Acacetin suppresses the electrocardiographic and arrhythmic manifestations of the J wave syndromes.

BACKGROUND: J wave syndromes (JWS), including Brugada (BrS) and early repolarization syndromes (ERS), are associated with increased risk for life-threatening ventricular arrhythmias. Pharmacologic approaches to therapy are currently very limited. Here, we evaluate the effects of the natural flavone acacetin. METHODS: The effects of acacetin on action potential (AP) morphology and transient outward current (Ito) were first studied in isolated canine RV epicardial myocytes using whole-cell patch clamp techniques. Acacetin's effects on transmembrane APs, unipolar electrograms and transmural ECGs were then studied in isolated coronary-perfused canine RV and LV wedge preparations as well as in whole-heart, Langendorff-perfused preparations from which we recorded a 12 lead ECG and unipolar electrograms. Using floating glass microelectrodes we also recorded transmembrane APs from the RVOT of the whole-heart model. The Ito agonist NS5806, sodium channel blocker ajmaline, calcium channel blocker verapamil or hypothermia (32°C) were used to pharmacologically mimic the genetic defects and conditions associated with JWS, thus eliciting prominent J waves and provoking VT/VF. RESULTS: Acacetin (5-10 µM) reduced Ito density, AP notch and J wave area and totally suppressed the electrocardiographic and arrhythmic manifestation of both BrS and ERS, regardless of the experimental model used. In wedge and whole-heart models of JWS, increasing Ito with NS5806, decreasing INa or ICa (with ajmaline or verapamil) or hypothermia all resulted in accentuation of epicardial AP notch and ECG J waves, resulting in characteristic BrS and ERS phenotypes. Phase 2-reentrant extrasystoles originating from the RVOT triggered VT/VF. The J waves in leads V1 and V2 were never associated with a delay of RVOT activation and always coincided with the appearance of the AP notch recorded from RVOT epicardium. All repolarization defects giving rise to VT/VF in the BrS and ERS models were reversed by acacetin, resulting in total suppression of VT/VF. CONCLUSIONS: We present experimental models of BrS and ERS capable of recapitulating all of the ECG and arrhythmic manifestations of the JWS. Our findings provide definitive support for the repolarization but not the depolarization hypothesis proposed to underlie BrS and point to acacetin as a promising new pharmacologic treatment for JWS.

Bovine pericardium membrane, gingival stem cells, and ascorbic acid: a novel team in regenerative medicine.

Recently, the development and the application of 3D scaffold able to promote stem cell differentiation represented an essential field of interest in regenerative medicine. In particular, functionalized scaffolds improve bone tissue formation and promote bone defects repair. This research aims to evaluate the role of ascorbic acid (AS) supplementation in an in vitro model, in which a novel 3D-scaffold, bovine pericardium collagen membrane called BioRipar (BioR) was functionalized with human Gingival Mesenchymal Stem Cells (hGMSCs). As extensively reported in the literature, AS is an essential antioxidant molecule involved in the extracellular matrix secretion and in the osteogenic induction. Specifically, hGMSCs were seeded on BioR and treated with 60 and 90 µg/mL of AS in order to assess their growth behavior, the expression of bone specific markers involved in osteogenesis (runt-related transcription factor 2, RUNX2; collagen1A1, COL1A1; osteopontin, OPN; bone morphogenetic protein2/4, BMP2/4), and de novo deposition of calcium. The expression of COL1A1, RUNX2, BMP2/4 and OPN was evaluated by RT-PCR, Western blotting and immunocytochemistry, and proved to be upregulated. Our results demonstrate that after three weeks of treatment AS at 60 and 90 µg/mL operates as an osteogenic inductor in hGMSCs. These data indicate that the AS supplementation produces an enhancement of osteogenic phenotype commitment in an in vitro environment. For this reason, AS could represent a valid support for basic and translational research in tissue engineering and regenerative medicine.

Vitamin D and macrophage polarization in epicardial adipose tissue of atherosclerotic swine.

