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Sci Rep. 2018 Jan 19;8(1):1256. doi: 10.1038/s41598-018-19677-4.

Identification and quantification of plasma calciprotein particles with distinct physical properties in patients with chronic kidney disease.

Author information

1
Division of Anti-Ageing Medicine, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
2
Department of Clinical Laboratory Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
3
Division of Nephrology, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
4
Division of Community and Family Medicine, Center for Community Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan.
5
Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
6
Division of Anti-Ageing Medicine, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan. mkuroo@jichi.ac.jp.
7
AMED-CREST, Japan Agency for Medical Research and Development, Tokyo, Japan. mkuroo@jichi.ac.jp.

Abstract

Calciprotein particles (CPP) are solid-phase calcium-phosphate bound to serum protein fetuin-A and dispersed as colloids in the blood. Recent clinical studies indicated that serum CPP levels were increased with decline of renal function and associated with inflammation and vascular calcification. However, CPP assays used in these studies measured only a part of CPP over a certain particle size and density. Here we show that such CPP are mostly artifacts generated during processing of serum samples in vitro. The native CPP in fresh plasma are smaller in size and lower in density than those artifactual CPP, composed of fetuin-A carrying amorphous and/or crystalline calcium-phosphate, and increased primarily with serum phosphate levels. We have identified several physicochemical factors that promote aggregation/dissolution of CPP and transition of the calcium-phosphate from the amorphous phase to the crystalline phase in vitro, including addition of anti-coagulants, composition of buffer for sample dilution, the number of freeze-thaw cycles, the speed for sample freezing, and how many hours the samples were left at what temperature. Therefore, it is of critical importance to standardize these factors during sample preparation in clinical studies on CPP and to investigate the biological activity of the native CPP.

PMID:
29352150
PMCID:
PMC5775250
DOI:
10.1038/s41598-018-19677-4
[Indexed for MEDLINE]
Free PMC Article

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