Lineage-tracing system showed that reprogrammed iCMs were derived from fibroblasts rather than other lineage s and could be enhanced by IMAP.
A, schematic diagram of lineage-tracing system using another two lentiviral plasmids, LV-Thy1.2-Cre pLKO.1 and pMSCV-loxp-dsRed-loxp-eGFP-Puro-WPRE, in which iCMs derived from fibroblasts showed green and iCMs derived from other lineages showed red under fluorescence microscope. B, representative FACS plots showing the validation and viral infection efficiency of lineage-tracing system. C, quantification of spontaneous beating iCMs (green) per well of 48-well plate after 2, 3, and 4 weeks of reprogramming in lineage-tracing system under fluorescence microscope. D, schematic representation of the strategy for generating a calcium transient detection mouse line by crossing α-MHC–Cre mouse line with Rosa26A-Flox-Stop-Flox-GCaMP3 mouse line. E, representative images of iCMs exhibiting calcium transient. F, quantification of NCFs (control) or iCMs with calcium transient activities after 2 weeks of reprogramming followed by another 2 weeks of mature medium treatment. (n = 30 from 10 wells). Error bars indicate mean ± S.E.; *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001compared with MGT+DMSO group.