Comparative analysis of expression of microbial sensing molecules in mucosal tissues with periodontal disease

Host-derived pattern recognition receptors (PRRs) are necessary for effective innate immune engagement of pathogens that express microbial-associated molecular patterns (MAMP) ligands for these PRRs. This study used a nonhuman primate model to evaluate the expression of these sensing molecules in gingival tissues. Macaca mulatta aged 12-24 with a healthy periodontium (n = 13) or periodontitis (n = 11) provided gingival tissues for assessment of naturally-occurring periodontitis. An additional group of animals (12-23 years; n = 18) was subjected to a 5 month longitudinal study examining the initiation and progression of periodontitis, RNA was isolated and microarray analysis conducted for gene expression of the sensing PRRs. The results demonstrated increased expression of various PRRs in naturally-occurring established periodontitis. Selected PRRs also correlated with both bleeding on probing (BOP) and pocket depth (PD) in the animals. The longitudinal model demonstrated multiple TLRs, as well as selected other PRRs that were significantly increased by 2 weeks during initiation of the lesion. While gene expression levels of various PRRs correlated with BOP and PD at baseline and resolution of disease, few correlated with these clinical parameters during initiation and progression of the lesion. These findings suggest that the levels of various PRRs are affected in established periodontitis lesions, and that PRR expression increased most dramatically during the initiation of the disease process, presumably in response to the juxtaposed microbial challenge to the tissues and goal of reestablishing homeostasis.