The Role Of Hippo Pathway In The Mechanism Of NPHP1

Research background:Nephronophthisis(NPHP)is an autosomal recessive cystic renal disease which is also call ciliopathy.It is one of the most common inherited diseases that causes End Stage Renal Disease(ESRD)in children and adolescent.The histology manifestations of NPHP are including corticomedullary cyst caused by the expansion of distal tubule,interstitial fibrosis and chronic inflammation.Studies finds that there are more than twenty genes related to NPHP,30%of which is the mutation of NPHP 1,and it is the most common in the patients who have NPHP,the kind of disease caused by NPHP1 mutation is called NPHP1.However,the mechanism of cyst formation and interstitial fibrosis in NPHP1 still reminded unknown,some studies hypothesis that HIPPO pathway is related to the mechanism of NPHP.Studies finds that Hippo pathway is associated with the function of cilium and tissue fibrosis,KIBRA is an upstream factor of hippo pathway and it is related to cell polarity protein.In our previous study,we find that the expression of KIBRA is upregulated in NPHP 1-knockout MDCK cell lines,we speculate Hippo pathway may play an important role in NPHP1 through KIBRA.This study investigates the role that KIBRA plays in NPHP1 through hippo pathway using NPHP1 knockout mice model which has been established in previous work and AAV9-KIBRAsiRNA.In addition,we explored the therapeutic effect of human umbilical cord mesenchymal stem cells(HUCMSCs)in NPHP1 knockout mice and the regulation of HIPPO pathway in it.Result:This study established KIBRA-KD-NPHP1-/-mice model using vector that expressing AAV9-KIBRA-siRNA.the virus particles of AAV9-KIBRA-RNAi was intravenously injected into 5 weeks old mice(n=6),and half of them were harvested at 12 weeks old and the remanent at 36 weeks old.We use western blot to identify the expression of KIBRA and use immunofluorescence analysis to identify the mainly location of KIBRA in mouse kidney,and we evaluated the phenotype of mice kidney via HE staining and Periodic Acid Schiff(PAS)Staining.Results show that knocking down the expression of KIBRA in NPHP1-/-mice can decrease the renal cyst formation and renal fibrosis.We examined the expression of factors of Hippo pathway through immunohistology analysis,the results reveal that downregulating expression of KIBRA may promote YAP cytoplasmic retention,phosphorylation and inhibit nuclear location through upregulated MST1,inhibit cyst formation,and downregulating expression of KIBRA can decrease the expression of FSP1 in interstitial cells and the expression of CTGF in tubular cells in NPHP1-/-mice.In addition,we explored the therapeutic effect of human umbilical cord mesenchymal stem cells(HUCMSCs)in NPHP1 knockout mice,and we further examined the expression of core components and effectors of Hippo pathway.Conclusion:Knocking down the expression of KIBRA in NPHP1-/-mice can decrease the renal cyst and renal fibrosis,promote YAP cytoplasmic retention and YAP phosphorylation,promote the expression of p-MST1 in tubular cells.Which suggested that Hippo pathway may have a difference in NPHP1 through KIBRA.Human umbilical cord mesenchymal stem cells have therapeutic effect on NPHP1;HUCMSCs therapeutic in NPHP1-/-mice promote the expression of p-MST1,YAP cytoplasmic retention and YAP phosphorylation in tubular cells.