The Distribution And Significance Of SP Immunoreactive Nerve Fibers In Degenerated Lumbar Disc

The intervertebral disc is the largest avascular tissue in the body, and could also be one of the easiest and earliest degenerated tissues. Lumbar disc degeneration (LDD) is an irreversible pathological process and can cause discogenic low back pain, even Lumbar disc herniation (LDH). So far, all the efforts to treat lumbar disc degeneration is not satisfied and those methods such as the transplantation of nucleus pulposus cells,the injection of cytokine and the gene therapy are only used in animal experiment but not applied to clinical therapy. Now the therapies for lumbar disc degeneration have mainly been focused on discogenic low back pain or decompression of nerve, not on disc degeneration. So, it is very necessary to clarify the mechanism of lumbar disc degeneration for finding out an effective treatment of disc degeneration. SP (Substance P) has been accepted as a neuropeptide that transmits pain information and causes discogenic pain. Recently, many studies has demonstrated that SP can induce the production of several cytokines, for example, basic fibroblast growth factor(bFGF),interleukin-1(IL-1),Tumor necrosis factor (TNF), etc, which play a key role in lumbar disc degeneration. Very little is known about the occurrence and localization of Substance P in intervertebral disc tissue and degree of lumbar disc degeneration. ObjectiveTo investigate the occurrence and localization of Substance P in intervertebral disc tissue and explore its relationship with the degree of disc degeneration. This study may help us to furthermore understand the mechanism of lumbar disc degeneration and provide experimental evidence for the treatment of it in clinical.Materials and methodsTwenty-one surgical lumbar disc specimens were collected from sixteen patients undergoing lumbar discectomy and twelve normal human lumbar discs were obtained at autopsy. All the specimens were observed in the morphologic features and the presence of nerve fibers was investigated using substance P immunocytochemistry to qualify and quantitate it. All the data were analyzed with spss10.0 statistical software, p<0.05was considered the level of significance.ResultsDegenerated intervertebral disc has lost its normal architecture, and there are changes both in the nuclear and annular; the cells become more rounded, chondrocyte-like, often forming clusters, whereas in the normal condition annular cells are more spindle shaped; more extracellular matrix was observed. The innervation of SP immunoreactive nerve fibers were sporadically observed in the outermost layers of the anulus fibrosus of the normal discs but greatly in the inner anulus fibrosus of the degenerated discs, even in nucleus pulposus partly. There are statistical difference between control group and patient group; a significant positive correlation of SP immunoreactive nerve fibers and disc degeneration was found in patient group, but no positive correlation between age and SP immunoreactive nerve fibers, degree of disc degeneration.Conclusions1. The nerves, capillary infiltration and granulation tissue was found in the inner anulus fibrosus and nucleus pulposus of degenerated discs.2. SP was synthesized and released during lumbar disc degeneration.3. The correlation of SP immunoreactive nerve fibers and degree of disc degeneration was positive; substance P may be associated with further promotion of degenerative disarrangement.