Abstract 11552: Coronary Artery Anomalies in Endothelin-1 and Endothelin A Receptor Knockout Mice
Endothelin-1 (ET1) /Endothelin A receptor (ETAR) axis has important roles in regulating organ development. We have previously reported that ET1 and ETAR knockout mice display craniofacial defects and aortic arch malformations. To further investigate the developmental roles of the ET1/ETAR signaling, we generated mice in which reporter genes (GFP or LacZ) are knocked-in into the ETAR locus and found ETAR expression in the smooth muscle cells of the coronary artery as early as embryonic stages. To examine whether defects in the ET1/ETAR signaling may affect coronary artery development, we analyzed morphological changes in ET-1 or ETAR KO mice. Histological examination showed distended vessels in the interventricular septum in many of ET-1 or ETAR KO mice. An ink-injection into the mouse fetal coronary arteries revealed septal branches were abnormally enlarged at embryonic day 17.5 (E17.5), whereas the other part of the coronary arteries was not affected. We then examined the coronary vessel structure at various developmental stages; there were no anatomical differences between normal and KO mice until E14.5, when smooth muscle cells did not covered CD31-positive endothelial network in both wild-type and KO mice. At E17.5, ETAR- and SMA-positive mural cells are uniformly aligned as a single cell layer covering the endothelium in wild-type mice. However, in KO mice, large parts of enlarged septal branches were free of SMA-positive cells, indicating that coronary artery maturation through smooth muscle layer formation was impaired. Next we hypothesized these septal branch-specific phenotype might reflect the difference of cell sources, and we evaluated the distribution pattern of neural crest cells using Wnt1-Cre;R26R-LacZ mice. Wnt1-Cre-positive cells are distributed around the proximal portion of coronary arteries in all branches. However, only in the septal branch, Wnt1-Cre-positive cells distribute more distally and contributed to the smooth muscle layer. In ETAR KO mice, the number of Wnt1-Cre-positive cells in and around the smooth muscle layer was markedly decreased. These findings indicate that the ET-1/ETAR signaling is involved in coronary artery development by acting on neural crest cells contributing to the septal branch formation.
- © 2011 by American Heart Association, Inc.