Posts Tagged: cardiac myocytes

PI3K and Calcium Signaling in Cardiovascular Disease

PI3K and Calcium Signaling in Cardiovascular Disease

Alessandra Ghigo, Muriel Laffargue, Mingchuan Li, Emilio Hirsch

Class I PI3Ks (phosphoinositide 3-kinases). Class I PI3Ks are obligate heterodimers composed by a p110 catalytic module and an adaptor subunit. Depending on the nature of the adaptor and of the activating membrane receptor, class I PI3Ks can be subgrouped into class IA and IB. Class IA includes PI3Kα, β, and δ, which are coupled to a p85 regulatory subunit and are engaged by tyrosine kinase receptors (RTKs). On the contrary, the unique member of class IB, PI3Kγ, binds to either p101 or p87 that, by tethering p110γ to the Gβγ subunit of G protein-coupled receptors (GPCRs), ensure the full enzyme activation. All class I isoenzymes phosphorylate PIP2 PtdIns(4,5)P2 to produce PIP3 that, in turn, serves as a docking site for intracellular effectors carrying a lipid-binding domain, such as Akt (protein kinase B). Activated Akt ultimately initiates a wide spectrum of biological events, ranging from proliferation, survival, and metabolic regulation. [Powerpoint File]

PI3K and Calcium Signaling in Cardiovascular Disease

PI3K and Calcium Signaling in Cardiovascular Disease

Alessandra Ghigo, Muriel Laffargue, Mingchuan Li, Emilio Hirsch

PI3K (phosphoinositide 3-kinase)-mediated compartmentalization of β-adrenergic receptors-dependent Ca2+ responses in cardiomyocytes. Class IB PI3Kγ restrains Ca2+ signaling in response to β-adrenergic stimuli via a kinase-unrelated mechanism. This relies on the ability of PI3Kγ to anchor PDE (phosphodiesterase)3 or 4 to their activator PKA in specific subcellular compartments and to promote PKA-mediated activation of PDEs (active PDE3/4). The ensuing cyclic AMP (cAMP) reduction limits PKA-mediated phosphorylation and activation of Ca2+-handling proteins, including L-type Ca2+ channel (LTCC) and PLN (phospholamban; left). In heart failure, a functional decay in PI3Kγ-directed protein–protein interactions limits PDE activity (inactive PDE3/4), leading to abnormal cAMP accumulation and uncontrolled PKA activity close to LTCC and PLN, which culminate in arrhythmogenic Ca2+ release events (right). PLN indicates phospholamban; and SR, sarcoplasmic reticulum. [Powerpoint File]

Multimodal Regulation of Cardiac Myocyte Proliferation

Multimodal Regulation of Cardiac Myocyte Proliferation

Xuejun Yuan, Thomas Braun

Schematic overview of cell-cycle activities, global DNA methylation, and metabolic properties of fetal, neonatal, adult, and hypertrophic cardiac myocytes. Green arrows represent cell-cycle processes leading to endomitosis and multinucleation, whereas orange arrows refer to endoreduplication resulting in polyploidy. cTnI (TNNI3) indicates cardiac troponin; FAO, fatty acid oxidation; and ssTnI(TNNI1), slow skeletal troponin. [Powerpoint File]

Multimodal Regulation of Cardiac Myocyte Proliferation

Multimodal Regulation of Cardiac Myocyte Proliferation

Xuejun Yuan, Thomas Braun

Schematic overview of the potential interplay between metabolic signals and epigenetic mechanisms for regulation of cardiac myocyte proliferation. Oxygen-dependent stimulation of mitochondrial respiration increases α-ketoglutarate (α-KG) production, which might stimulate DNA and histone demethylation thereby activating anti-proliferative genes or inducing accumulation of intracellular reactive oxygen species (ROS) and DNA damage responses. Such cues might promote polyplodization and/or activation of Hippo signaling prompting cell-cycle exit. In contrast, hypoxia stabilizes HIF1α (hypoxia-inducible factor 1-alpha) and leads to accumulation of intermediate metabolites such as succinate and fumarate, which inhibit α-KG–dependent epigenetic modifiers including TETs (ten–eleven translocation) and histone demethylases (HDMs) and stabilize HIF1α thus activating proproliferative gene programs. In addition, fumarate activates the Nrf2/Pitx2/Yap1 axis, which positively regulates proproliferative gene programs. Dashed lines indicate regulatory cascades investigated in noncardiac myocytes. [Powerpoint File]

