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Paquette SE, Oduor CI, Gaulke A, Stefan S, Bronk P, Dafonseca V, Barulin N, Lee C, Carley R, Morrison AR, Choi BR, Bailey JA, Plavicki JS. Loss of developmentally derived Irf8+ macrophages promotes hyperinnervation and arrhythmia in the adult zebrafish heart. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.17.589909. [PMID: 38659956 PMCID: PMC11042273 DOI: 10.1101/2024.04.17.589909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Recent developments in cardiac macrophage biology have broadened our understanding of the critical functions of macrophages in the heart. As a result, there is further interest in understanding the independent contributions of distinct subsets of macrophage to cardiac development and function. Here, we demonstrate that genetic loss of interferon regulatory factor 8 (Irf8)-positive embryonic-derived macrophages significantly disrupts cardiac conduction, chamber function, and innervation in adult zebrafish. At 4 months post-fertilization (mpf), homozygous irf8st96/st96 mutants have significantly shortened atrial action potential duration and significant differential expression of genes involved in cardiac contraction. Functional in vivo assessments via electro- and echocardiograms at 12 mpf reveal that irf8 mutants are arrhythmogenic and exhibit diastolic dysfunction and ventricular stiffening. To identify the molecular drivers of the functional disturbances in irf8 null zebrafish, we perform single cell RNA sequencing and immunohistochemistry, which reveal increased leukocyte infiltration, epicardial activation, mesenchymal gene expression, and fibrosis. Irf8 null hearts are also hyperinnervated and have aberrant axonal patterning, a phenotype not previously assessed in the context of cardiac macrophage loss. Gene ontology analysis supports a novel role for activated epicardial-derived cells (EPDCs) in promoting neurogenesis and neuronal remodeling in vivo. Together, these data uncover significant cardiac abnormalities following embryonic macrophage loss and expand our knowledge of critical macrophage functions in heart physiology and governing homeostatic heart health.
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Affiliation(s)
- Shannon E. Paquette
- Department of Pathology & Laboratory Medicine, Brown University, Providence, RI, 02912, USA
| | - Cliff I. Oduor
- Department of Pathology & Laboratory Medicine, Brown University, Providence, RI, 02912, USA
| | - Amy Gaulke
- Department of Pathology & Laboratory Medicine, Brown University, Providence, RI, 02912, USA
| | - Sabina Stefan
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA
| | - Peter Bronk
- Cardiovascular Research Center, Brown University Warren Alpert Medical School, Providence, RI, 02912, USA
| | - Vanny Dafonseca
- Department of Pathology & Laboratory Medicine, Brown University, Providence, RI, 02912, USA
| | - Nikolai Barulin
- Department of Pathology & Laboratory Medicine, Brown University, Providence, RI, 02912, USA
| | - Cadence Lee
- Vascular Research Laboratory, Providence VA Medical Center, Providence, RI, 02908, USA
- Ocean State Research Institute, Inc., Providence, RI, 02908, USA
| | - Rachel Carley
- Vascular Research Laboratory, Providence VA Medical Center, Providence, RI, 02908, USA
- Ocean State Research Institute, Inc., Providence, RI, 02908, USA
| | - Alan R. Morrison
- Vascular Research Laboratory, Providence VA Medical Center, Providence, RI, 02908, USA
- Ocean State Research Institute, Inc., Providence, RI, 02908, USA
- Department of Internal Medicine, Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Bum-Rak Choi
- Cardiovascular Research Center, Brown University Warren Alpert Medical School, Providence, RI, 02912, USA
| | - Jeffrey A. Bailey
- Department of Pathology & Laboratory Medicine, Brown University, Providence, RI, 02912, USA
| | - Jessica S. Plavicki
- Department of Pathology & Laboratory Medicine, Brown University, Providence, RI, 02912, USA
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Chen HS, van Roon L, Ge Y, van Gils JM, Schoones JW, DeRuiter MC, Zeppenfeld K, Jongbloed MRM. The relevance of the superior cervical ganglion for cardiac autonomic innervation in health and disease: a systematic review. Clin Auton Res 2024; 34:45-77. [PMID: 38393672 PMCID: PMC10944423 DOI: 10.1007/s10286-024-01019-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 01/22/2024] [Indexed: 02/25/2024]
Abstract
