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Abstract: SA-PO344

Development of a System for the Replacement of Animal Fetal Kidneys with Human Nephrons: Toward Clinical Application

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 600 Development, Stem Cells, and Regenerative Medicine


  • Matsui, Kenji, Tokyo Jikeikai Ika Daigaku, Minato-ku, Tokyo, Japan
  • Yamanaka, Shuichiro, Tokyo Jikeikai Ika Daigaku, Minato-ku, Tokyo, Japan
  • Kobayashi, Eiji, Tokyo Jikeikai Ika Daigaku, Minato-ku, Tokyo, Japan
  • Yokoo, Takashi, Tokyo Jikeikai Ika Daigaku, Minato-ku, Tokyo, Japan

Our focus is on "xenogeneic regenerative medicine," aiming to regenerate human nephrons using porcine fetal kidneys as a scaffold. Crucial to this approach is the replacement of porcine nephron progenitor cells (NPCs) with human NPCs. Previous studies using mouse models have shown complete replacement of the host nephrogenic niche with exogenous nephrons through Six2 (+) NPC suicide driven by diphtheria toxin (DT) or tamoxifen (TAM). However, there are limitations, such as DT's inability to target human NPCs and concerns about TAM's side effects. To facilitate future clinical applications, we have developed a novel inducible-caspase 9 (iCasp9) system. It activates the intrinsic apoptotic pathway upon the administration of a chemical inducer of dimerization (CID) without harming the surrounding renal tissue. Importantly, our study demonstrates efficient cell clearance using this new system in animal models.


Six2-iCasp9 mice were generated using TALEN-mediated gene modification. The knock-in site was positioned downstream of the exon to prevent lethality in homozygotes. CID was administered both in vitro to fetal kidneys and in vivo to neonatal mice with either Six2-iCasp9+/+ or Six2-iCasp9+/- genotype. Additionally, exogenous mouse and rat progenitor cells, as well as induced human NPCs, were injected into Six2-iCasp9+/+ fetal kidneys with CID administration.


In the culture of Six2-iCasp9+/+ fetal kidneys, treatment with CID induced efficient apoptosis of all NPCs within 18 hours, whereas the conventional TAM-driven model showed insufficient apoptosis at the same time point. In vivo administration of CID to neonates also led to the complete removal of NPCs. On the other hand, NPC removal was not observed in the Six2-iCasp9+/- mice.
Following the injection of exogenous progenitor cells, successful nephron replacement was achieved in Six2-iCasp9+/+ fetal kidneys.


We successfully developed an iCasp9 system that enables rapid and complete cell clearance, providing an optimal environment for NPC replacement and subsequent nephron regeneration in an animal model. The phenotypic differences between homozygotes and heterozygotes might be attributed to the varying levels of iCasp9 expression. This achievement marks a clinical advancement in the development of the porcine fetal replacement system.


  • Government Support – Non-U.S.