Periodontal Disease Differentially Alters the Compressive Responses of Periodontal Fibroblasts

Objectives: In periodontal disease (PD), periodontal integrity is disrupted and the restoration of the damaged bone to its original morphology and composition is inhibited. Matrix metalloproteinases (MMPs) and interleukin-6 (IL-6) are among the key mediators of irreversible tissue destruction in periodontitis. We hypothesized that the normal anabolic response of periodontal ligament (PDL) cells to mechanical inputs is dysregulated in diseased conditions. Studying the key proteolytic mediators of periodontal destruction will help identify how normal mechanical conditions may actually exacerbate disease progression.

Methods: Using real-time polymerase chain reaction, mRNA expression of IL-6, MMP-1 and MMP-8 was studied among human PDL cells from healthy individuals (hPDLs) and PD patients (pPDLs) in response to Cyclic Hydrostatic Compressive Stress (cHCS). PDL cells were taken from freshly extracted teeth and established in cell culture. Application of cHCS relied on a novel pneumatic system consisting of a custom stainless steel pressure vessel, solenoid valve and a high-pressure gas cylinder. Cells were cultured in serum-free medium on 22 mm treated coverslips, mounted into the bioreactor and cHCS at 150 psi was applied 3 hour/day for two days. Total RNA was reverse transcribed into cDNA, which then was amplified by PCR. Genes of interest were compared to the housekeeping gene, HPRT, for an internal standard.

Results: The quantitative analyses of IL-6, MMP-1 and MMP-8 showed that pPDLs exhibited significantly higher basal expression of these targets when compared with hPDLs. In addition, compression of pPDLs further significantly increased expression of IL-6, MMP-1 and MMP-8. In contrast, compression of hPDLs did not significantly modulate these genes.

Conclusion: PDLs differentially express specific pro-inflammatory genes in vitro, depending on the relative health of the tissue from which they were cultured. Compressive forces exerted on these cells can additionally stimulate expression of IL-6, MMP-1 and MMP-8.

Supported by Egyptian Cultural & Educational Bureau.