title: Alterations of retinal vasculature in cystathionine-Beta-synthase mutant mice, a model of hyperhomocysteinemia.
abstract: OBJECTIVE
  Mice with moderate/severe hyperhomocysteinemia due to deficiency or absence of the cbs gene encoding cystathionine-beta-synthase (CBS) have marked retinal disruption, ganglion cell loss, optic nerve mitochondrial dysfunction, and ERG defects; those with mild hyperhomocysteinemia have delayed retinal morphological/functional phenotype. Excess homocysteine is a risk factor for cardiovascular diseases; however, it is not known whether excess homocysteine alters retinal vasculature.
  
  
  METHODS
  Cbs(+/+), cbs(+/-), and cbs(-/-) mice (age ∼3 weeks) were subjected to angiography; retinas were harvested for cryosections, flat-mount preparations, or trypsin digestion and subjected to immunofluorescence microscopy to visualize vessels using isolectin-B4, to detect angiogenesis using anti-VEGF and anti-endoglin (anti-CD105) and activated glial cells (anti-glial fibrillary acidic protein [anti-GFAP]) and to investigate the blood-retinal barrier using the tight junction markers zonula occludens-1 (ZO-1) and occludin. Expression of vegf was determined by quantitative RT-PCR (qRT-PCR) and immunoblotting. Human retinal endothelial cells (HRECs) were treated with excess homocysteine to analyze permeability.
  
  
  RESULTS
  Angiography revealed vascular leakage in cbs(-/-) mice; immunohistochemical analysis demonstrated vascular patterns consistent with ischemia; isolectin-B4 labeling revealed a capillary-free zone centrally and new vessels with capillary tufts midperipherally. This was associated with increased vegf mRNA and protein, CD105, and GFAP in cbs(-/-) retinas concomitant with a marked decrease in ZO-1 and occludin. Homocysteine-treated HRECs showed increased permeability.
  
  
  CONCLUSIONS
  Severe elevation of homocysteine in cbs(-/-) mutant mice is accompanied by alterations in retinal vasculature (ischemia, neovascularization, and incompetent blood-retinal barrier). The marked disruption of retinal structure and decreased visual function reported in cbs(-/-) mice may reflect vasculopathy as well as neuropathy.
authors: Departments of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, USA.
authors: Amany
authors: A
authors: Tawfik
authors: Mohamed
authors: M
authors: Al-Shabrawey
authors: Penny
authors: P
authors: Roon
authors: Srinivas
authors: S
authors: Sonne
authors: Jason A
authors: JA
authors: Covar
authors: Surapoon
authors: S
authors: Matragoon
authors: Preethi S
authors: PS
authors: Ganapathy
authors: Sally S
authors: SS
authors: Atherton
authors: Azza
authors: A
authors: El-Remessy
authors: Vadivel
authors: V
authors: Ganapathy
authors: Sylvia B
authors: SB
authors: Smith
mesh_terms: D000818:Animals; D001813:Blood-Retinal Barrier / Q000378:metabolism / Q000503:physiopathology; D002199:Capillary Permeability; D003541:Cystathionine beta-Synthase / Q000172:deficiency / Q000235:genetics; D004195:Disease Models, Animal; D005451:Fluorescein Angiography; D005654:Fundus Oculi; D005786:Gene Expression Regulation; D006710:Homocysteine / Q000378:metabolism*; D020138:Hyperhomocysteinemia / Q000150:complications / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008817:Mice, Mutant Strains; D008856:Microscopy, Fluorescence; D012333:RNA, Messenger / Q000235:genetics*; D012160:Retina / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D012164:Retinal Diseases / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D006710:Homocysteine; D003541:Cystathionine beta-Synthase