Long-term exposure to cigarette smoke influences characteristics in human gingival fibroblasts

Periodontal disease is a chronic inflammatory disease caused by periodontopathic bacteria accumulated in the gingival sulcus and periodontal pocket. Cigarette smoking is a well-established risk factor for periodontal disease, and periodontal tissues in smokers are chronically exposed to cigarette smoke on a long-term basis.

In this study, we investigated the effects of long-term exposure to nicotine or cigarette smoke condensate (CSC) on cellular functions of human gingival fibroblasts (HGFs).

In vitro-maintained HGFs were divided into two groups. The HGFs of the short-term and the long-term culture groups were cultured for 4 and 25 days, respectively, in the presence or absence of nicotine, which is one of the main components of cigarette smoke, or CSC. The cellular proliferation and migration capacities of HGFs exposed to nicotine or CSC were evaluated by WST-1 and wound healing assays. The effects of exposure to nicotine or CSC on the expression of various extracellular matrix (ECM) components, inflammatory cytokines, and senescence-related genes were examined by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. The cellular senescence of HGFs exposed to nicotine or CSC was detected by the senescence-associated β-galactosidase (SA-β-gal) assay. To explore the senescence-associated microRNA (miRNA), we extracted miRNA from the HGFs and the expression profiles were examined by miRNA array.

In short-term culture, no significant changes were observed. Long-term exposure of HGFs to nicotine or CSC significantly suppressed their cellular proliferation and migration and upregulated type Ⅰ collagen, type Ⅲ collagen, interleukin (IL)-6, IL-8, p16, p21, and p53 mRNA expression, and IL-6 and IL-8 protein expression. Furthermore, long-term nicotine or CSC exposure significantly increased the percentage of SA-β-gal-positive HGFs. In addition, long-term nicotine or CSC exposure reduced miR-29b and miR-199a expression to less than 50% of that in the unstimulated HGFs.

These data suggest that long-term smoking habits may reduce wound healing ability, modulate ECM protein homeostasis, stimulate the inflammatory response, and accelerate cellular senescence in HGFs, and consequently accelerate the progression of periodontal diseases.