Implantation of an Isoproterenol Mini-Pump to Induce Heart Failure in Mice

Summary

The chronic administration of isoproterenol via an implanted osmotic pump has been used widely to mimic advanced heart failure in mice. Here, we describe detailed methods in surgical mini-pump implantation for the continuous isoproterenol administration over 3 weeks, as well as, echocardiographic assessment for the successful model creation.

Abstract

Isoproterenol (ISO), is a non-selective beta-adrenergic agonist, that is used widely to induce cardiac injury in mice. While the acute model mimics stress-induced cardiomyopathy, the chronic model, administered through an osmotic pump, mimics advanced heart failure in humans. The purpose of the described protocol is to create the chronic ISO-induced heart failure model in mice using an implanted mini-pump. This protocol has been used to induce heart failure in 100+ strains of inbred mice. Techniques on surgical pump implantation are described in detail and may be relevant to anyone interested in creating a heart failure model in mice. In addition, the weekly cardiac remodeling changes based on echocardiographic parameters for each strain and expected time to model development are presented. In summary, the method is simple and reproducible. Continuous ISO administered via the implanted mini-pump over 3 to 4 weeks is sufficient to induce cardiac remodeling. Finally, the success for ISO model creation may be assessed in vivo by serial echocardiography demonstrating hypertrophy, ventricular dilation, and dysfunction.

Introduction

Heart failure with reduced ejection fraction (HFrEF) is accompanied by a well-recognized compensatory response of the sympathetic nervous system to maintain cardiovascular homeostasis¹. Hemodynamic stress and deleterious effects on the heart and circulation were observed with chronic activation. These have become the cornerstone of contemporary pharmacotherapy for heart failure and are important mechanisms in the progression of heart failure and therapeutic antagonism of neurohormonal systems¹.

Several mouse models are available for basic investigations of heart failure. Genetic models are att....

Protocol

This protocol adheres to the animal care guidelines of the University of California, Los Angeles (ARC protocol #2010-075). Readers are advised to adhere to their own IACUC-approved protocol, as peri-procedure mouse care and analgesia management may be institution-specific.

1. Preparation of isoproterenol osmotic pump

NOTE: This procedure has been applied successfully on 9+ week-old female mice weighing 18+ g from over 100 inbred mouse strains, as well as, in male mice in a subset of strains. There is no maximum body weight limit for this procedure. Always include age-matched controls, as it is unknown whether the a....

Results

In our previously published study, we administered an ISO dosage of 30 mg/kg/d over 21 days via the osmotic pump across 105 Hybrid Mouse Diversity Panel (HMDP) strains^2,13. We assessed outcomes using echocardiogram performed at baseline, week 1, 2 and 3 of ISO treatment (Figure 1). Similar to a prior study where the authors studied the impact of isoproterenol among 23 mouse strains¹⁴, we observed striking inte.......

Discussion

We have applied this method to over 100+ strains of inbred mice to assess cardiac outcomes due to chronic beta-adrenergic stimulation^2,13. Significant differences in susceptibility to isoproterenol are known to exist among mouse strains and may be customized to the strain of interest as needed¹⁶. This may be due to the variation in beta-adrenergic receptor function between mouse strains¹⁷, strain-dependent differenc.......

Materials

Name	Company	Catalog Number	Comments
Micro-Osmotic Pump System with Flow Moderator in Place	Alzet	Model 1004	Includes filling tube, flow moderator and pump body
(-)-Isoproterenol hydrochloride	Sigma-Aldrich	16504-1G	(-)-Isoproterenol hydrochloride is a powder that needs to be stored at -20°C.
1 ml sterile syringe	VWR	BD309602
30 W LED Fiber optic O-ring light microscope illuminator	AmScope	SKU: LED-30WR
5-0 COATED VICRYL (polyglactin 910) Suture	Ethicon	J303H	5-0, absorbable
Fine Scissors - Sharp	FST	14060-09
Glass beads	FST	18000-46
Hot bead sterilizers	FST	18000-50
Iris forceps	WPI	15915
Look Sharpoint 6-0, 18" Black Nylon Monofilament Suture	LOOK	AA-2176	6-0, non-absorbable
Needle holder	WPI	15926
Normal Saline, 0.9% NaCl	Fisher	89167-772