PURPOSE The heart receives cervical and thoracic sympathetic contributions. Although the stellate ganglion is considered the main contributor to cardiac sympathetic innervation, the superior cervical ganglia (SCG) is used in many experimental studies. The clinical relevance of the SCG to cardiac innervation is controversial. We investigated current morphological and functional evidence as well as controversies on the contribution of the SCG to cardiac innervation. METHODS A systematic literature review was conducted in PubMed, Embase, Web of Science, and COCHRANE Library. Included studies received a full/text review and quality appraisal. RESULTS Seventy-six eligible studies performed between 1976 and 2023 were identified. In all species studied, morphological evidence of direct or indirect SCG contribution to cardiac innervation was found, but its contribution was limited. Morphologically, SCG sidedness may be relevant. There is indirect functional evidence that the SCG contributes to cardiac innervation as shown by its involvement in sympathetic overdrive reactions in cardiac disease states. A direct functional contribution was not found. Functional data on SCG sidedness was largely unavailable. Information about sex differences and pre- and postnatal differences was lacking. CONCLUSION Current literature mainly supports an indirect involvement of the SCG in cardiac innervation, via other structures and plexuses or via sympathetic overdrive in response to cardiac diseases. Morphological evidence of a direct involvement was found, but its contribution seems limited. The relevance of SCG sidedness, sex, and developmental stage in health and disease remains unclear and warrants further exploration.
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Affiliation(s)
- H Sophia Chen
- Department of Cardiology, Willem Einthoven Center for Cardiac Arrhythmia Research and Management, Leiden University Medical Center, Leiden, The Netherlands
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Lieke van Roon
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Yang Ge
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Janine M van Gils
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jan W Schoones
- Directorate of Research Policy, Leiden University Medical Center, Leiden, The Netherlands
| | - Marco C DeRuiter
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Katja Zeppenfeld
- Department of Cardiology, Willem Einthoven Center for Cardiac Arrhythmia Research and Management, Leiden University Medical Center, Leiden, The Netherlands
- Department of Cardiology, Center of Congenital Heart Disease Amsterdam Leiden (CAHAL), Leiden University Medical Center, Leiden, The Netherlands
| | - Monique R M Jongbloed
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands.
- Department of Cardiology, Center of Congenital Heart Disease Amsterdam Leiden (CAHAL), Leiden University Medical Center, Leiden, The Netherlands.
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Chen HS, van Roon L, Schoones J, Zeppenfeld K, DeRuiter MC, Jongbloed MRM. Cardiac sympathetic hyperinnervation after myocardial infarction: a systematic review and qualitative analysis. Ann Med 2023; 55:2283195. [PMID: 38065671 PMCID: PMC10836288 DOI: 10.1080/07853890.2023.2283195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Accepted: 11/08/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Cardiac sympathetic hyperinnervation after myocardial infarction (MI) is associated with arrhythmogenesis and sudden cardiac death. The characteristics of cardiac sympathetic hyperinnervation remain underexposed. OBJECTIVE To provide a systematic review on cardiac sympathetic hyperinnervation after MI, taking into account: (1) definition, experimental model and quantification method and (2) location, amount and timing, in order to obtain an overview of current knowledge and to expose gaps in literature. METHODS References on cardiac sympathetic hyperinnervation were screened for inclusion. The included studies received a full-text review and quality appraisal. Relevant data on hyperinnervation were collected and qualitatively analysed. RESULTS Our literature search identified 60 eligible studies performed between 2000 and 2022. Cardiac hyperinnervation is generally defined as an increased sympathetic nerve density or increased number of nerves compared to another control group (100%). Studies were performed in a multitude of experimental models, but most commonly in male rats with permanent left anterior descending (LAD) artery ligation (male: 63%, rat: 68%, permanent ligation: 93%, LAD: 97%). Hyperinnervation seems to occur mainly in the borderzone. Quantification after MI was performed in regions of interest in µm2/mm2 (41%) or in percentage of nerve fibres (46%) and the reported amount showed a great variation ranging from 439 to 126,718 µm2/mm2. Hyperinnervation seems to start from three days onwards to >3 months without an evident peak, although studies on structural evaluation over time and in the chronic phase were scarce. CONCLUSIONS Cardiac sympathetic hyperinnervation after MI occurs mainly in the borderzone from three days onwards and remains present at later timepoints, for at least 3 months. It is most commonly studied in male rats with permanent LAD ligation. The amount of hyperinnervation differs greatly between studies, possibly due to differential quantification methods. Further studies are required that evaluate cardiac sympathetic hyperinnervation over time and in the chronic phase, in transmural sections, in the female sex, and in MI with reperfusion.
