Directed differentiation methods allow acquisition of high-purity cardiomyocytes differentiated from human induced pluripotent stem cells (hiPSCs); however, their immaturity characteristic limits their application for drug screening and regenerative therapy. The rapid electrical pacing of cardiomyocytes has been used for efficiently promoting the maturation of cardiomyocytes, here we describe a simple device in modified culture plate on which hiPSCderived cardiomyocytes can form three-dimensional self-organized tissue rings (SOTRs). Using calcium imaging, we show that within the ring, reentrant waves (ReWs) of action potential spontaneously originated and ran robustly at a frequency up to 4 Hz. After 2 weeks, SOTRs with ReWs show higher maturation including structural organization, increased cardiac-specific gene expression, enhanced Ca 2+-handling properties, an increased oxygenconsumption rate, and enhanced contractile force. We subsequently use a mathematical model to interpret the origination, propagation, and long-term behavior of the ReWs within the SOTRs.

A polyoxotungstate-surfactant hybrid layered compound was synthesized as a single phase by using decatungstate ([W 10 O 32 ] 4− , W 10 ) and hexadecylpyridinium (C 16 py).The X-ray structure analysis combined with infrared spectroscopy and elemental analysis revealed the formula to be (C 16 py) 4 [W 10 O 32 ] (C 16 py-W 10 ). The layered structure consisted of alternative stacking of W 10 inorganic monolayers and interdigitated C 16 py bilayers with layered periodicity of 23.3 Å. Each W 10 anion in the W 10 inorganic monolayers was isolated by the hydrophilic heads of C 16 py. The hybrid crystals of C 16 py-W 10 decomposed at around 500 K. The conductivity of the hybrid layered crystal was estimated to be 4.8 × 10 −6 S cm −1 at 423 K by alternating current (AC) impedance spectroscopy.

SummaryWe show that a human pluripotent stem cell (hPSC) population cultured on a low-adhesion substrate developed two hPSC subtypes with different colony morphologies: flat and domed. Notably, the dome-like cells showed higher active proliferation capacity and increased several pluripotent genes’ expression compared with the flat monolayer cells. We further demonstrated that cell-matrix adhesion mediates the interaction between cell morphology and expression of KLF4 and KLF5 through a serum response factor (SRF)-based regulatory double loop. Our results provide a mechanistic view on the coupling among adhesion, stem cell morphology, and pluripotency, shedding light on the critical role of cell-matrix adhesion in the induction and maintenance of hPSC.

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