Posts Tagged: stem cells

Elixir of Life: Thwarting Aging With Regenerative Reprogramming

Elixir of Life: Thwarting Aging With Regenerative Reprogramming

Ergin Beyret, Paloma Martinez Redondo, Aida Platero Luengo, Juan Carlos Izpisua Belmonte

Regenerative reprogramming approaches. In vivo induction of transdifferentiation can be used to repopulate the cells lost during aging as an alternative to transplantation, complementing the intrinsic regenerative capacity. For instance, neurons lost to neurodegenerative diseases can be replaced by transdifferentiating resident glia or astrocytes; cardiac fibroblasts can be the cell source for induced cardiomyocytes; α, ductal, and acinar cells can be used for β cells. Alternatively, transient 4F (OCT4, KLF4, SOX2, and c-Myc) expression can be used to rejuvenate cells. This in turn can decelerate degeneration of biological units that have low regeneration capacity (eg, aorta) or augment regeneration capacity by counteracting stem cell exhaustion (eg, muscle) or by enhancing the plasticity of organs that intrinsically undergo cell conversions during regeneration (eg, transdifferentiation in the pancreas and dedifferentiation in the kidney). MuSC indicates muscle stem cell. [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

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]

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]

From Microscale Devices to 3D Printing: Advances in Fabrication of 3D Cardiovascular Tissues

From Microscale Devices to 3D Printing: Advances in Fabrication of 3D Cardiovascular Tissues

Anton V. Borovjagin, Brenda M. Ogle, Joel L. Berry, Jianyi Zhang

Bioprinting is usually accomplished using a combination of gel and cells. Laser-assisted bioprinting (A) using Laser-induced forward transfer relies on the focused energy of a laser onto an energy absorbing ribbon to induce bioink droplet formation. This technique is advantageous because it avoids the problem of clogging of the bioink nozzle that plagues other bioprinting techniques. Multiphoton excitation-based printing (B) is accomplished via photocrosslinking of proteins or polymers in the focal volume of the laser and excels in its high resolution and ability to polymerize many native proteins that do not form hydrogels spontaneously outside the body. Inkjet printing (C), one of the most common printing techniques, relies on a vapor bubble or a piezoelectric actuator to displace material to extrude the bioink from a nozzle. Robotic dispensing (D) uses other mechanical means of displacing bioink under robotic control. ECM indicates extracellular matrix. [Powerpoint File]

From Microscale Devices to 3D Printing: Advances in Fabrication of 3D Cardiovascular Tissues

From Microscale Devices to 3D Printing: Advances in Fabrication of 3D Cardiovascular Tissues

Anton V. Borovjagin, Brenda M. Ogle, Joel L. Berry, Jianyi Zhang

In vitro testing of cells and tissues may occur in several ways. Microfluidic systems (A) have emerged as a tool for basic science studies of the effect of highly controlled fluid mechanical and solid mechanical forces on single cell types or cocultures. Microfluidic systems are also gaining favor as a diagnostic tool and a platform for drug development. Organoid cultures (B) are described as organ buds grown in culture that feature realistic microanatomy and are useful as cellular models of human disease. These cultures have found utility in the study of basic mechanisms of organ-specific diseases. Spheroid cultures (C) feature sphere-shaped clusters of a single cell type or coculture sustained in a gel or a bioreactor in order to interact with their 3D surroundings and are useful in testing drug efficacy and toxicity. (D) Engineered heart tissues are constructed by polymerizing an extracellular matrix–based gel containing cardiac cell types between 2 elastomeric posts or similar structures allowing auxotonic contraction of cardiomyocytes. This allows approximation of the normal conditions of the heart contracting against the hydrostatic pressure imposed by the circulation. This type of tissue construct has been used for testing toxicity of drugs and basic studies of muscle function and interplay between multiple cardiac cell types. [Powerpoint File]

Emerging Concepts in Paracrine Mechanisms in Regenerative Cardiovascular Medicine and Biology

Emerging Concepts in Paracrine Mechanisms in Regenerative Cardiovascular Medicine and Biology

Conrad P. Hodgkinson, Akshay Bareja, José A. Gomez, Victor J. Dzau

Paracrine factors affect different temporal events after myocardial injury influencing different stages of the reparative and regenerative processes. [Powerpoint File]

Mechanical Forces Reshape Differentiation Cues That Guide Cardiomyogenesis

Mechanical Forces Reshape Differentiation Cues That Guide Cardiomyogenesis

Cassandra L. Happe, Adam J. Engler

Interplay of chemical and mechanical signals that underlie cardiac specification and development. Schematic representation of integrin-mediated signaling specifically detailing how chemical signals (left), for example, integrin ligation, drive focal adhesion formation, and downstream events leading to transcriptional changes. Mechanical signals (right) are mediated by actomyosin contractions. Both influence transcriptional changes via common mechanisms diagrammed at the bottom of the illustration, including chromatin remodeling and changes in nuclear pore complex diffusion among others. Dash and solid lines indicate the direction of biophysical and biochemical interactions, respectively. AKT indicates protein kinase B; ECM, extracellular matrix; FAK, focal adhesion kinase; GSK, glycogen synthase kinase; ILK, integrin-linked kinase; and PI3K, phosphoinositide 3-kinase. [Powerpoint File]

More Than Tiny Sacks: Stem Cell Exosomes as Cell-Free Modality for Cardiac Repair

More Than Tiny Sacks: Stem Cell Exosomes as Cell-Free Modality for Cardiac Repair