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Affiliation(s)
- H. Sophia Chen
- Department of Cardiology, Center of Congenital Heart Disease Amsterdam Leiden (CAHAL), Leiden University Medical Center, Leiden, The Netherlands
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Lieke van Roon
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jan Schoones
- Dictorate of Research Policy, Leiden University Medical Center, Leiden, The Netherlands
| | - Katja Zeppenfeld
- Department of Cardiology, Center of Congenital Heart Disease Amsterdam Leiden (CAHAL), Leiden University Medical Center, Leiden, The Netherlands
| | - Marco C. DeRuiter
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Monique R. M. Jongbloed
- Department of Cardiology, Center of Congenital Heart Disease Amsterdam Leiden (CAHAL), Leiden University Medical Center, Leiden, The Netherlands
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
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Ge Y, van Roon L, van Gils JM, Geestman T, van Munsteren CJ, Smits AM, Goumans MJTH, DeRuiter MC, Jongbloed MRM. Acute myocardial infarction induces remodeling of the murine superior cervical ganglia and the carotid body. Front Cardiovasc Med 2022; 9:758265. [PMID: 36277772 PMCID: PMC9582601 DOI: 10.3389/fcvm.2022.758265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/12/2022] [Indexed: 11/13/2022] Open
Abstract
A role for cardiac sympathetic hyperinnervation in arrhythmogenesis after myocardial infarction (MI) has increasingly been recognized. In humans and mice, the heart receives cervical as well as thoracic sympathetic contributions. In mice, superior cervical ganglia (SCG) have been shown to contribute significantly to myocardial sympathetic innervation of the left ventricular anterior wall. Of interest, the SCG is situated adjacent to the carotid body (CB), a small organ involved in oxygen and metabolic sensing. We investigated the remodeling of murine SCG and CB over time after MI. Murine SCG were isolated from control mice, as well as 24 h, 3 days, 7 days and 6 weeks after MI. SCG and CBs were stained for the autonomic nervous system markers β3-tubulin, tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT), as well as for the neurotrophic factors brain derived neurotropic factor (BDNF), nerve growth factor (NGF) and their tyrosine receptor kinase (pan TRK). Results show that after MI a significant increase in neuron size occurs, especially in the region bordering the CB. Co-expression of TH and ChAT is observed in SCG neuronal cells, but not in the CB. After MI, a significant decrease in ChAT intensity occurs, which negatively correlated with the increased cell size. In addition, an increase of BDNF and NGF at protein and mRNA levels was observed in both the CB and SCG. This upregulation of neurotropic factors coincides with the upregulation of their receptor within the SCG. These findings were concomitant with an increase in GAP43 expression in the SCG, which is known to contribute to axonal outgrowth and elongation. In conclusion, neuronal remodeling toward an increased adrenergic phenotype occurs in the SCG, which is possibly mediated by the CB and might contribute to pathological hyperinnervation after MI.
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Affiliation(s)
- Yang Ge
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands,Department of Cardiology, Leiden University Medical Center, Leiden, Netherlands
| | - Lieke van Roon
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands,Department of Cardiology, Leiden University Medical Center, Leiden, Netherlands
| | - Janine M. van Gils
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands,Department of Nephrology, Leiden University Medical Center, Leiden, Netherlands
| | - Tom Geestman
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Conny J. van Munsteren
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Anke M. Smits
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | | | - Marco C. DeRuiter
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Monique R. M. Jongbloed
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands,Department of Cardiology, Leiden University Medical Center, Leiden, Netherlands,*Correspondence: Monique R. M. Jongbloed, ; orcid.org/0000-0002-9132-0418
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Streef TJ, Smits AM. Epicardial Contribution to the Developing and Injured Heart: Exploring the Cellular Composition of the Epicardium. Front Cardiovasc Med 2021; 8:750243. [PMID: 34631842 PMCID: PMC8494983 DOI: 10.3389/fcvm.2021.750243] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 08/30/2021] [Indexed: 12/15/2022] Open
Abstract
The epicardium is an essential cell population during cardiac development. It contributes different cell types to the developing heart through epithelial-to-mesenchymal transition (EMT) and it secretes paracrine factors that support cardiac tissue formation. In the adult heart the epicardium is a quiescent layer of cells which can be reactivated upon ischemic injury, initiating an embryonic-like response in the epicardium that contributes to post-injury repair processes. Therefore, the epicardial layer is considered an interesting target population to stimulate endogenous repair mechanisms. To date it is still not clear whether there are distinct cell populations in the epicardium that contribute to specific lineages or aid in cardiac repair, or that the epicardium functions as a whole. To address this putative heterogeneity, novel techniques such as single cell RNA sequencing (scRNA seq) are being applied. In this review, we summarize the role of the epicardium during development and after injury and provide an overview of the most recent insights into the cellular composition and diversity of the epicardium.
