Healing of tympanic membrane after myringotomy during Streptococcus pneumoniae otitis media. An otomicroscopic and histologic study in the rat

Excising or preserving perforation margins in endoscopic transtympanic cartilage myringoplasty does not affect surgical success

OBJECTIVE

To compare the outcome of endoscopic transtympanic cartilage myringoplasty with and without removal of perforation edges for repairing chronic perforations with mucosal chronic otitis media (COM).

STUDY DESIGN

Quasi-randomised clinical trial.

SETTING

Tertiary referral centre.

MATERIALS AND METHODS

Patients with chronic perforations and mucosal COM undergoing endoscopic transtympanic cartilage myringoplasty were allocated to a control group for whom the perforation edges were preserved (n = 40) and an intervention group for whom the edges were removed (n = 39). Mean operation time, graft success rate, mean scores of graft neovascularisation and epithelialisation, and hearing were compared between the groups at 4 weeks and/or 6 months postoperatively.

RESULTS

Graft success rate was 95% (38/40) in the control group and 97% (38/39) in the intervention group at 6 months postoperatively; the difference was not significant. Mean graft neovascularisation scores 4 weeks postoperatively were 2.52 ± 0.59 in the control group and 2.58 ± 0.55 in the intervention group; the difference was not significant. Mean graft epithelisation scores 4 weeks postoperatively were 1.48 ± 0.57 in the control group and 1.68 ± 0.51 in the intervention group; the difference was not significant and remained nonsignificant 6 months postoperatively (2.5 ± 0.55 vs. 2.76 ± 0.36). Audiological outcomes at 6 months did not differ between the groups.

CONCLUSION

Endoscopic, transtympanic cartilage underlay myringoplasty with preservation of the perforation margins did not affect graft neovascularisation, epithelialisation or success. Longer-term outcomes and risk of cholesteatoma require further study.

FGF2 and EGF for the Regeneration of Tympanic Membrane: A Systematic Review

Objective

A systematic review was conducted to compare the effectiveness and safety of fibroblast growth factor-2 (FGF2) and epidermal growth factor (EGF) for regeneration of the tympanic membrane (TM).

Methods

The PubMed database was searched for relevant studies. Experimental and clinical studies reporting acute and chronic TM perforations in relation to two healing outcomes (success rate and closure time) and complications were selected.

Results

A total of 47 studies were included. Five experimental studies showed closure rates of 55%-100% with FGF2 compared with 10%-62.5% in controls for acute perforations. Five experimental studies showed closure rates of 30.3%-100% with EGF and 3.6%-41% in controls for chronic perforations. Two experimental studies showed closure rates of 31.6% or 85.7% with FGF2 and 15.8% or 100% with EGF. Nine clinical studies of acute large perforations showed closure rates of 91.4%-100% with FGF2 or EGF. Two clinical studies showed similar closure rates between groups treated with FGF2 and EGF. Seven clinical studies showed closure rates of 88.9%-100% within 3 months and 58%-66% within 12 months using FGF2 in repair of chronic perforations, but only one study showed a significantly higher closure rate in the saline group compared with the FGF2 group (71.4% vs. 57.5%, respectively, P = 0.547). In addition, three experimental studies showed no ototoxicity associated with FGF2 or EGF. No middle ear cholesteatoma or epithelial pearls were reported, except in one experimental study and one clinical study, respectively.

Conclusions

FGF2 and EGF showed good effects and reliable safety for the regeneration of TM. In addition, EGF was better for the regeneration of acute perforations, while FGF2 combined with biological scaffolds was superior to EGF for chronic perforations, but was associated with high rates of reperforation over time. Further studies are required to determine whether EGF or FGF2 is better for TM regeneration.

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.

