Sustained growth factor cotreatment enhances survival of miPSC-derived RGCs following intravitreal transplantation

Abstract

Purpose : We and others have explored the transplantation of primary and pluripotent stem cell-derived retinal ganglion cells (RGCs) as a strategy to rescue vision in animal models of RGC loss. While donor cells integrate in more than 50% of the recipients, the number of surviving donor RGCs per host retina remains below 1%. To address this challenge we have tested if cotreatment with known neuroprotective factors BDNF, GDNF and CNTF can support survival of donor RGCs.

Methods : Three-dimensional retinal organoids derived from Thy1-GFP iPSC (C57Bl/6 background) were differentiated according to the Sasai protocol and cotreated with GDNF/BDNF/CNTF-loaded PODS^TM (POlyhedrin Delivery System). For transplantation Thy1⁺ cells were isolated by magnetic micro-beads at day 21. Healthy adult mice were injected with either RGCs alone or RGCs + PODS and donor cell survival was assessed at 2 weeks post-transplant. In a second study, adult mice were injected with NMDA one week prior to cell delivery to cause RGC death, and subsequently injected with either cells alone, cells + PODS, or PODS alone. ERG was performed at 6 weeks post-transplant. Prior to transplant, identity of donor RGCs was confirmed by RT-PCR, Flow Cytometry, Immunohistochemistry and Calcium Imaging.

Results : In-vitro pre-treatment of organoids with BDNF/GDNF-PODS resulted in a 46% increase of RBPMS⁺ RGCs. Co-delivery of Thy1⁺ RGCs with PODS enhanced transplantation success in healthy adults from 50% (4 mice out of 8) to 73% (8 out of 11). Donor cell survival was graded as: low (<0.5%), medium (0.5-1%) and high (1-1.5%). While in retinas without cotreatment 3 of 4 successful transplants showed high donor cell survival, rates were split for the cotreatment condition across medium (3/8) and high (2/8), indicating that PODS treatment can stabilize survival in low integration transplants. Axon outgrowth from donor RGCs was observed in all retinas with survival rates above 0.5% irrespective of cotreatment. In hosts with NMDA induced RGC loss, PODS treatment partially preserved RGC function as measured by pSTR response (32uV in PODS group vs 17uV in control).

Conclusions : Slow-release growth factor cotreatment is capable to stabilize donor RGC survival post-transplantation and enables enhanced donor RGC integration, thereby paving the way towards functional vision recovery.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.