Is heterotopic bone formation, occurring near a cut ureter, a sign of osteoinductive potency of human urothelium?

Urine is a highly cytotoxic agent: does it influence stem cell therapies in urology?

The state of art of stem cell therapies in urologic regenerative medicine is still under development. There are still many issues before advances in tissue engineering can be introduced for clinical application. The essential question is whether stem cells should be seeded on the urinary tract lumen side. The present experiment, using Real-Time Cell Analyzer (RTCA) DP (Dual Plate) of the xCellligence system (Roche Applied Science, Mannheim, Germany), allowed us to monitor cellular events in real time. In this study we examined the influence of urine on bone marrow-derived mesenchymal stem cells (MSC). Cells were exposed to medium mixed with urine (1:1), medium mix with PBS (Phosphate Buffered Saline) (1:1), only urine, and whole medium without cells as background. The cell number was significantly lower in all groups exposed on medium mixed with urine and urine alone. The results showed that urine is a highly cytotoxic agent whose role in urologic regenerative medicine is underestimated.

[Bone formation in the ureter. Osseous metaplasia of an obstructed ureter]

Bone formation outside the skeleton is well known. Yet, ossification within the urogenital tract is rare. The case of a patient with distal ureteral obstruction, hydronephrosis, and subsequent circular osseous metaplasia of the ureter is presented. Open transperitoneal right-sided nephrectomy with partial resection of the ureter was performed. Intraoperatively and in histopathologic examination circular bone formation adjacent to the ureteral wall was detected. There was no evidence of malignancy. Early animal experiments in the twentieth century showed that bone metaplasia may be induced by epithelium of the urinary tract under certain conditions such as ischemia, inflammation, necrosis, sclerosis, and trauma. Osseous metaplasia may therefore be considered a differential diagnosis of calcification of the upper urinary tract in the absence of urolithiasis.

Ureteral obstruction after kidney transplantation secondary to bone metaplasia

We report a case of ureteral obstruction after kidney transplantation caused by localized bone metaplasia in the donor ureter. Surgical treatment consisted of removal of the involved ureteral segment, which was located 3 cm above the bladder and creation of a spatulated end-to-end anastomosis. Although bone metaplasia has been observed in the ureteral wall of some animal species secondary to experimental ischemia and microtrauma, it is exceedingly rare in humans and has never before been documented after kidney transplantation.