Ventricle Of Rats Research Articles

MicroRNA-dependent suppression of biological pacemaker activity induced by TBX18

Chemically modified mRNA (CMmRNA) with selectively altered nucleotides are used to deliver transgenes, but translation efficiency is variable. We have transfected CMmRNA encoding human T-box transcription factor 18 (CMmTBX18) into heart cells or the left ventricle of rats with atrioventricular block. TBX18 protein expression from CMmTBX18 is weak and transient, but Acriflavine, an Argonaute 2 inhibitor, boosts TBX18 levels. Small RNA sequencing identified two upregulated microRNAs (miRs) in CMmTBX18-transfected cells. Co-administration of miR-1-3p and miR-1b antagomiRs with CMmTBX18 prolongs TBX18 expression invitro and invivo and is sufficient to generate electrical stimuli capable of pacing the heart. Different suppressive miRs likewise limit the expression of VEGF-A CMmRNA. Cells therefore resist translation of CMmRNA therapeutic transgenes by upregulating suppressive miRs. Blockade of suppressive miRs enhances CMmRNA expression of genes driving biological pacing or angiogenesis. Such counterstrategies constitute an approach to boost the efficacy and efficiency of CMmRNA therapies.

Human Urinary Kallidinogenase Pretreatment Inhibits Myocardial Inflammation and Apoptosis after Coronary Microembolization by Activating PI3K/Akt/FoxO1 Axis.

As a fatal cardiovascular complication, coronary microembolization (CME) results in severe cardiac dysfunction and arrhythmia associated with myocardial inflammation and apoptosis. Human urinary kallidinogenase (HUK) can provide a protective function for cardiomyocytes by improving microcirculation. However, the therapeutic effects and underlying mechanisms of HUK in CME-induced myocardial injury remain unclear. We evaluated the effect of HUK on cardiac protection in a rat model of CME and whether it could restrain myocardial inflammation and apoptosis, and alleviate CME-induced myocardial injury. We established the CME model by injecting 42 μm inert plastic microspheres into the left ventricle of rats in advance, then the rats were randomly and equally divided into CME, CME + HUK (the dose of HUK at 0.016 PNA/kg/day), CME + HUK + LY (the dose of LY294002 at 10 mg/kg, 30 minutes before modeling), and Sham operation groups. Cardiac function, the serum levels of myocardial injury biomarkers, myocardial inflammation and apoptosis-related genes were measured; and the myocardial histopathological examination was performed at 12 h after the operation. The results revealed that HUK effectively reducing myocardial inflammation, apoptosis, and myocardial infarction area; and improving CME-induced cardiac injury by activating the PI3K/Akt/FoxO1 axis. In addition, these cardioprotective effects can be reduced by the PI3K specific inhibitor LY294002, suggesting that the aforementioned protective effects may be related to activation of the PI3K/Akt/FoxO1 axis. HUK seems to control inflammatory infiltration and cardiomyocyte apoptosis significantly to improve CME-induced cardiac injury via regulating the PI3K/Akt/FoxO1 axis.

CYP2D in the brain impacts oral hydrocodone analgesia in vivo

Cytochrome P450 2D (CYP2D) metabolises many centrally-acting substrates including opioids. Hydrocodone, an opioid and CYP2D substrate, is metabolised to hydromorphone, an active metabolite. CYP2D in the brain is active in vivo and can alter drug response however, it is unknown whether metabolism by CYP2D in the brain alters oral hydrocodone induced analgesia. Propranolol, a selective CYP2D mechanism-based inhibitor, or vehicle, was administered into the right cerebral ventricle of male rats, (HAN Wistars, Envigo), 24 h before testing for analgesia from oral hydrocodone (or hydromorphone, a non-CYP2D substrate). Hydrocodone and its CYP2D-mediated metabolites were simultaneously quantified using a novel LC-MS/MS assay. After propranolol vs vehicle pretreatment, there was significantly higher analgesia from oral hydrocodone, and a significantly lower brain CYP2D metabolic ratio (an in vivo phenotype of brain CYP2D activity that was derived from the molar sum of hydromorphone and its metabolites divided by hydrocodone). The brain CYP2D metabolic ratio correlated significantly with analgesia. There was no pretreatment effect on plasma hydrocodone concentrations, elimination rates, or metabolic ratio (an in vivo phenotype for hepatic CYP2D activity). The liver CYP2D metabolic ratio did not correlate with analgesia. Propranolol pretreatment had no impact on analgesia from oral hydromorphone. These data suggest that inhibited CYP2D activity in brain, causing reduced metabolism of brain hydrocodone, resulted in higher analgesia from oral hydrocodone, despite hydrocodone having a lower μ-opioid receptor affinity than hydromorphone. Thus, variation in CYP2D in the brain may be an important source of interindividual differences in response to CYP2D substrates, including oral hydrocodone.