Vitamin D functions as a potent immunomodulator by interacting with many immune cells however, its role in regulating inflammation in the epicardial adipose tissue (EAT) is unclear. In the EAT of atherosclerotic microswine that were fed with deficient, sufficient or supplemented levels of vitamin D, we evaluated the phenotype of the macrophages. Vitamin D treatment was continued for 12 months and serum 25(OH)D levels were measured regularly. Infiltration of M1/M2 macrophage was investigated by immunostaining for CCR7 and CD206, respectively in conjunction with a pan macrophage marker CD14. Significant difference in the number of CCR7+ cells was observed in the EAT from vitamin D-deficient swine compared to vitamin D-sufficient or -supplemented swine. Expression of CD206 correlated with high levels of serum 25(OH)D indicating a significant increase in M2 macrophages in the EAT of vitamin D-supplemented compared to -deficient swine. These findings suggest that vitamin D-deficiency exacerbates inflammation by increasing pro-inflammatory M1 macrophages, while vitamin D-supplementation attenuates the inflammatory cytokines and promotes M2 macrophages in EAT. This study demonstrates the significance of vitamin D mediated inhibition of macrophage mediated inflammation in the EAT during coronary intervention in addition to its immunomodulatory role. However, additional studies are required to identify the cellular mechanisms that transduce signals between macrophages and smooth muscle cells during restenosis in the presence and absence of vitamin D.

Three members of a peptide family are differentially distributed and elicit differential state-dependent responses in a pattern generator-effector system.

C-type allatostatins (AST-Cs) are pleiotropic neuropeptides that are broadly conserved within arthropods; the presence of three AST-C isoforms, encoded by paralog genes, is common. However, these peptides are hypothesized to act through a single receptor, thereby exerting similar bioactivities within each species. We investigated this hypothesis in the American lobster, Homarus americanus, mapping the distributions of AST-C isoforms within relevant regions of the nervous system and digestive tract, and comparing their modulatory influences on the cardiac neuromuscular system. Immunohistochemistry showed that in the pericardial organ, a neuroendocrine release site, AST-C I and/or III and AST-C II are contained within distinct populations of release terminals. Moreover, AST-C I/III-like immunoreactivity was seen in midgut epithelial endocrine cells and the cardiac ganglion (CG), whereas AST-C II-like immunoreactivity was not seen in these tissues. These data suggest that AST-C I and/or III can modulate the CG both locally and hormonally; AST-C II likely acts on the CG solely as a hormonal modulator. Physiological studies demonstrated that all three AST-C isoforms can exert differential effects, including both increases and decreases, on contraction amplitude and frequency when perfused through the heart. However, in contrast to many state-dependent modulatory changes, the changes in contraction amplitude and frequency elicited by the AST-Cs were not functions of the baseline parameters. The responses to AST-C I and III, neither of which is COOH-terminally amidated, are more similar to one another than they are to the responses elicited by AST-C II, which is COOH-terminally amidated. These results suggest that the three AST-C isoforms are differentially distributed in the lobster nervous system/midgut and can elicit distinct behaviors from the cardiac neuromuscular system, with particular structural features, e.g., COOH-terminal amidation, likely important in determining the effects of the peptides. NEW & NOTEWORTHY Multiple isoforms of many peptides exert similar effects on neural circuits. In this study we show that each of the three isoforms of C-type allatostatin (AST-C) can exert differential effects, including both increases and decreases in contraction amplitude and frequency, on the lobster cardiac neuromuscular system. The distribution of effects elicited by the nonamidated isoforms AST-C I and III are more similar to one another than to the effects of the amidated AST-C II.

Mouse Proepicardium Exhibits a Sprouting Response to Exogenous Proangiogenic Growth Factors in vitro.

