Pulmonary circulation imaging: embryology and normal anatomy.

This review focuses on the embryology and normal imaging anatomy of the pulmonary circulation, with emphasis on the major arterial and venous vasculature. The pulmonary circulation and parenchyma have a complex intertwined embryologic origin. Understanding the embryologic basis of normal pulmonary vasculature aids recognition of anomalies and visceral situs in the chest. Adaptive changes to congenital anomalies of the pulmonary arterial vasculature are used to contrast from normal and review associated temporal adaptive vascular and parenchymal changes.

Functional impact of heterogeneous nuclear ribonucleoprotein A2/B1 in smooth muscle differentiation from stem cells and embryonic arteriogenesis.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) play various roles in transcriptional and post-transcriptional modulation of gene expression. However, it remains unclear if hnRNPs are associated with smooth muscle cell (SMC) differentiation from stem cells and embryonic arteriogenesis. In this study, mouse embryonic stem (ES) cells were cultivated on collagen IV-coated plates and smooth muscle differentiation medium. We found that hnRNPA2/B1 gene and protein expression was significantly up-regulated following 3-7 days of cell differentiation. hnRNPA2/B1 knockdown resulted in down-regulation of specific smooth muscle markers and transcription factors, whereas enforced expression of hnRNPA2/B1 enhanced the expression of these genes. Moreover, we demonstrated by using luciferase and chromatin immunoprecipitation assays that hnRNPA2/B1 could transcriptionally regulate SMC gene expression through direct binding to promoters of Smαa and Sm22α genes. We further demonstrated that chromobox protein homolog gene 3, a previously identified SMC differentiation regulatory nuclear protein, is required for hnRNPA2/B1-mediated SMC differentiation gene expression. Importantly, specifically designed Hnrnpa2/b1 morpholinos for in vivo knockdown could inhibit the migration and differentiation of neural crest cells into SMCs in chick embryos. This resulted in the maldevelopment of branchial arch arteries and increased embryo lethality at a later developmental stage. Our findings demonstrated that hnRNPA2/B1 plays a functional role in SMC differentiation from stem cells in vitro and embryonic branchial arch artery development. This indicates that hnRNPA2/B1 is a potential modulating target for deriving SMCs from stem cells and cardiovascular regenerative medicine.

Morphological and embryological characteristics of bronchial arteries in the rat.

There have been no previous reports of detailed macroscopic findings of the bronchial arteries, the nutrial vessels of the lungs. Also, previously, very little was known about the developmental processes of the bronchial arteries in rats and other laboratory animals. In the present study, we dissected bronchial arteries of adult rats from their origin to the pulmonary hilus, and examined developmental processes of bronchial arteries in a series of rat embryos. We observed one right bronchial artery and one left bronchial artery. The right artery arose from the right highest intercostal artery, ran together with the right vagus nerve along the right side of the trachea and right principal bronchus and reached the pulmonary hilus. The left artery arose from the left internal thoracic artery, ran along the left vagus nerve on the ventral surface of the thoracic aorta, and reached the dorsal surface of the left principal bronchus. In a series of 12 to 20.5-day-old rat embryos, the right bronchial artery was clearly identified in 20.5, 18.5, and 16.5-day-old embryos. In a 15.5-day-old embryo, a vessel corresponding to the right bronchial artery was recognized within the capillary plexus extending along the right lateral surface of the bronchus. In ontogenetic development, there appears to be little difference in completion time of the extrapulmonary part of the bronchial arteries between humans and rats.

Airway and blood vessel interaction during lung development.

In the adult lung the pulmonary arteries run alongside the airways and the pulmonary veins show a similar branching pattern to the arteries, though separated from them. During early fetal development the airways act as a template for pulmonary blood vessel development in that the vessels form by vasculogenesis around the branching airways. In later lung development the capillary bed is essential for alveolar formation. This paper reviews evidence for the interaction of the airways and blood vessels in both normal and abnormal lung development.

Superior bronchial artery arising from the left common carotid artery: embryology and clinical considerations.

