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

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<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.

3037The prognostic significance of grade of ischemia in patients with STEMI: a substudy of the randomized trial of primary PCI with or without routine manual thrombectomy (TOTAL trial)

Background

The importance of grade of ischemia (GI) classification in the risk assessment of patients with ST-elevation myocardial infarction has been shown previously. Grade 3 ischemia (G3I) is defined by the Sclarovsky-Birnbaum grading system as ECG with ST-elevation and distortion of the terminal portion of the QRS complex in two or more adjacent leads, while grade 2 ischemia (G2I) is defined as ECG with ST-elevation without QRS distortion.

Methods

In a substudy of the international, multicenter, prospective, randomized Trial of Routine Aspiration Thrombectomy with PCI versus PCI Alone in Patients with STEMI (TOTAL), we studied the prognostic impact of the grade of ischemia classification on the outcome in patients with STEMI (n=7,211). The primary outcome was a composite of death from cardiovascular causes, recurrent MI, cardiogenic shock, or New York Heart Association (NYHA) class IV heart failure within one year.

Results

The primary outcome occurred in 153 of 1,563 patients (9.8%) in the G3I group vs. 364 of 5,648 patients (6.4%) in the G2I group (hazard ratio [HR], 1.55; 95% confidence interval [CI], 1.29 to 1.88; p<0.001). The rates of cardiovascular death (4.8% with G3I vs. 2.5% with G2I; HR, 1.92; 95% CI, 1.45 to 2.54; p<0.001) and all-cause mortality (5.2% with G3I vs. 3.3% with G2I; HR, 1.62; 95% CI, 1.25 to 2.10; p<0.001) were also higher in patients with G3I. The rate of stroke or TIA were similar within the two groups (1.1% with G3I vs. 1.0% with G2I; HR, 1.13; 95% CI, 0.66 to 1.95; p=0.650). The grade of ischemia (G3I vs G2I) was shown to be an independent predictor of primary outcome in adjusted multivariable analysis (adjusted HR, 1.43; 95% CI, 1.18 to 1.74; p<0.001).

Conclusions

STEMI patients with G3I in the presenting ECG proved to have an increased rate of cardiovascular death, recurrent MI, cardiogenic shock, or NYHA class IV heart failure within one year compared to patients with G2I.

Acknowledgement/Funding

Competitive State Research Financing of the Expert Responsibility area of Tampere University Hospital, The unit of Heart Center Co. [Z60064]

Minimal cues in the vocal communication of affect: Judging emotions from content-masked speech

Vocal expressions of emotions taken from a recorded version of a play were content. masked by using electronic filtering, randomized splicing and a combination of both techniques in addition to a no-treatment condition in a 2×2 design. Untrained listener-judges rated the voice samples in the four conditions on 20 semantic differential scales. Irrespective of the severe reduction in the number and types of vocal cues in the masking conditions, the mean ratings of the judges in all four groups agreed on a level significantly beyond chance expectations on the differential position of the emotional expressions in a multidimensional space of emotional meaning. The results suggest that a minimal set of vocal cues consisting of pitch level and variation, amplitude level and variation, and rate of articulation may be sufficient to communicate the evaluation, potency, and activity dimensions of emotional meaning. Each of these dimensions may be associated with a specific pattern of vocal cues or cue combinations. No differential effects of the type of content-masking for specific emotions were found. Systematic effects of the masking techniques consisted in a lowering of the perceived activity level of the emotions in the case of electronic filtering, and more positive ratings on the evaluative dimension in the case of randomized splicing. Electronic filtering tended to decrease, randomized splicing tended to increase inter-rater reliability.