Abstract
ObjectiveThis retrospective observational histological study aims to associate the size and type of disc herniation with the degree of macrophage infiltration in disc material retrieved during disc surgery in patients with sciatica.MethodsDisc tissue of 119 sciatica patients was embedded in paraffin and stained with hematoxylin and CD68. Tissue samples were categorized as mild (0–10/cm2), moderate (10–100/cm2), and considerable (> 100/cm2) macrophage infiltration. All 119 patients received an MRI at baseline, and 108 received a follow-up MRI at 1-year. MRIs were reviewed for the size and type of the disc herniations, and for Modic changes in the vertebral endplates.ResultsBaseline characteristics and duration of symptoms before surgery were comparable in all macrophage infiltration groups. The degree of macrophage infiltration was not associated with herniation size at baseline, but significantly associated with reduction of size of the herniated disc at 1-year post surgery. Moreover, the degree of macrophage infiltration was higher in extrusion in comparison with bulging (protrusion) of the disc. Results were comparable in patients with and without Modic changes.ConclusionMacrophage infiltration was positively associated with an extruded type of disc herniation as well as the extent of reduction of the herniated disc during 1-year follow-up in patients with sciatica. This is an indication that the macrophages play an active role in reducing herniated discs. An extruded disc herniation has a larger surface for the macrophages to adhere to, which leads to more size reduction.
Highlights
Herniation of the intervertebral disc is a highly prevalent disease [11], characterized by radiating pain symptoms due to a compression of the nerve root by the herniated disc
This disruption of the annulus fibrosus can result in a foreign-body reaction aimed at the nucleus pulposus that induces neovascularization [13], which is accompanied by macrophage infiltration [15, 24, 26]
Macrophage infiltration may have a positive effect on symptoms through inducing a phagocytic resorption process, mediated by anti-inflammatory cytokines such as IL-4 and IL-10 [27, 29]
Summary
Herniation of the intervertebral disc is a highly prevalent disease [11], characterized by radiating pain symptoms due to a compression of the nerve root by the herniated disc. Since 1934, it has been widely accepted that a disc may herniate due to a disruption of the annulus fibrosus or due to its attachments to the adjacent endplate [16] This disruption of the annulus fibrosus can result in a foreign-body reaction aimed at the nucleus pulposus that induces neovascularization [13], which is accompanied by macrophage infiltration [15, 24, 26]. This macrophage infiltration is believed to exacerbate pain symptoms through secretion of pro-inflammatory cytokines such as IL-6, IL8, and TNF-alfa [1, 20, 29].
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