From gingiva to multiple organs in mice: The trace of Porphyromonas gingivalis via in vivo imaging

Periodontitis is associated with systemic health. One of the underlying mechanisms is the translocation of periodontal pathogens, among which Porphyromonas gingivalis (Pg) is the most common. Here, we aimed to illustrate the biodistribution and dynamics of Pg from gingiva to multiple organs through blood circulation. Pg tagged by Cyanine 7 (Cy7-Pg) was injected into the gingiva of healthy and periodontitis mice. In vivo imaging system (IVIS) was applied to monitor the distribution of Cy7-Pg in multiple organs which were isolated at serial timepoints. Polymerase chain reaction (PCR) was conducted to determine the Pg DNA copies in the gingiva, blood and organs. Cy7-Pg in the gingiva and organs was also confirmed by frozen section staining. Furthermore, to figure out whether the bacteremia derived from oral-gut axis, mice received gavage of Cy7-Pg. Then the blood and organ samples were detected in the similar way as above. Intra-gingival injection induced larger amounts of Cy7-Pg accumulating in the gingiva of periodontitis mice (P < 0.05) as confirmed by above three methods. Twenty minutes after injection, Pg DNA copies in the blood of periodontitis group were 36.3-fold higher than healthy group (P < 0.05). IVIS results, combined with PCR and frozen sections, demonstrated periodontitis induced longer retention with higher amounts of Cy7-Pg in the periodontitis group. Pg was enriched more significantly in the liver for the longer duration than the kidney and pancreas. Our study showed Pg, which accumulated in the gingiva, could translocate through blood circulation to multiple organs with varied duration and amounts.