Effect of 5-fluorouracil in cholesteatoma development in an animal model

The Science of Cholesteatoma

Cholesteatoma is a potential end-stage outcome of chronic ear infections that can result in the destruction of temporal bone structures with potential resultant hearing loss, vertigo, and intracranial infectious complications. There is currently no treatment apart from surgery for this condition, and despite years of study, the histopathogenesis of this disease remains poorly understood. This review is intended to summarize our accumulated knowledge of the mechanisms of cholesteatoma development and the underlying molecular biology. Attention will be directed particularly to recent developments, covering many potential pharmacologic targets that could be used to treat this disease in the future.

Review of potential medical treatments for middle ear cholesteatoma

Middle ear cholesteatoma (MEC), is a destructive, and locally invasive lesion in the middle ear driven by inflammation with an annual incidence of 10 per 100,000. Surgical extraction/excision remains the only treatment strategy available and recurrence is high (up to 40%), therefore developing the first pharmaceutical treatments for MEC is desperately required. This review was targeted at connecting the dysregulated inflammatory network of MEC to pathogenesis and identification of pharmaceutical targets. We summarized the numerous basic research endeavors undertaken over the last 30+ years to identify the key targets in the dysregulated inflammatory pathways and judged the level of evidence for a given target if it was generated by in vitro, in vivo or clinical experiments. MEC pathogenesis was found to be connected to cytokines characteristic for Th1, Th17 and M1 cells. In addition, we found that the inflammation created damage associated molecular patterns (DAMPs), which further promoted inflammation. Similar positive feedback loops have already been described for other Th1/Th17 driven inflammatory diseases (arthritis, Crohn’s disease or multiple sclerosis). A wide-ranging search for molecular targeted therapies (MTT) led to the discovery of over a hundred clinically approved drugs already applied in precision medicine. Based on exclusion criteria designed to enable fast translation as well as efficacy, we condensed the numerous MTTs down to 13 top drugs. The review should serve as groundwork for the primary goal, which is to provide potential pharmaceutical therapies to MEC patients for the first time in history.

Inhibitory effect of mesna and 5-fluorouracil on propylene glycol-induced cholesteatoma in rats

Objective

The aim of this study was to investigate the inhibitory effect of different doses of sodium-2-mercaptoethanesulphonate (MESNA) and 5-fluorouracil on cholesteatoma formation.

Methods

Fifty-six Wistar albino male rats were divided into seven groups with eight rats in each. On the first, eighth and fifteenth days, 0.2 ml of saline was administered to the group 1 (control group), and propylene glycol to induce cholesteatoma the other groups. On the 22^nd day of the study, 0.2 ml saline was given to Group 1 and Group 2. Groups 3 to 7 were treated with 0.2 ml 100% MESNA, 0.2 ml 50% MESNA, 0.2 ml 20% MESNA, 0.2 ml 5-fluorouracil and 0.1 ml 100% MESNA plus 0.1 ml 5-fluorouracil, respectively, with all applications performed by intratympanic injection.

Results

Significant differences were found between Group 1 and all other groups except Group 3. Significant differences were also found between Group 3 and Groups 2, 5 and 6 (P < 0.05).

Conclusions

According to the results of this study, experimental cholesteatoma induced with propylene glycol may be inhibited by MESNA at 100% concentration.

The Effect of Oral Montelukast Administration in Cholesteatoma Development and Inflammation: An Experimental Animal Model

HYPOTHESIS

We hypothesized that oral montelukast treatment could inhibit cholesteatoma formation in an experimental animal model.

BACKGROUND

Inflammation and excessive proliferation have been described in the histopathology of cholesteatoma. The aim of this study was to determine the effect of oral montelukast on cholesteatoma development.

METHODS

Eighteen healthy female Wistar albino rats weighing 250 g were chosen for the study. The animals were divided into two groups: group 1 received montelukast and group 2 was the control group. Intratympanic propylene glycol injection was administered into the left ears and physiologic serum was instilled into the right ears of the animals on the first, eighth, and fifteenth days. The effects of montelukast administration were evaluated by histological examination of the tympanic membrane and middle ear.

