[Organogenesis of developing metanephroi allografted into nonimmunosuppressed adult rats]

To explore novel methods of possible donor organ supply and immunologic tolerance induction of organ transplantation.

Whole metanephroi from d14-19 (E14-E19) embryos of pregnant rats were grouped and allografted into the omenta or near remnants of renal vessels of nonimmunosupressed adult rats. At the time of implantation, host rats underwent unilateral nephrectomy. Four weeks after implantation, allografted metanephroi in host rats were removed for gross, biochemical and histopathological examination.

Four weeks post-implantation, (1) E19 and E18 metanephroi had enlarged,but were replaced by connective tissues. (2) E17 and E16 metanephroi showed the signs of acute rejection such as hypercellular glomeruli and lymphocyte infiltration in peritubular spaces. E16 grafted metanephroi underwent mild acute rejection of Banff schema, while E17 had moderate or severe acute rejection. When Cyclosporine A was administrated, E17 metanephroi formed mature nephrons and collecting ducts with few lymphocyte infiltration. (3) Metanephroi from E15 and E14 embryos allografted into the omentum or near remnants of renal vessels of uninephrectomized adult rats were enlarged and vascularized, and formed mature tubules and glomeruli. (4) The concentrations of urea nitrogen and creatinine in cyst fluid of E15 and E16 metanephroi were increased 40-fold and 50-fold, which were comparable to those in bladder urine. (5) In contrast, rat metanephroi did not grow or differentiate in rats without host kidney resection.

E14 and E15 metanephroi allografted into nonimmunosuppressed adult rats or E17 into cyclosporine-treated hosts undergo growth and differentiation and become vascularized. A variety of factors affect the growth and development of allografted metanephroi, while rejection is the main one.