Preservation Of Myocardial Function Research Articles

Mitochondrial transplantation preserves myocardial function and viability in pediatric and neonatal pig hearts donated after circulatory death

ObjectiveMitochondrial transplantation has been shown to preserve myocardial function and viability in adult porcine hearts donated after circulatory death (DCD) . Herein, we investigate the efficacy of mitochondrial transplantation for the preservation of myocardial function and viability in neonatal and pediatric porcine DCD heart donation. MethodsCirculatory death was induced in neonatal and pediatric Yorkshire pigs by cessation of mechanical ventilation. Hearts underwent 20 or 36 minutes of warm ischemia time (WIT), 10 minutes of cold cardioplegic arrest, and then were harvested for ex situ heart perfusion (ESHP). Following 15 minutes of ESHP, hearts received either vehicle (VEH) or vehicle containing isolated autologous mitochondria (MITO). A sham nonischemic group (SHAM) did not undergo WIT, mimicking donation after brain death heart procurement. Hearts underwent 2 hours each of unloaded and loaded ESHP perfusion. ResultsFollowing 4 hours of ESHP perfusion, left ventricle developed pressure, dP/dt max, and fractional shortening were significantly decreased (P < .001) in DCD hearts receiving VEH compared with SHAM hearts. In contrast, DCD hearts receiving MITO exhibited significantly preserved left ventricle developed pressure, dP/dt max, and fractional shortening (P < .001 each vs VEH, not significant vs SHAM). Infarct size was significantly decreased in DCD hearts receiving MITO as compared with VEH (P < .001). Pediatric DCD hearts subjected to extended WIT demonstrated significantly preserved fractional shortening and significantly decreased infarct size with MITO (P < .01 each vs VEH). ConclusionsMitochondrial transplantation in neonatal and pediatric pig DCD heart donation significantly enhances the preservation of myocardial function and viability and mitigates against damage secondary to extended WIT.

DJ-1 Deficiency Protects against Sepsis-Induced Myocardial Depression

Oxidative stress is considered one of the early underlying contributors of sepsis-induced myocardial depression. DJ-1, also known as PARK7, has a well-established role as an antioxidant. We have previously shown, in a clinically relevant model of polymicrobial sepsis, DJ-1 deficiency improved survival and bacterial clearance by decreasing ROS production. In the present study, we investigated the role of DJ-1 in sepsis-induced myocardial depression. Here we compared wildtype (WT) with DJ-1 deficient mice at 24 and 48 h after cecal ligation and puncture (CLP). In WT mice, DJ-1 was increased in the myocardium post-CLP. DJ-1 deficient mice, despite enhanced inflammatory and oxidative responses, had an attenuated hypertrophic phenotype, less apoptosis, improved mitochondrial function, and autophagy, that was associated with preservation of myocardial function and improved survival compared to WT mice post-CLP. Collectively, these results identify DJ-1 as a regulator of myocardial function and as such, makes it an attractive therapeutic target in the treatment of early sepsis-induced myocardial depression.

Transcriptomic and proteomic pathways of diabetic and non-diabetic mitochondrial transplantation

Reduced mitochondrial function increases myocardial susceptibility to ischemia–reperfusion injury (IRI) in diabetic hearts. Mitochondrial transplantation (MT) ameliorates IRI, however, the cardioprotective effects of MT may be limited using diabetic mitochondria. Zucker Diabetic Fatty (ZDF) rats were subjected to temporary myocardial RI and then received either vehicle alone or vehicle containing mitochondria isolated from either diabetic ZDF or non-diabetic Zucker lean (ZL) rats. The ZDF rats were allowed to recover for 2 h or 28 days. MT using either ZDF- or ZL-mitochondria provided sustained reduction in infarct size and was associated with overlapping upregulation of pathways associated with muscle contraction, development, organization, and anti-apoptosis. MT using either ZDF- or ZL-mitochondria also significantly preserved myocardial function, however, ZL- mitochondria provided a more robust long-term preservation of myocardial function through the mitochondria dependent upregulation of pathways for cardiac and muscle metabolism and development. MT using either diabetic or non-diabetic mitochondria decreased infarct size and preserved functional recovery, however, the cardioprotection afforded by MT was attenuated in hearts receiving diabetic compared to non-diabetic MT.