Extracellular signal-regulated kinase-dependent phosphorylation of histone H3 serine 10 is involved in the pathogenesis of traumatic brain injury.

Traumatic brain injury (TBI) induces a series of epigenetic changes in brain tissue, among which histone modifications are associated with the deterioration of TBI. In this study, we explored the role of histone H3 modifications in a weight-drop model of TBI in rats. Screening for various histone modifications, immunoblot analyses revealed that the phosphorylation of histone H3 serine 10 (p-H3S10) was significantly upregulated after TBI in the brain tissue surrounding the injury site. A similar posttraumatic regulation was observed for phosphorylated extracellular signal-regulated kinase (p-ERK), which is known to phosphorylate H3S10. In support of the hypothesis that ERK-mediated phosphorylation of H3S10 contributes to TBI pathogenesis, double immunofluorescence staining of brain sections showed high levels and colocalization of p-H3S10 and p-ERK predominantly in neurons surrounding the injury site. To test the hypothesis that inhibition of ERK-H3S10 signaling ameliorates TBI pathogenesis, the mitogen-activated protein kinase–extracellular signal-regulated kinase kinase (MEK) 1/2 inhibitor U0126, which inhibits ERK phosphorylation, was administered into the right lateral ventricle of TBI male and female rats via intracerebroventricular cannulation for 7 days post trauma. U0126 administration indeed prevented H3S10 phosphorylation and improved motor function recovery and cognitive function compared to vehicle treatment. In agreement with our findings in the rat model of TBI, immunoblot and double immunofluorescence analyses of brain tissue specimens from patients with TBI demonstrated high levels and colocalization of p-H3S10 and p-ERK as compared to control specimens from non-injured individuals. In conclusion, our findings indicate that phosphorylation-dependent activation of ERK-H3S10 signaling participates in the pathogenesis of TBI and can be targeted by pharmacological approaches.

Activation of 5-HT3 receptors in the medulla oblongata is involved in the phasic control of urinary bladder

The control of micturition depends on reflex mechanisms, however, it undergoes modulation from cortex, pons and medullary areas. This study investigated if the activation of 5-HT3 receptors in the medulla influences the urinary bladder (UB) regulation in rats. Isoflurane female Wistar rats were submitted to catheterization of the femoral artery and vein for mean arterial pressure (MAP) and heart rate (HR) recordings and injection of drugs, respectively. The UB was cannulated for intravesical pressure (IP) measurement. The Doppler flow probe was placed around the left renal artery for renal conductance (RC) recordings. Phenylbiguanide (PB) and granisetron (GN) were injected into the 4th brain ventricle in rats with guide cannulas implanted 5 days prior to the experiments; or PB and GN were randomly injected intravenously or applied topically (in situ) on the UB. PB injection into 4th V significantly increased IP (68.67 ± 11.70%) and decreased MAP (−29 ± 6 mmHg) compared to saline (0.34 ± 0.64% and −2 ± 2 mmHg), with no changes in the HR and RC. GN injection into the 4th V did not significantly change the IP and RC compared to saline, nevertheless, significantly increased MAP (25 ± 4 mmHg) and heart rate (36 ± 9 bpm) compared to saline. Intravenous PB and GN only produced cardiovascular effects, whilst PB but not GN in situ on the UB evoked increase in IP (111.60 ± 30.36%). Therefore, the activation of 5HT-3 receptors in medullary areas increases the intravesical pressure and these receptors are involved in the phasic control of UB. In contrast, 5-HT3 receptors in the medulla oblongata are involved in the pathways of the tonic control of the cardiovascular system. The activation of 5-HT3 receptors in the bladder cause increase in intravesical pressure and this regulation seem to be under phasic control as the blockade of such receptors elicits no changes in baseline intravesical pressure.

Regulation of APD and Force by the Na+/Ca2+ Exchanger in Human-Induced Pluripotent Stem Cell-Derived Engineered Heart Tissue.

