Bradykinin preconditioning improves therapeutic potential of human endothelial progenitor cells in infarcted myocardium

Bradykinin-pretreated Human cardiac-specific c-kit+ Cells Enhance Exosomal miR-3059-5p and Promote Angiogenesis Against Hindlimb Ischemia in mice

BACKGROUND

Protection of cardiac function following myocardial infarction was largely enhanced by bradykinin-pretreated cardiac-specific c-kit+ (BK-c-kit+) cells, even without significant engraftment, indicating that paracrine actions of BK-c-kit+ cells play a pivotal role in angiogenesis. Nevertheless, the active components of the paracrine actions of BK-c-kit+ cells and the underlying mechanisms remain unknown. This study aimed to define the active components of exosomes from BK-c-kit+ cells and elucidate their underlying protective mechanisms.

METHODS

Matrigel tube formation assay, cell cycle, and mobility in human umbilical vein endothelial cells (HUVECs) and hindlimb ischemia (HLI) in mice were applied to determine the angiogenic effect of condition medium (CM) and exosomes. Proteome profiler, microRNA sponge, Due-luciferase assay, microRNA-sequencing, qRT-PCR, and Western blot were used to determine the underlying mechanism of the angiogenic effect of exosomes from BK-c-kit+.

RESULTS

As a result, BK-c-kit+ CM and exosomes promoted tube formation in HUVECs and the repair of HLI in mice. Angiogenesis-related proteomic profiling and microRNA sequencing revealed highly enriched miR-3059-5p as a key angiogenic component of BK-c-kit+ exosomes. Meanwhile, loss- and gain-of-function experiments revealed that the promotion of angiogenesis by miR-3059-5p was mainly through suppression of TNFSF15-inhibited effects on vascular tube formation, cell proliferation and cell migration. Moreover, enhanced angiogenesis of miR-3059-5p-inhibited TNFSF15 has been associated with Akt/Erk1/2/Smad2/3-modulated signaling pathway.

CONCLUSION

Our results demonstrated a novel finding that BK-c-kit+ cells enrich exosomal miR-3059-5p to suppress TNFSF15 and promote angiogenesis against hindlimb ischemia in mice.

Human Whole Blood Interactions with Craniomaxillofacial Reconstruction Materials: Exploring In Vitro the Role of Blood Cascades and Leukocytes in Early Healing Events

The present study investigated early interactions between three alloplastic materials (calcium phosphate (CaP), titanium alloy (Ti), and polyetheretherketone (PEEK) with human whole blood using an established in vitro slide chamber model. After 60 min of contact with blood, coagulation (thrombin-antithrombin complexes, TAT) was initiated on all test materials (Ti > PEEK > CaP), with a significant increase only for Ti. All materials showed increased contact activation, with the KK-AT complex significantly increasing for CaP (p < 0.001), Ti (p < 0.01), and PEEK (p < 0.01) while only CaP demonstrated a notable rise in KK-C1INH production (p < 0.01). The complement system had significant activation across all materials, with CaP (p < 0.0001, p < 0.0001) generating the most pronounced levels of C3a and sC5b-9, followed by Ti (p < 0.001, p < 0.001) and lastly, PEEK (p < 0.001, p < 0.01). This activation correlated with leukocyte stimulation, particularly myeloperoxidase release. Consequently, the complement system may assume a more significant role in the early stages post implantation in response to CaP materials than previously recognized. Activation of the complement system and the inevitable activation of leukocytes might provide a more favorable environment for tissue remodeling and repair than has been traditionally acknowledged. While these findings are limited to the early blood response, complement and leukocyte activation suggest improved healing outcomes, which may impact long-term clinical outcomes.

Screening of the most efficacious lactic acid bacteria strain for myocardial infarction recovery and verification and exploration of its functions and mechanisms

Screening efficient strains by cell platform is cost-effective, but to date, no screening experiments have been performed for targeted lactic acid bacteria with hypoxic/reoxygenation (H/R)-treated cardiomyocytes, and their effects on the phosphoinositide 3-kinase (PI3K)/protein kinase b (Akt)/endothelial nitric oxide synthase (eNOS) pathway in myocardial infarction (MI) are unclear. Here we activated 102 strains of lactic acid bacteria and inoculated them into MRS medium for fermentation. The fermentation supernatants of the lactic acid bacteria were incubated with an H/R model of H9C2 cells. We found that Bifidobacterium longum ZL0210 had the greatest potential for inhibiting the apoptosis of H/R-induced H9C2 cells. Furthermore, it significantly increased the expression of heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (NQO1) in H9C2 cardiomyocytes, as well as the Bcl-2/Bax protein ratio, protecting damaged myocardial cells via an anti-apoptotic pathway. Intragastric administration of B. longum ZL0210 to mice for one week before and after establishment of an MI model drastically attenuated the myocardial cell hypertrophy and fibrosis of the MI mice. Meanwhile, B. longum ZL0210 significantly reduced the secretion of myocardial enzymes, increased the activity of antioxidant enzymes, and inhibited lipid-oxidative malondialdehyde (MDA) levels. Moreover, it upregulated the expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein and the phosphorylation levels of PI3K, Akt, and eNOS, resulting in increased NO contents. In summary, we screened 102 strains of lactic acid bacteria with a cell platform and determined that B. longum ZL0210 was a favorable candidate for protecting the myocardium. We are the first to reveal the protective effects of B. longum ZL0210 for MI via activation of the PI3K/Akt/eNOS pathway through TRAIL.

