Development of the pulmonary vasculature in the gray short-tailed opossum (Monodelphis domestica) – 3D reconstruction by microcomputed tomography

Abstract

AbstractThe marsupial gray short-tailed opossum (Monodelphis domestica) is born at the late canalicular stage of lung development and the lungs are structurally immature compared to eutherians. The majority of lung development, including the maturation of pulmonary vasculature, takes place in ventilated functioning state during the postnatal period.The current study uses X-ray computed tomography (µCT) to three-dimensionally reconstruct the vascular trees of the pulmonary artery and pulmonary vein in the marsupial gray short-tailed opossum to investigate the vascular genesis during the postnatal period. The development of the pulmonary vasculature was examined in 15 animals from neonate to postnatal day 57. The final 3-D reconstructions of the pulmonary artery and pulmonary vein in the neonate and at 21, 35 and 57 dpn were transformed into a centerline model of the vascular trees. Based on the reconstructions, the generation of end-branching vessels, the median and maximum generation and the number of vessels were calculated for the lungs.The pulmonary vasculature follows the lung anatomy with six pulmonary lobes indicated by the bronchial tree. The pulmonary arteries follow the bronchial tree closely, in contrast to the pulmonary veins, which run between the pulmonary segments. At birth the pulmonary vasculature has a simple branching pattern with a few vessel generations. Compared to the bronchial tree, the pulmonary vasculature appears to be more developed and extends to the large terminal air spaces. The pulmonary vasculature of the lungs from neonate to postnatal day 57 develops along the bronchial tree and shows a marked gain in volume and a progressive increase in vascular complexity and density. The gray short-tailed opossum resembles the assumed mammalian ancestor and is suitable to inform on the evolution of the mammalian lung. Vascular genesis in the marsupial bears resemblance to developmental patterns described in eutherians. Lung development in general seems to be highly conservative within mammalian evolution.