Microglial cell response to experimental periodontal disease

Area of Science:

• Neuroimmunology
• Periodontal Medicine
• Alzheimer's Disease Research

Background:

• Microglial activation is crucial for managing neuroinflammation and the progression of neurodegenerative diseases like Alzheimer's disease (AD).
• Microglia play roles in forming barriers around amyloid plaques and phagocytosing beta-amyloid peptide (Aβ).
• The potential link between periodontal disease (PD) and neuroinflammation warrants investigation.

Purpose of the Study:

• To test the hypothesis that periodontal disease (PD) alters inflammatory activation and Aβ phagocytosis by microglial cells.
• To investigate the impact of PD-induced infection on microglial function in a mouse model.

Main Methods:

• Experimental PD was induced in C57BL/6 mice using ligatures, with assessments at 1, 10, 20, and 30 days.
• Bone loss and cytokine expression confirmed PD progression; microglial activation was analyzed via flow cytometry.
• Microglial cells were incubated with PD-associated bacteria or bacterial biofilm to measure inflammatory and phagocytic markers.

Main Results:

• Progressive PD and bone resorption were observed, correlating with increased frequency of activated microglia in the brain.
• PD-associated bacteria and Klebsiella variicola significantly increased pro-inflammatory cytokines (TNFα, IL-1β, IL-6) and TLRs (TLR2, TLR9) in microglia.
• Klebsiella variicola significantly enhanced Aβ-phagocytosis (394%) and MSR1 expression (33-fold) in microglial cells.

Conclusions:

• Inducing PD in mice leads to microglia activation in vivo.
• PD-associated bacteria directly induce a pro-inflammatory and phagocytic phenotype in microglia.
• These findings support a direct role for PD pathogens in driving neuroinflammation.