Evaluation of the Effect of Everolimus on Retinal Pigment Epithelial Cells and Experimental Proliferative Vitreoretinopathy

ABSTRACT

Purpose: Failure of retinal detachment surgery is most commonly due to the development of proliferative vitreoretinopathy (PVR). Everolimus is an inhibitor of mammalian target of rapamycin (mTOR), and is available as oral tablets. In this study, we investigated the effect of everolimus on retinal pigment epithelial cells and modification of the severity of experimental PVR.

Methods: In our in vitro studies, primary culture of retinal pigment epithelium (RPE) cells was obtained from pigmented Rex rabbits. Cell proliferation was assayed with the tetrazolium dye cytotoxicity test, and cell migration assay was performed in 24-well transwell units with 8-μm filters. In the in vivo study, pigmented Rex rabbits weighing between 2 and 2.5 kg were used. Each rabbit eye underwent gas compression; one week later, 5 × 10⁴ RPE cells were injected into the vitreous cavity to induce PVR, and each eye was graded with indirect ophthalmoscopy on days 1, 3, 7, 14, 21, and 28. The rabbits were administered everolimus (0.5 mg/day orally) from the day of PVR induction. Total proteins extracted from RPE cells and dissected retinal samples were processed for Western blotting analysis of mTOR and ribosomal protein S6 (RPS6).

Results: The in vitro studies showed that everolimus significantly inhibited the proliferation of RPE cells at 0.1 μg/ml; additionally, at 10 μg/ml, it suppressed the migration of RPE cells and significantly suppressed the expression of mTOR and RPS6 in RPE cells. The in vivo study did not show any benefit of oral everolimus (0.5 mg/day) in suppressing experimental PVR. Thus, everolimus significantly suppressed the expression of mTOR and RPS6 in PVR.

Conclusions: Everolimus suppressed the proliferation and migration of RPE cells in vitro. Oral everolimus (0.5 mg/day) suppressed the expression of mTOR and RPS6 in the retina, but showed no effect in suppressing experimental PVR.

KEYWORDS:

• Everolimus
• mammalian target of rapamycin (mTOR)
• proliferative vitreoretinopathy
• retinal detachment
• ribosomal protein S6 (RPS6)

Acknowledgments

This work was supported by grant CMRPG8C0321 from the Chang-Gung Memorial Hospital, Taiwan. Mr. Hung Su and Jentaie Shiea, PhD (Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan) assisted in detection of intraocular everolimus with liquid chromatography coupled with tandem mass spectrometry (LC-MS).

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.