Pretreatment of cardiac progenitor cells with bradykinin attenuates H2O2-induced cell apoptosis and improves cardiac function in rats by regulating autophagy

Background

Previous studies have demonstrated that human cardiac c-Kit⁺ progenitor cells (hCPCs) can effectively improve ischemic heart disease. However, the major challenge in applying hCPCs to clinical therapy is the low survival rate of graft hCPCs in the host heart, which limited the benefit of transplanted hCPCs. Bradykinin (BK) is a principal active agent of the tissue kinin-kallikrein system. Our previous studies have highlighted that BK mediated the growth and migration of CPCs by regulating Ca²⁺ influx. However, the protective effect of BK on CPCs, improvement in the survival rate of BK-pretreated hCPCs in the infarcted heart, and the related mechanism remain elusive.

Methods

HCPCs were treated with H₂O₂ to induce cell apoptosis and autophagy, and different concentration of BK was applied to rescue the H₂O₂-induced injury detected by MTT assay, TUNEL staining, flow cytometry, western blotting, and mitoSOX assays. The role of autophagy in the anti-apoptotic effect of BK was chemically activated or inhibited using the autophagy inducer, rapamycin, or the inhibitor, 3-methyladenine (3-MA). To explore the protective effect of BK on hCPCs, 3-MA or BK-pretreated hCPCs were transplanted into the myocardial infarcted rats. An echocardiogram was used to determine cardiac function, H&E and Masson staining were employed to assess pathological characteristics, HLA gene expression was quantified by qRT-PCR, and immunostaining was applied to examine neovascularization using confocal microscopy.

Results

The in vitro results showed that BK suppressed H₂O₂-induced hCPCs apoptosis and ROS production in a concentration-dependent manner by promoting pAkt and Bcl-2 expression and reducing cleaved caspase 3 and Bax expression. Moreover, BK restrained the H₂O₂-induced cell autophagy by decreasing LC3II/I, Beclin1, and ATG5 expression and increasing P62 expression. In the in vivo experiment, the transplanted BK- or 3-MA-treated hCPCs were found to be more effectively improved cardiac function by decreasing cardiomyocyte apoptosis, inflammatory infiltration, and myocardial fibrosis, and promoting neovascularization in the infarcted heart, compared to untreated-hCPCs or c-kit^- cardiomyocytes (CPC^- cells).

Conclusions

Our present study established a new method to rescue transplanted hCPCs in the infarcted cardiac area via regulating cell apoptosis and autophagy of hCPCs by pretreatment with BK, providing a new therapeutic option for heart failure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02503-6.

Reducing Cardiac Injury during ST-Elevation Myocardial Infarction: A Reasoned Approach to a Multitarget Therapeutic Strategy

The significant reduction in ‘ischemic time’ through capillary diffusion of primary percutaneous intervention (pPCI) has rendered myocardial-ischemia reperfusion injury (MIRI) prevention a major issue in order to improve the prognosis of ST elevation myocardial infarction (STEMI) patients. In fact, while the ischemic damage increases with the severity and the duration of blood flow reduction, reperfusion injury reaches its maximum with a moderate amount of ischemic injury. MIRI leads to the development of post-STEMI left ventricular remodeling (post-STEMI LVR), thereby increasing the risk of arrhythmias and heart failure. Single pharmacological and mechanical interventions have shown some benefits, but have not satisfactorily reduced mortality. Therefore, a multitarget therapeutic strategy is needed, but no univocal indications have come from the clinical trials performed so far. On the basis of the results of the consistent clinical studies analyzed in this review, we try to design a randomized clinical trial aimed at evaluating the effects of a reasoned multitarget therapeutic strategy on the prevention of post-STEMI LVR. In fact, we believe that the correct timing of pharmacological and mechanical intervention application, according to their specific ability to interfere with survival pathways, may significantly reduce the incidence of post-STEMI LVR and thus improve patient prognosis.

