Creating a stable tympanic membrane perforation using mitomycin C

Tympanic Membrane Regeneration Therapy for Pediatric Tympanic Membrane Perforation

OBJECTIVE

To evaluate tympanic membrane regeneration therapy (TMRT) for pediatric tympanic membrane perforations (TMPs).

STUDY DESIGN

Intervention study.

SETTING

Research institute hospital.

PATIENTS

In this study, 20 patients with chronic TMP (M/F: 13/7, 13/8 ears, age 0-15 years) treated with TMRT were evaluated. As comparison, 20 pediatric patients with chronic TMP who underwent myringoplasty/tympanoplasty were included.

INTERVENTIONS

For the TM repair procedure, the edge of the TMP was disrupted mechanically, and gelatin sponge immersed in basic fibroblast growth factor was placed inside and outside the tympanic cavity and covered with fibrin glue. The TMP was examined 4 ± 1 weeks later. The protocol was repeated up to four times until closure was complete.

MAIN OUTCOME MEASURES

Closure of the TMP and hearing improvement were evaluated at 16 weeks after the final regenerative procedure. Adverse events were monitored.

RESULTS

The mean follow-up period was 427.1 days. The TM regenerated in all cases, but pinhole reperforation occurred in two cases, and the final closure rate was 90.5% (19 of 21). Hearing improved to 24.9 ± 7.6 dB on average before surgery and to 13.8 ± 5.4 dB after surgery. The AB gap improved from 12.9 ± 8.0 to 5.2 ± 3.5 dB.The myringoplasty/tympanoplasty group had significantly lower AB gap improvement compared with the TMRT group. There were no adverse events.

CONCLUSIONS

TMRT can be expected to regenerate near-normal TMs with a high closure ratio, resulting in better-hearing improvement compared with the myringoplasty/tympanoplasty group, and is an effective treatment for children with long life expectancy.

Three-Dimensional-Printed GelMA-KerMA Composite Patches as an Innovative Platform for Potential Tissue Engineering of Tympanic Membrane Perforations

Tympanic membrane (TM) perforations, primarily induced by middle ear infections, the introduction of foreign objects into the ear, and acoustic trauma, lead to hearing abnormalities and ear infections. We describe the design and fabrication of a novel composite patch containing photocrosslinkable gelatin methacryloyl (GelMA) and keratin methacryloyl (KerMA) hydrogels. GelMA-KerMA patches containing conical microneedles in their design were developed using the digital light processing (DLP) 3D printing approach. Following this, the patches were biofunctionalized by applying a coaxial coating with PVA nanoparticles loaded with gentamicin (GEN) and fibroblast growth factor (FGF-2) with the Electrohydrodynamic Atomization (EHDA) method. The developed nanoparticle-coated 3D-printed patches were evaluated in terms of their chemical, morphological, mechanical, swelling, and degradation behavior. In addition, the GEN and FGF-2 release profiles, antimicrobial properties, and biocompatibility of the patches were examined in vitro. The morphological assessment verified the successful fabrication and nanoparticle coating of the 3D-printed GelMA-KerMA patches. The outcomes of antibacterial tests demonstrated that GEN@PVA/GelMA-KerMA patches exhibited substantial antibacterial efficacy against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Furthermore, cell culture studies revealed that GelMA-KerMA patches were biocompatible with human adipose-derived mesenchymal stem cells (hADMSC) and supported cell attachment and proliferation without any cytotoxicity. These findings indicated that biofunctional 3D-printed GelMA-KerMA patches have the potential to be a promising therapeutic approach for addressing TM perforations.

Decellularized tympanic membrane scaffold with bone marrow mesenchymal stem cells for repairing tympanic membrane perforation

BACKGROUND

Tympanic membrane perforation (TMP) is a common disease in otology, and few acellular techniques have been reported for repairing this condition. Decellularized extracellular matrix (ECM) scaffolds have been used in organ reconstruction.

OBJECTIVE

This study on tissue engineering aimed to develop a tympanic membrane (TM) scaffold prepared using detergent immersion and bone marrow mesenchymal stem cells (BMSCs) as repair materials to reconstruct the TM.

RESULTS

General structure was observed that the decellularized TM scaffold with BMSCs retained the original intact anatomical ECM structure, with no cell residue, as observed using scanning electron microscopy (SEM), and exhibited low immunogenicity. Therefore, we seeded the decellularized TM scaffold with BMSCs for recellularization. Histology and eosin staining, SEM and immunofluorescence in vivo showed that the recellularized TM patch had a natural ultrastructure and was suitable for the migration and proliferation of BMSCs. The auditory brainstem response (ABR) evaluated after recellularized TM patch repair was slightly higher than that of the normal TM, but the difference was not significant.

CONCLUSION

The synthetic ECM scaffold provides temporary physical support for the three-dimensional growth of cells during the tissue developmental stage. The scaffold stimulates cells to secrete their own ECM required for tissue regeneration. The recellularized TM patch shows potential as a natural, ultrastructure biological material for TM reconstruction.

