Stem cell represents the most promising strategy for RP and other retinal diseases in the near future, and therapeutics assisted by gene techniques, neuroprotective compounds and artificial devices can be applied to fulfil the clinical needs for different kinds of retinal diseases patients.
Till now, retinal progenitor cells (RPCs), induced pluripotent stem cells (iPS) and mesenchymal stem cells (MSCs) have finished early-stage clinical trials since they can all differentiate into RPE, photoreceptors or ganglion cells, and have demonstrated safety and efficacy. Following is the comparison of these three kinds of stem cells.
|Type of Stem Cells||Origin||Advantage||Disadvantage|
|Retinal Progenitor Cells|
|Derived from fetal retinas||Can migrate into retinal layers, develop into various retinal cell types.||Ethical and immune rejection issues|
|Induced pluripotent stem cells (iPS)||Derived from somatic cell, which is reprogrammed in vitro.||Can differentiate into functional RPE and photoreceptor precursor cells.||Risk of viral integrations and oncogene expression|
|Mesenchymal stem cells|
|From human umbilical cord, bone marrow, adipose tissue.||Can be induced into optic cells, the experiment demonstrated the cells slow down retinal cell degeneration.||Low rate of cell survival. Biosafety issues.|
However, there are challenges involved in such treatments when these techniques are applied in real clinical practice, such as the inhibition of proliferation or differentiation in vitro (with the exception of RPE), and the limited long-term survival and functioning of grafts in vivo. Some other issues remain to be solved concerning the clinical translation of stem cell therapy, including (1) the ability to enrich for specific retinal subtypes; (2) cell survival; (3) cell delivery, which may need to incorporate a scaffold to induce correct cell polarization, which increases the size of the retinotomy in surgery and, therefore, the chance of severe complications; (4) the need to induce a localized retinal detachment to perform the subretinal placement of the transplanted cell.