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Lineage reprogramming has become a potential strategy for therapy of cardiac diseases. Somatic cells can be directly converted into the induced cardiomyocytes (iCMs) without passing through an induced pluripotent stem cell stage; this strategy has some advantages such as directional differentiation and preferable security. However, there are still many challenges which need to be further studied, such as identification of safer induced factors, exploration of molecular mechanisms, improvement of the mature level of iCMs and so on. Therefore, the structures of key factors, including transcription factors, microRNAs (miRNAs), epigenetic regulators and small molecules and their functions in the cardiac development and lineage reprogramming, molecular mechanisms underlying lineage conversion, strategies for generating matured iCMs, and major challenges were reviewed to lay the foundation for further applications of iCMs.

Reprogramming mediated with proteins provides a novel, simpler, and safer strategy for generating induced pluripotent stem cells (iPSCs); in order to efficiently produce the recombination proteins and optimize the gene delivery system, different agents were screened to efficiently transfect plasmid DNA (pDNA) encoding "Yamanaka factor" (Oct 4, Sox 2, Klf 4, or c-Myc) into human embryonic kidney (HEK)-293T cells. The results indicated that 10 μg/mL Poly-MAG (polyethyleneimine (PEI)-MIONP) combined with exogenous magnetic field, 5 μg/mL Lipofectamine® 2000, and 40 μg/mL PEI were, respectively, more suitable to deliver the pDNA encoding Oct 4 into HEK-293T cells in the same transfection reagent groups, but the cell survival rate in 10 μg/mL Poly-MAG treatment group was significantly higher than that in the latter two groups (P < 0.01). "Yamanaka factor" recombination proteins could be extracted and purified from enhanced green fluorescent protein positive (EGFP+) HEK-293T cells. These recombination proteins could be delivered into fibroblasts of miniature pig via the actions of poly-arginine 9R, Poly-MAG, and exogenous magnetic field, producing iPSC-like cells. Furthermore, these iPSC-like cells with MIONPs would be enriched under the action of magnetic force. Therefore, the synergistic action of Poly-MAG and exogenous magnetic field could not only mediate the gene delivery of "Yamanaka factor", but also enhance the transmembrane of functional recombination proteins and enrichment of generated iPSC-like cells, which laid a solid foundation for future safer iPSC-based targeted therapies. [ABSTRACT FROM AUTHOR]