3D printing technology and applied materials in eardrum regeneration

Tympanic membrane perforation is a common condition in clinical otolaryngology. Although some eardrum patients can self-heal, a long period of non-healing perforation leads to persistent otitis media, conductive deafness, and poor quality of life. Tympanic membrane repair with autologous materials requires a second incision, and the sampling site may get infected. It is challenging to repair tympanic membranes while maintaining high functionality, safety, affordability, and aesthetics. 3D bioprinting can be used to fabricate tissue patches with materials, factors, and cells in a design manner. This paper reviews 3D printing technology that is being used widely in recent years to construct eardrum stents and the utilized applied materials for tympanic membrane repair. The paper begins with an introduction of the physiological structure of the tympanic membrane, briefly reviews the current clinical method thereafter, highlights the recent 3D printing-related strategies in tympanic membrane repair, describes the materials and cells that might play an important role in 3D printing, and finally provides a perspective of this field.

Tissue engineering and regenerative medicine strategies for the repair of tympanic membrane perforations

Despite the high success rate of autologous grafts in tympanic membrane repair, clinical alternatives are required for the closure of unresponsive chronic perforations that can lead to recurring infection and hearing loss. Tissue engineering and regenerative medicine approaches have emerged as another strategy to repair the eardrum, in addition to negating the need for donor tissue harvest and related surgical iatrogenicities. This review highlights the main approaches using biomaterials, growth factors, and cell therapies towards the healing of complex TM perforations. In addition, we discuss the challenges and advances for the development of reliable animal models, which will allow the optimisation and development of novel techniques. Finally, we indicate technologies that are currently used clinically and others that are closer to the market. The advances here discussed on tissue engineering and regenerative medicine strategies applied to the field of TM perforations will allow otologists, surgeons, and researchers to better bring novel technologies to the bedside as well as to develop new ones.

Topical Application of bFGF Alone for the Regeneration of Chronic Tympanic Membrane Perforations: A Preliminary Case Series

Results

A total of 29 patients consisting 13 in the bFGF alone group and 16 in the myringoplasty group were finally included in the analysis. Of the 13 patients in the bFGF alone group, the perforations were small in 6 and medium in 7; the etiology was secondary to COM in 11 and to trauma in 2. One patient with an unhealed perforation continued bFGF treatment until 6 months, while the others stopped at 3 months. Of the seven medium-sized perforations, none of the five COM perforations closed, while the two traumatic perforations achieved complete closure within 2 and 4 weeks, respectively. The successful closure rate was 28.6% (2/7). Successful closure was achieved in 66.7% (4/6) of the six small perforations with COM, with a mean closure time of 4.75 weeks. Of the 16 patients in the myringoplasty group, all perforations were medium-sized and were secondary to COM in 15 cases and traumatic in 1 case; all achieved complete closure.

Conclusions

bFGF alone facilitated the repair of chronic traumatic perforations and small perforations with COM, but not medium-sized perforations with COM. These observations indicated that the regenerative conditions of traumatic perforations are better than those of COM perforations when using bFGF alone, and that graft materials could play a critical role in the regeneration of larger-sized chronic perforations with COM.

Contact Diode Laser Myringotomy and Mitomycin C in Children

OBJECTIVE: To investigate the use of contact diode laser myringotomy (C-LAM), combined with topical mitomycin C, as an alternative method for prolonged middle ear ventilation in children with otitis media with effusion.

STUDY DESIGN AND SETTING: Prospective study at a tertiary care pediatric institution.

METHODS: Fifteen children enrolled in the study. Mitomycin C was applied to the intact tympanic membrane in the right ears, whereas saline on the left side was used for controls. C-LAM was then performed in all ears. Outcome measures included healing rate and scarring, ear infection, and long-term audiometric follow-up.

RESULTS: There was no significant difference in median healing rate. In each group, the median was between the third and fourth month. Normal hearing thresholds were obtained in all children at 2-year follow-up.

CONCLUSION: C-LAM proved to be an effective method for medium-term ventilation, but topical mitomycin C before C-LAM did not prolong patency rate in our patients. No significant complication was encountered at 2-year follow-up. (Otolaryngol Head Neck Surg 2004;130:742-6.)

Refining indications for the use of mitomycin C using a randomized controlled trial with an animal model

Objectives

To evaluate the effect of mitomycin on the repair of acquired subglottic stenosis and to define the optimal concentration of mitomycin that would minimize restenosis after repair.

Study Design And Setting

A randomized prospective model was used in which 20 ferrets ( Mustela putorius furo) underwent simulated intubation injury that was then treated with CO2 laser lysis.

Results

Comparison of cross-sectional airway areas, after stenosis repair, showed no significant differences between control and mitomycin treatment groups. Comparison of histologic scores for both inflammation and mucosalization yielded no difference between control and treatment animals.

Conclusions

Mitomycin C appeared to have no benefit when placed after repair of an acquired stenosis.

Significance

This study closely models the injury experienced by children with acquired subglottic stenosis. These data provide clear evidence that mitomycin is limited in its effect on established wounds and help further define its role as an adjuvant for surgery in the aerodigestive tract.

Direct application of bFGF without edge trimming on human subacute tympanic membrane perforation

OBJECTIVE

To investigate the feasibility of direct application of basic fibroblast growth factor (bFGF) without edge trimming on human subacute traumatic tympanic membrane perforation (TMP).