Short-Wave Infrared Fluorescence Chemical Sensor for Detection of Otitis Media

Otitis media (OM) or middle ear infection is one of the most common diseases in young children around the world. The diagnosis of OM is currently performed using an otoscope to detect middle ear fluid and inflammatory changes manifested in the tympanic membrane. However, conventional otoscopy cannot visualize across the tympanic membrane or sample middle ear fluid. This can lead to low diagnostic certainty and overdiagnoses of OM. To improve the diagnosis of OM, we have developed a short-wave infrared (SWIR) otoscope in combination with a protease-cleavable biosensor, 6QC-ICG, which can facilitate the detection of inflammatory proteases in the middle ear with an increase in contrast. 6QC-ICG is a fluorescently quenched probe, which is activated in the presence of cysteine cathepsin proteases that are up-regulated in inflammatory immune cells. Using a preclinical model and custom-built SWIR otomicroscope in this proof-of-concept study, we successfully demonstrated the feasibility of robustly distinguishing inflamed ears from controls (p = 0.0006). The inflamed ears showed an overall signal-to-background ratio of 2.0 with a mean fluorescence of 81 ± 17 AU, while the control ear exhibited a mean fluorescence of 41 ± 11 AU. We envision that these fluorescently quenched probes in conjunction with SWIR imaging tools have the potential to be used as an alternate/adjunct tool for objective diagnosis of OM.

Identification of early inflammatory changes in the tympanic membrane with Raman spectroscopy

The tympanic membrane (TM) is a dynamic structure that separates the middle ear from the external auditory canal. It is also integral for the transmission of sound waves. In this study, we demonstrate the feasibility of using Raman spectroscopy to identify early chemical changes resulting from inflammation in the TM that can serve as an indicator of acute otitis media. Bacterial lipopolysaccharide (LPS) was injected trans-tympanicaly in a murine model. Presence of inflammatory response was assessed with binocular microscopy, confirmed with histopathology and immunofluorescence staining. Successful discrimination suggesting spectral differences among the control and LPS treated groups was achieved using principal component analysis. Raman imaging revealed major differences in collagen distribution and nucleic acid content. Image segmentation analysis on the trichrome stained tissue sections was performed to corroborate the Raman spectra. The spectral co-localization study suggests changes in the expression of collagen IV specific signals in LPS treated samples. The overall findings of the study support prospective application of RS in the diagnosis and therapeutic monitoring of otitis media.

Animal models of acute otitis media - A review with practical implications for laboratory research

Considerable animal research has focused on developing new strategies for the prevention and treatment of acute otitis media (AOM). Several experimental models of AOM have thus been developed. A PubMed search of the English literature was conducted from 1975 to July 2016 using the search terms "animal model" and "otitis media" from which 91 published studies were included for analysis, yielding 123 animal models. The rat, mouse and chinchilla are the preferred animals for experimental AOM models with their individual advantages and disadvantages. The most common pathogens used to create AOM are Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Streptococcus pneumoniae (types 3, 23 and 6A) and non-typeable Haemophilus influenzae (NTHi) are best options for inoculation into rat and mouse models. Adding viral pathogens such as RSV and Influenza A virus, along with creating ET dysfunction, are useful adjuncts in animal models of AOM. Antibiotic prophylaxis may interfere with the inflammatory response without a significant reduction in animal mortality.

Morphological changes in the tympanic membrane associated with Haemophilus influenzae-induced acute otitis media in the chinchilla

OBJECTIVE

The tympanic membrane (TM) couples sound waves entering the outer ear canal to mechanical vibrations of the ossicular chain in the middle ear. During acute otitis media (AOM), dynamic structural changes in the TM can occur, which potentially affect sound transmission. It has remained unclear whether TM changes contribute significantly to the conductive hearing loss associated with human AOM. Studies that systematically and quantitatively assess the impact of morphological and mechanical characteristics of the TM on hearing in animal models of AOM have been few in number and lack detail. Our current study focused on the identification of quantitative morphological changes in the TM of the adult chinchilla.

METHOD

AOM was produced by transbullar injection of the nontypeable (acapsular) Haemophilus influenzae strain 86-028NP into two treatment groups of chinchillas: one 4 days (4D) post bacterial challenge, and a second treatment group after 8 days (8D) post challenge. Structure and thickness were examined histologically at nine locations over the TM in untreated controls and in animals from both AOM treatment groups.

RESULTS

TM thickness was found to have increased significantly (110-150%) at all measured locations of H. influenzae-infected ears when compared with uninfected (normal) TMs at 4D post bacterial challenge. Cellular proliferation and infiltration in the outer epithelial layer were primary contributors to this thickening. In ears infected for 8D, the TM was substantially thicker, a 200-300% increase from uninfected control values, due to edema and cell proliferation in both the outer and inner epithelial layers. In both 4D and 8D ears, thickening of the TM was more prominent in the superior-anterior quadrant.

