No abstract

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.

There is conflicting evidence regarding inheritance of hemochromatosis gene (HFE) mutations and influence of hepatic iron deposition as cofactors for development of fibrosis in patients with nonalcoholic steatohepatitis (NASH). We studied hepatic iron content (Perls' stain grade), frequency of HFE mutations, and serum iron indices in 93 patients with NASH from a multiethnic background; 59 (63%) were of Anglo-Celtic origin. Data on C282Y mutations were available for all 93 patients and on H63D for 69 patients. Respective controls were 206 (for C282Y, 141 [69%] of whom were Anglo-Celtic) and 180 (for H63D) blood donors. Hyperferritinemia was present in 38 patients (40%) with NASH, but transferrin saturation was increased (>55%) in only 5 (5%). Liver biopsy specimens showed advanced fibrosis in 31 (33%) (cirrhosis in 20%). Altogether, 9 biopsy specimens (10%) showed increased iron: 7 (8%) with grade 2 and 2 (2%) with grade 3 iron staining. Only 1 biopsy specimen with increased iron showed advanced fibrosis. The frequency of C282Y heterozygosity was increased in Anglo-Celtic patients with NASH compared with ethnic blood donor controls (22% vs. 9.2%; P ‫؍‬ .035); there were no C282Y homozygotes in the NASH cohort. Although there was a trend toward higher serum ferritin levels among C282Y heterozygotes with NASH, there were no differences in histologic grades of steatosis, inflammation, or fibrosis between individuals with and without C282Y. The frequencies of compound C282Y/H63D heterozygotes (n ‫؍‬ 1) or H63D heterozygotes (n ‫؍‬ 10) were not increased in NASH. Multivariate analysis identified female sex, diabetes mellitus, and more severe liver inflammation but not HFE mutations, serum ferritin, iron saturation, or hepatic iron staining as independent predictors of hepatic fibrosis. In conclusion, hepatic iron is not a factor linked to hepatic fibrogenesis in patients with NASH. HFE mutations do not confer an additional risk of hepatic fibrosis in this disorder. (HEPATOLOGY 2002;36:142-149.)