title: Gap junction communication mediates transforming growth factor-beta activation and endothelial-induced mural cell differentiation.
abstract: During blood vessel assembly, endothelial cells recruit mesenchymal progenitors and induce their differentiation into mural cells via contact-dependent transforming growth factor-beta (TGF-beta) activation. We investigated whether gap junction channels are formed between endothelial cells and recruited mesenchymal progenitors and whether intercellular communication is necessary for endothelial-induced mural cell differentiation. Mesenchymal progenitors from Cx43-/- murine embryos and Cx43+/+ littermates were cocultured with prelabeled endothelial cells. Intracellular dye injection and dual whole-cell voltage clamp revealed that endothelial cells formed gap junction channels with Cx43+/+ but not Cx43-/- progenitors. In coculture with endothelial cells, Cx43-/- progenitors did not undergo mural cell differentiation as did Cx43+/+ cells. Stable reexpression of Cx43 in Cx43-/- cells (reCx43) restored their ability to form gap junctions with endothelial cells and undergo endothelial-induced mural cell differentiation. Cocultures of endothelial cells and either Cx43+/+ or reCx43 mesenchymal cells produced activated TGF-beta; endothelial-Cx43-/- cocultures did not. However, Cx43-/- cells did produce latent TGF-beta and undergo mural cell differentiation in response to exogenous TGF-beta1. These studies indicate that gap junction communication between endothelial and mesenchymal cells mediates TGF-beta activation and subsequent mural cell differentiation.
authors.affiliation: Department of Pediatrics, Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA. khirschi@bcm.tmc.edu
authors.forename: Karen K
authors.initials: KK
authors.lastname: Hirschi
authors.forename: Janis M
authors.initials: JM
authors.lastname: Burt
authors.forename: Kendal D
authors.initials: KD
authors.lastname: Hirschi
authors.forename: Cuiping
authors.initials: C
authors.lastname: Dai
mesh_terms: D000818:Animals; D002417:Cattle; D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000378:metabolism; D017629:Gap Junctions / Q000502:physiology*; D015870:Gene Expression; D007150:Immunohistochemistry; D007546:Isoquinolines / Q000008:administration & dosage / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008648:Mesoderm / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008845:Microinjections; D018408:Patch-Clamp Techniques; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D018031:Connexin 43; D005456:Fluorescent Dyes; D007546:Isoquinolines; D016212:Transforming Growth Factor beta; C017475:lucifer yellow