Combined Cell and Gene Therapy towards the Treatment of Age-Related Macular Degeneration and Diabetic Retinopathy

Abstract

Purpose : Anti-angiogenic drugs (i.e. Avastin) only temporarily repair leaky blood vessels, thus AMD and DR-patients require monthly injections. These treatments may cause side effects such as stroke, gastrointestinal perforations and hemorrhage. We hypothesized that cells transplanted into a diseased eye expressing novel, local acting anti-vascular biologics, or “VEGF Sticky-Trap”, can inhibit VEGF-dependent neovascularization (NV) in AMD and DR in a controlled and long-term manner, replacing damaged cells and avoiding any potential systemic side effects.

Methods : Cells expressing VEGF Stick-trap in an inducible manner (human RPE and mouse MSC) were generated in vitro and 4x10^4 cells (2x10^4 cells/ul) in 0.5%/0.5% hydrogel solution were injected subretinally (RPE; n=10) or intravitreally (MSC; n=10) of CD-1 mice. The contralateral eyes served as vehicle (hydrogel) controls (n=20). Subsequently to cell injections, half of the experimental groups were fed a doxycycline (DOX) diet to induce transgene expression from transplanted cells. 3 weeks post cell transplantation surgery, mice were perfused with 4% PFA solution and enucleated. Eyes were either subjected for cross-sectioning or retina’s were isolated and flat mounted.

Results : In previous studies we have shown, that upon intravitreal and subretinal injection with traps (10ug/eye), VEGF Sticky-Trap binds to the eye ECM. In contrast to the original VEGF- trap, developed by Regeneron, VEGF Sticky-trap was local acting and undetectable in circulation 6 hrs post eye injection. Furthermore, we have shown that VEGF Sticky-trap is able to inhibit NV in an oxygen-induced retinopathy mouse up to 74% compared to 39 and 26% in the case of VEGF-trap and vehicle (n=23, p<0.05)). VEGF Sticky-trap, expressed by generated RPE cells and MSC in vitro, is able to bind to ECM and trap soluble VEGF only upon DOX induction (VEGF-ELISA assay). 5% of injected cells incorporates into the eye, and expresses VEGF Sticky-trap in vivo only upon induction with DOX diet. In addition, VEGF Sticky-trap expressed by transplanted cells, is able to bind to eye ECM.

Conclusions : The injection of transgenic cells into the eye of CD-1 mice showed a low integration potential, but all incorporated cells were able to express VEGF Sticky-trap upon DOX induction. Next, we will determine, if incorporated cells are able to inhibit NV in mouse models of AMD and DR.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.