To elucidate whether APN may counteract critical actions of P. gingivalis on periodontal tissues, experimental periodontitis was established in APN−/− mice (Jax #008195) and WT mice (Jax #000664). APN−/− mice were maintained as reported previously (Tu et al., 2011 (link)). 12-week-old male mice were used in this study. APN−/− mice were divided into 3 groups (n = 5): periodontitis only, periodontitis+ APN infusion, and control without periodontitis and APN infusion. WT mice (n = 5) were used as negative control. Experimental periodontitis was induced as previously described (Zhang et al., 2014 (link)). For APN infusion, an Alzet micro-osmotic pump (model 1004, Durect Corporation) containing 1 mg/ml of APN was inserted subcutaneously in the back of each mouse following periodontitis induction. The pumps delivered 2.5 μg of recombinant APN per day. Mice were euthanized 10 days after periodontitis induction.