Grant: CIHR-ICRH Travel Awards - General pool

Background/aim: Acute kidney injury (AKI) caused by renal ischemia reperfusion (R I/R) is a major clinical issue that is lacking viable therapies, and its underlying mechanisms are poorly understood. Given the important role of hedgehog interacting protein in chronic kidney disease-related renal fibrosis, here, we aimed to investigate whether Hhip knockout in endothelial cells (EC) prevents R I/R-induced kidney injury in vivo and in vitro. Methods: Both male HhipEC KO and control Hhipfl/fl mice at 10-weeks old were subjected to 45 minutes of the unilateral R I/R or sham surgery with contralateral nephrectomy, respectively. The AKI time-course at Day1, Day 3, Day7 and Day 21 was performed. In vitro, naïve renal proximal tubular cells (IRPTCs) exposed to the conditioned media harvested from mouse endothelial cell (mECs) with or without Hhip (siRNA) ± gentamicin treatment, were studied. Results: Compared to the respective shamed controls, R I/R mice (Hhipfl/fl and HhipEC KO) loss body weight (BW, g) started from Day 1 until Day 21, regardless of Hhip deficiency or not. In line with AKI time course, Hhipfi/fl-R I/R mice displayed kidney dysfunction reviewed by increased urinary albumin-to-Creatinine ratio; tubular/endothelial cell injury and fibrosis assessed by kidney morphological staining (Periodic Acid-Schiff, Masson’s trichrome and Sirius Red) with enhanced Cystatin C-, KIM1-and TGFß1- immunoexpression in their kidneys. Maladaptive and inadequate renal tube damage repair was observed by enhanced vascular cell adhesion protein 1 (Vcam1) and NF/kB (p50/p65) expression. In contrast, these changes were significantly ameliorated in the kidneys of HhipEC KO -R I/R mice. In vitro, naïve IRPTCs exposed to the conditioned media harvested from mECs treated with gentamicin (2.5mg/ml) had lower wound healing ability/capacity, higher cellular senescent activity and increased NF/kB expression. Intriguingly, those changes were largely prevented in naïve IRPTCs exposed to the conditioned media harvested from Hhip KO mECs treated with gentamicin. Conclusion: Our data suggest that Hhip knockout in endothelial cells prevented AKI-induced renal tubular injury. This action might be mediated, at least, by the inhibition of NF-KB signaling.