Lineage tracing reveals KSP+ cells as multipotent progenitors driving postnatal renal development and injury repair via notch signaling.

BACKGROUND: Progenitor cells generate multiple cells during development and are thought to be involved in tissue repair. The widespread distribution of Kidney-specific cadherin-positive (KSP+) cells in the kidney suggests they play an important role in renal development. However, direct evidence demonstrating that KSP+ cells function as progenitor cells contributing to renal development and repair is lacking. METHODS: To obtain direct evidence for the differentiation and regenerative potential of KSP+ cells, we performed in vivo lineage tracing using Ksp-Cre and Rosa-LSL-tdTomato (RFP f/f ) transgenic mice, combined with thymidine analog (5-chloro-2'-deoxyuridine, CldU) labeling in adult wild-type (WT) mice. Lineage tracing was analyzed from embryonic day 14.5 (E14.5) to adulthood by triple immunofluorescence staining for KSP, red fluorescent protein (RFP), and nephron segment-specific markers. Unilateral ureteral obstruction (UUO) was performed to investigate the regenerative potential of KSP+ cells following renal injury. Proliferative capacity was assessed by CldU/Ki67/PCNA labeling from days 2-14 post-surgery. To explore the molecular mechanism potentially underlying KSP+ cell-mediated repair, we analyzed Notch signaling pathway in UUO-subjected WT mice. RESULTS: The Ksp-Cre: RFP f/f lineage-tracing model exhibited high efficiency and specificity, with RFP expression strictly confined to KSP+ cells at E14.5. Lineage tracing revealed that embryonic KSP + cells function as progenitor cells, giving rise to cells in the formation of multiple nephron segments, including proximal tubules (PTs), loops of Henle (HLs), distal convoluted tubules (DCTs), and collecting ducts (CDs) during kidney development. Comparison of the differentiation capacity of KSP+ cells during embryonic versus postnatal development indicated that KSP+ cells preferentially contribute to postnatal kidney development. In adult kidneys under homeostatic conditions, KSP + cells showed limited proliferative potential. However, following UUO injury, KSP+ cells exhibited markedly increased proliferation. Notably, the proliferative response of KSP+ cells was closely correlated with Notch activation. CONCLUSION: Our lineage tracing data supports the KSP+ lineage behaves as a multipotent progenitor population. These cells give rise to cells of multiple nephron segments and preferentially drive postnatal kidney development. In adult kidneys, KSP+ cells are quiescent under homeostasis but become highly proliferative after renal injury, and this proliferative response is closely associated with activation of the Notch signaling pathway.