Nerves from viruses
Geneticists have taught viruses to repair nerve tissueViruses can restore the functioning of nervous tissue and sooner or later will be used to treat patients with spinal cord injuries, Professor Seung-Wuk Lee from the University of California at Berkeley is confident in the scientific group.
The so–called bacteriophages are viruses that infect bacterial cells, but cannot penetrate into animal cells. Viruses are good because they are able to copy themselves and create structures similar to tissues in the body of animals, while all artificial tissue substitutes must be synthesized in the laboratory and shaped there. If you change the genetic code of a bacteriophage, it will produce the proteins necessary for the cell, supporting the growth and organization of neurons, for example.
While some scientists are trying to grow and transplant native cells of a diseased human organ, others are coming up with matrices that allow creating the skeleton of the desired organ (most often it is made from fibrillar protein and polymers, sometimes from old or donor organs).
Lee's team went the other way. "Viruses are smart materials," says the professor. "By collecting the genome of only one of them, you get a colony of billions of the same phages ready for subsequent replication" (an article by the authors of Genetically Engineered Nanofiber–Like Viruses For Tissue Regenerating Materials published in the journal Nanoletters).
A little background: the head of the laboratory has been working with the bacteriophage M13, a long and protein-fiber-like virus capable of creating complex cell matrices, for almost his entire scientific career. Lee participated in the work on the creation of an electric battery based on this bacteriophage. Other phages are also used, for example, as antibacterial components for preserving food (their safety for the human body has been proven) and are being investigated as a medicine for the treatment of chronic bacterial infections.
First, Lee and his colleague Anna Merzlyak changed the genetic code of M13 so that proteins appeared on its surface that help neurons grow, connect into a single whole and stretch in length. Then the viruses were placed in a nutrient medium and given the opportunity to multiply, after which they were transplanted into a solution containing the precursor cells of neurons.
These cells differ from stem cells by a greater degree of development, but they also need some message so that they form new tissues. In the solution, the viruses align, forming a semblance of liquid crystals.
A scheme for creating fibers using bacteriophages.
NPC–precursor cells of neurons (illustration Nano Letters).
Biologists place this solution in agar (a jelly-like medium), in which long fibers of nervous tissue grow, neurons mixed with viruses. The resulting structure (the position of the fibers and their branching) can be influenced by changing the concentration and magnetic fields around the vessels with the tissue being grown.
The photo shows a section of the resulting fiber. Its creation would not be possible if it were not for the work of billions of viruses in its structure (photo Nano Letters).
We have to talk about development in the future for the reason that scientists have not yet been able to grow neurons inside a living organism. However, preparations for tests on mice are already underway. It is necessary to check how the immune system of animals will react to the presence of bacteriophages in the body.
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