Prachyl, Hannah

Acute atrial ischemia is a well-known cause of postoperative atrial fibrillation (POAF). However, mechanisms through which ischemia contributes to the development of POAF are not well understood. In this study, ex vivo Langendorff perfusion was used to induce acute ischemia/reperfusion in the heart to mimic POAF. Inducibility of atrial fibrillation (AF) was evaluated using programmed electrical stimulation and verified with open-atrium optical mapping. Compared with the control group without ischemia, 25 minutes of ischemia substantially increased the incidence of AF. The right atrium was more susceptible to AF than the left atrium. Administering insulin for 30 minutes before ischemia and during reperfusion with 25 minutes of ischemia greatly reduced the vulnerability to AF. However, insulin treatment during reperfusion only did not show substantial benefits against AF. Optical mapping studies showed that insulin mitigated ischemia-induced abnormal electrophysiology, including shortened action potential duration and effective refractory period, slowed conduction velocity, increased conduction heterogeneity, and altered calcium transients. In conclusion, insulin reduced the risk of acute ischemia/reperfusion–induced AF via improving the electrophysiology and calcium handling of atrial cardiomyocytes, which provides a potential therapy for POAF.

Heart disease continues to be the leading cause of death globally, even with the development and implementation of numerous pharmacological and surgical treatments. Transplanting cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) shows potential for repairing heart damage. However, tracking and quantifying these cells after transplantation in large animals remains challenging. This study aimed to develop a hiPSC line that overexpresses ferritin heavy chain (FHC) to enable tracking of transplanted hiPSC-CMs via magnetic resonance imaging (MRI). Using the CRISPR/dCas9 activation system, we increased FHC expression in hiPSCs and hiPSC-CMs. Both mRNA and protein levels of FHC were significantly elevated following transfection. Cell viability was unaffected by iron chloride concentrations between 0 μM and 2000 μM. hiPSCs and hiPSC-CMs overexpressing FHC (hiPSC-FHC OE and hiPSC-CM-FHC OE ) showed enhanced iron chloride uptake without changes in their electrophysiological properties compared to control hiPSC-CMs. Additionally, hiPSC-CM-FHCOE cells provided strong contrast and lower T 2 * values, indicating their effectiveness for cardiac MRI. When hiPSC-CM-FHCOE cells were injected into mouse hearts and imaged three days later, MRI revealed distinct signals from these cells with lower T 2 * values and rapid signal decay. Overall, endogenous FHC labeling in hiPSC-CMs could significantly improve the precision of cardiac MRI, marking a crucial advancement in assessing the success of hiPSC-CM transplantation in large animal models and enhancing cardiac regenerative therapies.

AbstractThe objective of the current study is to develop a new method for tracking transplanted human induced pluripotent stem cells‐derived cardiomyocytes (hiPSC‐CMs) using magnetic resonance imaging (MRI). The CRISPR/dCas9 activation system is employed to overexpress ferritin heavy chain (FHC) in hiPSC‐CMs. The mRNA and protein expression of FHC in hiPSC and hiPSC‐CMs significantly increased after transfection. Iron chloride does not affect the cell viability in a concentration range from 0 to 2000 µm. hiPSCs overexpressing FHC (hiPSC‐ FHCOE) and hiPSC‐CMs overexpressing FHC (hiPSC‐CM‐FHCOE) significantly enhanced cellular uptake of iron chloride but with no changes in electrophysiological properties compared to hiPSC‐CM‐Control. Furthermore, hiPSC‐CM‐FHCOE presented robust contrast and lower T2* values, signifying their potential as highly effective candidates for cardiac MRI. Next, hiPSC‐CM‐FHCOE is injected into mouse hearts and after 3 days of transplantation, MR images are obtained. hiPSC‐CM‐FHCOE cells exhibited clear signals in the hearts with lower T2* and rapid signal decay. Collectively, data from this proof‐of‐concept study demonstrated that endogenous labeling with FHC in hiPSC‐CMs can be a potent strategy for enhancing the accuracy of cardiac MRI. This technology represents a significant step forward in tracking the transplanted hiPSC‐CMs in the hearts of live animals.