title: The morphogenetically active polymer, inorganic polyphosphate complexed with GdCl3, as an inducer of hydroxyapatite formation in vitro.
abstract: Inorganic polyphosphate (polyP) is a physiological polymer composed of tens to hundreds of phosphate units linked together via phosphoanhydride bonds. Here we compared the biological activity of polyP (chain length of 40 phosphate units), complexed with Gd(3+) (polyP·Gd), with the one caused by polyP (as calcium salt) and by GdCl3 alone, regarding their potencies to induce hydroxyapatite (HA) formation in SaOS-2 cells in vitro. The three compounds, GdCl3, polyP and polyP·Gd were found to be non-toxic at concentrations up to at least 30μM. Selecting a low, 5μM, concentration it was found that polyP·Gd significantly induced HA formation, as determined by Alizarin Red S staining and by quantitative determinations using that dye. Under those conditions polyP·Gd and to a smaller extent also polyP or GdCl3 (5μM each) caused HA crystal formation arranged in a nest-like pattern. Exposure of cells to polyP·Gd resulted in a strong increase in alkaline phosphatase activity; this enzyme did not cause a distinct degradation of polyP but of polyP·Gd which was extensively hydrolyzed. The morphogenetic activity of gadolinium, in the form of polyP·Gd, is underscored by the finding that this polymer causes a strong upregulation of the genes encoding morphogenetic protein-2 (BMP2) as well as collagen type I. It is concluded that polyP·Gd is not an inert polymer but acts as a morphogenetically active polymer and induces HA formation in vitro.
authors.affiliation: ERC Advanced Investigator Grant Research Group at Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, D-55128 Mainz, Germany. Electronic address: wang013@uni-mainz.de.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Chemical Biology School of Pharmaceutical Sciences, Peking University, Xueyuan Road 38, Beijing 100191, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Chemical Biology School of Pharmaceutical Sciences, Peking University, Xueyuan Road 38, Beijing 100191, China.
authors.forename: Kui
authors.initials: K
authors.lastname: Wang
authors.affiliation: ERC Advanced Investigator Grant Research Group at Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, D-55128 Mainz, Germany.
authors.forename: Meik
authors.initials: M
authors.lastname: Neufurth
authors.affiliation: ERC Advanced Investigator Grant Research Group at Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, D-55128 Mainz, Germany.
authors.forename: Heinz C
authors.initials: HC
authors.lastname: Schröder
authors.affiliation: ERC Advanced Investigator Grant Research Group at Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, D-55128 Mainz, Germany.
authors.forename: Shunfeng
authors.initials: S
authors.lastname: Wang
authors.affiliation: ERC Advanced Investigator Grant Research Group at Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, D-55128 Mainz, Germany. Electronic address: wmueller@uni-mainz.de.
authors.forename: Werner E G
authors.initials: WEG
authors.lastname: Müller
mesh_terms: D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D017886:Durapatite / Q000819:agonists* / Q000378:metabolism*; D005682:Gadolinium / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D011108:Polymers / Q000737:chemistry / Q000494:pharmacology*; D011122:Polyphosphates / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D011108:Polymers; D011122:Polyphosphates; D017886:Durapatite; D005682:Gadolinium; C038958:gadolinium chloride
keywords: Bone; Gadolinium; Hydroxyapatite formation; Inorganic polyphosphate; Osteoblasts; SaOS-2 cells