Angiogenesis contributes to the generation of the vascular bed but also affects the progression of many diseases, such as tumor growth. Many details of the molecular pathways controlling angiogenesis are still undefined due to the lack of appropriate models. We propose the proepicardial explant as a suitable model for studying certain aspects of angiogenesis. The proepicardium (PE) is a transient embryonic structure that contains a population of undifferentiated endothelial cells (ECs) forming a vascular net continuous with the sinus venosus. In this paper, we show that PE explants give rise to CD31-positive vascular sprouts in the presence of basic fibroblast growth factor (bFGF) and 2 isoforms of vascular endothelial growth factor A (VEGF-A), i.e. VEGF-A120 and VEGF-A164. Vascular sprouts exhibit differences in number, length, thickness and the number of branches, depending on the combination of growth factors used. Moreover, the ECs of the sprouts express various levels of mRNA for Notch1 and its ligand Dll4. Additionally, stimulation with bFGF/VEGF-A164 upregulates the expression of Lyve-1 antigen in the ECs in the sprouts. In summary, we present a new model for angiogenesis studies involving mouse PE as a source of ECs. We believe that our model may act as a supplementary assay for angiogenesis studies along with the existing models.

[Distribution of Substance P-positive Nerve Fibers in Local Skin Tissues of Five Shu-points of the Pericardium Meridian in the Rat].

OBJECTIVE: To investigate the distribution of substance P (SP)-positive nerve fibers in local skin tissues of the five shu-points of the Pericardium Meridian in rats for revealing the differential innervations of the five acupoints. METHODS: Six adult male SD rats were used in the present study. Under deep anesthesia, the rats received transcardiac perfusion with 4% polyformaldehyde+phosphate buffered solution, followed by dissecting the local skin tissues from the sites corresponding to five shu-points "Zhongchong" (PC 9), "Laogong" (PC 8), "Daling" (PC 7), "Jianshi" (PC 5), and "Quze" (PC 3) in the human body. The tissues were sagittally cut into sections (20 µm) using a freezing microtome, followed by fluorescent immunohistochemi-cal and histochemical staining with SP, phalloidin and DAPI, respectively. The distribution of SP-positive fibers were observed under fluorescent microscope and laser confocal microscope. RESULTS: In general, SP expressed on the thin sensory fibers in the skin tissue. SP-positive nerve fibers distributed in a free single style in the epidermis and dermis, and gathered together to form a bundle in the subcutaneous layer. After counting the number and length of free single fibers in the epidermis and dermis of each of the five shu-points, we found that no significant differences existed in the density between the PC 9 and PC 8 regions, as well as among the PC 7, PC 5, and PC 3 regions (P>0.05). In contrast, the density of SP-positive nerve fibers in the former two acupoints (PC 9 and PC 8) was significantly higher than that of anyone of the latter three acupoints (P<0.01). In addition, SP positive nerve fibers mainly ran in parallel to the vessel-like structure. CONCLUSIONS: The local skin tissues of acupoint PC 9, PC 8, PC 7, PC 5, and PC 3 of the Pericardium Meridian express SP-positive fibers, which presents a decreasing tendency in the density from the distal to the proximal part of the forelimb, reflecting a relative specificity of the innervations of the five shu-points.

Transcutaneous Electrical Stimulation Increased Nitric Oxide-Cyclic GMP Release Biocaptured Over Skin Surface of Pericardium Meridian and Acupuncture Points in Humans.

OBJECTIVES: The purpose of this study was to consecutively capture and quantify nitric oxide (NO) and cGMP, the second messenger of NO, over the skin surface of acupuncture points (acupoints), meridian line without acupoint, and non-meridian control regions of the Pericardium meridian (PC) in humans, and investigate their response to transcutaneous electrical nerve stimulation (TENS) . DESIGN, SETTING, AND MAIN OUTCOME MEASURES: Adhesive biocapture tubes were attached to the skin surface along PC regions and injected with 2-Phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl solution, an NO-scavenging compound, contacting the skin surface for 20 minutes each during 4 consecutive biocapture intervals. TENS (1.0 mA, 6 Hz, 1.0 msec duration) was applied over acupoints PC 8 and PC 3 during the 2nd biocapture for 20 min. Total nitrite and nitrate (NO(x)-), the stable metabolic products of NO, and cGMP in biocaptured samples were quantified using chemiluminescence and ELISA. RESULTS: NO(x)- levels in the 1st biocapture over PC regions are almost two fold higher compared to subsequent biocaptures and are higher over PC acupoints versus non-meridian control region. Following TENS, NO(x)- concentrations over PC regions were significantly increased, and cGMP is predominantly released from the skin surface of PC acupoints. CONCLUSIONS: TENS induces elevations of NO-cGMP concentrations over local skin region with a high level at acupoints. The enhanced signal molecules improve local circulation, which contributes to beneficial effects of the therapy.

