Spiral ligament fibrocytes release chemokines in response to otitis media pathogens

Spiral ligament fibrocytes (SLFs) may be involved in the innate immune response of the inner ear by producing chemoattractants for recruiting inflammatory cells such as neutrophils and monocytes.

The purpose of this study was to investigate the cellular responses of SLFs when challenged by inflammatory stimuli such as components of otitis media pathogens or proinflammatory cytokines.

To detect released inflammatory cytokines and chemokines, cells were treated for 48 h with whole lysates of nontypable Haemophilus influenzae (NTHi), Streptococcus pneumoniae, or with interleukin 1 alpha (IL-1alpha). The culture medium was then collected and applied to protein arrays. To compare mRNA levels of chemokines, total RNA was extracted after 3 h of treatment with the above agents, and quantitative real-time PCR was performed.

Protein array analysis showed that in response to NTHi or S. pneumoniae, rat SLFs released monocyte chemotactic protein 1, macrophage inflammatory protein 3 alpha, TNF-alpha, and cytokine-induced neutrophil chemoattractant 2 and 3. Treatment with IL-1alpha, on the other hand, resulted in release of MCP-1 but not the other molecules. Tissue inhibitor of metalloproteinase 1 and vascular endothelial growth factor were released regardless of the inflammatory stimulus used.