The physiological importance of NCX in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) is not well characterized but may depend on the relative strength of the current, compared to adult cardiomyocytes, and on the exact spatial arrangement of proteins involved in Ca2+ extrusion. Here, we determined NCX currents and its contribution to action potential and force in hiPSC-CMs cultured in engineered heart tissue (EHT). The results were compared with data from rat and human left ventricular tissue. The NCX currents in hiPSC-CMs were larger than in ventricular cardiomyocytes isolated from human left ventricles (1.3 ± 0.2 pA/pF and 3.2 ± 0.2 pA/pF for human ventricle and EHT, respectively, p < 0.05). SEA0400 (10 µM) markedly shortened the APD90 in EHT (by 26.6 ± 5%, p < 0.05) and, to a lesser extent, in rat ventricular tissue (by 10.7 ± 1.6%, p < 0.05). Shortening in human left ventricular preparations was small and not different from time-matched controls (TMCs; p > 0.05). Force was increased by the NCX block in rat ventricle (by 31 ± 5.4%, p < 0.05) and EHT (by 20.8 ± 3.9%, p < 0.05), but not in human left ventricular preparations. In conclusion, hiPSC-CMs possess NCX currents not smaller than human left ventricular tissue. Robust NCX block-induced APD shortening and inotropy makes EHT an attractive pharmacological model.

Exosomal miR-27b-3p Derived from Hypoxic Cardiac Microvascular Endothelial Cells Alleviates Rat Myocardial Ischemia/Reperfusion Injury through Inhibiting Oxidative Stress-Induced Pyroptosis via Foxo1/GSDMD Signaling.

Background Exosomes derived from cardiac microvascular endothelial cells (CMECs) under hypoxia can mediate cardiac repair functions and alleviate pyroptosis and oxidative stress during ischemia-reperfusion (I/R) injury. This study is aimed at investigating the effect and mechanism of miR-27b-3p underlying hypoxic CMECs-derived exosomes against I/R injury. Methods CMECs were isolated from the left ventricle of Sprague-Dawley rats, followed by culturing under hypoxic conditions or pretreatment with the miR-27b-3p inhibitor. CMECs-derived exosomes were added into H9C2 cells before hypoxia/reoxygenation (H/R) or injected into the rat heart before I/R injury. An in vivo I/R injury model was established by ligating and releasing the left anterior descending coronary artery. Expression of pyroptosis-related factors was detected using Western blot, and heart infarcted size was determined by the 2,3,5-triphenyl-2H-tetrazpinolium chloride staining method. Dual-Luciferase Reporter assays were performed to analyze the interactions of nmiR-27b-3p-forkhead box O1 (Foxo1) and Gasdermin D- (GSDMD-) Foxo1. Chromatin-immunoprecipitation (ChIP) assays were performed to validate the interactions between forkhead box O1 (Foxo1) and Gasdermin D (GSDMD) and Foxo1-mediated histone acetylation of GSDMD. Results CMECs were successfully identified from left ventricle of Sprague-Dawley rats. The expressions of Foxo1 and pyroptosis-related proteins (GSDMD, NLPR3, cleaved caspase 1, IL-1β, and IL-18) were upregulated in the rat heart after I/R injury. Treatment of CMEC-derived exosomes, especially that under hypoxic conditions, significantly reduced pyroptosis in the rat heart. miR-27b-3p was significantly upregulated in CMEC-derived exosomes under hypoxic conditions, and miR-27b-3p inhibition in exosomes alleviated its cytoprotection and inhibited oxidative stress in H9C2 cells. Treatment with Foxo1 overexpression plasmids aggravated in vitro H/R and in vivo I/R injury by upregulating pyroptosis-related proteins. Further experiments validated that miR-27b-3p negatively targeted Foxo1, which bound to the promoter region of GSDMD. Conclusions These results demonstrated a great therapeutic efficacy of miR-27b-3p overexpression in hypoxic CMEC-derived exosomes in preventing the development of myocardial damage post I/R injury through inhibiting Foxo1/GSDMD signaling-induced oxidative stress and pyroptosis.

