title: Nonenzymatic Transformation of Amorphous CaCO3 into Calcium Phosphate Mineral after Exposure to Sodium Phosphate in Vitro: Implications for in Vivo Hydroxyapatite Bone Formation.
abstract: Studies indicate that mammalian bone formation is initiated at calcium carbonate bioseeds, a process that is driven enzymatically by carbonic anhydrase (CA). We show that amorphous calcium carbonate (ACC) and bicarbonate (HCO3 (-) ) cause induction of expression of the CA in human osteogenic SaOS-2 cells. The mineral deposits formed on the surface of the cells are rich in C, Ca and P. FTIR analysis revealed that ACC, vaterite, and aragonite, after exposure to phosphate, undergo transformation into calcium phosphate. This exchange was not seen for calcite. The changes to ACC, vaterite, and aragonite depended on the concentration of phosphate. The rate of incorporation of phosphate into ACC, vaterite, and aragonite, is significantly accelerated in the presence of a peptide rich in aspartic acid and glutamic acid. We propose that the initial CaCO3 bioseed formation is driven by CA, and that the subsequent conversion to calcium phosphate/calcium hydroxyapatite (exchange of carbonate by phosphate) is a non-enzymatic exchange process.
authors: ERC Advanced Investigator Grant Research Group, Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128 Mainz (Germany). wmueller@uni-mainz.de.
authors: Werner E G
authors: WE
authors: Müller
authors: ERC Advanced Investigator Grant Research Group, Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128 Mainz (Germany).
authors: Meik
authors: M
authors: Neufurth
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Xueyuan Road 38, Beijing 100191 (China).
authors: Jian
authors: J
authors: Huang
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Xueyuan Road 38, Beijing 100191 (China).
authors: Kui
authors: K
authors: Wang
authors: Laboratory of Advanced Materials of Ministry of Education of China, School of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China).
authors: Qingling
authors: Q
authors: Feng
authors: ERC Advanced Investigator Grant Research Group, Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128 Mainz (Germany).
authors: Heinz C
authors: HC
authors: Schröder
authors: NanotecMARIN GmbH, Duesbergweg 6, 55128 Mainz (Germany).
authors: Bärbel
authors: B
authors: Diehl-Seifert
authors: Department of Physical Chemistry of Polymers, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany).
authors: Rafael
authors: R
authors: Muñoz-Espí
authors: ERC Advanced Investigator Grant Research Group, Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University, Duesbergweg 6, 55128 Mainz (Germany). wang013@uni-mainz.de.
authors: Xiaohong
authors: X
authors: Wang
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D049872:Bivalvia / Q000378:metabolism; D002119:Calcium Carbonate / Q000378:metabolism*; D002130:Calcium Phosphates / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000235:genetics; D002460:Cell Line; D017886:Durapatite / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D010012:Osteogenesis; D010455:Peptides / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D049833:Sepia / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D002130:Calcium Phosphates; D010455:Peptides; D010710:Phosphates; D017886:Durapatite; C020243:calcium phosphate; D002256:Carbonic Anhydrases; D002119:Calcium Carbonate; C018279:sodium phosphate
keywords: D/E peptide; biological activity; biomineral skeleton; bone formation; calcium; calcium phosphate