Characterization of the Leukocyte Response in Acute Vocal Fold Injury

Macrophages location in the superficial layer of the vocal fold (VF) is not only at the first line of defense, but in a place of physiologic importance to voice quality. This study characterizes and compares macrophage function in two models of acute injury. Porcine VF injuries were created bilaterally by either surgical biopsy or lipopolysaccharide (LPS) (1.5 μg/kg) injection. Animals were sacrificed at 1- or 5-day post LPS or 3-, 7-, or 23-days post-surgical injury (n = 3/time/injury). Flow cytometry characterized immunophenotypes and RT-PCR quantified cytokine gene expression. Uninjured VF were used as controls. Post-surgical and LPS injury, SWC9+/SWC3- cells identified as hi SLA-DR+ (p<0.05) compared to controls along with hi CD16+ expression at 1-day and 3-days respectively compared to all other time points (p<0.05). Surgical injuries, SWC9+/SWC3- cells exhibited hi CD163+ (p<0.05) at 3-days along with upregulation in TNFα and TGFβ1 mRNA compared to 23-days (p<0.05). No measurable changes to IL-12, IFNγ, IL-10, IL-4 mRNA post-surgery. LPS injuries induced upregulation of TNFα, IL-12, IFNγ, IL-10, and IL-4 mRNA at 1- and 5-days compared to controls (p<0.05). Higher levels of IL-10 mRNA were found 1-day post-LPS compared to 5-days (p<0.05). No changes to CD163 or CD80/86 post-LPS were measured. Acute VF injuries revealed a paradigm of markers that appear to associate with each injury. LPS induced a regulatory phenotype indicated by prominent IL-10 mRNA expression. Surgical injury elicited a complex phenotype with early TNFα mRNA and CD163+ and persistent TGFβ1 transcript expression.