Stem Cell Transplantation Can Restore Vision In Mice With Retinal Degeneration

An example of macular degeneration

Implantation of retinal tissue derived from mouse induced pluripotent stem cells (iPSCs) can restore vision in mice with end-stage retinal degeneration

Retinal degeneration is the primary cause of blindness in aged individuals, and commonly occurs as a result of macular degeneration or retinitis pigmentosa. Progressive damage to a layer of photosensitive cells results in ever worsening vision loss and eventual blindness. There is no curative therapy available today. 

Using induced pluripotent stem cells (iPSCs)

In many conditions in which cell death or loss is a cause, cell therapies and stem cell technology are becoming a promising route of research. A team from the RIKEN Center for Developmental Biology therefore set out to test whether iPSCs could provide treatment for this age-related vision loss. They began by reprogramming cells taken from the skin of adult mice with specific factors that instruct the cells to revert back to an embryonic-like state. They then carefully coaxed these cells into forming retinal tissue, and implanted this tissue into mice with end-stage retinal degeneration. 

What happened? 

Synaptic integration of graft retina into host mice. Host bipolar cells shown in green and graft retina shown in red. Credit: Mandai et al./Stem Cell Reports 2017

The new tissue integrated and formed new photoreceptor cells able to link up to their neighbouring cells. Transplantation led to structured outer nuclear layers consisting of mature photoreceptors. All of the transplanted retinal tissue showed some response to light input, and the strategy was able to restore vision to varying degrees in almost half of the mice treated. The researchers note that differentiating iPSCs into retinal tissue instead of individual retinal cells appeared to have a stronger regenerative impact; providing a 3D structure encouraging better maturation and integration. 

"We showed the establishment of host-graft synapses in a direct and confirmative way. No one has really shown transplanted stem cell-derived retinal cells responding to light in a straightforward approach as presented in this study, and we collected data to support that the signal is transmitted to host cells that send signals to the brain. The photoreceptors in the 3D structure can develop to form more mature, organized morphology, and therefore may respond better to light. From our data, the post-transplantation retina can respond to light already at one month in mice, but since the human retina takes a longer time to mature, it may take five to six months for the transplanted retina to start responding to light"

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