More evidence that e-cigarettes are as bad as cigarettes for blood vessels, this time on skin

The evidence that e-cigarettes are just as bad as conventional cigarettes for effects on blood and blood vessels keeps piling up.  Aline Sabrina Rau and colleagues at the University of Colorado just published “Electronic Cigarettes Are as Toxic to Skin Flap Survival as Tobacco Cigarettes” in the Annals of Plastic Survey. 
An important factor in wound healing is adequate circulation in small blood vessels.  Inadequate circulation leads to slower healing and even tissue death (necrosis).  Rau and colleagues did an experiment in which they exposed rats to high levels of secondhand cigarette smoke and aerosol from two different Blu e-cigarettes, one that exposed the rats to the same level of airborne nicotine as the tobacco cigarettes and one that exposed them to twice the nicotine.  The rats were exposed for 4 weeks, then surgery done, and the wound measured after another week of exposure.
Bottom line:  The effects on the cigarette smoke and e-cigarette aerosol were the same, independent of the nicotine level.
Rau and colleagues explained this finding as follows:
These results may suggest that nicotine may in fact exhibit a threshold effect. Once a certain level of plasma nicotine is obtained, the vasoconstrictive (ie, hypoxic [oxygen-starved]) effects of nicotine may have been maximized and will not increase, even with higher plasma nicotine levels. An additional explanation may be that the particles with a hydrodynamic diameter of 2.5 μm or less (fine particulate matter) within the vapor, rather than the nicotine, or in conjunction with nicotine, are having a drastic negative effect on flap physiology. Fine particles are concerning because they can penetrate into the lung tissue and blood stream unfiltered and can cause serious health effects. It has been established that cigarette smoke causes increased platelet aggregation, and that the fine particulate matter was the main contributor to antagonizing platelet functions (more so than nicotine). A recent study demonstrated that the fine particular matter within e-cigarette vapor alters platelet function to the same extent as the particulate matter within tobacco smoke. The results of this study may corroborate these results. The e-cigarette fine particulate matter may be causing microthrombosis [tiny blood clots] of the vessels, just as has been seen with conventional cigarettes.
These effects reflect the same processes by which cigarettes and e-cigarettes increase risk to the cardiovascular system and increase the risk of heart disease and triggering a heart attack.
These effects on small blood vessels in skin is why smoking causes wrinkles.
While, as far as I know, no one has yet studied these kinds of effects on heat-not-burn products like Philip Morris iQOS, we already know that, like cigarettes and e-cigarettes, these products deliver an aerosol of nicotine and ultrafine particles, precisely the same elements that are causing these effects.  Public health experts and regulatory authorities like the FDA need to carefully consider these important vascular effects, before jumping on the iQOS bandwagon.
Here is the abstract from the paper:
PURPOSE:  Electronic cigarettes (e-cigarettes) have become increasingly popular. However, information about the health risks associated with e-cigarette use is sparse. Currently, no published studies examine the effects of chronic e-cigarette exposure on microcirculation or perfusion. Using a rat skin flap model, we examined the toxic microcirculatory effects e-cigarettes may have in comparison with tobacco cigarettes.
METHODS: Fifty-eight rats were randomized to either exposure to room air, tobacco cigarette smoke, medium-nicotine content (1.2%) e-cigarette vapor, or a high-nicotine content (2.4%) e-cigarette vapor. After 4 weeks of exposure, a random pattern, 3 × 9 cm skin flap was elevated on the dorsum of the rats. At 5 weeks, flap survival was evaluated quantitatively, and the rats were euthanized. Plasma was collected for nicotine and cotinine analysis, and flap tissues were harvested for histopathological analysis.
RESULTS: Evaluation of the dorsal skin flaps demonstrated significantly increased necrosis in the vapor and tobacco groups. The average necrosis within the groups was as follows: control 19.23%, high-dose vapor 28.61%, medium-dose vapor 35.93%, and tobacco cigarette 30.15%. Although the e-cigarette and tobacco cigarette groups did not differ significantly, each individual group had significantly more necrosis than the control group (P<0.05). These results were corroborated with histopathological analysis of hypoxic tissue.
CONCLUSIONS:  Both the medium-content and high-nicotine content e-cigarette exposure groups had similar amounts of flap necrosis and hypoxia when compared with the tobacco cigarette exposure group. Nicotine-containing e-cigarette vapor is similarly toxic to skin flap survival as tobacco cigarettes.
The full citation is:  Rau AS, Reinikovaite V, Schmidt EP, Taraseviciene-Stewart L, Deleyiannis FW. Electronic Cigarettes Are as Toxic to Skin Flap Survival as Tobacco Cigarettes. Ann Plast Surg. 2017 Mar 1. doi: 10.1097/SAP.0000000000000998. [Epub ahead of print]