Abstract P216: Multiomics Approach To Unravel The Molecular Mechanisms Responsible For Kidney Concentric Arterial And Arteriolar Hypertrophy

Abstract

Introduction: Experimental or spontaneous mutations of any of the renin-angiotensin system (RAS) genes or treatment with RAS inhibitors in mammals -including humans- lead to kidney concentric arterial and arteriolar hypertrophy (CAAH), a silent, progressive, and severe thickening of the intrarenal arterial tree. Therefore, it is crucial to comprehend the identity and fate changes of the vascular smooth muscle cells (VSMCs) as they switch their phenotype to renin-producing cells (RPC) during the progression of the arteriolar disease. Objective: Using new mouse models and single-cell ‘omic’ approaches available in our lab to assess the chromatin landscape of the RPCs and VSMCs, we aim to identify the genomic hotspots that determine the initiation, evolution, and ultimate fate of the diseased cells. Methods: We generated two murine models. In the first model ( Ren1 c-/- ;Ren1 cCre ;R26R mTmG ) the renin gene is deleted while the cells (renin null cells) are labeled green (GFP+) from embryonic life. In the second model ( SMMHC CreERt2 ; R26R tdTomato ; Ren1 cYFP ) VSMCs are labeled red (tdTomato+) upon tamoxifen injection whereas cells currently expressing renin are labeled yellow (YFP+). Kidney cells expressing the different fluorophores were isolated by Fluorescence Activated Cell Sorting and processed for Single Cell Multiome ATAC (Assay for Transposase-Accessible Chromatin) + Gene Expression, using 10X Genomics Chromium technology. Results: The wall thickness of the afferent arterioles in Ren1 C KO mice was significantly increased when compared to control (4.54 ± 0.17 μm vs 11.57 ± 0.91 μm, P <0.0001). The hypertrophic arterioles were covered along their lengths with cells positive for renin, suggesting that renin cells were involved in the hypertrophy. As the mice got older, SMCs accumulate inwardly and concentrically, obstructing the vessels lumens, leading to focal fibrosis. Conclusion: Our studies showed that deletion of the renin gene led to CAAH. Experiments involving transcriptomics and epigenomics are ongoing to understand the evolution of the CAAH and identify and transcriptional profile changes that occur at the single-cell level.