Hemodynamic Characterization of Rodent Models of Pulmonary Arterial Hypertension

Summary

Pulmonary arterial hypertension (PAH) is a disease of pulmonary arterioles that leads to their obliteration and the development of right ventricular failure. Rodent models of PAH are critical in understanding the pathophysiology of PAH. Here we demonstrate hemodynamic characterization, with right heart catheterization and echocardiography, in the mouse and rat.

Abstract

Pulmonary arterial hypertension (PAH) is a rare disease of the pulmonary vasculature characterized by endothelial cell apoptosis, smooth muscle proliferation and obliteration of pulmonary arterioles. This in turn results in right ventricular (RV) failure, with significant morbidity and mortality. Rodent models of PAH, in the mouse and the rat, are important for understanding the pathophysiology underlying this rare disease. Notably, different models of PAH may be associated with different degrees of pulmonary hypertension, RV hypertrophy and RV failure. Therefore, a complete hemodynamic characterization of mice and rats with PAH is critical in determining the effects of drugs or genetic modifications on the disease.

Here we demonstrate standard procedures for assessment of right ventricular function and hemodynamics in both rat and mouse PAH models. Echocardiography is useful in determining RV function in rats, although obtaining standard views of the right ventricle is challenging in the awake mouse. Access for right heart catheterization is obtained by the internal jugular vein in closed-chest mice and rats. Pressures can be measured using polyethylene tubing with a fluid pressure transducer or a miniature micromanometer pressure catheter. Pressure-volume loop analysis can be performed in the open chest. After obtaining hemodynamics, the rodent is euthanized. The heart can be dissected to separate the RV free wall from the left ventricle (LV) and septum, allowing an assessment of RV hypertrophy using the Fulton index (RV/(LV+S)). Then samples can be harvested from the heart, lungs and other tissues as needed.

Introduction

Pulmonary arterial hypertension (PAH) is a disease of the pulmonary vasculature associated with inflammatory cell infiltration, smooth muscle proliferation and endothelial cell apoptosis. These changes result in obliteration of pulmonary arterioles, subsequently leading to right ventricular (RV) dysfunction and heart failure. In order to understand the pathophysiology underlying PAH and RV failure in PAH, a number of different models, including genetic and pharmacologic models, for studying this disease have been developed (reviewed elsewhere^1,2).

Of these models, the most popular are hypoxia-induced (Hx) PAH in the mouse and the....

Protocol

All procedures described follow the animal care guidelines of Duke University School of Medicine.

1. Prior to Starting the Procedure

Note: Prior to any animal procedures, ensure that appropriate institutional permission has been obtained. As with all procedures, use appropriate pain medication to ensure that there is no animal suffering.

1. Flush catheters with heparinized sterile saline (100 U/ml) to ensure the patency. Mark a point from the tip of the catheter equivalent to the length from the heart to the mid of the neck (approximately 4 cm for rats and 2 cm for mice).
2. Anesthetize the mouse ....

Results

As right heart catheterization in rodents is typically a terminal procedure that is not applicable to longitudinal follow-up, echocardiography is an excellent noninvasive alternative for screening and follow-up¹². While pulmonary artery systolic pressure in human PAH on echocardiography is usually derived from tricuspid regurgitation that is usually straightforward to be obtained in the apical view, such a view is not reliably obtained in rodents, preventing the estimation of pulmonary artery systolic pressure.......

Discussion

The protocols outlined here describe a comprehensive characterization of hemodynamics and right ventricular function in rodent models of pulmonary hypertension. While right heart catheterization as described here is a terminal procedure, the mortality associated with echocardiography is minimal, which allows for screening and follow-up of disease progression. However, similar to patients with PH having markedly increased mortality with anesthesia¹⁷, in our experience, rats with severe PH do not tolerate anesth.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Vevo 2100 Imaging System (120V)	VisualSonics, inc.	VS-11945
Vevo 2100 Imaging Station	VisualSonics, inc.
High-frequency Mechanical Transducers	VisualSonics, inc.	MS250, MS550D, MS400
Ultrasound Gel Parker	Laboratories Inc.	01-08
PowerLab 4/35	ADInstruments	ML765
Labchart 8	ADInstruments
BP transducer with stopcock and cable	ADInstruments	MLT1199
BP transducer calibration kit	ADInstruments	MLA1052
Mikro-Tip Pressure Catheter for mouse	Millar	SPR-1000	Alternative catheter available from Scisense FT111B (mouse) and FT211B (rat)
Mikro-Tip Pressure Catheter for rat	Millar	SPR-513	Alternative catheter available from Scisense FT111B (mouse) and FT211B (rat)
Millar Mikro-Tip ultra-miniature PV loop catheter for mice	Millar	PVR-1035	Alternative catheter available from Scisense FT112 (mouse)
Millar Mikro-Tip ultra miniature PV loop catheter for rats	Millar	SPR-869	Alternative catheter available from Scisense FT112 (mouse)
Millar PV system MPVS-300	Millar	MPVS-300
4-0 Silk Black Braid 100 Yard Spool	Roboz Surgical	SUT-15-2
6-0 Silk Black Braid 100 Yard Spool	Roboz Surgical	SUT-14-1
Iris Scissors, Delicate, Integra Miltex	VWR	21909-248
VWR Dissecting Scissors, Sharp/Blunt Tip	VWR	82027-588
VWR Delicate Scissors, 4 1/2"	VWR	82027-582
Two star Hemostats, Excelta	VWR	63042-090
Neutral-buffered formalin	VWR	89370-094
Crotaline	Sigma	C2401
SU5416	Tocris Biosciences	3037
3.5X-45X Boom Stand Trinocular Zoom Stereo Microscope	AmScope	SM-3BX
PE (Polyethylene Tubing)-10	Braintree Scientific Inc	PE10 36 FT
PE (Polyethylene Tubing)-50	Braintree Scientific Inc	PE50 36 FT
PE (Polyethylene Tubing)-60	Braintree Scientific Inc	PE60 36 FT
Tabletop Isoflurane Anesthesia Unit	Kent Scientific	ACV-1205S
Surgisuite multi-functional surgical platform	Kent Scientific	Surgisuite
Retractor set	Kent Scientific	SURGI-5002
Anesthesia induction chamber	VetEquip	941443
Anesthesia Gas filter canister	Kent Scientific	ACV-2001
Rodent nose cone	VetEquip	921431