Fig. 4

Analysis of Fn invasion and its effect on the secretion of proinflammatory factors by cell monolayers. a Illustration of Fn transitioning from a planktonic state to adherence and invasion to gingival epithelial cells. The figure was created using BioRender. Confocal images showing the interactions between Fn and TIGK cell monolayer under normoxic (b) and asymmetric coculture conditions, colocalized with Fn strains 23726 (c), 25586 (d), and 10953 (e). Fn was prelabeled with a red fluorescence dye DiD, and TIGK cells were post-labeled by Alexa Fluor™ 488 Phalloidin for cytoskeleton. MOI of Fn was 50. f Differential invasion of three Fn strains into the gingival epithelial cells (TIGKs) under normoxic and asymmetric coculture conditions for 24 h. The MOI of Fn was 1 (*0.01 < P < 0.05; n = 2, N = 3). g Enzyme-linked immunosorbent assay result of CXCL10 (IP-10) expression levels after infection with different Fn strains. The value was measured by assessing absorbance at 450 nm, with a reference at 570 nm (n = 3, N = 3). h–j Luminex outcome of the difference in expression levels of different pro-inflammatory factors after infection with different Fn strains (*0.01 < P < 0.05, ** P < 0.01; n = 1, N = 3). k Intracellular bacterial counts of Fn 25586 and Fn 10953 after treatment with amoxicillin, metronidazole, and their combination (n = 2, N = 3)