Midkine‐Mediated Microglia Activation after Renal Injury Promotes Cognitive Impairment Following Ischemic Renal Injury

Abstract Acute kidney injury (AKI) is associated with a high prevalence of cognitive impairment, the underlying mechanisms remain elusive. This study explores the role of midkine (MDK), upregulated in renal injury, in mediating cognitive dysfunction following post‐ischemic renal injury. Using a mouse model of unilateral renal ischemia‐reperfusion injury, cognitive deficits and blood‐brain barrier disruption is observed. Single‐cell RNA sequencing and ligand‐receptor interaction analysis reveals a strengthened MDK‐LRP1 axis in both the kidneys and hippocampus of mice subjected to ischemic renal injury. MDK, mainly from injured renal tubular cells and fibroblasts, is enriched in peripheral blood and the hippocampus, correlating with increased activation of hippocampal microglia and upregulation of c. It is demonstrated that MDK internalization into microglia via LRP1 upregulated P2ry12 expression, promoting microglial activation and phagocytosis. Inhibiting renal MDK expression with shRNA adenovirus ameliorated cognitive dysfunction and attenuated microglial activation after ischemic renal injury. These findings suggest the MDK‐LRP1 pathway is a key mediator of cognitive dysfunction following ischemic renal injury and a potential therapeutic target for mitigating cognitive decline in AKI patients. It provides a mechanistic link between renal injury, neuroinflammation, and cognitive deficits, highlighting the potential of targeting MDK‐LRP1 signaling to address cognitive impairment after ischemic renal injury.