RESULTS

Group 1 (montelukast group) showed significant differences in terms of cholesteatoma formation, granulation, epithelial invagination, and inflammation. Cholesteatoma formation in the left ear was observed in 2 (22%) and 8 (89%) rats in groups 1 and 2, respectively (p = 0.015).

CONCLUSION

Development of cholesteatoma and inflammation was significantly lower in the montelukast-administered group. Thus, oral montelukast was found effective in preventing cholesteatoma formation.

Chronic inflammation of middle ear cholesteatoma promotes its recurrence via a paracrine mechanism

Background

Cholesteatoma disease is an expanding lesion in the middle ear. Hearing loss and facial paralysis alongside with other intracranial complications are found. No pharmaceutical treatment is available today and recurrence after surgical extraction occurs. We investigated possible TLR4-based mechanisms promoting recurrence and explore possible treatments strategies.

Methods

We isolated fibroblasts and epidermal stem cells from cholesteatoma tissue and healthy auditory canal skin. Subsequently, their expression under standard culture conditions and after stimulation with LPS was investigated by RT-qPCR. Cell metabolism and proliferation were analysed upon LPS treatment, with and without TLR4 antagonist. An indirect co-culture of fibroblasts and epidermal stem cells isolated from cholesteatoma tissue was utilized to monitor epidermal differentiation upon LPS treatment by RT-qPCR and immunocytochemistry.

Results

Under standard culture conditions, we detected a tissue-independent higher expression of IL-1β and IL-8 in stem cells, an upregulation of KGF and IGF-2 in both cell types derived from cholesteatoma and higher expression of TLR4 in stem cells derived from cholesteatoma tissue. Upon LPS challenge, we could detect a significantly higher expression of IL-1α, IL-1β, IL-6 and IL-8 in stem cells and of TNF-a, GM-CSF and CXCL-5 in stem cells and fibroblasts derived from cholesteatoma. The expression of the growth factors KGF, EGF, EREG, IGF-2 and HGF was significantly higher in fibroblasts, particularly when derived from cholesteatoma. Upon treatment with LPS the metabolism was elevated in stem cells and fibroblasts, proliferation was only enhanced in fibroblasts derived from cholesteatoma. This could be reversed by the treatment with a TLR4 antagonist. The cholesteatoma fibroblasts could be triggered by LPS to promote the epidermal differentiation of the stem cells, while no LPS treatment or LPS treatment without the presence of fibroblasts did not result in such a differentiation.

Conclusion

We propose that cholesteatoma recurrence is based on TLR4 signalling imprinted in the cholesteatoma cells. It induces excessive inflammation of stem cells and fibroblasts, proliferation of perimatrix fibroblasts and the generation of epidermal cells from stem cells thru paracrine signalling by fibroblasts. Treatment of the operation site with a TLR4 antagonist might reduce the chance of cholesteatoma recurrence.

Video Abstract

Single dose intratympanic mesna application inhibits propylene glycol induced cholesteatoma formation

Objective:

Mesna (i.e. sodium 2-mercaptoethanesulfonate; C2H5NaO3S2) has been used in otological surgery such as cholesteatoma dissection and tympanic membrane lateralisation in atelectatic ears. However, this study aimed to investigate its effect on cholesteatoma formation.

Methods:

A total of 20 Wistar rats were divided into two groups of 10 animals. The right and left ears of control animals were treated with saline (saline control group; n = 10 ears) and propylene glycol plus saline (propylene glycol control group; n = 10 ears), respectively. In the mesna group, both ears were treated with propylene glycol plus mesna (n = 20 ears). On days 1, 8 and 15, the saline control group had intratympanic injections of 0.2 ml saline and the propylene glycol control and mesna groups had intratympanic injections of 0.2 ml 100 per cent propylene glycol. On day 22, the propylene glycol control group had a single intratympanic injection of 0.2 ml saline and the mesna group had a single intratympanic injection of 10 per cent mesna. Animals were killed 12 weeks after the last injection and the temporal bones were sent for histopathological evaluation.

