REPAIR OF CHRONIC TYMPANIC MEMBRANE PERFORATIONS USING EPIDERMAL GROWTH FACTOR: PROGRESS TOWARD CLINICAL APPLICATION

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Abstract

ABSTRACT

In an earlier study, epidermal growth factor (EGF) was shown to be effective in healing chronic tympanic membrane (TM) perforations in the chinchilla. The original protocol required rimming of the perforation's epithelial edge, application of a paper patch, placement of a Gelfoam pledget, and then administration of EGF solution. To develop a simple outpatient method of healing chronic TM perforations, an attempt was made to simplify the treatment protocol while preserving efficacy. In the modified experimental protocol, a large Gelfoam pledget was placed over the chronic perforation in contact with the residual TM, without mechanical disruption of the perforation edge or use of a paper patch. Then EGF in phosphate buffered saline (PBS) was applied to the Gelfoam pledget (50 uL of 0.5 mg EGF/mL PBS). A series of control ears received Gelfoam pledgets and PBS. Complete closure of the TM perforation was achieved in 80 percent (12/15) of treated ears but in only 20 percent (3/15) of controls (p<0.01), results similar to those obtained with the original protocol. At long-term follow-up, 4 to 9 months after treatment, EGF-healed TMs were histologically similar to normal TMs, both in their overall thickness and in the relative proportions of the three component layers. In contrast, the few spontaneously healed TMs from the control group were less than half the thickness of normal TMs. To ascertain the optimal EGF concentration for therapeutic effect, a dose ranging study was undertaken. Concentrations at 50 percent and 25 percent of the original proved equally effective in inducing chronic TM perforations to heal. Finally, an ototoxic screening study revealed no significant cochleotoxic effects following topical application of EGF to the middle ear. Based upon these promising results in the animal model, clinical trials of EGF in the management of chronic TM perforations are being initiated.

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