The expression of hypoxia inducible factor-1α and apoptosis in herniated discs

Study Design. Human intervertebral disc was obtained for the study of hypoxia inducible factor (HIF)-1 alpha and apoptosis using immunohistochemical staining. Objective. To study the expression of HIF-1 alpha and apoptosis in herniated lumbar discs. Summary of Background Data. The presence of HIF-1 alpha in human chondrocytes and rat intervertebral discs has been proven; however, to our knowledge, its expression in human intervertebral disc cells has not been reported. Apoptosis of the human intervertebral disc appears as a degenerative change caused by the aging of the intervertebral disc. To our knowledge, there is no reported study showing the correlation between apoptosis and HIF-1 alpha in the human intervertebral disc. Methods. There were 15 human intervertebral discs stained for HIF-1 alpha immunohistochemically, and apoptosis was detected using the terminal deoxynucleotidyl transferase mediated-dUTP nick end labeling method. On average, the patients were 32.9 years old. The intervertebral discs were divided into noncontained ( 9 patients) and contained ( 6) groups. For the control group, 5 disc samples were used. Results. The expression of HIF-1 alpha was visualized in every case, with an average of 62.2% +/- 9.5% in the noncontained group, 30.5% +/- 3.6% in the contained group, and 11.4% +/- 9.3% in the control group. Apoptosis occurred in 74.3% +/- 7.3% of the cells in the noncontained group, 42.8% +/- 5.5% of the cells in the contained group, and 28% +/- 8.4% of the cells in the control group. HIF-1 alpha and apoptosis expressions were both observed more frequently in the noncontained disc herniation group (P < 0.001). The correlation analysis between the degree of HIF-1 alpha expression and apoptosis was also statistically significant. Conclusions. HIF-1 alpha and apoptosis physiologically occur in human beings. Their expression was the highest in the noncontained group. HIF-1 alpha may play a crucial role for the survival of disc cells and resorption of the herniated disc in human intervertebral discs.