Twenty four 4-month-old male Sprague Dawley rats were used in this study and assigned to chronic scar, bFGF treated, sham (saline) treated, and control groups. Eight rats underwent unilateral vocal fold stripping with laryngeal harvest 2 months post injury (chronic scar group). Four rats underwent unilateral vocal fold stripping, injection of bFGF 2 months post injury, and laryngeal harvest 4 months post injury (bFGF treated group). Six rats underwent unilateral vocal fold stripping, injection of saline 2 months post injury, and laryngeal harvest 4 months post injury (sham treated group). Six rats underwent no vocal fold stripping or injection (control group).
Vocal fold injuries were created as previously reported (Tateya et al., 2005 ). Rats underwent anesthesia induction with isoflurane (2–3% delivered at 0.8–1.5 L/min) followed by maintenance using an intraperitoneal (IP) injection of ketamine hydrochloride (90 mg/kg) and xylazine hydrochloride (9 mg/kg). Atropine sulfate (0.05 mg/kg) was also injected IP to reduce the secretion of saliva and sputum in the laryngeal lumen. The animals were placed on an operating platform in a near-vertical position and a custom fabricated 1 mm diameter steel wire laryngoscope was inserted to facilitate vocal fold visualization. Vocal fold monitoring was performed using a 1.9 mm diameter 25° endoscope (Richard Wolf, Vernon Hills, IL) connected to an external light source and video monitor. Injuries were created by vocal fold stripping using a 25 G needle and microforceps.
Vocal fold injections were performed using a 50 µL, 50 mm, 26-gauge needle, under endoscopic guidance as described above. bFGF (Sigma-Aldrich, St. Louis, MO) was injected at a concentration of 100 ng in 10 µL; a 100 ng dose was selected based on Hirano et al. (2005) . Normal saline (0.9% w/v NaCl) was injected in a volume of 10 µL.
Euthanasia was performed via intracardiac injection of Beuthanasia (0.22 mg/kg) (Schering-Plough Animal Health, Union, NJ). Larynges were harvested en bloc (Figure 1 ), quick frozen using liquid nitrogen, and stored at −80°C until use. Larynges from the chronic scar group intended for histological processing were embedded in optimal cutting temperature compound (Tissue-Tek, Sakura, Tokyo, Japan) prior to quick freezing.
Vocal fold injuries were created as previously reported (Tateya et al., 2005 ). Rats underwent anesthesia induction with isoflurane (2–3% delivered at 0.8–1.5 L/min) followed by maintenance using an intraperitoneal (IP) injection of ketamine hydrochloride (90 mg/kg) and xylazine hydrochloride (9 mg/kg). Atropine sulfate (0.05 mg/kg) was also injected IP to reduce the secretion of saliva and sputum in the laryngeal lumen. The animals were placed on an operating platform in a near-vertical position and a custom fabricated 1 mm diameter steel wire laryngoscope was inserted to facilitate vocal fold visualization. Vocal fold monitoring was performed using a 1.9 mm diameter 25° endoscope (Richard Wolf, Vernon Hills, IL) connected to an external light source and video monitor. Injuries were created by vocal fold stripping using a 25 G needle and microforceps.
Vocal fold injections were performed using a 50 µL, 50 mm, 26-gauge needle, under endoscopic guidance as described above. bFGF (Sigma-Aldrich, St. Louis, MO) was injected at a concentration of 100 ng in 10 µL; a 100 ng dose was selected based on Hirano et al. (2005) . Normal saline (0.9% w/v NaCl) was injected in a volume of 10 µL.
Euthanasia was performed via intracardiac injection of Beuthanasia (0.22 mg/kg) (Schering-Plough Animal Health, Union, NJ). Larynges were harvested en bloc (