CONCLUSION

This study provides unequivocal structural evidence that significant TM thickness increases are associated with AOM induced by a well characterized H. influenzae human clinical isolate of low passage number. These and additional thickness data from early and later stages in middle ear infection will be used to derive the mechanical properties of the TM in a future study from our laboratory.

Role of c-Jun N-terminal protein kinase 1/2 (JNK1/2) in macrophage-mediated MMP-9 production in response to Moraxella catarrhalis lipooligosaccharide (LOS)

Moraxella catarrhalis is a Gram negative bacterium and a leading causative agent of otitis media (OM) in children. Recent reports have provided strong evidence for the presence of high levels of matrix metalloproteinase (MMPs) in effusion fluids from children suffering with OM, however, the precise mechanisms by which MMPs are generated are currently unknown. We hypothesized that MMPs are secreted from macrophages in the presence of M. catarrhalis lipooligosaccharide (LOS). In this report, we demonstrate that in vitro stimulation of murine macrophage RAW 264.7 cells with LOS leads to secretion of MMP-9 as determined by ELISA and zymogram assays. We have also shown that inhibition of ERK1/2 and p38 kinase completely blocked LOS induced MMP-9 production. In contrast, inhibition of JNK1/2 by the specific inhibitor SP600125 actually increased the level of expression and production of MMP-9 at both mRNA and protein levels, respectively by almost five fold. This latter result was confirmed by knocking down JNK1/2 using siRNA. Similar results have been observed in murine bone marrow derived macrophages in vitro. In contrast to and in parallel with the LOS-induced increased levels of MMP-9 in the presence of SP600125, we found a corresponding dose-dependent inhibition of TIMP-1 (tissue inhibitor of matrix metalloproteinase-1) secretion. Results of subsequent in vitro studies provided evidence that when JNK1/2 was inhibited prior to stimulation with LOS, it significantly increased both the extent of macrophage cell migration and invasion compared to control cells or cells treated with LOS alone. The results of these studies contribute to an increased understanding of the underlying pathophysiology of OM with effusion in children.

Rates of tympanic membrane closure in double-tympanocentesis studies

BACKGROUND

Data on the outcome of tympanic membrane (TM) closure after tympanocentesis in acute otitis media (AOM) patients is limited.

OBJECTIVES

To analyze the dynamics of TM perforation closure after 1 or 2 tympanocentesis procedures performed at diagnosis and during AOM treatment.

PATIENTS AND METHODS

Study population included 113 children enrolled in 4 double-tympanocentesis studies. Only the files of patients whose first and second examination were performed by the same 2 otorhinolaryngologists were analyzed. Middle ear fluid (MEF) was cultured on day 1 and days 4-6, the latter only in initially culture-positive patients. Patients were also examined on days 11-14 and followed until days 22-28.

RESULTS

Ninety-three (82%) patients underwent tympanocentesis on days 4-6; 103 (91%) and 95 (84%) were evaluable on days 11-14 and 22-28, respectively. One hundred seventy-three ears underwent tympanocentesis on day 1 and 139 on days 4-6. Ninety-seven (86%) patients had positive MEF cultures. One hundred fifty-three (88%) tympanocentesis procedures performed at enrollment were closed on days 4-6. No differences were recorded in the closure rates as function of patient age, previous AOM history, MEF culture positivity, pathogens isolated at enrollment, and pathogen eradication on days 4-6. The 20 eardrums still open on days 4-6 were closed on days 11-14. Eleven (9%) of the evaluable ears tapped on days 4-6 were not closed on days 11-14 and 9 of 10 were closed on days 22-28.

CONCLUSIONS

TM perforation closed in most cases within a few days regardless of patient and disease characteristics, and 2 consecutive tympanocentesis procedures performed at short-time intervals are associated with good TM closure rates.

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.

