Myocardial Capillary Density Research Articles

Intermittent hypoxia changes the interaction of the kinin-VEGF system and impairs myocardial angiogenesis in the hypertrophic heart.

Intermittent hypoxia (IH) is a feature of obstructive sleep apnea (OSA), a condition highly associated with hypertension‐related cardiovascular diseases. Repeated episodes of IH contribute to imbalance of angiogenic growth factors in the hypertrophic heart, which is key in the progression of cardiovascular complications. In particular, the interaction between vascular endothelial growth factor (VEGF) and the kallikrein‐kinin system (KKS) is essential for promoting angiogenesis. However, researchers have yet to investigate experimental models of IH that reproduce OSA, myocardial angiogenesis, and expression of KKS components. We examined temporal changes in cardiac angiogenesis in a mouse IH model. Adult male C57BI/6 J mice were implanted with Matrigel plugs and subjected to IH for 1–5 weeks with subsequent weekly histological evaluation of vascularization. Expression of VEGF and KKS components was also evaluated. After 3 weeks, in vivo myocardial angiogenesis and capillary density were decreased, accompanied by a late increase of VEGF and its type 2 receptor. Furthermore, IH increased left ventricular myocardium expression of the B2 bradykinin receptor, while reducing mRNA levels of B1 receptor. These results suggest that in IH, an unexpected response of the VEGF and KKS systems could explain the reduced capillary density and impaired angiogenesis in the hypoxic heart, with potential implications in hypertrophic heart malfunction.

Endovascular reversal of renovascular hypertension blunts cardiac dysfunction and deformation in swine.

Renovascular hypertension (RVH) induces hemodynamic and humoral aberrations that may impair cardiac function, structure and mechanics, including cardiac twist and deformation. Revascularization of a stenotic renal artery can decrease blood pressure (BP), but its ability to restore cardiac mechanics in RVH remains unclear. We hypothesized that percutaneous transluminal renal angioplasty (PTRA) would improve cardiac function and left ventricular (LV) deformation in swine RVH. Seventeen domestic pigs were studied for 16 weeks: RVH, RVH + PTRA and normal controls (n = 5-6 each). Global LV function was estimated by multidetector computed-tomography, and LV deformation by electrocardiographically triggered MRI tagging at the apical, mid, and basal LV levels. Cardiomyocyte hypertrophy, myocardial capillary density, and fibrosis were evaluated ex vivo. BP and wall thickness were elevated in RVH and decreased by PTRA, yet remained higher than in controls. LV myocardial muscle mass increased in RVH pigs, which also developed diastolic dysfunction, whereas cardiac output increased. Furthermore, both apical rotation and peak torsion angle increased in RVH compared with controls. Ex vivo, RVH induced myocardial fibrosis and vascular rarefaction. PTRA restored cardiac function and alleviated hypertrophy, vascular rarefaction, and fibrosis. PTRA also normalized apical rotation and peak torsion angle, and elevated basal peak radial strain and apical peak radial strain compared with RVH. In addition to cardiac LV adaptive hypertrophy and diastolic dysfunction, short-term RVH causes cardiac deformation. Despite only partial improvement in BP, PTRA effectively restored cardiac function and reversed abnormal mechanics. Hence, renal revascularization may be a useful strategy to preserve cardiac function in RVH.

The Effect of Eight Weeks of Moderate-Intensity Endurance Training on Myocardial Capillary Density, Ejection Fraction and Left Ventricular Shortening Fraction in Male Rats with Myocardial Infarction

The Effect of Eight Weeks of Moderate-Intensity Endurance Training on Myocardial Capillary Density, Ejection Fraction and Left Ventricular Shortening Fraction in Male Rats with Myocardial Infarction

Beta 1 adrenoceptor blockade promotes angiogenesis in hypertrophied myocardium of transverse aortic constricted mice.

Left ventricular hypertrophy (LVH) is an adaptive structural remodelling consequent to uncontrolled blood pressure. Impaired angiogenesis plays a vital role in transiting LVH into cardiac failure. Catecholamines modulate myocardial function through beta adrenoceptors, and their blockers (β-AR) reduce cardiovascular morbidity and mortality by decelerating the LVH progression. Nonetheless, the effect of β-AR blockers on myocardial vascular bed remains largely obscure. Hence, this study is focussed on analysing the possible outcomes of β-AR blockers on myocardial vascular remodelling using a surgically induced LVH mice model. Transverse aortic constricted mice and sham-operated mice were administered with metoprolol at a dose of 30mg/kg/d for 60days and myocardial vascular endothelial growth factor (VEGF) alpha levels, GSH/GSSG ratio, myocardial protein carbonyl content, hypertrophy index and global myocardial function, trans-aortic fluid dynamics and expression pattern of angiopoietin-1 and VEGF alpha were assessed. These findings were further confirmed by histochemical analysis for myocardial capillary density, perivascular fibrosis ratio and intimal thickening. Sub- chronic β-AR blockade reduced the oxidative stress, hypertrophic index, intimal thickening and perivascular fibrosis ratio. A marked increase in myocardial VEGF, angiopoietin 1, global myocardial function and myocardial capillary density was also observed. There was a reduction in the LVH and upregulation of myocardial angiogenesis concluding that β-AR blockers prevent adverse vascular remodelling which might underlie its concealed mechanism of action.

