Developing a Novel Treatment Method for Post-operative Middle Ear Regeneration Using Transplanted Nasal Muscosal Cells

Abstract

Typically, good mucosal regeneration will heal the ear adequately and lead to a successful operation. However, in most patients with cholesteatoma, the extent of the cyst or lesion is so severe that mucosal preservation is not easy. Recurrence of cholesteatoma and re-adhesion of the tympanic membrane often occurs leading to poor surgical results. "Regeneration of middle ear mucosa is necessary for good results after tympanoplasty," observes Kojima. "However, the challenge is that removing large amounts of mucosa, which tends to happen in surgery, impedes natural regeneration. A very thin layer of mucosa is left on the bone structure with a lack of connective tissue and poor blood supply." Thus far, there have been attempts to promote mucosal regeneration and rectify this challenge. Previous clinical studies for mucosal regeneration have included transplantation of middle ear mucosa and artificial materials such as collagen sponges, silicone sheets and gel films. However, the effectiveness of these methods has not been verified. Kojima and his team have discovered a viable solution. Their idea is to promote middle ear mucosal regeneration using the transplantation of cell sheets."?After coming to this conclusion, the next step in our process was to figure out which materials were suitable for creating these cell sheets," explains Kojima. "Using middle ear mucosa itself had been found to pose problems in clinical studies, so a different solution was needed." One issue with the use of middle ear mucosa was the need to open the middle ear surgically twice, as it is difficult to obtain a sufficient amount of raw material from the diseased ear. Therefore, the team sought answers through a different variety of mucosal tissue: nasal mucosa. "Not only does nasal mucosa belong to the same respiratory epithelium, or lining of cellular tissue, as does middle ear mucosa, but its location allows sufficient amounts of it to be easily harvested," Kojima says. Kojima began his investigation of the nasal mucosal cell sheet transplantation in rabbits. He experimented with one group of rabbits with their middle ear mucosa removed, one group with the cell sheet of nasal mucosa transplanted into their ears and a last control group. His findings were overwhelmingly positive. "Eight weeks after transplantation, the cell sheet transplanted group experienced good mastoid cavity aeration and suppressed bone hyperplasia whereas the mucosa-removed group had smaller mastoid cavities, extensive bone hyperplasia and granulation tissue formation which generally forms on the surface of a wound," notes Kojima. Their testing on rabbits suggested that their cell sheet has the potential to be useful as graft material for post-operative middle ear mucosal regeneration. Dr. Kojima - [e-mail]