title: The angio-fibrotic switch of VEGF and CTGF in proliferative diabetic retinopathy.
abstract: BACKGROUND
  In proliferative diabetic retinopathy (PDR), vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) cause blindness by neovascularization and subsequent fibrosis, but their relative contribution to both processes is unknown. We hypothesize that the balance between levels of pro-angiogenic VEGF and pro-fibrotic CTGF regulates angiogenesis, the angio-fibrotic switch, and the resulting fibrosis and scarring.
  
  
  RESULTS
  VEGF and CTGF were measured by ELISA in 68 vitreous samples of patients with proliferative DR (PDR, N = 32), macular hole (N = 13) or macular pucker (N = 23) and were related to clinical data, including degree of intra-ocular neovascularization and fibrosis. In addition, clinical cases of PDR (n = 4) were studied before and after pan-retinal photocoagulation and intra-vitreal injections with bevacizumab, an antibody against VEGF. Neovascularization and fibrosis in various degrees occurred almost exclusively in PDR patients. In PDR patients, vitreous CTGF levels were significantly associated with degree of fibrosis and with VEGF levels, but not with neovascularization, whereas VEGF levels were associated only with neovascularization. The ratio of CTGF and VEGF was the strongest predictor of degree of fibrosis. As predicted by these findings, patients with PDR demonstrated a temporary increase in intra-ocular fibrosis after anti-VEGF treatment or laser treatment.
  
  
  CONCLUSIONS
  CTGF is primarily a pro-fibrotic factor in the eye, and a shift in the balance between CTGF and VEGF is associated with the switch from angiogenesis to fibrosis in proliferative retinopathy.
authors.affiliation: Ocular Angiogenesis Group, Department of Ophthalmology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Esther J
authors.initials: EJ
authors.lastname: Kuiper
authors.forename: Frans A
authors.initials: FA
authors.lastname: Van Nieuwenhoven
authors.forename: Marc D
authors.initials: MD
authors.lastname: de Smet
authors.forename: Jan C
authors.initials: JC
authors.lastname: van Meurs
authors.forename: Michael W
authors.initials: MW
authors.lastname: Tanck
authors.forename: Noelynn
authors.initials: N
authors.lastname: Oliver
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Klaassen
authors.forename: Cornelis J F
authors.initials: CJ
authors.lastname: Van Noorden
authors.forename: Roel
authors.initials: R
authors.lastname: Goldschmeding
authors.forename: Reinier O
authors.initials: RO
authors.lastname: Schlingemann
mesh_terms: D000328:Adult; D000368:Aged; D049109:Cell Proliferation; D055513:Connective Tissue Growth Factor; D003930:Diabetic Retinopathy / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005123:Eye / Q000378:metabolism; D005260:Female; D005355:Fibrosis; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009389:Neovascularization, Pathologic; D016896:Treatment Outcome; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: C526317:CCN2 protein, human; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D042461:Vascular Endothelial Growth Factor A; D055513:Connective Tissue Growth Factor