Caspase 9-induced apoptosis for efficient fetal cell ablation and disease modeling
Animal models for targeted cell ablation are invaluable in the field of biology and medicine. Specifically, fetal targeted cell ablation has the potential for organ regeneration and xenotransplantation. Previous methods involve conventional knockout models, which offers limited control over severity, or conditional ablation models, which use inducers that are harmful to fetuses. In this study, we apply the inducible caspase 9 (iC9) system to target mouse fetal nephron progenitor cells. It triggers specific, rapid, and efficient target cell ablation through the intrinsic apoptosis pathway by the administration of a safe, placental-permeable inducer. This feature allowed for precise adjustment of severity based on the timing of administration, enabling the creation of a viable severe kidney failure model. We also demonstrate that cells with low iC9 expression levels and those in the solid organ state are less susceptible to apoptosis induction. RNA-seq of wild type mouse fetal kidneys revealed that DNA damage response is enhanced after dissociation, suggesting that it is the underlying mechanism for the reduced susceptibility to apoptosis in solid-state cells compared to single-cell states. Apoptosis can still be triggered in these conditions by the combined inhibition of X-linked inhibitor of apoptosis protein. This approach will not only facilitate the study of mechanisms involved in induced cell death but also enhance its utility as a research tool, including for fetal organ transplantation models. Overall design: We hypothesized that the single-cell state exhibits enhanced susceptibility to apoptosis. To investigate how gene expression related to apoptosis susceptibility differs before and after single-cell dissociation in fetal kidneys, we analyzed the transcriptomes between untreated wild-type fetal kidneys (pre-dissociation) and those enzymatically and manually dissociated into single-cell suspensions (post-dissociation) by bulk RNA-sequencing (n = 3 vs. 3).