Posts Tagged: cardiomyocytes

Physiologic, Pathologic, and Therapeutic Paracrine Modulation of Cardiac Excitation-Contraction Coupling

Physiologic, Pathologic, and Therapeutic Paracrine Modulation of Cardiac Excitation-Contraction Coupling

Joshua Mayourian, Delaine K. Ceholski, David M. Gonzalez, Timothy J. Cashman, Susmita Sahoo, Roger J. Hajjar, Kevin D. Costa

Endothelial–cardiomyocyte interplay through paracrine factors. Endothelial cell NO increases basal contractility via nitrosylation of L-type Ca2+ channel (LTCC) and ryanodine receptor (RyR2). NO attenuates β-adrenergic effects on cardiomyocyte excitation–contraction coupling via cGMP-dependent degradation of cAMP and protein kinase G (PKG)-mediated decrease of LTCC activity. PKG also phosphorylates troponin I, leading to myofilament calcium desensitization and thus increased lusitropy. Endothelin-1, which mainly acts through the endothelin A (ETA) receptor in ventricular cardiomyocytes, may increase calcium entry via protein kinase C (PKC)-mediated (1) increase of LTCC activity, (2) indirect activation of sodium–calcium exchanger (NCX) reverse mode by increasing Na+–H+ exchanger activity, and (3) direct activation of NCX reverse (shown) and forward (not shown) mode. Endothelin-1 alters myofilament Ca2+ sensitivity via protein kinase C/D (PKC/D) phosphorylation of troponin I and myosin-binding protein C. Finally, endothelin-1 may increase calcium-induced calcium release via inositol trisphosphate (IP3) activation of inositol trisphosphate receptor (IP3R), which sensitizes RyR2 on the sarcoplasmic reticulum (SR). Green and red arrows denote activation and inhibition, respectively. PLB indicates phospholamban; and SERCA, sarcoendoplasmic reticulum Ca2+-ATPase. [Powerpoint File]

Physiologic, Pathologic, and Therapeutic Paracrine Modulation of Cardiac Excitation-Contraction Coupling

Physiologic, Pathologic, and Therapeutic Paracrine Modulation of Cardiac Excitation-Contraction Coupling

Joshua Mayourian, Delaine K. Ceholski, David M. Gonzalez, Timothy J. Cashman, Susmita Sahoo, Roger J. Hajjar, Kevin D. Costa

Human engineered cardiac tissue (hECT) contractility assay. A, hECTs are created, cultured, and tested in a custom bioreactor with integrated force-sensing end-posts; as the tissue beats, deflections of the end-posts are tracked. Output contractile metrics include, but are not limited to, developed force (DF), maximum rates of contraction and relaxation (+/− dF/dt, respectively), and beat rate. B, Confocal microscopy of hECTs labeled with cardiac troponin I (green) and DAPI (4’,6-diamidino-2-phenylindole; blue) displays cardiomyocytes with striated sarcomeres and regions of aligned myofibrils. Inset shows magnified view of registered sarcomeres. C, hECT labeled with sarcoendoplasmic reticulum Ca2+-ATPase 2 (red) and DAPI (blue) shows sarcoplasmic reticulum structures distributed throughout the tissue. Bar = 40 µm. [Powerpoint File]

Developmental and Regenerative Biology of Multipotent Cardiovascular Progenitor Cells

Developmental and Regenerative Biology of Multipotent Cardiovascular Progenitor Cells

Anthony C. Sturzu, Sean M. Wu

Proposed cellular hierarchy of cardiac progenitor cells and their lineage diversification. Precursors for heart-forming cells in the vertebrate mesoderm transition from expressing brachyury T to Mesp1 when they enter the precardiac mesoderm stage of development. As these early cardiac mesodermal cells contribute to the developing heart, their transcriptional program determines their further lineage specification. Within the second heart field, Isl1, together with Nkx2.5 and Flk1, defines multipotent Isl1+ cardiovascular progenitor cells that can give rise to myocardial, conduction system, smooth muscle, and endothelial lineages. A subset of precursors derived from Isl1+ progenitors may function as more restricted bipotent progenitors, displaying myocardial and smooth muscle potential or endothelial and smooth muscle potential. The developmental potential of the first heart field progenitors is largely uncharacterized. Epicardial progenitor cells are marked by Wt1 and/or Tbx18. These cells have been shown to give rise to cardiomyocytes, smooth muscle, endothelial cells, and fibroblasts in the heart. CD31 (PECAM 1) indicates platelet/endothelial cell adhesion molecule; cTnT, cardiac troponin T; DDR2, discoidin domain receptor 2; FHF, first heart field; HCN4, potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 4; SHF, second heart field; sm-actin, smooth muscle actin; smMHC, smooth muscle myosin heavy chain. (Illustration Credit: Cosmocyte/Ben Smith). [Powerpoint File]