Effects of osteopontin on hypercalciuria-induced attachment of calcium oxalate crystals to rat renal epithelial cells

Abstract

Objective To address the effects of osteopontin (OPN) on hypercalciuria contributing to the kidney stone formation.Methods The normal rat kidney epithelial cell line NRK cells were divided into three groups,which were cultured in the medium containing calcium of 0.1,0.3 and 0.6 g/L,respectively.The cell proliferation,the content of OPN in the cell culture supernatants and the level of OPN gene expression at 3,6 and 24 h were examined.The lentivirus vector targeting OPN was constructed.The NRK cells were infected with the lentivirus and then cultured in the medium containing calcium of 0.6 g/L for 24 h.Eventually,The inhibitory effects of silencing OPN gene on the adhesion of calcium oxalate crystals to NRK cells were investigated.Results High level calcium could significantly suppress the proliferation of NRK cells and stimulate secretion of OPN as compared with the blank control group (P ＜ 0.05).The expression of OPN mRNA and protein was also significantly increased (P ＜ 0.05).Calcium concentrations of the lysate of infected NRK cells in the three groups after calcium chloride stimulation were (19.25 ±3.71),(27.22 ±3.82) and (31.91 ± 1.15) mg/L,respectively.The silencing of OPN gene expression could significantly inhibit the abilities of attachment of calcium oxalate crystals to NRK cells as compared with negative lentivirus vector and blank control group,respectively (P ＜ 0.05).Conclusion High level calcium could induce the adhesion of calcium oxalate crystals to NRK cells probably mediated by OPN. Key words: Hypercalciuria ; Osteopontin; Renal epithelial cell