The mobilization of splenic reservoir myeloid-derived suppressor cells in sepsis-induced myocardial injury

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) play key roles in sepsis, but whether the bone marrow is considered the only source remains unclear. The current knowledge about the mechanism of MDSCs leading to myocardial injury in sepsis is poor.

METHODS

In sepsis patients with cardiac dysfunction, the circulating percentage of CD14^-CD11b⁺ and serum concentrations of IL-6 and IL-1β were measured. A mouse sepsis model was established through caecum ligation and puncture (CLP). Animals were divided into four groups: control, sham, CLP and CLP+splenectomy (CLPS). Serum concentrations of IL-6, IL-1β, TnI and NT-proBNP were measured. CD11b⁺Gr-1⁺ cells were detected by immunofluorescence staining and RT-PCR. Myocardial injury was detected by HE, Masson and TUNEL staining. The expression of mTOR, P53 and caspase-3 was measured by Western blot.

RESULTS

In sepsis patients, circulating MDSCs were increased, and the serum concentrations of IL-6 and IL-1β were elevated. The serum concentrations of IL-6 and IL-1β were correlated with the ratio of circulating MDSCs. In the mouse sepsis model, the spleen was the major source of CD11b⁺Gr-1⁺ cells that migrated into circulation and the heart in sepsis. The serum concentrations of IL-6 and IL-1β were also elevated. Echocardiography and serum biomarkers showed that cardiomyocyte damage and cardiac hypofunction in sepsis-induced myocardial injury. The expression of CD11b, Gr-1 and pro-inflammatory cytokines in the heart was significantly higher in sepsis patients than that in controls. Pathological staining and TUNEL staining showed obvious myocardial damage and cell apoptosis. The Western blot analysis indicated that in the heart, the activation of mTOR was inhibited and that the expression of P53 and caspase-3 was elevated in sepsis-induced myocardial injury.

CONCLUSION

In sepsis-induced myocardial injury, splenic reservoir CD11b⁺Gr-1⁺ cells rapidly migrated into circulation and the heart, further impairing heart function via the high expression of P53 through the inhibition of mTOR.

How ACE inhibitors transformed the renin-angiotensin system

The renin-angiotensin system (RAS) now underlies the successful treatment of almost 50% of the patients in cardiovascular medicine, with serious possibilities of extension to diabetes, Alzheimer's disease and cancer. This clinical transformation started just over 50 years ago, with the unexpected identification of a bradykinin-potentiating peptide from snake venom, as a potent inhibitor of ACE which led to the development of the first synthetic inhibitor, captopril, followed by the angiotensin receptor blockers. This article analyses the transformation of the RAS into its different stages, from academic experiments to clinical use and back to the laboratory, identifying the critical events involved, both clinical and scientific. The analysis also assesses the contributions of chance, coincidence, and conviction that were crucial in this transformation. Although questions remain, the transformation of the RAS over the past five decades provides a success story for medicine, for pharmacology, and, most significantly, for patients.

Shear stress: An essential driver of endothelial progenitor cells

The blood flow through vessels produces a tangential, or shear, stress sensed by their innermost layer (i.e., endothelium) and representing a major hemodynamic force. In humans, endothelial repair and blood vessel formation are mainly performed by circulating endothelial progenitor cells (EPCs) characterized by a considerable expression of vascular endothelial growth factor receptor 2 (VEGFR2), CD34, and CD133, pronounced tube formation activity in vitro, and strong reendothelialization or neovascularization capacity in vivo. EPCs have been proposed as a promising agent to induce reendothelialization of injured arteries, neovascularization of ischemic tissues, and endothelialization or vascularization of bioartificial constructs. A number of preconditioning approaches have been suggested to improve the regenerative potential of EPCs, including the use of biophysical stimuli such as shear stress. However, in spite of well-defined influence of shear stress on mature endothelial cells (ECs), articles summarizing how it affects EPCs are lacking. Here we discuss the impact of shear stress on homing, paracrine effects, and differentiation of EPCs. Unidirectional laminar shear stress significantly promotes homing of circulating EPCs to endothelial injury sites, induces anti-thrombotic and anti-atherosclerotic phenotype of EPCs, increases their capability to form capillary-like tubes in vitro, and enhances differentiation of EPCs into mature ECs in a dose-dependent manner. These effects are mediated by VEGFR2, Tie2, Notch, and β1/3 integrin signaling and can be abrogated by means of complementary siRNA/shRNA or selective pharmacological inhibitors of the respective proteins. Although the testing of sheared EPCs for vascular tissue engineering or regenerative medicine applications is still an unaccomplished task, favorable effects of unidirectional laminar shear stress on EPCs suggest its usefulness for their preconditioning.

