Introduction: Chronic stimulation of renin cells by long-term renin-angiotensin system (RAS) inhibition causes renal arteriolar hypertrophy, hyperinnervation, fibrosis, and perivascular immune cell infiltration. Our previous studies indicated these pathological changes are initiated by renin cells, which increase in number, revert to an embryonic-secretory phenotype, and induce concentric accumulation of smooth muscle cells (SMCs). Multiple cell-cell interactions and signaling events likely underlie these phenomena, however, the precise mechanisms remain poorly understood. To understand these mechanisms requires examining RNA expression profiles within cells while preserving the intricate tissue architecture and the topological relationships of the renal arterioles with adjacent glomeruli, juxtaglomerular and tubular-interstitial areas. Hypothesis: Interaction between renin cells and surrounding tissues plays a critical role in renal arteriolar hypertrophy under chronic RAS inhibition. Methods: We utilized two experimental models of RAS inhibition: 1) SMMHC CreERT2 ; R26R tdTomato ; Ren1 cYFP mice treated with captopril for 6 months, and 2) Ren1 c KO mice analyzed at 6 months of age, each compared to age-matched controls. High-resolution spatial transcriptomics were performed using VISIUM HD. Selected gene expressions were validated by qPCR in renal cortex (n≥5 per group). Results: Spatial transcriptomics analysis revealed 887 genes significantly upregulated (p<0.05) in both the captopril-treated and the Ren1 c KO mice. Among these, we focused on key genes:(i) Aldh1a2 and Krt19, genes associated with activation of retinoic acid (RA) signaling, were markedly upregulated in the renin cells and transform SMCs; (ii) Pappa2 , which locally regulates insulin-like growth factor (IGF) bioavailability, was strongly upregulated specifically at the macula densa; and (iii) nerve growth factor ( Ngf ) expression increased in regions corresponding to Ren1 expression and fibrosis. qPCR validation confirmed significant up-regulation of these genes under both RAS inhibition models. Conclusions: Spatial transcriptomics identified localized activation of RA and IGF signaling surrounding renin cells as well as enhanced neurogenesis under long-term RAS inhibition. These molecular factors likely drive the synergistic dedifferentiation and accumulation of renin cells, and sustained renin production. This findings may provide novel insights into treating vascular remodeling and hypertension.
Yamaguchi et al. (Mon,) studied this question.