Growth Factors Influence Growth and Differentiation of the Middle Ear Mucosa

Autologous human nasal epithelial cell sheet using temperature-responsive culture insert for transplantation after middle ear surgery

Postoperative mucosal regeneration of the middle ear cavity and the mastoid cavity is of great importance after middle ear surgery. However, the epithelialization of the mucosa in the middle ear is retarded because chronic inflammation without epithelialization aggravates gas exchange and clinical function. These environmental conditions in the middle ear lead to postoperative retraction and adhesion of the newly-formed tympanic membrane. Therefore, if the mucosa on the exposed middle ear bone surface can be rapidly regenerated after surgery, the surgical treatments for cholesteatoma and adhesive middle ear disease can potentially be improved. In this study, we successfully generated a cell sheet designed for the postoperative treatment of cholesteatoma. We used nasal cells to create an artificial middle ear mucosal cell sheet with a three-dimensional (3D) configuration similar to that of the middle ear mucosa. The sheets consisted of multi-layered mucosal epithelia and lower connective tissue and were similar to normal middle ear mucosa. This result indicates that tissue-engineered mucosal cell sheets would be useful to minimize complications after surgical operations in the middle ear and future clinical applications are expected. Copyright © 2015 John Wiley & Sons, Ltd.

A mouse model of otitis media identifies HB-EGF as a mediator of inflammation-induced mucosal proliferation

Objective

Otitis media is one of the most common pediatric infections. While it is usually treated without difficulty, up to 20% of children may progress to long-term complications that include hearing loss, impaired speech and language development, academic underachievement, and irreversible disease. Hyperplasia of middle ear mucosa contributes to the sequelae of acute otitis media and is of important clinical significance. Understanding the role of growth factors in the mediation of mucosal hyperplasia could lead to the development of new therapeutic interventions for this disease and its sequelae.

Methods

From a whole genome gene array analysis of mRNA expression during acute otitis media, we identified growth factors with expression kinetics temporally related to hyperplasia. We then tested these factors for their ability to stimulate mucosal epithelial growth in vitro, and determined protein levels and histological distribution in vivo for active factors.

Results

From the gene array, we identified seven candidate growth factors with upregulation of mRNA expression kinetics related to mucosal hyperplasia. Of the seven, only HB-EGF (heparin-binding-epidermal growth factor) induced significant mucosal epithelial hyperplasia in vitro. Subsequent quantification of HB-EGF protein expression in vivo via Western blot analysis confirmed that the protein is highly expressed from 6 hours to 24 hours after bacterial inoculation, while immunohistochemistry revealed production by middle ear epithelial cells and infiltrating lymphocytes.

Conclusion

Our data suggest an active role for HB-EGF in the hyperplasia of the middle ear mucosal epithelium during otitis media. These results imply that therapies targeting HB-EGF could ameliorate mucosal growth during otitis media, and thereby reduce detrimental sequelae of this childhood disease.

[Clinical and roentgenological diagnostics of the severity of mucositis in the patients presenting with chronic suppurative otitis media]

The objective of the present study was to determine the prevalence of mucositis and its roentgenological manifestations in the patients presenting with chronic suppurative otitis media (CSOM). A total of 390 patients with CSOM (mesotympanitis) and 85 ones suffering CSOM with concomitant mucositis were available for the observation. The signs of mucositis were evaluated based on the patients' complaints, results of otomicroscopy, and computed tomography (CT) of the temporal bones. This randomized clinical study involving 390 patients presenting with CSOM revealed the signs of mucositis in 44.6% of the cases. Analysis of the results of temporal bone CT performed in 85 patients with CSOM and mucositis in the absence exacerbation has demonstrated the possibility of detecting mucositis and evaluating its severity from the changes in the airness of the tympanic cavity, attics, and antrum due to the presence of the pathological substrate in these regions.

In vitro reconstruction of a three-dimensional middle ear mucosal organ and its in vivo transplantation

CONCLUSIONS

These experimental findings suggest the feasibility of artificial middle ear mucosa grafting as an effective treatment for achieving mucosal regeneration after middle ear surgery.

OBJECTIVES

Postoperative mucosal regeneration of tympanic cavity and mastoid cavity is of great importance after middle ear surgery. We reconstructed in vitro a three-dimensional middle ear mucosal organ, and assessed its feasibility for regenerative medicine of middle ear-related diseases.

MATERIALS AND METHODS

Epithelial cells and fibroblasts were isolated from the middle ear mucosa of rats and propagated by subculturing. An artificial middle ear mucosal organ was reconstructed by overlaying the middle ear epithelial cells on three-dimensional lattices of a collagen gel that had been repopulated with the fibroblasts. In addition, the artificial organ was implanted in the middle ear cavity of rats.

RESULTS

The artificial middle ear mucosa consisted of the single layer of epithelial cells, the basal membrane, and the underlying connective tissue. Electron microscopy revealed the presence of tight junctions and adherence junctions on the apical side, and adhesion complexes made of desmosomes. The reconstituted mucosa expressed genes of mucin, strongly suggesting that the artificial middle ear mucosa was capable of secreting mucus proteins. The DiI-labeled artificial middle ear mucosa implanted into the middle ear cavity was well engrafted and associated with host tissues.

