M2 macrophages-derived exosomes regulate osteoclast differentiation by the CSF2/TNF-α axis

Area of Science:

• Cell Biology
• Immunology
• Biochemistry

Background:

• Osteoclast activity drives bone loss in various skeletal diseases.
• Exosomes are recognized for their role in regulating osteoclast differentiation.
• M2-polarized macrophages possess anti-inflammatory properties.

Purpose of the Study:

• To investigate the impact of M2 macrophage-derived exosomes (M2-exos) on osteoclastogenesis.
• To elucidate the molecular mechanisms underlying M2-exos' effects on osteoclasts.

Main Methods:

• M2-exos were isolated from IL-4-induced Raw264.7 cells (M2 macrophages).
• Osteoclast differentiation was assessed using tartrate-resistant acid phosphatase staining.
• Gene expression (qPCR) and protein levels (Western blotting) were analyzed to determine molecular mechanisms.

Main Results:

• M2-exos significantly suppressed receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation.
• CSF2 expression was elevated in M2 macrophages; its knockdown amplified M2-exos' inhibitory effects.
• CSF2 positively regulated TNF-α signaling; inhibiting TNF-α promoted osteoclast differentiation in M2-exo-treated cells.

Conclusions:

• M2-exos inhibit RANKL-induced osteoclast differentiation by downregulating CSF2 and inactivating TNF-α signaling.
• These findings highlight the therapeutic potential of M2-exos for bone diseases characterized by excessive bone resorption.