Chronic Stimulation of Renin Cells Leads to Vascular Pathology

Abstract

Experimental or spontaneous genomic mutations of the renin-angiotensin system or its pharmacological inhibition in early life leads to renal abnormalities including poorly developed renal medulla, papillary atrophy, hydronephrosis, inability to concentrate the urine, polyuria, polydipsia, renal failure and anemia. At the core of such complex phenotype is the presence of unique vascular abnormalities: the renal arterioles do not branch or elongate properly and they have disorganized, concentric hypertrophy. This lesion has been puzzling because it is often found in hypertensive individuals whereas mutant or pharmacologically inhibited animals are hypotensive. Remarkably, when renin cells are ablated with diphtheria toxin, the vascular hypertrophy does not occur suggesting that renin cells per se may contribute to the vascular disease. To test this hypothesis, on a Ren1c−/− background, we generated mutant mice with reporter expression (Ren1c−/−;Ren1c-Cre;R26R.mTmG; and Ren1c−/−;Ren1c-Cre;R26R.LacZ ) to trace the fate of reninnull cells. To assess whether reninnull cells maintain their renin promoter active, we used Ren1c−/−;Ren1c-YFP mice which transcribe YFP directed by the renin promoter. We also followed the expression of Akr1b7 and miR-330-5p, markers of cells programmed for the renin phenotype. Contrary to what we expected, reninnull cells did not die or disappear. Instead, they survived, increased in number along the renal arterial tree, and maintained an active molecular memory of the myo-epitheliod renin phenotype. Further, null cells of the renin lineage occupied the walls of the arteries and arterioles in a chaotic, directionless pattern directly contributing to the concentric arterial hypertrophy.

Super-enhancers maintain renin-expressing cell identity and memory to preserve multi-system homeostasis

“…They harbor the same Ren1 c-YFP transgene described above, reporting the activity of the renin promoter via YFP (9), which marks the recruited renin cells along the arterioles ( Figure 1C). These mice have 5 to 10 times more YFP + cells (range: 1,770-80,369; median: 16,175; mean: 18,334) along the arterioles than JG cells from WT mice (range: 841-6,917; median: 3,771; mean: 3,863; P < 0.001), and although these native renin cells do not produce RENIN, they maintain a super-activated renin promoter and conserve the molecular program of the renin cell phenotype (7). The results from those in vivo-isolated cells were compared with a third cellular model of renin-producing cells, the As4.1 kidney tumoral cells, derived from transgenic mice that harbor a transgene containing the Ren2 5′ regulatory noncoding region fused to the SV40 T antigen gene ( Figure 1D).…”

“…To investigate whether the super-enhancers found in renin cells were exclusive to them, we compared H3K27ac ChIP-Seq data from native recruited cells and As4.1 cells with H3K27ac ChIP-These results suggest that under short-term physiological stimulation, newly recruited cells may possess a chromatin configuration that resembles the chromatin of JG cells. On the other hand, chronic protracted stimulation, such as occurs in Ren1 c knockout animals or in tumoral As4.1 cells, may result in additional chromatin changes unrelated to the core chromatin features that determine the renin phenotype but rather to concomitant pathological changes that may occur in these 2 situations (7,10).…”

“…Ultimately this results in decreased arterial blood pressure, emphasizing the relevance of Med1 function in renin cells for blood pressure control even in the basal state. Given that absence of Med1 also affects the expression of Akr1b7, a renin-independent marker of cells programmed for the renin phenotype, the fate of the cells that stopped making renin remains to be determined by carefully designed lineage tracing experiments (7). We anticipate that lack of Med1 in renin cells leads to a dissipation of the renin superenhancer, making it impossible for the transcription machinery to activate the renin gene.…”

“…After blood was collected for renin measurements, blood samples were collected into heparinized and EDTA plasma separator tubes (Microtainer). Complete blood count and the basic metabolic panels were performed by the University of Virginia Hospital clinical laboratory (7).…”

A primitive type of renin-expressing lymphocyte protects the organism against infections

“…To determine whether these lymphocytes with a renin pedigree manufacture and release renin, we used a dot membrane immunoassay (13,14). Peritoneal cells from Ren1 dcre/+ ; mTmG reporter mice were cultured on nitrocellulose membranes for 48 hours followed by dot immunoassay for renin using a well characterized renin antibody and color development detection kit as previously described (15). Figure 2a shows that peritoneal cells derived from the renin lineage appear as discrete blue dots indicating that these cells actively release renin.…”