Regulation of wound healing by granulocyte-macrophage colony-stimulating factor after vocal fold injury

Abstract

Vocal fold (VF) scarring remains a therapeutic challenge. Granulocyte-macrophage colony-stimulating factor (GM-CSF) facilitates epithelial wound healing, and recently, growth factor therapy has been applied to promote tissue repair. This study was undertaken to investigate the effect of GM-CSF on VF wound healing in vivo and in vitro. VF scarring was induced in New Zealand white rabbits by direct injury. Either GM-CSF (treatment group) or PBS (control group) was injected into the VFs of rabbits immediately post-injury. Endoscopic, histopathological, immunohistochemical, and biomechanical evaluations of VFs were performed at 3 months post-injury. Human vocal fold fibroblasts (hVFFs) were cultured with GM-CSF. Productions of collagens type I and III were examined immunocytochemically and the syntheses of elastin and hyaluronic acids were evaluated by ELISA. The mRNA levels of genes related to ECM components and ECM production-related growth factors, such as HGF and TGF-ß1 were examined by real time RT-PCR.The GM-CSF-treated VFs showed reduced collagen deposition compared with the PBS-injected controls. Immunohistochemical staining revealed the amount of type I collagen and fibronectin was less in the GM-CSF-treated VFs (P = 0.0449 and P = 0.018, respectively). Viscous and elastic shear moduli of VF samples were significantly lower in the GM-CSF group than in the PBS-injected group (P < 0.0001 and P < 0.01, respectively). Mucosal waves in GM-CSF group showed significant improvement compared with the PBS group (P = 0.0446). GM-CSF inhibited TGF-β1-induced collagen synthesis by hVFFS (P < 0.05) and the production of hyaluronic acids increased at 72 hours post-treatment. The expressions of the mRNAs of HAS-2, tropoelastin, MMP-1, HGF, and c-Met were significantly increased by GM-CSF though at different time points (P < 0.05). The study shows that GM-CSF has therapeutic potential for the remodeling of VF wound and the promotion of VF regeneration.