METHODS

A total of 29 patients with traumatic TMPs beyond 1 month after trauma were enrolled. Patients were placed into two groups: an observation group (n=17) and a bFGF-treated group (n=12). The bFGF-treated group was treated by direct application of bFGF, in which the margin of the perforation was not trimmed. All patients were followed at least once per week until the perforation was completely closed or for up to 6 months. The closure rate and closure time were estimated.

RESULTS

At 6 months, 11/12 (91.7%) perforations achieved complete closure after bFGF treatment. The mean closure time was 18.1 ± 11.4 days (range=3-65 days). Purulent otorrhea was found after treatment in five patients, but resolved after oral amoxicillin and ofloxacin ear drops. Of these five patients, four achieved complete closure. However, only 9/17 (52.9%) perforations achieved complete spontaneous closure in the observation group. FGF-treated groups had significantly improved closure rates compared to the observation group (91.7% vs. 52.9%, respectively, P=0.03).

CONCLUSIONS

Although the margin of the perforation was not trimmed, direct application of bFGF on human subacute TMP was feasible, and it could significantly improve the closure rate of the subacute TMPs. The technique was simple and convenient. Thus, direct application of bFGF should be recommended pre-myringoplasty.

Animal models of chronic tympanic membrane perforation: a 'time-out' to review evidence and standardize design

OBJECTIVE

To review the literature on techniques for creation of chronic tympanic membrane perforations (TMP) in animal models. Establishing such models in a laboratory setting will have value if they replicate many of the properties of the human clinical condition and can thus be used for investigation of novel grafting materials or other interventions.

METHODS

A literature search of the PubMed database (1950-August 2014) was performed. The search included all English-language literature published attempts on chronic or delayed TMP in animal models. Studies of non English-language or acute TMP were excluded.

RESULTS

Thirty-seven studies were identified. Various methods to create TMP in animals have been used including infolding technique, thermal injury, re-myringotomy, and topical agents including chemicals and growth factor receptor inhibitors. The most common type of animal utilized was chinchilla, followed by rat and guinea pig. Twenty three of the 37 studies reported success in achieving chronic TMP animal model while 14 studies solely delayed the healing of TMP. Numerous experimental limitations were identified including TMP patency duration of <8 weeks, lack of documentation of total number of animals attempted and absence of proof for chronicity with otoscopic and histologic evidence.

CONCLUSION

The existing literature demonstrates the need for an ideal chronic TMP animal model to allow the development of new treatments and evaluate the risk of their clinical application. Various identified techniques seem promising, however, a need was identified for standardization of experimental design and evidence to address multiple limitations.

Myringotomy in the Junbo mouse model of chronic otitis media alleviates inflammation and cellular hypoxia

OBJECTIVES/HYPOTHESIS

Ventilation of the chronically inflamed middle ear is a key outcome in functional middle ear surgery. Grommets eliminate middle ear effusion, but there is also evidence that they downregulate inflammation. The reason for this is not understood, but there is little to suggest alteration in eustachian tube ventilatory capacity. Previous work has shown that the Junbo mouse model of chronic otitis media has hypoxic middle ear mucosa and bulla fluid leucocytes. Here we explore whether surgical ventilation may alleviate chronic otitis media through downregulation of hypoxia.

STUDY DESIGN

Surgical intervention on a mouse model of disease.

METHODS

We established patency of myringotomy incision as 5 days in wild-type mice. We performed unilateral myringotomy on three cohorts of mice: 10 wild-type controls, 12 Junbo mice, and 15 Junbo mice with additional removal of middle ear effusion. A small cohort of these mice were labeled in vivo by intraperitoneal injection of pimonidazole to identify tissue hypoxia. Tissues were assessed for mucoperiosteal thickening and pimonidazole labeling, comparing operated to nonoperated ears.

RESULTS

Ventilation of the inflamed Junbo middle ear revealed significant reduction in inflammatory thickening associated with loss of pimonidazole labeling, suggesting resolution of cellular hypoxia.

CONCLUSIONS

Surgical ventilation may achieve therapeutic effect through alleviation of cellular hypoxia in the chronically inflamed middle ear. Targeted molecular therapy of hypoxia signaling may offer future alternative therapy for chronic otitis media.

Animal models of chronic tympanic membrane perforation: in response to plasminogen initiates and potentiates the healing of acute and chronic tympanic membrane perforations in mice

Tympanic membrane perforations (TMP) are relatively common but are typically not treated in their acute stage, as most will heal spontaneously in 7–10 days. Those cases which fail to heal within 3 months are called chronic TMP which attract surgical intervention (e.g. myringoplasty), typically with a temporalis fascia autograft. New materials for the repair of chronic TMP are being developed to address deficiencies in the performance of autografts by undergoing evaluation in animal models prior to clinical study. However, there is currently a lack of ideal chronic TMP animal models available, hindering the development of new treatments. Various techniques and animal species have been investigated for the creation of chronic TMP with varied success. In the present commentary, we bring to the attention of readers the recent report by Shen et al. in Journal of Translational Medicine. The study reported the creation of a chronic TMP animal model in plasminogen gene deficient mice. However, the short observation time (9, 19 days), lack of success rate and the scarcity of solid evidence (e.g. otoscopic & histologic images) to confirm the chronicity of TMP warrant a more thorough discussion.

Microscopic comparison of topical use of Mitomycin C and Fluorouracil on cold knife myringotomy

Objective/hypothesis A comparison of the histopathological effect of topical use of Mitomycin C and 5-Fluorouracil in preventing myringotomy closure in rats.