Abstract 14959: Mitochondrial Transplantation in Pediatric and Neonatal Porcine Hearts in a Model of DCD Heart Transplantation

Introduction: Heart transplantation in pediatric and neonatal patients is limited by the donor pool. Donation after circulatory death (DCD) could potentially expand the donor pool by offering an additional source of cardiac allografts. In this study, we investigated the efficacy of mitochondrial transplantation to enhance myocardial function in pediatric and neonatal DCD hearts. Hypothesis: Autologous mitochondrial transplantation enhances the viability and function of pediatric and neonatal DCD donor hearts. Methods: Circulatory death was induced by extubation in neonatal (25 - 50g heart weight, representing 4-16 month human) and pediatric (68 - 98g heart weight, representing 4-6 year human) swine model. Hearts were subjected to 20 min of warm ischemia and 10 min of cold cardioplegic arrest and then harvested. The aorta and pulmonary artery were cannulated, inferior and superior venae cavae ligated and a balloon was inserted in the left ventricle. The hearts were then mounted on the ex situ perfusion device. After 15 minutes of reperfusion, hearts received either vehicle alone ([VEH], 10 mL n = 6) or vehicle containing autologous mitochondria ([MT] 5x10 9 in 10 mL; n = 6). A Sham non-ischemic group (n = 4) did not undergo warm ischemia, mimicking donor after brain death (DBD). Hearts were machine perfused for 2 hours unloaded and 2 hours of loaded conditions. Results: Following 4 hours of reperfusion, neonatal and pediatric DCD hearts receiving VEH showed significantly decreased myocardial function and viability as compared to Sham non-ischemic control hearts. In contrast, in both neonatal and pediatric DCD hearts receiving MT, LVDP, dP/dt max, and fractional shortening were significantly increased (p &lt; 0.001 for each) and were equal or better than that observed in Sham non-ischemic hearts. Infarct size was significantly decreased in both neonatal and pediatric DCD hearts receiving MT as compared to VEH (p &lt; 0.001). Conclusions: Mitochondrial transplantation provides for significantly enhanced preservation of myocardial function and viability in neonatal and pediatric DCD hearts that is equivalent to or better than that observed in DBD hearts. Mitochondrial transplantation provides a possible option to expand the pediatric and neonatal heart donor pool.

Prolonged (24-hour) Normothermic ex vivo Heart Perfusion Facilitated by Perfusate Hemofiltration.

Currently, normothermic ex vivo heart perfusion (NEVHP) is limited to 6-12 hours. NEVHP for 24 hours or more would allow organ treatment, assessment of organ function, and near-perfect recipient matching. We present a model of NEVHP using continuous hemofiltration (HFn) with sustained myocardial viability up to 24 hours. Twenty hearts from 6-10 kg piglets were procured and maintained on our NEVHP circuit. HFn hearts (n = 10) underwent NEVHP with HFn, whereas controls (n = 10) used NEVHP alone. All HFn vs. four controls were viable at 24 h (p = 0.004). At end perfusion, HFn hearts had higher left ventricular systolic pressure (51.5 ± 6.8 mm Hg, 38.3 ± 5.2 mm Hg, p = 0.05), lower coronary resistance (0.83 ± 0.11 mm Hg/mL/min, 1.18 ± 0.21mmHg/mL/min, p &lt; 0.05), and lower serum lactate levels (2.9 ± 0.4 mmol/L, 4.1 ± 0.6 mmol/L, p &lt; 0.0001) when compared to control hearts. HFn hearts also had less extensive myocardial damage and significantly less edema than control hearts with lower weight gain and wet-dry ratios. Using our circuit, NEVHP for 24 hours is possible with HFn and allows for preservation of myocardial function, improved tissue viability, decreased tissue edema, and less myocardial injury.

Inactivation of Interleukin-4 Receptor α Signaling in Myeloid Cells Protects Mice From Angiotensin II/High Salt-Induced Cardiovascular Dysfunction Through Suppression of Fibrotic Remodeling.