Qiliqiangxin Improves Cardiac Function through Regulating Energy Metabolism via HIF-1α-Dependent and Independent Mechanisms in Heart Failure Rats after Acute Myocardial Infarction.

The present study is aimed at investigating whether Qiliqiangxin (QL) could regulate myocardial energy metabolism in heart failure rats after acute myocardial infarction (AMI) and further exploring the underlying mechanisms. AMI was established by ligating the left anterior descending coronary artery in adult male SD rats. AMI rats with ejection fraction (EF) < 50% at two weeks after the operation were chosen as heart failure rats for the main study. Rats were randomized into the sham, MI, MI+QL, and MI+QL+2-MeOE2 groups. The results showed that compared with the MI group, QL significantly improved cardiac function, reduced serum NT-proBNP level, and alleviated myocardial fibrosis. QL also increased myocardial capillary density by upregulated protein expressions of vascular endothelial growth factor (VEGF) and CD31 by regulating the HIF-1α/VEGF pathway. Moreover, QL promoted ATP production, glucose uptake, and glycolysis by upregulating HIF-1α and a series of glycolysis-relevant enzymes in a HIF-1α-dependent manner. QL also improved myocardial glucose oxidation enzyme expression and free fatty acid uptake by a HIF-1α-independent pathway. Our results indicate that QL treatment improves cardiac function through regulating glucose uptake, FFA uptake, and key enzymes of energy metabolism via HIF-1α-dependent and independent mechanisms.

Intravital Multiphoton Microscopy of the Beating Mouse Heart Reveals Altered Cardiomyocyte Contraction Dynamics and Increased Microvascular Patrolling by Leukocytes during Cardiac Hypertrophy

BackgroundThe study of functional cardiomyocyte adaptation and inflammatory cell behavior at the micro‐scale in vivo has been challenging due to limited imaging tools. We recently developed intravital multiphoton microscopy (MPM) methods that enable visualization and quantification of cardiac dynamics at the cell and micro‐vessel level throughout the cardiac cycle. We aimed to determine the dynamic cellular changes that occur due to high fat diet (HFD) induced hypertrophy using intravital cardiac MPM.MethodsApoE−/− C57Bl6 mice started a HFD at 6 weeks of age (ApoE−/−‐HFD, n=11), while age‐matched wild‐type mice were fed a normal chow diet (WT‐ND, n=10). At 26‐weeks, mice were assessed by cardiac echocardiography and intravital MPM in the intact beating heart. Intravenous injections of rhodamine‐6G (R6g) labeled cardiomyocytes and leukocytes, and Texas‐Red dextran labeled vasculature during intravital MPM. 3D volumes were reconstructed throughout the cardiac cycle to quantify cell motion using automated algorithms for cell displacement and regional deformation. Post‐mortem immuno‐histology were performed for myocardial macrophages (CD68), capillary density and cross‐sectional area (wheat‐germ‐agglutin).ResultsApoE−/−‐HFD hearts underwent hypertrophy compared to WT‐ND with increased heart weight‐to‐tibial length ratio (13±1.1 vs 10±0.8), left ventricle wall thickness (1.13±0.06 mm vs 1.07±0.03 mm) and myocyte cross‐sectional area (387±22.1 mm2 vs 278±16.6 mm2, p&lt;0.05 for all), while ejection fraction remained preserved (59±3% vs 66±3%). Intravital MPM demonstrated that cardiomyocytes move a greater total distance during each cardiac cycle in ApoE−/−‐HFD vs WT‐ND. Maximum displacement in the apex‐base and anterior‐posterior directions increased by 56% in ApoE−/−‐HFD compared to WT‐ND (32±11 mm vs 18±6 mm), whereas regional absolute deformation remains similar between groups. R6g+ leukocytes were visible moving in capillaries. The incidence of patrolling behavior (defined as slow moving cells, visible for longer than one heartbeat) increased in capillaries of ApoE−/−‐HFD compared to WT‐ND (3.4±0.5/min vs 0.12±0.1/min, p&lt;0.01), while the incidence of flowing (visible for less than one heartbeat) and non‐flowing (visible for 500 heartbeats) remained similar. Myocardial CD68+ macrophages increased (780±121/mm2 vs 89±20/mm2, p&lt;0.0001) and capillary density decreased (3271±167/mm2 vs 3886±105/mm2, p=0.0067) in ApoE−/ −‐HFD hearts compared to WT‐ND in post‐mortem sections.ConclusionIntravital cardiac MPM provides a new perspective to study cardiac hypertrophy by capturing the simultaneous contributions of inflammatory cells and cardiomyocyte function in the beating heart. These results suggest that hypertrophied cardiomyocytes increase overall tissue motion to compensate for unchanged cardiomyocyte contraction to maintain a healthy ejection fraction. Increased capillary leukocyte patrolling behavior may promote myocardial hypertrophy.Support or Funding InformationAHA17POST33680127, NSFDBI1707312, NIH5R21EB02469403