Raj Kishore, Mohsin Khan

Stem cell–derived exosomes for cardiac repair. Exosome derived from different types of stem cells, including embryonic stem cells (ESC), induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), cardiac stem cells (CSCs), and endothelial progenitor cells (EPCs) carry and deliver messanger RNAs (mRNAs), microRNAs (miRNAs), and proteins to the damaged heart tissue consequently augmenting resident cardiac stem cell activation/expansion, cardiomyocyte proliferation, neovascularization, and modulation of cardiac inflammatory response (Illustration credit: Ben Smith). [Powerpoint File]

Emerging Concepts in Paracrine Mechanisms in Regenerative Cardiovascular Medicine and Biology

Emerging Concepts in Paracrine Mechanisms in Regenerative Cardiovascular Medicine and Biology

Conrad P. Hodgkinson, Akshay Bareja, José A. Gomez, Victor J. Dzau

Paracrine factors affect different cell types and create a microenvironment that is influenced by concentration gradients, with temporal and spatial summation of cellular responses. Reprinted from Hodgkinson et al149 with permission of the publisher. Copyright ©2015, Elsevier. [Powerpoint File]

Emerging Concepts in Paracrine Mechanisms in Regenerative Cardiovascular Medicine and Biology

Emerging Concepts in Paracrine Mechanisms in Regenerative Cardiovascular Medicine and Biology

Conrad P. Hodgkinson, Akshay Bareja, José A. Gomez, Victor J. Dzau

Paracrine factors are pleiotropic. For illustration, we show the cellular effects of 2 selective paracrine factors on the cardiomyocyte. Left, Hypoxic-induced Akt regulated stem cell factor (HASF) and secreted frizzled related protein 2 (Sfrp2) inhibit cardiomyocyte apoptosis through divergent pathways. HASF, after binding to a growth factor receptor, inhibits cytochrome release from mitochondria via protein kinase C-ε (PKCε). In contrast, Sfrp2 inhibits Wnt activation of frizzled receptors. This induces β-catenin degradation via the anaphase promoting complex (APC) complex. Right, Abi3bp and Sfrp2 promote cardiac progenitor cell differentiation and inhibiting proliferation. Abi3bp activates integrin-β1. Src and extracellular signal regulated kinase (ERK) activation work together to inhibit proliferation. PKCζ and Akt activation switch on cardiac genes. Sfrp2 sequesters Wnt, preventing the activation of frizzled receptors. This promotes c-Jun N-terminal kinase (JNK) activation and cardiac gene expression. Inhibition of β-catenin blocks the proliferation pathway in these cells. ECM indicates extracellular matrix; FRZ, frizzled; and TF, transcription factor. [Powerpoint File]

Modulating the Vascular Response to Limb Ischemia: Angiogenic and Cell Therapies

Modulating the Vascular Response to Limb Ischemia: Angiogenic and Cell Therapies

John P. Cooke, Douglas W. Losordo

Angiogenesis is triggered by reduced oxygen delivery to the tissue, which induces the elaboration by ischemic cells of angiogenic factors such as vascular endothelial growth factor (VEGF). Angiogenesis is characterized by capillary sprouting, endothelial cell migration, proliferation, and luminogenesis to generate new capillaries. Adult vasculogenesis is mediated by the action of circulating cells such as endothelial progenitor cells (EPCs). EPCs are a heterogenous population of cells, largely of hematopoietic lineage, and are characterized by cell-surface antigen markers including CD34, CD133, and VEGF receptor 2 (VEGFR-2). These circulating cells contribute to the expansion of the microvasculature via multiple mechanisms, secretion of paracrine factors playing a prominent role. A small subset of these cells seem to incorporate into the vasculature (inosculation). Arteriogenesis is a positive remodeling of pre-existing collateral channels in the limb. There is little to no flow through these narrow, high resistance channels in healthy individuals. However, when major conduits become severely narrowed or occluded, more flow becomes directed through the collateral channels. Under the influence of vascular shear stress, the diameter of these channels increase. This positive remodeling seems to be because of endothelial factors, as well as infiltrating macrophages. The remodeling process is characterized by dynamic restructuring of the extracellular matrix with degradation and synthesis; vascular smooth muscle cell apoptosis as well as proliferation, which lead to an increased diameter and thickness of the vessel. [Powerpoint File]

Use of Mesenchymal Stem Cells for Therapy of Cardiac Disease

Use of Mesenchymal Stem Cells for Therapy of Cardiac Disease

Vasileios Karantalis, Joshua M. Hare

Immunomodulatory capabilities of mesenchymal stem cells (MSCs). Schematic overview of the interactions between MSC and the immune system. Via multiple pathways, MSCs suppress proliferation of both T helper (TH) and cytotoxic T cells (Tc). In addition, differentiation to TH2 and regulatory T-cells (Treg) is triggered, resulting in an anti-inflammatory environment. Maturation of dendritic cells (DC) is inhibited via interleukin (IL)-6, blocking upregulation of CD40, CD80, and CD86, which in turn reduce T-cell activation. Monocytes are induced by MSC to differentiate preferentially toward the M2 phenotype. IL-10 produced by the M2 macrophages can boost the formation of Treg, whereas simultaneously reducing tissue migration of neutrophils. Neutrophils (polymorphonuclear granulocytes; PMN) are allowed longer life span but reactive oxygen species production is decreased. Natural Killer (NK) cell proliferation is suppressed as well as their cytotoxic activity. B-cell proliferation is inhibited and the production of antibodies is reduced. Modified from van den Akker et al.46 HGF indicates hepatocyte growth factor; IDO, indoleamine-pyrrole-2-3-dioxygenase; PGE2, prostaglandin E2; and TGF-β, transforming growth factor-β. [Powerpoint FIle]