Molecular Dissection of the Juxtaglomerular Apparatus

Background: The juxtaglomerular apparatus (JGA) plays a critical role in regulating renal hemodynamics, glomerular filtration rate, and systemic blood pressure through the coordinated actions of specialized cell types at the vascular pole of the nephron. While the distinct molecular identities of some of the cell types have recently been well-characterized, such as renin-producing juxtaglomerular cells and macula densa cells, the molecular identity of other key JGA cell types such as extraglomerular mesangial cells have remained elusive due to their sparsity within the kidney. Methods: We isolated nuclei from Pdgfrb-INTACT and Slc12a1-INTACT mouse kidneys enriching for GFP expressing nuclei with Fluorescent-Activated Nuclei Sorting and then transcriptionally profiled using the 10X Genomics platform. The resulting data was analyzed with Seurat to perform dimensional reduction which delineated the distinct populations of JGA cells at unprecedented molecular resolution. Pathways analysis was used to determine differences in molecular function between distinct JGA cell types while RNAscope was used to determine the specificity and spatial distribution of markers of distinct JGA cell types. Results: Slc12a1-derived nuclei divided into thick ascending limb (Cldn10/16+) and macula densa (Nos1+) cells while Pdgfrb-derived nuclei divided into fibroblasts (Pdgfra+), pericytes (Abcc9+), VSMCs (Acta2+), renin cells (Ren+), and mesangial cells (Piezo2+). VSMCs further divided into efferent (Tenm2+) and afferent (Hpse2+) subtypes while mesangial cells separated into extraglomerular (Adora1+) and intraglomerular (Col12a1+) subtypes. Pathway analysis revealed distinct molecular functions that differentiated efferent from afferent VSMC as well as extraglomerular from intraglomerular mesangial cells while RNAscope verified the specificity and spatial distribution of anchoring transcriptional markers. Conclusion: The JGA is composed of functionally and genetically diverse cells that work in harmony with each other to regulate critical kidney functions. Enriching for Pdgfrb and Slc12a1 derived nuclei enabled us to identify robust genetic markers of extraglomerular mesangial cells in the JGA, that have been previously unrecognized thereby deepening our understanding these rare kidney cell populations potentially uncovering novel targets for modulating renin release, glomerular filtration, or vascular tone. Funding: NIDDK Support, Private Foundation Support