Muscle fibers in the supporting substrate
Ji Hyun Kim et al. / Nature, 2020
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American doctors were able to accelerate the integration of printed muscles into a living body, supplying them with nerve cells during creation. Before that, researchers tried to use 3D printing to heal large muscle wounds, implanting artificial tissue into them, but it did not take root well. In the future, the new method will fully restore the performance of even those muscles that have lost more than a quarter of the volume as a result of injuries and diseases. The article is published in the journal. Nature communications.
3D printing of living tissue has been mastered for several years and has high expectations in medicine. The fact is that donor organs from another person require the use of immunosuppressants, may not take root and, most importantly, remain extremely scarce material. In 3D printing, organs are created from artificially bred cell culture, from the very beginning they are biologically compatible with the patient and can be produced in any quantity.
A team of scientists at Wake Forest University, led by Dr. Ji Hyun Kim, has explored the possibilities of transplanting printed muscle tissue into a living organism. The fact is that if, as a result of mechanical injuries, burns or frostbite, a muscle has lost more than 20 percent of its volume, it practically cannot independently regenerate and restore full functionality. Previously, researchers managed to transplant artificially grown tissue into such a muscle, and it took root, but the problem was that the nervous system had been integrating new fibers for a very long time. As a result, they managed to atrophy and degrade faster than the body could begin to control them.
To accelerate this integration, doctors decided to try to introduce nerve cells immediately when printing. The task was complicated by the fact that the abundance of foreign cells prevents the muscle from forming fibers, without which the muscles could not contract. Through experiments, it was found that the ideal balance between the embryos of muscle cells and nerve cells is approximately 300 to one. Both those and others landed a printhead on a polymer, which after transplantation into the body dissolves.
–Future muscles on a polymer substrate are visible in Figure B, implanted tissue is shown in Figure C, where the substrate has resorbed and the nerves from the neuron sprouted to the blocked nerve cells
Ji Hyun Kim et al. / Nature, 2020
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Then, 40 percent of the thigh muscle was surgically removed from several laboratory rats and four control groups were formed from the animals — intact (but immobilized for atrophy), without tissue transplantation, with transplantation of pure muscle fibers and a neuromuscular composite. As a result, it turned out that the inclusion of nerve cells in the tissue really significantly accelerates its acceptance by the body. But most importantly, only using this method it was possible to achieve a complete restoration of functionality – eight weeks after the operation, the contraction force was almost equal to that of muscles that simply did not work for this period.
–Strength of muscle contraction, from left to right – intact, without implantation, with the implantation of pure muscle fibers and with embedded nerve cells
Ji Hyun Kim et al. / Nature, 2020
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In recent years, with the help of three-dimensional printing, a miniature heart has been created, and arteries have been able to print using a conventional 3D printer.
Vasily Zaitsev
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