A new study in rats shows that stem cell secretions, called exosomes, appear to protect cells in the retina, the
Exosomes are tiny
In his study, Ben Mead, Ph. D., a
Stem cells have been the focus of therapeutic attempts to replace or repair tissues because of their ability to morph into any type of cell in the body. However, from a practical standpoint, using exosomes isolated from stem cells presents some key advantages over transplanting whole stem cells.
«Exosomes can be purified, stored and precisely dosed in ways that stem cells cannot," Mead said.
Another important advantage of exosomes is they lack the risks associated with transplanting live stem cells into the eye, which can potentially lead to complications such as immune rejection and unwanted cell growth.
In a rat glaucoma model, Mead studied the effects of exosomes isolated from bone marrow stem cells on retinal ganglion cells. Exosomes were injected weekly into the rats’ vitreous, the fluid within the center of the eye. Prior to injection, the exosomes were fluorescently labelled allowing the researchers to track the delivery of the exosome cargo into the retinal ganglion cells.
The researchers determined that the protective effects of exosomes are mediated by microRNA, molecules that interfere with or silence gene expression. Further research is needed to understand more about the specific contents of the exosomes, said Stanislav Tomarev, Ph. D., a principal investigator at NEI and the study’s coauthor.
«We need to know which particular microRNA — there are more than 2000 different microRNA molecules — are delivered into the retinal ganglion cells and what proteins or signaling pathways are being targeted upon arrival," said Tomarev. «We also need to attempt to target exosomes to specific sets of neurons and other cell types or groups of cells.»
Finally, the most optimal exosome approach needs to be identified, Tomarev added. It may be that the best approach would be to combine exosomes with additional therapies. From a treatment feasibility standpoint, a lot will depend on how frequently exosomes need to be administered to achieve a therapeutic effect.
This work was supported by the Intramural Research Programs of the National Eye Institute.