Staphylococci planktonic and biofilm environments differentially affect osteoclast formation

Area of Science:

• Microbiology
• Immunology
• Orthopedics

Background:

• Chronic implant-related bone infections involve increased osteoclast activity and bone resorption.
• Bacterial biofilms contribute to infection chronicity by protecting bacteria and impairing immune cells.
• Macrophages, as osteoclast precursors, link inflammation and bone destruction.

Purpose of the Study:

• To investigate the impact of Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) biofilms on macrophage-mediated osteoclastogenesis.
• To analyze the effects of planktonic and biofilm bacterial environments on osteoclast formation using RAW 264.7 cells.

Main Methods:

• Utilized RAW 264.7 cells and conditioned media (CM) from planktonic and biofilm cultures of SA and SE.
• Investigated osteoclastogenesis by priming cells with RANKL and adding CM.
• Assessed the impact of simultaneous CM and RANKL stimulation on osteoclast formation.

Main Results:

• Priming with RANKL before CM addition promoted osteoclast differentiation, with the strongest effect from SE planktonic or SA biofilm CM.
• Simultaneous stimulation with CM and RANKL suppressed osteoclast formation.
• Formation of multinucleated giant cells (MGCs), associated with inflammation, was most pronounced with SE planktonic CM.

Conclusions:

• The biofilm environment, despite high lactate levels, does not actively promote osteoclastogenesis.
• Inflammatory immune responses to planktonic bacterial factors via Toll-like receptors are the primary drivers of pathological osteoclast formation.
• Immune stimulation or biofilm disruption strategies must consider the potential for enhanced inflammation-mediated bone destruction.