Brain Damage-linked ATP Promotes P2X7 Receptors Mediated Pineal N-acetylserotonin Release

The pineal gland is a key player in surveillance and defense responses. In healthy conditions, nocturnal circulating melatonin (MEL) impairs the rolling and adhesion of leukocytes to the endothelial layer. Fungi, bacteria, and pro-inflammatory cytokines block nocturnal pineal MEL synthesis, facilitating leukocyte migration to injured areas. ATP is a cotransmitter of the noradrenergic signal and potentiates noradrenaline (NAd)-induced MEL synthesis via P2Y1 receptor (P2Y1R) activation. Otherwise, ATP low-affinity P2X7 receptor (P2X7R) activation impairs N-acetylserotonin (NAS) into MEL conversion in NAd incubated pineals. Here we mimicked a focal increase of ATP by injecting low (0.3 and 1.0 µg) and high (3.0 µg) ATP in the right lateral ventricle of adult rats. Nocturnal pineal activity mimicked the in culture data. Low ATP doses increased MEL output, while high ATP dose and the P2X7R agonist BzATP (15.0–50.0 ng) increased NAS pineal and blood content. In the brain, the response was structure-dependent. There was an increase in cortical and no change in cerebellar MEL. These effects were mediated by changes in the expression of coding genes to synthetic and metabolizing melatonergic enzymes. Thus, the pineal gland plays a role as a first-line structure to respond to the death of cells inside the brain by turning NAS into the darkness hormone.

Critical Requirements for the Initiation of a Cardiac Arrhythmia in Rat Ventricle: How Many Myocytes?

Cardiovascular disease is the leading cause of death worldwide due in a large part to arrhythmia. In order to understand how calcium dynamics play a role in arrhythmogenesis, normal and dysfunctional Ca2+ signaling in a subcellular, cellular, and tissued level is examined using cardiac ventricular myocytes at a high temporal and spatial resolution using multiscale computational modeling. Ca2+ sparks underlie normal excitation–contraction coupling. However, under pathological conditions, Ca2+ sparks can combine to form Ca2+ waves. These propagating elevations of (Ca2+)i can activate an inward Na+–Ca2+ exchanger current (INCX) that contributes to early after-depolarization (EADs) and delayed after-depolarizations (DADs). However, how cellular currents lead to full depolarization of the myocardium and how they initiate extra systoles is still not fully understood. This study explores how many myocytes must be entrained to initiate arrhythmogenic depolarizations in biophysically detailed computational models. The model presented here suggests that only a small number of myocytes must activate in order to trigger an arrhythmogenic propagating action potential. These conditions were examined in 1-D, 2-D, and 3-D considering heart geometry. The depolarization of only a few hundred ventricular myocytes is required to trigger an ectopic depolarization. The number decreases under disease conditions such as heart failure. Furthermore, in geometrically restricted parts of the heart such as the thin muscle strands found in the trabeculae and papillary muscle, the number of cells needed to trigger a propagating depolarization falls even further to less than ten myocytes.

Pretreatment with Shenmai Injection Protects against Coronary Microvascular Dysfunction.

Background The clinical treatment of coronary microvascular dysfunction (CMD) is mainly based on conventional medicine, but the mechanism of the medicine is single and the efficacy is different. Shenmai injection (SMI) has a variety of ingredients, but the effect of SMI on CMD has not been studied. This study investigated the effect of SMI on CMD and its possible mechanism. Methods The protective effect of SMI on CMD was evaluated in Sprague-Dawley (SD) rats and human umbilical vein endothelial cells (HUVECs). In vivo, forty-five male SD rats were randomly divided into control group (sham group), CMD group (model group), and SMI group (treatment group). Two weeks after SMI intervention, laurate was injected into the left ventricle of rats to construct a CMD model. Blood samples were collected to detect myocardial enzymes, oxidative stress, and inflammatory factors, and the hearts of rats were extracted for histopathological staining and western blot detection. In vitro, a hydrogen peroxide-induced endothelial injury model was established in HUVECs. After pretreatment with SMI, cell viability, oxidative stress, vasodilative factors, and apoptosis were detected. Results In vivo, pretreatment with SMI could effectively reduce the concentrations of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB), cardiac troponin I (cTnI), endothelin-1 (ET-1), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and malondialdehyde (MDA) in the serum of rats. Meanwhile, the expression of bcl-2-associated X (Bax) and caspase-3 protein in the myocardium of rats was decreased in the SMI group. The levels of nitric oxide (NO) and superoxide dismutase (SOD) and the expression of B-cell lymphoma-2 (Bcl-2) were higher in the SMI group than in the CMD group. Pathological staining results showed that SMI could effectively reduce inflammatory infiltration and the formation of collagen fibers and microthrombus in the rat myocardium. In vitro, intervention with SMI could improve endothelial function in a dose-dependent manner as evidenced by increasing the activity of endothelial cells and the expression of NO, SOD, endothelial nitric oxide synthase (eNOS), and Bcl-2, while decreasing cell apoptosis and the levels of ET-1, MDA, Bax, and caspase-3. Conclusions Pretreatment with SMI could improve CMD by alleviating oxidative stress, inflammatory response, and apoptosis and then improving vascular endothelial function and microvascular structure.

