Abstract
Purpose:
We have shown that a single intravitreal injection of anti-VEGF drugs has a strong influence on the choriocapillaris. It is known that endothelial cells in the kidney are also strongly VEGF dependent. Whether intravitreal drugs can be detected within the glomeruli or reduce VEGF in glomerular podocytes is not known. Therefore, we investigated the effects of a single intravitreal injection of aflibercept and ranibizumab on glomeruli of monkeys.
Methods:
The kidneys of eight cynomolgus monkeys which were intravitreally injected either with 2mg of aflibercept or with 0.5mg of ranibizumab were investigated one and seven days after injection. Two animals served as controls. The kidneys were investigated by electron microscopy and immunohistochemistry. The distribution of aflibercept, ranibizumab and VEGF was performed using anti-Fc or anti-F(ab)-fragment and anti-VEGF antibodies respectively. From each tissue-sample photos from 10 randomly chosen glomeruli-containing regions were taken at a magnification of x400. On these photos the glomeruli were defined as the regions of interest (roi). The ratio of stained area/nuclei was calculated using a semi-quantitative computer assisted method (image j software).
Results:
Compared to the controls, the anti-VEGF stained area in the roi of the ranibizumab-treated animals showed no significant changes at any of the analyzed time points whereas the stained areas of the aflibercept-treated monkeys showed a significant decrease one and seven days post treatment. The analysis of the immune reactivity (IR) against aflibercept or ranibizumab was only detected in aflibercept- or ranibizumab treated animals respectively and was unchanged between day one and seven. The fenestrae of the glomerular endothelial cells were not closed by diaphragms in contrast to those in the choriocapillaris.
Conclusions:
Surprisingly, both drugs could be detected within the capillaries of the glomeruli. Moreover, glomeruli’ and choriocapillaris’ fenestrae are morphologically different. After a single intravitreal injection of aflibercept, VEGF IR in the podocytes was significantly reduced compared to controls. Ranibizumab injection had no significant effect on glomeruli’s VEGF level. Whether this is caused by aflibercept’s higher affinity to VEGF or because it is used in higher stoichiometric concentration compared to ranibizumab remains to be investigated.
Keywords: 503 drug toxicity/drug effects •
554 immunohistochemistry •
597 microscopy: electron microscopy