September 23, 2023

In a current examine printed within the journal Cell Stem Cell, researchers hypothesized that pacemaker-like exercise of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) resulted in engraftment arrhythmias (EAs), which hampers the medical use of cell-based remedy utilizing hPSC-CMs for therapy of myocardial infarction (MI).

Study: Gene editing to prevent ventricular arrhythmias associated with cardiomyocyte cell therapy. Image Credit: FrentaN / ShutterstockResearch: Gene editing to prevent ventricular arrhythmias associated with cardiomyocyte cell therapy. Picture Credit score: FrentaN / Shutterstock


The human coronary heart doesn’t have regeneration potential. So when non-contractile scar tissue takes the place of 1 billion grownup CMs after one MI episode, this impairs coronary heart perform, which, in flip, might even result in a coronary heart assault or coronary heart failure.

The invention of hPSCs has opened new avenues for MI therapy. Word extremely pure hPSC-CMs whose intra-myocardial transplantation kinds new myocardium grafts in infarcted hearts comply with pacing from the host’s sinoatrial (SA) node. These are below intensive investigation as candidates for the regeneration of the human coronary heart post-MI. Nevertheless, EAs, a transitory however sustained ventricular tachycardia (VT), hinder the medical use of hPSC-CMs-based cell remedy. Furthermore, in contrast to grownup ventricular CMs (vCMs), hPSC-CMs exhibit automaticity, the flexibility to spontaneously and rhythmically depolarize and set off motion potentials (APs).

Up to now, researchers have used mouse, rat, guinea pig, and non-human primate (NHP) fashions of subacute MI to look at the consequences of transplantation of hPSC-CMs. Throughout regular maturation of those cells, automaticity stays restricted to specialised cells within the pacemaking system, and in small animal fashions, excessive coronary heart charges usually masks EAs. Nevertheless, in massive animal fashions with coronary heart charges similar to people, i.e., 70 beats per minute [bpm], the transplantation of hPSC-CMs triggers EA inside every week, seemingly arising from the graft-host electrical coupling.

EA-triggered VT usually lasts one month (on common), taking the guts charges of pigs and NHPs to as much as 300 revolutions per minute (rpm), which, in some extreme instances, might be deadly for pigs. Nevertheless,  normally, EA wanes steadily because the graft matures. Since people won’t be capable of tolerate fast EA, it’s essential to establish methods that management EA until the time their graft attains maturity.

Invasive electrophysiology research in NHPs and pigs have additionally proven {that a} spontaneous aberrant impulse generated from the graft (as a result of hPSC-CMs exhibit shorter AP period as a result of extra depolarized membrane potential) results in EA relatively than conduction defects (i.e., re-entry pathways). It seems to be associated to a fetus-like gene expression profile for concerned ion channels. Thus, overdrive pacing and direct present (DC) cardioversion can not terminate EA.

Concerning the examine

The authors had beforehand proven that hPSC CMs transplanted into the infarcted coronary heart of a rat matured to exhibit adult-like myofibril isoform group. This mannequin intently mimicked the maturation milieu that hPSC-CMs would expertise inside people, thus, had extra medical and physiological relevance. On this mannequin, they carried out laser-capture microdissection (LCM) adopted by bulk ribonucleic acid-sequencing (RNA-seq) to characterize the genome-wide expression dynamics of hPSC-CMs throughout in vivo maturation, which took round 12 weeks.

To extract in vivo transplanted hiPSC-CMs from rat hearts, they transduced them with inexperienced fluorescent calmodulin (GCaMP3) earlier than grafting. For comparisons, they analyzed hiPSC-CMs cultured long-term in vitro for as much as one yr. Additionally they analyzed human-specific and rat-specific RNA-seq reads (or graft alerts) individually.

Then, the researchers got down to generate hPSC-CMs with lowered automaticity like grownup vCMs however with acceptable electrophysiological conduct, i.e., beating in response to electrical stimulation. To this finish, they used CRISPR/Cas9 expertise and systematically knocked out over expressive ion channel genes—singly and together.

