Wnt7a Decreases Brain Endothelial Barrier Function Via β-Catenin Activation

The blood-brain barrier is a specialized structure that shields the brain from harmful substances in the bloodstream. This barrier is formed by endothelial cells connected by tight junction proteins like Claudin-5 and Occludin. Prior research has shown that these proteins help maintain barrier integrity. However, disruptions in this system may lead to neurological complications. The Wnt/β-catenin pathway is known to influence cell adhesion and permeability. That uncertainty drove this study to explore how Wnt7a affects endothelial barrier function. No prior work had resolved the role of Wnt7a in modulating tight junctions. This gap motivated the investigation into the signaling mechanisms involved. Understanding these pathways could help clarify how barrier dysfunction occurs. Researchers aimed to determine whether Wnt7a alters barrier integrity through β-catenin.

This study aimed to evaluate the effects of Wnt7a on endothelial cell barrier function in vitro. The researchers wanted to determine whether Wnt7a influences tight junction proteins like Claudin-5 and Occludin. They also sought to clarify the role of β-catenin in this process. The motivation for this study came from the known involvement of Wnt signaling in cell adhesion. The team wanted to test whether Wnt7a leads to barrier disruption. They also investigated the potential involvement of the Wnt/HIF1α pathway. The study focused on mouse brain endothelial cells as a model system. By modulating Wnt/β-catenin signaling, the researchers aimed to observe changes in barrier integrity.

The researchers used mouse brain endothelial cells (bEnd.3) to model the blood-brain barrier. They treated the cells with recombinant Wnt7a protein to activate the Wnt/β-catenin pathway. XAV939, a selective inhibitor of Wnt/β-catenin transcription, was used to block this pathway. To assess the role of HIF1α, the team used Hif1α siRNA to inhibit its signaling. They measured β-catenin activation and nuclear translocation using immunofluorescence. Claudin-5 and Occludin expression levels were analyzed via Western blot. Barrier integrity was evaluated using transendothelial electrical resistance. The study also examined changes in Hif1α and Vegfa expression levels.

Wnt7a treatment caused β-catenin activation and its translocation to the nucleus. This effect was blocked by XAV939, confirming the role of β-catenin in the pathway. Claudin-5 expression decreased following Wnt7a stimulation, which was mediated by β-catenin. Endothelial barrier formation was reduced under Wnt7a treatment. Hif1α and Vegfa expression levels increased after Wnt7a exposure. However, Hif1α signaling did not affect Claudin-5 or Occludin expression. The data suggest that Wnt7a reduces barrier integrity via β-catenin. This mechanism may contribute to endothelial cell proliferation and angiogenesis.

The study suggests that Wnt7a decreases endothelial barrier function through β-catenin activation. This process may lead to reduced Claudin-5 expression and impaired barrier formation. The findings indicate that Wnt7a could play a role in endothelial cell proliferation. The researchers propose that this mechanism might be involved in angiogenesis. Hif1α signaling did not regulate tight junction proteins in this model. However, it may still contribute to brain angiogenesis. The study highlights the potential role of Wnt/HIF1α signaling in disease processes. These results could inform future research on blood-brain barrier dysfunction.