Presentation Authors: Jennifer Bjazevic*, Kaitlin F. Al, Jaswanth Gorla, Hassan Razvi, Jeremy P. Burton, LONDON, Canada
Introduction: There is growing evidence to support a role of urinary bacteria in the development of calcium stone disease; however, the mechanisms by which urinary bacteria may influence calcium stone formation remain to be elucidated. Both osteopontin (OPN) and zinc (Zn) have been shown to play a role in calcium oxalate (CaOx) urolithiasis and have also been demonstrated to be involved in bacterial pathogenesis. We aimed to examine the effect of non-urease producing bacteria isolated from a urinary tract infection, as well as both OPN and Zn, on the adherence of calcium oxalate crystals to renal epithelial cells.
Methods: HEK293 and MDCK renal epithelial cells were grown to 90% confluence on culture plates. Cells were exposed to a non-urease producing strain of Escherichia coli (UTI89) for 20 minutes at 37C (103 CFU). The cells were then incubated with CaOx crystal suspension (0.5mg/mL) in artificial urine with or without the addition of OPN (0.1 Î¼g/ml) or zinc chloride (500 Î¼g/L), for 20 minutes at 37C. Unattached crystals were washed free with culture media. The adherence of calcium oxalate crystals was determined with birefringence microscopy and quantified by pixel intensity with MatLab.
Results: Microscopy following treatment exposure revealed live cells in all treatment groups, and bacterial rods visible in groups treated with UTI89. In the MDCK cells, exposure to UTI89 significantly increased crystal adherence (p < 0.001, FIgure 1). Exposure to OPN and Zn were noted to have opposite effects in UTI89 treated cells, resulting in attenuated and enhanced crystal adherence respectively (p < 0.001, Figure 1). Similar trends were observed in the HEK293 cells; however, these results did not reach statistical significance.
Conclusions: These findings suggest that non-urease producing E. coli impacts CaOx crystal adherence, and both Zn and OPN may have a novel role in this process. While Zn and OPN have previously been shown to be involved in both CaOx urolithiasis and bacterial pathogenesis; further investigation is required in order to delineate the potential mechanisms by which urinary pathogens alter crystal adherence, and the precise role that both Zn and OPN may play in this process.
Source of Funding: AUA Urology Care Foundation Research Scholar Award