Chemokine profile of herniated intervertebral discs infiltrated with monocytes and macrophages.

Study Design: Herniated lumbar disc specimens were analyzed using reverse transcriptase-polymerase chain reaction to determine the profile of chemokine expression.

Objective: To investigate the mechanism underlying the recruitment of inflammatory cells into herniated discs during the process of spontaneous regression.

Summary Of Background Data: Spontaneous regression of herniated intervertebral discs has been increasingly reported. Although macrophages are suggested to play a central role in this process, it remains unclear how these macrophages accumulate in the herniated discs.

Methods: RNA was extracted from 36 surgical specimens of the herniated lumbar disc, a disc specimen of idiopathic scoliosis and pyogenic spondylitis, and activated peripheral blood mononuclear cells of a normal donor. The RNA was reverse transcribed, and the resultant cDNA was amplified by PCR using primer pairs specific to the CXC chemokines (IL-8, MGSA-alpha, IP-10, MIG), the CC chemokines (MCP-1, MCP-2, MCP-3, MCP-4, MIP-1alpha, MIP-3alpha, RANTES, STCP-1), the C chemokine (lymphotactin), and the glyceraldehyde phosphate housekeeping gene. Thin cryostat sections also were made from the disc specimens and stained with hematoxylin and eosin.

Results: All the chemokines examined except MCP-4 were expressed by activated peripheral blood mononuclear cells. Glyceraldehyde phosphate was detected in 8 of 36 herniated discs and in 1 disc specimen each of idiopathic scoliosis and pyogenic spondylitis. Chemokine expression was examined for these 10 disc specimens. From among the 13 chemokines examined, MCP-3, MCP-4, RANTES, and IP-10 were detected in the disc from the idiopathic scoliosis, and MCP-3, MCP-4, RANTES, IP-10, MIG, and MGSA-alpha were detected in the infected or herniated discs. Histologic analysis showed infiltration of inflammatory cells in the infected disc and all 8 herniated discs.

Conclusions: The findings suggest that chemoattractive properties exist in a selected population of human intervertebral discs, and that unique sets of chemokinesplay a role in spontaneous regression of these herniated disc tissues.