title: Effects of intravitreal bevacizumab (Avastin) on the porcine retina.
abstract: BACKGROUND
  To evaluate the effects of intravitreal bevacizumab (Avastin) on the porcine retina, with respect to structural alterations, expression of proteins involved in apoptosis (bax, caspase-3, caspase-9) and gliosis (vimentin, GFAP), expression of factors which influence the development of vascular edema (VEGF, PEDF), and of membrane channels implicated in retinal osmohomeostasis (Kir4.1, aquaporin-1, aquaporin-4).
  
  
  METHODS
  One eye of seven adult pigs received a single intravitreal injection of bevacizumab (1.25 mg). Control eyes received buffered saline. For light and electron microscopy, the eyes were prepared 3 (one animal) and 7 days (two animals) after injection. Retinal slices were immunostained against gliosis- and apoptosis-related proteins. The gene expression was determined in the neuroretina and the retinal pigment epithelium of the remaining four animals with real-time RT-PCR 2 days after injection of bevacizumab.
  
  
  RESULTS
  Intravitreal bevacizumab did not induce alterations in the retinal structure, neither at light microscopic nor at electron microscopic level. The photoreceptors were well-preserved; no signs of photoreceptor damage or mitochondrial swelling were observed. Bevacizumab did also not induce reactive gliosis (as indicated by the unaltered immunolocalization of the glial proteins vimentin, GFAP, and glutamine synthetase) or apoptosis (as indicated by the unaltered immunolocalization of bax, caspase-3, and caspase-9). Intravitreal bevacizumab decreased the transcriptional expression of VEGF-A, and increased the expression of Kir4.1 in the neuroretina and pigment epithelium, and of PEDF in the pigment epithelium. Bevacizumab did not alter the transcriptional expression of GFAP, bax, caspase-3, VEGF receptor-1 and -2, and aquaporin-1 and -4.
  
  
  CONCLUSIONS
  A single intravitreal injection of bevacizumab does not result in structural changes of the porcine retina, nor in induction of gliosis or apoptosis. The bevacizumab-induced transcriptional downregulation of VEGF and upregulation of Kir4.1 might protect the retina from the development of vascular and cytotoxic edema.
authors.affiliation: Klinik und Poliklinik für Augenheilkunde, Universität Leipzig, Liebigstraße 10/14, 04103, Leipzig, Germany.
authors.forename: Ianors
authors.initials: I
authors.lastname: Iandiev
authors.forename: Mike
authors.initials: M
authors.lastname: Francke
authors.forename: Felix
authors.initials: F
authors.lastname: Makarov
authors.forename: Margrit
authors.initials: M
authors.lastname: Hollborn
authors.forename: Susann
authors.initials: S
authors.lastname: Uhlmann
authors.forename: Antje
authors.initials: A
authors.lastname: Wurm
authors.forename: Alexey
authors.initials: A
authors.lastname: Savvinov
authors.forename: Leon
authors.initials: L
authors.lastname: Kohen
authors.forename: Andreas
authors.initials: A
authors.lastname: Reichenbach
authors.forename: Peter
authors.initials: P
authors.lastname: Wiedemann
authors.forename: Thomas
authors.initials: T
authors.lastname: Pannicke
authors.forename: Andreas
authors.initials: A
authors.lastname: Bringmann
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000633:toxicity*; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D000068258:Bevacizumab; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005911:Gliosis / Q000139:chemically induced / Q000473:pathology; D058449:Intravitreal Injections; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012160:Retina / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D034421:Sus scrofa; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; D015415:Biomarkers; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D000068258:Bevacizumab