Stem cells are unripe cell that can divide but also specialise into specific cells for other tissues. Stem cells can develop into virtually every cell type in the body, which makes them versatile. Progenitor cells of the retina can differentiate into photoreceptors – rods and cones. They cannot develop into non-retinal cells, such as bone, fat or muscle cells.

When used for therapy, these retinal progenitor cells can fulfil two important functions. The first function is that they can produce grow factors with the possible result that the damaged retinal cells can be saved and the disease is slowed down. Another intended application of progenitor cells is inserting differentiated forms of the cells into the retina, replacing the dying retina cells by healthy cells.


The lab of Anai Gonzalez Cordero of University College in London cultivates retinal organoids using cells coming from a USH 2A patient. Retinal organoids, also called ‘eyes in a culture dish’, are made from stem cells and they are used to get more insight into Usher Syndrome and to test the effects of various medicines. In connection with this, skin cells of a patient are re-programmed into stem cells and then developed further into specific body tissues, in this case a retina.

Do you want to know more about cultivating a retina from skin cells? 


As the eye has few immune diseases, the body does not often regard transplanted progenitor cells as foreign intruders and rejection responses are considered to be unlikely. Because of this, patients probably have to make no or little use of additional medication to prevent rejection responses. The first clinical studies, testing applications of progenitor cells in patients with various eye disorders, were focused on studying the safety of this type of treatment. Most of these studies come to the conclusion that this type of treatment is generally tolerated well and safe. As studies into the safety only involve small numbers of patients, no scientifically well-based statement can be made about the effectiveness.

Cell therapy company jCyte has published preliminary results of a phase 1/2a clinical study for its study product, jCell, in retinitis pigmentosa (RP).

According to the company, the study, which covered 12 months, demonstrated that the application of jCell was safe and that a positive effect was seen. jCell has been recognised by the FDA for both orphan drugs and for regenerative medicine advanced therapy (RMAT).
In this treatment retinal progenitor cells are injected into the vitreous humour of the eye under local anaesthesia. It is hoped that diseased photoreceptors can be saved and be reactivated before they die.

The clinical trial phase 1/2 demonstrated that not only the development of retinitis pigmentosa was slowed down, but that some improvement was achieved as well.
The phase 1/2a study included 28 test persons. Observed side-effects are generally minor and only temporary. However, results from this study have not been published in scientific journals yet.
The company launched a larger phase 2b controlled study in order to judge the effectiveness of jCell. With support from the California Institute for Regenerative Medicine (CIRM), 85 patients have been included in the study phase 2b. Participants receive one jCell injection or a placebo. The effectiveness will be judged by testing the visual fields of vision, contrast sensitiveness, quality of life and the ability of participants to navigate through a labyrinth.

Update 7 September 2020:
Study phase 1 / 2a and 2b have shown that the therapy is effective, safe and even improves vision. The team now plan on carrying out a Phase 3 clinical trial starting next year.


Biotechnology company jCyte is gearing up to launch a phase 3 clinical trial in the United States for its jCell therapy, following a successful phase 2B trial and with approval from the U.S. Food & Drug Administration (FDA). The company plans to begin enrolling new participants for the next phase of the trial in the second half of 2024