Human Retinal Engineering using 3D PCL Scaffolds

Abstract

Patient specific induced pluripotent stem cell (iPSC) derived photoreceptor precursors are the ideal cell type for photoreceptor cell replacement and treatment of retinal degenerative blindness. However, bolus injection of donor cells as an unsupported cell suspension typically results in poor donor cell survival and lack of functional integration. Although polymer support scaffolds can be used to promote post‐transplant cellular survival and integration, in developing the ideal cell delivery scaffold two important considerations must be made: 1) mechanical matching between the cell delivery material and the host tissue and 2) proper cell packing/alignment. We hypothesize that by combining custom designed photomasks and photopolymerizable poly(caprolactone) (PCL) that we will be able to develop biocompatible cell delivery scaffolds that are ideally suited for human iPSC‐derived photoreceptor cell transplantation. Acrylate‐functionalized PCL was polymerized using custom photomasks. 9 independent photomasks were designed to create scaffolds with increasing pore diameter and decreasing pore spacing (i.e. opaque spots with increasing diameter that were spaced closer and closer together). In vitro cell compatibility studies, focused on determining if resultant PCL scaffolds promoted iPSC‐photoreceptor precursor cell survival and alignment, were performed. Cellular survival, identity, morphology and directionality were characterized via immunocytochemistry. In vivo biocompatibility studies, designed to evaluate local and systemic toxicity and/or tumorigenicity following subretinal transplantation of 3D PCL scaffolds, were performed in Pro23His Rhodopsin mutant pigs (N=12, 6 animals were sacrificed at 1‐month post‐transplant and 6 animals were sacrificed at 3‐months post‐transplant). At the time of sacrifice complete necropsy and tissue collection was performed. Photomasks with 75 um opaque spots that were spaced 25 um apart were determined to be ideal for creation of 3D retinal cell delivery scaffolds. 3D scaffolds were found to support the attachment and development of patient derived photoreceptor precursor cells in vitro. Specifically, following seeding photoreceptor precursor cells nested within the scaffold vertical pores and aligned in a manner similar to naturally occurring photoreceptor cells in vivo. No evidence of scaffold induced retinal damage or inflammation were detected via indirect ophthalmoscopy, fundus photography, or optical coherence tomography at either 1‐ or 3‐months post‐subretinal transplantation. Likewise, no evidence of systemic toxicity or tumorigenicity was detected following gross necropsy. The developed 3D PCL cell delivery scaffolds are compatible with iPSC derived photoreceptor cells in vitro and host retinal tissue in vivo. These findings lay the ground work for development of effective autologous photoreceptor cell replacement strategy.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.