Cell Study Links RNA Modification WTAP to KDR Protection in Aneurysm Model

A new cell-based study reports that a regulatory protein called WTAP can protect human brain microvascular endothelial cells from injury triggered by angiotensin II, a hormone used in the laboratory to mimic the cellular stress associated with intracranial aneurysms. The protection, described in Applied Biological Chemistry, depends on WTAP boosting the expression of KDR, the vascular endothelial growth factor receptor 2, through a chemical RNA modification known as m6A. The work was published on 7 October 2026 by researchers from the Affiliated Wuxi People’s Hospital of Nanjing Medical University.

Intracranial aneurysms are abnormal dilations of cerebral arteries that carry substantial risk: according to the paper’s introduction, severe disability occurs in roughly 30 percent of cases and death in 30 to 50 percent, particularly among people aged 40 to 60. Current treatment relies on surgical clipping or endovascular therapy, but the authors note that clinical outcomes with these approaches have been less than optimal, motivating a search for the underlying pathogenic mechanisms that might offer new targets.

The experimental system was deliberately simple. Primary human brain microvascular endothelial cells, obtained at passages 3 to 8 and confirmed to be mycoplasma-free, were exposed to 10⁻⁵ molar angiotensin II for 24 hours after an acclimatization period. This treatment served as an in vitro model of the hypertension-linked stress thought to contribute to aneurysm formation. The researchers then measured a battery of cellular endpoints: viability by cell counting kit-8 assay, apoptosis by flow cytometry with Annexin V and propidium iodide, mitochondrial membrane potential by JC-1 staining, reactive oxygen species by a DCFH-DA fluorometric assay, and reduced glutathione, malondialdehyde and ferrous iron by colorimetric assays. Each assay was run with three independent biological replicates.

The angiotensin II challenge produced a consistent pattern of damage. Treated cells showed reduced viability, increased apoptosis, a shift in mitochondrial membrane potential indicated by a higher JC-1 green fluorescence rate, elevated reactive oxygen species and ferrous iron, increased malondialdehyde, and depleted glutathione. The authors interpret this combined phenotype as an aneurysm-like injury state in cultured endothelium, while acknowledging that cultured cells cannot reproduce the full hemodynamic and multicellular environment of a living aneurysm.

A parallel clinical observation anchored the mechanistic work. The team enrolled 23 patients with intracranial aneurysms identified by digital subtraction angiography and excised aneurysm wall specimens during neurosurgery, snap-freezing them within 30 minutes of resection. Control vessels were macroscopically normal middle meningeal arteries harvested from trauma patients undergoing hematoma evacuation, matched to the aneurysm group in age and sex, with a mean patient age of 57.4 years. Quantitative PCR showed that KDR messenger RNA was significantly downregulated in aneurysm wall tissue compared with controls, and western blotting confirmed reduced KDR protein. KDR expression was also low in angiotensin II-treated cells. The authors point out that this finding contrasts with an earlier report of moderate KDR expression in aneurysm walls, but they argue that the earlier study rested on only six unruptured aneurysms and two controls, whereas their cohort of 23 patients provides stronger statistical support for downregulation.

To test whether restoring KDR matters functionally, the researchers transfected cells with a KDR overexpression plasmid before the angiotensin II exposure. Overexpression was efficient by western blot, and it measurably blunted the damage: cell viability recovered, apoptosis fell, the JC-1 green fluorescence rate declined, malondialdehyde, reactive oxygen species and ferrous iron dropped, and glutathione levels rebounded. In other words, ectopic KDR expression counteracted apoptosis, oxidative stress and ferroptosis in this cell model. The authors frame this as an endothelial-specific protective role for KDR, distinct from prior literature that had linked the receptor mainly to smooth muscle cell proliferation and vascular remodeling.

The mechanistic core of the paper concerns WTAP, a component of the m6A methyltransferase complex. The m6A modification, the addition of methyl groups to adenosine bases in RNA, is written by methyltransferase complexes, removed by demethylases and interpreted by binding proteins that shape RNA metabolism. Using the SRAMP prediction database, the team identified putative m6A sites on KDR messenger RNA and then tested them experimentally. A methylated RNA immunoprecipitation assay showed that m6A levels on the KDR transcript fell when WTAP was silenced. A dual-luciferase reporter assay strengthened the case: luciferase activity from the wild-type KDR reporter dropped when WTAP was knocked down, while a mutant reporter was unaffected, indicating that the effect depended on the predicted modification sites. An actinomycin D chase experiment added a kinetic layer, showing that the half-life of KDR messenger RNA shortened after WTAP knockdown, and western blots confirmed that KDR protein fell with WTAP silencing and rose with WTAP overexpression. WTAP itself was downregulated in aneurysm wall tissues and in angiotensin II-treated cells.

The final functional test tied the axis together. Cells received a WTAP overexpression plasmid, with or without a short hairpin RNA against KDR, before angiotensin II exposure. WTAP overexpression alone again protected the cells, restoring viability, reducing apoptosis, and normalizing the mitochondrial, oxidative and ferroptosis markers. But when KDR was simultaneously knocked down, that protection largely disappeared. The authors conclude that WTAP shields endothelial cells from angiotensin II-induced injury specifically by upregulating KDR in an m6A-dependent manner, delineating what they call a previously unrecognized WTAP/m6A/KDR pathway in aneurysm pathogenesis. They also contrast their findings with work in abdominal aortic aneurysm, where WTAP was reported to be highly expressed and to act through the unrelated target BASP1, underscoring that aneurysm mechanisms may differ by vascular bed.

The paper’s conclusion suggests that targeting the WTAP-KDR axis could have clinical implications for preventing and treating intracranial aneurysms, but the authors themselves list the limits of that leap. The mechanistic insights come entirely from an in vitro model that may not recapitulate the complex hemodynamic and multicellular microenvironment of aneurysms in vivo. Other m6A regulators such as METTL3 and FTO were not explored, so compensatory or synergistic pathways remain unknown. Clinical data were limited to expression profiling in resected tissue, and dynamic changes in WTAP and KDR during aneurysm progression or rupture have yet to be assessed. No efficacy results in patients exist; what the study establishes is a molecular relationship in cultured human endothelial cells and a consistent expression pattern in 23 aneurysm specimens, a foundation that any future therapeutic work would need to build on with animal models and clinical studies.

Subject of Research: WTAP-mediated m6A regulation of KDR in angiotensin II-treated human brain microvascular endothelial cells as a model of intracranial aneurysm injury

Article Title: WTAP-induced upregulation of KDR ameliorates angiotensin II-induced apoptosis, oxidative stress and ferroptosis of human brain microvascular endothelial cells

Article References: Shao, Y., Yang, Z., Pu, Y., Yu, X., & Miao, W. (2026). WTAP-induced upregulation of KDR ameliorates angiotensin II-induced apoptosis, oxidative stress and ferroptosis of human brain microvascular endothelial cells. Applied Biological Chemistry, 69(1), Article 74. https://doi.org/10.1186/s13765-026-01140-y

Image Credits: AI Generated

DOI: 10.1186/s13765-026-01140-y

Keywords: intracranial aneurysm, WTAP, KDR, m6A modification, ferroptosis, endothelial cells, angiotensin II, oxidative stress, apoptosis, human brain microvascular endothelial cells, RNA methylation, vascular biology