CD133+Exosome Treatment Improves Cardiac Function after Stroke in Type 2 Diabetic Mice.

Cardiac complications post-stroke are common, and diabetes exacerbates post-stroke cardiac injury. In this study, we tested whether treatment with exosomes harvested from human umbilical cord blood derived CD133+ cells (CD133+Exo) improves cardiac function in type 2 diabetes mellitus (T2DM) stroke mice. Adult (3-4m), male, BKS.Cg-m+/+Leprdb/J (db/db, T2DM) and non-DM (db+) mice were randomized to sham or photothrombotic stroke groups. T2DM-stroke mice were treated with phosphate-buffered saline (PBS) or CD133+Exo (20μg, i.v.) at 3days after stroke. T2DM sham and T2DM+CD133+Exo treatment groups were included as controls. Echocardiography was performed, and mice were sacrificed at 28days after stroke. Cardiomyocyte hypertrophy, myocardial capillary density, interstitial fibrosis, and inflammatory factor expression were measured in the heart. MicroRNA-126 expression and its target gene expression were measured in the heart. T2DM mice exhibit significant cardiac deficits such as decreased left ventricular ejection fraction (LVEF) and shortening fraction (LVSF), increased left ventricular diastolic dimension (LVDD), and reduced heart rate compared to non-DM mice. Stroke in non-DM and T2DM mice significantly decreases LVEF compared to non-DM and T2DM-sham, respectively. Cardiac dysfunction is worse in T2DM-stroke mice compared to non-DM-stroke mice. CD133+Exo treatment of T2DM-stroke mice significantly improves cardiac function identified by increased LVEF and decreased LVDD compared to PBS treated T2DM-stroke mice. In addition, CD133+Exo treatment significantly decreases body weight and blood glucose but does not decrease lesion volume in T2DM-stroke mice. CD133+Exo treatment of T2DM mice significantly decreases body weight and blood glucose but does not improve cardiac function. CD133+Exo treatment in T2DM-stroke mice significantly decreases myocardial cross-sectional area, interstitial fibrosis, transforming growth factor beta (TGF-β), numbers of M1 macrophages, and oxidative stress markers 4-HNE (4-hydroxynonenal) and NADPH oxidase 2 (NOX2) in heart tissue. CD133+Exo treatment increases myocardial capillary density in T2DM-stroke mice as well as upregulates endothelial cell capillary tube formation in vitro. MiR-126 is highly expressed in CD133+Exo compared to exosomes derived from endothelial cells. Compared to PBS treatment, CD133+Exo treatment significantly increases miR-126 expression in the heart and decreases its target gene expression such as Sprouty-related, EVH1 domain-containing protein 1 (Spred-1), vascular cell adhesion protein (VCAM), and monocyte chemoattractant protein 1 (MCP1) in the heart of T2DM-stroke mice. CD133+Exo treatment significantly improves cardiac function in T2DM-stroke mice. The cardio-protective effects of CD133+Exo in T2DM-stroke mice may be attributed at least in part to increasing miR-126 expression and decreasing its target protein expression in the heart, increased myocardial capillary density and decreased cardiac inflammatory factor expression.

Selective intrarenal delivery of mesenchymal stem cell-derived extracellular vesicles attenuates myocardial injury in experimental metabolic renovascular disease.