Strategies to Enhance the Effectiveness of Adult Stem Cell Therapy for Ischemic Heart Diseases Affecting the Elderly Patients

Myocardial infarctions and chronic ischemic heart disease both commonly and disproportionately affect elderly patients more than any other patient population. Despite available treatments, heart tissue is often permanently damaged as a result of cardiac injury. This review aims to summarize recent literature proposing the use of modified autologous adult stem cells to promote healing of post-infarct cardiac tissue. This novel cellular treatment involves isolation of adult stem cells from the patient, in vitro manipulation of these stem cells, and subsequent transplantation back into the patient's own heart to accelerate healing. One of the hindrances affecting this process is that cardiac issues are increasingly common in elderly patients, and stem cells recovered from their tissues tend to be pre-senescent or already in senescence. As a result, harsh in vitro manipulations can cause the aged stem cells to undergo massive in vivo apoptosis after transplantation. The consensus in literature is that inhibition or reversal of senescence onset in adult stem cells would be of utmost benefit. In fact, it is believed that this strategy may lower stem cell mortality and coerce aged stem cells into adopting more resilient phenotypes similar to that of their younger counterparts. This review will discuss a selection of the most efficient and most-recent strategies used experimentally to enhance the effectiveness of current stem cell therapies for ischemic heart diseases.

Human Umbilical Cord Mesenchymal Stem Cells Protect Against SCA3 by Modulating the Level of 70 kD Heat Shock Protein

Spinocerebellar ataxia 3 (SCA3), which is a progressive neurodegenerative disease, is currently incurable. Emerging studies have reported that human umbilical cord mesenchymal stem cells (HUC-MSCs) transplantation could be a promising therapeutic strategy for cerebellar ataxias. However, few studies have evaluated the effects of HUC-MSCs on SCA3 transgenic mouse. Thus, we investigated the effects of HUC-MSCs on SCA3 mice and the underlying mechanisms in this study. SCA3 transgenic mice received systematic administration of 2 × 10⁶ HUC-MSCs once per week for 12 continuous weeks. Motor coordination was measured blindly by open field tests and footprint tests. Immunohistochemistry and Nissl staining were applied to detect neuropathological alternations. Neurotrophic factors in the cerebellum were assessed by ELISA. We used western blotting to detect the alternations of heat shock protein 70 (HSP70), IGF-1, mutant ataxin-3, and apoptosis-associated proteins. Tunel staining was also used to detect apoptosis of affected cells. The distribution and differentiation of HUC-MSCs were determined by immunofluorescence. Our results exhibited that HUC-MSCs transplantation significantly alleviated motor impairments, corresponding to a reduction of cerebellar atrophy, preservation of neurons, decreased expression of mutant ataxin-3, and increased expression of HSP70. Implanted HUC-MSCs were mainly distributed in the cerebellum and pons with no obvious differentiation, and the expressions of IGF-1, VEGF, and NGF in the cerebellum were significantly elevated. Furthermore, with the use of HSP70 analogy quercetin injection, it demonstrated that HSP70 is involved in mutant ataxin-3 reduction. These results showed that HUC-MSCs implantation is a potential treatment for SCA3, likely through upregulating the IGF-1/HSP70 pathway and subsequently inhibiting mutant ataxin-3 toxicity.

Pinocembrin ex vivo preconditioning improves the therapeutic efficacy of endothelial progenitor cells in monocrotaline-induced pulmonary hypertension in rats

Pulmonary hypertension is still not curable and the available current therapies can only alleviate symptoms without hindering the progression of disease. The present study was directed to investigate the possible modulatory effect of pinocembrin on endothelial progenitor cells transplanted in monocrotaline-induced pulmonary hypertension in rats. Pulmonary hypertension was induced by a single subcutaneous injection of monocrotaline (60mg/kg). Endothelial progenitor cells were in vitro preconditioned with pinocembrin (25mg/L) for 30min before being i.v. injected into rats 2weeks after monocrotaline administration. Four weeks after monocrotaline administration, blood pressure, electrocardiography and right ventricular systolic pressure were recorded. Rats were sacrificed and serum was separated for determination of endothelin-1 and asymmetric dimethylarginine levels. Right ventricles and lungs were isolated for estimation of tumor necrosis factor-alpha and transforming growth factor-beta contents as well as caspase-3 activity. Moreover, protein expression of matrix metalloproteinase-9 and endothelial nitric oxide synthase in addition to myocardial connexin-43 was assessed. Finally, histological analysis of pulmonary arteries, cardiomyocyte cross-sectional area and right ventricular hypertrophy was performed and cryosections were done for estimation of cell homing. Preconditioning with pinocembrin provided a significant improvement in endothelial progenitor cells' effect towards reducing monocrotaline-induced elevation of inflammatory, fibrogenic and apoptotic markers. Furthermore, preconditioned cells induced a significant amelioration of endothelial markers and cell homing and prevented monocrotaline-induced changes in right ventricular function and histological analysis compared with native cells alone. In conclusion, pinocembrin significantly improves the therapeutic efficacy of endothelial progenitor cells in monocrotaline-induced pulmonary hypertension in rats.

