Murine Intrapulmonary Tracheal Transplantation: A Model for Investigating Obliterative Airway Disease After Lung Transplantation

Summary

The murine intrapulmonary tracheal transplantation (IPTT) model is valuable for studying obliterative airway disease (OAD) after lung transplantation. It offers insights into lung-specific immunological and angiogenic behavior in airway obliteration after allotransplantation with high reproducibility. Here, we describe the IPTT procedure and its expected results.

Abstract

Murine intrapulmonary tracheal transplantation (IPTT) is used as a model of obliterative airway disease (OAD) following lung transplantation. Initially reported by our team, this model has gained use in the study of OAD due to its high technical reproducibility and suitability for investigating immunological behaviors and therapeutic interventions.

In the IPTT model, a rodent tracheal graft is directly inserted into the recipient's lung through the pleura. This model is distinct from the heterotopic tracheal transplantation (HTT) model, wherein grafts are transplanted into subcutaneous or omental sites, and from the orthotopic tracheal transplantation (OTT) model in which the donor trachea replaces the recipient's trachea.

Successful implementation of the IPTT model requires advanced anesthetic and surgical skills. Anesthetic skills include endotracheal intubation of the recipient, setting appropriate ventilatory parameters, and appropriately timed extubation after recovery from anesthesia. Surgical skills are essential for precise graft placement within the lung and for ensuring effective sealing of the visceral pleura to prevent air leakage and bleeding. In general, the learning process takes approximately 2 months.

In contrast to the HTT and OTT models, in the IPTT model, the allograft airway develops airway obliteration in the relevant lung microenvironment. This allows investigators to study lung-specific immunological and angiogenic processes involved in airway obliteration after lung transplantation. Furthermore, this model is also unique in that it exhibits tertiary lymphoid organs (TLOs), which are also seen in human lung allografts. TLOs are comprised of T and B cell populations and characterized by the presence of high endothelial venules that direct immune cell recruitment; therefore, they are likely to play a crucial role in graft acceptance and rejection. We conclude that the IPTT model is a useful tool for studying intrapulmonary immune and profibrotic pathways involved in the development of airway obliteration in the lung transplant allograft.

Introduction

Lung transplantation has been established as an effective treatment for patients with end-stage respiratory diseases. However, the median survival rate for human lung transplant recipients is only approximately 6 years, with the development of obliterative bronchiolitis (OB), a type of obstructive airway disease (OAD), being a major cause of death after the first year post transplantation¹.

Several animal models have been utilized to investigate the mechanism underlying OAD. One such model is the heterotopic tracheal transplantation (HTT) model². In this model, tracheal grafts are implanted in....

Protocol

All animals were treated in accordance with the guidelines set forth by the Canadian Council on Animal Care in the Guide to the Care and Use of Experimental Animals. The experimental protocol was approved by the Animal Care Committee of the Toronto General Hospital Research Institute, University Health Network.

1. Donor surgery

NOTE: BALB/c mice are used as an example of donors for the experiment. All procedures must be performed utilizing a sterile t.......

Discussion

The murine IPTT procedure includes critical steps. Regarding anesthesia, the first crucial step is endotracheal intubation. It is essential to hold the mouse at an appropriate height with its legs on the table to visualize the vocal cords and facilitate immediate intubation. Additionally, careful respiratory volume and positive end-expiratory pressure (PEEP) adjustment is necessary. Typically, a respiratory volume of 500 µL and a PEEP of 2 cmH₂O are sufficient for mice weighing 25-30 g. However, larger re.......

Materials

Name	Company	Catalog Number	Comments
BALB/cJ	The Jackson Laboratory	8-10 weeks 25-30 g	Male, Donor
BD 1 mL Syringe	Becton Dickinson	309659
BD PrecisionGlide Needle Aiguile BD PrecisionGlide	Becton Dickinson	305122
Bovie Change-A-Tip Deluxe High-Temperture	Bovie	DEL1
C57BL/6J	The Jackson Laboratory	8-10 weeks 25-30 g	Male, Recipient
Dumont #5/45 Forceps	F·S·T	11251-35
Ethicon Ligaclip Multiple -Clip Appliers-	Ethicon	LX107
Extra Fine Graefe Forceps	F·S·T	11150-10
Glover Bulldog Clamp	Integra	320-127
Halsted-Mosquito Hemostats	F·S·T	13009-12
Horizon Titanium Ligating Clips	Teleflex	001201
Leica M651 Manual surgical microscope for microsurgical procedures	Leica
Magnetix Fixator with spring lock	CD+ LABS	ACD-001
Microsurgical Scissor	Jarit	277-051
Mouse and Perinatal Rat Ventilator Model 687	Harvard	55-0001
Perfadex Plus	XVIVO	19850
Retractor Tip Blunt - 2.5 mm	CD+ LABS	ACD-011
small animal table	CD+ LABS	ACD-003
Surgipro Blue 24" CV-1 Taper, Double Armed	Covidien	VP702X
Systane ointment	Alconn	1444062
System Elastomer	CD+ LABS	ACD-007
Terumo Surflo IV Catheter, 20 G x 1 in	Terumo Medical Corporation	SR-OX2025CA
VMT table Top	benson	91803300