Extracellular vesicles (EVs) deliver genes and proteins to recipient cells, and mediate paracrine actions of their parent cells. Intrarenal delivery of mesenchymal stem cell (MSC)-derived EVs preserves stenotic-kidney function and reduces release of pro-inflammatory cytokines in a swine model of coexisting metabolic syndrome (MetS) and renal artery stenosis (RAS). We hypothesized that this approach is also capable of blunting cardiac injury and dysfunction. Five groups of pigs were studied after 16weeks of diet-induced MetS and RAS (MetS + RAS), MetS and MetS + RAS treated 4weeks earlier with a single intrarenal delivery of EVs-rich fraction harvested from autologous adipose tissue-derived MSCs, and lean and MetS Shams. Cardiac structure, function, and myocardial oxygenation were assessed in vivo using imaging, and cardiac inflammation, senescence, and fibrosis ex vivo. Inflammatory cytokine levels were measured in circulating and renal vein blood. Intrarenal EV delivery improved stenotic-kidney glomerular filtration rate and renal blood flow, and decreased renal release of monocyte-chemoattractant protein-1 and interleukin-6. Furthermore, despite unchanged systemic hemodynamics, intrarenal EV delivery in MetS + RAS normalized cardiac diastolic function, attenuated left ventricular remodeling, cellular senescence and inflammation, and improved myocardial oxygenation and capillary density in MetS + RAS. Intrarenal delivery of MSC-derived EVs blunts myocardial injury in experimental MetS + RAS, possibly related to improvement in renal function and systemic inflammatory profile. These observations underscore the central role of inflammation in the crosstalk between the kidney and heart, and the important contribution of renal function to cardiac structural and functional integrity in coexisting MetS and RAS.

NADPH oxidase-4 promotes eccentric cardiac hypertrophy in response to volume overload.

AimsChronic pressure or volume overload induce concentric vs. eccentric left ventricular (LV) remodelling, respectively. Previous studies suggest that distinct signalling pathways are involved in these responses. NADPH oxidase-4 (Nox4) is a reactive oxygen species-generating enzyme that can limit detrimental cardiac remodelling in response to pressure overload. This study aimed to assess its role in volume overload-induced remodelling.Methods and resultsWe compared the responses to creation of an aortocaval fistula (Shunt) to induce volume overload in Nox4-null mice (Nox4−/−) vs. wild-type (WT) littermates. Induction of Shunt resulted in a significant increase in cardiac Nox4 mRNA and protein levels in WT mice as compared to Sham controls. Nox4−/− mice developed less eccentric LV remodelling than WT mice (echocardiographic relative wall thickness: 0.30 vs. 0.27, P < 0.05), with less LV hypertrophy at organ level (increase in LV weight/tibia length ratio of 25% vs. 43%, P < 0.01) and cellular level (cardiomyocyte cross-sectional area: 323 µm2 vs. 379 μm2, P < 0.01). LV ejection fraction, foetal gene expression, interstitial fibrosis, myocardial capillary density, and levels of myocyte apoptosis after Shunt were similar in the two genotypes. Myocardial phospho-Akt levels were increased after induction of Shunt in WT mice, whereas levels decreased in Nox4−/− mice (+29% vs. −21%, P < 0.05), associated with a higher level of phosphorylation of the S6 ribosomal protein (S6) and the eIF4E-binding protein 1 (4E-BP1) in WT compared to Nox4−/− mice. We identified that Akt activation in cardiac cells is augmented by Nox4 via a Src kinase-dependent inactivation of protein phosphatase 2A.ConclusionEndogenous Nox4 is required for the full development of eccentric cardiac hypertrophy and remodelling during chronic volume overload. Nox4-dependent activation of Akt and its downstream targets S6 and 4E-BP1 may be involved in this effect.

P3507Heterozygous cardiomyocyte-specific deletion of ErbB4 sensitizes to development of pregnancy-related cardiomyopathy

Abstract Background Peripartum cardiomyopathy (PPCM) is a potentially life-threatening disease in women without known cardiovascular disease; PPCM is characterized by left ventricular (LV) systolic dysfunction towards the end of pregnancy and/or in the first months postpartum. The underlying mechanisms of PPCM are incompletely understood, but there is recent evidence that impaired cardiomyocyte expression of the tyrosine kinase ErbB4 receptor plays a role. ErbB4 is the main receptor of neuregulin-1, a protective and regenerative paracrine factor in the heart. Homozygous deletion of ErbB4 is lethal. Purpose To test the hypothesis that mice with heterozygous (HZ) cardiomyocyte-specific deletion of ErbB4 (ErbB4+/−) are more susceptible to PPCM. Methods Cardiac morphology and function was evaluated by echocardiography with a Vevo 2100 Imaging System during 2 pregnancies and 6 weeks postpartum (n=7–9) or during non-pregnant control conditions in HZ (ErbB4+/−) and wild type controls (n=9–10). Then, hearts were excised for analyses of myocardial fibrosis, macrophage infiltration, capillary density and cardiomyocyte cross sectional area. Results When compared to pregnant wild type controls, pregnant ErbB4+/− mice developed significant LV dilatation (2 weeks after the 2nd delivery: LVIDd +16% ± 2%, p&lt;0.05) and dysfunction (6 weeks after the 2nd delivery: EF −23% ± 3%, p&lt;0.001), increased heart to body weight ratio (+7% ± 4%, p&lt;0.05) and increased cardiomyocyte cross sectional area (+28% ± 7%, p&lt;0.01). Non-pregnant ErbB4+/− mice also developed LV dilatation and dysfunction, albeit slower than pregnant ErbB4+/− mice. On histology, however, myocardial tissue of pregnant ErbB4+/− mice did not show macrophage infiltration, neither fibrosis, nor reduced capillary density. Conclusions Heterozygous cardiomyocyte-specific deletion of ErbB4 sensitizes to peripartum LV dilatation and cardiomyocyte hypertrophy and systolic dysfunction without profound cardiac injury, features that are frequently present in PPCM patients and may explain their high chance for recovery. These data reinforce a compensatory role for neuregulin-ErbB4 signaling during hemodynamic overload, and confirm that this signaling pathway is important to protect the maternal heart during peripartum stress. Acknowledgement/Funding Fund scientific research Flanders; University Antwerp

