Pulmonary vascular remodeling in rats with unilaterally banded lobar pulmonary veins

Abstract

AbstractAlthough pulmonary vascular disease occurs in association with pulmonary venous obstruction, a model of pulmonary vascular lesions in this setting in small laboratory animals has yet to be described. The objective of this study was to determine if unilateral banding of pulmonary veins in the rat would produce pulmonary vascular disease that mimicked key aspects of the human disorder. Rats were anesthetized and, after mechanical ventilation and thoracotomy, one of the four pulmonary veins was banded to reduce its external diameter by approximately 65–75% to 0.8 mm. Additional animals, sham-operated controls, were treated identically except for venous banding. Mortality did not differ between groups and was less than 20%. Eight weeks after surgical preparation, moderate pulmonary hypertension was demonstrated with a mean pressure in the pulmonary artery of 24.9 mm Hg (range 19.25 – 30.0) in the banded group versus 18.7 mm Hg (range 16.6 – 19.3) for sham-operated animals. Pulmonary cineangiography in rats with banded pulmonary veins demonstrated marked pulmonary congestion and a prolonged residence time of contrast medium in the capillary circulation of the lung region subjected to banding. Angiographically, non-banded lungs were similar to shams. Histopathology of the vein-banded region revealed venous congestion, arterialization of veins, perivenular edema, and sparse to moderate inflammation. Prominent bronchial vessels, pulmonary arterial medial and occasional intimal thickening, and periarterial inflammation were also observed in banded regions. Similar inflammation around pulmonary arterial and pulmonary venous vessels was noted in contralateral lung lobes but not in sham-operated control rats. Morphometric evaluation of all muscular pulmonary arteries from 50–200μ external diameter accompanying airways to the level of terminal and respiratory bronchioles indicated that the medial area in lung regions subjected to venous banding was over three times greater than in shams. Pulmonary arteries from the contralateral, unbanded lungs of treated animals also exhibited a two-fold increase in medial area. These findings indicate that a modest degree of pulmonary venous banding in rats produces congestion and causes alterations in lung vessels which are reminiscent of those observed in humans with pulmonary venous outflow obstruction. Such a model in a cost-effective laboratory animal should be useful for delineating the specific mechanisms underlying these alterations.