Polymorphonuclear neutrophils and their mediators in gingival tissues from generalized aggressive periodontitis

Impaired polymorphonuclear neutrophil (PMN) functions were generally considered to be related to the onset of generalized aggressive periodontitis (GAgP). However, some research has indicated that the hyperreactivity of PMN seems to be involved in the inflammatory response of GAgP. The present study's main purpose was to provide more evidence about the role of PMN in the pathogenesis of GAgP by surveying PMN infiltration in gingiva and its relationship with the expression of their mediators including intercellular adhesion molecule-1 (ICAM-1), interleukin-8 (IL-8), interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha). The inflammatory response in GAgP was also compared with that in adult periodontitis (AP) and periodontally healthy subjects. Since these PMN mediators were reported to be produced mainly by macrophages, the association between the expression of these PMN mediators and the distribution of macrophages was also investigated.

A total of 25 gingival specimens were obtained from 10 GAgP patients, 10 AP patients, and 5 periodontally healthy subjects. Serial sections were obtained from each specimen, and the following techniques were adopted to investigate the distribution and interrelation of different cells and cytokines. Infiltration of PMN was observed by using hematoxylin and eosin staining. Distribution of the macrophages, identified as CD68+, was shown by using immunohistochemistry. Immunohistochemistry and in situ hybridization were used to detect the expression of ICAM-1, IL-8, IL-1beta, and TNF-alpha in gingival tissues. These techniques were performed in serial sections from each individual specimen.

Large numbers of infiltrating PMNs were observed in gingiva from GAgP. In gingiva from both GAgP and AP, the strongest protein and mRNA expression of IL-8, ICAM-1, IL-1beta, and TNF-alpha were located in pocket epithelium and adjacent connective tissue with large numbers of infiltrating PMNs. In tissues without abundant PMN infiltration, the appearance of positive cells expressing IL-8, ICAM-1, IL-1beta, and TNF-alpha was scattered. CD68+ was distributed sparsely in connective tissue and was hardly seen in pocket epithelium with large numbers of PMN infiltration. The degree of leukocyte infiltration and connective tissue destruction in gingiva from GAgP patients was not distinctly different from that in gingiva from AP. The gingival specimens with heavy PMN infiltration from both GAgP and AP patients presented strong expressions of IL-1beta and TNF-alpha; showed more extensive inflammatory cell infiltration; had severe connective tissue destruction; and presented severe elongation and ulceration of pocket epithelium. In gingiva from healthy subjects, inflammation was minor with visually no PMN, CD68+, or the positive cells of IL-8, ICAM-1, IL-1beta and TNF-alpha expression.

Enhanced accumulation of PMN, which is associated with the upregulation of IL-8, ICAM-1, IL-1beta, and TNF-alpha expression, relates to the severity and activity of GAgP. In addition to macrophages, PMN and/or epithelial cells might also be important sources of IL-8, IL-1beta, and TNF-alpha production in gingiva.