STUDY DESIGN

clinical trial. Methods and materials The study was performed on 43 rats that were divided into three groups. Study groups (A and B) and control group (C) after bilateral cold-knife myringotomy, we applied Mitomycin C (MMC) 4mg/ml to group A, 5-Fluouracil (5FU) 50mg/ml to group B, and normal saline to group C. An examination of all ears of rats was carried out by otoscope on days 0, 1, 3, 5, 7, and then every five days up to 70 days. Each day's closed myringotomies of all groups were examined. Results The mean of post myringotomy opening time was 37, 16, and 12 days respectively in MMC, 5FU, and saline. Patency duration of MMC group was significantly long (p<0.0001), but in histopatholgical examinations, sclerosis of tympanic membrane in MMC group showed the highest patency duration (p<0.0001). Conclusion Mitomycin C significantly prolonged the duration of myringotomy patency time - longer than 5-Fluouracil and saline but with the adverse effects of tympanic membrane fibrosis.

Is there any synergic effect for coadministration of mitomycin C and halofuginone on the skin wound healing?

OBJECTIVE

This study compared the potencies of the antifibrotic agents mitomycin C (MMC) and halofuginone (HFN) and investigated whether coadministration of these agents produces synergic effects in an animal skin wound model.

SUBJECTS AND METHODS

Twenty male Sprague-Dawley rats were used for this study. After a full-thickness excisional wound was made on the dorsum of each rat, each rat was treated with topical mitomycin, intraperitoneal HFN, or both. Wound surface areas were measured over time, and histologic analysis was performed after wounds healed completely.

RESULTS

The groups treated with MMC alone, HFN alone, and a combination of the two all exhibited delayed wound healing compared with the untreated group. Histologically, fibrosis and matrix metalloproteinase-2 expression were significantly inhibited in the treated groups. However, there were no gross or histologic differences between the MMC-treated group, the HFN-treated group, and the combination-treatment group.

CONCLUSIONS

Both MMC and HFN inhibited excessive fibrosis. However, there was no significant difference in the antifibrotic effects of MMC and HFN on surgically induced skin wounds. Moreover, combination treatment with both MMC and HFN failed to confer an additional antifibrotic effect on skin wounds when compared with treatment with MMC or HFN alone.

Repair of the tympanic membrane with urinary bladder matrix

OBJECTIVES/HYPOTHESIS

To test urinary bladder matrix (UBM) as a potential treatment for tympanic membrane (TM) healing and regeneration.

STUDY DESIGN

This prospective pilot study was designed to provide both qualitative and semiquantitative assessment of temporal and spatial healing events in the chinchilla model of chronic TM perforations with and without UBM patching.

METHODS

Bilateral myringotomies were performed and repeated as necessary to create subtotal perforations over an 8-week period. Myringoplasty was then performed, with left TMs serving as controls and right TMs receiving UBM patches. TMs were excised at 4 weeks, 8 weeks, and 12 weeks. Fixed tissue samples were characterized for gross morphology, then processed for microscopic evaluation.

RESULTS

Chronic perforations were maintained with one or more repeated myringotomies. Although both control and patched TMs were thicker than native tissue, patched TMs were transparent and uniform in thickness without any inclusions. UBM patches were readily degraded and replaced by newly deposited and organized host tissue that recapitulated the native TM layers.

CONCLUSIONS

UBM scaffolds were an effective biological scaffold for TM closure and tissue remodeling, leading to thicker than normal anatomy but otherwise normal morphology. Future studies are required to determine functional and temporal outcomes as well as alternative patch orientations. The results show particular promise as a superior alternative means of reconstructing not only chronic TM perforations but also dimeric TMs associated with retraction pockets and atelectasis. Laryngoscope, 2009.

Study of Wound Healing in Rats Treated with Topical and Injected Mitomycin C

Objectives:

Mitomycin C, a widely used chemotherapeutic drug, has been proposed as a potential adjuvant for the control of scar tissue in surgical wounds because of its capacity to inhibit fibroblast proliferation. The current study used a combination of topical and injected mitomycin C to slow the healing process of surgical wounds in rats.

Methods:

An experimental model of surgical wounding at the dorsum of rats was used. A total of 43 animals were subdivided into 3 groups: Control, topical mitomycin C, and a combination of topical treatment and intradermal injections of the drug at 30 and 60 days after the initial topical treatment. After 3 months, the animals were painlessly sacrificed and the surgical scars were removed for microscopic analysis.

Results:

The group that received only topical mitomycin C presented milder inflammatory signs and consequently had a less intense healing process than the control group. The group treated with a combination of both topical and injected mitomycin C presented results comparable to those of the control group.

Conclusions:

The toxic characteristics of mitomycin C were most likely responsible for the greater tissue damage that occurred when it was used in the injected form, causing increased scar tissue formation. Mitomycin C slows the healing process of surgical wounds when used topically, but causes enhanced scar tissue formation when injected.