First forty-eight hours of developing otitis media: an experimental study

The early inflammatory changes in the tympanic membrane were explored in 2 rat models. Acute otitis media was induced by instillation of Streptococcus pneumoniae type 3 into the middle ear cavity, and otitis media with effusion was induced by blockage of the eustachian tube. Otomicroscopic examination was performed before the rats were painlessly sacrificed at 3, 6, 9, 12, 18, 24, or 48 hours after initiation of the otitis media conditions. The tympanic membrane was studied by light and electron microscopy. Both acute otitis media and otitis media with effusion caused early inflammatory changes of the tympanic membrane, and the pars flaccida was the portion that reacted first. The inflammatory alterations were most pronounced in the acute otitis media model. The course of inflammation showed a bimodal pattern with an early deposition of a filamentous material with a band pattern, typical of fibrin. Despite a fluid-filled middle ear cavity, the inflammatory changes in the otitis media with effusion model were moderate, as was consistent with the clinical appearance of the tympanic membrane.

Myringotomy delays the tympanic membrane recovery in acute otitis media: a study in the rat model

BACKGROUND/HYPOTHESIS

Acute otitis media is a major cause of visits to pediatric health care providers. Myringotomy in uncomplicated acute otitis media is debatable today. The study addressed this problem through the otomicroscopic and histopathological observations of the events occurring in the tympanic membrane during the first week after myringotomy.

STUDY DESIGN

Randomized study in an experimental animal model.

METHODS

Under anesthesia, the left middle ear of 36 Sprague-Dawley rats was inoculated with Streptococcus pneumoniae type 3. Forty-eight hours later, at day 0, four animals were immediately killed and the remaining animals were randomly assigned into a myringotomy group (n = 16, myringotomy on the left ear) and a non-myringotomy group (n = 16, otomicroscopy without myringotomy). Otomicroscopy and killings were performed in series of four animals from each group at days 1, 2, 4, and 7 after myringotomy. Tympanic membranes were collected after fixation and processed for light and electron microscopy.

RESULTS

All inoculated ears showed a manifest acute otitis media at day 0. An intense infiltration by inflammatory cells and edema distorted severely the tympanic membrane structure. These findings decreased the following days. However, inflammation as evaluated by the thickness and the cytoarchitecture of the tympanic membrane layers, recovered significantly faster in the membranes in the non-myringotomy group. At day 7, all tympanic membranes in the myringotomy group were closed by a hypertrophic keratinizing epithelium and a remodeling connective tissue layer, whereas the animals in the non-myringotomy group had a residual edema in the lamina propria.

CONCLUSIONS

The present infectious model induced an intense inflammatory reaction within the entire structure of the tympanic membrane. Myringotomy provoked a delayed recovery from the inflammatory process within the tympanic membrane. Therefore, if applicable to human conditions, the use of myringotomy in the management of acute otitis media should be restricted to selected cases of acute otitis media.

Early structural tympanic membrane reactions to myringotomy: a study in an acute otitis media model

Myringotomy (Myr) is one of the most frequently performed surgical procedures in children. However, events occurring in the early phases, i.e. a matter of hours, following Myr in the acute otitis media (AOM) model have not been described. The aim of the present study was to evaluate the early otomicroscopic and histopathologic reactions of the tympanic membrane (TM) after Myr during the course of AOM (AOM-Myr). The left tympanic bulla from 36 healthy Sprague-Dawley rats was inoculated with Streptococcus pneumoniae type 3. Forty-eight h later, at Day 0, 4 randomized animals were immediately sacrificed and the remaining animals were treated with bilateral Myr. Otomicroscopy and sacrifices were performed in series of 4 animals at 3, 6, 9, 12, 24 and 48 h, and 4 and 7 days. The AOM-Myr TMs were compared to non-infected Myr TMs (non-AOM-Myr). The TMs were then dissected free and routinely processed for light and electron microscopy. AOM developed in all inoculated ears at Day 0. In the pars tensa of the AOM-Myr TMs the reaction of the keratinocyte layer of the perforation border was already evident at 6 h. The lamina propria exhibited a strong inflammatory reaction, which became more organized from 12 h onwards. At Day 4 the perforations were closed in three-quarters of cases. At Day 7 all perforations were healed with a distorted scar. In the non-AOM Myr TMs a strong degranulation of mast cells and edema were found in the pars flaccida at 6 h. A keratin spur at the perforation border was not seen until 24 h. All perforations were patent on Day 7 and myringosclerotic deposits were abundant in these TMs. The infected TMs regenerated faster and closed their perforations at an earlier stage. These findings favor the hypothesis that there is a low risk of chronic perforations when myringotomizing AOM TMs.

