Ultrastructural Analysis on Lumbar Disc Herniation Using Surgical Specimens : Role of Neovascularization and Macrophages in Hernias

The mechanisms responsible for the spontaneous regression of lumbar disc herniation (LDH) were studied by examining herniated tissue collected at operation from patients with LDH. The aim of the present study was to investigate the role of neovascularization and macrophages in hernias when spontaneous regression of LDH occurred. Spontaneous regression of LDHs has already been demonstrated by diagnostic imaging with tools such as magnetic resonance imaging. However, there have been few studies on the mechanisms of spontaneous regression based on pathologic examination of herniated tissue. In particular, there has been no detailed work on the role of macrophages, which are thought to be closely associated with spontaneous regression. The magnetic resonance imaging and operative findings of 73 patients who underwent surgery were investigated, and specimens collected during surgery were examined by light and transmission electron microscopy. Capillaries that invade the hernia and macrophages derived from monocytes migrating out of these capillaries are considered to be important factors in the regression of the herniated disc. Macrophages contain lysosomes filled with collagen-degrading enzymes that break down substances after phagocytosis, whereas primary lysosomes are secreted by these cells and break down intercellular substances such as collagen. Both of these mechanisms are closely involved in the regression of herniation. The inflammatory response that occurs around hernia tissue in the epidural space is believed to play an important role in herniated disc resorption, although it may also have a harmful effect on the adjacent nerve root. Therefore, control of the inflammatory reaction is an important challenge when treating patients with disc herniation.