Structural and electrophysiological dysfunctions due to increased endoplasmic reticulum stress in a long-term pacing model using human induced pluripotent stem cell-derived ventricular cardiomyocytes

Abstract

BackgroundLong-term ventricular pacing has deleterious effects and becomes more significant when cumulative percent ventricular pacing (Cum%VP) exceeds 40% of time. However, cellular disturbances and pathways by which pacing leads to myocardial disorders are not well understood. Attempts to resolve these questions have been hampered by difficulties in obtaining human cardiac tissue and the inability to build a longer-lasting (lasting longer than weeks) pacing model in vitro.MethodsHuman induced pluripotent stem cell-derived ventricular cardiomyocytes (VCMs) were cultured in the presence of electrical stimulation for 2 weeks. Quantitative structural and electrophysiological analyses were used to define the functional disturbances of pacing.ResultsCompared to controls, paced VCMs exhibited a remarkable reduction in the contractile protein expression, an increased apoptosis ratio and electrophysiological remodelling in a Cum%VP-dependent manner. Investigation of the protein expression levels revealed that long-term pacing universally activated both ER stress and downstream calpain. Moreover, the inhibition of calpain attenuated the adverse effects on the structural remodelling and increased the ICa, L in paced VCMs.ConclusionsThe results demonstrated that pacing VCMs for 2 weeks in vitro led to a series of structural and electrophysiological dysfunctions. The increased ER stress and downstream calpain could be a central mechanism underlying the disease pathogenesis. This finding could represent a new therapeutic target in the management of long-term pacing patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-017-0566-6) contains supplementary material, which is available to authorized users.

Chronic intermittent tachypacing by an optogenetic approach induces arrhythmia vulnerability in human engineered heart tissue

“… 37 Faster contraction kinetics were accompanied by shorter APD 90 ( Figure 4 H ) upon chronic optical tachypacing, as it was previously reported for chronic electrical stimulation. 15 , 37 Expression analysis did not reveal significant changes in the expression of depolarizing ( CACNA1C ) or repolarizing ion channels ( KCNH2 and KCNQ1; Figure 6 D and Supplementary material online , Figure S6 ). Although transcript levels of CACNA1C were unchanged, APD 90 shortening might be explained by lower I CaL density in optically tachypaced compared to unpaced ChR2-EHTs ( Figure 6 E ).…”

“… 12–14 On the contrary, chronic electrical stimulation can also induce structural and electrophysiological adverse remodelling in hiPSC-derived ventricular CMs. 15 Rapid electrical pacing of hiPSC-CMs disturbed calcium homeostasis, which led to mitochondrial stress, promoted cell apoptosis, and caused electrophysiological remodelling. 16 The mechanisms of these adverse consequences of electrical pacing are not clear and may have also technical reasons.…”

Assessment of Drug Proarrhythmic Potential in Electrically Paced Human Induced Pluripotent Stem Cell–Derived Ventricular Cardiomyocytes Using Multielectrode Array

“…17 The adverse effects mentioned earlier in hiPSC-CMs caused by electrical stimulus, such as electrophysiological remodeling and structural changes, mainly occurred with long-term, rapid, and strong-intensity electrical stimulation (i.e., 3 V for 1 week at 3 Hz, or 3 V for 6 weeks at 1.2 Hz). 18–20 One week of electrical stimulation with 3 V at 1 Hz did not, however, change the electrophysiological properties of hiPSC-CMs. 18 Considering current CiPA guidance on evaluating the acute TdP risk of a drug, the electrical stimulus (400 mV) used here should only have a minor influence on the activity of hiPSC-vCMs.…”

Comparative Analysis of Genetic Variations in the Nav1.5 Sodium Channel Subunits that Underlie Brugada Syndrome Using Patient-Specific iPSC-CMs

“…Cardiomyocytes were prepared for TEM evaluation as described previously (15). Brie y, CMs were dissociated into single cells with 0.25% trypsin.…”

“…The parameters that describe and evaluate the calcium transient include the spontaneous beat rate, amplitude and arrhythmic events that are EADlike or brillation-like. Data were analyzed using ImageJ as previously described (15).…”