Twin Glomeruli: a Newly Discovered Marker of Neonephrogenesis in the Ischemia-Reperfusion Injured Adult Mouse Kidney.

BACKGROUND: The renal glomerulus, a capillary network between two arterioles, is essential for urine production in mammals. While it partially regenerates after renal injury, its precise mechanisms remain unclear, and stereological studies on post-injury glomerular structural changes are limited. METHODS: Therefore, this study aims to investigate three-dimensional glomerular alterations over time following ischemia-reperfusion injury (IRI) in adult mouse kidneys. Synchrotron radiation micro-computed tomography (SR-MCT) and immunohistochemical analyses were employed to visualize and quantify three-dimensional glomerular structures and nephron numbers from 1 to 21 days post-IRI. RESULTS: A unique "twin glomeruli" structure, linked to three arterioles through an atypical "aefferent" arteriole, appeared between 3 and 21 days post-IRI, peaked on day 9, and exhibited features distinct from both degenerating and developing glomeruli. SR-MCT revealed a time-dependent increase in nephron numbers between 1 and 21 days post-IRI, while immunohistochemistry revealed significant elevated glomerular and tubular densities from days 9 to 21. These findings suggest that twin glomeruli are transient structures induced by IRI and may contribute to nephron expansion. CONCLUSION: This study challenges current understanding by demonstrating that twin glomeruli represent an atypical glomerular structure occurring during kidney repair and suggesting possible neonephrogenesis in the adult mouse kidney, a phenomenon previously considered impossible after birth. If similar results are observed in humans, it could lead to significant changes in the approaches and objectives for treating renal diseases. Additionally, a comprehensive investigation into the numerical response of glomerular counts to various stimuli could provide valuable insights into kidney regeneration and repair.