RANHUI XI
| RANHUI XI |
Ranhui Xi1, Marco Tizzano1, Robert.F. Margolskee2
1Department of Basic & Translational Sciences, University of Pennsylvania, School of Dental Medicine; 2Monell Chemical Senses Center
Introduction
Solitary Chemosensory Cells (SCCs) in the airways, gut and urogenital tract are involved in innate immune responses. We recently reported SCCs expressing a T2R-mediated signaling transduction cascade in mouse gingival tissue. Gingival SCCs play a role in oral microbiome regulation and protection against periodontitis-- affecting 64 million in the US alone. Determining the role of gSCCs in periodontitis can lead to the development of new pharmacological strategies for human oral health.
Methods
A total number of 112 cohoused mice, including WT (wild-type), Gnat3(-/-), TrpM5(-/-), and Skn1a(-/-) mice, were used in this study. Ligature-induced experimental periodontitis was produced by placing a small diameter silk sling ligature around the left maxillary second molar. After one week, the maxillary bone was harvested and processed with a micro-CT scanner (uct-45, Scanco). Using Dragonfly (v2020.2), we developed a 3D deep learning model to measure the alveolar bone volume and density. RNA-seq analysis of gingival samples from ligatured and control side for all genotypes (each genotype n=3) was used to study the expression level of inflammatory and other genes differentially expressed.
Results
A total number of 112 cohoused mice, including WT (wild-type), Gnat3(-/-), TrpM5(-/-), and Skn1a(-/-) mice, were used in this study. Ligature-induced experimental periodontitis was produced by placing a small diameter silk sling ligature around the left maxillary second molar. After one week, the maxillary bone was harvested and processed with a micro-CT scanner (uct-45, Scanco). Using Ligatured WT mice lost 29.56% of the alveolar bone volume compared to the un-ligatured baseline, while Gnat3(-/-) mice lost 34.32% (P<0.01), and Skn1a(-/-) mice lost 37.46% (P<0.05). The bone density was reduced in Gnat3(-/-) and Skn1a(-/-) compared to WT mice (P<0.05). No significant differences in alveolar bone volume and density were found in TrpM5(-/-) mice or any heterozygotes (+/-) compared to WT mice. RNA-seq data revealed changes in inflammatory marker genes consistent with the bone loss of Gnat3(-/-)and Skn1a(-/-). In Skn1a(-/-) mice the expression of interleukin-36 family of cytokines, including Il36ra (Il1f5), Il36a (Il1f6) and Il36b (Il1f8) was downregulated. Il-36 signaling system induces the expression of several antimicrobial peptides (AMPs), which explains the downregulation of beta-defensin-4 in the ligatured Skn1a(-/-).
Conclusion
SCCs have a functional role in periodontitis. The lack of Gnat3 or Skn1a increases bone-loss and inflammation by reducing AMPs and cytokine production.