Artikel
E-cigarette aerosols do not compromise bone integrity compared with mainstream cigarette smoke after six-month inhalation in ApoE-/- mouse model
Suche in Medline nach
Autoren
Veröffentlicht: | 22. Oktober 2019 |
---|
Gliederung
Text
Objectives: Electronic cigarettes (e-cigs) are currently used as a replacement for cigarettes. However, there are limited data on the safety profile of e-cig usage in terms of toxicology or disease risks as compared with that of cigarette smoking. The main objective of this study was to characterize the impact of six-months of inhalation of mainstream cigarette smoke (CS) from a 3R4F reference cigarette and e-cig aerosols on the bone morphology, structure, and bone strength of female ApoE-/- mice.
Methods: In the current study, two-month-old female ApoE-/- mice were randomly allocated to five exposure groups: sham (exposure to fresh, conditioned air), CS from the 3R4F reference cigarette, or three variations of e-cig aerosols. Capillary aerosol generators were used to generate e-cig aerosols using various e-liquids ("CARRIER“ containing humectants alone, „BASE“ containing humectants and 4% nicotine, and „TESTMIX“ containing humectants, 4% nicotine, and flavors). ApoE-/- mice were exposed at matched nicotine concentration, 36 µg/L, to CS and the e-cig aerosols ("BASE“ and „TESTMIX"). Ten animals per group were exposed for three hours per day, five days per week, for six months. Bone integrity analysis was performed using the tibiae. µCT imaging served for cortical and whole bone structure analysis. Three-point bending was used to test biomechanical properties, and histological stainings showed bone morphological details.
Results and conclusion: Animals of all groups showed no significant difference across the groups in body weight or tibial bone weight and lengths. Bone structure analysis using µCT revealed significant reduction in bone volume/total volume (BV/TV) of total bone as well as midshaft cortical bone in the CS group compared to the e-cig aerosol groups: CS versus CARRIER (total bone p<0.001, cortical p<0.05), CS versus BASE (total bone p<0.05), and CS versus TESTMIX (total bone p<0.05). Accordingly, biomechanical analysis showed significantly reduced ultimate load (UL) and stiffness (S) in CS versus Sham (S p<0.05), CS versus CARRIER (UL p<0.05), and CS versus TESTMIX (S p<0.05, UL p<0.01). Histology indicated variation in cortical composition, mainly in the sham group, using Masson Trichrome staining. Also, micro cracks in cortical bone were identified among all groups, showing hypertrophic chondrocytes as signs for endochondral healing identified by Alcian blue staining. In conclusion, mainstream CS significantly compromised bone structure and strength in the ApoE-/- mouse model. In contrast, in the ApoE-/- mouse model none of the e-cig aerosols showed significant changes of biomechanical properties or the ratio of BV/TV after a six-month inhalation exposure.