Interleukin-6 deficiency increases inflammatory bone destruction.

Area of Science:

• Oral Biology
• Immunology
• Bone Biology

Background:

• Periapical bone destruction is a common consequence of pulpal infection.
• Interleukin-1 (IL-1) has been identified as a primary stimulator of bone destruction in this context.
• Interleukin-6 (IL-6) is a cytokine induced during infections with complex roles.

Purpose of the Study:

• To investigate the role of IL-6 in regulating IL-1 expression and bone resorption during pulpal infection.
• To determine the in vivo effects of IL-6 deficiency on infection-induced periapical bone destruction.

Main Methods:

• Surgical pulp exposure and infection with a mixture of common pulpal pathogens in IL-6 knockout (IL-6(-/-)) and wild-type mice.
• Assessment of bone destruction and cytokine expression after 21 days.
• Evaluation of both chronic (IL-6(-/-)) and short-term (anti-IL-6 antibody neutralization) IL-6 deficiency models.

Main Results:

• Bone destruction was significantly increased (30%) in IL-6(-/-) mice compared to wild-type controls.
• Both chronic IL-6 deficiency and short-term IL-6 neutralization led to increased periapical bone resorption.
• Increased bone resorption correlated with higher osteoclast numbers and elevated IL-1alpha/IL-1beta expression, alongside decreased IL-10 expression.

Conclusions:

• Endogenous IL-6 expression exerts significant anti-inflammatory effects.
• IL-6 plays a critical role in modulating infection-stimulated periapical bone destruction in vivo.
• The absence of IL-6 exacerbates bone loss by increasing pro-inflammatory mediators and osteoclast activity.