Abstract Body: Experimental or spontaneous mutations of any of the renin-angiotensin system (RAS) genes or treatment with RAS inhibitors in mammals lead to kidney concentric arterial and arteriolar hypertrophy (CAAH). Despite the prevalent use of RAS inhibitors in children and adults, our knowledge of this disease is very limited.
We assessed the hypothesis that mouse models of CAAH will produce identifiable and reproducible markers of early and progressive disease.
We generated murine models that tracks the lineage of renin-producing cells with deletion (Ren1^c-/-;Ren1^cCre;R26R^mTmG, Ren1cKO) or an intact renin gene (Ren1^c+/-;Ren1^cCre;R26R^mTmG, control). Kidney cells expressing GFP and tdTomato were isolated by FACS and processed for scRNA-seq. Plasma and urine were collected for proteomics, metabolomics and lipidomics. To study kidney function and structure, we measured transdermal glomerular filtration rate (tGFR) and performed comprehensive three-dimensional (CUBIC) and immunohistochemical analyses.
Ren1cKO mice presented with a decrease in the GFR (1.47±0.02 vs 0.40±0.06 mL/min/100g b.w (n=6; P<0.05)). They also had polydipsia (3.9±0.05 vs 9.6±0.09 mL/24h (n=6; P<0.05), polyuria (2.4±0.07 vs 5.9±0.09 mL/24h (n=6; P<0.05) and marked reduction in urinary osmolality (1384±92.09 vs 588±68.04 mOsm/kg (n=6; P<0.05). The wall thickness of the afferent arterioles in Ren1cKO mice was significantly increased when compared to controls (4.54 ± 0.17 μm vs 11.57 ± 0.91 μm, P<0.05). The hypertrophic arterioles were covered along their lengths with cells positive for renin. Plasma metabolites showed a significant increase in fatty acids and phosphatidylcholines (P<0.05) in Ren1cKO mice. Collagens (P<0.05), lymphocyte antigens (P<0.05), Spink 1 (P<0.05), and cadherin 13 were differentially abundant with cadherin 13 exclusively detected in Ren1cKO mice at 1 and 6 months. Our scRNA-seq data also found Spink 1 (P_Holm-adj.=0.00) and Cadherin 13 (P_Holm-adj.=5.49X10³) significantly increased in renin null cells, corroborating the proteomic findings.
1) CAAH involves smooth muscle cell transdifferentiation to renin-expressing cells that exhibit a mesenchymal phenotype characterized by pro-inflammatory pathways, and deregulation of lipid-metabolic homeostasis. Further, the exclusive expression of Spink and Cadherin 13 suggest their involvement in the pathogenesis of these severe, and silent arteriolar disease. Those molecules may serve to mark the initiation and progression of CAAH.