Engineering Cardiac Muscle Tissue: A Maturating Field of Research

Engineering Cardiac Muscle Tissue: A Maturating Field of Research

Florian Weinberger, Ingra Mannhardt, Thomas Eschenhagen

Histological structure of native mouse and rat heart (longitudinal mouse heart in A; cross section of rat heart in B), engineered heart tissue (EHT) from neonatal rat heart cells (longitudinal in C, E, cross section in D), or human pluripotent stem cell–derived cardiomyocytes (F–J). A, staining of actinin (green). B, Staining of sarcolemma with wheat germ agglutinin (white in B). C and D, Staining of actinin (red in C and I), F-actin (green in D and J), or actinin and troponin T (green/red in H) and nuclei in blue (all). E, Hematoxylin and eosin–stained paraffin section. A, Reprinted from Mearini et al135 with permission of the publisher. Copyright © 2014, Macmillan Publishers Limited. B, Reprinted from Bensley et al136 with permission. Copyright © 2016, The Authors. C, D, I, and J, Reprinted from Jackman et al35 with permission of the publisher. Copyright © 2016, Elsevier; and from Eschenhagen et al134 (E) with permission of the publisher. Copyright © 2012, the American Physiological Society. F, Reprinted from Hirt et al36 with permission of the publisher. Copyright © 2014, Elsevier. G, Reprinted from Mannhardt et al78 with permission. Copyright © 2016, The Authors. H, Riegler et al93 with permission of the publisher. Copyright © 2015, American Heart Association. [Powerpoint File]

Engineering Cardiac Muscle Tissue: A Maturating Field of Research

Engineering Cardiac Muscle Tissue: A Maturating Field of Research

Florian Weinberger, Ingra Mannhardt, Thomas Eschenhagen

Plane engineered heart tissue (EHT) on Velcro-covered rods (Eschenhagen et al2, A), ring EHTs (Zimmermann et al24, B), fibrin-based mini-EHT on PDMS (polydimethylsiloxane) racks (Hansen et al25, C), cardiac micro tissues (CMT) on fluorescent pillars (Boudou et al34, D), cardiobundles on PDMS frame (Jackman et al35, Copyright © 2016, Elsevier; E), micro heart muscle (Huebsch et al81, Copyright © 2016, The Authors; F), cardiac biowires (Nunes et al131, Copyright © 2013, Nature Publishing Group; G), cardiac patch (Bian et al133, H). Please note that scale bars are only representative, and sketches might not match the exact dimensions. Graphics in A, B, and D were modified from Eschenhagen et al134 with permission of the publisher. Copyright © 2012, the American Physiological Society. [Powerpoint File]

