Aldosterone Receptor in Vascular Muscle Fails to Drive Atherosclerosis in Either Sex of Mice

A long-standing suspicion in cardiovascular research has just been put to a rigorous test, and the answer is a clean negative. The mineralocorticoid receptor, the molecular sensor that allows the stress hormone aldosterone to switch genes on and off inside cells, has been implicated in nearly every stage of artery disease. Yet when researchers deleted this receptor selectively from vascular smooth muscle cells in atherosclerosis-prone mice, the plaques in their arteries looked essentially indistinguishable from those of animals that retained the receptor. The result held for males and females alike, and it forces a recalibration of where scientists should look for the inflammatory and structural effects of aldosterone on the vessel wall.

The study, conducted by Nicole L. Svedberg, Wenxi An, Sorelle Tan and Iris Z. Jaffe and published in PLOS One, set out to close a conspicuous gap in the experimental literature. Earlier work from the same field had shown that removing the mineralocorticoid receptor from endothelial cells, the thin lining of the artery, or from myeloid cells, the immune population that infiltrates growing plaques, worsens atherosclerosis in male mice. Those same experiments, however, revealed a striking sexual dimorphism: the endothelial and myeloid effects largely vanished in females. Smooth muscle cells, the spindle-shaped cells that populate the fibrous cap of a plaque and determine its stability, had only been tested in males, where deleting their receptor produced no measurable change in plaque phenotype. Whether the female artery responds differently to the loss of smooth muscle mineralocorticoid signaling had never been examined.

The biological stakes of that question are considerable. Aldosterone, a steroid hormone produced by the adrenal cortex, circulates at higher levels in obesity and independently associates with an increased incidence of myocardial infarction in human studies. The mineralocorticoid receptor is a ligand-activated transcription factor; when aldosterone binds it, the complex translocates to the nucleus and modulates the expression of genes governing sodium handling, inflammation, fibrosis and cell growth. In the vasculature, smooth muscle cells are not passive scaffolding. They migrate, proliferate and deposit extracellular matrix in response to injury, and their behavior largely determines whether a plaque remains a stable fibrous cap or ruptures into a lethal clot. If aldosterone acted on these cells through their receptor to accelerate disease, blocking that interaction could have been a therapeutic target.

To test the hypothesis genetically, the team crossed mice lacking apolipoprotein E, a classic model in which lipid clearance fails and plaques develop on a high-fat diet, with animals whose mineralocorticoid receptor gene was flanked by loxP recombination sites and carried a tamoxifen-inducible Cre recombinase driven by the smooth muscle alpha-actin promoter. The offspring could therefore be divided into littermates with the receptor intact in smooth muscle and littermates in which the gene had been deleted specifically in those cells, all on the same atheroprone background. The inducible design matters because it sidesteps developmental compensation: the receptor functions normally throughout growth and is removed only in adulthood, immediately before the atherosclerosis challenge begins.

Validation came first. Quantitative measurement of messenger RNA from the aorta confirmed significant knockdown of receptor expression in both male and female knockout animals, establishing that the genetic manipulation had actually reached its target in the relevant tissue. The researchers then placed the mice on a high-fat diet for eight weeks, a window that captures early atherosclerotic lesion development rather than end-stage disease. Throughout this period they tracked the physiological variables that aldosterone is known to influence. Deletion of the receptor in smooth muscle cells left plasma aldosterone concentrations, blood pressure, fasting glucose, cholesterol and body weight essentially unchanged in both sexes. The only metabolic difference observed was the expected one between genotypes: male mice weighed significantly more than females, a baseline feature of the model rather than a consequence of the knockout.

The critical readout was the plaque itself. Examining cross-sections of the aortic root, the standard anatomical site for quantifying atherosclerosis in mice, the investigators found that removing the mineralocorticoid receptor from smooth muscle cells did not significantly alter plaque area in males or females. Interestingly, female mice developed larger plaques than males in this model, a detail that underscores how sex shapes the disease even when the manipulation under study has no effect. But within each sex, the presence or absence of the receptor in vascular muscle made no difference to the size of the lesions.

Composition proved equally insensitive. Oil-Red-O staining, which highlights neutral lipids within the plaque, and the measurement of necrotic core area, the acellular debris that marks advanced, unstable lesions, showed no significant differences attributable to either sex or genotype. Masson’s Trichrome staining, which reveals collagen deposition and fibrosis, likewise detected no impact of the knockout on the fibrous content of the plaque. Immunofluorescent staining for smooth muscle alpha-actin, a marker of the vascular muscle population, and for Mac2, a galectin-3 marker of inflammatory myeloid cells, completed the picture. Neither marker shifted with the deletion of the receptor, and neither differed significantly between males and females in this early-disease setting.

The conclusion, stated plainly by the authors, is that in apolipoprotein E knockout mice fed a high-fat diet for eight weeks, deletion of the smooth muscle mineralocorticoid receptor does not influence traditional cardiovascular risk factors, plaque size or plaque composition in early atherosclerosis in either sex. This is not a trivial negative. It rules out one specific cellular pathway with the precision that only a cell-type-specific genetic approach can provide, and it does so across both sexes in a field where sexual dimorphism has repeatedly complicated extrapolation from male data to the whole population.

What the finding does not rule out is equally important. The study examined early lesions after eight weeks of dietary challenge; the receptor might still act on smooth muscle cells in advanced disease, where plaques remodel, calcify and depend on vascular muscle behavior for stability. The manipulation was also confined to a single cell type. The cumulative evidence now points away from vascular muscle and toward the endothelium and myeloid cells as the sites where mineralocorticoid signaling drives atherogenesis, at least in males. For female biology, the picture is murkier still, since the endothelial and myeloid effects themselves disappear in females, and the present study confirms that smooth muscle does not compensate for that absence. Elevated aldosterone in obesity may therefore harm the artery through mechanisms that lie outside the smooth muscle compartment, or through receptor-independent actions that no genetic deletion of the receptor can reveal. Dissecting those alternatives is the task the field now faces, armed with a cleaner map of where the receptor does not matter.

Subject of Research: Cell-type-specific deletion of the smooth muscle mineralocorticoid receptor does not alter early atherosclerotic plaque size or composition in male or female ApoE-knockout mice

Article Title: Smooth muscle cell mineralocorticoid receptor does not contribute to atherosclerosis in male or female ApoE-knockout mice

Article References: Svedberg, N. L., An, W., Tan, S., & Jaffe, I. Z. (2026). Smooth muscle cell mineralocorticoid receptor does not contribute to atherosclerosis in male or female ApoE-knockout mice. PLOS One, 21(10), e0360618. https://doi.org/10.1371/journal.pone.0360618

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360618

Keywords: atherosclerosis, mineralocorticoid receptor, aldosterone, smooth muscle cells, sex differences, ApoE-knockout mice, cardiovascular disease, PLOS One, Smooth, muscle, cell, mineralocorticoid