Transplantation of metanephroi after preservation in vitro

To determine whether transplanted metanephroi grow, differentiate, and func tion in hosts after preservation in vitro, we implanted metanephroi from em bryonic day 15 (E15) Sprague-Dawley rat embryos into the omentum of nonimmu nosuppressed 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 preimpl antation of E15 metanephroi implanted directly were not distinguishable fro m the size and differentiation of metanephroi preserved for 3 days. In cont rast, E16 metanephroi were larger than E15 metanephroi preserved for 3 days . E16 metanephroi or E13 metanephroi grown in organ culture for 3 days cont ained more differentiated nephron structures than those in E15 metanephroi preserved for 3 days. By 4 wk posttransplantation, metanephroi that had bee n preserved for 3 days had grown and differentiated such that glomeruli, pr oximal and distal tubules, and collecting ducts with normal structure had d eveloped. At 12 wk posttransplantation, inulin clearances of preserved meta nephroi were comparable to those of metanephroi that had been implanted dir ectly. Addition of growth factors to the UW solution enhanced inulin cleara nces. 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.