INHIBITION OF RAS COMPONENTS ATTENUATES PROGRESSION OF MYOCARDIAL REMODELING IN BOTH NORMOTENSIVE AND HYPERTENSIVE RATS IN EXPERIMENTAL HEART FAILURE

Objective: New findings in the pathogenesis of heart failure (HF) with a focus on extracellular matrix (ECM) and communication in the heart are still relevant for more effective treatment. We focused on signaling pathways involved in cardiac structural remodeling in HF due to pressure and volume overload, as well as on investigating the efficacy of substances with possible antifibrotic potential. Design and method: We used as experimental model 28-week-old hypertensive (TGR) and normotensive (HSD) rats with created aortocaval fistula (ACF), supplemented with ACE inhibitor (ACEi) (Trandolapril, 15 weeks, 6 mg/L) and AT1 receptor blocker (ARB) (Losartan, 15 weeks, 200 mg/L). Results: Echocardiography confirmed an increase in cardiac output and a decrease in ejection fraction in both strains of rats. BW was higher in TGR vs HSD and it was not affected by VO. ACF-induced cardiac volume overload, elevated markers of heart failure and oxidative damage, ANP, BNP-45, and TBARS, were elevated in the blood serum of both strains. ACF induced profibrotic signaling by increasing TGF-, and mRNA collagen I, and collagen I protein expression in the left and right ventricles of HSD rats. In TGR rats ACF decreased TGF- and SMAD2 protein expression in the right ventricle similar to HSD rats, in which ACF also suppressed MMP-2 protein expression. Heart failure affected protein kinase signaling by reducing the protein expression of PKC, PKG, and in part, PKC in both chambers of the heart of both strains. ACF decreased the protein expression of Cx43 and its phosphorylated form, which is significantly proarrhythmic. Hypertension in TGR rats increased mRNA TGF- expression and collagen I, but decreased PKC and PKC protein expression and increased PKC. Conclusions: A notable finding was that the signaling pathways involved in cardiac remodeling were more normalized by the ARB, while proteins involved in intercellular communication, ACEi. The results of analyzes of both experiments indicate attenuated responses of the signaling pathways monitored by us in the heart of hypertensive strains reflecting adaptation to primarily induced pathophysiology. Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic VEGA 2/0158/19, 2/0002/20

Regulation of APD and force by Na+/Ca2+ exchanger in hiPSC-cardiomyocytes

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): BMBF Introduction Human induced pluripotent stem cell-derived cardiomyocytes (HiPSC-CM) are an emerging, powerful tool to study human cardiac physiology, pharmacology and toxicology, to model cardiovascular diseases or even to use for cardiac repair. Understanding the similarities and differences between hiPSC-CM and adult human cardiomyocytes is critical for their use. Here we focus on sodium calcium exchanger (NCX) who plays a crucial role in the Ca2+-homeostasis in the mammalian heart. Importantly, alterations in NCX expression in human heart are associated with various cardiac pathologies such as heart failure or arrhythmias. In order to investigate whether hiPSC-CM could serve as model for adult human heart NCX we measured the properties of NCX in hiPSC-CM and human ventricular tissue. Rat ventricular tissue was used for comparison. Methods HiPSC-CM were differentiated from a healthy iPSC line and dissociated from engineered heart tissue (EHT). Adult human and rat cardiomyocytes were digested from ventricular samples. We measured NCX current by the whole-cell patch clamp technique at 37 °C. Standard sharp microelectrodes were used to record action potentials (AP). Contractile force in human and rat ventricular samples was measured isometrically. A video-optical contractility test system was used to measure force in EHT. SEA0400 (10 µM) was used to block NCX. Results NCX currents could be measured in every hiPSC-CM. The NCX current densities in hiPSC-CM were larger than in human ventricular cardiomyocytes (3.2±0.2 pA/pF n=28 vs. 1.3±0.2 pA/pF n=15, p&amp;lt;0.05), but lower than reported for rat left ventricular cardiomyocytes using the same protocol. SEA0400 shortened APD90 markedly in EHT (264.1±24.9 ms to 191±31.6 ms, n=4) and to a lesser extent in rat ventricular tissue (54.4±3.9 ms to 48.9±4.2 ms, n=7). Shortening in human left ventricular preparations was tiny (320±22.1 ms to 305.5±20.3 ms, n=6) and not different from time-matched controls (TMC). Resting membrane potential, action potential amplitude and upstroke velocity were not affected neither in EHT nor in left ventricular preparations (rat and human). Force was significantly increased by NCX block in rat ventricle (by 31±5.4%, n=18) and EHT (by 20.8±3.9%, n=4), but in human left ventricular preparations there was only a tendency to attenuate spontaneous run-down (-3.7±4.3% n=8 with SEA vs. -6.2±3.7% n=12 in TMC). Conclusion HiPSC-CM possess NCX in the physiological range. HiPSC-CM show NCX-effects on APD and force as predicted from rat ventricle and in full accordance with cardiac physiology. Lack of NCX effect in human adult ventricles that had been already reported previously needs further investigations.

