[1]Zhongshan Hosp, Fudan Univ, Shanghai, China.
Although induced pluripotent stem cells (iPSCs)-derived cardiomyocytes are expected as the potential source of cell-based therapy for heart diseases, the rate of derivation is too low for clinical application. Recently, we used a functional proteomic analysis to screen out nucleosome assembly protein 1-like 1 (Nap1l1) which was downregulated during the differentiation of P19CL6 cells into cardiomyocytes. Here, we attempted to study the role of Nap1l1 in the cardiogenesis of iPSCs. We observed Nap1l1 was downregulated during the differentiation of iPSCs. Nap1l1 knockdown dramatically enhanced the differentiation of iPSCs into cardiomyocytes characterized by the increased number of beating embryonic bodies (EBs), the larger alpha-myosin heavy chain (α-MHC)-stained area and the upregulation of cardiac transcription factors (Nkx2.5, GATA4, et al). Cardiomyocytes derived from Nap1l1-knockdown-iPSCs exhibited proper cell biological characteristics judged from subcellular structure and their response to neurohormonal triggers. The cardiogenic effect was sharply inhibited by inducible Nap1l1 overexpression in iPSCs only at early-stage during the differentiation process. Further study revealed that Nap1l1 negatively induced mesoderm (Flk1, Brachyury and Mesp1) development. However, the same number of mesoderm stem cells (Flk1 positive cells) from Nap1l1-knockdown-, Nap1l1-overexpressed or their control-iPSCs didn"t show obvious difference in cardiomyocyte differentiation. Inducible Nap1l1 overexpression in iPSCs at late-stage during differentiation process didn"t affect cardiomyocytes induction. These data suggest that Nap1l1 knockdown promotes cardiomyocytes differentiation by mesoderm induction. Next study indicated that Nap1l1 positively regulated Notch intracellular domain (NICD) and downstream genes during differentiation of iPSCs. Notch signaling inhibitor greatly rescued the inhibitory effects of Nap1l1 on mesoderm induction and cardiogenesis. These findings demonstrate that downregulation of Nap1l1 significantly enhances mesodermal induction and subsequently promotes cardiogenesis from mouse iPSCs via regulating Notch signaling, which will facilitate application of iPSCs to heart diseases.
(8.0+极速模式)