BackgroundHypertension‐induced cardiovascular remodeling is characterized by chronic low‐grade inflammation. Interleukin‐4 receptor α (IL‐4Rα) signaling is importantly involved in cardiovascular remodeling, however, the target cell type(s) is unclear. Here, we investigated the role of myeloid‐specific IL‐4Rα signaling in cardiovascular remodeling induced by angiotensin II and high salt.Methods and ResultsMyeloid IL‐4Rα deficiency suppressed both the in vitro and in vivo expression of alternatively activated macrophage markers including Arg1 (arginase 1), Ym1 (chitinase 3‐like 3), and Relmα/Fizz1 (resistin‐like molecule α). After angiotensin II and high salt treatment, myeloid‐specific IL‐4Rα deficiency did not change hypertrophic remodeling within the heart and aorta. However, myeloid IL‐4Rα deficiency resulted in a substantial reduction in fibrosis through the suppression of profibrotic pathways and the enhancement of antifibrotic signaling. Decreased fibrosis was associated with significant preservation of myocardial function in MyIL4RαKO mice and was mediated by attenuated alternative macrophage activation.ConclusionsMyeloid IL‐4Rα signaling is substantially involved in fibrotic cardiovascular remodeling by controlling alternative macrophage activation and regulating fibrosis‐related signaling. Inhibiting myeloid IL‐4Rα signaling may be a potential strategy to prevent hypertensive cardiovascular diseases.

A nephroprotective iodinated contrast agent with cardioprotective properties: A pilot study.

Background and PurposeEvaluation and treatment of acute ischemic syndromes, in the heart and brain, require vessel visualization by iodinated X‐ray contrast agents. However, these contrast agents can induce injury, in both the kidneys and target organs themselves. Sulfobutylether beta cyclodextrin (SBECD) added to iohexol (SBECD‐iohexol) (Captisol Enabled‐iohexol, Ligand Pharmaceuticals, Inc, San Diego, CA) is currently in clinical trials in cardiovascular procedures, to determine its relative renal safety in high‐risk patients. Preclinical studies showed that SBECD‐iohexol reduced contrast‐induced acute kidney injury in rodent models by blocking apoptosis. The current study was undertaken to determine whether SBECD‐iohexol is also cardioprotective, in the male rat ischemia‐reperfusion model, compared to iohexol alone.MethodsAfter anesthesia, the left coronary artery was ligated for 30 min and the ligation released and reperfusion followed for 2 h prior to sacrifice. Groups 1–4 were injected in the tail vein 10 min prior to ischemia with: (1) vehicle; (2) iohexol; (3) SBECD; and (4) SBECD‐iohexol. Infarct size, hemodynamics, and serum markers were measured.ResultsAn eight‐fold increase in serum creatine kinase in the iohexol‐alone group was observed, compared with no increase in the SBECD‐iohexol group. The mean arterial pressure and rate pressure product were depressed in the iohexol‐alone group, but not in the SBECD‐iohexol group, or controls. No difference in infarct size or serum creatinine among the groups was observed.ConclusionThe results of this study suggest that SBECD‐iohexol is superior to iohexol alone, for both the preservation of cardiomyocyte integrity and preservation of myocardial function in myocardial ischemia.

Preservation and Recovery of Myocardial Function during Normothermic Ex Situ Heart Perfusion: Does the Position of the Heart during Perfusion Matter?

Ex-situ heart perfusion preserves the donated heart in a perfused and semi-physiologic condition preventing preservation-related ischemia however, myocardial function declines overtime in this setting. All models of ex-situ heart perfusion (ESHP) position the heart in a suspended state which is at considerable variance with the in vivo positioning of the heart. In vivo, the aorta, vasculature and extracellular matrix support the myocardial mass. We hypothesize that the suspended myocardium may sustain greater injury and therefore may have greater decline in function compared to the supported myocardium. In this study, cardiac function and metabolism was assessed in healthy pig hearts, perfused for 12 hours, in either a conventional suspended position (susp) in which the heart is perfused suspending from the main vascular cannulas, or in a supported position (supp) in which the heart is perfused lying on a supporting membrane with integrated vascular cannulas (Figure 1). The hearts in each position were perfused either in non-working mode (NWM) or working mode (WM). Cardiac function was best preserved in the hearts perfused in a supported position in WM (relative 11-hour cardiac index / 1-hour cardiac index %: WM-supp=94.25 vs. NWM-supp=54.85, WM-susp=37.43, NWM-sup=11.17, p<0.001). Plasma cardiac troponin-I was significantly lower in supported-perfused compared to suspended-perfused hearts after 11 hours of perfusion (12.17 versus 20.80 ng/mL, p=0.001). Delivery of pyruvate bolus after 11 hours of perfusion, while leading to significant improvement of function in supported-perfused hearts, only partially recovered the myocardial function in the suspended-perfused groups (relative cardiac index %: supp= 100.31, susp= 41.50, p<0.001). ESHP in a semi-anatomical supported position, and physiologic, WM leads to less tissue injury and better preservation of myocardial function and viability.