Chronic tympanic membrane perforation: a better animal model is needed

Developments in the treatment of chronic tympanic membrane perforation have been hindered by the lack of an ideal animal model. It is not appropriate to test such treatments on acute perforations as the majority of these heal spontaneously. An ideal animal model would be one that most closely resembles the human clinical situation. It should be inexpensive, readily available, and easy to create. There have been a number of attempts to create a chronic tympanic membrane perforation model with limited success. All published attempts at chronic tympanic membrane perforations have been reviewed and the limitations of each model are discussed. A number of areas for research exist for further developing a chronic tympanic membrane perforation model. These areas include a perforation model in the presence of bacteria and eustachian tube dysfunction. Understanding the molecular and genetic mechanisms of chronic otitis media and potential treatments will also be useful.

Effects of Ciprofloxacin/Dexamethasone and Ofloxacin on Tympanic Membrane Perforation Healing

HYPOTHESIS:: Exposure to ciprofloxacin/dexamethasone, but not ofloxacin, prolongs tympanic membrane (TM) healing. BACKGROUND:: Exposure to hydrocortisone has been shown to delay TM wound healing. No published studies have compared the effects of ciprofloxacin/dexamethasone and ofloxacin on TM healing. METHODS:: Noninfected TM perforations were created in 30 rats. The rats were split into three groups, and ciprofloxacin/dexamethasone, ofloxacin, or isotonic sodium chloride solution drops were instilled for 8 days. Tympanic membrane healing was analyzed at specified intervals using photographic documentation verified by a blinded observer. RESULTS:: The isotonic sodium chloride solution control and ofloxacin-exposed TMs healed at similar rates. There was a statistically significant delay in TM healing in the ciprofloxacin-/dexamethasone-exposed TMs by postoperative Day 10. However, all TM perforations were healed by postoperative Day 20. CONCLUSION:: Ciprofloxacin/dexamethasone delays healing of experimental TM perforations, but the brief exposure in this study did not cause persistent perforations.

Topical Application of Mitomycin C to the Middle Ear Is Ototoxic in the Gerbil

HYPOTHESIS

Mitomycin C is ototoxic when applied topically to the structures of the middle ear.

BACKGROUND

Mitomycin C is a topically applied medication widely used in a variety of surgical procedures to prevent excessive scar tissue formation. Its safety for use during otologic procedures has not been fully evaluated.

METHODS

A laboratory study was undertaken using the Mongolian gerbil as an animal model. Both acute and chronic effects on cochlear function of mitomycin C were assessed with measurements of compound action potential (CAP) thresholds of the auditory nerve, CAP input/output functions, distortion product otoacoustic emissions, and endocochlear potentials. Morphologic changes were assessed with light microscopy using hematoxylin-eosin staining as well as transmission electron microscopy.

RESULTS

Five-minute applications of mitomycin C (0.5 mg/ml) to the entire surface of the middle ear adversely affected CAP thresholds, input/output functions, distortion product otoacoustic emissions, and the endocochlear potential. Ninety-minute exposures of mitomycin C solely to the round window produced similar changes. Histologic evaluation of animals 1 week after treatment showed damage to cochlear hair cells, the stria vascularis, and spiral ganglion neurons when compared with controls.

CONCLUSION

Mitomycin C can produce substantial sensorineural hearing loss when applied topically to the gerbil middle ear for even brief periods. Consequently, its safety for topical use in the human middle ear is highly questionable.

Topical Application of Mitomycin C in Combination with Dexamethasone: Effective Delay of Myringotomy Closure

The object of this study was to investigate the efficacy of topical mitomycin C (MMC) in combination with subsequent topical dexamethasone to prolong the patency of myringotomies. Bilateral instrumental myringotomies were performed in 12 rats. On both sides, a solution of MMC (2 mg/ml) was applied to the intact tympanic membrane for ten minutes before myringotomy. Dexamethasone (4 mg/ml) was applied to one tympanic membrane of each animal at days 3, 6, 9 and 14. Tympanic membranes were observed weekly for a total of 9 weeks. The mean healing period was found to be 17.5 days (range 4.5-45.5 days) in the group with MMC alone, and 32 days (range 17.5-59.5 days) in the group MMC + dexamethasone. The difference was significant. A combination of topical MMC and subsequent dexamethasone did delay the healing rate of myringotomies in rat tympanic membranes longer than MMC alone.

Topical Application of Mitomycin C before versus after Myringotomy: An Experimental Study

The objective of this animal study was to compare topical mitomycin C (MMC) before and after nonlaser myringotomy. Bilateral myringotomies were performed in 12 rats. On the left side, MMC was applied to the intact tympanic membrane for 10 min before myringotomy (preapplication group). On the right side, MMC was applied to the tympanic membrane following myringotomy. Tympanic membranes were observed for a total of 8 weeks. By day 35, all myringotomies with application of MMC after perforation of the tympanic membrane were closed, whereas 42% of the myringotomies with application of MMC prior to perforation remained patent. One tympanic membrane in the preapplication group showed an enlargement of the perforation with partial destruction of the malleus. The present study showed that the application of MMC to the intact tympanic membrane prolongs the patency of nonlaser myringotomies in rats. Specific side effects of the MMC application must be kept in mind.

Radiofrequency Myringotomy with the Topical Use of Mitomycin C: An Experimental Study

OBJECTIVE

To assess the use of radiofrequency myringotomy in combination with mitomycin C as an alternative myringotomy technique on rabbits.

STUDY DESIGN

Experimental animal research protocol.

