIC, with a particular focus on the innate immune response and cytokine inhibition. Given the current COVID-19 pandemic, the inflammatory hypothesis of cardiac protection is an attractive target on which to re-purpose such novel therapies. A PubMed/MEDLINE™ search was performed on July 13th 2020, for the key terms RIC, cytokines, the innate immune system and inflammation. Data suggest that RIC attenuates inflammation in animals by immune conditioning, cytokine inhibition, cell survival and the release of anti-inflammatory exosomes. It is proposed that RIC inhibits cytokine release via a reduction in nuclear factor kappa beta (NF-κB)-mediated NLRP3 inflammasome production. In vivo, RIC attenuates pro-inflammatory cytokine release in myocardial/cerebral infarction and LPS models of endotoxaemia. In the latter group, cytokine inhibition is associated with a profound survival benefit. Further clinical trials should establish whether the benefits of RIC in inflammation can be observed in humans. Moreover, we must consider whether uncomplicated MI and elective surgery are the most suitable clinical conditions in which to test this hypothesis.

Vascular conditioning prevents adverse left ventricular remodelling after acute myocardial infarction: a randomised remote conditioning study

AIMS

Remote ischemic conditioning (RIC) alleviates ischemia-reperfusion injury via several pathways, including micro-RNAs (miRs) expression and oxidative stress modulation. We investigated the effects of RIC on endothelial glycocalyx, arterial stiffness, LV remodelling, and the underlying mediators within the vasculature as a target for protection.

METHODS AND RESULTS

We block-randomised 270 patients within 48 h of STEMI post-PCI to either one or two cycles of bilateral brachial cuff inflation, and a control group without RIC. We measured: (a) the perfusion boundary region (PBR) of the sublingual arterial microvessels to assess glycocalyx integrity; (b) the carotid-femoral pulse wave velocity (PWV); (c) miR-144,-150,-21,-208, nitrate-nitrite (NOx) and malondialdehyde (MDA) plasma levels at baseline (T0) and 40 min after RIC onset (T3); and (d) LV volumes at baseline and after one year. Compared to baseline, there was a greater PBR and PWV decrease, miR-144 and NOx levels increase (p < 0.05) at T3 following single- than double-cycle inflation (PBR:ΔT0-T3 = 0.249 ± 0.033 vs 0.126 ± 0.034 μm, p = 0.03 and PWV:0.4 ± 0.21 vs -1.02 ± 0.24 m/s, p = 0.03). Increased miR-150,-21,-208 (p < 0.05) and reduced MDA was observed after both protocols. Increased miR-144 was related to PWV reduction (r = 0.763, p < 0.001) after the first-cycle inflation in both protocols. After one year, single-cycle RIC was associated with LV end-systolic volume reduction (LVESV) > 15% (odds-ratio of 3.75, p = 0.029). MiR-144 and PWV changes post-RIC were interrelated and associated with LVESV reduction at follow-up (r = 0.40 and 0.37, p < 0.05), in the single-cycle RIC.

CONCLUSION

RIC evokes "vascular conditioning" likely by upregulation of cardio-protective microRNAs, NOx production, and oxidative stress reduction, facilitating reverse LV remodelling.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov . Unique identifier: NCT03984123.

Targeting the Endothelium to Achieve Cardioprotection

Despite considerable improvements in the treatment of myocardial infarction, it is still a highly prevalent disease worldwide. Novel therapeutic strategies to limit infarct size are required to protect myocardial function and thus, avoid heart failure progression. Cardioprotection is a research topic with significant achievements in the context of basic science. However, translation of the beneficial effects of protective approaches from bench to bedside has proven difficult. Therefore, there is still an unmet need to study new avenues leading to protecting the myocardium against infarction. In line with this, the endothelium is an essential component of the cardiovascular system with multiple therapeutic targets with cardioprotective potential. Endothelial cells are the most abundant non-myocyte cell type in the heart and are key players in cardiovascular physiology and pathophysiology. These cells can regulate vascular tone, angiogenesis, hemostasis, and inflammation. Accordingly, endothelial dysfunction plays a fundamental role in cardiovascular diseases, which may ultimately lead to myocardial infarction. The endothelium is of paramount importance to protect the myocardium from ischemia/reperfusion injury via conditioning strategies or cardioprotective drugs. This review will provide updated information on the most promising therapeutic agents and protective approaches targeting endothelial cells in the context of myocardial infarction.

MicroRNA Mediated Cardioprotection - Is There a Path to Clinical Translation?

