title: TLR4 stimulation by LPS enhances angiogenesis in a co-culture system consisting of primary human osteoblasts and outgrowth endothelial cells.
abstract: The development of new approaches leading to fast and successful vascularization of tissue-engineered constructs is one of the most intensively studied subjects in tissue engineering and regenerative medicine. Recently, TLR4 activation and LPS stimulation of endothelial cells have been reported to promote angiogenesis in a variety of settings. In this study, we demonstrate that TLR4 activation by Ultrapure LPS Escherichia coli 0111:B4 (LPS-EB) significantly enhances microvessel formation in a co-culture system consisting of outgrowth endothelial cells (OECs) and primary human osteoblasts (pOBs). The precise modes of TLR4 action on the process of angiogenesis have also been investigated in this study. Using quantitative fluorescence microscopy in monocultures of OECs and pOBs, it was found that TLR4 activation through LPS-EB upregulates the expression level of TLR4/MYD88 and enhances both angiogenesis and osteogenesis. Furthermore, ELISA and qRT-PCR have shown that the level of two adhesion molecules (ICAM-1 and E-selectin), two cytokines (IL-6 and IL-8) and two growth factors (VEGF and PDGF-BB) related to angiogenesis increase significantly after LPS-EB treatment. This increased understanding of the role of TLR4 in angiogenesis could be of value in various settings related to tissue repair and tissue engineering. Moreover, since LPS and TLR4 agonists improve angiogenesis and osteogenesis, TLR4 agonists (endogenous or synthetic) could be used for angiogenesis intervention in vivo and therefore could be tested for their potential clinical applications in promoting angiogenesis in bone tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.
authors.affiliation: REPAIR-Lab, Institute of Pathology, University Medical Centre of the Johannes Gutenberg University, Mainz, Germany.|Department of Molecular and Biomedical Sciences, School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia.|School of Medicine, University of Notre Dame Australia, Fremantle, WA, Australia.
authors.forename: Bin
authors.initials: B
authors.lastname: Ma
authors.affiliation: REPAIR-Lab, Institute of Pathology, University Medical Centre of the Johannes Gutenberg University, Mainz, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Dohle
authors.affiliation: REPAIR-Lab, Institute of Pathology, University Medical Centre of the Johannes Gutenberg University, Mainz, Germany.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: REPAIR-Lab, Institute of Pathology, University Medical Centre of the Johannes Gutenberg University, Mainz, Germany.
authors.forename: Charles James
authors.initials: CJ
authors.lastname: Kirkpatrick
mesh_terms: D001842:Bone and Bones / Q000098:blood supply / Q000166:cytology / Q000378:metabolism; D018920:Coculture Techniques; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D055806:Microvessels / Q000166:cytology / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D010006:Osteoblasts / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects; D023822:Tissue Engineering / Q000379:methods; D051197:Toll-Like Receptor 4 / Q000819:agonists* / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C440499:lipopolysaccharide, Escherichia coli O111 B4
keywords: Toll-like receptor 4; angiogenesis; lipopolysaccharide; outgrowth endothelial cells; primary human osteoblasts