Covid-19 is notorious for attacking the lungs of patients, leaving them fighting for their lives. Yet already, a <a href="http://www.mofaic.gov.ae/en/mediahub/news/2020/5/2/02-05-2020-uae-medicine">team of doctors and researchers</a> in the UAE are working on new stem cell therapy to tackle the issue. The idea is that those suffering from damaged lung tissue will be able to breathe in cells to help kick start the regeneration process. And while it may sound implausible, results so far are promising and could play a key role in helping even the most seriously ill patients recover from the deadly virus. The body is made up of hundreds of different types of cell, each with its own specific role. But so-called stem cells are generalists, capable of becoming other types of cell and helping to regenerate damaged tissue. Researchers are finding ways of persuading stem cells to take on new roles and using them to create fresh tissue, or to help existing tissue repair itself. The lives of thousands of leukaemia patients have been saved by extracting stem cells from their blood and reprogramming them to become healthy bone marrow cells. Damaged bone, skin and eyes have also been repaired using fresh tissue created by stem cells. As early as January, researchers in China began investigating the potential for stem cell therapy in combating the deadly effects of Covid-19. A small group of seriously ill patients injected with stem cells showed signs of improvement in a few days with no adverse effects. Remarkably, all of them - including a critically ill elderly patient - recovered completely. Exactly why remains unclear: the leading theory is that the stem cells did not create fresh tissue, but secreted biochemicals over the damaged lung cells, encouraging them to repair themselves. The stem cells also seem to help patients by calming the body’s own immune system in fighting the virus. This can over-react, <a href="https://www.thenational.ae/uae/health/coronavirus-what-scientists-know-after-100-days-of-covid-19-1.1002913" target="_blank">triggering a "cytokine storm" that leads to organ failure and death even in young and healthy patients</a>. Instead of injecting patients with stem cells, the team at the Abu Dhabi Stem Cell Centre have developed a means of delivering the cells in a vapour that patients inhale directly into the lungs. In tests on 73 patients - a quarter of whom were in intensive care - stem cells derived from their blood were delivered using a jet nebulization process. Despite aiming to assess just the safety of the new approach rather than its effectiveness, the team found that all of the patients recovered with no signs of adverse effects. The UAE team has already begun trials that will compare the effectiveness of adding the stem cell therapy to the standard level of care given to Covid-19 patients. These are expected to be completed by the middle of this month. Other research teams are setting up clinical trials of stem cell therapy, focusing on its ability to protect patients against the over-reaction of their own immune systems. <a href="http://investorsmedia.mesoblast.com/static-files/337e723a-340d-493e-a4a1-0971d2c71460" target="_blank">A small study of seriously ill patients in a New York hospital</a> reportedly found more than 80 per cent of those treated with stem cell therapy survived, compared to just 12 per cent of patients receiving the standard level of care. <em>Robert Matthews is visiting professor of science at Aston University, Birmingham, UK</em>