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Affiliation(s)
| | - Anke M. Smits
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
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Ge Y, Smits AM, Liu J, Zhang J, van Brakel TJ, Goumans MJTH, Jongbloed MRM, de Vries AAF. Generation, Characterization, and Application of Inducible Proliferative Adult Human Epicardium-Derived Cells. Cells 2021; 10:2064. [PMID: 34440833 PMCID: PMC8391799 DOI: 10.3390/cells10082064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 08/02/2021] [Accepted: 08/04/2021] [Indexed: 12/20/2022] Open
Abstract
RATIONALE In recent decades, the great potential of human epicardium-derived cells (EPDCs) as an endogenous cell source for cardiac regeneration has been recognized. The limited availability and low proliferation capacity of primary human EPDCs and phenotypic differences between EPDCs obtained from different individuals hampers their reproducible use for experimental studies. AIM To generate and characterize inducible proliferative adult human EPDCs for use in fundamental and applied research. METHODS AND RESULTS Inducible proliferation of human EPDCs was achieved by doxycycline-controlled expression of simian virus 40 large T antigen (LT) with a repressor-based lentiviral Tet-On system. In the presence of doxycycline, these inducible EPDCs (iEPDCs) displayed high and long-term proliferation capacity. After doxycycline removal, LT expression ceased and the iEPDCs regained their cuboidal epithelial morphology. Similar to primary EPDCs, iEPDCs underwent an epithelial-to-mesenchymal transition (EMT) after stimulation with transforming growth factor β3. This was confirmed by reverse transcription-quantitative polymerase chain reaction analysis of epithelial and mesenchymal marker gene expression and (immuno) cytochemical staining. Collagen gel-based cell invasion assays demonstrated that mesenchymal iEPDCs, like primary EPDCs, possess increased invasion and migration capacities as compared to their epithelial counterparts. Mesenchymal iEPDCs co-cultured with sympathetic ganglia stimulated neurite outgrowth similarly to primary EPDCs. CONCLUSION Using an inducible LT expression system, inducible proliferative adult human EPDCs were generated displaying high proliferative capacity in the presence of doxycycline. These iEPDCs maintain essential epicardial characteristics with respect to morphology, EMT ability, and paracrine signaling following doxycycline removal. This renders iEPDCs a highly useful new in vitro model for studying human epicardial properties.
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Affiliation(s)
- Yang Ge
- Department of Anatomy & Embryology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands; (Y.G.); (M.R.M.J.)
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; (J.L.); (J.Z.); (A.A.F.d.V.)
| | - Anke M. Smits
- Department of Cell and Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands;
| | - Jia Liu
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; (J.L.); (J.Z.); (A.A.F.d.V.)
- Central Laboratory, Longgang District People’s Hospital of Shenzhen & The Third Affiliated Hospital of The Chinese University of Hong Kong, Shenzhen 518172, China
| | - Juan Zhang
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; (J.L.); (J.Z.); (A.A.F.d.V.)
| | - Thomas J. van Brakel
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Albinusdreef 2, 2333 ZC Leiden, The Netherlands;
| | - Marie José T. H. Goumans
- Department of Cell and Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands;
| | - Monique R. M. Jongbloed
- Department of Anatomy & Embryology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, The Netherlands; (Y.G.); (M.R.M.J.)
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; (J.L.); (J.Z.); (A.A.F.d.V.)
| | - Antoine A. F. de Vries
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; (J.L.); (J.Z.); (A.A.F.d.V.)