A bronchial artery arising from the left common carotid artery was incidentally documented during cerebral angiography in a 64-year-old patient. This variant can be understood as the adult persistence of a primitive bronchial branch arising from the third branchial arch. It represents a potential pitfall for the identification and treatment of the bleeding source in patients with hemoptysis.

A common bronchial arterial trunk arising from a left subclavian artery: a rare anatomic variant.

The origin of the bronchial arteries is very variable. An exceptional case is reported of a common bronchial arterial trunk arising from a left subclavian artery discovered incidentally during angiography in a patient without any pulmonary disease. An embryologic explanation is proposed for this anatomic variant.

Development of the pharyngeal arch system related to the pulmonary and bronchial vessels in the avian embryo. With a concept on systemic-pulmonary collateral artery formation.

BACKGROUND: The literature is ambiguous as to the question of the developmental background of systemic-pulmonary collateral arteries. These are found in combination with various congenital heart malformations such as pulmonary atresia. From a clinical point of view, it is of interest to know whether we are dealing with the persistence of transient embryological vessels such as ventral segmental arteries or parts of pharyngeal arch arteries or with the prenatal or postnatal recruitment of the bronchial vasculature that normally supplies the lung. This study of the embryology of the extrapulmonary and intrapulmonary vasculature aims at a better understanding of the variations in origin, course, branching pattern, and histology of collateral arteries. METHODS AND RESULTS: Serial sections of quail embryos ranging between stage HH11 and stage HH28 were incubated with a monoclonal antibody (alpha MB1) against endothelial cells and their precursors. Additional series of chick embryos were injected with india ink to study the lumenized vascular patterns. A splanchnic plexus consisting of endothelial cells and precursors is present around the foregut before the lung buds develop. This plexus expands and gives rise to the pharyngeal arch arteries, the ventral pharyngeal veins, the pulmonary vessels, and the bronchial vessels, including the intrapulmonary vessel network. During two subsequent periods, the splanchnic plexus is transiently connected to the systemic arteries and veins. The bronchial arteries and veins develop in the second period from these transient vessels. The expansion and extension of the splanchnic plexus to many organs during the formation of the bronchial vessels explains the varying course and branching pattern of the bronchial vasculature. CONCLUSIONS: These results show that we are not dealing with two or more individual vascular systems that contribute to the developing vessels of the lungs but with one vascular plexus that normally gives rise to the pulmonary and bronchial vasculature but has the potential to give rise to other systemic-pulmonary connections.

Pulmonary aeration after unilateral fetal ligation of pulmonary artery in neonatal rabbits.

When the pulmonary artery was ligated at the gestational age of 30 days, 9 out of the 17 rabbit fetuses had vital lungs and in 7 of these the lungs were aerated after breathing for 15 min to 1 h. Ligation before this gestational age caused necrotic lungs in all 13 rabbit fetuses. On the basis of this we can conclude that the bronchial circulation is not sufficient to ensure vitality of the fetal lung and the pulmonary circulation does not play a major role in the primary aeration of the lungs at birth.

Development of the right outflow tract and pulmonary arterial supply.

The branchial arch vessels of the human embryo have been studied by histological and radiographic methods and the modelling that occurs during the period Day 25-Day 52 postfertilization is described. It has been shown that the myoendocardial reticulum is reamed out by blood flow and it is suggested that hydrodynamic force is the fundamental factor which determines chamber structure of the heart and flow pattern in the outflow tracts and great vessels. The sixth aortic arch vessels contribute tissue to the pulmonary trunk and proximal pulmonary arteries. The 'postbranchial pulmonary arteries' are morphologically distinct and form the pulmonary arteries at the lung hila. The primitive pulmonary plexus around the tips of the developing tracheobronchial primordia is formed from segmental vessels arising from the dorsal aorta. Bronchial arteries can be demonstrated only late in intrauterine life. The numerous bronchopulmonary precapillary anastomoses which are found in the fetus at this time have been demonstrated radiographically.