A review of strategies for infarct size reduction during acute myocardial infarction

Advances in medical and interventional therapy over the last few decades have revolutionized the treatment of acute myocardial infarction. Despite the ability to restore epicardial coronary artery patency promptly through percutaneous coronary intervention, tissue level damage may continue. The reported 30-day mortality after all acute coronary syndromes is 2 to 3%, and around 5% following myocardial infarction. Post-infarct complications such as heart failure continue to be a major contributor to cardiovascular morbidity and mortality. Inadequate microvascular reperfusion leads to worse clinical outcomes and potentially strategies to reduce infarct size during periods of ischemia-reperfusion can improve outcomes. Many strategies have been tested, but no single strategy alone has shown a consistent result or benefit in large scale randomised clinical trials. Herein, we review the historical efforts, current strategies, and potential novel concepts that may improve myocardial protection and reduce infarct size.

Bradykinin inhibits oxidative stress-induced senescence of endothelial progenitor cells through the B2R/AKT/RB and B2R/EGFR/RB signal pathways

Circulating endothelial progenitor cells (EPCs) have multiple protective effects that facilitate repair of damage to tissues and organs. However, while various stressors are known to impair EPC function, the mechanisms of oxidative stress-induced EPC senescence remains unknown. We demonstrated that B2 receptor (B2R) expression on circulating CD34⁺ cells was significantly reduced in patients with diabetes mellitus (DM) as compared to healthy controls. Furthermore, CD34⁺ cell B2R expression in patients with DM was inversely correlated with plasma myeloperoxidase concentrations. Bradykinin (BK) treatment decreased human EPC (hEPC) senescence and intracellular oxygen radical production, resulting in reduced retinoblastoma 1 (RB) RNA expression in H₂O₂-induced senescent hEPCs and a reversal of the B2R downregulation that is normally observed in senescent cells. Furthermore, BK treatment of H₂O₂-exposed cells leads to elevated phosphorylation of RB, AKT, and cyclin D1 compared with H₂O₂-treatment alone. Antagonists of B2R, PI3K, and EGFR signaling pathways and B2R siRNA blocked BK protective effects. In summary, this study demonstrates that BK significantly inhibits oxidative stress-induced hEPC senescence though B2R-mediated activation of PI3K and EGFR signaling pathways.

Insight on stem cell preconditioning and instructive biomaterials to enhance cell adhesion, retention, and engraftment for tissue repair

Stem cells are a promising solution for the treatment of a variety of diseases. However, the limited survival and engraftment of transplanted cells due to a hostile ischemic environment is a bottleneck for effective utilization and commercialization. Within this environment, the majority of transplanted cells undergo apoptosis prior to participating in lineage differentiation and cellular integration. Therefore, in order to maximize the clinical utility of stem/progenitor cells, strategies must be employed to increase their adhesion, retention, and engraftment in vivo. Here, we reviewed key strategies that are being adopted to enhance the survival, retention, and engraftment of transplanted stem cells through the manipulation of both the stem cells and the surrounding environment. We describe how preconditioning of cells or cell manipulations strategies can enhance stem cell survival and engraftment after transplantation. We also discuss how biomaterials can enhance the function of stem cells for effective tissue regeneration. Biomaterials can incorporate or mimic extracellular function (ECM) function and enhance survival or differentiation of transplanted cells in vivo. Biomaterials can also promote angiogenesis, enhance engraftment and differentiation, and accelerate electromechanical integration of transplanted stem cells. Insight gained from this review may direct the development of future investigations and clinical trials.

Transplantation of bradykinin-preconditioned human endothelial progenitor cells improves cardiac function via enhanced Akt/eNOS phosphorylation and angiogenesis

This study determines whether preconditioning (PC) of human endothelial progenitor cells (hEPCs) with bradykinin promotes infarcted myocardium repair via enhanced activation of B2 receptor (B2R)-dependent Akt/eNOS and increased angiogenesis. hEPCs with or without bradykinin preconditioning (BK-PC) were transplanted into a nude mouse model of acute myocardial infarction. Survival of transplanted cells was assessed using DiD-labeled hEPCs. Infarct size, cardiac function, and angiogenesis were measured 10 d after transplantation. Akt, eNOS, and vascular endothelial growth factor (VEGF) expressions in cardiac tissues were detected by western blotting, and NO production was determined using an NO assay kit. The cell migration and tube formation in cultured hEPCs were determined using transwell chamber and matrigel tube formation assays, respectively. The VEGF levels in the cell supernatant were measured using an enzyme-linked immunosorbent assay kit. BK-PC-hEPCs improved cardiac function, decreased infarct size, and promoted neovascularization 10 d following transplantation. PC increased Akt and eNOS phosphorylation, VEGF expression, and NO production in the ischemic myocardium. The effects of BK-PC were abrogated by HOE140 (B2R antagonist) and LY294002 (Akt antagonist). PC increased hEPC migration, tube formation, and VEGF levels in vitro. Activation of B2R-dependent Akt/eNOS phosphorylation by BK-PC promotes hEPC neovascularization and improves cardiac function following transplantation.

