Both Th17-&-RANKL+Th-cells modulate severe periodontal bone loss in T1D

Background: Diabetes withholds a high-risk of developing severe-periodontitis and we have shown that diabetic non-obese-diabetic-(NOD)-mice, an analogue of type-1 diabetes (T1D), manifest more periodontal breakdown than non-diabetics-controls. IL17 is known to implicate arthritic bone loss; however, its role in periodontitis under T1D remains unclear. Objective: To study the mechanisms of T-cell-mediated immunity, IL17 & RANKL-RANK to enhancing periodontal breakdown in diabetic-NOD-mice orally infected with Aggregatibactor actinomycetemcomitans (Aa), a G(-)anaerobe responsible for aggressive-&-chronic periodontitis. Materials-&-Methods: Pre-diabetic (5-6-weeks-old), non-diabetic (14-16-weeks-old) and diabetic (>16-18 weeks-old)-NOD mice were orally inoculated with Aa (ATCC-29523) 2x/wk for 3-wks, and followed till 8-wks. Subsequently, molars were quantified for alveolar bone loss by histomorphometry and local CD4+Th-cells were purified for responses to Aa-stimulation in-vitro & measurement of RANKL-vs-IL17 expressions by flow-cytometry & real-time-PCR and cytokines in culture-supernatant by ELISA. Results: i) Aa-reactive CD4+T-cells from diabetic-mice exhibit significantly more proliferation and RANKL expressions than those from pre- & non-diabetic controls; ii) in-parallel, diabetic Th-cells have a 3.5-fold-increase in RANKL vs. a 3.4-fold-increase in IL17-mRNA expression, along with higher IL17 secretion, based on ELISA; iii) FACS-analyses show that Aa-reactive CD4+Th-cells from diabetic-mice manifest similar subsets of RANKL+IL17+Th(17)-cells, despite higher IL17 production. In conclusion: Microbes-reactive RANKL(+) diabetic CD4+Th(17)-cells do not express higher amount of IL17, whose contribution during the enhanced periodontal breakdown in T1D awaits determination and differ from those shown in arthritic bone loss. Ongoing study of RANKL and IL17/Th17-interactions are discussed to reveal the underlying mechanisms in T1D. Project supported by NIH-DE018356/-014473, USA & EX99-S34199N, NHRI, Taiwan.