The role of inflammation in sciatica: the contradictory effect of macrophages

Abstract

Herniation of the lumbar disc can cause severe pain radiating down the leg alongside a dermatome. This pain can be caused by compression of the nerve root, but recent evidence has indicated that a local inflammation response may also play a role. This thesis focuses on how macrophages that infiltrate the herniated disc in patients with lumbar disc herniation, influence pain and recovery after discectomy. Our data shows that for most patients, if macrophages are present, they benefit the process of healing by leading to a quicker resorption of the herniated material which results in faster recovery. However, for patients with Modic changes, which indicates a degenerated endplate (structure between disc and vertebrae), the presence of macrophages is less beneficial, for they recover more slowly after surgery. The reason for this discrepency seems to be an altered differentiation profile in macrophages. Macrophages differentiate into different types with different behaviours: the M2 macrophages are known for its anti-inflammatory properties and tissue resorption. Our study found M2 macrophages in lower numbers in patients with degenerated endplates, which can explain their slower recovery. Together the data indicates that macrophage differentiation profiles in lumbar herniated discs are promising treatment targets.