Custodiol-MP for ex vivo lung perfusion - A comparison in a porcine model of donation after circulatory determination of death.

INTRODUCTION: Ex vivo lung perfusion (EVLP) is an established technique to evaluate and eventually recondition lungs prior to transplantation. Custodiol-MP (C-MP) solution is a new solution, designed for clinical machine perfusion, that has been used for kidneys. The aim of this study was to compare the effects of EVLP with Custodiol-MP on lung functional outcomes to the gold standard of EVLP with Steen Solution™. MATERIAL AND METHODS: In a porcine EVLP model of DCDD (Donation after Circulatory Determination of Death), lungs were perfused with Steen Solution™ (SS, n = 7) or Custodiol-MP solution supplemented with 55 g/l albumin (C-MP, n = 8). Lungs were stored cold for 4 h in low potassium dextran solution and subsequently perfused ex vivo for 4 h. During EVLP pulmonary gas exchange, activities of lactate dehydrogenase (LDH) and alkaline phosphatase (AP) as well as levels of lactate in the perfusate were recorded hourly. RESULTS: Oxygenation capacity differed significantly between groups (averaged over 4 h: SS 274 ± 178 mmHg; C-MP 284 ± 151 mmHg p = 0.025). Lactate dehydrogenase activities and lactate concentrations were significantly lower in Custodiol-MP perfused lungs.In a porcine model of DCDD with 4 h of EVLP the use of modified Custodiol-MP as perfusion solution was feasible. The use of C-MP showed at least comparable lung functional outcomes to the use of Steen SolutionTM. Furthermore C-MP perfusion resulted in significantly lower lactate dehydrogenase activity and lactate levels in the perfusate and higher oxygenation capacity.

Pharmacologic TWIK-Related Acid-Sensitive K+ Channel (TASK-1) Potassium Channel Inhibitor A293 Facilitates Acute Cardioversion of Paroxysmal Atrial Fibrillation in a Porcine Large Animal Model.

Background The tandem of P domains in a weak inward rectifying K+ channel (TWIK)-related acid-sensitive K+ channel (TASK-1; hK2P3.1) two-pore-domain potassium channel was recently shown to regulate the atrial action potential duration. In the human heart, TASK-1 channels are specifically expressed in the atria. Furthermore, upregulation of atrial TASK-1 currents was described in patients suffering from atrial fibrillation (AF). We therefore hypothesized that TASK-1 channels represent an ideal target for antiarrhythmic therapy of AF. In the present study, we tested the antiarrhythmic effects of the high-affinity TASK-1 inhibitor A293 on cardioversion in a porcine model of paroxysmal AF. Methods and Results Heterologously expressed human and porcine TASK-1 channels are blocked by A293 to a similar extent. Patch clamp measurements from isolated human and porcine atrial cardiomyocytes showed comparable TASK-1 currents. Computational modeling was used to investigate the conditions under which A293 would be antiarrhythmic. German landrace pigs underwent electrophysiological studies under general anesthesia. Paroxysmal AF was induced by right atrial burst stimulation. After induction of AF episodes, intravenous administration of A293 restored sinus rhythm within cardioversion times of 177±63 seconds. Intravenous administration of A293 resulted in significant prolongation of the atrial effective refractory period, measured at cycle lengths of 300, 400 and 500 ms, whereas the surface ECG parameters and the ventricular effective refractory period lengths remained unchanged. Conclusions Pharmacological inhibition of atrial TASK-1 currents exerts antiarrhythmic effects in vivo as well as in silico, resulting in acute cardioversion of paroxysmal AF. Taken together, these experiments indicate the therapeutic potential of A293 for AF treatment.

Self-Powered Coiled Carbon-Nanotube Yarn Sensor for Gastric Electronics.

