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Introduction: Previously, murine models Ccm1+/-Msh2-/- and Ccm2+/-Trp53-/- showed a reduction or no effect on cerebral cavernous malformation (CCM) burden and favorable effects on lesional hemorrhage by RhoA kinase (Rock) inhibitor fasudil and by simvastatin (with weak pleiotropic Rock inhibition effect). Herein we investigated treatment of the more aggressive Ccm3/Pdcd10 model with these drugs, and higher dose and intensity atorvastatin, and determined which Rock isoform is involved in CCM development and hemorrhage.Hypothesis: Rock inhibition blocks CCM burden in Ccm3 models, through Rock1 or Rock2 isoforms.Methods: The murine model Ccm3+/-Trp53-/- was concurrently treated from weaning to 5 months of age with fasudil (100 mg/kg/day in drinking water, n=7), simvastatin (40 mg/kg/day in chow, n=8), atorvastatin (80 mg/kg/day in chow, n=7) or with placebo (n=10). We assessed CCM volume in mouse brains by micro-computed tomography. We then concurrently bred Rock1+/+ (n=15) and Rock1+/- (n=17), Rock2+/+ (n=17) and Rock2+/- (n=15) mice with Ccm3+/-mice and assessed respective lesion burden. We further analyzed chronic hemorrhage in CCM lesions by intensity of Perl staining in brain sections.Results: In the Ccm3+/-Trp53-/- model, mean CCM lesion volume/brain volume (X 103) per mouse decreased from 12.2 in placebos to 2.5 (p=0.002) by fasudil, and to 3.0 (p=0.002) by atorvastatin treatment, but was not changed significantly by simvastatin. CCM lesion volume/brain volume (x 106) per mouse decreased from 19.6 in Ccm3+/-Rock2+/+ to 2.3 (p=0.011) in Ccm3+/-Rock2+/- animals, and not significantly in Ccm3+/-Rock1+/ mice. Hemorrhage intensity per brain was commensurately decreased by Rock 2 but not Rock1 transheterozygocity.Conclusion: CCM lesion development was inhibited by fasudil and atorvastatin but not lower dose and intensity simvastatin therapy. The benefit of Rock inhibition on lesion development and blunting of hemorrhage resulted from effects through Rock2, predominantly expressed in heart and brain, but not Rock1 isoform.