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Koracevic G, Micic S, Stojanovic M. By discontinuing beta-blockers before an exercise test we may precipitate a rebound phenomenon. Curr Vasc Pharmacol 2021; 19:624-633. [PMID: 33653252 DOI: 10.2174/1570161119666210302152322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 01/25/2021] [Accepted: 01/30/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND There is a need to analyse the current approach to beta-blocker (BB) use in relation to exercise-based stress tests. OBJECTIVE We compared various guidelines regarding recommending abrupt vs gradual discontinuation of BB prior to exercise tests. We also analyse the shortcomings of the currently recommended approach and suggest a new approach to avoid BB rebound. METHODS A narrative review is used to analyse this topic due to lack of valid randomized clinical trials. RESULTS Omitting the BB therapy prior to exercise-based test has been recommended in guidelines for many years. Although reasonable, this approach has potential disadvantages since sudden BB withdrawal may induce a rebound phenomenon, which is, also, acknowledged in several guidelines. CONCLUSIONS We observed inconsistency among relevant guidelines; there is no homogenous approach regarding BB use before exercise tests. Most guidelines recommend BB withdrawal for a couple of days before the test; they do not advise BB dose tapering. This approach is not standardised and raises the risk of BB rebound phenomenon both before and during the test. Therefore, we suggest using the half the prescribed BB dose at the usual time of administration (in the morning, prior to the exercise test).
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Affiliation(s)
- Goran Koracevic
- Department for Cardiovascular Diseases, Clinical Center Nis. Serbia
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Liao Z, Chen Y, Duan C, Zhu K, Huang R, Zhao H, Hintze M, Pu Q, Yuan Z, Lv L, Chen H, Lai B, Feng S, Qi X, Cai D. Cardiac telocytes inhibit cardiac microvascular endothelial cell apoptosis through exosomal miRNA-21-5p-targeted cdip1 silencing to improve angiogenesis following myocardial infarction. Am J Cancer Res 2021; 11:268-291. [PMID: 33391474 PMCID: PMC7681094 DOI: 10.7150/thno.47021] [Citation(s) in RCA: 80] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 09/22/2020] [Indexed: 12/15/2022] Open
Abstract
Promotion of cardiac angiogenesis in ischemic myocardium is a critical strategy for repairing and regenerating the myocardium after myocardial infarction (MI). Currently, effective methods to aid in the survival of endothelial cells, to avoid apoptosis in ischemic myocardium and to achieve long-term cardiac angiogenesis are still being pursued. Here, we investigated whether cardiac telocyte (CT)-endothelial cell communication suppresses apoptosis and promotes the survival of endothelial cells to facilitate cardiac angiogenesis during MI. Methods: CT exosomes were isolated from CT conditioned medium, and their miRNA profile was characterized by small RNA sequencing. A rat model of left anterior descending coronary artery ligation (LAD)-mediated MI was assessed with histology for infarct size and fibrosis, immunostaining for angiogenesis and cell apoptosis and echocardiography to evaluate the therapeutic effects. Cardiac microvascular endothelial cells (CMECs) and the LAD-MI model treated with CT exosomes or CT exosomal miRNA-21-5p in vitro and in vivo were assessed with cellular and molecular techniques to demonstrate the underlying mechanism. Results: CTs exert therapeutic effects on MI via the potent paracrine effects of CT exosomes to facilitate the inhibition of apoptosis and survival of CMECs and promote cardiac angiogenesis. A novel mechanism of CTs is revealed, in which CT-endothelial cell communication suppresses apoptosis and promotes the survival of endothelial cells in the pathophysiological myocardium. CT exosomal miRNA-21-5p targeted and silenced the cell death inducing p53 target 1 (Cdip1) gene and thus down-regulated the activated caspase-3, which then inhibited the apoptosis of recipient endothelial cells under ischemic and hypoxic conditions, facilitating angiogenesis and regeneration following MI. Conclusions: The present study is the first to show that CTs inhibit cardiac microvascular endothelial cell apoptosis through exosomal miRNA-21-5p-targeted Cdip1 silencing to improve angiogenesis in myocardial infarction. It is believed that these novel findings and the discovery of cellular and molecular mechanisms will provide new opportunities to tailor novel cardiac cell therapies and cell-free therapies for the functional and structural regeneration of the injured myocardium.
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