The strong peristaltic contraction of the stomach facilitates mixing and emptying of ingested food, which occurs rhythmically at approximately 3 cycles/min (cpm) in humans. Generally, most patients with gastroparesis show gastric electrical dysrhythmia that is disrupted electrical signals controlling gastric contractions. For treatment of gastric electrical dysrhythmia, in vivo electrical impulses to the stomach via an implanted gastric stimulator have been known to restore these gastric deformations. Nevertheless, improved sensors to monitor gastric contractions are still needed in current gastric stimulators. Recently, we have developed a new technology converting mechanical motion to electrical energy by using stretch-induced capacitance changes of a coiled carbon-nanotube (CNT) yarn. For its potential use as a gastric deformation sensor, the performance of a coiled CNT yarn was evaluated in several biological fluids. For a sinusoidal stretch to 30%, the peak-to-peak open-circuit voltage (OCV) was consistently generated at frequencies below 0.1 Hz. This sinusoidal variation in OCV augmented as the strain increased from 10 to 30%. In an in vitro artificial gastric system, the OCV was approximately linearly proportional to the balloon volume, which can monitor periodic deformations of the balloon at 2, 3, and 4 cpm as shown for human gastric deformations. Moreover, stretchy coiled yarns generate the peak electrical voltage and power when deformed. The present study shows that a self-powered CNT yarn sensor can not only monitor the changes in frequency and amplitude of volumetric change but also generate electrical power by periodic deformations of the balloon. Therefore, it seems possible to automatically deliver accurate electrical impulses according to real-time evaluation of a patient's gastric deformation based on information on the frequency, amplitude, and rate of the OCV from CNT yarn.

Enrichment of cardiac pacemaker-like cells: neuregulin-1 and cyclic AMP increase I(f)-current density and connexin 40 mRNA levels in fetal cardiomyocytes.

Generation of a large number of cells belonging to the cardiac pacemaker system would constitute an important step towards their utilization as a biological cardiac pacemaker system. The aim of the present study was to identify factors, which might induce transformation of a heterogenous population of fetal cardiomyocytes into cells with a pacemaker-like phenotype. Neuregulin-1 (alpha- and beta-isoform) or the cAMP was added to fresh cell cultures of murine embryonic cardiomyocytes. Quantitative northern blot analysis and flowcytometry were performed to detect the expression of connexins 40, 43 and 45. Patch clamp recordings in the whole cell configuration were performed to determine current density of I (f), a characteristic ion current of pacemaker cells. Fetal cardiomyocytes without supplement of neuregulin or cAMP served as control group. Neuregulin and cAMP significantly increased mRNA levels of connexin 40 (Cx-40), a marker of the early differentiating conduction system in mice. On the protein level, flowcytometry revealed no significant differences between treated and untreated groups with regard to the expression of connexins 40, 43 and 45. Treatment with cAMP (11.2 +/- 2.24 pA/pF; P < 0.001) and neuregulin-1-beta (6.23 +/- 1.07 pA/pF; P < 0.001) significantly increased the pacemaker current density compared to control cardiomyocytes (1.76 +/- 0.49 pA/pF). Our results indicate that neuregulin-1 and cAMP possess the capacity to cause significant transformation of a mixed population of fetal cardiomyocytes into cardiac pacemaker-like cells as shown by electrophysiology and increase of Cx-40 mRNA. This method may allow the development of a biological cardiac pacemaker system when applied to adult or embryonic stem cells.

Transplanted fetal cardiomyocytes as cardiac pacemaker.

BACKGROUND: While morphologic integration of transplanted fetal cardiomyocytes into the ventricular myocardium is a well-known fact, no studies have yet shown transplanted cells to coherently contribute to contraction and electrical excitation of the host myocardium. The aim of this study was to prove the hypothesis that by transplanting cardiomyocytes with a higher intrinsic rhythmic rate into the myocardium of the left ventricle, these cells could act as an ectopic pacemaker by functional coupling with host cardiomyocytes. METHODS AND RESULTS: Dissociated fetal canine atrial cardiomyocytes including sinus nodal cells were delivered into the free wall of the left ventricle of adult canine X-linked muscular dystrophy dogs (n=2). These dogs fail to express Dystrophin in both cardiac and skeletal muscle. In the control group (n=2) fetal skin fibroblasts were used for grafting. A total of 3-4 weeks after transplantation the dogs underwent catheter ablation of the atrioventricular node (AV-node) and subsequent electrophysiological mapping studies. Transplanted cells were identified by Dystrophin immunoreactivity, indicating survival and morphological integration in the recipient heart. The expression of Connexin 43 between donor and recipient cells suggested formation of gap junctions between injected and host cardiomyocytes. After catheter ablation of the AV-node, a ventricular escape rhythm emerged driving the pace of the heart and originating from the labeled transplantation site. This effect could not be observed in the control group (n=2). CONCLUSIONS: The results constitute the first observation of phenomena indicating electrical and mechanical coupling between allogeneic donor cardiomyocytes and recipient myocardium in-vivo. Further experiments are necessary to evaluate the technique as a potential therapy for atrioventricular block.