Transplantation of rat metanephroi into mice

To determine whether transplanted metanephroi grow and differentiate after implantation into the omentum in hosts of a different species, we implanted metanephroi from embryonic day 15 (E15) rat embryos into uninephrectomized mice (hosts). Some host mice received human CTLA4Ig (hCTLA4Ig), anti-CD45R B, and anti-CD154 (tolerance-inducing agents). E15 metanephroi contained on ly metanephric blastema, segments of ureteric bud, and primitive nephrons w ith no glomeruli. Rat metanephroi did not grow or differentiate in mice tha t received no tolerance-inducing agents. However, by 2 wk posttransplantati on in mice that received hCTLA4Ig, anti-CD45RB, and anti-CD154, metanephroi from E15 rats had enlarged, become vascularized, and formed mature tubules and glomeruli. Rat metanephroi contained cells that stained specifically f or mouse CD31, a marker for sprouting endothelial cells. Some rat glomerula r capillary loops stained positively for mouse CD31. Here, we show that chi meric kidneys develop from metanephroi transplanted rat-->mouse and that gl omeruli are vascularized, at least in part, by host vessels.