Variations in energy metabolism along the pericardium meridian and its relationship with visceral function adjustments during electroacupuncture.

BACKGROUND: Electroacupuncture (EA) is a traditional Chinese medicine treatment guided by meridian theory. As it gradually gains more worldwide acceptance, a clarification of its mechanisms is extremely urgent. We observed variations in transcutaneous oxygen pressure/carbon dioxide pressure (tcpO2/tcpCO2) and microcirculation blood perfusion units (BPU) along the pericardium meridian, and cardiac function during EA at Neiguan (PC6) to explore variations in energy metabolism and its relationship with visceral function adjustments during EA. METHODS: Twenty-two healthy volunteers participated in this study. Three channel laser Doppler flowmetry and tcpO2/tcpCO2 detection systems were used to detect tcpO2/tcpCO2 and microcirculation BPU along the pericardium meridian. A hemodynamic monitor was used to detect cardiac function. RESULTS: In the normal state, the microcirculatory BPU along the pericardium meridian were significantly higher than that of their bilateral corresponding control points (p < 0.05). During EA at PC6, the values of the microcirculatory BPU along the pericardium meridian did not vary, and few increased. In the normal state, the values of tcpO2 along the pericardium meridian were significantly higher than those of their bilateral corresponding control points (p < 0.05). In addition, the values of tcpCO2 along the pericardium meridian were lower than those of their bilateral corresponding control points. In comparison with the normal state, EA could decrease tcpO2 along the meridian significantly (p < 0.05) and increase tcpCO2. During EA at PC6 in healthy volunteers treated by artificial acute mild hypoxia, cardiac output and cardiac index (p < 0.05) decreased and systemic vascular resistance increased significantly (p < 0.05). CONCLUSIONS: In the normal state, the values of microcirculatory BPU and tcpO2 along the pericardium meridian were both higher than those of their bilateral corresponding control points. Energy metabolism was vigorous along the meridian. During EA, the decrease in oxygen partial pressure along the pericardium meridian might be a result of strengthened energy metabolism of associated tissue and increased oxygen consumption. The variations in energy metabolism along the pericardium meridian during the course of EA had a close relationship with visceral function adjustments. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTRTRC13003193.

Combined anticalcification treatment of bovine pericardium with decellularization and hyaluronic acid derivative.

The objective of this work was to evaluate the effect of decellularization and hyaluronic acid derivative on the improvement of anticalcification of glutaraldehyde fixed bovine pericardium (GFBP) using a rat subcutaneous implantation model A cell extraction process was employed to remove the cells and cellular components from bovine pericardium (BP), leaving a framework of largely insoluble collagen. Then acellular BP was cross-linked by glutaraldehyde solution and treated with hyaluronic acid derivative (HA-ADH) which was obtained by coupling adipic dihydrazide (ADH) on-COOH of hyaluronic acid (HA). The results of in vivo calcification tests showed that the calcium content was decreased dramatically by decellularization alone (from 28.07 ± 18.87 to 2.44 ± 0.55 µg Ca/mg dry tissue after 8 weeks' implantation), and even less concentration was shown by the combination of HA derivative treatment and decellularization (GFaBP-HA group) (0.25 ± 0.08 µg Ca/mg dry tissue after 8 weeks' implantation). In addition, GFaBP-HA group not only presented a lower degree of calcification, but also showed lower ratios of Ca/P molar, which corresponded to amorphous calcium phosphates. The obtained results indicated that GFaBP-HA was a potential candidate for the manufacture of anticalcification bioprostheses.

Aged garlic extract with supplement is associated with increase in brown adipose, decrease in white adipose tissue and predict lack of progression in coronary atherosclerosis.

