MO469: GPR124—A Driver of Fibrotic Kidney Diseases. (3rd May 2022) - Blank, Patrick
Abstract: BACKGROUND AND AIMS: Renal fibrosis is a central feature of chronic kidney disease (CKD), and the severity of CKD correlates with the magnitude of renal fibrosis. Despite the causative role attributed to fibrosis in CKD progression, there is still no treatment available that directly targets renal fibrosis. Upon kidney injury, embryonic signalling pathways are activated, promoting the repair and regeneration of injured tissue. Maladaptive repair mechanisms have been associated with the development of renal fibrosis and sustained activation of Wnt/β-catenin signalling contributes to CKD progression. GPR124 (ADGRA2 gene), has been identified as a potential fibrotic mediator through its upregulation in pericytes during pericyte to myofibroblast transition. GPR124 has been identified to function as a co-receptor for Wnt7 mediating canonical Wnt signaling in endothelial cells. We observed elevated GPR124 expression in mouse kidneys after chronic ischaemia reperfusion injury (cIRI). To further explore the role of GPR124 in CKD progression, we have studied its correlation with disease severity in human NURTuRE kidney biopsies [1 ]. We have also looked at GPR124 therapeutic potential in mouse cIRI. Given its potential disease relevance, we set out to develop inhibitory GPR124 antibodies as novel therapeutics to treat renal fibrosis. METHOD: Diagnostic FFPE kidney cortex biopsy samples from 497 NURTuRE patients were subjected to bulk RNA-Seq. Library preparation with Illumina Enrichment Tagmentation technology was followed by sequencing and alignment of paired-end reads to the reference genome GRCh38/ENSEMBL 97 and quantification. Monoclonal Anti-GPR124 antibodies were generated against the extracellular domain of human GPR124. Top candidates were selected by FACS binding and further characterized in a TCF/LEF luciferase assay for the inhibition of Wnt7 signaling. One hu/ms cross-reactive candidate was studied in a 14-day IRI mouse model to assess its anti-fibrotic effect in vivo. Mice were exposed to 30-min unilateral renal ischaemia, followed by 14 days recovery. Kidneys were studied for gene expression by RT-PCR. Animals were divided into sham ( n = 5), control IRI (no antibody, n = 12) and treated groups (each n = 12). The antibody was administered before ischemia and during the recovery phase in two doses [50 mg/kg and 150 mg/kg]. RESULTS: In NURTuRE kidney biopsies, GPR124 expression was enhanced in patients with CKD of unknown etiology, IgA Nephropathy, and Ischemic kidney disease. Elevated GPR124 expression correlated with increased disease severity (by G stage), increased tubulointerstitial fibrosis as seen by histopathology and regulation of extracellular matrix genes. From the 15 antibodies identified to bind to human GPR124, four candidates showed cross-reactivity to mouse GPR124 and showed specific inhibition of canonical Wnt7 signaling in TCF/LEF luciferase assay with an IC50 of 1 µg/ml. Renal ischaemia led to upregulation of profibrotic genes. In vivo administration of the inhibitory mAB led to 25–30% downregulation of the profibrotic genes Tgfb1, Acta2, Col1a1 and Col3a1 in the cIRI animals treated with GPR124 Ab compared to the untreated group. CONCLUSION: NURTuRE provides us with a unique opportunity to assess relevance of a potential target candidate gene in kidney disease patients. The potential of GPR124 as a therapeutic target was highlighted by the upregulation of expression levels along disease severity and biological pathway analysis, where our data supports a potential role in extracellular matrix reorganization. The administration of GPR124 antibodies and inhibition of the GPR124-mediated Wnt signaling in vivo inhibited the development of ischaemia-induced fibrosis in the mouse kidney. The results strongly support a role for GPR124 in human kidney disease progression, through inhibition of fibrosis, and its potential as a future clinical target.