(A) H&E staining and Ki67 immunostaining of the recipient mouse uteri on day 4 of pregnancy. Normal proliferation-differentiation switching during implantation, a marker of uterine receptivity, was observed in the transplanted decellularized uterine matrix (DUM), indicating the normal capacity for embryo implantation in the regenerated uterus. WT recipient mice 1 month after decellularized matrix transplantation were crossed with fertile WT males. Scale bar: 200 μm. UT, a recipient uterus surrounding DUM; dotted line, a boundary between DUM and UT. Each image is a representative from at least 3 independent experiments. (B) A macroscopic image of an implantation site at the transplanted DUM site on day 19 of pregnancy. To assess pregnancy outcome of WT recipient mice, cesarean section was performed on day 19 of pregnancy. The reconstructed uterus within the transplanted DUM site showed normal appearance and looked like a pregnant uterus on day 19. Yellow arrow, a 10-0 nylon suture thread. Scale bar: 2 mm. (C) Numbers of implantation sites in the surgical and nonsurgical horns in the pregnant recipient mice on day 19 of pregnancy. Numbers of implantation sites in the pregnant recipient mice were comparable between the surgical and nonsurgical horns. (D) A macroscopic image of pups in the surgical and nonsurgical horns of the same recipient mouse delivered by cesarean section on day 19 of pregnancy. Size and general appearance of pups at the transplanted DUM sites were similar to those of pups at the nonsurgical site as well as those of pups in the surgical horns. (E) Weight of pups that developed at the surgical site, the nonsurgical site in the surgical horn, and the nonsurgical horn on day 19 of pregnancy. The weight of pups that developed at the transplanted DUM sites were similar to those of pups that developed at the nonsurgical site as well as those of pups that developed in the surgical horns, indicating that regenerated uterine capacity was normal and could maintain full pregnancy.