Multiomics reveals SYNPO2/VNN1 target and microbiota vaccine for atherosclerosis

In a finding that could reshape how scientists think about the links between gut bacteria, hormones and heart disease, an international team of researchers has identified a specific molecular pathway connecting the gut microbiome to the development of atherosclerosis, the artery-clogging process behind most heart attacks and strokes. The study, led by teams at Nanjing Medical University in China and Yokohama City University in Japan, went further than most microbiome research: rather than stopping at associations, the investigators built a causal argument using human genetics, tested it with advanced single-cell analysis of human tissue, and then translated the results into a working vaccine that slashed arterial plaque in mice by roughly 40 percent.

The research, published in the Journal of Translational Medicine, addresses one of the most persistent frustrations in cardiology. Decades of studies have shown that people with atherosclerosis tend to have altered gut microbial communities, but correlation is not causation, and the field has struggled to identify which specific bacteria matter, which host cells they influence, and how the interaction could be targeted therapeutically. Traditional therapies for atherosclerosis focus almost exclusively on lowering cholesterol, yet many patients continue to suffer cardiovascular events even when their lipid levels are well controlled. The new work suggests an entirely different lever: protecting the body’s own vasoprotective hormones from bacterial degradation.

To establish causality, the team began with bidirectional Mendelian randomization, a statistical technique that uses naturally occurring genetic variants as proxies to test whether one trait genuinely influences another. Because genetic variants are randomly allocated at conception, this approach largely sidesteps the confounding and reverse-causation problems that plague observational studies. Drawing on large-scale genome-wide association study data from resources including the UK Biobank and the GWAS Catalogue, the researchers examined whether genetically predicted variation in gut microbial taxa influenced atherosclerosis risk, and whether the reverse relationship held. The analysis identified 38 microbial taxa with credible causal links to the disease: 14 that appear to increase risk and 24 that appear protective. Crucially, the reciprocal analysis supported the causal direction, and sensitivity tests for heterogeneity, pleiotropy and directionality were reported in the study’s extensive supplementary materials.

With candidate bacteria in hand, the team turned to transcriptomics to identify which genes in human tissue respond to atherosclerotic disease. By integrating bulk RNA sequencing data from atherosclerotic and healthy vascular samples with single-cell RNA sequencing data that resolves gene expression in individual cells, the investigators homed in on two endothelial genes with striking, opposing behavior. SYNPO2, a gene encoding synaptopodin 2, an actin-associated protein involved in cytoskeletal organization and cell differentiation, was consistently downregulated as atherosclerosis progressed. VNN1, which encodes vanin-1, a pantetheinase enzyme tied to oxidative stress and inflammatory signaling, was upregulated. The pattern was not uniform across the vasculature’s many cell types: single-cell analysis positioned endothelial cells as the central mediators of the disease process, with SYNPO2 dominating the early differentiation programs of endothelial cells and VNN1 driving the inflammatory states characteristic of late-stage disease.

The single-cell work revealed a level of architectural detail that bulk sequencing cannot provide. The researchers identified 16 distinct cell clusters in their integrated data, annotated them using canonical markers, and found that endothelial cells were significantly depleted in atherosclerotic samples compared with controls. Cell-cell communication analysis mapped the ligand-receptor conversations taking place between macrophages, vascular smooth muscle cells and endothelial cells, identifying interaction pairs such as SPP1 signaling between macrophages and vascular smooth muscle cells in diseased tissue. Immune infiltration analysis showed that 27 of 28 scored immune cell types were present at significantly higher levels in atherosclerotic samples, and the investigators observed that SYNPO2 expression correlated positively with immature dendritic cells and myeloid-derived suppressor cells, while VNN1 showed a negative correlation with those populations.

Drug screening against the SYNPO2/VNN1 axis produced an unexpected result: estradiol and progesterone emerged as dual-target agents capable of favorably modulating both genes. Estradiol, the primary female sex hormone, has long been suspected of protecting premenopausal women from atherosclerosis through effects on endothelial function, lipid metabolism and inflammation, though the mechanistic picture has remained murky. The new study supplied a missing piece of the puzzle: when the researchers examined Klebsiella aerogenes, one of the microbial taxa flagged by the Mendelian randomization analysis, they found that the bacterium can degrade atheroprotective estradiol. In other words, a specific gut organism may actively strip the bloodstream of a hormone the vascular system depends on, quietly accelerating arterial disease.

That mechanistic insight pointed directly at a therapeutic strategy. Rather than attempting to wipe out gut bacteria with broad-spectrum antibiotics, an approach known to cause collateral damage to beneficial microbes and to fuel resistance, the team developed a vaccine targeting K. aerogenes itself. They tested the vaccine in apolipoprotein E knockout mice, a standard model in which animals fed a high-fat diet develop extensive atherosclerotic plaques resembling those seen in human disease. The results were striking. Vaccinated mice preserved higher serum estradiol levels, showed reduced aortic plaque burden by approximately 40 percent, and displayed improved lipid profiles compared with unvaccinated controls. Importantly, sequencing-based assessments of gut microbial diversity indicated that the vaccine did not broadly disrupt the overall microbial community, suggesting the intervention was targeted rather than scorched-earth.

Molecular confirmation followed. Immunohistochemistry of aortic root sections showed that vaccinated mice had significantly higher SYNPO2 expression and lower VNN1 expression in their vessel walls than controls, mirroring the protective molecular signature identified in the human data. Serum analyses revealed significantly lower IgG3 levels in vaccinated animals, a marker the authors link to reduced systemic inflammatory signaling. Correlation analyses between serum estradiol and aortic protein expression showed a positive trend with SYNPO2 and a significant negative relationship with VNN1, tying the hormonal, microbial and endothelial strands of the story together into a single coherent axis. The animal work was approved by the Animal Care and Use Committee of Nanjing Medical University under protocol IACUC-1909031, and no new human subjects were recruited; all human data came from publicly available, approved resources.

The authors frame their findings as the definition of a gut-microbiome-immune-endothelial axis in atherosclerosis: dysbiosis in the gut erodes levels of vasoprotective estradiol, which in turn destabilizes the SYNPO2/VNN1 balance in endothelial cells, pushing them away from healthy differentiation and toward inflammatory dysfunction that promotes plaque formation. The K. aerogenes-targeted vaccine, in this model, acts as a precision tool that preserves the hormone and restores the endothelial equilibrium without disturbing the wider microbial ecosystem. If the concept survives further testing, it would represent a genuinely novel class of cardiovascular intervention, one aimed at the microbiome rather than at cholesterol, blood pressure or clotting.

Independent experts caution, as they always do with mouse studies, that the distance from apolipoprotein E knockout mice to human patients is long, and that microbiome-targeted vaccines raise questions about strain specificity, immune safety and whether a vaccine designed against one organism will help patients whose dysbiosis involves different microbial culprits. The Mendelian randomization findings themselves, while methodologically sophisticated, depend on the quality and power of the underlying genome-wide association data for microbial taxa, which remain works in progress. Nevertheless, the study’s translational arc, from genetic causal inference through single-cell mechanistic discovery to a validated intervention in disease models, is unusually complete, and it offers a template for how microbiome science might finally deliver on its long-promised clinical payoff. The research was supported by the National Natural Science Foundation of China, JSPS KAKENHI and several regional science foundations, and the work is published open access under a Creative Commons license.