Researchers at the Wellcome Sanger Institute and University College London Institute have identified a type of lung cell that can almost “magically” replenish the lining of airways in people who have given up smoking.
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A study of lung biopsies taken from 16 individuals found that among former smokers, many of the cells that had been damaged by smoking had been replaced with healthy ones that closely resembled those seen in people who had never smoked.
For some former smokers, there was no longer any evidence of lung damage smoking within a few years of quitting the habit.
Scientists had previously thought that the smoking-induced mutations that lead to lung cancer are permanent and persist even when a person has stopped smoking.
However, according to findings recently reported in the journal Nature, certain cells that go unscathed by tobacco damage later repair the lining of the lungs.
“It’s never too late to quit”
People who have smoked heavily for 30, 40 or more years often say to me that it’s too late to stop smoking – the damage is already done. What is so exciting about our study is that it shows that it’s never too late to quit.”
Campbell added that some people included in the study had smoked over 15,000 packets of cigarettes, yet, within just a few years, many of the cells lining their airways showed no evidence of damage.
What did the study involve?
The chemicals found in tobacco drive DNA mutations in lung cells, eventually making them cancerous, even before a smoker has developed cancer.
For the study, Campbell and the team looked for these mutations in the lungs of 16 individuals, including current smokers, former smokers, never smokers and children.
Some mutations are harmless and occur as a natural part of aging. These are referred to as “passenger mutations.” However, some mutations “dramatically change the behavior of the cells and instruct them to behave more like cancer,” Campbell told the news agency AFP. “If enough of these ‘driver mutations’ accumulate, then the cell will become full-blown cancer.”
Campbell and the team found that, among the lung biopsies taken from people who smoked, 90% of the cells had cancer-driving mutations.
These can be thought of as mini time bombs, waiting for the next hit that causes them to progress to cancer,"
However, a small proportion of the cells had escaped the tobacco damage and were still healthy.
Among former smokers who had given up, these healthy cells had proliferated and replaced the mutated cells.
Furthermore, as much as 40% of cells in the lungs of people who had stopped smoking were healthy, compared with one-quarter of that amount among individuals who had not yet stopped smoking.
"We were unprepared for the finding”
"We were unprepared for the finding. There is a population of cells that, kind of, magically replenish the lining of the airways,” Campbell told the BBC News: “One of the remarkable things was patients who had quit, even after 40 years of smoking, had regeneration of cells that were unscathed by the exposure to tobacco."
Campbell says what researchers need to do now is locate the pool of healthy lung cells and find out exactly how they replace the damaged cells.
“If we can work out where they normally live and what makes them expand when someone stops smoking, perhaps we have opportunities to make them even more effective at repair,” he concludes.
BBC News. (2020). Lungs 'magically' heal damage from smoking. [online] Available at: https://www.bbc.co.uk/news/health-51279355 [Accessed 30 Jan. 2020].
the Guardian. (2020). Lungs damaged by smoking can heal – study. [online] Available at: https://www.theguardian.com/society/2020/jan/30/lungs-damaged-by-smoking-can-magically-heal-study [Accessed 30 Jan. 2020].
Pfeifer, G. (2020). Smoke signals in the DNA of normal lung cells. Nature.