Results:

The cholesteatoma formation rate was 88 per cent in the propylene glycol control group, but was significantly lower in the mesna group (p = 0.01). There were no significant differences in granulation tissue formation (p = 0.498), cyst formation in the bulla (p = 0.381), fibrosis (p = 0.072) and epithelial hyperplasia (p = 0.081) among experimental groups.

Conclusion:

Intratympanic propylene glycol administration is an effective method of promoting experimental cholesteatoma formation. Administration of a single dose of intratympanic mesna inhibited cholesteatoma formation in an animal model.

Does Topical Application of 5-Fluorouracil Ointment Influence Inner Ear Function?

OBJECTIVE: To investigate the effect of 5-fluorouracil (5-FU) ointment on the inner ear of guinea pigs.

STUDY DESIGN AND SETTING: In group A (n = 7), 5-FU ointment was applied into the left external auditory canal. In group B (n = 10), 5-FU ointment was applied to the left middle ear through myringotomy. In both groups, the right ear served as a control. One week later the endocochlear DC potential (EP) was measured and morphology of the cochleae was examined using scanning electron microscopy (SEM) and light microscopy.

RESULTS: In group A, there was no significant difference between the EP values of the experimental side and the control side. In group B, there was a statistically significant difference between them ( P < 0.05). Morphologic findings showed no damage.

CONCLUSION: 5-FU ointment application to the external ear seems to be safe but its application to the middle ear may pose some risk of ototoxicity.

Effect of intratympanic mitomycin C on the development of cholesteatoma and otitis media in rats

Objective:

To determine whether the administration of mitomycin C prevents propylene glycol exposure from inducing middle-ear cholesteatoma and otitis media, in a rat model.

Methods:

Twenty-four Wistar rats underwent intratympanic injections on days 1, 8 and 15, via the tympanic membrane pars tensa, in both the right and left ears. The right ear injection solution contained 50 per cent propylene glycol, gentamicin and saline (0.9 per cent), while the left ear solution contained 50 per cent propylene glycol, gentamicin and mitomycin C. Animals were sacrificed and examined.

Results:

There were statistically significant differences between the control and experimental groups for tympanic bulla mucosal thickness (p = 0.004) but not for tympanic membrane thickness (p = 0.371), otomicroscopic findings (p = 0.262), or the presence of exudate (p = 0.125), fibrosis (p = 1.000) or cholesteatoma (p = 0.687).

Conclusion:

Intratympanic mitomycin C was ineffective in preventing middle-ear cholesteatoma and otitis media in this rat model.

Animal models of middle ear cholesteatoma

Middle ear acquired cholesteatoma is a pathological condition associated with otitis media, which may be associated with temporal bone resorption, otorrhea and hearing loss, and occasionally various other complications. Cholesteatoma is characterized by the enhanced proliferation of epithelial cells with aberrant morphologic characteristics. Unfortunately, our understanding of the mechanism underlying its pathogenesis is limited. To investigate its pathogenesis, different animal models have been used. This paper provides a brief overview of the current status of research in the field of pathogenesis of middle ear acquired cholesteatoma, four types of animal models previously reported on, up-to-date cholesteatoma research using these animal models, our current studies of the local hybrid ear model, and the future prospect of new animal models of middle ear cholesteatoma.

Effect of trans-retinoic acid in the inhibition of cholesteatoma in guinea pigs

Middle ear cholesteatoma affected more than 5 million people until the 80;s. Many animal models were used, unsuccessfully, to study an alternative therapy to cholesteatoma.

AIM

observe the effect of the trans-retinoic acid in the inhibition of middle ear cholesteatomas induced by propylene glycol.

STUDY DESIGN

Clinical and Experimental.

METHODS

25 guinea pigs were submitted to the application of a 100% propylene glycol solution in their bulla bilaterally and a solution of trans-retinoic acid was applied locally in the external right ear, while in the left ear saline solution was applied (control ear). The guinea pigs were slaughtered and their temporal bones were prepared for macroscopic and histological analysis.

