The principal cells involved in proliferative vitreo-retinopathy (PVR) are retinal pigment epithelial cells (RPE). Everolimus is a drug used in renal cell carcinoma which targets and inhibits a key regulatory protein in cancer (mTOR). In this study, the authors investigated the effect of everolimus on RPE cells and modification of the severity of experimental PVR induced by RPE cells. In the in vitro studies, everolimus significantly inhibited the proliferation and migration of RPE cells. In the in vivo studies (utilising rabbits with experimental PVR), 12 control eyes and 11 study eyes were included. Oral everolimus (0.5mg/day) suppressed the expression of mTOR in PVR, but there was no statistical difference in PVR grading between the study and control groups at all time points. This means that the drug did not show any effect in suppressing the experimental PVR. The authors conclude that this study does not exclude the role of everolimus or other mTOR inhibitors in clinical PVR. They highlight the difference between experimental and clinical PVR, and that PVR formation is multifactorial, in which the significance of mTOR is unknown. Further studies are needed to further investigate PVR therapies. 

Evaluation of the effect of everolimus on retinal pigment epithelial cells and experimental proliferative vitreoretinopathy.
Kuo HK, Chen YH, Kuo YH, et al.
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Kurt Spiteri Cornish

Sheffield Teaching Hospitals NHS Trust, London, UK.

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