Quantitative results:
The tympanic bulla mucosa and tympanic membrane thicknesses of the experiment group and the control group were measured. These histological parameters are given in Table 1 and 2. The decrease in the minimum mucosal thickness of the tympanic bulla was evaluated as statistically significant (p=0.019). When the maximum and average thicknesses of the tympanic membrane were evaluated, the decrease in the experiment group was statistically significant (p=0.008, p=0.011).
Discussion
In the recent years, Mesna is being used in surgical procedures for tissue dissection because of its chemical properties.12 It is being used in the practice of otolaryngology, especially to open the thickness between the tympanic membrane and the middle ear mucosa that occurs in the adhesive otitis media and atelectatic tympanic membranes.8,13 Yılmaz et al conducted a study where they applied Mesna to the 42 ears of 39 patients diagnosed with retraction pockets fixed to the incudo stapedial joint, stapes or promontorium and adhesive otitis media.8 As a result they reported that the use of Mesna is safe and eases the surgery, increasing surgical success. Kalcioğlu et al reported in a retrospective study that the use of Mesna increases surgical success, decreasing the need for second-look surgery.13 We, in our clinic, usually use %20 Mesna in the surgery of adhesive otitis media. We administer Mesna from the non retracted region of the tympanic membrane or the antrum to the middle ear cavity. We usually use dental injectors and administer one dose. We wait approximately 4-6 minutes after administration.
When the studies in the literature are considered, it can be seen that different agents have been used to prevent the development of experimental cholesteatoma. In these studies, it has been reported that cyclophospamide, isotretinoin, hyaluronic acid and mitomicin – C have no inhibiting effect on the development of cholesteatoma, prednisolon, transretinoic acid, 5- fluorouracilin have been reported to stop the increase of cholesteatoma.6,14-18 In our study we administered Mesna to provide the inhibition of the development cholesteatoma that occurred with the intratympanic injection of propylene glycol. According to the histopathological evaluation we observed that Mesna decreases the development of cholesteatoma.
According to the theory of epithelial migration, propylene glycol causes the formation of cholesteatoma.4,17 However there is diversity amongs the studies regarding the prevalence of cholesteatoma formation and histopathological properties. In experimental studies it has been shown that proliferation of the epithelial basal layer of the tympanic membrane starts in the third week.19,20 In the sixth week, the prevalence of the cholesteatoma caused by %90 propylene glycol (%90) is %87.5.21 It has been shown in the tympanic bullas of the chinchilla type rats that a single application of %50 propylene glycol (%50) can form cholesteatoma after three weeks.4 According to the information in the literature, the concentration of the mucosal irritant used to form experimental cholesteatoma and the duration of use are important. Therefore diversity is observed between the studies. We used %50 propylene glycol in our study and sacrificed the rats 45 days after the first administration. The cholesteatoma prevalence seen in the control group of our study, %50, was evaluated to be in concordance with the studies in the literature (%33–90).5
In our animal model study the decreases of the tympanic membrane thickness and the tympanic bulla mucosal thickness seen in the histopathological images between the control group and the experiment group were evaluated to be statistically significant. It was observed in the histopathological images that the cholesteatoma were mainly located at the tympanic bulla. Melo et al showed in their experimental study that epidermal invasion occurred from the tympanic membrane to the tympanic bulla in the control group and study group.5
In a study conducted on Winstar rats in which the effect of intratympanic single dose Mesna on cholestatoma was investigated, it was emphasized that single dose intratympanic Mesna prevented the formation of cholestatoma.22 In our study, despite the intratympanic Mesna application applied for 4 times, no statistical significance was found, indicating that the formation of cholestatoma was completely prevented. However, in microscopic examination, it was determined that Mesna reduced the occurrence prevalence of cholesteatoma and fibrosis.
Conclusion
According to the histopahtological results of our study on the experimental cholesteatoma model created on rats, the intratympanic administration of Mesna had a decreasing effect on the prevalence of cholesteatoma.
Acknowledgments: We thank Dr. Pınar Ergen for performing histopathological examination.
Conflicts of Interest: The authors declare no conflict of interest
Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Table 1. Statistical analysis of groups according to the thickness of the tympanic membrane