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

Sumanth D. Prabhu, Nikolaos G. Frangogiannis

Toll-like receptor (TLR) and nucleotide-binding oligomerization domain–like receptor (NLR) signaling. Danger-associated molecular patterns (DAMPs) released from necrotic and damaged cells and extracellular matrix bind to the TLRs, which comprised an extracellular leucine-rich repeat (LRR) domain, a transmembrane (TM) domain, and a conserved cytoplasmic Toll/interleukin (IL)-1R (TIR) domain, which serves as docking site for other TIR-containing cytoplasmic adaptor proteins (top left). The binding of DAMPs, and often coreceptors such as CD14 and MD2, to TLR4 engages the adaptor myeloid differentiation factor 88 (MyD88) via the adaptor TIR domain-containing adaptor protein (TIRAP). MyD88 recruits IL-1R–associated kinase (IRAK) 4 and the IRAK1/2 and TNF receptor associated factor (TRAF) 6 complex, which activates transforming growth factor activated kinase 1 (TAK1). TAK1, a mitogen-activated protein kinase (MAPK) KK, then activates the MAPK cascade and also phosphorylates IκB kinase (IKK), that leads to nuclear factor-κB (NF-κB) p65 and p50 nuclear translocation and the transcription of a panel of inflammatory genes, including cytokines, chemokines, cell adhesion molecules, and complement factor B. Furthermore, after endocytosis, TLR4 signals in a MyD88-independent manner via the cytoplasmic adaptor TRIF, in turn recruited through the bridging adaptor TRAM. This pathway results in noncanonical IKK and NF-κB activation, as well as the induction of type I interferon (IFN) via TANK-binding kinase (TBK) 1 and the transcription factor IFN-regulatory factor (IRF) 3. Except for TLR3, the other TLRs also signal, directly or indirectly as depicted, via MyD88. Endolysosomal TLR3 activates IRF3 signaling via TRIF and TBK1, whereas endolysosomal TLR7/8 and TLR9 also induce type I IFN via TRAF3 and IRF7 in a MyD88-dependent manner (not pictured). In addition to TLRs, intracellular NLRs respond to a variety of DAMPs via the formation of multiprotein inflammasomes, comprised an activated NLR protein, the adaptor protein apoptosis speck-like protein containing a caspase-recruitment domain (ASC), and procaspase-1. One proposed model of NLRP3 inflammasome activation results from stimulation of the purinergic P2X7 ion channel by extracellular ATP, resulting in K+ efflux, recruitment of the pannexin-1 pore, DAMP entry into cytosol, and activation of NLRP3. This activates caspase-1, which then converts pro–IL-18 and pro–IL-1β to active IL-18 and IL-1β. As discussed in the text, cell-type–specific innate immune signaling can result in distinctive, and sometimes divergent, in vivo physiological responses during acute MI. Schema derived from Mann,13 Newton and Dixit,14 Schroder and Tschopp,18 Chao,76 and Mann83 (Illustration credit: Ben Smith). [Powerpoint File]

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

Sumanth D. Prabhu, Nikolaos G. Frangogiannis

Cellular effectors and molecular signals that repress and resolve inflammation after myocardial infarction leading to the transition from the inflammatory to the proliferative phase of cardiac repair. Recruitment of anti-inflammatory monocyte (Mo) subsets (1), T-cell subpopulations, such as regulatory T cells (Tregs) (2) and invariant Natural Killer T cells (iNKT; 3) contributes to repression of the postinfarction inflammatory response. Moreover, members of the transforming growth factor (TGF)-β family (such as TGF-β1 and growth differentiation factor (GDF)-15 inhibit neutrophil transmigration by attenuating expression of adhesion molecules by endothelial cells (ECs) (4). Recruitment of pericytes (P) by microvascular ECs is mediated through platelet-derived growth factor (PDGF) receptor-β actions and may also contribute to suppression of postinfarction inflammation (5). Macrophages (Ma) acquire an anti-inflammatory phenotype, secreting TGF-β, interleukin (IL)-10, and proresolving lipid mediators, on ingestion of apoptotic neutrophils (aN) (6). Dendritic cells (DCs) are also activated after infarction and secrete anti-inflammatory cytokines (7). Cardiomyocytes (CM) in the border zone may contribute to suppression and spatial containment of the postinfarction inflammatory response by secreting mediators that promote an anti-inflammatory macrophage phenotype (such as regenerating islet-derived-3β [Reg-3β]; 8). Fibroblasts (F) also exhibit dynamic phenotypic alterations that mark the transition from the inflammatory to the proliferative phase (9). During the inflammatory phase, inflammatory cytokines (such as IL-1β and TNF-α) and activation of toll-like receptor (TLR)–dependent signaling by matrix fragments may activate a proinflammatory fibroblast phenotype. Stimulation of fibroblasts with IL-1β induces matrix metallproteinase expression and chemokine synthesis, while reducing α-smooth muscle actin levels. During the proliferative phase, activation of TGF-β–dependent cascades stimulates a matrix-preserving myofibroblast (MF) phenotype. [Powerpoint File]