Primary Cardiac Angiosarcoma: Authors' Perspective Following Synthesis of Available Literature

Why are malignant primary cardiac tumors so rare? Is it because of the specialized cardiac muscle cells or the large number of mitochondria per cell? Is it because cardiac muscle is the most aerobic organ of the body and its myocardial capillary density is at a 1:1 ratio, which is 10-fold higher than that of the skeletal muscle? There is overwhelming evidence regarding the benefits of aerobic exercise in prevention of many types of cancer and their associated sequelae. However, there appears to be an evidence gap that needs to be filled. Is there a link between the rare occurrence of primary cardiac cancers in terms of the oxygenation of cardiac muscle tissue and the benefits of aerobic exercise that could provide a new area of research for the primary prevention of cancer? Discussion of these questions was the impetus for the authors to conduct a literature search and then synthesize the review findings. This perspective aims to explore currently available knowledge and gaps in available evidence to understand areas in which physical therapists may impact the varied levels of preventive intervention on primary malignant cardiac cancers. The 35 presenting symptoms and medical history reported in the literature may provide a basis for correlation with other genetic and epigenetic factors to explore along our journey for answers. The physical therapy profession is well positioned to promote healthy behaviors and provide patient education to reduce risk factors and prevent and treat noncommunicable diseases consistent with a biopsychosocial paradigm.

Alterations in Myocardial Oxygen Balance, Anaerobic Metabolism and Diastolic Dysfunction in Exercising Swine with Multiple Comorbidities

IntroductionMultiple comorbidities, including diabetes mellitus (DM), hypercholesterolemia and chronic kidney disease (CKD) are associated with diastolic dysfunction. These risk factors also cause coronary microvascular dysfunction leading to impaired myocardial perfusion and ischemia with non‐obstructive coronary artery disease (INOCA). Recently a link has been proposed between INOCA and HFpEF. We investigated the detrimental effects of DM, CKD and high fat diet (HFD) on myocardial function and perfusion.HypothesisProlonged exposure to multiple comorbidities in swine leads to diastolic dysfunction, associated with impaired myocardial perfusion and anaerobic metabolism.MethodsDM (streptozotocin 3×50mg/kg i.v.) and CKD (renal embolization) were induced in 7 female swine fed a high fat diet (DM+HFD+CKD), while 10 female healthy swine on normal diet served as controls (CON). After 6 months, myocardial perfusion and oxygen balance were studied at rest and during treadmill exercise. At sacrifice PV‐loop measurements and histology were performed.ResultsDM+HFD+CKD animals showed hyperglycemia (glucose: 19.2±1.5 vs 7.5±0.6 mmol/L), renal dysfunction (glomerular filtration rate: 132±14 vs 197±10 ml/min) and hypercholesterolemia (total cholesterol: 8.28±0.86 vs 1.65±0.06 mmol/l, all P&lt;0.05). DM+HFD+CKD had an increased EDPVR (0.14±0.02 vs 0.09±0.01 mmHg/mL) with preserved ejection fraction, a lower cardiac index compared to CON at similar levels of exercise (fig A). Left ventricular myocardial capillary density was decreased (1229±59 vs 1502±86 #/mm2) and collagen content was increased (9.6±1.9 vs 5.0±0.6 %). Their myocardium required more oxygen for similar levels of cardiac work, suggesting cardiac inefficiency (fig B). Furthermore, they showed a lower myocardial oxygen delivery (fig C), forcing the myocardium to increase its oxygen extraction (fig D) leading to lower coronary venous oxygen saturation (fig E) both at rest and during exercise. This was accompanied by a decrease in myocardial lactate consumption at the same lactate supply as in CON (fig F), suggestive of anaerobic metabolism. Importantly, DM+HFD+CKD showed no coronary atherosclerosis.ConclusionMultiple co‐morbidities in swine result in severe perturbations in myocardial oxygen balance and anaerobic metabolism in the absence of significant atherosclerosis, indicating severe coronary microvascular dysfunction co‐occurring with diastolic dysfunction.Support or Funding InformationThis study was supported by grants from the European Commission FP7‐Health‐2010 grant MEDIA‐261409, the Netherlands CardioVascular Research Initiative: an initiative with support of the Dutch Heart Foundation [CVON2012‐08 (PHAEDRA), CVON2014‐11 (RECONNECT)]. Cardiac index (CI) of DM+HFD+CKD was lower than in CON swine (A). Myocardium of DM+HFD+CKD swine shows increased oxygen consumption (MVO2) for the same level of cardiac work (B), has a lower myocardial oxygen delivery (MDO2, C) and a higher oxygen extraction (MEO2, D), which results in lower coronary venous oxygen saturation (cv SaO2, E). Lower myocardial lactate consumption (MVlactate) at a given level of myocardial lactate delivery (MDlactate, F). *p&lt;0.05 DM+HFD+CKD versus CONimageCardiac index (CI) of DM+HFD+CKD was lower than in CON swine (A). Myocardium of DM+HFD+CKD swine shows increased oxygen consumption (MVO2) for the same level of cardiac work (B), has a lower myocardial oxygen delivery (MDO2, C) and a higher oxygen extraction (MEO2, D), which results in lower coronary venous oxygen saturation (cv SaO2, E). Lower myocardial lactate consumption (MVlactate) at a given level of myocardial lactate delivery (MDlactate, F). *p&lt;0.05 DM+HFD+CKD versus CONThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Alterations in myocardial connexin-43 and matrix metalloproteinase-2 signaling in response to pregnancy and oxygen deprivation of Wistar rats: a pilot study 1.

