MON-475 - Functional polarity in aldosterone-producing nodules by spatial transcriptomics analysis

[Objective]
Aldosterone-producing nodules (APNs), one of the major causes of primary aldosteronism, are characterized by a gradient of aldosterone synthase (CYP11B2) expression within the nodule. This spatial heterogeneity suggests functional compartmentalization; however, the molecular mechanisms underlying the fine architecture and polarity of APNs remain poorly understood.
[Methods]
Adrenal tissue containing an APN was obtained from a surgical specimen of a patient with aldosterone-producing adenoma. Comprehensive analyses including histopathological evaluation, whole-exome sequencing, and spatial transcriptomics (ST) were performed. ST data were integrated with histological findings to accurately localize APN regions, followed by unsupervised clustering, differential gene expression analysis, and pathway enrichment analysis.
[Results]
Whole-exome sequencing identified a KCNJ5 mutation in the APN, consistent with known driver mutations in aldosterone-producing adenomas. ST analysis integrating gene expression profiles with spatial information enabled precise identification of APN regions. Unsupervised clustering revealed that the APN was clearly divided into two distinct clusters: an outer layer (s-APN) and an inner layer (d-APN), indicating spatially organized cellular heterogeneity. Differential expression analysis demonstrated that genes involved in aldosterone biosynthesis, including key steroidogenic enzymes, were significantly upregulated in s-APN. In contrast, genes associated with cortisol biosynthesis and adrenal androgen synthesis pathways were significantly enriched in d-APN. Pathway analysis further showed that s-APN was characterized by upregulation of genes involved in de novo cholesterol biosynthesis, particularly the mevalonate pathway, suggesting enhanced substrate supply for steroidogenesis. In addition, transcription factor activity analysis indicated activation of SREBF2 in s-APN, implying a regulatory role in cholesterol metabolism and aldosterone production within this compartment.
[Conclusion]
These findings suggest that APNs exhibit spatial polarity and are composed of functionally distinct cellular populations with differential steroidogenic programs. The outer layer appears specialized for aldosterone production supported by enhanced cholesterol biosynthesis, whereas the inner layer shows features of alternative steroidogenic lineages. Further investigations are required to clarify the mechanisms that establish and maintain this functional polarity and to determine its clinical significance in primary aldosteronism.

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