Use of a calcium tracer to detect stone increments in a rat calcium oxalate xenoplantation model

The majority of urinary stones have been observed to grow by circular increments in the clinic and in animal studies. However, the mechanism of stone formation has not yet been elucidated. Marking the stone at specific time-points during the growth of the stone is likely to enable the clarification of the mechanisms behind lithogenesis. The objective of this study was to evaluate the role and efficacy of calcium-tracing fluorescence in the labeling of stone lamination in a rat calcium oxalate xenoplantation model. In the rat calcium oxalate xenoplantation model, human renal stone particles, extracted by percutaneous nephrolithotomy, were xenoplanted into the bladders of Wistar rats in a sterile manner. The rats received 1% ethylene glycol in their drinking water, starting from the day following the stone xenoplantation. Two weeks subsequent to this, three calcium-tracing fluorochromes, alizarin complexone, calcein and xylenol orange were administered by intraperitoneal injection. The newly-formed bladder stones were cut into slices and examined using light and fluorescence microscopy. The newly-formed bladder stones had a large variance in size, and circular increments were observed in the sections of the stones. The stones were successfully labeled with calcein and alizarin complexone, although calcein labeling provided superior results. However, the use of xylenol orange did not result in clear labeling. The calcium-tracing fluorochromes, calcein and alizarin complexone may be effectively used to label stone lamination in rat models.