Abstract: FR-PO333

GPR124 Regulates Development of Kidney Medulla and Adult Kidney Fibrosis via Wnt7a/b Dependent and Independent Signaling

Session Information

Category: Chronic Kidney Disease (Non-Dialysis)

  • 308 CKD: Mechanisms of Tubulointerstitial Fibrosis

Authors

  • Ikeda, Yoichiro, Washington University, School of Medicine, St. Louis, Missouri, United States
  • Liu, Jing, University of Southern California, Los Angeles, California, United States
  • McMahon, Andrew P., Keck School of Medicine of the University of Southern California, Los Angeles, California, United States
  • Humphreys, Benjamin D., Washington University School of Medicine, Clayton, Missouri, United States
Background

GPR124 is an orphan GPCR expressed in endothelial cells where it is a coreceptor for Wnt7a/b to activate canonical Wnt signaling. Wnt7b is required for the development of kidney medulla and cortico-medullary axis, and Wnt7a is associated with renal function and fibrosis. Pericyte-specific translational profiling revealed strong upregulation of GPR124 mRNA during kidney fibrosis. We investigated the role of GPR124 in pericytes and myofibroblasts during kidney development and fibrosis.

Methods

Models were developed for overexpression of GPR124 in fibroblasts (NRK-49F) and Crispr/Cas9-mediated knockout in myofibroblasts (10T1/2). Kidney stroma-specific deletion was accomplished with FoxD1-Cre;GPR124 floxed mice and conditional deletion with Gli1-CreER; GPR124 floxed; R26(tdTomato) mice.

Results

GPR124 mRNA was strongly upregulated in whole kidney during mouse UUO by qPCR, and specifically in the interstitium by in situ hybridization. GPR124 expression directly correlated with degree of fibrosis in human kidney. Lentiviral overexpression of GPR124 in NRK49f fibroblasts drove spontaneous myofibroblast differentiation even in the absence of Wnt ligand. By contrast, Crispr/Cas9 knockout of GPR124 in 10T1/2 mesenchymal cells, caused a strong reduction in fibrotic marker expression including aSMA and collagens. These knockout cells also failed to respond to Wnt7a and 7b ligand, confirming that GPR124 is a Wnt coreceptor in pericytes. Stromal specific GPR124 knockout mice resulted in a hypomorphic medulla phenotype and the loss of cortico-medullary axis, phenocopying the HoxB7-Cre; Wnt7b(f/f) phenotype. In addition, knockout mice showed microvascular hemorrhage in medulla. Conditional deletion of GPR124 in adult mouse kidney using Gli1-CreER; GPR124(f/f) ;tdTomato mice with tamoxifne administration resulted in reduced fibrosis in two fibrotic models also associated with reduced canonical Wnt-b-catenin signaling.

Conclusion

GPR124 is unexpectedly expressed in kidney pericytes and perivascular fibroblasts where it regulates Wnt7a/b signaling and drives myofibroblast differentiation. During development, stromal GPR124 is required for medullary development and in fibrosis GPR124 plays a critical role in regulating pericyte and fibroblast to myofibroblast transition.

Funding

  • NIDDK Support