Renal Myofibroblasts Undergo Autophagy to Support Cyst Growth in Autosomal Dominant Polycystic Kidney Disease

Background: Myofibroblasts often surround renal epithelial cysts in autosomal dominant polycystic kidney disease (ADPKD). Our previous studies showed that myofibroblast depletion ameliorates disease progression in the RC/RC mouse model of ADPKD. Based on our observation that myofibroblasts in ADPKD kidneys undergo autophagy, we examined if autophagy in myofibroblasts contributes to renal cyst growth in ADPKD. Methods: Cell proliferation of human ADPKD renal cyst epithelial cells exposed to cell culture conditioned media from human ADPKD myofibroblasts treated with vehicle or autophagy inhibitor- chloroquine was measured. Autophagy protein 5 (ATG5) is crucial for autophagy. We made myofibroblast-specific Atg5 gene knockout- RC/RC;Atg5f/f;PDGFRbcreERT2 mouse by breeding RC/+;PDGFRbcre-ERT2 mouse with Atg5f/f mice. Wild type (WT), Atg5KO; RC/RC, RC/RC:Atg5KO mouse littermates were treated with vehicle or tamoxifen and sacrificed at 28 weeks of age and their kidneys were analyzed. Results: Immunofluorescence staining in human ADPKD kidneys and RC/RC mouse kidneys showed that myofibroblasts surrounding renal cysts undergo autophagy. Human ADPKD renal cyst epithelial cells exposed to human ADPKD renal myofibroblast-conditioned media proliferated more compared to cells exposed to control media. Inhibition of autophagy in ADPKD human-renal myofibroblasts reduced the ability of their conditioned media to induce cyst epithelial cell proliferation in vitro. RC/RC:Atg5KO group had significantly lower kidney/body weight ratio, cyst number and cystic index when compared to RC/RC group. RC/RC:Atg5KO group had significantly reduced fibrosis and extracellular matrix related gene expression when compared to RC/RC group. No morphological changes were observed in Atg5KO mice when compared to WT. Conclusion: Our results suggest that myofibroblasts in ADPKD kidneys undergo autophagy to support cyst growth, and inhibition of autophagy in renal myofibroblasts leads to reduced renal cyst growth and fibrosis. Funding: NIDDK Support