Background
Brugada Syndrome is a disorder associated with characteristic ECG precordial ST elevation and predisposes afflicted patients to ventricular fibrillation and sudden cardiac death. Despite marked achievements in outlining the organ level pathophysiology of the disorder, the understanding of human cellular phenotype has lagged due to lack of adequate human cellular models of the disorder.
Methods and Results
We recruited two patients with Type 1 Brugada Syndrome (BrS) carrying two different SCN5A variants and two healthy controls. We generated induced pluripotent stem cells (iPSCs) from their skin fibroblasts by using integration-free Sendai virus. We utilized directed differentiation to create purified populations of iPSC-derived cardiomyocytes (iPSC-CMs). BrS iPSC-CMs showed reductions in inward Na+ current density and reduced maximal upstroke velocity of action potential compared to healthy control iPSC-CMs. Furthermore, BrS iPSC-CMs showed increased burden of triggered activity, abnormal Ca2+ transients, and beating interval variation. Correction of the causative variant by genome editing was performed and resultant iPSC-CMs showed resolution of triggered activity and abnormal Ca2+ transients. Gene expression profiling of iPSC-CMs showed clustering of BrS compared to controls. Furthermore, BrS iPSC-CM gene expression correlated with gene expression from BrS human cardiac tissue gene expression.
Conclusions
Patient-specific iPSC-CMs are able to recapitulate single cell phenotype features of BrS, including blunted inward sodium current, increased triggered activity and abnormal Ca2+ handling. This novel human cellular model creates future opportunities to further elucidate cellular disease mechanism and identify novel therapeutic targets.
Considering the superior
ultraviolet (UV) absorptivity and environmental
friendliness of lignin, a novel lignin-based microsphere was prepared.
Through self-assembly, sodium lignosulfonate (SL) and cetyltrimethylammonium
bromide (CTAB) aggregated into uniform colloidal spheres (SL-CTAB).
SL-CTAB performed a reversible aggregation behavior and was used as
the shell material to prepare microspheres to encapsulate avermectin
(AVM), a kind of photosensitive pesticide. Moreover, the microsphere
(AVM@SL-CTAB) exhibited an uniform spherical structure. To reveal
the excellent embedding capability of AVM@SL-CTAB, the controlled
release and antiphotolysis performance for AVM were systematically
investigated in this work. As a result, the encapsulation efficiency
value of AVM@SL-CTAB reached to 62.58 ± 0.06%. The release of
AVM from AVM@SL-CTAB was still going on after 70 h, and its cumulative
release amount at that time was 49.96 ± 1.13%. The release process
of AVM@SL-CTAB could be controlled by adjusting the doped proportion
of SL-CTAB. The half-life (DT50) of AVM in AVM@SL-CTAB
under UV irradiation could be prolonged for 7.35 times that of uncoated
AVM. The enhanced photoprotection and the controlled release of AVM
implied that SL-CTAB possessed a great application prospect for efficient
pesticide utilization.
Recent in vitro cardiac safety studies demonstrate the ability of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to detect electrophysiologic effects of drugs. However, variability contributed by unique approaches, procedures, cell lines, and reagents across laboratories makes comparisons of results difficult, leading to uncertainty about the role of hiPSC-CMs in defining proarrhythmic risk in drug discovery and regulatory submissions. A blinded pilot study was conducted to evaluate the electrophysiologic effects of 8 well-characterized drugs on 4 cardiomyocyte lines using a standardized protocol across 3 microelectrode array platforms (18 individual studies). Drugs were selected to define assay sensitivity of prominent repolarizing currents (E-4031 for IKr, JNJ303 for IKs) and depolarizing currents (nifedipine for ICaL, mexiletine for INa) as well as drugs affecting multichannel block (flecainide, moxifloxacin, quinidine, and ranolazine). Inclusion criteria for final analysis was based on demonstrated sensitivity to IKr block (20% prolongation with E-4031) and L-type calcium current block (20% shortening with nifedipine). Despite differences in baseline characteristics across cardiomyocyte lines, multiple sites, and instrument platforms, 10 of 18 studies demonstrated adequate sensitivity to IKr block with E-4031 and ICaL block with nifedipine for inclusion in the final analysis. Concentration-dependent effects on repolarization were observed with this qualified data set consistent with known ionic mechanisms of single and multichannel blocking drugs. hiPSC-CMs can detect repolarization effects elicited by single and multichannel blocking drugs after defining pharmacologic sensitivity to IKr and ICaL block, supporting further validation efforts using hiPSC-CMs for cardiac safety studies.
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