BACKGROUND: Aged garlic extract with supplement (AGE-S) significantly reduces coronary artery calcium (CAC). We evaluated the effects of AGE-S on change in white (wEAT) and brown (bEAT) epicardial adipose tissue, homocysteine and CAC. METHODS: Sixty subjects, randomized to a daily capsule of placebo vs. AGE-S inclusive of aged garlic-extract (250 mg) plus vitamin-B12 (100 µg), folic-acid (300 µg), vitamin-B6 (12.5mg) and L-arginine (100mg) underwent CAC, wEAT and bEAT measurements at baseline and 12 months. The postcuff deflation temperature-rebound index of vascular function was assessed using a reactive-hyperemia procedure. Vascular dysfunction was defined according to the tertiles of temperature-rebound at 1 year of follow-up. CAC progression was defined as an annual-increase in CAC>15%. RESULTS: From baseline to 12 months, there was a strong correlation between increase in wEAT and CAC (r(2)=0.54, p=0.0001). At 1 year, the risks of CAC progression and increased wEAT and homocysteine were significantly lower in AGE-S to placebo (p<0.05). Similarly, bEAT and temperature-rebound were significantly higher in AGE-S as compared to placebo (p<0.05). Strong association between increase in temperature-rebound and bEAT/wEAT ratio (r(2)=0.80, p=0.001) was noted, which was more robust in AGE-S. Maximum beneficial effect of AGE-S was noted with increase in bEAT/wEAT ratio, temperature-rebound, and lack of progression of homocysteine and CAC. CONCLUSIONS: AGE-S is associated with increase in bEAT/wEAT ratio, reduction of homocysteine and lack of progression of CAC. Increases in bEAT/wEAT ratio correlated strongly with increases in vascular function measured by temperature-rebound and predicted a lack of CAC progression and plaque stabilization in response to AGE-S.

Donkey pericardium as an alternative bioprosthetic heart valve material.

This study comparatively evaluates the characteristics of glutaraldehyde-treated acellular bovine and donkey pericardium using histological and electronic microscopic observation techniques, shrinkage temperature, and mechanical properties, as well as determining calcium and phosphorus content at 4 and 8 weeks after the subcutaneous implantation of donkey and bovine pericardium in Wistar rats. Donkey pericardium was significantly thinner compared with bovine pericardium (1.622 ± 0.161 mm vs. 4.027 ± 0.401 mm, P < 0.0001) and was associated with significantly greater tensile strength (14.21 ± 3.81 MPa vs. 3.78 ± 1.20 MPa, P = 0.001) and elastic modulus (81.67 ± 20.41 MPa vs. 21.67 ± 11.69 MPa, P < 0.0001) over bovine pericardium. Shrinkage temperature of donkey pericardium was similar to that of bovine pericardium (87.43 ± 0.55°C vs. 87.50 ± 0.36°C, P = 0.810). No differences between groups were observed for maximum load (donkey: 21.64 ± 7.02 KN/m vs. bovine: 15.05 ± 4.50 KN/m, P = 0.082) and tear strength (donkey: 11.54 ± 5.33 MPa vs. bovine: 10.69 ± 3.77 MPa, P = 0.757). Calcium content was significantly lower in donkey pericardium compared with bovine pericardium at 4 weeks (690.15 ± 191.27 µg/g vs. 1381.73 ± 62.52 µg/g, P = 0.001) and 8 weeks (205.24 ± 62.40 µg/g vs. 910.48 ± 398.29 µg/g, P = 0.037). This preliminary study has confirmed that glutaraldehyde-tanned donkey pericardium, demonstrating reduced calcification and increased tensile strength, may provide a suitable bioprosthetic valve substitute.

Vitamin D deficiency induces cardiac hypertrophy and inflammation in epicardial adipose tissue in hypercholesterolemic swine.

