Cerebral cavernous malformations (CCMs) are vascular lesions of the central nervous system appearing as multicavernous, blood-filled capillaries, leading to headache, seizure and hemorrhagic stroke. CCM occurs either sporadically or as an autosomal dominant disorder caused by germline mutation of one of the three genes: CCM1/KRIT1, CCM2/MGC4607 and CCM3/PDCD10. Surgically resected human CCM lesions have provided molecular and immunohistochemical evidence for a two-hit (germline plus somatic) mutation mechanism. In contrast to the equivalent human genotype, mice heterozygous for a Ccm1- or Ccm2-null allele do not develop CCM lesions. Based on the two-hit hypothesis, we attempted to improve the penetrance of the model by crossing Ccm1 and Ccm2 heterozygotes into a mismatch repair-deficient Msh2(-/-) background. Ccm1(+/-)Msh2(-/-) mice exhibit CCM lesions with high penetrance as shown by magnetic resonance imaging and histology. Significantly, the CCM lesions range in size from early-stage, isolated caverns to large, multicavernous lesions. A subset of endothelial cells within the CCM lesions revealed somatic loss of CCM protein staining, supporting the two-hit mutation mechanism. The late-stage CCM lesions displayed many of the characteristics of human CCM lesions, including hemosiderin deposits, immune cell infiltration, increased endothelial cell proliferation and increased Rho-kinase activity. Some of these characteristics were also seen, but to a lesser extent, in early-stage lesions. Tight junctions were maintained between CCM lesion endothelial cells, but gaps were evident between endothelial cells and basement membrane was defective. In contrast, the Ccm2(+/-)Msh2(-/-) mice lacked cerebrovascular lesions. The CCM1 mouse model provides an in vivo tool to investigate CCM pathogenesis and new therapies.

Purpose The phenotypic manifestations of cerebral cavernous malformation (CCM) disease caused by rare PDCD10 mutations have not been systematically examined, and a mechanistic link to Rho kinase (ROCK) mediated hyperpermeability, a potential therapeutic target, has not been established. Methods We analyze PDCD10-siRNA treated endothelial cells for stress fibers, ROCK activity and permeability. ROCK activity is assessed in CCM lesions. Brain permeability and CCM lesion burden is quantified, and clinical manifestations are assessed in prospectively enrolled subjects with PDCD10 mutations. Results We determine that PDCD10 protein suppresses endothelial stress fibers, ROCK activity and permeability in vitro. Pdcd10 heterozygous mice have greater lesion burden than other Ccm genotypes. We demonstrate robust ROCK activity in murine and human CCM vasculature, and increased brain vascular permeability in humans with PDCD10 mutation. Clinical phenotype is exceptionally aggressive compared to the more common KRIT1 and CCM2 familial and sporadic CCM, with greater lesion burden and more frequent hemorrhages earlier in life. We first report other phenotypic features including scoliosis, cognitive disability and skin lesions, unrelated to lesion burden or bleeding. Conclusion These findings define a unique CCM disease with exceptional aggressiveness, and they inform preclinical therapeutic testing, clinical counseling and the design of trials.

Background and Purpose Cerebral cavernous malformations (CCMs) are characterized by grossly dilated capillaries, associated with vascular leak and hemorrhage, and occur in sporadic or inherited (autosomal dominant) forms with mutations in one of three gene loci (CCM 1, 2 or 3). We previously reported that the CCM1 protein (KRIT1) localizes to endothelial cell-cell junctions and loss of KRIT1 leads to junctional instability associated with activation of RhoA and its effector Rho kinase (ROCK). Although ROCK inhibition has been proposed as potential therapy for CCM, there has been no demonstration of a therapeutic effect on CCM lesion genesis in vivo. Methods Our recently generated a model of CCM1 disease (Ccm1+/−Msh2−/−) was treated with ROCK inhibitor fasudil (100 mg/kg/day administered in drinking water from weaning to 5 months of age), or placebo, and blindly assessed CCM lesion burden by systematic survey of animals’ brains. For comparison, we also assessed therapeutic effect in previously described Ccm2+/−Trp53−/− mice, treated with the same dose and duration of fasudil and placebo. Results Fasudil treated Ccm1+/−Msh2−/− mice had a significantly decreased prevalence of CCM lesions compared to placebo controls. Lesions in treated animals were smaller and less likely associated with hemorrhage, inflammation and endothelial proliferation, and exhibited decreased expression of ROCK activation biomarkers. A therapeutic effect was also documented in Ccm2+/−Trp53−/− mice. Conclusion This represents the first report of therapeutic benefit of pharmacological therapy in development and progression of CCMs, and indicates that ROCK activation is a critical step in CCM lesion genesis and maturation.