Replacing damaged photoreceptor cells
Stargardt disease leads to photoreceptor cells’ deterioration in the macula, which makes cell therapy a current line of research.
The aim of cell therapy is to replace damaged cells with injected healthy cells, thus restoring altered cell functions. It consists of grafts or cell transplants. Two possibilities are being explored for Stargardt disease: RPE transplantation (retinal pigment epithelium transplantation) or photoreceptor cell transplantation.
In pigmentary retinopathies such as Stargardt disease, the following transplantation procedures are based on injection into the retina of:
- Either healthy retinal cells which will embed themselves in the retina
- Or stem cells which are able to differentiate and multiply to become normal, sufficient and functional retinal cells (photoreceptor cells, cells of the RPE) in order to replace the damaged cells.
Cell therapy is promising, but many obstacles have yet to be overcome: graft procedures, risks (rejection, the creation of a tumour…), the quantity and quality of cells produced…
As part of research, it is possible to transform adult skin cells into stem cells called IPS cells (Induced Pluripotent Stem cells) by genetically reprogramming these cells. These IPS cells have similar properties to an embryo’s stem cells. They can dedifferentiate themselves to become different cells and proliferate.
For the study of pigmentary retinopathies, IPS cells can be transformed into retinal cells (RPE, photoreceptor cells). The cells obtained are then produced in several identical copies in order to create cellular models.
Currently, researchers are studying the procedures of creation of cellular models for Stargardt disease from skin cells of adults affected by the disease. On the one hand, these models would enable a future better understanding of the disease’s mechanisms, and on the other hand, they would enable a sorting and study of future medical drugs for Stargardt disease.
However, these developments require a better understanding of stem cells’ self-renewal, differentiation and proliferation (in culture conditions or in the implanted tissue).