Transplantation of Pulmonary Valve Using a Mouse Model of Heterotopic Heart Transplantation

Summary

In order to understand the cellular and molecular mechanisms underlying neotissue formation and stenosis development in tissue engineered heart valves, a murine model of heterotopic heart valve transplantation was developed. A pulmonary heart valve was transplanted to recipient using the heterotopic heart transplantation technique.

Abstract

Tissue engineered heart valves, especially decellularized valves, are starting to gain momentum in clinical use of reconstructive surgery with mixed results. However, the cellular and molecular mechanisms of the neotissue development, valve thickening, and stenosis development are not researched extensively. To answer the above questions, we developed a murine heterotopic heart valve transplantation model. A heart valve was harvested from a valve donor mouse and transplanted to a heart donor mouse. The heart with a new valve was transplanted heterotopically to a recipient mouse. The transplanted heart showed its own heartbeat, independent of the recipient’s heartbeat. The blood flow was quantified using a high frequency ultrasound system with a pulsed wave Doppler. The flow through the implanted pulmonary valve showed forward flow with minimal regurgitation and the peak flow was close to 100 mm/sec. This murine model of heart valve transplantation is highly versatile, so it can be modified and adapted to provide different hemodynamic environments and/or can be used with various transgenic mice to study neotissue development in a tissue engineered heart valve.

Introduction

Congenital cardiovascular defects are one of the leading causes of infant mortality in the western world^1,2.  Among them, pulmonic valve stenosis and bicuspid aortic valve defects are a frequently occurring form³.  Heart valve replacement surgery is a routine choice of reconstructive surgeries; however, complications including stenosis and calcification of the heart valve, and lifelong dependence on anticoagulants are a significant source of chronic ill health and death^4-7. Moreover, the lack of growth potential requires revision surgeries, which further increases the mortality of those young patients^4,8,9.

Protocol

Note: All animal procedures were approved by the Nationwide Children’s Hospital Institutional Animal Care and Use Committee.

1. Pulmonary Heart Valve Harvest from a Heart Valve Donor Mouse

1. Autoclave all the surgical tools before the surgery: 1x fine scissors, 3x micro forceps, 2x micro vascular clamps, 1x clamp applying forceps, 1x micro needle holder, 1x spring scissors, 1x retractor.
2. A 6-8 week old female C57BL/6 mouse is used as a pulmonary heart valve donor. Remove the mouse from its cage and weigh it, then euthanize with a ketamine/xylazine cocktail (Ketamine, 200 mg/kg and xylazine, 20 mg/kg, IP) overdose.<....

Results

Figure 1 illustrates the schematics of the heart valve transplantation model using heterotopic heart transplantation. The heart valve was harvested from a donor heart and implanted onto a heart from a second donor mouse. Then the heart with the new heart valve was implanted to the abdomen of a recipient mouse. Figure 2 shows an illustration of the implanted heart on the abdominal space (A), right after heart transplantation (B), and 5 min after transplan.......

Discussion

The mortality rate of this procedure is close to 20%, which was mostly caused by hemorrhage at the PV transplantation site and anastomosis on the donor aorta to the recipient abdominal aorta. In most of the cases, the mortality rate decreases significantly 48 hr post surgery. The survival mice showed strong heart beats and blood flow through the implanted PV. The entire process takes four hours for an experienced micro surgeon. It will take roughly 250 mice to master the technique. The heterotopic heart transplantation i.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
DPBS	Gibco	14190-144
Microscope	Leica	M80
C57BL/6J (H-2b), Female	Jackson Laboratories	664	8-12 weeks
Ketamine Hydrochloride Injection	Hospira Inc.	NDC 0409-2053
Xylazine Sterile Solution	Akorn Inc.	NADA# 139-236
Ketoprofen	Fort Dodge Animal Health	NDC 0856-4396-01
Ibuprofen	PrecisionDose	NDC 68094-494-59
Heparin Sodium	Sagent Pharmaceticals	NDC 25021-400
Saline solution (Sterile 0.9% sodium chloride)	Hospira Inc.	NDC 0409-0138-22
0.9% Sodium chloride Injection	Hospira Inc.	NDC 0409-4888-10
Petrolatum Ophthalmic Ointment	Dechra Veterinary Products	NDC 17033-211-38
Iodine Prep Pads	Triad Disposables, Inc.	NDC 50730-3201-1
Alcohol Prep Pads	McKesson Corp.	NDC 68599-5805-1
Cotton tipped applicators	Fisher Sientific	23-400-118
Fine Scissor	FST	14028-10
Micro-Adson Forcep	FST	11018-12
Clamp Applying Forcep	FST	00072-14
S&T Vascular Clamp	FST	00396-01
Spring Scissors	FST	15008-08
Colibri Retractors	FST	17000-04
Dumont #5 Forcep	FST	11251-20
Dumont #7 - Fine Forceps	FST	11274-20
Dumont #5/45 Forceps	FST	11251-35
Tish Needle Holder/Forceps	Micrins	MI1540
Black Polyamide Monofilament Suture, 10-0	AROSurgical Instruments Corporation	TI638402	For sutureing the graft
Black Polyamide Monofilament Suture, 6-0	AROSurgical Instruments	SN-1956	For musculature and skin closure
Non Woven Sponges	McKesson Corp.	94442000
Absorbable hemostat	Ethicon	1961
1 ml Syringe	BD	309659
3 ml Syringe	BD	309657
10 ml Syringe	BD	309604
18 G 1 1/2 in, Needle	BD	305190
25 G 1 in., Needle	BD	305125
30 G 1 in., Needle	BD	305106
Warm Water Recircultor	Gaymar	TP-700
Warming Pad	Gaymar	TP-22G
Trimmer	Wahl	9854-500
VEVO2100 High Frequency Ultrasound	VisualSonics	http://www.visualsonics.com/vevo2100	The catalog number and pricing can be acquired from the sales representatives.
Ultrasound transmission gel	Parker Laboratories, INC.	01-02
Table Top Laboratory Animal Anesthesia System	VetEquip, INC.	901806
Isoflurane	Baxter	1001936060