Generation of induced pluripotent stem cells (iPSCs) has opened new avenues for the investigation of heart diseases, drug screening and potential autologous cardiac regeneration. However, their application is hampered by inefficient cardiac differentiation, high interline variability, and poor maturation of iPSC-derived cardiomyocytes (iPS-CMs). To identify efficient inducers for cardiac differentiation and maturation of iPSCs and elucidate the mechanisms, we systematically screened sixteen cardiomyocyte inducers on various murine (m) iPSCs and found that only ascorbic acid (AA) consistently and robustly enhanced the cardiac differentiation of eleven lines including eight without spontaneous cardiogenic potential. We then optimized the treatment conditions and demonstrated that differentiation day 2-6, a period for the specification of cardiac progenitor cells (CPCs), was a critical time for AA to take effect. This was further confirmed by the fact that AA increased the expression of cardiovascular but not mesodermal markers. Noteworthily, AA treatment led to approximately 7.3-fold (miPSCs) and 30.2-fold (human iPSCs) augment in the yield of iPS-CMs. Such effect was attributed to a specific increase in the proliferation of CPCs via the MEK-ERK1/2 pathway by promoting collagen synthesis. In addition, AA-induced cardiomyocytes showed better sarcomeric organization and enhanced responses of action potentials and calcium transients to β-adrenergic and muscarinic stimulations. These findings demonstrate that AA is a suitable cardiomyocyte inducer for iPSCs to improve cardiac differentiation and maturation simply, universally, and efficiently. These findings also highlight the importance of stimulating CPC proliferation by manipulating extracellular microenvironment in guiding cardiac differentiation of the pluripotent stem cells.

No abstract

Surface-capping agents play key roles in cellular uptake and biological activity of functional nanomaterials. In the present study, functionalized selenium nanoparticles (SeNPs) have been successfully synthesized using Polyporus rhinocerus water-soluble polysaccharide-protein complexes (PRW) as the capping agent during the reduction of selenium salts. The acquired monodisperse, spherical PRW-SeNPs presented desirable size distribution and stability in the solution. Moreover, PRW surface decoration significantly enhanced the cellular uptake of SeNPs via endocytosis. Exposure to PRW-SeNPs significantly inhibited the growth of A549 cells through induction of apoptosis and G2/M phase arrest (IC50 = 4.06 ± 0.25 μM) supported by an increase of sub-G1 and G2/M phase cell populations, DNA fragmentation, and chromatin condensation. Caspase-3/8 activation induced by PRW-SeNPs indicated that the activation of death receptors was the main cause of PRW-SeNP-induced apoptosis. Collectively, the results suggest that it is highly efficient to use PRW as a surface decorator of SeNPs to enhance cellular uptake and anticancer efficacy, and the PRW-SeNPs are potential chemopreventive agents for lung cancer therapy.