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Producing Praiseworthy Progenitors with Protein!

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Review of “Generation of Functional Human Cardiac Progenitor Cells by High-Efficiency Protein Transduction” from Stem Cells Translational Medicine by Stuart P. Atkinson

Direct lineage reprogramming of one cell type to another to provide a reliable source of transplantable cells is an exciting alternative to the generation and differentiation of induced pluripotent stem cells (iPSCs). Reprogramming strategies using the direct delivery of proteins does not need viral transduction or DNA integration, although currently used techniques suffer from low efficiency and alternative strategies are much sought after.

Now, researchers from the laboratories of Xi-Yong Yu (Guangzhou Medical University, People’s Republic of China) and Jianjun Wang (Wayne State University School of Medicine, USA) have studied the direct reprogramming of human dermal fibroblasts (HDFs) into cardiac progenitor cells (CPCs) using the QQ-protein transduction technique which can deliver proteins into mammalian cells with high efficiency and low cytotoxicity [1]. They hope that this report will lay the foundation for new cardiomyocyte regeneration strategies following myocardial infarction (Ml) [2].

The QQ-reagent is a cocktail of the polyethylenimine (PE1) and DOTAP/DOPE transfection reagents which, after mixing with the protein of choice and incubating with cells, can mediate a near 100% transfection efficiency with little or no cytotoxic side effects. Sounds good so far! For this study, the authors used the QQ reagents to transduce HDFs with cardiac transcription factor proteins (Gata4/Hand2/Mef2c/Tbx5 [3, 4]) in the presence of BMP4, activin A, and bFGF. This strategy produced protein-induced cardiac progenitor cells (piCPCs) at an efficiency of around 80%. Good just got better.

The piCPCs produced showed many similarities to cardiac progenitors - morphological appearance, colony formation, a reduction in fibroblast genes and an increase in cardiac progenitor marker expression, and chromatin remodeling of important cardiac gene regulatory regions. Following reprogramming to the CPC stage, the application of a modified cardiac differentiation strategy [5] using an inhibitor of the canonical Wnt pathway (IWR-1) enabled the production of three cardiac cell types - beating cardiomyocytes, endothelial cells, and smooth muscle cells – suggesting that CPCs may be highly therapeutically relevant.

But do piCPCs have any therapeutic effect in the treatment of MI? To test this, the study followed the consequences of injecting piCPCs into rat heart tissue following induced MI. This attenuated left ventricular remodeling, decreased fibrosis (See figure), and enhanced heart cell differentiation, all indicative of a high regenerative/reparative function of transplanted piCPCs.

While the authors note that this process requires further optimization, this study does demonstrate the efficient generation of functional cardiac progenitors without the need for viral transduction. The authors suggest that further modulation of the chromatin environment and the in-depth study of in vivo differentiated cardiomyocytes may improve their already safe and effective method, and make piCPCs an excellent alternative strategy for the treatment of the failing heart.

References

  1. Li Q, Huang Y, Xiao N, et al. Real time investigation of protein folding, structure, and dynamics in living cells. Methods Cell Biol 2008;90:287-325.
  2. Li X-H, Li Q, Jiang L, et al. Generation of Functional Human Cardiac Progenitor Cells by High-Efficiency Protein Transduction. Stem Cells Translational Medicine 2015;4:1415-1424.
  3. Olson EN Gene regulatory networks in the evolution and development of the heart. Science 2006;313:1922-1927.
  4. Srivastava D Making or breaking the heart: from lineage determination to morphogenesis. Cell 2006;126:1037-1048.
  5. Efe JA, Hilcove S, Kim J, et al. Conversion of mouse fibroblasts into cardiomyocytes using a direct reprogramming strategy. Nat Cell Biol 2011;13:215-222.