Stem cell exosomes protect the retina

Researchers at the US National Eye Institute led by Dr. Stanislav Tomarev have found that stem cell secretions, the so–called exosomes, have the ability to protect retinal cells - the light-sensitive tissue of the eye – from damage.

The image obtained with the help of a microscope shows exosomes (green),
surrounding ganglion cells (orange and yellow).

Exosomes are tiny membrane bubbles that form inside cells and subsequently extend beyond them. For a long time it has been assumed that exosomes are a component of the excretory system of the cell, but recently scientists have found that these bubbles are filled with proteins, fats and RNA that regulate the activity of genes. Experiments have shown that exosomes of one cell can be absorbed by another cell by merging with the membrane of the target cell, which triggers the synthesis of new proteins in it. Exosomes also facilitate intercellular interactions and play the role of signaling elements, which indicates their potential therapeutic potential.

As part of his research, Dr. Ben Mead studied the effect of exosomes released by stem cells on retinal ganglion cells that form the optic nerve, which provides the transmission of visual signals from the eye to the brain. The death of these cells in glaucoma and other optical neuropathies leads to loss of vision.

Stem cells attract the attention of scientists trying to replace or repair damaged tissues because of their ability to differentiate into any types of cells in the body. However, from a practical point of view, the use of exosomes isolated from stem cells has a number of advantages over the transplantation of stem cells themselves. According to the Ministry of Foreign Affairs, exosomes can be cleaned, stored and used in strictly dosed quantities, which is impossible when working with stem cells.

Another important advantage of exosomes is the absence of the risk associated with transplantation of living stem cells into the eye tissue, which can potentially cause the development of complications such as immune rejection and unwanted cell growth.

The authors studied the effect of exosomes isolated from bone marrow stem cells on retinal ganglion cells of a rat model of glaucoma.

At the beginning of the experiment, the animals were damaged by the optic nerve of one eye, after which exosomes were injected into the vitreous body of the damaged eye at a dose of 3X10 ⁹. Injections were repeated after 7 and 14 days. Prior to the introduction, exosomes were labeled with fluorescent labels, which made it possible to evaluate the delivery of their contents into retinal ganglion cells. On the 21st day of the experiment, the rats were killed, after which the condition of their retina was analyzed.

According to the data obtained, the introduction of exosomes ensured the preservation of about 70% of retinal ganglion cells, whereas in the control group that did not receive therapeutic injections, up to 90% of these cells died. In addition, according to electroretinography, which evaluates the electrical activity of retinal cells, the introduction of exosomes ensured the preservation of the functionality of ganglion cells.

The authors found that the protective effect of exosomes is mediated by microRNA molecules that alter or suppress gene expression. According to Dr. Tomarev, further research is needed to obtain more detailed information about the contents of exosomes. It is necessary to determine which microRNA from more than 2,000 known molecules is delivered to ganglion cells and which proteins or signaling pathways they affect inside cells. In addition, the researchers plan to create exosomes specific to certain types of neurons and other cells or groups of cells.

In addition, they note the need to identify the optimal approach to the use of exosomes, including the possibilities of combining them with other therapeutic approaches, as well as their frequency of administration.

The article by Mead B. and Tomarev S. Bone Marrow-Derived Mesenchymal Stem Cells-Derived Exosomes Promote Survival of Retinal Ganglion Cells Through miRNA-Dependent Mechanisms is published in the journal Stem Cells Translational Medicine.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the National Eye Institute: Stem cell secrets may protect against glaucoma.

01.02.2017