UC Irvine

INTRODUCTION: Tobacco smoking has been implicated in an array of adverse health outcomes, including those that affect adult bone. However, little is known about the impact of tobacco products on developing bone tissue as it develops in the embryo. AIMS AND METHODS: Here, human embryonic stem cells were differentiated into osteoblasts in vitro and concomitantly exposed to various concentrations of smoke solutions from two conventional, one additive-free and two harm-reduction brands of cigarettes. Differentiation inhibition was determined by calcium assays that quantified matrix mineralization and compared to the cytotoxicity of the tobacco product. RESULTS: Exposure to mainstream smoke from conventional and additive-free cigarettes caused no inhibition of cell viability or mineralization, while sidestream smoke (SS) concentration-dependently produced cell death. In contrast, mineralization was inhibited only by the highest mainstream concentration of harm-reduction smoke solution. Additionally, sidestream smoke solution from the harm-reduction cigarettes impeded calcification at concentrations lower than those determined to be cytotoxic for conventional products. CONCLUSIONS: Sidestream smoke impaired in vitro osteogenesis at subtoxic concentrations. In addition, though often perceived as safer, smoke from harm-reduction cigarettes was more potent in inhibiting in vitro osteogenesis than smoke from conventional cigarettes. IMPLICATIONS: This study adds to a growing list of adverse outcomes associated with pre-natal tobacco exposure. Specifically, in vitro exposure to tobacco products interfered with osteogenic differentiation of human embryonic stem cells, a well-established surrogate model for human embryonic bone development. Contrasting a diverse array of tobacco products unveiled that sidestream smoke was generally more developmentally osteotoxic than mainstream smoke and that harm-reduction products may not be less harmful than conventional products, adverse effects that were seemingly independent of nicotine.