Repeated cigarette smoke exposure attenuates the proliferation rate of primary human lung fibroblasts in vitro

BackgroundLung fibroblasts are crucial structural cells involved in airway remodelling and tissue maintenance. The study aimed to analyze the effect of cigarette smoke extract (CSE) on primary human lung fibroblasts at various stages of proliferation to assess whether an initial exposure could exert a protective effect against subsequent exposures. MethodsWe examined the effect of CSE on fibroblasts isolated from 15 donors who had undergone lung surgery. Fibroblast cultures were exposed to 2% CSE early (day 5-7), late (day 9-11), or at both time points (double). Cell counts and viability tests were performed every 2 days. Changes in proliferation rates were determined immediately at the end of each 2-day exposure as well as 2 days afterwards, until the end of the experiment with a plateau of proliferation. Differences between exposures were analyzed by comparing proliferation rates by ANOVA with adjusted post-hoc analyses. ResultsEarly-, late- and double-CSE exposed cultures showed lower proliferation rates (p<0.05 each) compared to unexposed cultures. The response to late-CSE exposure varied depending on whether an initial CSE exposure had occurred, suggesting a protective effect from the early exposure. Changes observed over the 2-day exposure period and the subsequent 2 days (a total of 4 days) yielded similar results to those recorded during just the 2-day exposure period. Proliferation rates varied among cells from different donors, but responses correlated across different exposure regimens, indicating inherent differences in susceptibility to CSE. ConclusionsRepeated CSE exposures attenuated the proliferation of primary human lung fibroblasts more strongly than a single exposure, despite the fact that an early CSE exposure appeared to protect against the CSE in repetitively exposed fibroblast cultures. Our results highlight that while significant differences may occur among primary cells from different donors in vitro, responses can remain consistent across various exposure conditions.