Expression of monocyte chemoattractant protein-1 in primary cultures of rabbit intervertebral disc cells

Macrophages are considered essential for herniated disc resorption, and chemokines may play a role in their recruitment. Here we demonstrate that intervertebral disc cells are capable of producing monocyte chemoattractant protein-1 (MCP-1), a CC chemokine that is chemotactic for macrophages. Nucleus pulposus cells and anulus fibrosus cells were harvested from intervertebral discs of healthy rabbits, and the cells were stimulated with either interleukin (IL)-1β or tumor necrosis factor (TNF)α. Reverse transcriptase polymerase chain reaction demonstrated that IL-1β and TNFα induced mRNA expression for MCP-1 in nucleus pulposus and anulus fibrosus cells. Protein concentrations of MCP-1 in the culture supernatants were quantitated by fluoroimmunoassay, which showed that nucleus pulposus and anulus fibrosus cells dose- and time-dependently produced MCP-1 after IL-β-and TNFα-stimulation, an event that was completely abrogated by IL-1 receptor antagonist and anti-TNFα monoclonal antibody, respectively. Nucleus pulposus cells produced significantly higher levels of MCP-1 than did anulus fibrosus cells. Immunohistochemically, the intensity of MCP-1 positive cells in nucleus pulposus cells was stronger than that in anulus fibrosus cells. Altogether, our data clearly demonstrated the production of MCP-1 in intervertebral disc cells, suggesting the possible involvement of disc cells in an early stage of macrophage infiltration.