A red herring in vascular calcification: 'nanobacteria' are protein-mineral complexes involved in biomineralization - PubMed (original) (raw)

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A red herring in vascular calcification: 'nanobacteria' are protein-mineral complexes involved in biomineralization

Georg Schlieper et al. Nephrol Dial Transplant. 2011 Nov.

Abstract

Biomineralization at pathological extraosseous sites (i.e. vasculature and soft tissues) is associated with increased morbidity and mortality. So-called 'nanobacteria' have been described as pathogenic agents causing many diseases including calcification. Initially, their appearance, and having a content consisting of nucleic acids plus proteins and properties of growing structures, suggested that they were living organisms. However, it could be demonstrated that the so-called nanobacteria were in fact mineralizing nanoparticles that contain mineral and non-mineral compounds, that these particles bind to charged molecules and that supersaturation enables in vitro growth of these nanoparticles. Recent data indicate that nanoparticles consisting of protein-mineral complexes can be seen both in vitro and in vivo as precursors of matrix calcification.

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Figures

Fig. 1.

Fig. 1.

Transmission electron micrograph of so-called ‘nanobacteria’ after a 3-month culture period (bar = 200 nm). Photograph taken with permission from [6] (copyright 1998 National Academy of Sciences, USA).

Fig. 2.

Fig. 2.

Illustration of a CPP, calciprotein monomer (modified after [18, 19]) and a low-density lipoprotein (LDL) particle. The LDL particle is ∼22 nm in diameter and contains many esterified cholesterol molecules in the hydrophobic core, cholesterol, phospholipids and a few apolipoprotein B-100 molecules in the hydrophilic coat (modified after [20]).

Fig. 3.

Fig. 3.

Electron microscopic picture of synthetic CCPs [22]. The CCPs initially have a diameter of 30–150 nm (2 h, 37°C) and are amorphous as shown by diffraction analysis. Nextly, the CPPs are transformed, dependent on temperature, mineral ion supersaturation and fetuin-A concentration, into larger and crystalline mineral particles [23]. These particles are still soluble until ∼24 h at 37°C. Similar particles have been detected in ascites of patients with sclerosing calcifying peritonitis [24]. Scale bars represents 100 nm. This research was originally published in [22] © the American Society for Biochemistry and Molecular Biology.

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