Intensified Statin Preserves Global Longitudinal Strain in Transplanted Heart

Left ventricular (LV) global longitudinal strain (GLS) is a robust marker of subclinical myocardial dysfunction. Previous studies showed that as small as 2% reduction in GLS predicted major adverse event in heart transplant (HT) recipients, including cardiac allograft vasculopathy (CAV). Although low intensity statin is commonly used after HT to reduce CAV, the incremental impact of statin intensity on myocardial function is unknown. A single center, retrospective review was conducted in all adult HT recipients between 2012 and 2016. Patients were excluded for: death, LV ejection fraction <50%, rejection ≥ ISHLT 2R, angiographic CAV and interrupted statin therapy. Echocardiograms performed at 1 and 3-year outpatient follow-up were reviewed for remaining patients, who were further excluded for having poor acoustic windows. Included patients were divided into those on low intensity statin (pravastatin 20-40mg) and clinically intensified statin (atorvastatin 10mg or higher intensity) at 1-year follow up and were compared for GLS. Measurements of GLS were performed on apical views by two readers blinded to statin exposure. Forty-three HT recipients (low intensity statin, n=21; intensified statin, n=22) comprised the study population. Age, sex, donor age, presence of pre-HT VAD, and immunosuppression regimen were not significantly different between groups. Importantly, GLS was preserved in HT recipients receiving intensified statin (-17.0 ± 3.3 vs. -17.1 ± 2.5%, p=0.62) but significantly reduced in low intensity statin group (-17.5 ± 2.5 vs. -15.8 ± 2.5%, p=0.029, Figure 1A). The degree of GLS reduction was significantly higher during low intensity statin use (1.8 ± 1.5%) in comparison to intensified statin (0.13 ± 2.7%, p=0.044, Figure 1B). Interobserver correlation coefficient was 0.95. Intensified statin after HT is associated with preservation of myocardial function during intermediate term follow up, indicating a favorable impact of intensifying statin regimen after HT.

Nursing interventions in the treatment of syndrome Takotsubo // Zadaci kardiološke medicinske sestre u lečenju Takotsubo sindroma

Takostube syndrome (TS; broken heart syndrome) is described as transient reversible cardiomyopathy that occurs in older women in most cases as a result of mental or psychological suffering. It is associated with various disorders and it is defined as Takotsubo Syndrome (TS). The clinical picture is similar to acute coronary syndrome, but it must differ from acute ischemic heart disease. Ethiopathological factors have not been fully clarified, but the main role in the development of TS by catecholamine-induced spiking myocardial capillaries or the direct toxicity of catecholamines themselves.There are no strict guidelines in the implementation of health care for patients with TS. Given the great similarity in the clinical picture between acute myocardial infarction and TS, the same procedures and tasks are used in practice as in patients with acute myocardial infarction with ST elevation, while coronarography does not prove to be the opposite. The patient under suspicion of diagnosis of TS is admitted to the coronary unit.Healthcare goals for the treatment of patients with TS are identical to those in acute coronary syndrome and include: pain relief, tension reduction - anxiety, preservation of myocardial function, and prevention and treatment of complications.

(490) - Identification of Hypoxic Cells in Lung Grafts for Future Cell Targeted Therapy for Obliterans Bronchiolitis