In the past 20 years, there have been several approaches to achieve cardioprotection or cardiac regeneration using a vast variety of cell therapies and remote ischemic pre-conditioning (RIPC). To date, substantial proof that either cell therapy or RIPC has the potential for clinically relevant cardiac repair or regeneration of cardiac tissue is still pending. Preclinical trials indicate that the secretome of cells in situ (during RIPC) as well as of transplanted cells may exhibit cardioprotective properties in the acute setting of cardiac injury. The secretome generally consists of cell-specific cytokines and extracellular vesicles (EVs) containing microRNAs (miRNAs). It is currently hypothesized that a subset of known miRNAs play a crucial part in the facilitation of cardioprotective effects. miRNAs are small non-coding RNA molecules that inhibit post-transcriptional translation of messenger RNAs (mRNAs) and play an important role in gene translation regulation. It is also known that one miRNAs usually targets multiple mRNAs. This makes predictability of pharmacokinetics and mechanism of action very difficult and could in part explain the inferior performance of various progenitor cells in clinical studies. Identification of miRNAs involved in cardioprotection and remodeling, the composition of miRNA profiles, and the exact mechanism of action are important to the design of future cell-based but also cell-free cardioprotective therapeutics. This review will give a description of miRNA with cardioprotective properties and a current overview on known mechanism of action and potential missing links. Additionally, we will give an outlook on the potential for clinical translation of miRNAs in the setting of myocardial infarction and heart failure.

Extracellular vesicles isolated from patients undergoing remote ischemic preconditioning decrease hypoxia-evoked apoptosis of cardiomyoblasts after isoflurane but not propofol exposure

Remote ischemic preconditioning (RIPC) can evoke cardioprotection following ischemia/reperfusion and this may depend on the anesthetic used. We tested whether 1) extracellular vesicles (EVs) isolated from humans undergoing RIPC protect cardiomyoblasts against hypoxia-induced apoptosis and 2) this effect is altered by cardiomyoblast exposure to isoflurane or propofol. EVs were isolated before and 60 min after RIPC or Sham from ten patients undergoing coronary artery bypass graft surgery with isoflurane anesthesia and quantified by Nanoparticle Tracking Analysis. Following EV-treatment for 6 hours under exposure of isoflurane or propofol, rat H9c2 cardiomyoblasts were cultured for 18 hours in normoxic or hypoxic atmospheres. Apoptosis was detected by flow cytometry. Serum nanoparticle concentrations in patients had increased sixty minutes after RIPC compared to Sham (2.5x10¹¹±4.9x10¹⁰ nanoparticles/ml; Sham: 1.2x10¹¹±2.0x10¹⁰; p = 0.04). Hypoxia increased apoptosis of H9c2 cells (hypoxia: 8.4%±0.6; normoxia: 2.5%±0.1; p<0.0001). RIPC-EVs decreased H9c2 cell apoptosis compared to control (apoptotic ratio: 0.83; p = 0.0429) while Sham-EVs showed no protection (apoptotic ratio: 0.97). Prior isoflurane exposure in vitro even increased protection (RIPC-EVs/control, apoptotic ratio: 0.79; p = 0.0035; Sham-EVs/control, apoptotic ratio:1.04) while propofol (50μM) abrogated protection by RIPC-EVs (RIPC-EVs/control, Apoptotic ratio: 1.01; Sham-EVs/control, apoptotic ratio: 0.94; p = 0.602). Thus, EVs isolated from patients undergoing RIPC under isoflurane anesthesia protect H9c2 cardiomyoblasts against hypoxia-evoked apoptosis and this effect is abrogated by propofol. This supports a role of human RIPC-generated EVs in cardioprotection and underlines propofol as a possible confounder in RIPC-signaling mediated by EVs.

Upregulation of miR‑423 improves autologous vein graft restenosis via targeting ADAMTS‑7

