Summary

マウスの左前下冠動脈の動脈の常設ライゲーション:心筋梗塞後のリモデリングおよび心不全のモデル

Published: December 02, 2014
doi:

Summary

Heart failure is the leading cause of hospitalization and a major cause of mortality. A model of permanent ligation of the left anterior descending coronary artery in mice is applied to investigate ventricular remodelling and cardiac dysfunction post-myocardial infarction. The technique of invasive hemodynamic measurements in mice is presented.

Abstract

心不全は、心臓が、安静時またはストレス中の細胞酸素要求に見合った速度で血液を送り出すために失敗する症候群である。これは、労作時、特に、体液貯留、息切れ、疲労によって特徴付けられる。心不全は、成長している公衆衛生問題、入院の主要な原因であり、死亡率の主要な原因である。虚血性心疾患は、心不全の主な原因である。

心室リモデリングは、左心室の構造、大きさ、形状の変化を指す。左心室のこのアーキテクチャのリモデリング( 例えば、全身性動脈高血圧症または大動脈弁狭窄症)、または容量過負荷による圧負荷により、傷害( 例えば、心筋梗塞)によって誘導される。心室リモデリングは、壁応力に影響を与えるので、それは心機能及び心不全の発症に重大な影響を与える。左前descendinの永久結紮のモデルマウスにおけるグラム冠動脈心室リモデリングおよび心臓機能心筋梗塞後を調査するために使用される。このモデルは、左冠動脈前下行枝の過渡結紮のモデルに比べて目標や病態生理学的関連性の点で基本的に異なる。虚血/再灌流傷害のこの後者のモデルにおいて、梗塞の初期の程度は、再灌流後の心筋救済に影響を与える要因によって調節され得る。対照的に、左冠動脈前下行枝の永久結紮後24時間での梗塞領域は固定されている。このモデルにおける心機能は、1)梗塞拡大、梗塞の治癒、および瘢痕形成のプロセスによって影響される。 2)左心室拡張、心肥大、及び心室リモデリングの同時開発。

左冠動脈前下行枝の永久結紮モデル、侵襲的血行動態MEAの技術に加えてマウスにおけるsurements詳細に示されている。

Introduction

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with the cellular oxygen requirements at rest or during stress. It is characterized by fluid retention, shortness of breath, and fatigue, in particular on exertion. Heart failure is a growing public health problem, the leading cause of hospitalization, and a major cause of mortality. Ischemic heart disease is the main cause of heart failure1.

Ventricular remodelling refers to changes in structure, size, and shape of the left ventricle. In other words, ventricular remodelling concerns an alteration of the left ventricular architecture. This architectural remodelling of the left ventricle is induced by injury (e.g., myocardial infarction), by pressure overload (e.g., systemic arterial hypertension or aortic stenosis), or by volume overload (e.g., mitral insufficiency). Since ventricular remodelling affects wall stress, it has a profound impact on cardiac function and on the development of heart failure.

Loss of myocardial tissue following acute myocardial infarction results in a decreased systolic ejection and an increased left ventricular end-diastolic volume and pressure. The Frank-Starling mechanism, implying that an increased end-diastolic volume results in an increased pressure developed during systole, may help to restore cardiac output. However, the concomitant increased wall stress may induce regional hypertrophy in the non-infarcted segment, whereas in the infarcted area expansion and thinning may occur. Experimental animal studies show that the infarcted ventricle hypertrophies and that the degree of hypertrophy is dependent on the infarct size2.

The loss of myocardial tissue following acute myocardial infarction results in a sudden increase in loading conditions. Post-infarct remodelling occurs in the setting of volume overload, since the stretched and dilated infarcted tissue increases the left ventricular volume. An increased ventricular volume not only implies increased preload (passive ventricular wall stress at the end of diastole) but also increased afterload (total myocardial wall stress during systolic ejection). Afterload is increased since the systolic radius is increased. Therefore, ventricular remodelling post-myocardial infarction is characterized by mixed features of volume overload and pressure overload.

