UCSF

Role of Fas Ligand in Apical Periodontitis upon Infection with Oral Anaerobes (Fusobacterium nucleatum )

By Yasaman Ravandoust, DDS

Fusobacterium nucleatum (Fn) is one of the most prevalent anaerobes found in endodontic infections. Our group has shown that Fn aggregates immune cells, upregulates the death-ligand FasL,and induces apoptosis (Jewett 2000, Fraser 2010, Huynh 2011). In this study, we investigated the role of FasL in regulating bone resorption upon murine pulp exposure and infection with Fn and Prevotella intermedia (Pi).

Mandibular first molar pulps from Wild-type, and FasL- deficient mice were exposed and infected with Fn and Pi. Mice with no pulp exposures were the control group. Animals were euthanized after 21 days. Hemi-mandibles were fixed in 10% phosphate-buffered-formalin, and subjected to micro-computed-tomography. The volumetric measurements of the periapical lesions on the mesial and distal roots were calculated and statistically analyzed with ANOVA and Post-

hoc Tukey's test.

Mesial and distal root periapical lesion sizes were significantly larger in Wild-type mice than in FasL deficient mice respectively (p<0.05).

a) Wild type mouse mesial root: 0.17±0.007;

b) FasL-deficient mouse mesial root: 0.12±0.007;

c) Wild type mouse distal root: 0.15±0.008;

d) FasL-deficient mouse distal root: 0.11±0.001

In conclusion, FasL plays an important role in the induction of periapical bone resorption induced by co-infection with Fusobacterium nucleatum & Prevotella intermedia.