Clinical and histological findings after intravitreal injection of bevacizumab (Avastin) in a porcine model of choroidal neovascularization.
OBJECTIVE
To examine the effect of intravitreally injected bevacizumab (Avastin) on the histological and angiographic morphology of choroidal neovascularization (CNV) in a masked and placebo-controlled animal study.


METHODS
Choroidal neovascularization was induced surgically in 11 porcine eyes by perforating Bruch's membrane with a retinal perforator. After closure of the ports used for the vitrectomy, which was performed to facilitate the Bruch's membrane rupture, 0.05 ml of either bevacizumab or Ringer-Lactat (placebo) was injected into the vitreous cavity. Eyes were enucleated after 14 days. Fundus photographs and fluorescein angiograms (FAs) were obtained immediately prior to enucleation. Sections of formalin- and paraffin-embedded eyes were examined by light microscopy and by immunohistochemical staining.


RESULTS
Placebo-injected eyes exhibited the highest propensity to leak, with five of six eyes leaking on FA, whereas only one of five bevacizumab-injected eyes exhibited leakage. On histological examination, all 11 eyes contained CNV membranes of similar size, regardless of treatment. The number of vascular endothelial cells was significantly reduced (p = 0.03) in CNV membranes from eyes that had been injected with bevacizumab when compared with CNV membranes from placebo-injected eyes. There was a trend towards more retinal pigment epithelium cells (p = 0.16) and fewer glial fibres (p = 0.08) in membranes from bevacizumab-treated eyes compared with placebo-treated eyes. Bevacizumab was identified immunohistochemically in the inner limiting membrane (ILM) and to a lesser degree in the remaining retina. Strong staining was also detected in both retinal blood vessels and entire CNV membranes with no cellular predisposition. Vascular endothelial growth factor expression was found in the CNV membranes, in the ILM, in the ganglion cell layer, in Müller cells throughout the neuroretina and in retinal blood vessels.


CONCLUSIONS
Bevacizumab significantly reduced the proliferation of vascular endothelial cells in CNV membranes and showed a strong trend towards a reduction of leakage from these membranes. After a single injection, bevacizumab did not exhibit a size reducing effect on CNV, but it was still present in the membranes 14 days after intravitreal injection.
Department of Neuroscience and Pharmacology, University of Copenhagen, Denmark. nl@eyepath.ku.dk <nl@eyepath.ku.dk>
Nathan
N
Lassota
Jan Ulrik
JU
Prause
Erik
E
Scherfig
Jens Folke
JF
Kiilgaard
Morten
M
la Cour
D020533:Angiogenesis Inhibitors / Q000008:administration & dosage*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage*; D061067:Antibodies, Monoclonal, Humanized; D000068258:Bevacizumab; D002199:Capillary Permeability / Q000187:drug effects; D020256:Choroidal Neovascularization / Q000188:drug therapy* / Q000473:pathology*; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005260:Female; D005451:Fluorescein Angiography; D007124:Immunoenzyme Techniques; D007267:Injections; D008856:Microscopy, Fluorescence; D013552:Swine; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000378:metabolism; D014821:Vitrectomy; D014822:Vitreous Body
D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D042461:Vascular Endothelial Growth Factor A; D000068258:Bevacizumab