Photoluminescent Mesoporous Silicon Nanoparticles with siCCR2 Improve the Effects of Mesenchymal Stromal Cell Transplantation after Acute Myocardial Infarction

BACKGROUND

Despite the benefits of mesenchymal stromal cell (MSC) transplantation in cardiac tissue, detailed in vivo observations have shown that MSCs only survive for a brief period after transplantation due to harsh microenvironmental conditions, including ischemia, inflammation and anoikis, in the infarcted myocardium. Thus, new strategies are needed to enhance MSC survival and inhibit cardiac remodeling. Studies have now demonstrated that chemokine [C-C motif] ligand 2 (CCL2) and its cognate receptor C-C chemokine receptor 2 (CCR2) promote excessive Ly6C(high) inflammatory monocyte infiltration at the infarct in response to ischemic myocardial injury. Therefore, decreasing the activities of these monocytes immediately after acute myocardial infarction (AMI) could be beneficial for AMI patients.

OBJECTIVES

This study tested the hypothesis that therapeutic siRNA-loaded photoluminescent mesoporous silicon nanoparticles (PMSNs) targeting CCR2 expression in Ly6C(high) inflammatory monocytes decrease the accumulation of these cells in the infarct, improve the efficacy of MSC transplantation and attenuate myocardial remodeling.

METHODS

PMSNs carrying therapeutic siCCR2 were first synthesized without the inclusion of fluorescent materials or dyes. After AMI BALB/c mice were established, 10(5) 5-ethynyl-2'- deoxyuridine (EdU)-labeled MSCs suspended in 100 µl of phosphate buffered saline (PBS) were injected into the border zone of the infarct of each mouse. PMSNs-siCCR2 (25 µg/g) were also intravenously injected via the tail vein immediately following AMI induction. Control mice were injected with an equal amount of PMSNs without siCCR2. PMSNs-siCCR2 were examined in vivo using near-infrared imaging technology. The therapeutic effects of PMSNs-siCCR2 for MSC transplantation were determined at the mRNA, protein and functional levels.

RESULTS

PMSNs-siCCR2 circulated freely in vivo and were cleared in a relatively short period of time (t(½)=37 min) with no evidence of toxicity. The therapeutic PMSNs-siCCR2 showed higher levels of cellular accumulation in Ly6C(high) monocytes in the spleen and more efficient degradation of CCR2 compared with the control (8.04%±2.17% vs. 20.02%±4.55%, p<0.001). Subsequently, the PMSNs-siCCR2 decreased the accumulation of CD11b-positive monocytes at the infarct (49.3%±17.34% vs. 61.32%±22.43%, p<0.001) on day 1. Increased survival of transplanted MSCs (13±3/mm(2) vs. 4±1/mm(2), p<0.001) and significantly decreased TdT-mediated dUTP nick end labeling (TUNEL)(+) cardiac myocytes (17.44%±6.26% vs. 39.49%±13.28%, p<0.001) were then identified in the infarct zone three days after AMI induction in the PMSNs-siCCR2 group. Three weeks after MSC injection, significant increases were observed in the vascular density (235.5±39.6/mm(2) vs. 147.4±20.3/mm(2), p<0.001) and the cardiac myosin-positive area (21.7%±8.4% vs. 13.2%±4.4%, p<0.001) of the infarct border zone. In addition, significant amelioration of left ventricular (LV) remodeling (thickness of the LV posterior walls) (0.84±0.11 mm vs. 0.61±0.08 mm, p<0.001) was also observed at the same time compared with the control group.

CONCLUSIONS

PMSNs-siCCR2-mediated CCR2 gene silencing in Ly6C(high) monocytes improved the effectiveness of MSC transplantation and selectively ameliorated myocardial remodeling after AMI. These results suggest that PMSNs-siCCR2 could potentially be used to develop an anti-inflammatory therapy for post-AMI MSC transplantation.

