Abstract

The reprogramming of somatic cells to a spontaneously contracting cardiomyocyte-like state using defined transcription factors has proven successful in mouse fibroblasts. However, this process has been less successful in human cells, thus limiting the potential clinical applicability of this technology in regenerative medicine. We hypothesized that this issue is due to a lack of cross-species concordance between the required transcription factor combinations for mouse and human cells. To address this issue, we identified novel transcription factor candidates to induce cell conversion between human fibroblasts and cardiomyocytes, using the network-based algorithm Mogrify. We developed an automated, high-throughput method for screening transcription factor, small molecule, and growth factor combinations, utilizing acoustic liquid handling and high-content kinetic imaging cytometry. Using this high-throughput platform, we screened the effect of 4,960 unique transcription factor combinations on direct conversion of 24 patient-specific primary human cardiac fibroblast samples to cardiomyocytes. Our screen revealed the combination of MYOCD, SMAD6, and TBX20 (MST) as the most successful direct reprogramming combination, which consistently produced up to 40% TNNT2+ cells in just 25 days. Addition of FGF2 and XAV939 to the MST cocktail resulted in reprogrammed cells with spontaneous contraction and cardiomyocyte-like calcium transients. Gene expression profiling of the reprogrammed cells also revealed the expression of cardiomyocyte associated genes. Together, these findings indicate that cardiac direct reprogramming in human cells can be achieved at similar levels to those attained in mouse fibroblasts. This progress represents a step forward towards the clinical application of the cardiac direct reprogramming approach. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/532629v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@17d6539org.highwire.dtl.DTLVardef@180a0b8org.highwire.dtl.DTLVardef@1b7cb46org.highwire.dtl.DTLVardef@182618b_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIUsing network-based algorithm Mogrify, acoustic liquid handling, and high-content kinetic imaging cytometry we screened the effect of 4,960 unique transcription factor combinations. C_LIO_LIUsing 24 patient-specific human fibroblast samples we identified the combination of MYOCD, SMAD6, and TBX20 (MST) as the most successful direct reprogramming combination. C_LIO_LIMST cocktail results in reprogrammed cells with spontaneous contraction, cardiomyocyte-like calcium transients, and expression of cardiomyocyte associated genes. C_LI