Study Design. Both sequestrated nucleus pulposus (SNP) and the remaining nucleus pulposus (RNP) were studied from the discs of the same patient to evaluate apoptosis using immunohistochemical staining.
Objective. To compare apoptosis of the SNP and the RNP in the disc of the same patient.
Summary of Background Data. Many studies have been conducted on the natural history and apoptosis of the herniated nucleus pulposus; however, apoptosis of the remaining nucleus cells, after removal of the sequestrated disc, in the same patient, has not been reported.
Materials and Methods. Eight samples of SNP and RNP from the disc of the same patient were obtained. The TUNEL stain was performed to confirm the occurrence of apoptosis in disc cells. Immunohistochemistry staining and Western blot analysis were performed to determine the presence of proteins, including caspase-3,-8,-9, and Bid.
Results. TUNEL-positive chondrocytes were identified in all of the SNP and RNP samples; the apoptotic index was 5.8 ± 1.9% and 5.9 ± 1.2%, respectively (P = 0.60). Caspase-3,-8,-9, and Bid were expressed in the SNP and the RNP of the cytoplasm and the nucleus by the immunohistochemical staining. The expression of active caspase-3,-8,-9, and Bid in the RNP of the disc and the SNP was different in each patient.
Conclusion. The frequency of chondrocyte apoptosis in the SNP and the RNP was not different in the disc. The pathways involved in chondrocyte apoptosis of the SNP and the RNP differed among individuals and included intrinsic and/or extrinsic pathways.