6533b7d3fe1ef96bd1260b33

RESEARCH PRODUCT

Direct nucleation of calcium oxalate dihydrate crystals onto the surface of living renal epithelial cells in culture

subject

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Direct nucleation of calcium oxalate dihydrate crystals onto the surface of living renal epithelial cells in culture. Background. The interaction of the most common crystal in human urine, calcium oxalate dihydrate (COD), with the surface of monkey renal epithelial cells (BSC-1 line) was studied to identify initiating events in kidney stone formation. Methods. To determine if COD crystals could nucleate directly onto the apical cell surface, a novel technique utilizing vapor diffusion of oxalic acid was employed. Cells were grown to confluence in the inner four wells of 24-well plates. At the start of each experiment, diethyloxalate in water was placed into eight adjacent wells, and the plates were sealed tightly with tape so that oxalic acid vapor diffused into a calcium-containing buffer over- lying the cells. Results. Small crystals were visualized on the cell surface after two hours, and by six hours the unambiguous habitus of COD was confirmed. Nucleation onto cells occurred almost exclusively via the (001) face, one that is only rarely observed when COD crystals nucleate onto inanimate surfaces. Similar results were obtained when canine renal epithelial cells (MDCK line) were used as a substrate for nucleation. Initially, COD crystals were internalized almost as quickly as they formed on the apical cell surface. Conclusions. Face-specific COD crystal nucleation onto the apical surface of living renal epithelial cells followed by internal- ization is a heretofore unrecognized physiological event, suggest- ing a new mechanism to explain crystal retention within the nephron, and perhaps kidney stone formation when this process is dysregulated or overwhelmed.