Background: Several preventative therapies for acute kidney injury (AKI) in mice require an intact spleen. However, the interaction of the spleen with AKI is unknown. Therefore the objective of the current study was to determine how prior splenectomy (SPLX) modulates the susceptibility of mice to AKI.

Methods: Male 8-12 wk old C57BL/6 or Rag1-/- mice underwent SPLX or sham operation 7d prior to subthreshold, bilateral renal ischemia-reperfusion injury (subIRI). After 24h of reperfusion, AKI was assessed by plasma creatinine and histology. Renal inflammation was determined by FACS, immunohistochemistry, and renal CXCL1 and IL-6 mRNA expression. In separate experiments, phagocytic splenocytes were labeled by i.v. injection of fl uorescently labeled liposomes 24h prior to unilateral IRI. Tissue samples were collected 1, 3, and 7d following reperfusion.

Results: 5d after SPLX, no difference (P≥0.25) was observed in circulating leukocytes or total hematocrit compared to sham-operated mice. Plasma creatinine (mg/dL) in mice receiving subIRI alone was similar (0.4) to controls (0.3). However, SPLX+subIRI resulted in higher plasma creatinine (1.2, P=0.001) and acute tubular necrosis (15% of kidney section area) compared to subIRI alone (5%, P<0.001). SPLX+subIRI resulted in increased circulating (P=0.009) and infiltrating neutrophils (P<0.001) and renal mRNA expression of CXCL1 and IL-6 (P≤0.003). SPLX Rag1-/- mice were also more susceptible to IRI (P<0.001), suggesting the effect of SPLX is not dependent upon T or B-cells. Fluorescently labeled cells were observed 3d after reperfusion and persisted only in the ischemic kidney through 7d, suggesting phagocytic cells originating from the spleen localize to ischemic renal tissue following AKI.

Conclusions: The spleen mediates the susceptibility of mice to IRI. Prior SPLX results in increased renal inflammation and damage following IRI. Trafficking of splenic phagocytes does not appear to influence AKI, since fluorescently labeled cells were not observed in the ischemic kidney until 3d after reperfusion.