title: Lysophosphatidic acid cooperates with EGF in inducing branching morphogenesis of embryonic mouse salivary epithelium.
abstract: Epithelial morphogenesis is supported by diffusible growth factors and by nondiffusible cell substrata, such as laminin and fibronectin. When embedded in a laminin-rich basement-membrane substratum, embryonic mouse submandibular epithelium undergoes cell proliferation and branching morphogenesis in response to epidermal growth factor (EGF) in mesenchyme-free culture but not in serum-free medium. In this study, we sought to identify the biologically active factor in serum. As this factor was heat-stable and trypsin-resistant, the lipid fraction was analyzed. Horse serum was fractionated by ethanol extraction, Folch partition with chloroform-methanol-water, and high-performance liquid chromatography, and we tested the branch-inducing activity of each fraction. We also analyzed the partially purified fraction with a mass spectrometer, indicating that the active fraction largely consisted of lysophosphatidyl-hexose. Finally we identified the molecule as lysophosphatidic acid (LPA), because, whereas lysophosphatidyl-inositol had only a slight branch-inducing activity, its relevant LPA fully substituted for serum and induced branching morphogenesis in cooperation with EGF. LPA receptor genes were expressed in submandibular epithelial cells. DNA-synthesizing cells were abundant only when cultured in the presence of both EGF and LPA, but not either singly.
authors.affiliation: Department of Life and Earth Sciences, Graduate School of Science and Technology, Chiba University, Chiba, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Noguchi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okamoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kasama
authors.forename: Shinobu
authors.initials: S
authors.lastname: Imajoh-Ohmi
authors.forename: Takashi
authors.initials: T
authors.lastname: Karatsu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nogawa
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D004848:Epithelium / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D006358:Hot Temperature; D050356:Lipid Metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D051379:Mice; D008813:Mice, Inbred ICR; D009024:Morphogenesis / Q000187:drug effects*; D049368:Receptors, Lysophosphatidic Acid / Q000235:genetics; D012469:Salivary Glands / Q000166:cytology / Q000187:drug effects* / Q000196:embryology* / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D008246:Lysophospholipids; D049368:Receptors, Lysophosphatidic Acid; C025449:lysophosphatidylinositol; D004815:Epidermal Growth Factor; D004247:DNA; D014357:Trypsin; C032881:lysophosphatidic acid