journal club

Animal models enabling precise cell or tissue ablation represent crucial tools for investigating developmental biology, organ regeneration, and disease pathophysiology.Current models, such as knockout and conditional ablation systems, are often limited by lack of temporal and dosage control or involve inducers (e.g., tamoxifen or doxycycline), leading to undesired toxicity.Importantly, a reliable mouse model to investigate the physiological effects of reduced nephron numbers in kidney injury models has been notably absent.Matsui et al. introduce a novel inducible caspase 9 (iC9) mouse model that allows targeted ablation of fetal nephron progenitor cells (NPCs) with high precision, efficiency, and safety.This model represents a novel approach to studying the impact of reduced nephron numbers on blood pressure regulation and other complex physiological renal parameters.In this study, Matsui et al. generated Six2-driven iC9 knock-in mouse models, selectively expressing iC9 in NPCs.Administration of a placenta-permeable chemical inducer of dimerization (CID) triggered caspase 9 activation, initiating rapid apoptosis of NPCs.Importantly, CID demonstrated no toxicity to untreated fetuses or mothers, providing significant advantages over traditional tamoxifen-induced ablation systems.The authors demonstrated that the timing of CID administration allowed precise control over disease severity, ranging from congenital kidney deficiency to severe chronic kidney disease (CKD).Early administration (embryonic day 11.5 [E11.5])led to neonatal lethality, whereas later administration (E13.5)produced viable offspring with severe CKD, characterized by glomerular sclerosis, interstitial fibrosis, and macrophage infiltration.The effectiveness of the system correlated with the level of iC9 expression.NPC ablation was less effective in heterozygous mice with lower iC9 expression, but this limitation was overcome by combining CID administration with an inhibitor of X-linked inhibitor of apoptosis protein.Additionally, the authors established interspecies chimeric kidneys using rat and human NPCs injected into ablated mouse NPC niches, demonstrating successful nephron replacement and differentiation in vivo, which represents another exciting approach of this mouse model (Figure 1).This study represents a significant advancement in animal models for kidney disease research, enabling accurate modeling of fetal nephron loss and CKD progression, and it can be used as a model for fetal organ complementation