Two important aspects of cardiac adaptive response to pregnancy have been studied in normal as well as hypoxic conditions: (1) intercellular signaling mediated by myocardial connexin-43 (Cx43) that is crucial to synchronize heart function; (2) extracellular signaling mediated by matrix metalloproteinase-2 (MMP-2) that is an early marker of extracellular matrix remodeling. Myocardial Cx43 distribution and functional capillary density were determined as well. Hypoxia was induced by exposure of rats to 10.5% O2 and 89.5% N2 in a hermetically sealed chamber. Findings showed that pregnancy resulted in a significant increase of Cx43 protein expression, its functional phosphorylated forms, and enhanced capillary density while did not affect either expression of total MMP-2 or its activity. Maternal hypoxia for 12 or 16 h did not affect elevated Cx43 but enhanced its distribution on lateral sides of the cardiomyocytes. In contrast, hypoxia of nonpregnant rats resulted in upregulation of Cx43, its lateral distribution, and enhanced capillary density. Hypoxia did not affect myocardial MMP-2 either in pregnant or nonpregnant rats. Cardiac adaptive response to pregnancy is accompanied by enhanced Cx43 without changes in MMP-2 signaling. Pregnant rat heart is tolerant to short-term hypoxemia, while nonpregnant rat heart reacts by upregulation of Cx43 and increased capillary density.

Effective Treatment of Diabetic Cardiomyopathy and Heart Failure with Reconstituted HDL (Milano) in Mice.

The risk of heart failure (HF) is prominently increased in patients with type 2 diabetes mellitus. The objectives of this study were to establish a murine model of diabetic cardiomyopathy induced by feeding a high-sugar/high-fat (HSHF) diet and to evaluate the effect of reconstituted HDLMilano administration on established HF in this model. The HSHF diet was initiated at the age of 12 weeks and continued for 16 weeks. To investigate the effect of reconstituted HDLMilano on HF, eight intraperitoneal administrations of MDCO-216 (100 mg/kg protein concentration) or of an identical volume of control buffer were executed with a 48-h interval starting at the age of 28 weeks. The HSHF diet-induced obesity, hyperinsulinemia, and type 2 diabetes mellitus. Diabetic cardiomyopathy was present in HSHF diet mice as evidenced by cardiac hypertrophy, increased interstitial and perivascular fibrosis, and decreased myocardial capillary density. Pressure-volume loop analysis indicated the presence of both systolic and diastolic dysfunction and of decreased cardiac output in HSHF diet mice. Treatment with MDCO-216 reversed pathological remodelling and cardiac dysfunction and normalized wet lung weight, indicating effective treatment of HF. No effect of control buffer injection was observed. In conclusion, reconstituted HDLMilano reverses HF in type 2 diabetic mice.

