Abstract
Background: Periodontitis is an inflammatory condition of the tooth-supporting structures initiated and perpetuated by pathogenic bacteria present in the dental plaque biofilm. In periodontitis, immune cells infiltrate the periodontium to prevent bacterial insult. Macrophages derived from monocytes play an important role in antigen presentation to lymphocytes. However, they are also implicated in causing periodontal destruction and bystander damage to the host tissues. Objectives: The objective of the present study was to quantify the cytokine profile of gingival crevicular fluid (GCF) samples obtained from patients with periodontitis. The study further aimed to assess if GCF of periodontitis patients could convert CD14+ monocytes into macrophages of destructive phenotype in an in vitro setting. The secondary objectives of the study were to assess if macrophages that resulted from GCF treatment of monocytes could affect the synthetic properties, stemness, expression of extracellular matrix proteins, adhesion molecules expressed by gingival stem cells, gingival mesenchymal stromal cells, and osteoblasts. Methods: GCF, blood, and gingival tissue samples were obtained from periodontitis subjects and healthy individuals based on specific protocols. Cytokine profiles of the GCF samples were analyzed. CD14+ monocytes were isolated from whole blood, cultured, and treated with the GCF of periodontitis patients to observe if they differentiated into macrophages. Further, the macrophages were assessed for a phenotype by surface marker analysis and cytokine assays. These macrophages were co-cultured with gingival stem cells, epithelial, stromal cells, and osteoblasts to assess the effects of the macrophages on the synthetic activity of the cells. Results: The GCF samples of periodontitis patients had significantly higher levels of IFN gamma, M-CSF, and GM-CSF. Administration of the GCF samples to CD14+ monocytes resulted in their conversion to macrophages that tested positive for CD80, CD86, and CD206. These macrophages produced increased levels of IL-1β, TNF-α, and IL-6. Co-culture of the macrophages with gingival stem cells, epithelial cells, and stromal cells resulted in increased cytotoxicity and apoptotic rates to the gingival cells. A reduced expression of markers related to stemness, extracellular matrix, and adhesion namely OCT4, NANOG, KRT5, POSTN, COL3A1, CDH1, and CDH3 were seen. The macrophages profoundly affected the production of mineralized nodules by osteoblasts and significantly reduced the expression of COL1A1, OSX, and OCN genes. Conclusion: In periodontitis patients, blood-derived monocytes transform into macrophages of a destructive phenotype due to the characteristic cytokine environment of their GCF. Further, the macrophages affect the genotype and phenotype of the resident cells of the periodontium, aggravate periodontal destruction, as well as jeopardize periodontal healing and resolution of inflammation.
Highlights
Periodontitis is an inflammatory condition of microbial etiology that affects the toothsupporting tissues collectively referred to as the periodontium
The present study aimed to quantify the cytokine profile of gingival crevicular fluid (GCF) samples obtained from patients with periodontitis and sought to examine whether GCF of periodontitis patients convert could convert monocytes into macrophages of destructive phenotype in an could monocytes into macrophages of destructive phenotype in an in vitro in vitro setting
Exclusion criteria, and details of sample collection: GCF samples were colcollected from patients diagnosed with generalized periodontitis with sites in all lected from 10 patients diagnosed with generalized periodontitis with sites in all 4 quad4rants quadrants presenting with 3/Stage
Summary
Periodontitis is an inflammatory condition of microbial etiology that affects the toothsupporting tissues collectively referred to as the periodontium. Plaque elicits an inflammatory response in the gingiva that is characterized by an infiltration of this tissue initially by polymorphonuclear leukocytes that predominantly constitute the innate immune response This is succeeded by the recruitment and movement of monocyte-derived macrophages, T and B lymphocytes as a part of the specific or adaptive immune response [1]. Periodontitis is a progression of inflammation that spreads from the gingival tissues to involve and destroy the underlying periodontal ligament, cementum, and alveolar bone resulting in the formation of periodontal pockets associated with clinically appreciable attachment loss and tooth mobility This can lead to tooth loss, aesthetic, and functional concerns for the afflicted patient [2]. These macrophages were co-cultured with gingival stem cells, epithelial, stromal cells, and osteoblasts to assess the effects of the macrophages on the synthetic activity of the cells
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