SETTING

University of Crete, School of Medicine, Medical Experimental Education and Research Center.

METHODS

Radiofrequency myringotomies were performed under general anesthesia on both ears of 20 rabbits. Mitomycin C (0.3 mg/ml) pledgets were applied in the right ears (study group) and saline pledgets in the left ears (control group). Animals were monitored using otomicroscopy weekly until myringotomy closure. Kaplan-Meier survival techniques were used to compare myringotomy patency time between the two sides.

INTERVENTION

Radiofrequency myringotomy under general anesthesia on both ears of 20 rabbits.

MAIN OUTCOME MEASURE

Myringotomy patency time.

RESULTS

The mean patency time of the study group was 5.45 weeks (95% confidence interval, 5.185-5.715 weeks). The mean patency rate for the control side was 1.60 weeks (95% confidence interval, 1.38-1.82 weeks). The Breslow (generalized Wilcoxon) test showed the study group to have significantly longer patency of radiofrequency myringotomy than the control group (p<0.0001).

CONCLUSION

The patency period of radiofrequency myringotomy was not long enough to be proposed as an alternative to the insertion of ventilation tubes, although mitomycin C had a significant adjunct effect in prolonging the patency rate of radiofrequency myringotomy on rabbits.

Systemische Kortikoidgaben und additive lokale Applikation von Mitomycin oder Dexamethason

BACKGROUND

The purpose of this study was to determine whether systemic glucocorticoid application, in combination with topical mitomycin or dexamethasone, prolongs the patency of a tympanic membrane perforation.

METHOD

Bilateral myringotomies were performed on 24 rats. The 48 ears were separated into eight groups. Treatment with combined systemic and topical dexamethasone or mitomycin differed between these groups. After the first 2 weeks, the animals were checked weekly for a total of 12 weeks.

RESULTS

A combination of systemic and topical dexamethasone delayed tympanic membrane closure after myringotomy. Perforation size increased in all tympanic membranes treated with mitomycin plus systemic dexamethasone.

CONCLUSION

Topical mitomycin plus systemic glucocorticoid may lead to a massive malfunction of tympanic membrane healing.

Effects of topical application of mitomycin-C and 5-fluorouracil on myringotomy in rats

OBJECTIVE

The effects of topical application of Mitomycin-C (MMC) and 5-fluorouracil (5-FU) for maintaining myringotomy patency were investigated in this experimental study.

STUDY DESIGN

We performed simple myringotomy with a knife on 140 tympanic membranes of 70 rats. Rats were divided in two study groups and a control group. Each study group had 60 tympanic membranes, and the control group had 20. We applied Mitomycin-C (0.4 mg/ml) in Group A, 5-fluorouracil (50 mg/ml) in Group B topically, and sterile saline in the control group for 10 minutes. Examination was made with otoendoscope on days 1, 3, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, and 70, and patency rates were recorded.

RESULTS

MMC and 5-FU Groups remained open for a mean of 46.17 days and 14.62 days, respectively. The control ears healed within 10.4 days. Fibrosis of the MMC-treated group was the same as that of 5-FU-treated groups. Fibrosis of both study groups was significantly lower than that of the control group.

CONCLUSIONS

MMC is more effective than 5-FU, which is more effective than the simple myringotomy procedure in extending the patency of myringotomies in rat tympanic membranes (p < 0.05). Both medications are useful as an adjunct in preventing myringotomy closure.

Use of mitomycin C for treatment of keloid: a preliminary report

OBJECTIVES

Mitomycin C (MC) is an anti-neoplastic agent with an anti-proliferative effect on fibroblasts. We set out to evaluate the effect of MC application following keloid excision.

STUDY DESIGN AND SETTING

Patients with keloid in a tertiary referral center were enrolled in a prospective study. The scar was excised and prior to skin closure, a pledget with 1 cc of MC 0.4 mg/mL was applied for 5 minutes. Patient satisfaction and keloid thickness were assessed.

RESULTS

All patients were satisfied with the results, although complete disappearance of the keloid was evident only in two. Keloid thickness was measured and ranged from 5 to 26 mm. Following surgery and treatment at 2 months thickness ranged from 0 to 8 mm.

CONCLUSIONS

MC application following scar resection appears to be effective in treatment of keloid.

SIGNIFICANCE

As no specific effective treatment for keloid is currently available, utilization of this readily available therapeutic agent may improve treatment outcome.

[An improved animal model for chronic perforation of the tympanic membrane]

BACKGROUND

An inexpensive and valid animal model of chronic tympanic membrane perforation is needed.

METHOD

Twelve male rats were selected for different surgical procedures (subtotal tympanic membrane perforation with local microflaps, re-perforation without flaps, partial excision of the handle of malleus). The inhibition of spontaneous healing was accomplished by the application of prednisolon or mitomycin directly onto the tympanic membrane.

RESULTS

Only by additional partial excision of the handle of malleus followed by local application of mitomycin were we able to achieve a persistent tympanic membrane perforation.

CONCLUSION

Chronic tympanic membrane perforation using this procedure may be useful in further investigations of the medical impact of tympanic membrane healing.

Clinical and Histological Healing of Surgical Wounds Treated With Mitomycin C

OBJECTIVES/HYPOTHESIS

The proven ability of mitomycin C to inhibit fibroblasts in vitro has stimulated its use in research animals and in humans to control healing. The objective of the study was to follow the healing process of surgical wounds in the dorsum of rats treated topically with mitomycin C.