Epidermal Growth Factor Expression in Middle Ear Cholesteatoma

Middle ear cholesteatoma is destructive to auditory ossicles and temporal bone, and treatment usually requires surgical removal of all epithelial content. Epidermal growth factor (EGF) can stimulate the growth and differentiation of a variety of mammalian cells, including epithelial cells. Our study used the avidin-biotin complex technique to evaluate the expression of EGF in 40 cases of middle ear cholesteatoma (active cholesteatoma, 31 cases; inactive cholesteatoma, 9 cases) and 34 normal postauricular skin samples. In middle ear cholesteatoma, EGF was expressed in squamous epithelium in 21 cases (53%), fibroblasts in two cases (5%), and cholesteatoma endothelium in two cases (5%). In normal postauricular skin, EGF was expressed in squamous epithelium in 14 samples (41%), fibroblasts in one sample (3%), and endothelium in none. No statistical difference in EGF expression was found between cholesteatoma and normal postauricular skin samples. These results show that the distribution of EGF in middle ear cholesteatoma is not deranged and that the progression of cholesteatoma might be induced by the release of factors from the cholesteatoma matrix via autocrine stimulation, or by inflammatory cells of the subepithelial tissue through paracrine stimulation, or in both of these ways.

Effect of growth factors on hyaluronan production by canine vocal fold fibroblasts

Hyaluronan (HYA) is considered to be a crucial factor in scarless wound healing and in maintaining tissue viscosity of the vocal fold lamina propria. In this study focusing on the effects of growth factors, we examined how HYA is produced and controlled in canine cultured vocal fold fibroblasts. Fibroblasts were taken from the lamina propria of the vocal folds of 8 dogs and cultured with and without growth factors. The production of HYA in the supernatant culture was quantitatively examined by enzyme-linked immunosorbent assay. Hepatocyte growth factor, epidermal growth factor, basic fibroblast growth factor, and transforming growth factor beta1 all stimulated HYA synthesis from vocal fold fibroblasts. These effects differed with the concentration of growth factors and the incubation period. We also examined how frequently the growth factors had to be administered in order to maintain appropriate levels of HYA. A single administration was sufficient to maintain appropriate HYA levels for at least 7 days. The present studies have demonstrated positive effects of growth factors in stimulating HYA production. Further in vivo study is needed to clarify the usefulness of these growth factors in the management of vocal fold scarring.

Hepatocyte growth factor and its receptor c-met in rat and rabbit vocal folds

Vocal fold fibrotic scar is characterized by fibrosis of the lamina propria and epithelium, and is difficult to treat. Hepatocyte growth factor (HGF) has antifibrotic activity and has received attention as a possible therapeutic alternative to treat fibrosis. In this study, in order to clarify whether HGF can be involved in vocal fold scarring, we examined the existence of HGF and its receptor, c-Met, in rat vocal folds, and then the activity of HGF in rabbit injured vocal folds, using immunohistochemistry and enzyme-linked immunosorbent assay. We found HGF and c-Met on epithelial cells and gland cells of the rat vocal folds. On the injured vocal folds of rabbits, little HGF was observed immediately after injury, but prominent activity occurred simultaneously with reepithelialization of the vocal fold mucosa on days 10 to 15. The activity of HGF was observed on fibroblasts in the lamina propria, as well as the epithelium. It is suggested that HGF in the vocal folds is produced by the fibroblasts and delivered to the epithelium. The implication of these findings is that HGF is involved in wound healing of the vocal fold, and may provide an alternative approach in preventing and treating vocal fold scarring.

Growth factors and their receptors in the middle ear mucosa during otitis media

OBJECTIVE

The hyperplastic response of the middle ear mucosa during bacterial otitis media is thought to be mediated by the actions of growth factors and their respective receptors. The purpose of the study was to explore the expression of growth factors known to stimulate epithelial cells in other systems, as well as their receptors, in the middle ear mucosa during otitis media.

STUDY DESIGN

Expression of mRNA growth factors and receptors was measured over time after inoculation of the rat middle ear with bacteria.

METHODS

The middle ears of 12 male Sprague-Dawley rats were injected with 10(5)/mL Haemophilus influenzae strain 3655 (nontypeable, biotype II). Three rats were killed at 6, 24, 48, and 72 hours. Three untreated rats were also killed to serve as negative controls. The middle ear mucosa samples were surgically removed and homogenized. Reverse transcription-polymerase chain reaction was performed on each sample with primers for rat epidermal growth factor, epidermal growth factor receptor (ErbB), heparin binding epidermal-like growth factor, hepatocyte growth factor, hepatocyte growth factor receptor, keratinocyte growth factor, betacellulin, amphiregulin, and neuregulin-alpha.

RESULTS

Hepatocyte growth factor and epidermal growth factor receptor primers demonstrated polymerase chain reaction products of the expected size that were not displayed in the normal middle ear mucosa. Keratinocyte growth factor and hepatocyte growth factor receptor demonstrated polymerase chain reaction products at all time points tested. Betacellulin and neuregulin-alpha products were present at all time points except 72 hours after infection.

CONCLUSIONS

The results of the study support a role for growth factors in the middle ear mucosa during otitis media. These bioactive ingredients contribute to mucosal hyperplasia.