Reduced occurrence of programmed cell death and gliosis in the retinas of juvenile rabbits after short-term treatment with intravitreous bevacizumab

Abstract

OBJECTIVE:Bevacizumab has been widely used as a vascular endothelial growth factor antagonist in the treatment of retinal vasoproliferative disorders in adults and, more recently, in infants with retinopathy of prematurity. Recently, it has been proposed that vascular endothelial growth factor acts as a protective factor for neurons and glial cells, particularly in developing nervous tissue. The purpose of this study was to investigate the effects of bevacizumab on the developing retinas of juvenile rabbits.METHODS:Juvenile rabbits received bevacizumab intravitreously in one eye; the other eye acted as an untreated control. Slit-lamp and fundoscopic examinations were performed both prior to and seven days after treatment. At the same time, retina samples were analyzed using immunohistochemistry to detect autophagy and apoptosis as well as proliferation and glial reactivity. Morphometric analyses were performed, and the data were analyzed using the Mann-Whitney U test.RESULTS:No clinical abnormalities were observed in either treated or untreated eyes. However, immunohistochemical analyses revealed a reduction in the occurrence of programmed cell death and increases in both proliferation and reactivity in the bevacizumab-treated group compared with the untreated group.CONCLUSIONS:Bevacizumab appears to alter programmed cell death patterns and promote gliosis in the developing retinas of rabbits; therefore, it should be used with caution in developing eyes.

In Vitro Effects of Bevacizumab Treatment on Newborn Rat Retinal Cell Proliferation, Death, and Differentiation

“…However, no quantitative analyses of cell death, proliferation, and gliosis were performed. 22 On the other hand, Fusco et al 23 evaluated juvenile rabbits treated with bevacizumab intravitreously in one eye while the contralateral eye was assigned as control. Immunohistochemistry revealed fewer cells undergoing programmed cell death, more proliferating cells, and increased reactivity of glial cells in bevacizumab-treated eyes compared with controls.…”

“…Nevertheless, a possible influence of the injection procedure could not be ruled out. 23 In the current study, we moved one step further in the analysis by investigating the effect of bevacizumab using an in vitro-organotypic culture of developing retina. To accomplish this, we used explants of developing rat retina, which provide an excellent model to study mechanisms of proliferation, cell death, and differentiation in a complex and highly structured tissue, provided the spatial distribution of the various cell types, the neurochemical circuitry, and the extracellular matrix microenvironment are preserved.…”

“…On the other hand, using quantitative immunohistochemistry, Fusco et al 23 observed more proliferating cells, greater glial cell reactivity, and fewer cells undergoing programmed cell death in the retinas of 28-day-old rabbits injected intravitreously with bevacizumab than in nontreated retinas. 23 However, while the effect was most likely the result of the pharmacological action of bevacizumab, since a sham injection in the fellow eye was not delivered, a contributory effect of the inflammation caused by the trauma of intraocular injection could not be ruled out, pointing out the need for further studies to clarify this issue.…”

“…20,21 Only two previous studies have evaluated the effect of anti-VEGF agents on the developing retina in vivo. 22,23 Zayit-Soudry et al 22 evaluated the effect of intravitreal administration of bevacizumab on the developing retina of 11-or 25-day-old rabbits, but found no electroretinographic or morphological abnormalities; nevertheless, no quantitative analysis of cell death, proliferation, or reactive gliosis were performed. On the other hand, using quantitative immunohistochemistry, Fusco et al 23 observed more proliferating cells, greater glial cell reactivity, and fewer cells undergoing programmed cell death in the retinas of 28-day-old rabbits injected intravitreously with bevacizumab than in nontreated retinas.…”

“…22,23 Zayit-Soudry et al 22 evaluated the effect of intravitreal administration of bevacizumab on the developing retina of 11-or 25-day-old rabbits, but found no electroretinographic or morphological abnormalities; nevertheless, no quantitative analysis of cell death, proliferation, or reactive gliosis were performed. On the other hand, using quantitative immunohistochemistry, Fusco et al 23 observed more proliferating cells, greater glial cell reactivity, and fewer cells undergoing programmed cell death in the retinas of 28-day-old rabbits injected intravitreously with bevacizumab than in nontreated retinas. 23 However, while the effect was most likely the result of the pharmacological action of bevacizumab, since a sham injection in the fellow eye was not delivered, a contributory effect of the inflammation caused by the trauma of intraocular injection could not be ruled out, pointing out the need for further studies to clarify this issue.…”