Cerebral cavernous malformations form an anticoagulant vascular domain in humans and mice

Abstract

Cerebral cavernous malformations (CCMs) are common brain vascular dysplasias that are 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 hemorrhage in CCMs 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, as well as in the plasma of patients with CCMs. In mice, endothelial-specific genetic inactivation of Krit1 (Krit1ECKO) or Pdcd10 (Pdcd10ECKO), which cause CCM formation, results in increased levels of vascular TM and EPCR, as well as 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 1 or 2 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 cofactors that generate anticoagulant APC can contribute to bleeding in CCMs, and plasma soluble TM may represent a biomarker for hemorrhagic risk in CCMs.

Mapping endothelial-cell diversity in cerebral cavernous malformations at single-cell resolution

“…The expression of typical lesion markers Klf4 , Ly6a , and Thbd ( Maddaluno et al, 2013 ; Lopez-Ramirez et al, 2019 ) was higher for the Pdcd10 -ko cells specific to the S0–S2 and S3–S0 branches, even if not exclusively limited to these branches ( Figure 6D ).…”

Pharmacological inhibition of the heart of glass (HEG1)-Krev interaction trapped protein 1 (KRIT1) protein complex increases Krüppel-like Factors 4 and 2 (KLF4/2) expression in endothelial cells

“…Moreover, HEG1 mutations have never been identified in human CCM and deletion of HEG1 in mice does not cause CCM (1). Here we developed a method for pharmacological inhibition of the HEG1-KRIT1 protein-protein interaction and found the predicted upregulation of KLF4 and KLF2 gene expression, and expected effects on some of their target genes such as THSP1 and THBD, as we previously observed with knockdown of KRIT1 in EC (9,29). Moreover, KLF4/2 were upregulated within 4 hr of drug addition, a time long before acute genetic inactivation of Krit1 would do so.…”

“…Many of the effects of pulsatile sheer stress (PS) are due to upregulation of transcription factors KLF4 and KLF2, which in turn can increase expression of genes that encode anticoagulant cofactors (e.g., THBD encoding thrombomodulin, TM) and suppress expression of genes that antagonize angiogenesis (e.g.,THBS1 encoding thrombospondin1, TSP1). Thus, PS can upregulate KLF4/2 in endothelium and their important transcriptional targets (9,(24)(25)(26)(27)(28)(29).…”

Cavernous angiomas: deconstructing a neurosurgical disease

“…65,93 Other signaling aberrations involve dysangiogenesis; 46,107 endothelial-mesenchymal transition; 60 proinflammatory state, oxidative stress, and autophagy; 70,76 loss of TSP1; 56 and thrombomodulinassociated local anticoagulant domains. 57 Lesion development is also driven by lipid polysaccharide signaling through CD14/TLR4 receptors on brain microvascular ECs, and this has been related to a robust impact of gramnegative bacteria in the gut microbiome on lesion development. 97 Heterozygous CCM mutations have been correlated with increased vascular permeability in the skin, lung, and brain, 93,103 even in the absence of lesions, which has been confirmed in humans.…”