Purpose: Ex vivo heart perfusion (EVHP) has been proposed as a means improving heart preservation and expanding the donor pool. Current clinical EVHP protocols involve preservation in an unloaded and non-working state; however, the impact of this approach on the preservation of donor heart function is unknown. We sought to determine if myocardial load during EVHP impacts the preservation of donor heart function. Methods: Donor porcine hearts were perfused ex vivo in a beating state for 12 hours. Loaded hearts (N= 4) were perfused in a working mode (left atrial pressure= 6 mmHg, heart rate= 100 beats/minute) for the entire EVHP interval. Unloaded hearts (N= 4) were briefly transitioned into a working mode at hours 1 (T1), 5 (T5), and 11 (T11) for metabolic and functional assessments, but were otherwise perfused in a resting mode (left atrial pressure= 0 mmHg). Results: Myocardial function (T11 cardiac index (mL/minute/gram): loaded= 6.9±1.0 vs. unloaded= 2.0±1.2, p= 0.02) and mechanical efficiency (T11: loaded= 11±1 vs. unloaded= 2±1 %, p< 0.01) were better preserved in loaded hearts. Myocardial injury (T11 troponin I (ng/mL): loaded= 11.6±0.4 vs. unloaded= 12.1±0.3, p= 0.39) and edema formation (% weight gain: loaded= 14±8 vs. unloaded= 24±3 %, p= 0.15) did not account for these differences. Free fatty acids were rapidly depleted in both groups; however, triglycerides were continually consumed by loaded hearts and secreted by unloaded heats (Figure 1). Conclusion: EVHP in a loaded state improves the preservation of myocardial function. Uncoupling of fatty acid oxidation may contribute to the decline in myocardial function observed in unloaded hearts; however, further research is required to elucidate the mechanism underlying these observations. These results highlight the need for an EVHP device capable of preserving the donor heart in a physiologic working mode.

A whole blood–based perfusate provides superior preservation of myocardial function during ex vivo heart perfusion

Ex vivo heart perfusion (EVHP) provides the opportunity to resuscitate unused donor organs and facilitates assessments of myocardial function that are required to demonstrate organ viability before transplantation. We sought to evaluate the effect of different oxygen carriers on the preservation of myocardial function during EVHP. Twenty-seven pig hearts were perfused ex vivo in a normothermic beating state for 6 hours and transitioned into working mode for assessments after 1 (T1), 3 (T3), and 5 (T5) hours. Hearts were allocated to 4 groups according to the perfusate composition. Red blood cell concentrate (RBC, n = 6), whole blood (RBC+Plasma, n = 6), an acellular hemoglobin-based oxygen carrier (HBOC, n = 8), or HBOC plus plasma (HBOC+Plasma, n = 7) were added to STEEN Solution (XVIVO Perfusion, Goteborg, Sweden) to achieve a perfusate hemoglobin concentration of 40 g/liter. The perfusate composition affected the preservation of systolic (T5 dP/dtmax: RBC+Plasma = 903 ± 99, RBC = 771 ± 77, HBOC+Plasma = 691 ± 82, HBOC = 563 ± 52 mm Hg/sec; p = 0.047) and diastolic (T5 dP/dtmin: RBC+Plasma = -574 ± 48, RBC = -492 ± 63, HBOC+Plasma = -326 ± 32, HBOC = -268 ± 22 mm Hg/sec; p < 0.001) function, and the development of myocardial edema (weight gain: RBC+Plasma = 6.6 ± 0.9, RBC = 6.6 ± 1.2, HBOC+Plasma = 9.8 ± 1.7, HBOC = 16.3 ± 1.9 g/hour; p < 0.001) during EVHP. RBC+Plasma hearts exhibited less histologic evidence of myocyte damage (injury score: RBC+Plasma = 0.0 ± 0.0, RBC = 0.8 ± 0.3, HBOC+Plasma = 2.6 ± 0.2, HBOC = 1.75 ± 0.4; p < 0.001) and less troponin-I release (troponin-I fold-change T1-T5: RBC+Plasma = 7.0 ± 1.7, RBC = 13.1 ± 1.6, HBOC+Plasma = 20.5 ± 1.1, HBOC = 16.7 ± 5.8; p < 0.001). Oxidative stress was minimized by the addition of plasma to RBC and HBOC hearts (oxidized phosphatidylcholine compound fold-change T1-T5: RBC+Plasma = 1.83 ± 0.20 vs RBC = 2.31 ± 0.20, p < 0.001; HBOC+Plasma = 1.23 ± 0.17 vs HBOC = 2.80 ± 0.28, p < 0.001). A whole blood-based perfusate (RBC+Plasma) minimizes injury and provides superior preservation of myocardial function during EVHP. The beneficial effect of plasma on the preservation of myocardial function requires further investigation.

