Enhanced Renoprotective Effect of GDNF-Modified Adipose Derived Mesenchymal Stem Cells on Renal Interstitial Fibrosis

Abstract

Background: The therapeutic effect of Mesenchymal stem cells (MSCs) from human adipose tissue on renal interstitial fibrosis has been demonstrated by several groups. However, the way to enhance the renoprotective effect of Adipose Derived Mesenchymal Stem Cells (AMSCs) and the possible mechanisms, are still unclear. The present study aimed to determine whether glial cell line-derived neurotrophic factor (GDNF)-modified AMSCs holds an enhanced protective effect on renal fibrosis. Methods: AMSCs were isolated and purified for culture. GDNF gene was constructed to transfect into AMSCs. The ability of AMSCs and GDNF-AMSCs supernatants to promote tube formation of endothelial cells, repair damaged endothelial cell junctions and improve endothelial cell function was compared by tube formation assay, immunofluorescence techniques and vascular ring assay, respectively. Furthermore, HE and Masson staining were used to observe the histological morphology of the kidney in vivo. Peritubular Capillary Changes were detected and analysed by Fluorescence Micro-angiography (FMA). Meanwhile, the endothelial cell, hypoxia, oxidative stress, fibrotic markers and PI3K/Akt pathway proteins were measured by western blot or qRT-PCR technics. Results: Studies in vitro demonstrated that compared with AMSCs only, GDNF-AMSCs could better repair injured endothelial cells and promote angiogenesis through secreting more growth factors in the supernatant of GDNF-AMSCs culture media. Studies in vivo, unilateral ureteral obstruction (UUO)-induced fibrotic mice were injected with transfected AMSCs through their tail veins. We showed that enhanced homing of AMSCs were observed in the GDNF-AMSC group compared with the AMSC group. GDNF-AMSCs treated animals exhibited better improvement of capillary rarefaction and fibrosis induced by obstructed kidney compared with the AMSC group. Furthermore, we reported that GDNF-AMSCs protect renal tissues against microvascular injuries via activation of the PI3K/Akt signaling pathway. Therefore, GDNF-AMSCs further ameliorated the tissue hypoxia, suppressed oxidative stress, and finally inhibited endothelial to mesenchymal transition noting by decreased coexpression of endothelial cell (CD31) and myofibroblast (a-SMA) markers. Conclusion: Collectively, our data indicated that the GDNF gene enhances the ability of AMSCs in improving renal microcirculation through PI3K/Akt/eNOS signaling pathway, and afterward inhibit the EndMT process and kidney fibrogenesis, which should have wide implications in designing future remedies for chronic kidney disease (CKD) treatment.