Rabbit Anti-Human MEF2C (Phospho-Ser396) polyclonal antibody

Aged skeletal muscle has an attenuated and delayed ability to proliferate satellite cells in response to resistance exercise. The mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway is a focal point for cell growth, however, the effect of postexercise mTORC1 activation on human skeletal muscle satellite cell (SC) proliferation is unknown. To test the proliferative capacity of skeletal muscle SC in aging muscle to a potent mTORC1 activator (i.e., EAA; essential amino acids) we recruited older (similar to 72y) men to conduct leg resistance exercise (8setsx10reps) without (-EAA; n=8) and with (+EAA: n=11) ingestion of 10g of EAA 1h postexercise. Muscle biopsies were taken before exercise (Pre) and 24h postexercise (Post) for assessment of expression and fiber type-specific Pax7(+) SC, Ki67(+)Pax7(+) SC and MyoD(+) SC. -EAA did not show an increase in Pax7(+) satellite cells at Post(P>0.82). Although statistical significance for an increase in Pax7+ SC at 24h post-RE was not observed in +EAA versus -EAA, we observed trends for a treatment difference (P<0.1). When examining the change from Pre to Post trends were demonstrated (#/myofiber: P=0.076; and %/myonuclei: P=0.065) for a greater increase in +EAA versus -EAA. Notably, we found an increase SC proliferation in +EAA, but not -EAA with increase in Ki67(+) SC and MyoD(+) cells (P<0.05). Ki67(+) SC also exhibited a significant group difference Post (P<0.010). Pax7(+) SC in fast twitch myofibers did not change and were not different between groups (P>0.10). CDK2, MEF2C, RB1 mRNA only increased in +EAA (P<0.05). Acute muscle satellite cell proliferative capacity may be partially rescued with postexercise EAA ingestion in older men.

Sonic hedgehog (Shh) signaling plays an important role for early heart development, such as heart looping and cardiomyogenesis of pluripotent stem cells. A multifunctional receptor Cdo functions as a Shh coreceptor together with Boc and Gas1 to activate Shh signaling and these coreceptors seem to play compensatory roles in early heart development. Thus in this study, we examined the role of Cdo in cardiomyogenesis by utilizing an in vitro differentiation of pluripotent stem cells. Here we show that Cdo is required for efficient cardiomyogenesis of pluripotent stem cells by activation of Shh signaling. Cdo is induced concurrently with Shh signaling activation upon induction of cardiomyogenesis of P19 embryonal carcinoma (EC) cells. Cdo-depleted P19 EC and Cdo(-/-) mouse embryonic stem (ES) cells display decreased expression of key cardiac regulators, including Gata4, Nkx2.5 and Mef2c and this decrease coincides with reduced Shh signaling activities. Furthermore Cdo deficiency causes a stark reduction in formation of mature contractile cardiomyocytes. This defect in cardiomyogenesis is overcome by reactivation of Shh signaling at the early specification stage of cardiomyogenesis. The Shh agonist treatment restores differentiation capacities of Cdo-deficient ES cells into contractile cardiomyocytes by recovering both the expression of early cardiac regulators and structural genes such as cardiac troponin T and Connexin 43. Therefore Cdo is required for efficient cardiomyogenesis of pluripotent stem cells and an excellent target to improve the differentiation potential of stem cells for generation of transplantable cells to treat cardiomyopathies. (C) 2016 Elsevier Ltd. All rights reserved.