Abstract Body: Introduction:

Juxtaglomerular (JG) cells sense changes in blood pressure through communication with neighboring cells, and/or the sympathetic nervous system upon which they release renin to maintain homeostasis. To meet the demands for circulating renin when homeostasis is threatened, smooth muscle cells (SMCs) of the renal arterioles are transformed to renin-synthesizing cells. Discriminating transformed cells versus JG cells using sorting and scRNA-seq is cumbersome, limiting our ability to explore the events underlying such transformation. Therefore, there is a need to study these cells in situ to assign and determine which epigenomic and cell communication pathways regulate renin expression and SMC transformation.

Hypothesis:

Transformation of SMCs to renin-expressing cells during homeostatic stress requires specific signals from neighboring cells in addition to intrinsic transcriptomic changes.

Methods:

A pilot study was performed using two three-month-old C57BL/6 mice fed either a normal diet, or a low-salt diet with the RAS inhibitor, captopril, to induce homeostatic stress. After one week, the kidneys were harvested and prepared for the 10X Genomics Visium platform. Sequencing results were preprocessed using the Space Ranger pipeline (v. 2.0.1) with the mouse mm10 genome prior to downstream analysis using the R packages Seurat, Signac, and CellChat.

Results:

Homeostatic challenge significantly increased Ren1 expression (p_Holm-adj.=4.63x10^-10) and led to more and stronger cellular interactions. Interstitial cells and JG cells contributed the largest percent increase in the observed signaling changes (6.5% and 4.5% respectively). Increased signals for collagen, amyloid precursor protein, osteopontin, laminin, thrombospondin 1, vascular endothelial growth factor, and growth arrest specific pathways drove changes between native and transformed renin-expressing cells. In addition to the established JG cell markers Ren1 and Akr1b7, transformed cells had significantly increased expression (p_{Bonferroni-adj} < 0.01) of Hmgcs2, Cyp4a14, Suox, Acta2, Slc2a5, Ptp4a3, Sncg, and Rad21.

Conclusions:

In conclusion, spatial transcriptomics revealed the evolution of SMC transformation into renin phenotypes by uncovering pathways and genes understudied in the context of renin regulation. Future work will leverage higher resolution spatial technology and further explore the contribution of identified pathways to renin regulation and SMC transformation.