A cell's role in ageing

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A cell's role in ageing

Eliminating worn-out cells extends the healthy lives of lab mice — an indication that treatments aimed at killing off these cells, or blocking their effects, might also help to combat age-related diseases in humans. As animals age, cells that are no longer able to divide — called senescent cells — accrue all over their bodies, releasing molecules that can harm nearby tissues. Senescent cells are linked to diseases of old age, such as kidney failure and type 2 diabetes.

To test the cells’ role in ageing, Darren Baker and Jan van Deursen, molecular biologists at the Mayo Clinic in Rochester, Minnesota, and their colleagues engineered mice so that their senescent cells would die off when the rodents were injected with a drug. The work involved sophisticated genetic tinkering and extensive physiological testing, but the concept has an elegant simplicity to it. “We think these cells are bad when they accumulate. We remove them and see the consequences,” says Darren.

Mice whose senescent cells were killed off over six months were healthier, in several ways, than a control group of transgenic mice in which these cells were allowed to build up. Their kidneys worked better and their hearts were more resilient to stress. They tended to explore their cages more and they developed cancers at a later age. Eliminating senescent cells also extended the life spans of the mice by 20 to 30 per cent, Darren and Jan report.

The research is a follow-up to a 2011 study, in which their team also found that eliminating senescent cells delayed the onset of diseases of old age in mice, although that work had been done in mice which had a mutation that causes premature ageing. In the hope of discovering therapies for diseases of old age, researchers are already looking for drugs that can directly eliminate senescent cells or stop them from churning out factors that damage neighbouring tissue. They include Darren and Jan, who have licensed patents to develop such drugs to a company Jan has co-founded.

The team’s experiment “gives you confidence that senescent cells are an important target,” says Dominic Withers, a clinician-scientist who studies ageing at Imperial College London and who co-wrote an article for Nature that accompanies the Mayo Clinic report. “I think that there is every chance this will be a viable therapeutic option.”

Ewen Callaway Sleep and cold

There is plenty of evidence linking poor sleep to chronic diseases like diabetes and heart disease, but remarkably few good clinical trials have looked at whether sleep is a bulwark against respiratory infections. One such study, published in the journal Sleep, reported that adults who slept less than five or six hours a night were four times more likely to catch a cold than those who slept at least seven hours.

The trial was one of the first to objectively measure the amount of sleep volunteers got before they were deliberately exposed to the common cold through nasal drops containing the cold virus. A clinical trial in 2009 that relied on participants’ own accounts of their sleep habits also found sleep protective against common cold. In that trial, volunteers who reported sleeping fewer than seven hours a night were nearly three times more likely to catch a cold after exposure than those who slept eight hours or more.

An observational study from 2012 of nearly 60,000 women in the Nurses Health Study II also suggested sleep patterns may affect pneumonia risk. It found that women who slept five hours or less were more likely to develop pneumonia. Oddly enough, those who slept nine hours or more were also at higher risk. Dr Sanjay Patel, the study’s author, suggested that the women who slept excessively may have suffered from poor quality sleep. It is also possible that being in the sleep position for an extended time increases susceptibility to pneumonia, since bacteria that colonise the nose and throat may drip into the lungs, he said.

Scientists were not aware of any studies examining the role of sleep in bronchitis. Scientists are uncertain how sleep might help fight infections, but sleep is known to play a role in the regulation of the immune system. Studies suggest that sleep deprivation, for example, may lead to a weaker antibody response to vaccination, Sanjay said. Insufficient sleep “seems to reduce the functioning of cells like natural killer cells and lymphocytes that are important in giving you an immune response.”

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