The effect of acidic fibroblast growth factor and live yeast cell derivative on tympanic membrane regeneration in a rat model

Induction of growth factor expression is reduced during healing of tympanic membrane perforations in glucocorticoid-treated rats

The participation of growth factors in wound healing of tympanic membranes (TMs) is established. To determine the possible role of these growth factors in normal healing, we examined the regulation of keratinocyte growth factor (KGF), transforming growth factor-alpha (TGF-alpha), and basic fibroblast growth factor (bFGF) messenger RNA (mRNA) expression in wounded TMs of glucocorticoid-treated rats; these rats have severe wound healing abnormalities. Induction of KGF, TGF-alpha, and bFGF mRNA expression after TM injury was significantly reduced in these rats. Moreover, we found that the average number of bromodeoxyuridine-positive cells in a glucocorticoid-treated group was significantly lower than that in controls. The data suggest that reduced expression of these genes might be partially responsible for the wound healing defects seen in these animals. These results provide a possible explanation for the beneficial effect of exogenous KGF, TGF-alpha, or bFGF in treatment of wound healing disorders of the TM.

Creating a stable tympanic membrane perforation using mitomycin C

OBJECTIVE

To determine the ability of topically applied mitomycin C to create a stable tympanic membrane perforation.

STUDY DESIGN AND SETTING

Twenty-four rats underwent subtotal removal of the tympanic membranes bilaterally. Forty ears received 0.2 mg/ml of mitomycin C. The remaining 8 received phosphate-buffered saline solution (control). Photographs taken every 3 to 5 days for 44 days were digitally scanned and computer analyzed to calculate the percentage of residual perforation. Application of solutions, photography, and data analysis were performed in a blinded fashion.

RESULTS

The mitomycin C treated ears had delayed closure time and healing rate (from day 0 to 25) compared to the control group. All controls healed by day 14. By day 44, 92.5% of the mitomycin C treated ears healed.

CONCLUSION

Mitomycin C prolongs the closure and healing rate of myringotomies in rat tympanic membranes.

SIGNIFICANCE

Myringotomy with concurrent mitomycin C application may be useful for creating an animal model for chronic tympanic membrane perforation and should be tested in human beings as a method to maintain myringotomy patency for long-term ventilation.