STUDY DESIGN

Prospective experimental study.

METHODS

Two distinct surgical wounds were made to the dorsum of 10 adult rats. One of the wounds received topical mitomycin C diluted at 0.5 mg/mL during a 5-minute period, and the other wound was used as a control. The healing process was followed clinically and histologically after the rats were killed at different post-treatment periods. The degree of fibrosis was evaluated histologically by two different pathologists.

RESULTS

Surgical wounds treated with mitomycin C presented delayed healing when compared with the untreated wounds, with remission of scabs 7 days after the control wounds. Histological analysis at 1 month after treatment revealed a significant reduction in fibrosis of the wounds treated with mitomycin C when compared with the untreated wounds. After the third month the degree of fibrosis was comparable in both wounds.

CONCLUSION

Topical mitomycin C delays the healing of surgical wounds in rats up to the fourth week following treatment, but the degree of fibrosis is comparable in both treated and untreated wounds after 12 weeks. In otolaryngology this characteristic of the drug may be useful in the treatment of external ear canal stenosis, choanal atresias, nasal cicatricial stenosis, laryngeal stenosis, and keloids.

Dose-Response Relationship of Topically Applied Mitomycin C for the Prevention of Laser Myringotomy Closure

OBJECTIVE: We sought to determine a dose-response curve for topical mitomycin C when used to prolong the patency of laser-assisted myringotomies.

STUDY DESIGN AND SETTING: Bilateral myringotomies were performed using the argon laser in 40 guinea pigs with normal ears. Pledgets with (0.05, 0.2, 0.4, or 2.0 mg/mL) mitomycin C were applied topically. Monitoring consisted of weekly or biweekly otomicroscopy.

RESULTS: As in previous studies, all saline-treated myringotomies closed by day 7. By day 14, all myringotomies (100%) in the 0.05 mg/mL group were closed. By contrast, all myringotomies (100%) remained patent in the 0.2 and 0.4 mg/mL treatment groups, and 56% of the myringotomies remained patent in the 2.0 mg/mL group at day 14. By day 56, all myringotomies were closed in the 2.0 mg/mL group, 5 (50%) myringotomies were patent in the 0.4 mg/mL group, and 1 (11%) myringotomy was patent in the 0.2 mg/mL group. The study was terminated on day 84 (12 weeks). At that time, only the 0.4 mg/mL group had patent myringotomies (n = 3; 30%). The highest dose (2.0 mg/mL) of mitomycin was significantly associated with otorrhea. Otorrhea also appeared to be associated with earlier myringotomy closure.

CONCLUSION: There is a dose-response curve for topical mitomycin C when used for prolonging my-ringotomy patency in doses up to 0.4 mg/mL. Higher doses do not appear to prolong patency and are associated with greater otorrhea, suggesting middle ear toxicity.

Tratamento cirúrgico da otite média com efusão: tubo de ventilação versus aplicação tópica de mitomicina C

O uso do tubo de ventilação (TV) da orelha média, tratamento cirúrgico eleito da otite média com efusão (OME), não é isento de complicações, promovendo ainda limitação social pela necessidade de abandono dos banhos de imersão. A mitomicina C (MMC) é um antineoblástico, cuja aplicação tópica retarda a fibrose e previne a estenose cicatricial. Em cobaias, retardou o fechamento de timpanotomias, permitindo maior tempo de aeração da orelha média, à semelhança dos tubos de ventilação. FORMA DE ESTUDO: Clínico prospectivo. OBJETIVO: Comparar a eficácia entre timpanotomia, aspirado da efusão e inserção de tubo de ventilação (grupo TV) versus timpanotomia, aspirado da efusão e aplicação tópica de mitomicina C (grupo MMC). Comparar o tempo de manutenção da timpanotomia e a incidência de complicações nos dois grupos. RESULTADOS: O grupo MMC apresentou eficácia significativamente menor (52% versus 80%) que o grupo TV (p= 0,34). A presença de timpanometria tipo "B" e a ausência de comprometimento do óstio faríngeo tubário pelo tecido adenóide no pré-operatório representaram fatores de mau prognóstico. A aplicação tópica de MMC nas bordas da timpanotomia proporcionou um tempo de abertura da membrana timpânica por duas a três semanas. No grupo TV, a otorréia foi observada em 13,3% dos pacientes. No grupo MMC, apesar da menor eficácia, nenhum paciente apresentou complicações nem sofreu prolongada proibição dos banhos de imersão. CONCLUSÃO: Apesar de concluirmos que o TV apresenta maior eficácia, novos estudos utilizando maior concentração, maior tempo de aplicação ou o uso seriado de MMC no tratamento da otite média com efusão devem ser realizados.

The effects of hyaluronic acid, epidermal growth factor, and mitomycin in an experimental model of acute traumatic tympanic membrane perforation

HYPOTHESIS

The goal of this study was to evaluate the effects of hyaluronic acid, epidermal growth factor, and mitomycin C on the healing of acute experimental traumatic perforations of the tympanic membrane.

