Cardiomyocytes (CMs) and mesenchymal stem cells (MSCs) are important cell types for cardiac repair post myocardial infarction. Here we proved that both CMs and MSCs can be simultaneously generated from human induced pluripotent stem cells (hiPSCs) via a pro-mesoderm differentiation strategy. Two hiPSC lines, hiPSC (1) and hiPSC (2) were generated from human dermal fibroblasts using OCT-4, SOX-2, KLF-4, c-Myc via retroviral-based reprogramming. H9 human embryonic stem cells (hESCs) served as control. CMs and MSCs were co-generated from hiPSCs and hESCs via embryoid body-dependent cardiac differentiation protocol involving a serum-free and insulin-depleted medium containing a p38 MAPK inhibitor, SB 203580. Comparing to bone marrow and umbilical cord blood-derived MSCs, hiPSC-derived MSCs (iMSCs) expressed common MSC markers and were capable of adipogenesis, osteogenesis and chondrogenesis. Moreover, iMSCs continuously proliferated for more than 32 population doublings without cellular senescence and showed superior pro-angiogenic and wound healing properties. In summary, we generated a large number of homogenous MSCs in conjunction with CMs in a low-cost and efficient one step manner. Functionally competent CMs and MSCs co-generated from hiPSCs may be useful for autologous cardiac repair.

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We investigated global and regional effects of myocardial transplantation of human induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells (iMSCs) in infarcted myocardium. Acute myocardial infarction (MI) was induced by ligation of left coronary artery of severe combined immunodeficient mice before 2 × 105 iMSCs or cell-free saline were injected into peri-infarcted anterior free wall. Sham-operated animals received no injection. Global and regional myocardial function was assessed serially at 1-week and 8-week by segmental strain analysis by using two dimensional (2D) speckle tracking echocardiography. Early myocardial remodelling was observed at 1-week and persisted to 8-week with global contractility of ejection fraction and fractional area change in saline- (32.96 ± 14.23%; 21.50 ± 10.07%) and iMSC-injected (32.95 ± 10.31%; 21.00 ± 7.11%) groups significantly depressed as compared to sham control (51.17 ± 11.69%, P < 0.05; 34.86 ± 9.82%, P < 0.05). However, myocardial dilatation was observed in saline-injected animals (4.40 ± 0.62 mm, P < 0.05), but not iMSCs (4.29 ± 0.57 mm), when compared to sham control (3.74 ± 0.32 mm). Furthermore, strain analysis showed significant improved basal anterior wall strain (28.86 ± 8.16%, P < 0.05) in the iMSC group, but not saline-injected (15.81 ± 13.92%), when compared to sham control (22.18 ± 4.13%). This was corroborated by multi-segments deterioration of radial strain only in saline-injected (21.50 ± 5.31%, P < 0.05), but not iMSC (25.67 ± 12.53%), when compared to sham control (34.88 ± 5.77%). Improvements of the myocardial strain coincided with the presence of interconnecting telocytes in interstitial space of the infarcted anterior segment of the heart. Our results show that localized injection of iMSCs alleviates ventricular remodelling, sustains global and regional myocardial strain by paracrine-driven effect on neoangiogenesis and myocardial deformation/compliance via parenchymal and interstitial cell interactions in the infarcted myocardium.

AimHydrogen sulfide (H2S) is a promising cardioprotective agent and a potential modulator of cardiac ion currents. Yet its cardiac effects on humans are poorly understood due to lack of functional cardiomyocytes. This study investigates electrophysiological responses of human pluripotent stem cells (hPSCs) derived cardiomyocytes towards H2S.Methods and ResultsCardiomyocytes of ventricular, atrial and nodal subtypes differentiated from H9 embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) were electrophysiologically characterized. The effect of NaHS, a donor of H2S, on action potential (AP), outward rectifier potassium currents (I Ks and I Kr), L-type Ca2+ currents (I CaL) and hyperpolarization-activated inward current (I f) were determined by patch-clamp electrophysiology and confocal calcium imaging. In a concentration-dependent manner, NaHS (100 to 300 µM) consistently altered the action potential properties including prolonging action potential duration (APD) and slowing down contracting rates of ventricular-and atrial-like cardiomyocytes derived from both hESCs and hiPSCs. Moreover, inhibitions of slow and rapid I K (I Ks and I Kr), I CaL and I f were found in NaHS treated cardiomyocytes and it could collectively contribute to the remodeling of AP properties.ConclusionsThis is the first demonstration of effects of H2S on cardiac electrophysiology of human ventricular-like, atrial-like and nodal-like cardiomyocytes. It reaffirmed the inhibitory effect of H2S on I CaL and revealed additional novel inhibitory effects on I f, I Ks and I Kr currents in human cardiomyocytes.

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