Abstract 22: CXCR4 Expression on Endogenous Bone Marrow Stem/Progenitor Cells is Crucial for Preservation of Myocardial Function After MI

Background: Studies examining the role of bone marrow CXCR4 in the response to myocardial infarction (MI) using the CXCR4 antagonist AMD3100 in animal myocardial infarction (MI) models are inconclusive. Chronic AMD3100 administration exacerbated injury and myocardial dysfunction while bolus injection immediately post-MI reduced size of the injury with improvement of systolic function. Aims: As MI mobilizes bone marrow stem/progenitor cells and immune cells into peripheral blood which then home to injured myocardium to facilitate and impair, respectively, regeneration and healing we were interested in the role of bone marrow CXCR4 on functional recovery, angiogenesis, and cardiomyogenesis. Experimental Approach: To define the role of CXCR4 in the bone marrow we generated chimeras with bone marrow from CXCR4 flox/flox mice. Wild type mice were transplanted with CXCR4 flox/flox or CXCR4 flox/flox UBQ Cre bone marrow cells after a lethal dose of irradiation. CXCR4 deletion was induced 5 weeks after transplant with Tamoxifen. The coronary artery was ligated after another two weeks. Function was evaluated five weeks post MI function by echo and pathology analysis was performed to measure scar size, collagen content, hypertrophy, capillary counts, CSCs counts, angiogenesis and cardiomyogenesis. Results: compared to wild type, mice with CXCR4 KO bone marrow had impaired LV systolic function evaluated 5 weeks post-MI by echocardiography. Morphometric analysis of Masson’s Trichrome stained sections confirmed LV exacerbated chamber enlargement (expansion index), larger scar and decreased infarcted wall thickness in mice with bone marrow cells deficient for CXCR4. More detailed analysis revealed c-kit positive CSC numbers were decreased as were proliferating c-kit CSC indicated by Ki67 staining. Decreased proliferation also correlated with reduced numbers of newly formed myocytes (αsarcomeric actin pos /BrdU pos ). Capillary and arteriole counts were also reduced in infarcted hearts of mice with CXCR4 KO bone marrow compared to wild type. Conclusion: based on these findings we can conclude that CXCR4 is necessary for bone marrow cell homing to infarcted myocardium to preserve LV function, regenerate lost myocardium, and promote angiogenesis.

Selective inhibition of inositol hexakisphosphate kinases (IP6Ks) enhances mesenchymal stem cell engraftment and improves therapeutic efficacy for myocardial infarction.

5-Diphosphoinositol pentakisphosphate (IP7), formed by a family of inositol hexakisphosphate kinases (IP6Ks), has been demonstrated to be a physiologic inhibitor of Akt. IP6K inhibition may increase Akt activation in mesenchymal stem cells (MSCs), resulting in enhanced cardiac protective effect after transplantation. The aim of this study was to investigate the role of IP6Ks for improving MSCs' functional survival and cardiac protective effect after transplantation into infarcted mice hearts. Bone marrow-derived mesenchymal stem cells, isolated from dual-reporter firefly luciferase and enhanced green fluorescent protein positive (Fluc(+)-eGFP(+)) transgenic mice, were preconditioned with IP6Ks inhibitor TNP (0.5, 1, 5, and 10 μmol/L) for 2 h followed by 6 h of hypoxia and serum deprivation (H/SD) injury. TNP concentration dependently significantly decreased IP7 production with increased Akt phosphorylation. Moreover, TNP at 10 μmol/L significantly improved the viability and enhanced the paracrine effect of MSCs after H/SD. Furthermore, MSCs were transplanted into infarcted hearts with or without selective IP6Ks inhibition. Longitudinal in vivo bioluminescence imaging and immunofluorescent staining revealed that TNP pretreatment enhanced the survival of engrafted MSCs, which promoted the anti-apoptotic and pro-angiogenic efficacy of MSCs in vivo. Furthermore, MSC therapy with IP6Ks inhibition significantly decreased fibrosis and preserved heart function. This study demonstrates that inhibition of IP6Ks promotes MSCs engraftment and paracrine effect in infarcted hearts at least in part by down-regulating IP7 production and enhancing Akt activation, which might contribute to the preservation of myocardial function after MI.

