Preapplication of mitomycin C for enhanced patency of myringotomy

A novel gel patch for minimally invasive repair of tympanic membrane perforations

OBJECTIVE

Evaluate the efficacy of a photocrosslinkable gel patch for repairing tympanic membrane (TM) perforations using a minimally invasive procedure.

METHODS

38 adult male chinchillas underwent bilateral TM perforation via CO₂ laser (n = 76 TMs). Eight weeks post-perforation induction, either a gel patch (n = 26) or EpiDisc (n = 12) was applied to the perforation through the ear canal. Perforation margins were not abraded prior to gel patch application in order to make the procedure minimally invasive. During the study, the application process was refined, and 9 of 26 gel-treated TMs received a second gel-patch augmentation. Perforations were observed for 14 weeks post-treatment to determine healing rates, after which animals were euthanized and their TMs and cochlea removed for histological analysis.

RESULTS

38 perforations (50%) persisted for 8 weeks without manipulation. Healing rates stabilized within three weeks post-treatment. Of the gel-treated TMs, 14 TMs healed after one application, 7 TMs healed after a second application, and 5 TMs did not heal, yielding an 81% total healing rate. Six of 12 EpiDisc-treated TMs healed (50%). There was no statistical difference (p = 0.06) in perforation size between gel-treated (25.1 ± 12.5% total TM area) and Epidisc-treated (36.4 ± 22.5). The largest perforation healed with gel patch was 60% total TM area. Histological analysis showed gel-treated TMs to have trilaminar regeneration with substantial lamina propria thickness. Gel-treated TMs had thickness of statistical equivalence to untreated TMs (47.1 ± 29.0 and 54.8 ± 12.1 μm, respectively (p = 0.40)). EpiDisc-treated TMs showed a cell monolayer of substantially less thickness (9.04 ± 6.26 μm, p < 0.05) than gel-treated TMs. No evidence of ototoxicity was present in cochlea from either gel patch or Epidisc treatment.

CONCLUSIONS

The gel is promising regarding thickness and trilaminar regenerated tissue, perhaps due to the biomechanical properties of the gel, and further refinements in the material and technique are anticipated to increase ease and efficacy of treatment while minimizing complications.

Safety and efficacy of Intraurethral Mitomycin C Hydrogel for prevention of post-traumatic anterior urethral stricture recurrence after internal urethrotomy

BACKGROUND

Evaluation of the safety and efficacy of intraurethral Mitomycin C (MMC) hydrogel for prevention of post-traumatic anterior urethral stricture recurrence after internal urethrotomy.

METHODS

A thermoresponsive hydrogel base consisting of 0.8 mg MMC with 1cc water and propylene glycol to PF-127 poloxamer was used in theater. 40 male patients with short, non-obliterated, urethral stricture were randomized into 2 groups: control and MMC. After internal urethrotomy, the MMC group patients received the MMC-Hydrogel while the others were just catheterized. Both groups had their catheters for at least 1 week. After surgery, they were followed up by means of medical history and physical examination, monitoring voiding patterns and retrograde urethrogram at 1 month, 6 months and 1 year after surgery.

RESULTS

40 male patients between 14 to 89 years old (Mean = 54.15) underwent internal urethrotomy. The average age for the control and MMC group was 54.55±21.25 and 53.75±24.75 respectively. In a comparison of age between the two groups, they were matched (P=0.574). Stricture length was 10.7±5.9 and 9.55±4.15 mm for the control and MMC group respectively. There were no statistically meaningful differences between the two groups (P=0.485). Fifteen patients had a history of one previous internal urethrotomy which in a comparison between the two groups meant there was no meaningful difference (P=0.327). During postoperative follow up, total urethral stricture recurrence happened in 12 patients: 10 patients (50%) in control group and 2 patients (10%) in MMC group. The difference was statistically significant (P=0.001). There were no significant complications associated with the MMC injection in our patients.

CONCLUSIONS

Based on our results, MMC Hydrogel may have an anti-fibrotic action preventing post-traumatic anterior urethral stricture recurrence with no side effects on pre-urethral tissue. Due to our study limitations, our follow up time and the small number of patients, our results were not conclusive and further studies will be needed with a longer follow up time.

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.

Efficacy of topical halofuginone in myringotomy patency

The objective of the study is to determine whether topical halofuginone (HF) application has an impact on prolonging the time for healing of myringotomy incision, and to investigate histopathologic effects of HF on tympanic membrane (TM) in rat model. Forty rats with normal eardrums were involved in this study. The study group and control group consisted of 30 and 10 rats, respectively. A posterior incision 1 mm in diameter was made on healthy eardrums of the rats. Following incision, gelfoam soaked with HF hydrobromide of 30 mg/dl was applied on the perforation in study group, whereas gelfoam soaked with isotonic saline was applied on the perforation in control group. On days 1, 3, 7, 10, 14, 18, 21, 24, 27, and 30, otoendoscopic evaluation of eardrums under general anesthesia was conducted and perforations were screened. A rat of each group was killed in control days and TMs were dissected to evaluate histopathological changes. The average times for patency of perforation in study and control groups were 21.43 and 7.50 days, respectively. The difference was found to be statistically significant (p < 0.05). Histopathological evaluation revealed that HF reduces hyalinisation and fibrosis in eardrum, when compared with the control group. In conclusion, HF significantly delays closure time of myringotomies in rat model. However, this delay may not be enough for recovery of otitis media with effusion.

