(423) ARE E-CIGARETTES SAFER THAN COMBUSTIBLE TOBACCO ON HUMAN TYPE II ALVEOLAR CELLS AND MESENCHYMAL STEM CELLS?

Abstract

Electronic cigarettes (e-cigarettes) are promoted as safer alternatives to combustible cigarettes. However, the health burden and effects of their long-term use remain unidentified. This study evaluates the extent and reversibility of cellular damage following exposure to cigarette and e-cigarette smoke aerosols, in vitro, of human type II alveolar cells (A549) and bone marrow-derived mesenchymal stem cells (BM-MSCs). The survival, levels of reactive oxygen species (ROS) generation and expression of epithelial-to-mesenchymal transition (EMT) markers are reported for A549 cells. BM-MSCs are evaluated for their survival and their differentiation potential into the osteogenic lineage. Cigarette smoke aerosols irreversibly reduce cell proliferation in A549 cells and enhance ROS production. E-cigarette smoke aerosols also permanently reduce proliferation of A549 cells, downregulated the gene expression of connexin 43 and E-cadherin and upregulated that of N-cadherin; promoting EMT. The integrity of BM-MSC- mediated cellular repair, described in terms of BM-MSC proliferation and osteogenic differentiation, was compromised by both cigarette and e-cigarette aerosol extracts. However, BM-MSCs were able to recover their proliferative ability and osteogenic differentiation upon e-cigarette, but not combustible cigarette, washout. The cellular damage caused by cigarette aerosols is irreversible in A549 cells and on BM-MSCs; while e cigarettes were associated with less alterations and greater, albeit incomplete, recovery of some cellular functions after smoke washout. These results shed light on the safety of e-cigarettes, attempt to explain long-term illnesses in chronic smokers and feed into future public policies on tobacco control.