Coronary artery bypass graft (CABG) is one of the primary methods of treating coronary heart disease (CHD); however, vein graft restenosis is a major limiting factor of the effectiveness of CABG. Emerging evidence has indicated that miR‑423 is associated with vascular diseases. Additionally, upregulation of a disintegrin and metalloproteinase with thrombospondin motifs‑7 (ADAMTS‑7) contributes to neointima formation by promoting the proliferation and migration of vascular smooth muscle cells and inhibiting the proliferation and migration of endothelial cells. The aim of the present study was to examine the effects of miR‑423 target, ADAMTS‑7, on regulating vein graft disease and identify novel biomarkers for use in therapy of vein graft failure (VGF). Aberrant expression of miR‑423 in plasma of patients with CHD prior to and following CABG confirms that miR‑423 may be a suitable target for preventing VGF. Furthermore, a dual‑luciferase reporter gene assay indicated that miR‑423 directly interacted with ADAMTS‑7 and suppressed its expression. Ectopic expression of miR‑423 suppressed ADAMTS‑7, resulting in decreased proliferation and migration rates of human umbilical vein smooth muscle cells by targeting ADAMTS‑7, but resulted in increased proliferation and migration of human umbilical vein endothelial cells in vitro. Overexpression of miR‑423 also enhanced re‑endothelialization and decreased neointimal formation in a rat vein graft model. In conclusion, the results of the present study demonstrated that the miR‑423/ADAMTS‑7 axis may possess potential clinical value for the prevention and treatment of restenosis in patients with CHD following CABG.

Remote Ischemic Pre-Conditioning Attenuates Adverse Cardiac Remodeling and Mortality Following Doxorubicin Administration in Mice

Objectives

Because of its multifaceted cardioprotective effects, remote ischemic pre-conditioning (RIPC) was examined as a strategy to attenuate doxorubicin (DOX) cardiotoxicity.

Background

The use of DOX is limited by dose-dependent cardiotoxicity and heart failure. Oxidative stress, mitochondrial dysfunction, inflammation, and autophagy modulation have been proposed as mediators of DOX cardiotoxicity.

Methods

After baseline echocardiography, adult male CD1 mice were randomized to either sham or RIPC protocol (3 cycles of 5 min femoral artery occlusion followed by 5 min reperfusion) 1 h before receiving DOX (20 mg/kg, intraperitoneal). The mice were observed primarily for survival over 85 days (86 mice). An additional cohort of 50 mice was randomized to either sham or RIPC 1 h before DOX treatment and was followed for 25 days, at which time cardiac fibrosis, apoptosis, and mitochondrial oxidative phosphorylation were assessed, as well as the expression profiles of apoptosis and autophagy markers.

Results

Survival was significantly improved in the RIPC cohort compared with the sham cohort (p = 0.007). DOX-induced cardiac fibrosis and apoptosis were significantly attenuated with RIPC compared with sham (p < 0.05 and p < 0.001, respectively). Although no mitochondrial dysfunction was detected at 25 days, there was a significant increase in autophagy markers with DOX that was attenuated with RIPC. Moreover, DOX caused a 49% decline in cardiac BCL2/BAX expression, which was restored with RIPC (p < 0.05 vs. DOX). DOX also resulted in a 17% reduction in left ventricular mass at 25 days, which was prevented with RIPC (p < 0.01), despite the lack of significant changes in left ventricular ejection fraction.

Conclusions

Our preclinical results suggested that RIPC before DOX administration might be a promising approach for attenuating DOX cardiotoxicity.

The role of microglia in ischemic preconditioning

Ischemic preconditioning (IPC) is an experimental phenomenon in which a brief ischemic stimulus confers protection against a subsequent prolonged ischemic event. Initially thought to be due to mechanistic changes in neurons, our understanding of IPC has evolved to encompass a global reprogramming of the Central Nervous System (CNS) after transient ischemia/reperfusion that requires innate immune signaling pathways including Toll-like receptors (TLRs) and Type I interferons. Microglia are the CNS resident neuroimmune cells that express these key innate immune receptors. Studies suggest that microglia are required for IPC-mediated neuronal and axonal protection. Multiple paradigms targeting TLRs have converged on a distinctive Type I interferon response in microglia that is critical for preconditioning-mediated protection against ischemia. These pathways can be targeted through administration of TLR agonists, cytokines including interferon-β, and pharmaceutical agents that induce preconditioning through cross-tolerance mechanisms. Transcriptomic analyses and single cell RNA studies point to specific gene expression signatures in microglia that functionally shift these mutable cells to an immunomodulatory or protective phenotype. Although there are technological challenges and gaps in knowledge to overcome, the targeting of specific molecular signaling pathways in microglia is a promising direction for development of novel and effective pharmacotherapies for stroke. Studies on preconditioning in animal models, including nonhuman primates, show promise as prophylactic preconditioning treatments for selected at risk patient populations. In addition, our growing understanding of the mechanisms of IPC-mediated protection is identifying novel cellular and molecular targets for therapeutic interventions that could apply broadly to both acute stroke and chronic vascular cognitive impairment patients.