Targeting C1q prevents microglia-mediated synaptic removal in neuropathic pain

Area of Science:

• Neuroscience
• Immunology
• Pain Research

Background:

• Microglia activation in the spinal cord is key to neuropathic pain.
• Microglia's role in synaptic pruning during neuropathic pain is not fully understood.
• Immune and neurotrophic signaling by microglia are known factors in pain.

Purpose of the Study:

• To investigate the role of microglial phagocytosis and synaptic pruning in neuropathic pain.
• To determine the specific synaptic changes induced by peripheral nerve injury.
• To identify the molecular pathways involved in microglia-mediated synapse elimination.

Main Methods:

• Inducing peripheral nerve injury in mice.
• Analyzing synapse density in the dorsal horn.
• Utilizing complement-deficient mice (C3 and C4 knockout).
• Administering pharmacological inhibitors of complement protein C1q.

Main Results:

• Peripheral nerve injury leads to microglial engulfment of dorsal horn synapses.
• This process results in a preferential loss of inhibitory synapses, altering the inhibitory/excitatory balance.
• Synapse elimination is dependent on the complement pathway (C3 and C4).
• Inhibition of C1q prevents synapse loss and reduces neuropathic pain.

Conclusions:

• The complement pathway mediates microglia-driven synapse pruning in the spinal cord following nerve injury.
• This pruning, particularly of inhibitory synapses, contributes to persistent neuropathic pain.
• C1q represents a potential therapeutic target for managing neuropathic pain.