RESULTS

The macroscopic findings had evidenced the presence of cholesteatoma in 25% of the right ears and 85% of the left ears (P=0.0003 *). The histological study had evidenced the presence of cholesteatoma in 30% of right ears and 75% of the left ears (P=0.0104*).

CONCLUSION

The local use of the trans-retinoic acid is effective in inhibiting the induced formation of cholesteatomas in guinea pigs.

Efeito do ácido trans-retinóico na inibição de colesteatoma em cobaias

O colesteatoma de orelha média atingia mais de 5 milhões de pessoas até a década de 80. Vários modelos animais já foram utilizados para alternativas de tratamento do colesteatoma sem sucesso. OBJETIVO: Estudar os efeitos do ácido trans-retinóico, uso tópico na orelha externa em cobaias, na inibição da formação do colesteatoma de orelha média induzido pelo propilenoglicol. Estudo experimental prospectivo. MATERIAL E MÉTODOS: 25 cobaias foram submetidas à aplicação de propilenoglicol a 100% na bula timpânica bilateralmente e uma solução de ácido trans-retinóico foi aplicada topicamente (total de 5 aplicações) na orelha externa, região justa-timpânica, na orelha direita, enquanto na orelha esquerda aplicou-se solução fisiológica (orelha controle). As cobaias foram sacrificadas após 6 semanas do procedimento inicial e os ossos temporais foram separados, fixados e descalcificados, para análise macroscópica e histológica. RESULTADOS: Os achados macroscópicos evidenciaram a presença e suspeita de colesteatoma em 25% das orelhas direitas e 85% das orelhas esquerdas (P=0,0003*). Os achados histológicos dos 40 ossos temporais evidenciaram a presença de colesteatoma em 30% das orelhas direitas e 75% das orelhas esquerdas (P=0,0104*). CONCLUSÃO: O uso tópico do ácido trans-retinóico é efetivo na inibição da formação de colesteatoma induzido pelo propilenoglicol em cobaias.

Clinical efficacy of 5-fluorouracil (5-FU) topical cream for treatment of cholesteatoma

OBJECTIVE

In order to clarify clinical efficacy of commercially available 5-fluorouracil (5-FU) topical cream, a clinical study was conducted.

METHODS

Two to three cubic millimetres of 5-FU topical cream (Kyowa, Roche) was applied on 50 cases of various types of cholesteatoma (50 patients) two to five times with the interval of 2 weeks, and its clinical efficacy was evaluated by the criteria we developed.

RESULTS

In total, 59% of the cholesteatomas showed good effect, 29% of them showed fair effect, and the effect was poor in the remaining 12%. It was particularly effective in cholesteatomas in the EAC, attic cholesteatomas with an aerated mastoid, and in recurrent-type cholesteatomas.

CONCLUSION

5-FU topical cream appeared effective for the treatment of cholesteatomas.

Tumors of the skull base in children: review of tumor types and management strategies

Although many treatment strategies for skull base tumors in adults have been reported, relatively little has been reported regarding such therapies in the pediatric population. Skull base tumors in children present a therapeutic challenge because of their unique pathological composition, the constraints of the maturing skull and brain, and the small size of the patients. In this review, the authors examine the pediatric skull base lesions that occur in the anterior, middle, and posterior cranial base, focusing on unique pediatric tumors such as encepahalocele, fibrous dysplasia, esthesioneuroblastoma, craniopharyngioma, juvenile nasopharyngeal angiofibroma, cholesteatoma, chordoma, chondrosarcoma, and Ewing sarcoma. They review management strategies that include radio- and chemotherapy, as well as surgical approaches with emphasis on the modifications and complications associated with the procedures as they apply in children. Evidence for the advantages and limitations of radiotherapy, chemotherapy, and surgery as it pertains to the pediatric population will be examined. With a working knowledge of skull base anatomy and special considerations of the developing craniofacial skeleton, neurosurgeons can treat skull base lesions in children with acceptable morbidity and mortality rates. Outcomes in this population may be better than those in adults, in part because of the benign histopathology that frequently affects the pediatric skull base, as well as the plasticity of the maturing nervous system.