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Cerebral cavernous malformations form an anticoagulant vascular domain

Miguel Alejandro Lopez-Ramirez, Angela Pham, Romuald Girard, Tine Wyseure, Preston Hale, Atsuki Yamashita, Janne Koskimäki, Sean Polster, Laleh Saadat, Ignacio A. Romero, Charles T. Esmon, Frederic Lagarrigue, Issam A. Awad, Laurent O. Mosnier and Mark H. Ginsberg

Key points

  • Increased levels of protein C activation co-factors form an anticoagulant vascular domain in cerebral cavernous malformations.

  • Plasma levels of soluble TM may represent a biomarker for CCM risk of hemorrhage.

Abstract

Cerebral cavernous malformations (CCM) are common brain vascular dysplasias prone to acute and chronic hemorrhage with significant clinical sequelae. The pathogenesis of recurrent bleeding in CCM is incompletely understood. Here we show that central nervous system (CNS) hemorrhage in CCM is associated with locally elevated expression of the anticoagulant endothelial receptors thrombomodulin (TM) and endothelial protein C receptor (EPCR). TM levels are increased in human CCM lesions and in the plasma of patients with CCMs. In mice, endothelial-specific genetic inactivation of Krit1 (Krit1ECKO) or Pdcd10 (Pdcd10ECKO), which cause CCM formation, result in increased levels of vascular TM and EPCR, and in enhanced generation of activated protein C (APC) on endothelial cells. Increased TM expression is due to upregulation of transcription factors KLF2 and KLF4 consequent to the loss of KRIT1 or PDCD10. Increased TM expression contributes to CCM hemorrhage, because genetic inactivation of one or two copies of the Thbd gene decreases brain hemorrhage in Pdcd10ECKO mice. Moreover, administration of blocking antibodies against TM and EPCR significantly reduced CCM hemorrhage in Pdcd10ECKO mice. Thus, a local increase in the endothelial co-factors that generate anticoagulant APC can contribute to bleeding in CCMs and plasma soluble TM may represent a biomarker for hemorrhagic risk in CCMs.

  • Submitted June 5, 2018.
  • Accepted October 31, 2018.