Transplantation of bradykinin-preconditioned human endothelial progenitor cells improves cardiac function via enhanced Akt/eNOS phosphorylation and angiogenesis

This study determines whether preconditioning (PC) of human endothelial progenitor cells (hEPCs) with bradykinin promotes infarcted myocardium repair via enhanced activation of B2 receptor (B2R)-dependent Akt/eNOS and increased angiogenesis. hEPCs with or without bradykinin preconditioning (BK-PC) were transplanted into a nude mouse model of acute myocardial infarction. Survival of transplanted cells was assessed using DiD-labeled hEPCs. Infarct size, cardiac function, and angiogenesis were measured 10 d after transplantation. Akt, eNOS, and vascular endothelial growth factor (VEGF) expressions in cardiac tissues were detected by western blotting, and NO production was determined using an NO assay kit. The cell migration and tube formation in cultured hEPCs were determined using transwell chamber and matrigel tube formation assays, respectively. The VEGF levels in the cell supernatant were measured using an enzyme-linked immunosorbent assay kit. BK-PC-hEPCs improved cardiac function, decreased infarct size, and promoted neovascularization 10 d following transplantation. PC increased Akt and eNOS phosphorylation, VEGF expression, and NO production in the ischemic myocardium. The effects of BK-PC were abrogated by HOE140 (B2R antagonist) and LY294002 (Akt antagonist). PC increased hEPC migration, tube formation, and VEGF levels in vitro. Activation of B2R-dependent Akt/eNOS phosphorylation by BK-PC promotes hEPC neovascularization and improves cardiac function following transplantation.

Telmisartan reduces atrial arrhythmia susceptibility through the regulation of RAS-ERK and PI3K-Akt-eNOS pathways in spontaneously hypertensive rats

Telmisartan is an angiotensin II receptor blocker that displays unique PPAR-γ modulating activity. PPAR-γ agonists have been shown to decrease susceptibility to atrial fibrillation through their antioxidant and antiapoptotic effects. The aim of this study was to determine whether telmisartan would have a greater effect on susceptibility to atrial arrhythmia in a hypertensive rat model than valsartan, which is a traditional angiotensin II receptor blocker. In this study, spontaneously hypertensive rats were treated with 10 mg·(kg body mass)(-1)·d(-1) telmisartan (TEL group), 10 mg·(kg body mass)(-1)·d(-1) valsartan (VAL group), or vehicle (saline; SHR group) for 4 weeks. Age-matched Wistar-Kyoto rats (WKY) were used as normotensive controls. After 4 weeks of treatment, we performed echocardiographic assessment, electrophysiological analysis, histological evaluation, and Western blot analysis. Telmisartan decreased systolic blood pressure to a similar extent as valsartan. Relative to the WKY controls, atrial arrhythmia susceptibility was significantly increased in the SHR group, and was significantly decreased by both telmisartan and valsartan, albeit to a greater extent with telmisartan. Arrhythmogenic atrial remodeling, including enlargement of the left atrium, myocyte hypertrophy, interstitial fibrosis, and myocyte apoptosis, was observed in the SHR group, and was accompanied by activated RAS-ERK signaling and suppressed PI3K-Akt-eNOS signaling. The results suggest that telmisartan reduced susceptibility to atrial arrhythmia to a greater extent than valsartan, ameliorated atrial remodeling, and reversed imbalances in the RAS-ERK and PI3K-Akt-eNOS pathways.

Inhibiting the mobilization of Ly6C(high) monocytes after acute myocardial infarction enhances the efficiency of mesenchymal stromal cell transplantation and curbs myocardial remodeling

BACKGROUND

Ischemia related inflammation is the most critical factor for the survival of transplanted mesenchymal stem cells (MSCs), and strategies for controlling excessive inflammation after acute myocardial infarction (AMI) are essential and necessary for cell transplantation therapy. Our present study tested the effect of decreased Ly6C(high) monocytes on mouse MSCs transplantation after AMI.

METHODS

BALB/c AMI mice were treated systemically with a CCR2 antagonist (RS 504393, 2 mg/kg, subcutaneously) or normal saline (control group). Next, 10(5) EdU-labeled MSCs were administered by intramyocardial injection to the mice in each group. TUNEL kits were used to identify the apoptotic cardiomyocytes in the infarct. The slides of the infarct border zone were stained with wheat germ agglutinin to measure the vessel density, and anti-myosin heavy chain eFluor 660 was used to measure the cardiac myosin-positive area. A transwell chamber was used to examine the interactions between Ly6C(high) monocytes and MSCs. The inflammatory cytokines expressed by Ly6C(high) monocytes and the SDF-1 expressed by MSCs were detected using ELISA kits. MSC viability was further examined by MTT and mitochondrial membrane potential assays by flow cytometry using JC-1 kits.