The myocardium consists of 3 integrated components: cardiomyocytes, extracellular matrix, and the capillary microcirculation. All 3 components are involved in the remodelling process. Matrix metalloproteinases produced by inflammatory cells induce degradation of intermyocyte collagen struts and cardiomyocyte slippage. This leads to infarct expansion characterized by the disproportionate thinning and dilatation of the infarct segment3. In later stages of remodelling, interstitial fibrosis is induced, which negatively affects the diastolic properties of the heart.

The vascular and cardiomyocyte compartment in the myocardium should remain balanced in the process of ventricular remodelling to avoid tissue hypoxia4,5. Whether hypertrophy progresses to heart failure or not may be critically dependent on this balance between the vascular and cardiomyocyte compartment in the myocardium.

A model of permanent ligation of the left anterior descending coronary artery in mice is used to investigate ventricular remodelling and cardiac function post-myocardial infarction. This model is fundamentally different in terms of objectives and pathophysiological relevance compared to the model of transient ligation of the left anterior descending coronary artery. In this latter model of ischemia/reperfusion injury, the initial extent of the infarct may be modulated by factors that affect myocardial salvage following reperfusion6. In contrast, the infarct area at 24 hours after permanent ligation of the left anterior descending coronary artery is fixed. Cardiac function in this model will be affected by 1) the process of infarct expansion, infarct healing, and scar formation; and 2) the concomitant development of left ventricular dilatation, cardiac hypertrophy, and ventricular remodelling.

Protocol

注:この項で説明するすべての実験手順は、動物実験ルーヴェン·カトリック大学の研究諮問委員会によって承認された(プロジェクト:2013分の154-B·デ·沖積層)。 左前下冠動脈の動脈の1常設ライゲーション / kgのペントバルビタールナトリウム70mgの40〜10mg / kgの腹腔内投与によりマウスを麻酔。それはもはやしっかりとつま先のピンチを反応するときに、マウ?…

Representative Results

心筋梗塞の程度は、エバンスブルー/塩化2,3,5-トリフェニルテトラゾリウム(TTC)の二重染色によって評価することができる。 TTCは、NADH 8の存在下で様々なデヒドロゲナーゼの活性による生体組織の深い赤1,3,5- triphenylformazanに変換され、酸化還元指示薬、ある。 図1は、24時間後に心臓の代表的な断面を示している左冠動脈前下行枝の結紮。ブルー染色領域が非虚血/正常?…

Discussion

慢性心筋の構造および機能の変化、左心室機能不全の発症、および心不全への進行は、いくつかのマウスモデル12で調査することができる。心臓リモデリングおよび機能不全は、心筋障害、または圧力大動脈狭窄を横断する第二過負荷、または拡張型心筋12の遺伝モデルで研究することができることによって誘導することができる。明らかに、マウスモデルの最も顕著な利点?…

Disclosures

The authors have nothing to disclose.

Acknowledgements

This work was supported by Onderzoekstoelagen grant OT/13/090 of the KU Leuven and by grant G0A3114N of the FWO-Vlaanderen.

Materials

Reagents
Buprenorphine (Buprenex®) Bedford Laboratories
Sodium Pentobarbital (Nembutal®) Ceva
Betadine® VWR internationals 200065-400
5 – 0 silk suture Ethicon, Johnson & Johnson Medical K890H
6 – 0 prolene suture  Ethicon, Johnson & Johnson Medical F1832
6 – 0 Ti- Cron suture Ethicon, Johnson & Johnson Medical F1823
Urethane  Sigma 94300
Alconox Alconox Inc.
Equipment
Ventilator, MiniVent Model 845 Hugo Sachs 73-0043
Chest retractor or Thorax retractor Kent Scientific corporation INS600240 ALM Self-retaining, serrated, 7cm long, 4 x 4 "L" shaped prongs, 3mm x 3mm
1.0 French Millar pressure catheter  Millar Instruments  SPR – 1000/NR
Powerlab ADInstruments Pty Ltd.
LabChart® software ADInstruments Pty Ltd.
Rectal probe ADInstruments Pty Ltd.

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Cite This Article
Muthuramu, I., Lox, M., Jacobs, F., De Geest, B. Permanent Ligation of the Left Anterior Descending Coronary Artery in Mice: A Model of Post-myocardial Infarction Remodelling and Heart Failure. J. Vis. Exp. (94), e52206, doi:10.3791/52206 (2014).

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