Gingival Toll-like receptor and cytokine mRNA levels in equine periodontitis and oral health

REASONS FOR PERFORMING STUDY: Equine periodontitis is a common and painful condition. Despite this, the disease often goes unnoticed by owners and is thus a major welfare concern. The aetiopathogenesis of the condition remains poorly understood with few recent studies performed. The innate immune system is known to play an important role in human periodontitis, but its role in equine periodontitis has not been examined.

OBJECTIVES: To quantify the mRNA levels of Toll-like receptors (TLRs) and cytokines in gingival tissue from orally healthy horses and those affected by periodontitis.

STUDY DESIGN: Observational study.

METHODS: Gingival tissue samples were taken post mortem from 13 horses with no clinical signs of oral disease and 20 horses with periodontitis. mRNA levels of TLR2, TLR4 and TLR9 and cytokines IL-1β, TNFα, IL-4, IL-6, IL-10, IL-12, IL-17 and IFN-ɣ were determined using quantitative real-time PCR. Statistical significance of results was assessed using appropriate t-tests.

RESULTS: mRNA levels of all TLRs and cytokines were up-regulated in equine periodontitis. Significant increases in mRNA levels of TLR2, TLR9, IL-4, IL-10, IL-12 (p≤0.05) and IFN-ɣ (p≤0.01) were observed for both un-weighted and age-weighted analyses of diseased gingival tissue samples compared to healthy gingival samples. When comparing periodontitis lesions to healthy gingival control samples from the same horse, significant increases in mRNA levels of TLR4, TLR9, IL-10, IFN-ɣ (p≤0.05), TLR2, IL-1β and IL-12p35 (p≤0.01) were observed.

CONCLUSIONS: This study has provided an initial insight into the involvement of the immune system in equine periodontitis. Increased mRNA levels of TLR2, TLR4 and TLR9 indicate substantial microbial challenge in diseased gingival tissue. A mixed Th1/Th2/Th17 cytokine response is produced in equine periodontitis. Further studies are required to more fully characterise the role of the innate immune system in this disease. This article is protected by copyright. All rights reserved.