Mending a Faltering Heart

Mending a Faltering Heart

Mo Li, Juan Carlos Izpisua Belmonte

Recent strategies for cardiomyocyte regeneration. Cardiomyocytes can be induced to re-enter the cell cycle through modulation of endogenous cardiomyocyte proliferation programs. Reprogramming to induced pluripotent stem cell (iPSCs) followed by directed differentiation could provide a large number of immature cardiomyocytes. Other noncardiomyocyte cells, such as fibroblasts, can be directly converted to induced cardiomyocytes (iCMs). These in vitro derived cardiomyocytes may be further matured using tissue engineering technologies. In situ conversion of cardiac fibroblasts also represents a promising strategy for heart repair. MI indicates myocardial infarction. [Powerpoint File]

Cardiac Nonmyocytes in the Hub of Cardiac Hypertrophy

Cardiac Nonmyocytes in the Hub of Cardiac Hypertrophy

Takehiro Kamo, Hiroshi Akazawa, Issei Komuro

Intercellular communications between cardiomyocytes and nonmyocytes in the development of cardiac hypertrophy. Myocardial cell responses are regulated by intercellular communications between cardiomyocytes and nonmyocytes, such as fibroblasts, endothelial cells, and inflammatory cells. Cardiomyocytes secrete angiogenic factors to induce angiogenesis. An increase in capillary mass leads to increase in supply of nutrients and O2 necessary for hypertrophic growth. In addition, endothelial cells produce a variety of paracrine factors that exert prohypertrophic and antihypertrophic responses. During the development of cardiac hypertrophy, localized proliferation of both epicardium-derived and endocardium-derived fibroblast lineages contributes to extracellular matrix protein deposition and cardiac fibrosis. A wide variety of paracrine and autocrine factors mediate the intercellular communications between cardiac fibroblasts and cardiomyocytes in cardiac hypertrophy. During the development of cardiac hypertrophy, macrophages accumulate in ventricle both through localized proliferation and recruitment of circulating monocytes. Cardiac macrophages and mast cells are involved in induction of cardiac hypertrophy, although mechanistic link between T cells and the development of cardiac hypertrophy remains unclear. [Powerpoint File]

Human Induced Pluripotent Stem Cell–Derived Cardiomyocytes: Insights Into Molecular, Cellular, and Functional Phenotypes

Human Induced Pluripotent Stem Cell–Derived Cardiomyocytes: Insights Into Molecular, Cellular, and Functional Phenotypes

Ioannis Karakikes, Mohamed Ameen, Vittavat Termglinchan, Joseph C. Wu

Expression of key structural and functional genes in induced pluripotent stem cell–derived cardiomyocytes (iPSC-CMs). A, Schematic of the major structural and functional features of iPSC-CMs. In adult CMs, on membrane depolarization a small amount of Ca2+ influx induced by activation of voltage-dependent L-type Ca2+ channels (CACNAC1) triggers the release of Ca2+ from the sarcoplasmic reticulum (SR) through the ryanodine receptors (ryanodine receptor 2 [RYR2]), termed Ca2+-induced Ca2+-release mechanism. The released Ca2+ ions diffuse through the cytosolic space and bind to troponin C (TNNC1), resulting in the release of inhibition induced by troponin I (TNNI3), which activates the sliding of thin and thick filaments, and lead to cardiac contraction. Recovery occurs as Ca2+ is extruded by the Na2+/Ca2+ exchanger (NCX1) and returned to the SR by the sarco(endo)plasmic Ca2+-ATPase pumps on the nonjunctional region of the SR that are regulated by phospholamban (PLN). This process is conserved in iPSC-CMs, but major differences exist, such as a nascent SR, the presence of an inositol 1,4,5-trisphosphate–releasable Ca2+ pool, and the complete absence of T-tubules. The genes encoding the major transmembrane ion channels involved in the generation of action potential are also shown. B, Immunofluorescence staining of cardiac troponin T and α-sarcomeric actinin in iPSC-CMs. C, Line-scan images and spontaneous Ca2+ transients in iPSC-CMs. ACTC1 indicates actin, α, cardiac muscle 1; CACNA1C, calcium channel, voltage-dependent, L type, α1C subunit; IPTR3, inositol 1,4,5-trisphosphate receptor, type 3; KCNH2, potassium voltage-gated channel, subfamily H (eag-related), member 2; KCNIP2, potassium channel–interacting protein 2; KCNJ2, potassium inwardly rectifying channel, subfamily J, member 2; KCNQ1, potassium voltage-gated channel, KQT-like subfamily, member 1; MYBPC3, myosin binding protein C; MYH6, myosin, heavy chain 6, α; MYH7, myosin, heavy chain 7, β; MYL2, myosin, light chain 2; MYL3, myosin, light chain 3; SCN5A, sodium channel, voltage-gated, type V, α-subunit; SERCA2, SR Ca2+-ATPase 2; TNNI3, troponin I type 3; TNNT2, troponin T type 2; TTN, titin; and TPM1, tropomyosin 1 (α). [Powerpoint File]

