Specific BFGF Targeting Of KIM-1 In Ischemic Kidneys Protects Against Renal Ischemia Reperfusion Injury In Rats

ObjectiveRenal ischemia reperfusion injury(I/R)is one of the major causes of acute kidney injury(AKI).However,there is still no effective treatment for this disease.Basic fibroblast growth factor(bFGF)was reported to be beneficial for the recovery of ischemic diseases,which could promote the angiogenesis and protect the cell survival.Currently,to increase the local concentration and reduce the diffusion of bFGF in vivo is critical for the therapy of renal I/R injury.When ischemic renal injury occurs,kidney injury molecule-1(KIM-1)is significantly up-regulated and continuously expressed in ischemic renal tissue.It is reported that the specific short peptide KIT screened by Phage Display technology can specifically bind to KIM-1 in ischemic renal tissue.Therefore,the purpose of this study is to construct specific targeted drug delivery system KIT-bFGF,which can improve the effective concentration of bFGF in the ischemic kidney tissue,reduce bFGF diffusion in peripheral blood,and provide a new,safe and reliable treatment strategy for AKIMethods and ContentsWe fused KIT peptide with bFGF to construct a modified bFGF-kidney injury targeting bFGF(KIT-bFGF),which specifically targeted to the KIM-1 both in hypoxic renal HK-2 cells in vitro and ischemic kidney by intravenous injection in vivo.The biological activity of KIT-bFGF and native bFGF was detected by promoting the proliferation of HSFs.Then rat model of I/R injury was established and reperfusion for 1 h.KIT-bFGF and native bFGF protein were injected into rats through tail vein respectively.The protein content in ischemic kidney was detected by ELISA assay at 6 h and 24 h post-administration.Next,KIT-bFGF and native bFGF proteins were chemically crosslinked with fluorescein Dy Light-747 and injected into rats through tail vein.The targeting ability of KIT-bFGF in rats was evaluated by small animal imaging system in vivo.Finally,we used H&E staining,Masson staining,TUNEL staining,and other related pathological indexes to detect the protective effect of KIT-bFGF on ischemic renal tissues.Furthermore,the potential protective mechanism of KIT-bFGF in ischemic renal tissues was also explored.ResultsThe spatial structure of KIT-bFGF and native bFGF showed that the fusion of KIT short peptide did not affect the active domain of bFGF.And the results showed that KITbFGF protein and native bFGF protein had similar biological activities.The experiments showed that KIT-bFGF could specifically bind to hypoxia-induced HK-2 in vitro.The results of ELISA showed that the amount of KIT-bFGF significantly increased in the ischemic kidney at different times after ischemia compared with native bFGF.And after used in rat models with renal I/R injury,KIT-bFGF could attenuate the renal tubules damage,fibrosis and promote the functional recovery compared to native bFGF and PBS groups.In addition,the potential mechanism of KIT-bFGF was explored,which activated the ERK1/2and Akt signaling pathways to reduce apoptosis and protect against ischemic injury in the kidney.ConclusionsIn summary,the modified bFGF(KIT-bFGF)specifically targeted to KIM-1 after renal I/R injury and retained in the ischemic kidney.KIT-bFGF can promote the recovery of renal function,alleviate renal injury,reduce the area of renal fibrosis,and protect kidneys from I/R injury.Therefore,this targeting delivery of KIT-bFGF could be a potential effective strategy for the therapy of renal I/R injury.