RESULTS

We first observed the increased survival of transplanted MSCs (11.2 ± 3.4/mm(2) vs. 3.5 ± 1.6/mm(2), p < 0.001), and the decreased apoptosis of cardiomyocytes (11.20% ± 3.55% vs. 20.51% ± 8.17%, p < 0.001) in the infarcts at 3 days in the CCR2 antagonist group. An increased number of capillaries and small arterioles (139.6 ± 21.7/mm(2) vs. 95.4 ± 17.6/mm(2), p < 0.001) and an increased cardiac myosin-positive area (17.9% ± 6.6% vs. 11.8% ± 3.5%, p < 0.001) were also observed in the infarct zone at 21 days post MSC infusion in the CCR2 antagonist group. In addition, a significantly increased LvEF% (50.17 ± 10.06 vs. 45.44 ± 9.45, p < 0.001) was detected at the same time compared to the control mice. We further demonstrated that both the mitochondrial membrane potential of the MSCs (0.45 ± 0.11 vs. 3.4 ± 0.3, p < 0.001) and stromal cell-derived factor-1 (SDF-1) secreted by the MSCs significantly decreased (80.77 ± 39.02 pg/ml vs. 435.5 ± 77.41 pg/ml, p < 0.001) when co-cultured with Ly6C(high) monocytes. This is possibly mediated by the over-expressed cytokines secreted by the Ly6C(high) monocytes compared to the Ly6C(low) monocytes, including IL-1 (139.45 ± 30.44 vs. 80.05 ± 19.33, p < 0.001), IL-6 (187.82 ± 40.43 vs. 135.5 ± 22.09, p < 0.001), TNF-α (121.77 ± 31.65 vs. 75.3 ± 22.14, p < 0.001) and IFN-γ (142.46 ± 27.55 vs. 88.25 ± 19.91, p < 0.001).

Targeting stress responses for regenerative medicine

Some internal and external stimuli elicit stress responses on the cellular level and at the level of the organism. When the stimulus is brief and its intensity mild to moderate, it triggers adaptation changes that improve the cell's or organism's survival. This adaptation is achieved through a variety of cellular mechanisms such as induction of repair mechanisms, improved removal of damaged macromolecules, upregulation of endogenous antioxidant defenses, and prevention of apoptosis triggering by moderate stressors. The key intracellular signaling pathways involved in stress adaptation are the mTORC1 and SIRT1. Manipulating these stress adaptation signaling pathways with a variety of agents, improves the cellular adaptation to stress, prolongs cell survival, and improves the transplantation outcome in animal models and in clinical trials. The challenge for the future is to fine-tune the numerous experimental techniques to suit the needs of transplantation and regenerative medicine.

Cardioprotective effect of betulinic Acid on myocardial ischemia reperfusion injury in rats

Objectives. This study aims to investigate the effect of betulinic acid (BA) on myocardial ischemia reperfusion/injury in an open-chest anesthetized rat model. Methods. The model was induced by 30 minutes left anterior descending occlusion followed by 2 hours reperfusion. There are six groups in our present study: sham operation group, ischemia/reperfusion group, low-dosage BA group, medium-dosage BA group, high-dosage BA group, and fosinopril sodium group. Rats in the latter four groups were administrated with BA (50, 100, and 200 mg/kg, i.g.) or fosinopril sodium (10 mg/kg, i.g.) once a day for 7 days before operation, respectively. Rats in the former two groups were given the same volume of vehicle (0.5% CMC-Na, i.g.). During the operation, cardiac function was continuously monitored. Serum LDH and CK were measured with colorimetric assays. The expression of Bcl-2 and Bax and the apoptosis of cardiomyocytes were investigated with western blot and TUNEL assay, respectively. Results. Pretreatment with BA improved cardiac function and attenuated LDH and CK activities compared with IR group. Further investigation demonstrated that the expression of Bcl-2 and Bax and TUNEL assay was in line with the above results. Conclusion. BA may reduce the release of LDH and CK, prevent cardiomyocytes apoptosis, and eventually alleviate the extent of the myocardial ischemia/reperfusion injury.

Venlafaxine protects methylglyoxal-induced apoptosis in the cultured human brain microvascular endothelial cells

It was reported that venlafaxine protects microvascular endothelial cells injury in several models. But the mechanisms of venlafaxine protects cell injury still poor understanding. Here, we shows that in the cultured human brain microvascular endothelial cells (HBMEC), we found that venlafaxine protects methylglyoxal (MGO)-induced cell injury, and the venlafaxine significant reduction in the level of reactive oxygen species, down-regulated expression of pro-apoptotic activated caspase-3 and Bax, increased BDNF release and expression of anti-apoptotic Bcl-2 in the cultured HBMEC. Furthermore, we found that venlafaxine inhibits MGO-induced phosphorylation of JNK. Moreover, venlafaxine increased AKT phosphorylation and the protective effects of venlafaxine was inhibited by PI3K/AKT inhibitor. These findings suggest that venlafaxine protects MGO-induced HBMEC injury through PI3K/AKT and JNK pathway as the potential underlying mechanisms of HBMEC injury in diabetes.