Crystal adhesion and internalization of sub-micron COM and COD crystals on Human kidney proximal tubular epithelial cells

[Objective] This study aims to compare the internalization of sub-micron calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) crystals in human kidney proximal tubular epi-thelial cells (HKC) so as to explore the mechanism of renal epithelial cell injury caused by urine calcium oxalate crystals. [Methods] Cell viability, malondialdehyde (MDA) content, and propidium iodide (PI) staining were determined to examine cell injury during adhesion. The internalization of COM and COD crystals to HKC cells was observed through scanning electron microscopy. [Results] The injury effect of COM was stronger than that of COD on cells under the same conditions. Both of them injured HKC in a dose-dependent manner. The ability of COM to adhere to the injured HKC cells was higher than that of COD crystals. Compared to the COD group, the crystal adhered on cell surface appeared obvious aggregation in COM treatment group. [Conclusions] Cytotoxicity of sub-micron COM was greater than sub-micron COD. The attached COM crystals aggregated on cell surface. HKC cells swallow COD crystals more easily than COM. These findings provide further insights into kidney stone formation.