INTRODUCTION: Vitamin D is a sectosteroid that functions through Vitamin D receptor (VDR), a transcription factor, which controls the transcription of many targets genes. Vitamin D deficiency has been linked with cardiovascular diseases, including heart failure and coronary artery disease. Suppressor of cytokine signaling (SOCS)3 regulates different biological processes such as inflammation and cellular differentiation and is an endogenous negative regulator of cardiac hypertrophy. OBJECTIVE: The purpose of this study was to test the hypothesis that vitamin D deficiency causes cardiomyocyte hypertrophy and increased proinflammatory profile in epicardial adipose tissue (EAT), and this correlates with decreased expression of SOCS3 in cardiomyocytes and EAT. METHODS: Eight female Yucatan miniswine were fed vitamin D-sufficient (900 IU/d) or vitamin D-deficient hypercholesterolemic diet. Lipid profile, metabolic panel, and serum 25(OH)D levels were regularly measured. After 12 months animals were euthanized and histological, immunohistochemical and qPCR studies were performed on myocardium and epicardial fat. RESULTS: Histological studies showed cardiac hypertrophy, as judged by cardiac myocyte cross sectional area, in the vitamin D-deficient group. Immunohistochemical and qPCR analyses showed significantly decreased mRNA and protein expression of VDR and SOCS3 in cardiomyocytes of vitamin D-deficient animals. EAT from vitamin D-deficient group had significantly higher expression of TNF-α, IL-6, MCP-1, and decreased adiponectin in association with increased inflammatory cellular infiltrate. Interestingly, EAT from vitamin D-deficient group had significantly decreased expression of SOCS3. CONCLUSION: These data suggest that vitamin D deficiency induces hypertrophy in cardiomyocytes which is associated with decreased expression of VDR and SOCS3. Vitamin D deficiency is also associated with increased inflammatory markers in EAT. Activity of VDR in the body is controlled through regulation of vitamin D metabolites. Therefore, restoration of VDR function by supplementation of VDR ligands in vitamin D-deficient population might be helpful in reducing inflammation and cardiovascular risk.

Use of endogenous NADH fluorescence for real-time in situ visualization of epicardial radiofrequency ablation lesions and gaps.

Radiofrequency ablation (RFA) aims to produce lesions that interrupt reentrant circuits or block the spread of electrical activation from sites of abnormal activity. Today, there are limited means for real-time visualization of cardiac muscle tissue injury during RFA procedures. We hypothesized that the fluorescence of endogenous NADH could be used as a marker of cardiac muscle injury during epicardial RFA procedures. Studies were conducted in blood-free and blood-perfused hearts from healthy adult Sprague-Dawley rats and New Zealand rabbits. Radiofrequency was applied to the epicardial surface of the heart using a 4-mm standard blazer ablation catheter. A dual camera optical mapping system was used to monitor NADH fluorescence upon ultraviolet illumination of the epicardial surface and to record optical action potentials using the voltage-sensitive probe RH237. Epicardial lesions were seen as areas of low NADH fluorescence. The lesions appeared immediately after ablation and remained stable for several hours. Real-time monitoring of NADH fluorescence allowed visualization of viable tissue between the RFA lesions. Dual recordings of NADH and epicardial electrical activity linked the gaps between lesions to postablation reentries. We found that the fluorescence of endogenous NADH aids the visualization of injured epicardial tissue caused by RFA. This was true for both blood-free and blood-perfused preparations. Gaps between NADH-negative regions revealed unablated tissue, which may promote postablation reentry or provide pathways for the conduction of abnormal electrical activity.

Cardiac responses to the intrapericardial delivery of metoprolol: targeted delivery compared to intravenous administration.

Anti-arrhythmic drugs have narrow therapeutic ranges and typically can engender harmful side effects. The intrapericardial (IP) delivery of anti-arrhythmic agents proposes to achieve higher myocardial levels while minimizing plasma concentrations, thus diminishing systemic side effects. Furthermore, IP delivery enables concentrations at the target site to be more precisely controlled. Our study objective was to compare the relative cardiac effects of intrapericardial administration of metoprolol to standard intravenous (IV) delivery in a swine surgical model. In order to answer the question of how IP metoprolol affects sinus tachycardia, atrial electrophysiology, and pharmacokinetics compared with IV delivery, a medial sternotomy was performed on 21 swine that were divided into three groups: (1) After inducing sinus tachycardia, metoprolol boluses were delivered IP (n = 4) or IV (n = 4); (2) metoprolol was administered either IP (n = 3) or IV (n = 3) with saline controls (n = 3), and electrophysiologic data were collected; (3) metoprolol levels were tracked both in the blood (IV, n = 2) and pericardial (IP, n = 2) fluid. After either IP or IV delivery of metoprolol, heart rates were lowered significantly to 70% and 73% of control rate, respectively. The therapeutic effect of IV-administered metoprolol was considerably reduced after 1 h but was sustained longer in the IP group. Additionally, ventricular contractility and mean arterial pressure parameters were significantly lower in IV-treated animals but were nearly unaffected in IP-treated animals. With IP administration, the elimination half-life of metoprolol in pericardial fluid was 14.4 min with negligible accumulations in the plasma, whereas with IV delivery, the elimination half-life in plasma was 11.1 min with negligible amounts found in the pericardial fluid. The targeted intrapericardial delivery of metoprolol effectively lowers heart rates for sustained periods of time, with minimal effect on either ventricular contractility or mean arterial pressure. We did not observe dramatic changes in induced atrial fibrillation times or refractory periods using this model.

