Toll-like receptor 4 expression in the epithelium of inflammatory periapical lesions. An immunohistochemical study

  • R. Leonardi University of Catania, Italy.
  • R.E. Perrotta University of Catania, Italy.
  • C. Loreto | carla.loreto@unict.it University of Catania, Italy.
  • G. Musumeci University of Catania, Italy.
  • S. Crimi University of Messina, Italy.
  • J.N. dos Santos Federal University of Bahia, Brazil.
  • M.C. Rusu “Carol Davila” University of Medicine and Pharmacy, Romania.
  • P. Bufo University of Foggia, Italy.
  • E. Barbato Sapienza University of Rome, Italy.
  • G. Pannone University of Foggia, Italy.

Abstract

Toll-like receptors (TLR) are essential for the innate immune response against invading pathogens and have been described in immunocompetent cells of areas affected by periapical disease. Besides initiating the inflammatory response, they also directly regulate epithelial cell proliferation and survival in a variety of settings. This study evaluates the in situ expression of TLR4 in periapical granulomas (PG) and radicular cysts, focusing on the epithelial compartment. Twenty-one periapical cysts (PC) and 10 PG were analyzed; 7 dentigerous non-inflamed follicular cyst (DC) served as control. TLR4 expression was assessed by immunohistochemistry. TLR4 immunoreaction products were detected in the epithelium of all specimens, with a higher percentage of immunostained cells in PG. Although TLR4 overexpression was detected in both PG and PC, there were differences that seemed to be related to the nature of the lesion, since in PG all epithelial cells of strands, islands and trabeculae were strongly immunoreactive for TLR4, whereas in PC only some areas of the basal and suprabasal epithelial layers were immunostained. This staining pattern is consistent with the action of TLR4: in PG it could promote formation of epithelial cell rests of Malassez and in epithelial strands and islands the enhancement of cell survival, proliferation and migration, whereas in PC TLR4 could protect the lining epithelium from extensive apoptosis. These findings go some way towards answering the intriguing question of why many epithelial strands or islands in PG and the lining epithelium of apical cysts regress after non-surgical endodontic therapy, and suggest that TLR4 plays a key role in the pathobiology of the inflammatory process related to periapical disease.

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Author Biographies

R. Leonardi, University of Catania
Department of Medical and Surgical Science, Dentistry Section.
R.E. Perrotta, University of Catania
Department of Medical and Surgical Science. Plastic Surgery Section
C. Loreto, University of Catania
Department of BioMedical Sciences, Human Anatomy and Histology Section, School of Medicine
G. Musumeci, University of Catania
Department of BioMedical Sciences, Human Anatomy and Histology Section, School of Medicine
S. Crimi, University of Messina
Department of Maxillofacial Surgery
J.N. dos Santos, Federal University of Bahia
Faculty of Dentistry, Surgical Pathology Laboratory
M.C. Rusu, “Carol Davila” University of Medicine and Pharmacy
Division of Anatomy, Faculty of Dental Medicine
P. Bufo, University of Foggia
Department of Clinical and Experimental Medicine, Pathological Anatomy Section
E. Barbato, Sapienza University of Rome
Department of Oral and Maxillofacial Sciences, School of Dentistry,
G. Pannone, University of Foggia
Department of Clinical and Experimental Medicine, Institute of Pathology and Cytopathology
Published
2015-10-26
Section
Brief Reports
Keywords:
TLR4, periapical inflammatory granulomas, radicular cysts.
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How to Cite
Leonardi, R., Perrotta, R., Loreto, C., Musumeci, G., Crimi, S., dos Santos, J., Rusu, M., Bufo, P., Barbato, E., & Pannone, G. (2015). Toll-like receptor 4 expression in the epithelium of inflammatory periapical lesions. An immunohistochemical study. European Journal of Histochemistry, 59(4). https://doi.org/10.4081/ejh.2015.2547

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