Healing of laser-induced tympanic membrane perforations in rats: No contribution of granulocyte colony-stimulating factor or Gelfoam®

ObjectivesTo study whether granulocyte colony-stimulating factor together with Gelfoam® (absorbable gelatin sponge, USP) could enhance the healing of freshly perforated tympanic membranes. The frequency and occurrence of different immunocompetent cells and collagen types was noted.MethodsLaser perforations were made in the tympanic membrane of rats that were sacrificed at different time intervals post-myringotomy: Day 1, 3, 6, and 12. Tympanic membrane specimens were embedded and sections were stained with hematoxylin/eosin and an immunohistochemical technique was used, with antibodies against macrophages, B-cells, T-cells, and type I–IV collagens. Semi-quantification was performed after counting positive cells, mean values were calculated and analyzed statistically.ResultsAll perforations, except one, had closed by Day 12 and no difference was observed between experimental and control ears at the other time points. Gelfoam® was still present in a high amount at Day 12. The sections were initially stained positive for type I and II collagen, but after Day 6, the regenerating tissue stained positive for mainly type III and IV collagens. Results showed that the recruitment of macrophages, B-cells, and T-cells could not be mapped with a statistical significance.ConclusionsThis study showed that at 6–12 days post-laser myringotomy, type III and IV collagen has replaced the collagen type II that normally constitutes the healthy tympanic membrane. There is a concern for excessive scarring involving adjacent structures. It was also seen that the combination of Gelfoam® and granulocyte colony-stimulating factor or saline did not affect the healing times in perforated tympanic membranes. No significant results regarding the inflammatory cell recruitment could be obtained on the studied time points or between experimental and control ears, except for in the Gelfoam® matrix.