Cigarette consumption negatively impacts bone quality and is a risk-factor for the development of multiple bone associated disorders, due to the highly vascularised structure of bone being exposed to systemic factors. However, the impact on bone to electronic cigarette (e-cigarette) use, which contains high doses of nicotine and other compounds including flavouring chemicals, metal particulates and carbonyls, is poorly understood. Here, we present the first evidence demonstrating the impact of e-cigarette vapour condensate (replicating changes in e-cigarette liquid chemical structure that occur upon device usage), on human primary osteoblast viability and function. 24 h exposure of osteoblasts to e-cigarette vapour condensate, generated from either second or third generation devices, significantly reduced osteoblast viability in a dose dependent manner, with condensate generated from the more powerful third generation device having greater toxicity. This effect was mediated in-part by nicotine, since exposure to nicotine-free condensate of an equal concentration had a less toxic effect. The detrimental effect of e-cigarette vapour condensate on osteoblast viability was rescued by co-treatment with the antioxidant N-Acetyl-L-cysteine (NAC), indicating toxicity may also be driven by reactive species generated upon device usage. Finally, non-toxic doses of either second or third generation condensate significantly blunted osteoblast osteoprotegerin secretion after 24 h, which was sustained for up to 7 days. In summary we demonstrate that e-cigarette vapour condensate, generated from commonly used second and third generation devices, can significantly reduce osteoblast viability and impair osteoblast function, at physiologically relevant doses. These data highlight the need for further investigation to inform users of the potential risks of e-cigarette use on bone health, including, accelerating bone associated disease progression, impacting skeletal development in younger users and to advise patients following orthopaedic surgery, dental surgery, or injury to maximise bone healing.
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