Published online Aug 26, 2020. doi: 10.4252/wjsc.v12.i8.841
Peer-review started: February 25, 2020
First decision: May 26, 2020
Revised: July 17, 2020
Accepted: August 1, 2020
Article in press: August 1, 2020
Published online: August 26, 2020
Cigarette smoking (CS) is the most common method of consuming tobacco. Deleterious effects on bone integrity, increased incidence of fractures, and delayed fracture healing are all associated with CS. Tobacco combusted at about 800 °C generates approximately 6500 molecular species, more than 150 of which have been identified as toxic compounds. New approaches have been on developing reduced-risk alternatives for smokers that maintain the smoking ritual, while providing the same levels of nicotine as conventional cigarettes with less harmful constituents.
New technologies designed to develop a reduced-risk alternative for smokers are based on electronic nicotine delivery systems, such as e-cigarettes and tobacco heating systems (THS). Instead of burning tobacco, THS heat tobacco rolled up in a stick form up to 350 °C (avoiding combustion and formation of ashes). THS contain tobacco and convey the feeling of smoking a conventional cigarette. Several studies have demonstrated reduced levels of toxic and harmful compounds from electronic nicotine delivery systems.
The present study aim to examine the effects of THS on osteoprogenitor cell viability and function compared to conventional CS.
Human immortalized mesenchymal stem cells and primary human pre-osteoblasts isolated from cancellous bone samples were osteogenically differentiated with aqueous extracts generated from either the THS 2.4 “IQOS” or conventional “Marlboro” cigarettes for up to 21 d. Cell viability was analyzed using resazurin conversion assay (mitochondrial activity) and calcein-AM staining (esterase activity). Osteogenic differentiation and bone cell function were evaluated using alkaline phosphatase (AP) activity, while matrix formation was analyzed through alizarin red staining. Primary cilia structure was examined by acetylated α-tubulin immunofluorescent staining. Free radical production was evaluated with 2′,7′-dichlorofluorescein-diacetate assay.
THS is significantly less toxic to bone cells than CS when analyzed by mitochondrial and esterase activity (P < 0.001). No significant differences in cytotoxicity between the diverse flavors of THS were observed. Harmful effects from THS on bone cell function were observed only at non-physiological concentrations. In contrast, conventional cigarettes significantly reduced the AP activity (by two-fold) and matrix mineralization (four-fold) at low concentrations. Moreover, morphologic analysis of primary cilia revealed no significant changes in the length of the organelle involved in osteogenesis of osteoprogenitor cells, nor in the number of ciliated cells following THS treatment. Assessment of free radical production demonstrated that THS induced significantly less oxidative stress than conventional CS in osteoprogenitor cells.
The present study demonstrate reductions in the harmful effects on bone-forming cells and bone progenitor cells treated with THS compared to conventional cigarettes.
THS could be a potential alternative for smokers to maintain appropriate bone homeostasis and delay development of secondary osteoporosis, which consequently would reduce health system costs.