Developmental Biology

Congenital renal disorders, such as the Potter sequence, result from renal dysgenesis. To explore a prenatal therapeutic approach for fetuses with kidney insufficiency, we established an in utero transplantation protocol using donor fetal kidneys. Although numerous rodent studies have reported cellular injections into fetal recipients, no protocol to date has described whole-organ transplantation during gestation. Here, we present a step-by-step method for grafting donor fetal kidneys (embryonic day 14.0–16.5) into allogeneic rat fetuses at embryonic day 18.0–18.5, resulting in term neonates that retain the grafts postnatally. A 15–16 G needle preloaded with the donor kidney is inserted transuterinely, depositing the organ into the subcutaneous space of the fetus. Four days later, the term pups are delivered naturally and evaluated for graft development. This protocol enables organ-level transplantation and longitudinal assessment of graft maturation within the unique fetal environment, which differs markedly from adult settings in terms of growth factor availability and immune reactivity. To our knowledge, this is the first protocol to successfully achieve whole-organ transplantation directly into fetuses in utero. Therefore, the model provides a valuable platform for studying developmental organogenesis, fetal immunology, and regenerative strategies that leverage embryonic cues.

Primary cilia are evolutionarily conserved organelles that play critical roles in brain development. In the developing cortex, neural progenitors extend their primary cilia into the ventricular surface, where the cilia act as key signaling hubs. However, visualizing these cilia in a systematic and intact manner has been challenging. The commonly used cryostat sectioning only provides a limited snapshot of cilia on individual sections, and this process often disrupts the ciliary morphology. By contrast, the previously established whole-mount technique has been shown to preserve ciliary architecture in the adult mouse cortex. Here, we adapt and optimize the whole-mount approach for embryonic and neonatal brain, allowing robust visualization of ciliary morphology at the ventricular surface during development. This protocol describes step-by-step procedures for whole-mounting and immunostaining delicate embryonic and neonatal mouse cortices, enabling direct visualization of cilia in neural progenitors in the developing brain.