Differential bound proteins and adhesive capabilities of calcium oxalate monohydrate crystals with various sizes

yyAdhesion of calciumoxalate (CaOx) crystals onto renal tubular epithelial cells is one of the critical steps in kidney stone formation. However, effects of crystal size on the crystal adhesive capability remained unclear. This study compared the adhesive capabilities of CaOxmonohydrate (COM) crystalswith various sizes (<10 mu m, 20-30 mu m, 50-60 mu m, and > 80 mu m). Crystal-cell adhesion assay showed size-dependent increase of COM crystal adhesion onto epithelial cell surface using the larger crystals. Identification of apical membrane proteins that could bind to COM crystals by tandem mass spectrometry (nanoLC-ESI-ETD MS/MS) demonstrated size-specific sets of the COMcrystal-binding proteins. Among these, numbers of known oxalate-binding proteins and COM crystal receptorswere greatest in the set of the largest size (>80 mu m). Atomic force microscopy (AFM) revealed that adhesive forces between carboxylic-immobilized AFM tip and COMcrystal surface and between COM-mounted AFM tip and renal epithelial cell surface were size-dependent (greater for the larger crystals). In summary, the adhesive capability of COMcrystals is size-dependent - the larger the greater adhesive capability. These data may help better understanding of the pathogenic mechanisms of kidney stone formation at an initial stage when renal tubular cells are exposed to various sizes of COM crystals. (C) 2020 Elsevier B.V. All rights reserved.