BACKGROUND

Most acute perforations of the tympanic membrane heal spontaneously. However, some form of surgical treatment (i.e., myringoplasty) is needed for nonhealing perforations. Because the closure occurs by squamous epithelial migration, drugs that stimulate this regenerative process may aid in the closure of the perforation, obviating the need for more extensive treatments.

METHODS

Bilateral perforations of the tympanic membrane were created in 30 rats, divided into three groups (A, B, C). The perforations in the right ears were treated with hyaluronic acid, epidermal growth factor, or mitomycin C. Those in the left ears were left untreated for comparison. To examine the healing process in different periods, 5 animals were killed in each group at days 3, 5, 7, 9 and 14. The other 5 animals in each group were observed daily to determine the duration of perforation closures. Thirty surgical specimens (5 right sides from each group and all 15 left sides in all groups) were histopathologically examined for tympanic membrane thickness, fibroblastic reaction, neovascularization, and crust morphology.

RESULTS

Hyaluronic acid and epidermal growth factor applications significantly shortened the healing in acute experimental traumatic perforations of the tympanic membrane (p = 0.0432); however, the difference between them was not significant (p = 0.3160). On the other side, tympanic membrane perforations treated with topical mitomycin C showed no evidence of closure. There were no significant differences in the histologic parameters between the treated groups and their contralateral control ears.

CONCLUSION

Hyaluronic acid and epidermal growth factor accelerated the closure of acute tympanic membrane perforations in rats. This may make them clinically useful in augmenting the efficiency of conservative treatments of acute perforations of the tympanic membrane.

O comportamento clínico e histológico da pele do rato submetida ao uso tópico e injetável de Mitomicina C

OBJETIVO: A Mitomicina C é um quimioterápico que apresenta a capacidade de inibir fibroblastos in vitro. Esta característica a levou a ser usada experimentalmente em animais de laboratório e no ser humano, principalmente em oftalmologia, para inibir o processo cicatricial. Este trabalho visa acompanhar o processo de cicatrização de feridas cirúrgicas feitas em dorsos de ratos e tratadas topicamente com Mitomicina C, comparando-as com feridas no mesmo local, não tratadas. Propõe-se também a avaliar a resposta da pele quando injetada com concentrações diferentes do medicamento. FORMA DE ESTUDO: Experimental. MATERIAL E MÉTODO: Foram feitas, em 10 ratos, duas feridas cirúrgicas em seus dorsos. Uma delas foi tratada topicamente com Mitomicina C na diluição de 0,5 mg/ml por 5 minutos e outra não. O processo de cicatrização destas feridas foi acompanhado clinicamente. Posteriormente, os ratos foram sacrificados em períodos diferentes, e suas feridas estudadas histologicamente quanto ao grau de fibrose por dois anatomopatologistas. Posteriormente, três ratos foram submetidos a injeções intradérmicas com concentrações diferentes de Mitomicina C, e o comprometimento local foi avaliado clínica e histologicamente, sendo que apenas na concentração de 0,01mg/ml não se observou necrose tecidual. RESULTADOS: As feridas tratadas com Mitomicina C tiveram seu processo cicatricial retardado, com o desaparecimento das crostas locais 7 dias após o das feridas não tratadas. Ao exame histológico, observado separadamente por dois anatomopatologistas, observou-se no primeiro mês uma nítida diminuição do grau de fibrose nas feridas tratadas com Mitomicina C em relação às não tratadas. Este grau de fibrose se iguala, nas duas feridas, no terceiro mês. Quanto às diluições injetadas, notou-se clínica e histologicamente uma necrose tecidual proporcional ao grau de concentração (0,5; 0,1; e 0,05 mg/ml), que não foi observada na concentração de 0,01mg/ml. CONCLUSÃO: A Mitomicina C usada topicamente em feridas cirúrgicas em ratos retarda seu processo de cicatrização até a 4ª semana. Na 12ª semana este processo se equaliza. Quando usada intradermicamente, causa necrose tecidual apenas em concentrações elevadas. Estas características da Mitomicina C podem ser usadas, em otorrinolaringologia, como coadjuvante no tratamento de estenoses do meato acústico externo, imperfurações coanais, sinéquias nasais, estenoses laríngeas e quelóides.

Effect of exposure to mitomycin C on cultured tympanic membrane fibroblasts

OBJECTIVE

Recently, attempts have been made to prolong the patency of myringotomy site with topical use of mitomycin C (MMC). It has been shown that MMC inhibits mitosis and proliferation of ocular fibroblasts, however, there are no studies of MMC's effect on tympanic membrane fibroblasts. To investigate the effects of MMC on cultured human tympanic membrane fibroblasts and understand the cellular basis of MMC for maintain myringotomy patency, cultured fibroblasts were exposed to various concentrations of MMC for periods of 5-10 min.

METHODS

Effect of MMC on cultured fibroblasts was assessed by microscopic observation and cell viability test.

RESULTS

Dose-, time- dependent relationship of MMC on cultured fibroblasts was revealed. There was a significant difference between the inhibition effects of MMC at concentrations of 0.4 mg/ml and control following 5 and 10 min exposure intervals. Phase-contrast microscopy showed consistency with the antiproliferative effect of MMC at higher concentration.

CONCLUSIONS

Therefore, it would appear that intraoperative use of MMC could be effective in delaying the healing of the myringotomy site and extending the period of time for myringotomy patency.