Functional development of a transplanted embryonic kidney: effect of transplantation site

Abstract

A xenotransplanted metanephros may undergo complete nephrogenesis in the host animal, forming a functional kidney. This suggests that, in future, xenometanephroi could become an unlimited source of material for renal transplantation. Although the omentum (OM) is the primary site for transplantation, we speculated that the growth of the transplant could differ depending on the site of transplantation. Thus, we determined the optimal transplantation site for the metanephros in terms of retaining its ability to produce renin and erythropoietin (EPO). Rat metanephroi were transplanted into the OM, paraaortic area (PA), or both (OM+PA) of unilaterally nephrectomized host rats. After 2-3 weeks, blood was rapidly withdrawn in order to induce production of renin and EPO in the transplants. Histological analysis indicated that transplants in both the PA and OM were well differentiated, demonstrating polarity of the medulla through to the cortex. Plasma renin activity (PRA) increased in response to the induction procedure, but transplants in the PA expressed PRA more effectively than did those in the OM. Real-time polymerase chain reaction (PCR) revealed higher levels of renin mRNA expression in transplants in the PA than in those in the OM. Although EPO production increased 24 hours after the induction procedure, the levels did not differ significantly between OM- and PA-transplanted rats. Compared with transplantation to the OM, transplantation of rat metanephroi to the PA results in better renin production, whereas the transplantation site does not affect EPO production.