α-lipoic acid ameliorates inflammation state and oxidative stress by reducing the content of bioactive lipid derivatives in the left ventricle of rats fed a high-fat diet

Lipid mediators derived from arachidonic acid (AA) are implicated with the occurrence of inflammation and oxidative stress. The current knowledge of AA metabolism focuses on searching for the therapeutic strategy to subvert affected AA metabolism. The aim of our study was to evaluate the potential protective effect of chronic α-lipoic acid (α-LA) supplementation on myocardial inflammation state and oxidative stress in obesity-related cardiovascular dysfunction. The experiment was carried out on male Wistar rats receiving a standard or a high-fat diets with intragastric α-LA administration for 8 weeks. Plasma and myocardial AA concentrations were determined using the gas-liquid chromatography (GLC). The Western blot technique was used to examine the expression of proteins from the inflammatory pathway. The content of selected cytokines, inflammatory mediators, and oxidative stress indicators was detected by the ELISA, colorimetric, and multiplex assay kits. Our results revealed that α-LA caused a notable reduction in AA content, mainly in the phospholipid fraction with a simultaneous diminishment in the synthesis of pro-inflammatory mediators, i.e., prostaglandin E2, leukotrienes B4 and C4 by decreasing the expression of COX-2 and 5-LOX. α-LA also augmented the level of antioxidative SOD2 and GSH and decreased the level of lipid peroxidation products, which improved oxidative system impairment in the left ventricle tissue. The data clearly showed that α-lipoic acid has a significant role in inflammation and oxidative stress development ameliorating the risk of cardiac obesity induced by high-fat feeding.

Engineering Models of the Heart Left Ventricle.

Despite capturing the imagination of scientists for decades, the goal of creating an artificial heart for transplantation proved to be significantly more challenging than initially anticipated. Toward this goal, recent ground-breaking studies demonstrate the development of functional left ventricular (LV) models. LV models are artificially constructed 3D chambers that are capable of containing liquid within the engineered cavity and exhibit the functionality of native LV including contraction, ejection of fluid, and electrical impulse propagation. Various hydrogels and polymers have been used in manufacturing of LV models, relying on techniques such as electrospinning, bioprinting, casting, and molding. Most studies scaled down the models based on the dimensions of the human or rat ventricle. Initially, neonatal rat cardiomyocytes were the cell type of choice for construction the LV models. Yet, as the stem cell biology field advanced, recent studies focused on the use of cardiomyocytes derived from human induced pluripotent stem cells. In this review, we first describe the physiological characteristics of the human heart, to establish the parameter space for modeling. We then elaborate on current advances in the field and compare recently developed LV models among themselves and with the native human left ventricle. Fabrication methods, cell types, biomaterials, functional properties, and disease modeling capability are some of the major parameters that have distinguished these models. We also highlight some of the current challenges in this field, such as vascularization, cell composition and fidelity, and discuss potential solutions to overcome them.

