LYVE1 Ectodomain Shedding Promotes Renal Interstitial Retention of Macrophages Cleared by Lymphatic Vessels and Kidney Fibrosis

Background: Macrophage accumulation has been associated with the progression of renal fibrosis. However, most previous studies have focused on the recruitment of macrophages while neglecting their efflux. Lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1) has a macrophage-binding domain at the extracellular site, which mediates macrophage adhesion and subsequent translocation in lymphatic vessels (LVs). However, it is unknown whether LYVE1 is altered in renal disease and whether it thereby mediates changes in macrophage trafficking. Methods: Models of ureteral obstruction (UUO), ischemia/reperfusion (I/R), folic acid (FA)-induced renal fibrosis models were created for in vivo experiments and human lymphatic endothelial cell (hLEC) line was used for in vitro experiments. Results: First, we found that macrophages were significantly recruited and clustered around LVs in the mouse fibrosis models. We further showed that in renal fibrosis models and TGF-β1-cultured hLECs, LYVE1 shed its extracellular domain on LECs and therefore lost its macrophage-binding domain, thus hindering macrophage adhesion to LECs. Meanwhile, LYVE1 shedding fragments were shown to mediate macrophage-to-myofibroblast transition (MMT) to promote fibrosis. Mechanistically, elevated MMP9 mediated LYVE1 ectodomain shedding, resulting in the loss of sites for macrophage binding. The use of chemical shedding inhibitors or MMP9 targeting siRNA attenuated LYVE1 shedding, restored macrophages trafficking and alleviated renal fibrosis. Conclusion: LYVE1 shedding is tightly associated with progression of renal fibrosis, whereas inhibition of LYVE1 shedding is capable of ameliorating macrophage aggregation and MMT to attenuate disease progression.Schematic graph