Co‐treatment with erythropoietin derived HBSP and caspase‐3 siRNA: A promising approach to prevent fibrosis after acute kidney injury

Acute kidney injury (AKI) is a risk factor of chronic kidney disease, without specific treatment. This study investigated the effect of co‐treatment using erythropoietin‐derived helix B surface peptide (HBSP) and caspase‐3 small interfering RNA (CASP3siRNA) on preventing fibrosis post AKI in order to achieve better efficacy by different action mechanisms. Ischemia–reperfusion (IR) in mice was induced by clamping bilateral renal pedicles for 30 min followed by 2‐week reperfusion, with HBSP and/or CASP3siRNA administered at the onset of IR. Serum creatinine, apoptosis, active caspase‐3 and high mobility group protein B1 (HMGB1) in kidneys were decreased by HBSP, CASP3siRNA or both, with increased PCNA. α‐SMA expression and collagen I deposition were also reduced by CASP3siRNA and both. Most interestingly, the co‐treatment further reduced tubulointerstitial damage and fibrosis, but raised PCNA compared to CASP3siRNA. EPOR/βcR was reduced by HBSP, and positively correlated with Sirius red staining, whereas EPOR was unchanged. In TCMK‐1 cells, H2O2 raised apoptosis and α‐SMA were reduced by HBSP, while the same was occurred to HMGB1. However, HMGB1 was further increased by EPOR siRNA under H2O2 stimulation with/without HBSP treatment. In conclusion, this study demonstrated synergistic long‐term renoprotection post IR‐AKI by HBSP and CASP3siRNA, which may be due to co‐inhibiting inflammation and stimulating repair at early stage, and subsequently preventing fibrosis.