The researchers characterised these hPSC-CMs in vitro and examined the influence of gene edits on EA in an in vivo mannequin, the unhurt hearts of immunosuppressed Yucata’ n minipigs, transplanted with 150 million hESC-CMs. They monitored their coronary heart fee and rhythm with a  steady electrocardiogram (ECG) system, which indicated their EA burden. Additional, they decided the expression dynamics of all ion channel genes post-hPSC-CM transplantation to curate an inventory of EA mediators and to engineer their electrophysiology towards an adult-like phenotype.

Additional, the researchers got down to perceive the drivers of automaticity in human embryonic stem cell-derived cardiomyocytes (hESC-CMs) differentiated by modulating the WNT signaling pathway with small molecules. To evaluate the position of particular ion currents, the researchers genetically manipulated candidate genes encoding for ion channels seemingly enjoying an necessary position in hESC-CM automaticity primarily based on obtainable transcriptomic and pharmacological knowledge, which helped them establish the minimal variety of gene edits wanted to nullify automaticity (or EA).


Single, double, and triple gene edits lowered the heartbeat fee and destabilized the SA node rhythm, however they might not get rid of automaticity or EA in vitro and in vivo, respectively. A quadruple edit or simultaneous knockout (KO) of 4 genes, HCN4, CACNA1H, and SLC8A1, coupled with overexpression of KCNJ2 termed MEDUSA eradicated the automaticity of hESC-CMs in vitro (in >10 cell traces) with out affecting the flexibility of those cells to fireside APs when stimulated, i.e., the cells had been quiescent but excitable.

Relative to wild-type (WT) controls and the opposite cell traces, transplantation of post-quadruple-gene edited CMs didn’t lead to sustained EA in vivo. Additionally, MEDUSA hESC-CMs engrafts had been secure for 3 months, beat synchronously with the host myocardium, and exhibited markedly attenuated VTs. These modifications additionally prevented pigs’ morbidity, mortality, and coronary heart failure post-hPSC-CM transplantation.

Gene expression profiles confirmed stronger and quicker maturation in vivo in comparison with in vitro tradition, which lagged after one yr in tradition. Inducing a extra adult-like ion-channel gene expression profile in hPSC-CMs lowered automaticity and, probably, the burden of EA after transplantation. Curiously, the examine outcomes highlighted the significance of Ca2+ trafficking in hESC-CM automaticity.


Additional research are wanted to check whether or not MEDUSA hESC-CMs might work successfully post-transplantation into infarcted rat hearts. It’s needed as a result of the researchers noticed that MEDUSA cells weren’t fully quiescent. Throughout warmth shock or different stress circumstances, they sometimes beat spontaneously.

Equally, transplantation-induced stresses, corresponding to ischemia or irritation, might induce related beating exercise in vivo, which could govern the self-restricted EA episodes noticed in the course of the transplantation of excessive doses of MEDUSA cells. Nonetheless, this examine confirmed a good profile of MEDUSA hESC-CMs in comparison with their WT counterparts. Furthermore, combining much less arrhythmogenic hESC-CMs with ivabradine may confer extra security advantages throughout medical trials.

To conclude, these outcomes offered new insights into the mechanisms behind the automaticity of hESC-CMs. Nevertheless, extra work is warranted to find out whether or not MEDUSA hESC-CM might probably restore systolic perform, an development wanted to securely revascularize the injured coronary heart.

Journal reference:

  • Gene modifying to forestall ventricular arrhythmias related to cardiomyocyte cell remedy, Silvia Marchiano, Kenta Nakamura, Hans Reinecke, Lauren Neidig, Michael Lai, Shin Kadota, Filippo Perbellini, Xiulan Yang, Jordan M. Klaiman, Leslie P. Blakely, Elaheh Karbassi, Paul A. Fields, Aidan M. Fenix, Kevin M. Beussman, Anu Jayabalu, Religion A. Kalucki, Jennifer C. Potter, Akiko Futakuchi-Tsuchida, Gerhard J. Weber, Sarah Dupras, Hiroshi Tsuchida, Lil Pabon, Lili Wang, Björn C. Knollmann, Steven Kattman, R. Scott Thies, Nathan Sniadecki, W. Robb MacLellan, Alessandro Bertero, Charles E. Murry, Cell Stem Cell 2023, DOI:,