Pregnancy after allogeneic uterus transplantation in the rat: perinatal outcome and growth trajectory.

To investigate whether allogeneic uterine grafts in a rat model, with tacrolimus immunosuppression, can harbor pregnancies that result in offspring with normal postnatal growth. Experimental animal study. University hospital. Lewis rats as uterus donors and Piebald-Virol-Glaxo rats as recipients. Animals were allocated to one of the following three groups: allogeneic uterus transplantation with end-to-side anastomosis to the external iliac vessels and immunosuppression with tacrolimus (UT+Tac; n = 10); sham surgery and immunosuppression with tacrolimus (Sham+Tac; n = 10); or sham surgery (Sham; n = 10). The rats were subsequently introduced to male rats with proven fertility and in the event of resulting pregnancy cesarean sections were performed on day 22 of pregnancy. Graft viability, fertility rate, perinatal death, birth weight, postnatal birth trajectory. Pregnancy rate was higher in the control groups (70% Sham and 80% Sham+Tac) than in the transplanted group (50% UT+Tac), although these differences did not reach the significance threshold. There were no differences between groups regarding number of living pups or neonatal deaths. Pups born from UT+Tac mothers had birth weights similar to external control animals from our breeding colony (BC): UT+Tac males 6.2 ± 0.2 g, UT+Tac females 5.5 ± 0.6 g, BC males 5.8 ± 0.2 g, BC females 5.2 ± 0.3 g; n.s. Evaluation of uteri and placentas of pregnant animals revealed a somewhat reduced vascular density in both tissues in the UT+Tac group, and that was not seen in the Sham+Tac group. Allogeneic uterus transplantation and immunosuppression with tacrolimus is compatible with normal pregnancy and perinatal outcome in a rat model.