Healthy cells ‘magically’ regrow in ex-smokers: study

Quitting smoking can do more than just halt damage to the lungs. A study shows regrowth of cells unscathed by exposure to tobacco.

Scientists were “totally unprepared” for the finding there is a population of cells that magically replenish the lining of the airways. Picture: istock

Quitting cigarettes triggers the regrowth of healthy cells, undoing some of the damage done by decades of heavy smoking, according to a study.

Even the cells in the airways of a 70-year-old who has smoked 10,000 packets of cigarettes over their lifetime can start to replenish, researchers said.

The study found that dormant cells within the airway lining which have avoided damage from tobacco smoke can spring into life and multiply to replace damaged ones.

Previous work showed that former smokers who quit seven years earlier had a 43 per cent lower risk of lung cancer compared with those who still smoked. Former smokers who quit 12 years earlier had a 72 per cent lower risk.

The study in Nature suggests that people who have given up smoking have more “genetically healthy” lung cells than people who still smoke.

Cancer Research UK said: “The study shows that quitting smoking could do much more than just stopping further damage to the lungs.

“Researchers believe it could also allow new, healthy cells to actively replenish the lining of our airways. This shift could help protect against cancer.”

The cells of the lungs of someone who has never smoked are at normal or near-normal levels of health. For smokers this falls to between 4 and 10 per cent but for someone who has quit, the proportion of healthy cells can return to between 20 and 40 per cent.

The researchers, from the Welcome Trust Sanger Institute in Essex and University College London Hospital, found that the benefits of stopping smoking “begin immediately, accrue with time and are evident even after quitting late in life”.

They said, however, that the damage caused by smoking to deeper layers of lung tissue “is not reversible”. Smoking can damage the DNA in lung cells and create genetic errors. If there are enough mutations, the cells can divide uncontrollably and become cancerous.

Researchers took lung biopsies from 16 people including smokers, ex-smokers and people who had never smoked and sequenced the DNA from 632 cells. They found that up to 96 per cent of cells in a smoker’s lungs had genetic mutations not present in non-smokers and 25 per cent of these cells had at least one mutation linked to cancer.

The researchers said they were surprised by their findings that the lungs of people who had given up smoking had four times more healthy cells in their airways than people who still smoked and that these cells were as healthy as those in people who had never started.

The study concludes: “Stopping smoking, at any age, does not just slow the accumulation of further damage, but can reawaken cells unscathed by past lifestyle choices.”

Peter Campbell, of the Sanger Institute, told the BBC: “We were totally unprepared for the finding. There is a population of cells that magically replenish the lining of the airways.

“One of the remarkable things was patients who had quit, even after 40 years of smoking, had regeneration of cells that were totally unscathed by the exposure to tobacco.”

The Times