Quantitation and prevalence of tympanosclerosis in a pediatric otolaryngology clinic

OBJECTIVE

To determine the incidence and prevalence of tympanosclerosis (TS) in patients seen in a pediatric otolaryngology clinic.

DESIGN

Prospective observational study.

SETTING

Tertiary care, ambulatory care clinic.

PATIENTS AND OTHER PARTICIPANTS

We conducted a prospective observational study to determine the incidence of TS in 218 patients seen consecutively in a pediatric otolaryngology clinic for otologic and nonotologic reasons. The patient age range was 3 weeks to 30 years; 63% were male and 37% female. Of the 218 patients, 37% (81) had undergone bilateral myringotomy and tube placement (BM&T), and 35% (21) of the 81 showed signs of TS; 63% (137) of the 218 patients had no history of otologic surgery, but 12% (15) of the 137 showed signs of TS.

METHOD

The area of the tympanic membrane affected by TS was determined by otoscopy performed by one viewer, who drew the otoscopic findings on a standardized tympanic membrane template. The area of TS was quantified in terms of percentages by digital image analysis of the scaled drawings.

RESULTS

There was a range of 0.5-59.9% involvement of the tympanic membrane with TS, with the median percentage of involvement being 4.95%. There was an increased percentage of TS with repeat BM&T.

CONCLUSION

This observational study shows that patients who have had BM&T have a higher incidence of TS than those who have not had the surgery. However our findings also show that 38% of the patients in this study who had TS had never undergone BM&T.

Synthetic polysaccharide type 3-related di-, tri-, and tetrasaccharide-CRM(197) conjugates induce protection against Streptococcus pneumoniae type 3 in mice

Di-, tri-, and tetrasaccharides, synthesized according to the chemical structure of pneumococcal polysaccharide type 3 (PS3), were coupled to the cross-reactive material (CRM(197)) of modified diphtheria toxin in different molar carbohydrate/protein ratios using the squarate coupling method. To study protective immunity, female BALB/c mice were subcutaneously immunized twice (with a 3-week interval) using the amount of conjugates corresponding to 2.5 microg of oligosaccharide per mouse. The conjugates evoked PS3 binding immunoglobulin G antibodies that lasted for at least 7 weeks after the booster. Immunogenicity was not influenced by the carbohydrate/protein ratio. All mice with PS3-specific antibodies survived the intraperitoneal challenge with Streptococcus pneumoniae type 3. Therefore, synthetic oligosaccharide-protein conjugates might have potential as vaccines.

Natural pathogens of laboratory mice, rats, and rabbits and their effects on research

Laboratory mice, rats, and rabbits may harbor a variety of viral, bacterial, parasitic, and fungal agents. Frequently, these organisms cause no overt signs of disease. However, many of the natural pathogens of these laboratory animals may alter host physiology, rendering the host unsuitable for many experimental uses. While the number and prevalence of these pathogens have declined considerably, many still turn up in laboratory animals and represent unwanted variables in research. Investigators using mice, rats, and rabbits in biomedical experimentation should be aware of the profound effects that many of these agents can have on research.

Myringotomy: a prerequisite for the development of myringosclerosis?

Streptococcus pneumoniae was inoculated into the left middle-ear cavity in two groups of rats, resulting in purulent otitis media. After 3 days, one group of infected animals and a third group of noninfected animals were subjected to left-sided myringotomy. The tympanic membranes were examined both otomicroscopically and histologically 1 and 3 months later. On otomicroscopic examination the noninfected myringotomized animals had developed extensive myringosclerotic lesions, whereas only minimal sclerotic deposits were noted in the myringotomized animals with acute otitis media (AOM). On histologic examination both the noninfected myringotomized animals and the myringotomized animals with AOM were similar in the frequency and extension of sclerotic lesions in the tympanic membrane. The nonmyringotomized rats with AOM were free of sclerotic lesions, except for minor changes found in one animal.