title: Identification of dicalcium phosphate dihydrate deposited during osteoblast mineralization in vitro.
abstract: The hydroxyapatite (HAP) with variable chemical substitutions has been considered as the major component in the mineralized part of bones. Various metastable crystalline phases have been suggested as transitory precursors of HAP in bone, but there are no consensuses as to the nature of these phases and their temporal evolution. In the present study, we cultured rat calvarial osteoblasts with ascorbate and β-glycerophosphate to explore which calcium phosphate precursor phases comprise the initial mineral in the process of osteoblast mineralization in vitro. At the indicated time points, the deposited calcium phosphate was analyzed after removing organic substances from the extracellular matrix with hydrazine. The features comparable to dicalcium phosphate dihydrate (DCPD) and octacalcium phosphate (OCP), in addition to HAP, were detected in the mineral phases by high resolution transmission electron microscopy. And there was a trend of conversion from DCPD- and OCP-like phases to HAP in the course of mineralization, as indicated by Fourier-transform infrared microspectroscopy, energy-dispersive X-ray spectroscopy and synchrotron X-ray powder diffraction analyses. Besides, biochemical assay showed a progressive decrease in the ratio of mineral-associated proteins to calcium with time. These findings suggest that DCPD- and OCP-like phases are likely to occur on the course of osteoblast mineralization, and the mineral-associated proteins might be involved in modulating the mineral phase transformation.
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, PR China.
authors: Zheng-Lai
authors: ZL
authors: Zhang
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, PR China.
authors: Xiao-Rong
authors: XR
authors: Chen
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, PR China.
authors: Sha
authors: S
authors: Bian
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, PR China. Electronic address: jhuang@bjmu.edu.cn.
authors: Jian
authors: J
authors: Huang
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, PR China. Electronic address: tlzhang@bjmu.edu.cn.
authors: Tian-Lan
authors: TL
authors: Zhang
authors: Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, PR China.
authors: Kui
authors: K
authors: Wang
mesh_terms: D000818:Animals; D002113:Calcification, Physiologic; D002130:Calcium Phosphates / Q000032:analysis* / Q000378:metabolism; D002478:Cells, Cultured; D017886:Durapatite / Q000378:metabolism; D005994:Glycerophosphates / Q000494:pharmacology; D046529:Microscopy, Electron, Transmission / Q000379:methods; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D011506:Proteins / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017550:Spectroscopy, Fourier Transform Infrared; D017356:Synchrotrons; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D002130:Calcium Phosphates; D005994:Glycerophosphates; D011506:Proteins; C022045:octacalcium phosphate; D017886:Durapatite; C494366:calcium phosphate, dibasic, dihydrate; C031463:beta-glycerophosphoric acid
keywords: Dicalcium phosphate dehydrate; Mineralization; Octacalcium phosphate; Osteoblasts