Crystal Surface Adhesion Explains the Pathological Activity of Calcium Oxalate Hydrates in Kidney Stone Formation

Abstract

Renal tubular fluid in the distal nephron of the kidney is supersaturated with calcium oxalate (CaOx), which crystallizes in the tubules as either calcium oxalate monohydrate (COM) or calcium oxalate dihydrate (COD). Kidney stones are aggregates, most commonly containing microcrystals of COM as the primary inorganic constituent. Stones also contain small amounts of embedded proteins, which are thought to play an adhesive role in these aggregates, and they often are found attached to the tip of renal papilla, presumably through adhesive contacts. Voided urine, however, often contains COD in the form of single micron-sized crystals. This suggests that COD formation protects against stone disease because of its reduced capacity to form stable aggregates and strong adhesion contacts to renal epithelial cells. Using atomic force microscopy configured with tips modified with biologically relevant functional groups, we have compared the adhesion strengths of the morphologically important faces of COM and COD. These measurements provide direct experimental evidence, at the near molecular level, for poorer adhesion at COD crystal faces, which explains the benign character of COD and has implications for resolving one of the mysteries of kidney stone formation.

Antiurolithiatic Activity of Daucus carota: An In vitro Study

“…Therefore, of the two polymorphs, COM significantly promotes crystal retention and eventual stone formation. 17 Therefore, a transformation from COM to COD is advocated as a crucial step in inhibition of calculi formation. 16 In present study, DCRE also promoted transformation of pointy edged dendritic COM crystals to smoother edged COD crystals of extremely reduced size and number.…”

Kinetic study of dehydration of calcium oxalate trihydrate

“…The most frequently published data on calcium oxalate describe the crystal growth (conditions and kinetics) [3,[9][10][11][12][13][14][15][16][17][18] and dissolution of hydrates [19][20][21][22]. The crystallization of COM has been the subject of physico-chemical and biological analyses [23,24]. Recently a  pavla.honcova@upce.cz; tel.…”

Phyllanthus niruri as a promising alternative treatment for nephrolithiasis

“…CaOx crystals are found in urine under several forms including monohydrate (COM) and dihydrate (COD) forms. Unlike COD, which is predominantly found in normal individuals, COM crystals have higher capacity to aggregate and adhere, and is the main form excreted by the nephrolithiasis patients (26)(27)(28). In the model of in vitro precipitation of CaOx using human urine from healthy individuals, Phyllanthus niruri induced an increase in COD forms and reduced the amount of COM crystals, responsible for higher potential risk for stone formation.…”