Species differences in uroepithelium-induced bone development: observations on transplants of human uroepithelium in cortisone-treated mice.

Specimens (2-3 x 3-5 mm) of human urinary tract mucosa from bladder (67 cases), ureter and renal pelvis (35 cases) were implanted intramuscularly into cortisone-treated mice in order to elucidate whether human urothelium has the potency to induce osteogenesis. Although xenogeneic epithelium survived up to 14 days after implantation, in none of the 300 implants performed was a bone or cartilage induction observed. Implantation of urinary bladder mucosa from guinea pig and dog resulted in a heterotopic bone and cartilage formation in the graft's vicinity in 28 of 39 cases. The survival of animal transitional epithelium was similar to that of human. It is concluded that human transitional epithelium does not possess osteoinductive potency. Some clinical data pointing to a link between heterotopic osteogenesis and surgical intervention on urinary tract have been reconsidered and explained by the authors' own hypothesis. In addition, data presented in this paper indicate that one should be very careful when attempting to transmit results performed on dog urinary tract to humans.