Abstract 9321: Selective Inhibition of Inositol Hexakisphosphate Kinases Enhances Mesenchymal Stem Cell Engraftment and Improves Therapeutic Efficacy for Myocardial Infarction

Rationale: 5-diphosphoinositol pentakisphosphate (IP7), formed by a family of inositol hexakis phosphate kinases (IP6Ks), has been demonstrated to be a physiologic inhibitor of Akt. IP6K inhibition may increase Akt activation in mesenchymal stem cells (MSCs), resulting in enhanced cardiac protective effect after transplantation. Objective: To investigate the role of IP6Ks for improving MSCs’ functional survival and cardiac protective effect after transplantation into infarcted mice hearts. Methods and results: Bone marrow-derived mesenchymal stem cells (BMMSCs), isolated from dual-reporter firefly luciferase and enhanced green fluorescent protein positive (Fluc + -eGFP + ) transgenic mice, were preconditioned with IP6Ks inhibitor TNP (0.5μmol/L, 1μmol/L, 5μmol/L, and 10μmol/L) for 2 h followed by 6 hours of hypoxia and serum deprivation (H/SD) injury. TNP dose dependently significantly decreased IP7 production with increased Akt phosphorylation. Moreover,TNP at 10μmol/L significantly improved the viability and enhanced the paracrine effect of MSCs after H/SD. Furthermore, MSCs were transplanted into infarcted hearts with or without selective IP6Ks inhibition. Longitudinal in vivo bioluminescence imaging (BLI) and immunofluorescent staining revealed that TNP pretreatment enhanced the survival of engrafted MSCs, which promoted the anti-apoptotic and pro-angiogenic efficacy of MSCs in vivo . Furthermore, MSCs therapy with IP6Ks inhibition significantly decreased fibrosis and preserved heart function. Conclusion: Inhibition of IP6Ks promotes MSCs engraftment and paracrine effect in infarcted hearts at least in part by down-regulating IP7 production and enhancing Akt activation, which might contribute to the preservation of myocardial function after MI.

A Donor Whole Blood-Based Perfusate Provides Superior Preservation of Myocardial Function During Ex Vivo Heart Perfusion

Discarded hearts from brain-dead donors and donors after circulatory death may represent unutilized sources of organs for transplantation; however, demonstration of adequate myocardial function prior to transplantation is necessary. Ex vivo heart perfusion (EVHP) provides an opportunity for such functional assessment. The optimal method of oxygen delivery to meet the metabolic demands of a heart in working mode during EVHP has not been established. We sought to determine the impact of different oxygen carriers on the preservation of myocardial function during EVHP.

Diacylglycerol kinase α exacerbates cardiac injury after ischemia/reperfusion

Early coronary reperfusion of the ischemic myocardium is a desired therapeutic goal for the preservation of myocardial function. However, reperfusion itself causes additional myocardium injuries. Activation of the diacylglycerol-protein kinase C (DAG-PKC) cascade has been implicated in the cardioprotective effects occurring after ischemia/reperfusion (I/R). DAG kinase (DGK) controls cellular DAG levels by converting DAG to phosphatidic acid, and may act as an endogenous regulator of DAG-PKC signaling. In the present study, we examined the functional role of DGKα in cardiac injury after I/R in in vivo mouse hearts. We generated transgenic mice with cardiac-specific overexpression of DGKα (DGKα-TG). The left anterior descending coronary artery was transiently occluded for 20min and reperfused for 24h in DGKα-TG mice and wild-type littermate (WT) mice. The levels of phosphorylation activity of PKCε, extracellular-signal regulated kinase (ERK) 1/2, and p70 ribosomal S6 kinase (p70S6K) were increased after I/R in WT mouse hearts. However, in DGKα-TG mice, activation of PKCε, ERK1/2, and p70S6K was attenuated compared to WT mice. After 24h, Evans blue/triphenyltetrazolium chloride double staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining showed that DGKα-TG mice had significantly larger myocardial infarctions and larger numbers of TUNEL-positive cardiomyocytes than WT mice. Echocardiography and cardiac catheterization revealed that left ventricular systolic function was more severely depressed in DGKα-TG mice than in WT mice after I/R. These findings suggest that DGKα exacerbates I/R injury by inhibiting the cardioprotective effects of PKCε, ERK1/2, and p70S6K activation.

