Vapor no bar to healing

Laboratory wound-healing assays have revealed that whereas cigarette smoke completely prevents wound healing at concentrations of more than 20 percent, electronic-cigarette vapor has no such effect, even at 100 percent concentration and double the amount of nicotine relative to that in smoke.

According to a British American Tobacco press note, the scratch tests involved growing in the laboratory a layer of endothelial cells (cells that line the inside of blood vessels), creating a wound/scratch in the layer of cells, and observing how long it took to heal.

It was found that the wound healed normally when exposed cells were untreated or when they were exposed to e-cigarette vapor, but not when exposed to cigarette smoke.

The results are published today in Toxicology Letters (DOI is 10.1016/j.toxlet.2017.06.001).

“Our results suggest that chemicals in cigarette smoke that inhibit wound healing are either absent from e-cigarette vapor or present in concentrations too low for us to detect an effect,” Dr. James Murphy, head of reduced risk substantiation at BAT was quoted as saying.

The press note went on to say that it was thought that the presence of damaged endothelial cells, which have an impaired ability to repair, might be a factor in the development of heart disease. Smoking was known to be a risk factor for the development of heart disease.

‘The basic steps of the test involve creating a wound in a single layer of cells grown in the lab, capturing images of the beginning and at regular intervals during the “healing” process, as the cells move together, and then comparing the images,’ the press note said.

‘In this way, it is possible to measure the ability of a tissue to repair an artificial injury in the presence of various substances. To repair the wound created by a scratch, cells must move into the wound and close the gap, and it’s the rate at which they do it that the test measures.

‘Scientists at British American Tobacco used the scratch test to compare the effects of smoke extract from a reference cigarette (3R4F) and vapor extract from two commercial e-cigarettes, Vype ePen (a closed modular device) and Vype eStick (a cig-a-like device), on the wound healing process.

‘When a person smokes or vapes, water-soluble chemicals pass into circulation and interact with endothelial cells lining blood vessels. So to mimic this exposure, the scientists tested aqueous extracts – the water-soluble fraction – of smoke or vapor. Aqueous extracts were obtained by bubbling puff-matched amounts of smoke or vapor through cell-growth medium to produce a stock that could be diluted into various concentrations. Smoke extract was then assessed at concentrations from 0 percent to 30 percent. To ensure that e-cigarette extracts were tested at equivalent and higher nicotine concentrations than smoke (as possibly experienced by a heavy vaper), vapor was tested at concentrations between 40 percent and 100 percent (over twice the nicotine).

‘Immediately after the wound was made, the cells were immersed in smoke or vapor extract for 20 hours. Smoke decreased cell migration rate in a concentration-dependent manner, completely inhibiting movement of cells towards the wound at concentrations over 20 percent. In stark contrast, vapor from both types of e-cigarette had no effect – cells could migrate into the wounded area, as normal, even at 100 percent concentration and double the amount of nicotine.’