PDL Fibroblast Attachment to Fibronectin Increases Resistance to Cigarette Smoke

Objectives:  The periodontal ligament (PDL) is the connective tissue that anchors the cementum of the teeth to the alveolar process.  PDL fibroblasts are the primary cell of the ligament and are responsible for its remodeling and maintenance.  Periodontal disease is increased among smokers in both incidence and severity.  It is believed that the primary mechanisms of this increase are the systemic effects of smoking, such as the inhibition of the immune response.  This study looks at the direct effect that smoking has on PDL fibroblast survival, focusing on the role of cell-ECM interactions in promoting resistance to the toxins found within cigarette smoke.

Methods:   PDL cells were plated for various times on either tissue culture plastic or select ECM proteins; collagen Type I or fibronectin.  Cells were exposed to various concentrations of Cigarette Smoke Extract (CSE) during or after the attachment process.  Cells were labeled with calcein-AM, and visualized using a fluorescent microscope.  Cell survival was quantified via relative fluorescence using a fluorescent plate reader.

Results: Cells allowed to attach to tissue culture plastic for 48 hours displayed significantly reduced survival following treatment with 1.5% CSE for 24 hours.  With increased attachment times, cells displayed increasing resistance to CSE, with 80% survival of cells by 6 days to 5% CSE.  This decrease in sensitivity to CSE was independent of soluble factors present in PDL cell conditioned media.  Furthermore, initial cell attachment to fibronectin but not collagen Type I significantly increased the survival of PDL cells. 

Conclusions:   This study shows that cell-ECM interactions increase the survival of PDL cells exposed to CSE.  It also demonstrates that PDL cells alter their ECM environment to improve their resistance to CSE, possibly by depositing fibronectin on their underlying substrata.  Thus, cell-ECM interactions likely affect the healing of the periodontal ligament in smokers.