Microvascular Rarefaction and Heart Failure With Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is characterized by diastolic dysfunction and is commonly seen in the elderly and diabetic and hypertensive patients. Despite its rising prevalence, the pathophysiology of HFpEF is poorly understood and its optimal treatment remains undefined. Recent clinical studies indicate that coronary microvascular rarefaction (reduced myocardial capillary density) with reduced coronary flow reserve (CFR) is a major contributor to diastolic dysfunction in HFpEF patients. On a molecular level, endothelial cells (EC) are dependent on glycolysis for supporting their functions and vascular homeostasis. Sirtuin 3 (SIRT3) has a critical role in the regulation of endothelial glycolytic metabolism and thus affects angiogenesis. Disruption of SIRT3-mediated EC metabolism and impairment of angiogenesis may promote cardiomyocyte hypoxia and myocardial fibrosis, leading to diastolic dysfunction and HFpEF. This review summarizes current knowledge of SIRT3 in EC metabolism, coronary microvascular rarefaction and HFpEF.

Selective deletion of endothelial cell calpain in mice reduces diabetic cardiomyopathy by improving angiogenesis.

The role of non-cardiomyocytes in diabetic cardiomyopathy has not been fully addressed. This study investigated whether endothelial cell calpain plays a role in myocardial endothelial injury and microvascular rarefaction in diabetes, thereby contributing to diabetic cardiomyopathy. Endothelial cell-specific Capns1-knockout (KO) mice were generated. Conditions mimicking prediabetes and type 1 and type 2 diabetes were induced in these KO mice and their wild-type littermates. Myocardial function and coronary flow reserve were assessed by echocardiography. Histological analyses were performed to determine capillary density, cardiomyocyte size and fibrosis in the heart. Isolated aortas were assayed for neovascularisation. Cultured cardiac microvascular endothelial cells were stimulated with high palmitate. Angiogenesis and apoptosis were analysed. Endothelial cell-specific deletion of Capns1 disrupted calpain 1 and calpain 2 in endothelial cells, reduced cardiac fibrosis and hypertrophy, and alleviated myocardial dysfunction in mouse models of diabetes without significantly affecting systemic metabolic variables. These protective effects of calpain disruption in endothelial cells were associated with an increase in myocardial capillary density (wild-type vs Capns1-KO 3646.14 ± 423.51 vs 4708.7 ± 417.93 capillary number/high-power field in prediabetes, 2999.36 ± 854.77 vs 4579.22 ± 672.56 capillary number/high-power field in type 2 diabetes and 2364.87 ± 249.57 vs 3014.63 ± 215.46 capillary number/high-power field in type 1 diabetes) and coronary flow reserve. Ex vivo analysis of neovascularisation revealed more endothelial cell sprouts from aortic rings of prediabetic and diabetic Capns1-KO mice compared with their wild-type littermates. In cultured cardiac microvascular endothelial cells, inhibition of calpain improved angiogenesis and prevented apoptosis under metabolic stress. Mechanistically, deletion of Capns1 elevated the protein levels of β-catenin in endothelial cells of Capns1-KO mice and constitutive activity of calpain 2 suppressed β-catenin protein expression in cultured endothelial cells. Upregulation of β-catenin promoted angiogenesis and inhibited apoptosis whereas knockdown of β-catenin offset the protective effects of calpain inhibition in endothelial cells under metabolic stress. These results delineate a primary role of calpain in inducing cardiac endothelial cell injury and impairing neovascularisation via suppression of β-catenin, thereby promoting diabetic cardiomyopathy, and indicate that calpain is a promising therapeutic target to prevent diabetic cardiac complications.

Human Neonatal Thymus Mesenchymal Stem/Stromal Cells and Chronic Right Ventricle Pressure Overload.

Right ventricle (RV) failure secondary to pressure overload is associated with a loss of myocardial capillary density and an increase in oxidative stress. We have previously found that human neonatal thymus mesenchymal stem cells (ntMSCs) promote neovascularization, but the ability of ntMSCs to express the antioxidant extracellular superoxide dismutase (SOD3) is unknown. We hypothesized that ntMSCs express and secrete SOD3 as well as improve survival in the setting of chronic pressure overload. To evaluate this hypothesis, we compared SOD3 expression in ntMSCs to donor-matched bone-derived MSCs and evaluated the effect of ntMSCs in a rat RV pressure overload model induced by pulmonary artery banding (PAB). The primary outcome was survival, and secondary measures were an echocardiographic assessment of RV size and function as well as histological studies of the RV. We found that ntMSCs expressed SOD3 to a greater degree as compared to bone-derived MSCs. In the PAB model, all ntMSC-treated animals survived to the study endpoint whereas control animals had significantly decreased survival. Treatment animals had significantly less RV fibrosis and increased RV capillary density as compared to controls. We conclude that human ntMSCs demonstrate a therapeutic effect in a model of chronic RV pressure overload, which may in part be due to their antioxidative, antifibrotic, and proangiogenic effects. Given their readily available source, human ntMSCs may be a candidate cell therapy for individuals with congenital heart disease and a pressure-overloaded RV.

Fetal hypoxemia causes abnormal myocardial development in a preterm ex utero fetal ovine model.

