The aberrant expression or alternation of miRNA in the pathogenesis of aldosterone-producing adenomas (APAs) is still largely unknown.

We investigated the role of miRNA-203 (screened from miRNA microarrays) and elucidated its effects on the Wnt/β-catenin pathway regarding aldosterone production and cell proliferation in APAs.

miR-203 expression was upregulated or downregulated by transfecting miR-203 mimics or inhibitors into primary APA cells, the human adrenocortical cell line HAC15, and C57BL/6 mice. In vitro and biochemical data were correlated with the respective clinical parameters of APAs to evaluate their clinical importance.

The expression of miR-203 in human APA samples was significantly lower than that of peritumor adrenal samples. Tumoral miR-203 abundance correlated negatively with both plasma aldosterone level and tumor size in patients with APAs. miR-203 inhibitors increased aldosterone production and cell proliferation in HAC15 cells, and restoration of expression via miR-203 mimics showed decreased cell proliferation and aldosterone hypersecretion in APA cell cultures. In vivo selective inhibition of miR-203 via intra-adrenal injection of miR-203 inhibitors in mice led to a substantial increase in systolic blood pressure and plasma aldosterone levels. Additionally, the dual-luciferase reporter assay demonstrated that WNT5A is a direct target of miR-203. Furthermore, plasma Wnt5a levels in adrenal vein sampling were helpful in differentiating tumor localization, and preoperative plasma Wnt5a levels predicted the cure of hypertension after adrenalectomy.

We have demonstrated that attenuated miR-203 expression in APAs increases aldosterone production and the tumorigenesis of adrenal cells by activating the Wnt5a/β-catenin pathway.