Endothelial-Mesenchymal Transition Occurs during Embryonic Pulmonary Artery Development

Abstract

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 expressing alpha -smooth muscle actin (alpha-SM actin). To determine whether pulmonary endothelial cells undergo a transition to mesenchymal cells, the authors used pulmonary artery explants from 10- to 11-day-old chicken embryos and found that explanted endothelial cells detached from the monolayer and acquired mesenchymal characteristics. Some of these cells maintained immunoreactivity for von Willebrand factor (vWF), whereas other jointly lost vWF and gained alpha -SM actin expression (transitional cells), suggesting conversion to SMCs. Therefore, these findings strongly support the authors' in vivo observations and demonstrate that embryonic pulmonary endothelial cells undergo a transition to mesenchymal cells and participate in intimal thickening formation and pulmonary vascular remodeling.

The role of endothelial–mesenchymal transition in development and pathological process

“…Arciniegas reported that endothelial cells transdifferentiated into SMCs vessel walls in the advanced stages of chicken embryo development. And then, they demonstrated that embryonic pulmonary endothelial cells underwent a transition to mesenchymal cells and participated in intimal thickening formation and pulmonary vascular remodeling (9). During maturation of dorsal aorta in quail, endothelial cells experimentally labeled with a wheat germ agglutinin-colloidal gold marker were shown to differentiate into subendothelial mesenchymal cells that were positive for both endothelial and mural markers in the aortic wall (10).…”

Possible role of NFĸB in the embryonic vascular remodeling and the endothelial-mesenchymal transition process

“…13,14 Also, it has been proposed that the nuclear localization of both p50 and p65 subunits in intimal cells of atherosclerotic lesions is an indicator of NFκB activity. [20][21][22][23][24][25] We therefore also examined by double immunoperoxidase staining whether p50, p65 or IKKα were present at the nucleus of those cells that expressed α-SM actin at days E12-E14 of development, when the intimal thickening is evident.…”

“…12 It may involve several regulated steps: cell spreading, cell separation or loss of cell-cell contacts or adherence junctions, proteases, cytokine and growth factor synthesis and secretion, ECM remodeling, membrane receptor expression, cytoskeletal organization, cell separation from the substratum (cell detachment) and cell migration and differentiation. 12 Of particular significance, intimal thickening formation involving EndoMT has been described in both aortic 13 and pulmonary artery wall 14 during advanced stages of chicken embryo development and correlated with an increase in blood pressure that occurs during these stages. Nevertheless, the mechanisms by which endothelial transformation occurs, as well as the signals controlling this process, are only beginning to be elucidated.…”

Integrin-Mediated Endothelial Cell Adhesion and Activation of c-Src, EGFR and ErbB2 are Required for Endothelial-Mesenchymal Transition

“…Fixed and permeabilized cells were processed for immunofluorescence as previously described (Arciniegas et al, 2005) using the following antibodies: a mouse monoclonal antibody (mab) anti-human integrin 3 (GPIIIa, CD61) and a mab anti-chicken integrin 1 www.intechopen.com …”

“…Fixed cells were processed for immunoperoxidase as described previously (Arciniegas et al, 2005) using a rabbit pab raised against a short amino acid sequence containing phosphorylated Tyr845 of EGFR of human origin, and a rabbit pab raised against a short amino acid sequence containing phosphorylated Tyr877 of ErbB2/Neu of human origin (Santa Cruz Biotechnology). The images were captured using the Image Pro Plus software program.…”