Effect of Mitomycin C on Anterior Urethral Stricture Recurrence after Internal Urethrotomy

OBJECTIVES

Urethral stricture is one of the oldest known urologic diseases and remains a common problem with high morbidity. Internal urethrotomy refers to any procedure that opens the stricture by incising or ablating it transurethrally. The most common complication of internal urethrotomy is stricture recurrence. The curative success rate of internal urethrotomy is approximately 20%. Mitomycin C has antifibroblast and anticollagen properties and in sporadic reports of animal and clinical studies it has increased the success rate of trabeculectomy and myringotomy. This study evaluated the efficacy of mitomycin C in the prevention of anterior urethral stricture recurrence after internal urethrotomy.

PATIENTS AND METHODS

Forty male patients with anterior urethral strictures were randomized to undergo internal urethrotomy with or without urethral submucosal mitomycin C injection. Using general anaesthesia, the urethrotomy was performed under direct vision. Mitomycin C (0.1mg) was injected submucosally at the urethrotomy site in 20 patients. The patients were re-evaluated after 6 mo and the stricture recurrence rate was compared between the two groups (chi(2) analysis).

RESULTS

Urethral stricture recurred in 2 patients (10%) in the mitomycin C-treated group and in 10 patients (50%) in the other group. This difference in stricture recurrence between the two groups was statistically significant (p=0.006).

CONCLUSIONS

To our knowledge, this is the first prospective, randomized, clinical trial to evaluate the efficacy of mitomycin C application in internal urethrotomy. Submucosal injection of mitomycin C significantly reduced stricture recurrence after internal urethrotomy. Further investigations are warranted to confirm its efficacy and safety.

Behandlung von Trommelfellperforationen mit Fibringel

BACKGROUND

The goal of this study was to evaluate the effects of a fibrin gel on the healing of tympanic membrane perforation in rats.

METHODS

Prolonged tympanic membrane perforations in 12 rats were created by application of mitomycin C to the intact tympanic membranes followed by bilateral myringotomy. Repeated applications of a fibrin gel to the perforation site of one tympanic membrane were performed in each animal. Tympanic membranes were observed for a total of 8 weeks.

RESULTS

One perforation in each group was already patent at the end of the observation period. The mean healing period of the remaining tympanic membranes was found to be 16.7 days in the fibrin gel group and 19.6 days in the control group.

CONCLUSION

A fibrin sheet does not seem to promote the wound healing process of tympanic membranes. However, the sheet might serve as a drug-delivery system for growth factors in the treatment of tympanic membrane perforations, because of its biocompatibility.

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.

Time and Dose Effects of Mitomycin C on Extracellular Matrix Fibroblasts and Proteins

OBJECTIVES/HYPOTHESIS

The objective was to determine treatment dose and time-dependent effects of injected mitomycin C on extracellular matrix fibroblasts, collagen, and fibronectin, important mediators in the wound healing response, in a rat cutaneous wound model.

STUDY DESIGN

A prospective, controlled animal study.

METHODS

Forty rats were injected with three different doses (0.4, 2.3, and 5.0 mg/mL) of mitomycin C at three different wound sites with a fourth wound site receiving saline as a control. The rats were grouped to have their tissue harvested at five different dates ranging from 1 week to 8 weeks. After death, samples from the wound site underwent Western blot analysis for collagen and fibronectin and histological analysis measuring fibroblast apoptosis.

RESULTS

Over an 8-week period, collagen and fibronectin significantly decreased and fibroblast apoptosis significantly increased. No correlation was found between the injected dose of mitomycin C and either the extracellular matrix protein concentration or the rate of fibroblast apoptosis.

CONCLUSION

Mitomycin C demonstrated a long-term effect in a wound, inhibiting collagen and fibronectin production and inducing apoptosis. Use of mitomycin C in excess of 0.4 mg/mL did not alter protein concentrations or rate of apoptosis.

[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.

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.

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.

Effects of topical mitomycin on inner ear: a light and electron microscopic study

Providing maintenance of myringotomy patency without use of ventilation tubes in the treatment of secretory otitis media has been one of the important study areas. For this reason, laser and Mitomycin C (MMC) are used together in experimental studies. But there has been no ultrastructural studies concerning whether leakage of MMC to middle ear during application of this procedure has an ototoxic effect or not and if so, to what extent. In this study, we searched the ultrastructural changes which occurred in the middle ear by direct applications of MMC to the middle ear for different time durations. The study was carried out over thirty adult guinea pigs without ear diseases. Bilateral myringotomy was performed and MMC was applied only to the right middle ear of each guinea pig. The first group received MMC once for 10 minutes, the second group received it once for 20 minutes, and the third group took it each day for 10 minutes during a one week period. The left ears of the samples were accepted as the control group. On the 8th day, sacrification was carried out. After electron and light microscopy examination, significant changes in the inner ear were observed in the third group though no significant change was observed for the first and the second groups. As a result it was concluded that the application of MMC to the middle ear once for a short duration causes no toxic effect on the inner ear.