title: Local production of the alternative pathway component factor B is sufficient to promote laser-induced choroidal neovascularization.
abstract: OBJECTIVE
  Complement factor B (CFB) is a required component of the alternative pathway (AP) of complement, and CFB polymorphisms are associated with age-related macular degeneration (AMD) risk. Complement factor B is made in the liver, but expression has also been detected in retina and retinal pigment epithelium (RPE)-choroid. We investigated whether production of CFB by the RPE can promote AP activation in mouse choroidal neovascularization (CNV).
  
  
  METHODS
  Transgenic mice expressing CFB under the RPE65 promoter were generated and crossed onto factor B-deficient (CFB-KO) mice. Biological activity was determined in vitro using RPE monolayers and in vivo using laser-induced CNV. Contribution of systemic CFB was investigated using CFB-KO reconstituted with CFB-sufficient serum.
  
  
  RESULTS
  Transgenic mice (CFB-tg) expressed CFB in RPE-choroid; no CFB was detected in serum. Cultured CFB-tg RPE monolayers secreted CFB apically and basally upon exposure to oxidative stress that was biologically active. Choroidal neovascularization sizes were comparable between wild-type and CFB-tg mice, but significantly increased when compared to lesions in CFB-KO mice. Injections of CFB-sufficient serum into CFB-KO mice resulted in partial reconstitution of systemic AP activity and significantly increased CNV size.
  
  
  CONCLUSIONS
  Mouse RPE cells express and secrete CFB sufficient to promote RPE damage and CNV. This further supports that local complement production may regulate disease processes; however, the reconstitution experiments suggest that additional components may be sequestered from the bloodstream. Understanding the process of ocular complement production and regulation will further our understanding of the AMD disease process and the requirements of a complement-based therapeutic.
authors.affiliation: Research Service, Ralph H. Johnson VA Medical Center, Charleston, South Carolina, United States.
authors.forename: Gloriane
authors.initials: G
authors.lastname: Schnabolk
authors.affiliation: Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, United States.
authors.forename: Beth
authors.initials: B
authors.lastname: Coughlin
authors.affiliation: Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, United States.
authors.forename: Kusumam
authors.initials: K
authors.lastname: Joseph
authors.affiliation: Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, United States.
authors.forename: Kannan
authors.initials: K
authors.lastname: Kunchithapautham
authors.affiliation: Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, United States.
authors.forename: Mausumi
authors.initials: M
authors.lastname: Bandyopadhyay
authors.affiliation: Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, United States.
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: O'Quinn
authors.affiliation: Department of Medicine, Division of Rheumatology and Immunology, Medical University of South Carolina, Charleston, South Carolina, United States.
authors.forename: Tamara
authors.initials: T
authors.lastname: Nowling
authors.affiliation: Research Service, Ralph H. Johnson VA Medical Center, Charleston, South Carolina, United States Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, United States.
authors.forename: Bärbel
authors.initials: B
authors.lastname: Rohrer
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002829:Choroid / Q000473:pathology*; D020256:Choroidal Neovascularization / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D011415:Complement Factor B / Q000096:biosynthesis / Q000235:genetics*; D003170:Complement Pathway, Alternative / Q000235:genetics*; D004195:Disease Models, Animal; D004596:Electroretinography; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation; D007834:Lasers / Q000009:adverse effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000473:pathology / Q000503:physiopathology; D041623:Tomography, Optical Coherence
chemical_list: D012333:RNA, Messenger; D011415:Complement Factor B
keywords: RPE-specific transgenic mouse; age-related macular degeneration; alternative complement pathway; choroidal neovascularization; complement factor B