Herniated and spondylotic intervertebral discs of the human cervical spine: Histological and immunohistochemical observations

We investigated the histological and immunohistochemical changes within and around the cervical intervertebral discs in symptomatic myeloradiculopathy and myelopathy patients. A total of 163 cervical intervertebral discs, 100 herniated discs and 63 spondylotic discs, were harvested en bloc during anterior decompressive surgeries and histological examination was performed, focusing on nucleus pulposus, annulus fibrosus, cartilaginous endplate, and ligamentous enthesis. There was a close relationship between MRI grade and histological degenerative changes. Histological features of the herniated intervertebral discs were the presence of granulation tissue, newly-developed blood vessels and infiltration of CD68-positive cells, which surrounded the herniated tissue in the outer layer of the annulus fibrosus. Marked vascular invasion was detected in 67% of herniated discs and 54% of spondylotic discs. lmmunohistochemically, chondrocytes positive for matrix metalloproteinase (MMP)-3, tumor necrosis factor (TNF)-alpha, basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) were detected in both herniated and spondylotic discs. Our results indicate that the neoangiogenesis process is associated with overexpression of bFGF and VEGF, and suggest that intervertebral disc degradation is enhanced by macrophage infiltration, which is regulated by MMP-3 and TNF-alpha. The expression of these proteins may be enhanced by the tear of annulus fibrosus.