Site-Specific Neutrophil Migration and CXCL2 Expression in Periodontal Tissue

Abstract

The oral microbial community is the best-characterized bacterial ecosystem in the human host. It has been shown in the mouse that oral commensal bacteria significantly contribute to clinically healthy periodontal homeostasis by influencing the number of neutrophils that migrate from the vasculature to the junctional epithelium. Furthermore, in clinically healthy tissue, the neutrophil response to oral commensal bacteria is associated with the select expression of the neutrophil chemokine CXCL2 but not CXCL1. This preliminary study examined the contribution of commensal bacteria on neutrophil location across the tooth/gingival interface. Tissue sections from the root associated mesial (anterior) of the second molar to the root associated distal (posterior) of the second molar were examined for neutrophils and the expression of the neutrophil chemokine ligands CXCL1 and CXCL2. It was found that both the number of neutrophils as well as the expression of CXCL2 but not CXCL1 was significantly increased in tissue sections close to the interdental region, consistent with the notion of select tissue expression patterns for neutrophil chemokine expression and subsequent neutrophil location. Furthermore, mice gavaged with either oral Streptococcus or Lactobacillus sp. bacteria induced a location pattern of neutrophils and CXCL2 expression similar to the normal oral flora. These data indicate for the first time select neutrophil location and chemokine expression patterns associated with clinically healthy tissue. The results reveal an increased inflammatory load upon approaching the interproximal region, which is consistent with the observation that the interproximal region often reveals early clinical signs of periodontal disease.

Human neutrophils and oral microbiota: a constant tug‐of‐war between a harmonious and a discordant coexistence

“…compare the expression levels of CXCL2 and neutrophil location in different areas of the junctional epithelium across the tooth, among GF, SPF and GF mice which were gavaged with single commensal oral bacteria like Streptococcus sp. or Lactobacillus sp . Neutrophils show a similar location pattern in the periodontium of the SPF mice and bacteria‐gavaged GF mice, but this is distinct from the pattern seen in GF mice.…”

“…In the presence of the indigenous oral bacterial community, both the numbers of neutrophils as well as the levels of the CXCL2 chemokine are enhanced in the interdental region of the periodontal tissue. This provides novel and valuable information about how the commensal organisms modulate the innate immune response to maintain homeostasis in the oral cavity …”

Toll‐like receptor‐2 and ‐4 responses regulate neutrophil infiltration into the junctional epithelium and significantly contribute to the composition of the oral microbiota

“…This study demonstrates that at least in mice, direct recognition of bacterial components by either TLR2 or TLR4 is not required for neutrophil migration into the gingival sulcus. Rather, the key activation pathway that elicits neutrophil migration in healthy gingiva remains unknown, but appears to be dependent on both MyD88 and bacteria …”

“…Similar to previously published methods, mice were euthanized by cervical dislocation and tissues were harvested for histological processing. Maxillae and mandibles were immediately fixed overnight on a shaker at 4˚C and rinsed with 70% ethanol daily for 1 week, gradually decreasing the rinses to once every other day until dissection.…”

“…Detection of neutrophils on paraffin embedded samples by immunohistochemistry (IHC). Every fifth slide was picked serially from the root‐associated first molar to the root‐associated second molar as previously described, resulting in ≈30 sections (60 JE; 15 slides) per half mandible. Tissue sections were deparaffinized and rehydrated using a gradation of diluted ethanol.…”