Rat Heterotopic Abdominal Heart/Single-lung Transplantation in a Volume-loaded Configuration

Summary

We describe a novel technique for heterotopic abdominal heart-lung transplantation (HAHLT) in rats. The transplant configuration results in a partially loaded graft circulation, allowing direct functional assessment. This model may be employed for acute or chronic studies of function and immunologic status of the transplanted graft.

Abstract

Herein, we describe a novel technique for heterotopic abdominal heart-lung transplantation (HAHLT) in rats. The configuration of the transplant graft involves anastomosis of donor inferior vena cava (IVC) to recipient IVC, and donor ascending aorta (Ao) to recipient abdominal Ao. The right upper and middle lung lobes are preserved and function as conduits for blood flow from right heart to left heart.

There are several advantages to using this technique, and it lends itself to a broad range of applications. Because the graft is transplanted in a configuration that allows for dyamic volume-loading, cardiac function may be directly assessed in vivo. The use of pressure-volume conductance catheters permits characterization of load-dependent and load-independent hemodynamic parameters. The graft may be converted to a loaded configuration by applying a clamp to the recipient’s infra-hepatic IVC. We describe modified surgical techniques for both donor and recipient operations, and an ideal myocardial protection strategy. Depending on the experimental aim, this model may be adapted for use in both acute and chronic studies of graft function, immunologic status, and variable ventricular loading conditions. The conducting airways to the transplanted lung are preserved, and allow for acute lung re-ventilation. This facilitates analysis of the effects of the mixed venous and arterial blood providing coronary perfusion to the graft.

A limitation of this model is its technical complexity. There is a significant learning curve for new operators, who should ideally be mentored in the technique. A surgical training background is advantageous for those wishing to apply this model. Despite its complexity, we aim to present the model in a clear and easily applicable format. Because of the physiologic similarity of this model to orthotopic transplantation, and its broad range of study applications, the effort invested in learning the technique is likely to be worthwhile.

Introduction

The first rodent model of heterotopic abdominal heart transplantation (HAHT) was described by Abbott and colleagues in 1964¹. This technique, and subsequent modifications have been widely applied to characterize transplant graft function and immunologic status. The majority of HAHT techniques described involve a non-volume loaded heart^2,3. Models of HAHT involving volume-loaded ventricles have been described, but they are frequently limited in one or more respects.

Heterotopic abdominal heart-lung transplantation (HAHLT) with a volume-loaded left ventricle (LV) has been described previously. Chen and colleagues⁴

Protocol

All animals were housed and cared for in accordance with National and Institutional guidelines for the care and use of laboratory animals. Ethics approval for this protocol was granted by the University of British Columbia’s Animal Care Committee. Male, Sprague-Dawley rats weighing between 300 - 450 g were used for this protocol.

1. Donor Operation

1. Have approximately 100 ml of cardioplegia (RT) in a cylindrical flask connected to long intravenous (IV) catheter tubing by a 3-way stopcock. Use a stand to elevate the flask to approximately 80cm above the operative surface, enabling cardioplegia delivery by gravity.
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Results

The HAHLT technique described above is highly technical and requires close attention to detail. Table 1 highlights some of the key factors associated with successful versus unsuccessful procedures, and can be used as a guide for troubleshooting technical difficulties.

After the recipient aorta is unclamped, the graft coronary arteries should be seen to fill with oxygenated blood. Accordingly, the myocardium should become pink and well perfused. In technically successful experi.......

Discussion

Success with the technique described here will be predicated on several factors. Key among them will be ensuring stability of both donor and recipient animals, adopting meticulous operative technique that is safe and associated with minimal blood loss, ensuring complete cardioplegic arrest with uniform graft cooling, minimizing total ischemic time, and adequately de-airing the graft. As acknowledged above, the technique’s technical complexity is its chief limitation.

We have advanced pre.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Celsior Cardioplegic Soution	Genzyme		The solution is kept on ice throughout the procedure. We prepare our own solution, with slight modifications.
Rodent Ventilator	Harvard Apparatus	Model 683
Vital Sign Monitor	Nonin	Model 9847V	Displays SpO2 and heart rate.
IV Cannulae	Jelco	3063	24 - 26 G x 3/4" cannulae.
IV Tubing	CareFusion	MP9259-C	Short-length connector tubing (18 cm).
Surgical Clips	Teleflex Medical	001204	Horizon titanium ligating clips.
Sutures	Ethicon, Sharpoint	LA54G, AK-0107	3-0 silk reel, and 9-0 prolene suture (single-armed, DR5 needle).
Surgical Instruments	Not Applicable	Not Applicable	The instruments used are generic, and can be purchased from any surgical supply company.