Endothelial-Mesenchymal Transition Occurs during Embryonic Pulmonary Artery Development

Pulmonary vascular remodeling is a process generally associated with pulmonary hypertension that involves intimal thickening, medial hyperthrophy, and plexiform lesions. Morphological studies during pulmonary hypertension have indicated that intimal thickening consists of immature smooth muscle cells (SMCs) associated with determined extracellular matrix components, suggesting an important role for these cells in vascular lesions. Controversy exists regarding the nature and origin of the cells conforming the intimal thickenings. In this study, the authors characterized the in vivo phenotype of the cells located in the pulmonary artery wall during the advanced stages of chicken embryo development and examined whether intimal thickenings are present in such stages. Immunolabeling of cryosections demonstrated presence of intimal thickenings composed of mesenchymal cells that may arise from the endothelium. These cells persist either as nonmuscle throughout the development, or possibly convert to cells expres...