In utero hypoxia is a major cause of neonatal morbidity and mortality and predisposes to adult cardiovascular disease. No therapies exist to correct fetal hypoxia. In a new ex utero fetal support system, we tested the hypothesis that hypoxemic support of the fetus impairs myocardial development, whereas normoxic support allows normal myocardial development. Preterm fetal lambs were connected via umbilical vessels to a low-resistance oxygenator and placed in a sterile-fluid environment. Control normoxic fetuses received normal fetal oxygenation, and hypoxemic fetuses received subphysiologic oxygenation. Fetuses with normal in utero development served as normal controls. Hypoxemic fetuses exhibited decreased maximum cardiac output in both ventricles, diastolic function, myocyte and myocyte nuclear size, and increased myocardial capillary density versus control normoxic fetuses. There were no differences between control normoxic fetuses in the fetal support system and normal in utero controls. Chronic fetal hypoxemia resulted in significant abnormalities in myocyte architecture and myocardial capillary density as well as systolic and diastolic cardiac function, whereas control fetuses showed no differences. This ex utero fetal support system has potential to become a significant research tool and novel therapy to correct fetal hypoxia.

Cardio-omentopexy Reduces Cardiac Fibrosis and Heart Failure After Experimental Pressure Overload

The pedicled greater omentum has been shown to offer benefit in ischemic heart disease for both animal models and human patients. The impact of cardio-omentopexy in a pressure overload model of left ventricular hypertrophy (LVH) is unknown. LVH was created in rats by banding the ascending aorta after right thoracotomy (n= 23). Sham surgery was performed in 12 additional rats. Six weeks after banding, surviving LVH rats were assigned to cardio-omentopexy by left thoracotomy (LVH+Om, n= 8) or sham left thoracotomy (LVH, n= 8). Sham rats also underwent left thoracotomy for cardio-omentopexy (Sham+Om, n= 6); the remaining rats underwent sham left thoracotomy (Sham, n= 6). Echocardiography 10 weeks after cardio-omentopexy revealed LV end-systolic diameter, cardiomyocyte diamter, and myocardial fibrosis in the LVH group were significantly increased compared with the LVH+Om, Sham+Om, and Sham groups (p < 0.01). LV ejection fraction of the LVH group was lower than the LVH+Om group (p < 0.01). Gene expression analysis revealed significantly lower levels of sarcoendoplasmic reticulum calcium adenosine triphosphatase 2b in LVH rats than in the LVH+Om, Sham+Om, and Sham groups (p < 0.01). In contrast, collagen type 1 α 1 chain, lysyl oxidase-like protein 1, nuclear protein-1, and transforming growth factor- β1 in the LVH group were significantly higher than in the LVH+Om cohort (p < 0.01), consistent with a reduced fibrotic phenotype after omentopexy. Lectin staining showed myocardial capillary density of the LVH group was significantly lower than all other groups (p < 0.01). Cardio-omentopexy reduced cardiac dilation, contractile dysfunction, cardiomyocyte hypertrophy, and myocardial fibrosis, while maintaining other molecular indicators of contractile function in this LVH model.

High thoracic sympathetic block improves coronary microcirculation disturbance in rats with chronic heart failure

IntroductionCoronary microcirculation disturbance plays an important role in chronic heart failure (CHF). High thoracic sympathetic block (HTSB) is effective to treat CHF, but its impact on coronary microcirculation is unclear. MethodsForty male Wistar rats were subcutaneously injected with isoproterenol (340 mg/kg) for 2 days. Eight weeks later, 24 surviving rats were randomized to the CHF and HTSB groups and 10 rats were used as the control group. 50 μl of saline and ropivacaine (0.2%) were epidurally infused everyday in the CHF and HTSB group respectively. Four weeks later, echocardiography and pathological and ultrastructural examination, capillary histochemical staining and vascular endothelial growth factor (VEGF) immunohistochemical staining in left ventricular (LV) subendocardial myocardium were performed. ResultsCompared with the control group, LV dilation and dysfunction, myocardial focal necrosis, capillary spasm appeared in the CHF group. HTSB ameliorated LV dilation and dysfunction, myocardial necrosis and capillary spasm. Rats in the CHF group had less myocardial capillary density and more VEGF expression than in the control group (1591 ± 99 vs. 1972 ± 118/mm2, 0.62 ± 0.13 vs. 0.33 ± 0.10 optic density, all p < 0.05). Myocardial capillary density (1782 ± 96/mm2) was more and VEGF expression (0.47 ± 0.12 optic density) was less in the HTSB group than in the CHF group (all p < 0.05). ConclusionHTSB improves coronary microcirculation disturbance in CHF, which may contribute to reversing myocardial remodeling and dysfunction. HTSB stimulates myocardial capillary growth independent of VEGF.