Transplantation of metanephroi after preservation in vitro.

To determine whether transplanted metanephroi grow, differentiate, and function in hosts after preservation in vitro, we implanted metanephroi from embryonic day 15 (E15) Sprague-Dawley rat embryos into the omentum of nonimmunosuppressed uninephrectomized Sprague-Dawley (host) rats. Metanephroi were either implanted directly or suspended in ice-cold University of Wisconsin (UW) preservation solution with or without added growth factors for 3 days before implantation. The size and extent of tissue differentiation preimplantation of E15 metanephroi implanted directly were not distinguishable from the size and differentiation of metanephroi preserved for 3 days. In contrast, E16 metanephroi were larger than E15 metanephroi preserved for 3 days. E16 metanephroi or E13 metanephroi grown in organ culture for 3 days contained more differentiated nephron structures than those in E15 metanephroi preserved for 3 days. By 4 wk posttransplantation, metanephroi that had been preserved for 3 days had grown and differentiated such that glomeruli, proximal and distal tubules, and collecting ducts with normal structure had developed. At 12 wk posttransplantation, inulin clearances of preserved metanephroi were comparable to those of metanephroi that had been implanted directly. Addition of growth factors to the UW solution enhanced inulin clearances. Here we show for the first time that functional kidneys develop from metanephroi transplanted from rat embryos to adult rats after as long as 3 days of preservation in vitro.