VEGF-A signaling through Flk-1 is a critical facilitator of early embryonic lung epithelial to endothelial crosstalk and branching morphogenesis

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2005.11.022 Byline: Pierre-Marie Del Moral (a)(b), Frederic G. Sala (a), Denise Tefft (a)(b), Wei Shi (a)(b), Eli Keshet (c), Saverio Bellusci (a), David Warburton (a)(b) Keywords: Vascular endothelial growth factor-A (VEGF-A); Fetal liver kinase-1 (Flk-1); Bone morphogenetic protein-4 (BMP-4); Murine Sprouty-2 (mSpry-2); Murine Sprouty-4 (mSpry-4) Abstract: Vascular endothelial growth factor-A (VEGF-A) signaling directs both vasculogenesis and angiogenesis. However, the role of VEGF-A ligand signaling in the regulation of epithelial-mesenchymal interactions during early mouse lung morphogenesis remains incompletely characterized. Fetal liver kinase-1 (Flk-1) is a VEGF cognate receptor (VEGF-R2) expressed in the embryonic lung mesenchyme. VEGF-A, expressed in the epithelium, is a high affinity ligand for Flk-1. We have used both gain and loss of function approaches to investigate the role of this VEGF-A signaling pathway during lung morphogenesis. Herein, we demonstrate that exogenous VEGF 164, one of the 3 isoforms generated by alternative splicing of the Vegf-A gene, stimulates mouse embryonic lung branching morphogenesis in culture and increases the index of proliferation in both epithelium and mesenchyme. In addition, it induces differential gene and protein expression among several key lung morphogenetic genes, including up-regulation of BMP-4 and Sp-c expression as well as an increase in Flk-1-positive mesenchymal cells. Conversely, embryonic lung culture with an antisense oligodeoxynucleotide (ODN) to the Flk-1 receptor led to reduced epithelial branching, decreased epithelial and mesenchymal proliferation index as well as downregulating BMP-4 expression. These results demonstrate that the VEGF pathway is involved in driving epithelial to endothelial crosstalk in embryonic mouse lung morphogenesis. Author Affiliation: (a) Developmental Biology Program, Saban Research Institute, Children's Hospital Los Angeles, Department of Pediatric Surgery, USC Keck School of Medicine, 4650 Sunset Blvd., Los Angeles, CA 90027, USA (b) Center for Craniofacial Molecular Biology, Keck School of Medicine and School of Dentistry, University of Southern California, CA, USA (c) Department of Molecular Biology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel Article History: Received 20 November 2004; Revised 10 October 2005; Accepted 14 November 2005