Retinoic acid production by endocardium and epicardium is an injury response essential for zebrafish heart regeneration.

Zebrafish heart regeneration occurs through the activation of cardiomyocyte proliferation in areas of trauma. Here, we show that within 3 hr of ventricular injury, the entire endocardium undergoes morphological changes and induces expression of the retinoic acid (RA)-synthesizing enzyme raldh2. By one day posttrauma, raldh2 expression becomes localized to endocardial cells at the injury site, an area that is supplemented with raldh2-expressing epicardial cells as cardiogenesis begins. Induced transgenic inhibition of RA receptors or expression of an RA-degrading enzyme blocked regenerative cardiomyocyte proliferation. Injured hearts of the ancient fish Polypterus senegalus also induced and maintained robust endocardial and epicardial raldh2 expression coincident with cardiomyocyte proliferation, whereas poorly regenerative infarcted murine hearts did not. Our findings reveal that the endocardium is a dynamic, injury-responsive source of RA in zebrafish, and indicate key roles for endocardial and epicardial cells in targeting RA synthesis to damaged heart tissue and promoting cardiomyocyte proliferation.

Cytosolic calcium accumulation and delayed repolarization associated with ventricular arrhythmias in a guinea pig model of Andersen-Tawil syndrome.

BACKGROUND: Andersen-Tawil syndrome (ATS1)-associated ventricular arrhythmias are initiated by frequent, hypokalemia-exacerbated, triggered activity. Previous ex vivo studies in drug-induced Andersen-Tawil syndrome (DI-ATS1) models have proposed that arrhythmia propensity in DI-ATS1 derives from cytosolic Ca(2+) ([Ca(2+)](i)) accumulation leading to increased triggered activity. OBJECTIVE: The purpose of this study was to test the hypothesis that elevated [Ca(2+)](i) with concomitant APD prolongation, rather than APD dispersion, underlies arrhythmia propensity during DI-ATS1. METHODS: DI-ATS1 was induced in isolated guinea pig ventricles by perfusion of 2 mM KCl Tyrode solution containing 10 µM BaCl(2). APD and [Ca(2+)](i) from the anterior epicardium were quantified by ratiometric optical voltage (di-4-ANEPPS) or Ca(2+) (Indo-1) mapping during right ventricular pacing with or without the ATP-sensitive potassium channel opener pinacidil (15 µM). RESULTS: APD gradients under all conditions were insufficient for arrhythmia induction by programmed stimulation. However, 38% of DI-ATS1 preparations experienced ventricular tachycardias (VTs), and all preparations experienced a high incidence of premature ventricular complexes (PVCs). Pinacidil decreased APD and APD dispersion and reduced VTs (to 6%), and PVC frequency (by 79.5%). However, PVC frequency remained significantly greater relative to control (0.5% ± 0.3% of DI-ATS1). Importantly, increased arrhythmia propensity during DI-ATS1 was associated with diastolic [Ca(2+)](i) accumulation and increased [Ca(2+)](i) transient amplitudes. Pinacidil partially attenuated the former but did not alter the latter. CONCLUSION: The study data suggest that arrhythmias during DI-ATS1 may be a result of triggered activity secondary to prolonged APD and altered [Ca(2+)](i) cycling and less likely dependent on large epicardial APD gradients forming the substrate for reentry. Therefore, therapies aimed at reducing [Ca(2+)](i) rather than APD gradients may prove effective in treatment of ATS1.

