Β-­CATENIN SIGNALING IN CCM3 NULL ENDOTHELIAL CELLS CONTRIBUTES TO CEREBRAL CAVERNOUS MALFORMATION PATHOLOGY

Cerebral cavernous malformation (CCM) is a vascular disease that affects blood vessels in the central nervous system, which become malformed, leaky and prone to hemorrhage. The organ location is critical, both for neurological consequences and therapeutic intervention, which is exclusively surgical to date. The cause of CCM can be either sporadic or genetic. Mutations in three genes named CCM1/Krit1, CCM2/Malcavernin and CCM3/Pdcd10 are associated with hereditary CCM. Here we describe a novel murine model of the disease that develops after endothelial cell-selective ablation of the CCM3 gene in newborn mice and that we use to investigate the molecular mechanisms behind the development of CCM. We report enhanced transcription activity of β-catenin in CCM3-knockout endothelial cells in in vitro and in vivo models and we demonstrate that such activation is critical at early stage of the pathology development. In particular, we found that β-catenin is fundamental to trigger the process of endothelial-to-mesenchymal transition (EndMT), which has been previously demonstrated to be crucial for CCM development. Noteworthy, the activation of β-catenin pathway results Wnt-independent, while it correlates with the impaired state of endothelial cell-to-cell junctions typical of vessels developing CCM lesions. We also show that a pharmacological screening of a panel of drugs targeting β-catenin signaling revealed the NSAIDs sulindac sulfide and sulindac sulfone as potent inhibitors of this signaling pathway in endothelial cells. Moreover, we found that sulindac sulfide and sulindac sulfone are able to attenuate β-catenin transcription activity and to significantly reduce the number and dimension of vascular lesions in the central nervous system of mice with endothelial cell-specific CCM3-knockout. These NSAIDs thus represent pharmacological tools for inhibition of the formation of CCM3 vascular lesions, particularly with a view to patients affected by the genetic variant of CCM, who continue to develop new malformations over time.