Connexin43 deficiency causes dysregulation of coronary vasculogenesis

• Published in: Developmental biology 2005-08, Vol.284 (2), p.479-498
• Main Authors: Walker, Diana L., Vacha, Scott J., Kirby, Margaret L., Lo, Cecilia W.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Biomarkers; Connexin 43 - deficiency; Connexin 43 - genetics; Connexin43; Coronary vessels; Coronary Vessels - embryology; Crosses, Genetic; Endothelial cells; Endothelial Cells - physiology; Endothelium, Vascular - cytology; Endothelium, Vascular - metabolism; Fibroblasts - physiology; Gene Expression Regulation, Developmental; Genes, Reporter; Heart - embryology; Heart development; Heterozygote; Immunohistochemistry; Knockout; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Microarray Analysis; Models, Biological; Muscle, Smooth, Vascular - metabolism; Neovascularization, Physiologic - physiology; Receptors, Notch; Signal Transduction; Transforming Growth Factor beta - genetics; Transforming Growth Factor beta - metabolism; Vascular Endothelial Growth Factor A - metabolism; Vascular smooth muscle; VEGF
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2005.06.004

The connexin43 knockout (Cx43α1 KO) mouse dies at birth from outflow obstruction associated with infundibular pouches. To elucidate the origin of the infundibular pouches, we used microarray analysis to investigate gene expression changes in the pouch tissue. We found elevated expression of many genes encoding markers for vascular smooth muscle (VSM), endothelial cells, and fibroblasts, cell types that are epicardially derived and essential for coronary vasculogenesis. This was accompanied by increased expression of VEGF and genes in the TGFβ and VEGF/Notch/Eph cell-signaling pathways known to regulate vasculogenesis/angiogenesis. Using immunohistochemistry and a VSM lacZ reporter gene, we confirmed an abundance of ectopic VSM and endothelial cells in the infundibular pouch and in some regions of the right ventricle forming secondary pouches. This was associated with distinct thinning of the compact myocardium. TUNEL labeling showed increased apoptosis in the pouch tissue, in agreement with the finding of altered expression of many apoptotic genes. Defects in vascular remodeling were indicated by a marked reduction in the branching complexity of the distal coronary arteries. In the near term KO mouse, we also observed a profusion of large coronary vascular plexuses subepicardially. This was associated with elevated epicardial expression of VEGF and abnormal epicardial cell morphology. Together, these observations indicate that dysregulated coronary vasculogenesis plays a pivotal role in formation of the infundibular pouches and suggests an essential role for Cx43α1 gap junctions in coronary vasculogenesis and vascular remodeling.