Role of central irisin in the cardiorespiratory and metabolic control of adult rats

Irisin has been identified as an important exercise‐induced myokine that acts in different physiological systems; however, little is known about the participation of irisin in cardiorespiratory and basal metabolic control. Therefore, the present study evaluated the effect of intracerebroventricular (icv) injection of vehicle or irisin (IR, 0.425 µg/µL) in the fourth ventricle (4V) of adult male rats on the cardiorespiratory and metabolic control during wakefulness and sleep under room air, hypercapnia (7% CO2) and hypoxia (10% O2). Our data show a tendency of reduction in basal ventilation of IR group during wakefulness (VEH: 1056.2 ± 61.8 vs IR: 816.9 ± 30.5 mL.Kg‐1.min‐1), due to a reduction in respiratory frequency (VEH: 105.1 ± 5.3 vs IR: 85.9 ± 5.1 breaths.min‐1) and a consequent decrease in arterial partial pressure of O2 (VEH: 95.1 ± 2.4 vs IR: 88.7 ± 3.1 mmHg). No difference was observed in metabolic rate; however, central IR promoted a reduction in the air convection requirement (VEH: 57.2 ± 4.7 vs IR: 39.6 ± 3.7). Regarding the cardiovascular parameters, central injection of IR caused a significant increase in heart rate during hypoxia exposure (VEH: 342.5 ± 38.0 vs IR: 406.2 ± 16.8 beats.min‐1) without changing arterial pressure. These effects were only observed in awake conditions, with no changes evidenced during sleep. No difference in cardiorespiratory and metabolic parameter were observed under CO2 exposure after central IR injection. Therefore, our preliminary results suggest that IR caused a hypoventilation under room air conditions, possibly due to a lower ventilation, increased heart rate under hypoxic conditions, suggesting that this myokine also acts in the central nervous system to modulate breathing and cardiovascular parameters.

Pregnancy‐induced physiological cardiac hypertrophy regulates the expression of perilipin isoforms

Perilipins (PLINs) isoforms are proteins associated to surface of intracelular lipid droplets (LDs) that participate in the regulation of lipid metabolism and storage during hypertrophic cardiomyopathies. PLINs can associate to the PPAR coactivators peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha (PGC‐1α) and Sirtuin 1 (SIRT1) to regulate the expression of genes involved in lipid metabolism. Pregnancy‐induced physiological cardiac hypertrophy is a reversible process in which there is a change in lipid metabolism. However, there are a lack attention of the participation of PLINs isoforms in response to pregnancy‐induced cardiac hypertrophy. In this work, we quantified the PLINs isoforms and PGC‐1α mRNAs and proteins level, along with the transcriptional activities de PPARs family, triacylglyceride (TAG) and cholesterol/ester cholesterol in left ventricle of rats before, during, and after pregnancy. Expressions of mRNAs for PLIN1, PLIN2 and PLIN5 increased 9.5‐ and 7.4‐fold, 27.5‐ and 17.7‐fold, and 8‐ and 2.4‐fold 2 during pregnancy and postpartum, respectively, while PLIN3 did not change and PLIN4 was not detected. In contrast, the protein content of PLIN2 increased 1.5‐fold during postpartum, and PLIN5 increased 1.3‐ and 1.5‐ fold during pregnancy and postpartum, respectively, while PLIN1 did not change. Expression of mRNA and protein content for PGC‐1α increased 17.7 and 11.26‐fold and 1.5‐ and 1.2‐ fold during pregnancy and postpartum, respectively. The activity of PPARγ increased 1.6‐fold during pregnancy and decreased to basal levels postpartum. The concentration of TAG and Cholesterol/Cholesteryl ester increased 1.5‐ and 1.4‐ fold in the pregnant group compared to the non‐pregnant group, and returned to basal levels at postpartum, respectively. The results demonstrate that pregnancy‐induced, physiological cardiac hypertrophy activates the expression of genes involved in lipid storage suggesting that the shift in cardiac metabolism is mediated by the activation of PPARγ/PGC‐1α.

Cerebrospinal fluid-based boron delivery system may help increase the uptake boron for boron neutron capture therapy in veterinary medicine: A preliminary study with normal rat brain cells

Boron neutron capture therapy (BNCT) is a non-invasive type of radiation therapy developed for humans and translated to veterinary medicine. However, clinical trials on BNCT for patients with brain tumors are on-going. To improve the therapeutic efficacy of BNCT for brain tumors, we developed a boron delivery system that involves the cerebrospinal fluid (CSF), in contrast to the conventional method that involves intravenous (IV) administration. This study aimed to investigate the time-concentration profile of boron in the CSF as well as the uptake rate of boron by the brain cells after administering L-p‑boronophenylalanine (BPA) into the lateral ventricle of normal rats. Brain cell uptake rates were compared between the CSF-based and IV administration methods. The CSF-based and IV administration methods achieved comparable brain cell uptake levels; however, the former method involved lower BPA doses than the latter method. These findings suggest that the CSF method may reduce the economic and physical burdens associated with this treatment in brain tumor patients. Future studies should validate these findings in rat models of brain tumors.

