Small molecule regulators of postnatal Nkx2.5 cardiomyoblast proliferation and differentiation
ABSTRACT While recent data have supported the capacity for a neonatal heart to undergo cardiomyogenesis, it is unclear whether these new cardiomyocytes arise from an immature cardiomyoblast population or from the division of mature cardiomyocytes. By following the expression of enhanced Green Fluorescent Protein (eGFP) in an Nkx2.5 enhancer-eGFP transgenic mice, we have identified a population of immature cells that can undergo cardiomyogenic as well as smooth muscle cell differentiation in the neonatal heart. Here, we examined growth factors and small molecule regulators that potentially regulate the proliferation and cardiomyogenic versus smooth muscle cell differentiation of neonatal Nkx2.5-GFP (+) cells in vitro. We found that A83-01 (A83), an inhibitor of TGF-βRI, was able to induce an expansion of neonatal Nkx2.5-eGFP (+) cells. In addition, the ability of A83 to expand eGFP (+) cells in culture was dependent on signalling from the mitogen-activated protein kinase kinase (MEK) as treatment with a MEK inhibitor, PD0325901, abolished this effect. On the other hand, activation of neonatal Nkx2.5-eGFP (+) cells with TGF-β1, but not activin A nor BMP2, led to smooth muscle cell differentiation, an effect that can be reversed by treatment with A83. In summary, small molecule inhibition of TGF-β signalling may be a promising strategy to induce the expansion of a rare population of postnatal cardiomyoblasts.
Full-textDOI: · Available from: Sean M Wu, May 28, 2015
[Show abstract] [Hide abstract]
ABSTRACT: Our previous study found that A83-01, a small molecule type 1 TGFβ receptor inhibitor, could induce proliferation of postnatal Nkx2.5+ cardiomyoblasts in vitro and enhance their cardiomyogenic differentiation. The present study addresses whether A83-01 treatment in vivo could increase cardiomyogenesis and improve cardiac function after myocardial infarction (MI) through an Nkx2.5+ cardiomyoblast-dependent process.Cardiovascular Research 10/2014; 105(1). DOI:10.1093/cvr/cvu229 · 5.81 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Perturbed biomechanical stimuli are thought to be critical for the pathogenesis of a number of congenital heart defects, including Hypoplastic Left Heart Syndrome (HLHS). While embryonic cardiomyocytes experience biomechanical stretch every heart beat, their molecular responses to biomechanical stimuli during heart development are poorly understood. We hypothesized that biomechanical stimuli activate specific signaling pathways that impact proliferation, gene expression and myocyte contraction. The objective of this study was to expose embryonic mouse cardiomyocytes (EMCM) to cyclic stretch and examine key molecular and phenotypic responses. Analysis of RNA-Sequencing data demonstrated that gene ontology groups associated with myofibril and cardiac development were significantly modulated. Stretch increased EMCM proliferation, size, cardiac gene expression, and myofibril protein levels. Stretch also repressed several components belonging to the Transforming Growth Factor-β (Tgf-β) signaling pathway. EMCMs undergoing cyclic stretch had decreased Tgf-β expression, protein levels, and signaling. Furthermore, treatment of EMCMs with a Tgf-β inhibitor resulted in increased EMCM size. Functionally, Tgf-β signaling repressed EMCM proliferation and contractile function, as assayed via dynamic monolayer force microscopy (DMFM). Taken together, these data support the hypothesis that biomechanical stimuli play a vital role in normal cardiac development and for cardiac pathology, including HLHS. Copyright © 2014 Elsevier Ltd. All rights reserved.Journal of Molecular and Cellular Cardiology 11/2014; 79C:133-144. DOI:10.1016/j.yjmcc.2014.11.003 · 5.22 Impact Factor