Immunolocalization of bone morphogenetic protein and its receptors in degeneration of intervertebral disc

Study Design. Immunohistochemical study of expression and localization of bone morphogenetic protein (BMP)-2/4 and type I and II receptors on intervertebral disc. Objectives. To determine the biologic functions of BMPs and their receptors in the process of degeneration of the intervertebral disc. Summary of Background Data. Biologic and pathologic processes in the cell during the degeneration of the intervertebral disc are as yet poorly understood. Methods. The cervical spines of 15 male senescence-accelerated mice aged 8, 24, or 50 weeks were used for histologic and immunohistochemical examination of BMP-2/4 and BMP receptors IA, IB, and II. Immunostaining was performed with the avidin-biotin-peroxidase complex method. Results. Degenerative change was recognized within intervertebral discs of senescence-accelerated mice aged 50 weeks. BMP-2/4 and its receptors were abundant in hyaline cartilaginous cells within the endplate of the vertebrae at 8 and 24 weeks of age. However, the expression of BMP-2/4 and its receptors moved from the hyaline cartilage of the endplate of the vertebrae to fibrous cells within the anulus and to the calcified cartilage at the site of enthesis of mice aged 50 weeks. Conclusions. BMP-2/4 and its receptors may play roles in degenerative change of intervertebral disc.