Effect of Alpha-Lipoic Acid on Rat Ventricles and Atria under LPS-Induced Oxidative Stress.

Alpha-lipoic acid (α-LA) is a disulfide compound and one of the most effective antioxidants. Many studies have indicated positive effects of α-LA in the prevention of pathologic conditions mediated by oxidative stress, such as cardiovascular diseases. However, the therapeutic potential of α-LA for the heart has not been explored with regards to the ventricles and atria. The aim of our study was to evaluate the effects of α-LA on oxidative stress parameters and inflammation in the ventricles and atria of the heart in rats under LPS-induced oxidative stress. Wistar rats were divided into 4 groups: I—control (received 2 doses of 0.2 mL of 0.9% NaCl i.v., 0.5 h apart); II—α-LA (received 0.2 mL of 0.9% NaCl and 0.5 h later received α-LA 60 mg/kg b.w. i.v.); III—lipopolysaccharide (LPS) (received 0.2 mL of 0.9% NaCl and 0.5 h later received LPS 30 mg/kg b.w. i.v.); and IV—LPS + LA (received LPS 30 mg/kg b.w. i.v. and 0.5 h later received α-LA 60 mg/kg b.w. i.v.). Five hours later, the rats were euthanized. The hearts were surgically removed and weighed to estimate heart edema. The ventricular and atrium tissue was isolated to measure levels of TNF-α, IL-6, superoxide dismutase (SOD), thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2), total sulfhydryl groups (-SH), total glutathione (tGSH), reduced glutathione (GSH), glutathione disulfide (GSSG), and the GSH/GSSG ratio. LPS significantly increased TNF-α, IL-6, TBARS, and H2O2 levels and decreased SOD, -SH groups, tGSH, the GSH/GSSG ratio, and GSH levels in rat ventricles and atria while α-LA administered after the injection of LPS significantly decreased TNF-α, IL-6, TBARS, and H2O2 levels. α-LA also increased SOD and -SH group levels and ameliorated the glutathione redox status when compared to the LPS group. Our data suggest that α-LA administration 30 min after LPS infusion may effectively prevent inflammation and oxidative stress in the ventricles and atria.

Effect of Sex on Structural and Morphological Parameters of Rat Heart under Conditions of Combined Exposure to Hypokinesia and Cold.

We studied the combined effect of hypokinesia and external cooling on structural and morphological changes in the ventricular myocardium and parameters of homeostasis of the blood system in male and female WKY (normotensive) and SHR (hypertensive) rats. Simultaneous exposure to hypokinesia and cold caused destructive processes in the myocardium and high dynamics of heart remodeling with diverse structural and morphological changes in the left ventricle in rats of both sexes. The thickness of the left ventricular wall most rapidly decreased in male hypertensive SHR rats. The thickness of the wall of the right ventricle significantly increased in male and female rats of both strains. In WKY and SHR females, structural transformations in the heart were less pronounced than in males. The key role in different degree of morphological remodeling of the myocardium in male and female probably belongs to sex hormones.

Intraventricular Drug Delivery and Sampling for Pharmacokinetics and Pharmacodynamics Study.

Although the blood-brain barrier (BBB) protects the brain from foreign entities, it also prevents some therapeutics from crossing into the central nervous system (CNS) to ameliorate diseases or infections. Drugs are administered directly into the CNS in animals and humans to circumvent the BBB. The present protocol describes a unique way of treating brain infections through intraventricular delivery of antibiotics, i.e., polymyxins, the last-line antibiotics to treat multi-drug resistant Gram-negative bacteria. A straightforward stereotaxic surgery protocol was developed to implant a guide cannula reaching into the lateral ventricle in rats. After a recovery period of 24 h, rats can be injected consciously and repeatedly through a cannula that is fitted to the guide. Injections can be delivered manually as a bolus or infusion using a microinjection pump to obtain a slow and controlled flow rate. The intraventricular injection was successfully confirmed with Evans Blue dye. Cerebrospinal fluid (CSF) can be drained, and the brain and other organs can be collected. This approach is highly amenable for studies involving drug delivery to the CNS and subsequent assessment of pharmacokinetic and pharmacodynamic activity.