Exercise Attenuates Renal Dysfunction with Preservation of Myocardial Function in Chronic Kidney Disease

Previous studies have suggested that exercise improves renal and cardiac functions in patients with chronic kidney disease. The aim of this study was to evaluate the effects of long-term aerobic swimming exercise with overload on renal and cardiac function in rats with 5/6 nefrectomy (5/6Nx). Eight Wistar rats were placed into 4 groups: Control (C), Control+Exercise (E), Sedentary 5/6Nx (NxS) and 5/6Nx+Exercise (NxE). The rats were subjected to swimming exercise sessions with overload for 30 min five days per week for five weeks. Exercise reduced the effect of 5/6Nx on creatinine clearance compared to the NxS group. In addition, exercise minimized the increase in mean proteinuria compared to the NxS group (96.9±10.0 vs. 51.4±9.9 mg/24 h; p<0.05). Blood pressure was higher in the NxS and NxE groups compared to the C and E groups (216±4 and 178±3 vs. 123±2 and 124±2 mm Hg, p<0.05). In the 200 glomeruli that were evaluated, the NxS group had a higher sclerosis index than did the NxE group (16% vs. 2%, p<0.05). Echocardiography demonstrated a higher anterior wall of the left ventricle (LV) in diastole in the NxS group compared with the C, E and NxE groups. The NxS group also had a higher LV posterior wall in diastole and systole compared with the E group. The developed isometric tension in Lmax of the heart papillary muscle was lower in the NxS group compared with the C, E and NxE groups. These results suggested that exercise in 5/6Nx animals might reduce the progression of renal disease and lessen the cardiovascular impact of a reduction in renal mass.

Female stem cells are superior to males in preserving myocardial function following endotoxemia

Mesenchymal stem cells (MSCs) may offer therapeutic benefit in the setting of sepsis and endotoxemia. Previous studies suggest that MSCs from female donors may possess better protective capabilities than their male counterparts. The present study examined whether female MSCs may offer a greater protective advantage in the setting of endotoxemic cardiac dysfunction compared with male MSCs. Adult male Sprague-Dawley rats were injected intraperitoneally with LPS and then treated with intraperitoneal injections of either saline, female MSCs, or male MSCs. Hearts and serum were then collected for analysis of myocardial function, myocardial protein, and myocardial and serum cytokines. Compared with male MSC or vehicle-treated animals, female MSC treatment resulted in greater preservation of myocardial function (P < 0.001). Serum and myocardial levels of all measured cytokines were comparable between rats given MSCs from male or female donors but substantially improved over rats given vehicle (P < 0.05). Reduced myocardial inflammation correlated with reduced levels of phosphorylated p38 MAPK expression in the myocardium of animals injected with MSCs of either sex (P < 0.05). The Bcl-xL/Bax ratio was increased to a greater extent following treatment with female MSCs vs. male MSCs (P < 0.05). Intraperitoneal administration of MSCs is effective in limiting myocardial inflammation and dysfunction in the rat endotoxemia model. Compared with treatment with their male counterparts, MSC treatment from female donors is associated with greater cardiac protection against acute endotoxemic injury.

A phase I study of MN-029 (denibulin), a novel vascular-disrupting agent, in patients with advanced solid tumors

MN-029 (denibulin HCl) is a novel vascular-disrupting agent that reversibly inhibits microtubule assembly, resulting in disruption of the cytoskeleton of tumor vascular endothelial cells. This study determined the safety, pharmacokinetics, and acute anti-vascular effects of MN-029. Patients were treated with escalating doses of MN-029 (4.0-225mg/m(2)) administered IV at 3-week intervals. This first-in-human study followed an accelerated titration design, with intra-patient dose escalation. Plasma samples were assayed to determine PK parameters. DCE-MRI scans were acquired at baseline and at 6-8h post-dose. Thirty-four patients received 151 infusions of MN-029. The most common toxicities of MN-029 included nausea and vomiting (which appeared to be dose related), diarrhea, fatigue, headache, and anorexia. No clinically significant myelotoxicity, stomatitis or alopecia was observed. There was no evidence of cumulative toxicity in patients receiving multiple courses of therapy. The cohort at 180mg/m(2) was expanded to six patients due to a reversible episode of acute coronary ischemia, without sequelae and with preservation of myocardial function. Two dose-limiting toxicities occurred at 225mg/m(2), a transient ischemic attack and grade 3 transaminitis, thus ending dose escalation. Pharmacokinetic data indicated dose-related increases in C (max) and AUC values, although substantial inter-subject variability was observed. No objective responses were noted; however, five patients had stable disease ≥6months. A significant linear correlation was found between reduction in K (trans) and exposure to MN-029. MN-029 was generally well tolerated and showed decrease in tumor vascular parameters. The maximum tolerated dose was 180mg/m(2).