Human Induced Pluripotent Stem Cell–Derived Cardiomyocytes: Insights Into Molecular, Cellular, and Functional Phenotypes

Human Induced Pluripotent Stem Cell–Derived Cardiomyocytes: Insights Into Molecular, Cellular, and Functional Phenotypes

Ioannis Karakikes, Mohamed Ameen, Vittavat Termglinchan, Joseph C. Wu

Current applications of patient-specific induced pluripotent stem cell–derived cardiomyocyte (iPSC-CM) technology. iPSC-CMs have been used for disease modeling of inherited cardiomyopathies and channelopathies, regenerative therapies, drug discovery, and cardiotoxicity testing, as well as for studying metabolic abnormalities and cardiac development. [Powerpoint File]

Maintaining Ancient Organelles: Mitochondrial Biogenesis and Maturation

Maintaining Ancient Organelles: Mitochondrial Biogenesis and Maturation

Rick B. Vega, Julie L. Horton, Daniel P. Kelly

Peroxisome-proliferator activated receptor γ (PPARγ) coactivator-1α (PGC-1α) mediates physiological control of mitochondrial biogenesis and function. The transcriptional coactivator PGC-1α interacts directly with multiple transcription factors to integrate upstream signaling events with mitochondrial biogenesis and functional capacity. The downstream transcription factors control virtually every aspect of mitochondrial function and energy production, including biogenesis, dynamics, and maintenance of protein levels. The control of PGC-1α expression and activity is dynamic, responding to multiple intracellular second messengers and signaling molecules transmitting inputs from various physiological and metabolic stimuli (top). AMPK indicates AMP-activated protein kinase; CaMK, calmodulin-dependent kinase; CN, calcineurin; CREB, cAMP-response element binding protein; ERR, estrogen-related receptor; ETC/OXPHOS, electron transport chain/oxidative phosphorylation; NAD+, nicotinamide adenine dinucleotide; and NRF, nuclear respiratory factor. [Powerpoint FIle]

Maintaining Ancient Organelles: Mitochondrial Biogenesis and Maturation

Maintaining Ancient Organelles: Mitochondrial Biogenesis and Maturation

Rick B. Vega, Julie L. Horton, Daniel P. Kelly

Two predominant models of mtDNA replication are shown here. Both models concur the replisome consists of at least a helicase, T7 gp4-like protein with intramitochondrial nucleoid localization (TWINKLE; orange) and polymerase γ (POLG; yellow). Leading strand synthesis begins at OH and lagging strand synthesis at OL (red arrow). A, Strand-displacement model proposes single-stranded binding proteins (green spheres) bind the displaced H-strand during leading strand replication. B, Alternatively, the ribonucleotide incorporation throughout the lagging strand (RITOLS) model proposes portions of transcribed mitochondrial DNA bind the H-strand (green dotted line). [Powerpoint File]

Direct Cardiac Reprogramming: Progress and Challenges in Basic Biology and Clinical Applications

Direct Cardiac Reprogramming: Progress and Challenges in Basic Biology and Clinical Applications

Taketaro Sadahiro, Shinya Yamanaka, Masaki Ieda

Future cardiac regenerative therapy. The lost myocardial tissue is replaced by fibrous tissue that mainly consists of cardiac fibroblasts and extracellular matrix. The cell transplantation–based approach using induced pluripotent stem cell (iPSC)–derived cardiomyocytes is shown (upper). Direct cardiac reprogramming approach may convert endogenous cardiac fibroblasts directly into cardiomyocytes by defined factors in situ (lower). [Powerpoint File]