Age-Associated Differential Salivary Immune Profiles in Post-Non-Surgical Periodontal Therapy Subjects

Periodontal Disease (PD) is the second most prevalent oral condition worldwide and has been linked with other systemic conditions. This inflammatory disease primarily occurs due to biofilm dysbiosis with periopathogens that triggers the host immune system to elicit exaggerated responses. Aging has been reported to affect the immune system, leading to increased effects on age-related diseases, including PD. Examining how aging affects immunobiology of PD and its resolution can uncover novel mechanisms that may cater towards the treatment of aging subjects. Saliva and gingival crevicular fluid (GCF) can allow us to monitor immune changes non-invasively by evaluating the biomarkers involved in the disease process. The objective of this study is to dissect mechanisms of immune perturbation in geriatric and young-middle age PD patients before and after non-surgical periodontal therapy (NSPT, scaling and root planing). Periodontally healthy young and geriatric patients were included as control groups. Clinical parameters including probing depth (PPD), bleeding on probing (BOP), & plaque index (PI) were measured pre- & post-NSPT. Salivary immune cells were assessed by flow cytometry and GCF cytokines were quantified by multiplex. To measure the bacterial burden, key virulence factors of A. actinomycetemcomitans and P. gingivalis were quantified by RT-qPCR. Our results show reduction of clinical parameters for both, young-middle aged (YMA) and geriatric (G) groups post-NSPT. However, NSPT significantly reduces bacterial burden in young subjects but not in geriatric patients. GCF assessment by periotron also indicates significantly higher reduction in YMA group post-therapy compared to geriatric PD subjects. This correlates with salivary cytology showing differential impact of NSPT on immune cell abundance with less reduction in geriatric subjects compared to YMA cohort showed significant reduction in these inflammatory T cells and concomitant increase in immunoregulatory Tregs (CD4+IL-10+). Overall, we noticed less reduction in clinical parameters of PD, poor bacterial clearance, higher inflammatory cells, and low immunosuppressive T cell abundance in geriatric PD subjects indicating age-associated immune profiles that can be used to non-invasively monitory therapy outcomes. Clinical relevance: difference in post-treatment improvements and bacterial clearance are linked to higher immune infiltrate for the geriatric group resulting in impaired resolution of the disease. Stronger responses of the pro- and anti-inflammatory cells of the young-middle aged group influenced the success of the therapy and wound healing.