IMMUNOHISTOLOGIC STUDY OF THE RUPTURED INTERVERTEBRAL DISC OF THE LUMBAR SPINE

Study Design. This study analyzed immunohistological features of the e xtruded or sequestrated intervertebral disc of the lumbar spine. To cl arify the pathogenesis of neovascularization, cells isolated from hern iated disc were cultured and examined biologically. Objectives. The ob jectives of this study were to characterize the histologic features of extruded or sequestrated discs and inflammatory cells that infiltrate along the margins of the disc tissue and to clarify the pathogenesis of neovascularization observed at the edge of the disc tissue. Summary of Background Data. When some of the contents of the disc extrudes in to the epidural space and is considered ''foreign,'' an autoimmune res ponse develops, which can lead to a chronic inflammatory response. How ever, the pathogenesis of inflammatory cell infiltrations and neovascu larization are not clearly defined. Methods. The herniated discs were obtained during surgery and were stained with anti-interleukin-1, inte rcellular adhesion molecule-1, lymphocyte function-associated antigen, and basic fibroblast growth factor antibodies by using an indirect im munoperoxidase method. Cells isolated from herniated disc were cocultu red with human endothelial cells and basic fibroblast growth factor co ntained by cultured disc cells were measured by radioimmunoassay. Resu lts. The ingrowth of granulation tissue with vascularization, occurrin g at the edge of fibrocartilage fragment, was present at 11 of 16 of e xtruded and 3 of 5 of sequestrated discs. Anti-interleukin-1, intracel lular adhesion molecule-1, lymphocyte function-associated antigen, and basic fibroblast growth factor were expressed on most of mononuclear cells infiltrating into the extruded or sequestrated disc. Cells from the extruded or sequestrated disc demonstrated significantly greater l evels of basic fibroblast growth factor than those from the protruded disc, and they enhanced the proliferation of endothelial cells. Conclu sions. This study showed that mononuclear cells infiltrating along the margins of extruded discs expressed inflammatory mediators and might induce neovascularization and persistence of inflammation.