Genetical modification to reduce bipolar cells in hESC derived retinas aiming for enhanced host-graft contact after transplantation

Abstract

Purpose : In a previous reports, we have shown that mouse and human ES/iPSC derived retinal tissue could develop to form ONL structure consisting of mature photoreceptors and that some graft photoreceptors form synapses with the host bipolar cells after transplantation in severely degenerated host retina of rd1 mice. However, the presence of graft inner cells or bipolar cells often seemed to interfere with the host bipolar – graft photoreceptor contact. The aim of this study was to establish the genetically modified hESC cell lines to produce retinas with a reduced number of graft bipolar cells.

Methods : In the CRX-GFP hESC line, using CRISPR/Cas9 system we knocked out the gene (ISLET1) that is considered to contribute to survival and maturation of ON bipolar cells. We then differentiated the KO cell line into retinal tissue (hESC-retina) by serum-free floating culture of embryoid body-like aggregates with quick reaggregation (SFEBq) method and were characterized by immunohistochemistry. Then these hESC-retinas were transplanted into the sub-retinal space of immunodeficient end-stage retinal degeneration rats [SD-Foxn1 Tg(S334ter)3LavRrrc]. Graft maturation and host–graft contact was studied in the control and in the KO hESC-retina by immunohistochemistry.

Results : The KO line differentiated similarly with the wild type as characterized by immunohistochemistry. By in-vivo fundus examination we confirmed the survival of CRX-GFP positive cells after transplantation. 180 days after transplantation, grafted cells show maturation of rod and cone photoreceptors in structured outer nuclear layers. Immunohistochemical analyses showed decrease number of bipolar cells in the KO line compared with the control line.

Conclusions : We could obtain the genetically modified hESC line that could subsequently produce retinal transplant with mature photoreceptors with decreased number of graft bipolar cells.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.