Gravity separation of pericardial fat in cardiotomy suction blood: an in vitro model.

Fat emboli generated during cardiac surgery have been shown to cause neurologic complications in patients postoperatively. Cardiotomy suction has been known to be a large generator of emboli. This study will examine the efficacy of a separation technique in which the cardiotomy suction blood is stored in a cardiotomy reservoir for various time intervals to allow spontaneous separation of fat from blood by density. Soybean oil was added to heparinized porcine blood to simulate the blood of a patient with hypertriglyceridemia (> 150 mg/dL). Roller pump suction was used to transfer the room temperature blood into the cardiotomy reservoir. Blood was removed from the reservoir in 200-mL aliquots at 0, 15, 30 45, and 60 minutes. Samples were taken at each interval and centrifuged to facilitate further separation of liquid fat. Fat content in each sample was determined by a point-of-care triglyceride analyzer. Three trials were conducted for a total of 30 samples. The 0-minute group was considered a baseline and was compared to the other four times. Fat concentration was reduced significantly in the 45- and 60-minute groups compared to the 0-, 15-, and 30-minute groups (p < .05). Gravity separation of cardiotomy suction blood is effective; however, it may require retention of blood for more time than is clinically acceptable during a routing coronary artery bypass graft surgery.

Larger dispersion of INa in female dog ventricle as a mechanism for gender-specific incidence of cardiac arrhythmias.

AIMS: Women have a higher incidence of long QT-related arrhythmias, whereas men exhibit a higher incidence of Brugada syndrome (BrS). The cardiac sodium current (I(Na)) is associated with arrhythmias in BrS and long QT-syndrome (LQTS) and conduction disease. Although a great deal of work has been performed to explain how heterogeneous distribution of repolarizing currents triggers arrhythmias, the transmural distribution of I(Na) within the cardiac ventricle and its contribution to generate the arrhythmogenic substrate remain unknown. We undertook to determine whether I(Na) was heterogeneously distributed within the ventricular wall of canine heart, an animal model close to humans. METHODS AND RESULTS: Using patch-clamp and molecular biology techniques, we tested whether gender differences exist in the ventricular distribution and amplitude of I(Na) in the canine heart model. Our results show that the I(Na) amplitude is smaller in the female epicardial and endocardial layers of the left ventricle, but similar to male in the mid-myocardium. Exposure of female cardiomyocytes to testosterone increased the amplitude of I(Na) to levels similar to male in epicardium, but had no effects in mid-myocardial and endocardial cells. Castrated male dogs displayed I(Na) amplitudes similar to what was found in female hearts. CONCLUSION: The larger dispersion of I(Na) amplitude within the female cardiac ventricle may contribute to the higher risk of arrhythmias in females. Testosterone modulates this dispersion. By decreasing the transmural dispersion of I(Na), testosterone may exert a protective effect against LQTS-related arrhythmias in males.

The distribution of transcutaneous CO2 emission and correlation with the points along the pericardium meridian.

This study aimed to understand energy metabolism distribution along the pericardium meridian and verify the correlation between the body surface (points), and classic meridian theory. A highly sensitive CO(2) instrument was used to measure the transcutaneous CO(2) emission at 13 points along the pericardium meridian line (12 points on the line and one point beyond the line) and 13 control points beside them. Results showed that the distribution of transcutaneous CO(2) emission is highly related to the position on the body. Transcutaneous CO(2) emission is significantly higher at P7 and P3, than the control points beside them. The points along the meridian and the points beside them were clustered with relative distance by SAS statistics software. Two distance matrixes were then obtained. The correlation coefficients between the points along the line and between the control points were calculated. The results showed that the 13(th) point beyond the line was far from the 12 points on the line (distance, 0.24), while acupoints on the line clustered earlier when compared with the non-acupoints. The average correlation coefficients among the acu-points was 0.65 which was significantly higher than 0.56, among the non-acupoints. No such characteristics were found among the control points. It was concluded that there is a strong correlativity of energy metabolism activity between the body surfaces along the meridian, and an even stronger correlativity between the acupoints on the meridian.