OBJECTIVES/HYPOTHESIS: High-mobility group box 1 (HMGB1) protein has been identified as a principal instigator of injury-induced inflammation in many organ systems. Physiologically, HMGB1 binds to chromatin in cell nucleus. Upon injury, cells release HMGB1 to extracellular milieu, triggering a destructive inflammatory response. Neutralizing or removing HMGB1 has been shown to control inflammation. Unfortunately, the role of HMGB1 in laryngeal inflammation and healing has yet to be defined. The purpose of this study was to determine spatial and temporal patterns of HMGB1 expression in surgically injured rat vocal folds up to 2 weeks after injury. STUDY DESIGN: Prospective animal study. METHODS: Bilateral vocal fold injury was performed on 70 Sprague-Dawley rats. An additional 14 rats served as uninjured controls. Animals were sacrificed at 1 day, 3 days, 5 days, 1 week, and 2 weeks following surgery. Immunohistochemistry staining and enzyme-linked immunosorbent assay (ELISA) were performed to determine the spatial distribution and temporal expression, respectively, of HMGB1 in vocal fold tissue. Hematoxylin-and-eosin staining for cell counting was performed to evaluate cell infiltration. RESULTS: Cell number peaked significantly 5 days after injury. HMGB1 was positively stained in the nuclear, cytoplasmic, and extracellular compartments from days 1 to 7 after injury, whereas a strict nuclear staining was observed in uninjured controls and week 2 animals. Staining results were corroborated by ELISA. CONCLUSIONS: Spatial and temporal changes of HMGB1 expression were shown in injured vocal fold tissue, indicating this protein may be one of the principal drivers of inflammation and healing response to surgical injury in the larynx.
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