Collagen Type II Is Produced in Healing Pars Tensa of Perforated Tympanic Membranes

Abstract

Type II collagen is synthesized in the tympanic membrane during healing of a perforation. The time course and appearance of Type II collagen regrowth in the newly healed tympanic membrane is the subject of the present study. The arrangement of Type II collagen fibers in the tympanic membrane gives it a unique tensile strength important for sound conduction. Healing after tympanic membrane perforation can cause the tympanic membrane to lose its characteristic. At what phase Type II collagen in tympanic membrane is replaced during healing of a perforation has previously not been studied. Rat tympanic membranes were perforated, and the animals were sacrificed 9 to 16 days after perforation. Tympanic membranes were stained with a Type II collagen antibody. At Day 9, a majority of the tympanic membranes had healed. Keratinizing epithelium and connective tissue had formed, but there was no Type II collagen. At Day 10, all tympanic membranes had healed, and staining for Type II collagen appeared. After Day 10, staining was more intense. Newly formed collagen did not show the parallel bundle arrangement seen in normal tympanic membranes but was more scattered in the tissue. Type II collagen was seen in tympanic membranes only after closure of the perforation. The fiber arrangement after healing was disturbed, which presumably has an impact on the function of the tympanic membrane. Understanding the formation of Type II collagen in the healing of tympanic membrane perforations could enable further research toward treating tympanic membrane perforations.