Transplantation of human embryonic stem cell-derived retinal tissue in two primate models of retinal degeneration

Abstract

Retinal transplantation therapy for retinitis pigmentosa is increasingly of interest due to accumulating evidence of transplantation efficacy from animal studies and development of techniques for the differentiation of human embryonic stem cells (hESCs) and induced pluripotent stem cells into retinal tissues or cells. In this study, we aimed to assess the potential clinical utility of hESC-derived retinal tissues (hESC-retina) using newly developed primate models of retinal degeneration to obtain preparatory information regarding the potential clinical utility of these hESC-retinas in transplantation therapy. hESC-retinas were first transplanted subretinally into nude rats with or without retinal degeneration to confirm their competency as a graft to mature to form highly specified outer segment structure and to integrate after transplantation. Two focal selective photoreceptor degeneration models were then developed in monkeys by subretinal injection of cobalt chloride or 577-nm optically pumped semiconductor laser photocoagulation. The utility of the developed models and a practicality of visual acuity test developed for monkeys were evaluated. Finally, feasibility of hESC-retina transplantation was assessed in the developed monkey models under practical surgical procedure and postoperational examinations. Grafted hESC-retina was observed differentiating into a range of retinal cell types, including rod and cone photoreceptors that developed structured outer nuclear layers after transplantation. Further, immunohistochemical analyses suggested the formation of host-graft synaptic connections. The findings of this study demonstrate the clinical feasibility of hESC-retina transplantation and provide the practical tools for the optimization of transplantation strategies for future clinical applications.

Developments in 3D neural cell culture models: the future of neurotherapeutics testing?

“…Self-assembled aggregate cultures, which encompass spheroids, embryoid bodies, neurospheres, and microtissues, can be formed through suspension culture, in concave microwells, on sponge-gel matrices, and by a variety of other methods [12][13][14][15][16][17][18]. Neural spheroids can be produced using primary neural cells or neural cell lines such as the SK-N-SH neuroblastoma cell line for brain tumor studies [12,13].…”

“…However, our understanding and capabilities to manipulate stem cell aggregate development and differentiation has seen rapid advancement. Complex, patterned, and potentially transplantable formations of cortical and retinal tissue can be formed using self-organized aggregates of stem cells [16][17][18]. An important consideration when choosing a 3D culture model is that spheroids can be produced at a faster rate and…”

Embryoids, organoids and gastruloids: new approaches to understanding embryogenesis

“…This approach was later adapted for making retinal tissue from human ESCs (hESCs) (Kuwahara et al, 2015). More recently, it was shown that human optic cup organoids engrafted onto injured eyes in primates continue to differentiate into a variety of retinal cell types, even creating synaptic contacts with the host (Shirai et al, 2016). Many other examples of organoids have also emerged (reviewed by McCauley and Wells, 2017), including gut (Sato et al, 2009;Spence et al, 2011), kidney (Takasato et al, 2015), pancreas (Greggio et al, 2013) and even brain (Eiraku et al, 2008;Lancaster et al, 2013) organoids.…”

hESC-derived photoreceptors survive and integrate better in immunodeficient retina

“…One word of caution: Zhu et al argued that immunosuppression may have enhanced transplant integration in the study of Shirai et al (5), but this study already used cyclosporine A as immunosuppressant. The study by Zhu et al confirms that immunodeficient animal models are better for transplant survival and integration than models that need immunosuppression by drugs because of the side effects of immunosuppressant drugs (24).…”

“…T h e r e a r e t w o d i f f e r e n t s t r a t e g i e s t o r e p l a c e photoreceptors: (I) transplantation of retinal progenitor sheets (fetal retina or stem-cell derived) (2)(3)(4)(5). Fetal retinal sheet transplants have resulted in long-term visual improvements in different animal models of retinal degeneration (4,(6)(7)(8) and in patients (9), and have shown to integrate and synaptically connect with a degenerated retina (6,8).…”