GSE118304
Transcriptome dynamics of oral polymorphonuclear neutrophils during experimental gingivitis
Oral polymorphonuclear neutrophils (oPMNs) are essential for the maintenance of oral health. Functionally active oPMNs have been described in oral health, gingivitis and periodontitis. Interestingly, recent evidence showed that oPMNs from chronic periodontitis patients have a similar functional and reactivity pattern compared to oPMNs from healthy subjects. However, it remains unknown whether oPMNs respond to the initiation and resolution of gingival inflammation. Therefore, this study aimed to evaluate the oPMNs' transcriptional responses during the initiation and resolution of an experimentally induced gingivitis.     Oral rinses were obtained from 8 subjects at 4 different time points during the experiment for the isolation of oPMNs; day 0 (baseline), day 9 (during gingivitis challenge), day 14 (end of the challenge) and day 21 (resolution). Transcriptome of oPMNs was determined by RNAsequencing. Differentially expressed genes (DEGs) was selected at P<0.01 level, and evaluated for pathway regulation at different time points using Ingenuity Pathway Analysis suite.     During the gingivitis challenge, dental plaque levels and gingival bleeding levels were significantly increased at day 14 compared to baseline. Transcriptome analysis indicate four major clusters of DEGs, which consisted of a group of 256 initial response DEGs (day 9 only), 221 late response DEGs (day 14 only), 53 persistent response DEGs (consistent at day 9 and day 14), and a group of 524 DEGs showing response only after the gingivitis challenge (day 21 only). Pathway analysis of the initial response DEGs showed their involvement in many immune regulatory pathways (interleukin signaling, reactive oxygen species processes and granulocyte adhesion and diapedesis). Late responding DEGs mainly showed activation of signaling pathways and phagosome formation as part of the phagocytosis process, whereas DEGs at day 21 were involved in epithelial adherence signaling and other miscellaneous related signaling pathways.    This study showed that oPMNs have specific expression profiles during the development and resolution of experimental gingivitis. Even though, the specific observed pathways were not identical within each time point, the altered pathways indicate PMN responses in general and suggests an immunomodulatory role for the oPMNs. The oPMNs may therefore play a co-controlling part in the initiation and resolution of gingival inflammation. Overall design: Time course study in which 8 healthy individuals were asked to refrain from any form of oral hygiene for a period of 2 weeks. Data were derived from samples taken at start (day 0), day 9, and day 14. After this timepoint the habitual oral hygiene routine was re-established by each participant. At the end of the study (day 21) a final sample was collected from all participants.