Generation of functional cardiomyocytes derived from human somatic cells and therapy for heart diseases
Authors: Johnson Rajasingh , Rajasingh Sheeja , Isai Dona Greta , Samanta Saheli , Cao Thuy , Czirok Andras 
Published: November 2023

Background and Hypothesis

Successful generation of induced pluripotent stem cells (iPSCs) and their differentiation into cardiomyocytes (iCMCs) have created exciting possibilities, wherein iCMCs may offer a renewable cell source for therapy, disease modeling and drug discovery. The major problem remains to generate safe, homogeneous, highly efficient functional iCMCs from adult somatic cells for drug screening and cell therapy. Thus, we hypothesize that the iPSC‐derived functional iCMCs would be a good in vitro model for drug screening and a superior source of cells for therapy in a mouse heart failure model.

Methods

Recently, we reported an approach of using highly efficient viral‐free combination of DNA and mRNA embryonic transcription factors to generate iPSCs and functional iCMCs from adult human cells. These differentiated iCMCs were characterized qualitatively and quantitatively by their genes and proteins expression. Furthermore, the contractility of chronotropic drugs treated and untreated iCMCs were measured and analyzed by our new particle image velocimetry (PIV) method followed by divergence and Fourier's spectrum analyses. We also compared our PIV technique with available standard confocal calcium transient imaging analysis. Finally, to see the therapeutic potential, we have transplanted these iCMCs intramyocardially in a mouse heart failure model.

Results

We attained the following observations: We identified a new combination of mature CMC cell‐surface markers CD36 and γ‐sarcoglycan to isolate a homogenous population from the CMCs differentiated culture by FACS analysis. To follow the in vitro differentiation process of CMC cultures, we recorded and analyzed the same areas at various time points using high frame rate video microscopy. Our PIV image analysis technique provided beat patterns: time‐series data of tissue displacement, measured relative to a resting reference state. The beat patterns revealed that the contractility of early CMC nodes was asynchronous in space and irregular in time (days 8 and 13). During subsequent days as the CMCs matured, contractile centers became synchronous (day 15). Our optically recorded beat patterns were in good agreement with the calcium‐imaging signal. In our in vitro drug screening systems, isoproterenol resulted in a substantial and sustained increase in beat frequency without triggering arrhythmias, on an in vitro day 14 CMC culture. Our day 35 post‐echocardiography data showed a significant improvement in the cardiac functions in iCMCs treated mice over the untreated control mice. Moreover, the fluorescence imaging data showed that the injected cells were stained positive for human nuclear antigen, integrin‐β antigen and human cardiotroponin T (CTT), suggesting the presence of iCMCs at the 35‐day post‐transplanted mouse heart.

Conclusion

Overall, these in vitro data offer new opportunities to model cardiac diseases and allow efficient screening of drug effects at various stages of cardiac developments. Furthermore, our in vivo data showed that the human adult somatic cell‐derived iCMCs were engrafted well and also functional in the failing mouse heart, suggesting its therapeutic application.

Support or Funding Information

American Heart Association Grant‐in Aid