Histology of the tympanic perforation and the replacement membrane

Tracking cell layer contribution during repair of the tympanic membrane

The tympanic membrane (i.e. eardrum) sits at the interface between the middle and external ear. The tympanic membrane is composed of three layers: an outer ectoderm-derived layer, a middle neural crest-derived fibroblast layer with contribution from the mesoderm-derived vasculature, and an inner endoderm-derived mucosal layer. These layers form a thin sandwich that is often perforated following trauma, pressure changes or middle ear inflammation. During healing, cells need to bridge the perforation in the absence of an initial scaffold. Here, we assessed the contribution, timing and interaction of the different layers during membrane repair by using markers and reporter mice. We showed that the ectodermal layer is retracted after perforation, before proliferating away from the wound edge, with keratin 5 basal cells migrating over the hole to bridge the gap. The mesenchymal and mucosal layers then used this scaffold to complete the repair, followed by advancement of the vasculature. Finally, differentiation of the epithelium led to formation of a scab. Our results reveal the dynamics and interconnections between the embryonic germ layers during repair and highlight how defects might occur.

The Effectiveness of bFGF in the Treatment of Tympanic Membrane Perforations: A Systematic Review and Meta-Analysis

Objective:

To investigate the effectiveness of basic fibroblast growth factor (bFGF) versus placebo or no intervention in the treatment of tympanic membrane (TM) perforations from randomized controlled trials (RCTs), prospective and retrospective studies.

Data Sources:

PubMed, EMBASE, and Cochrane databases were screened from their inceptions to June 2019.

Study Selection:

Inclusion criteria: 1) English language; 2) observational (retrospective or prospective) or treatment (RCT) studies; 3) reported the outcomes on the application of bFGF in adult or pediatric population. Exclusion criteria: 1) studies without a control group; 2) animal studies, in vitro studies, review studies, and case reports.

Data Extraction:

Number of patients, cause of TM perforation, perforation size, treatment, mean age, follow-up time, sex, closure rate, healing time, mean air-bone gap improvement.

Data Synthesis:

A total of 14 studies were included, including seven RCTs and seven non-RCTs with a total of 1,072 participants. The odds ratio for closure rate of bFGF treatment was 7.33 (95% confidence interval [CI], 4.65 to 11.53; p < 0.01; I² = 44%) and the standardized mean difference (SMD) for healing time was –5.89 (95% CI: –7.85 to –3.93, p < 0.01, I² = 98%), suggesting bFGF application has a significant effect on closure of TM perforations. However, no significant change in hearing (SMD: 0.08, 95% CI: –0.11 to 0.27, p = 0.39, I² = 0%) was seen as a result of bFGF treatment.

Conclusions:

Our meta-analysis has revealed that the application of bFGF can significantly enhance the closure rate as well as shorten the healing time for TM perforations. In terms of hearing, there is as yet no evidence that bFGF has a significant effect. Given its ease, availability, and safety, bFGF can be used effectively for TM repair.

The Long-Term Stability of Fat-Graft Myringoplasty in the Closure of Tympanic Membrane Perforations and Hearing Restoration

BACKGROUND/AIMS

This study was conducted to evaluate the long-term stability of fat-graft myringoplasty (FGM) for chronic tympanic membrane perforations, analyzing the perforation closure rate and re-gained hearing outcome with respect to the size and location of the perforations.

METHODS

Between August 2007 and June 2018, a total of 193 patients who underwent FGM due to chronic tympanic membrane perforation at a tertiary referral center were enrolled and analyzed.

RESULTS

The mean follow-up was 14.6 months (range 6-39). The complete perforation closure rate after FGM was 89.6%, with no statistical difference among the perforation size groups. The mean postoperative air-bone gap (ABG) was 11.0 dB and mean ABG improvement was 4.9 dB.

CONCLUSION

Our FGM technique had a favorable tympanic closure rate for small to large perforations, and yielded relatively good hearing improvement in the mid-size perforation cases over long-term follow-up periods. According to the topographic evaluation of FGM, this procedure resulted in a reliable perforation closure rate and audiological results regardless of the perforation site.

Full-thickness cartilage graft myringoplasty combined with topical application of bFGF for repair of perforations with extensive epithelialization

OBJECTIVE

The objective of this study is to evaluate the long term outcome of endoscope full-thickness cartilage graft myringoplasty combined with topical application of basic fibroblast growth factor (bFGF) for repair of perforations with extensive epithelialization.

MATERIALS AND METHODS

In total, 65 perforations with extensive epithelialization of edges were divided into the endoscope full-thickness cartilage graft myringoplasty with (bFGF treatment group) and without topical application of bFGF (control group) groups. The outcomes were evaluated in terms of the hearing gain and graft success rate at 12 and 24 months post-surgery.

RESULTS

All patients were followed up at 24 months. Graft success rate was 97.2% in postoperative 12th month and 97.2% in postoperative 24th month in the bFGF group, whereas graft success rate was 100.0% in postoperative 12th month and 86.2% in postoperative 24th month in the control group. The re-perforation wasn't evident in any patients in the bFGF group while re-perforation in 4 (13.8%) patients in the control group, with statistical significance (P = 0.023).Comparing the two groups, there was no difference regardless of in preoperative or postoperative 12 months mean ABG or ABG closure. CT images revealed the well pneumatized middle ear and mastoid cells at postoperative 24th months in both groups, no middle ear cholesteatoma and keratin pearls were found during the period of follow up.

CONCLUSIONS

The cartilage-perichondrium double graft combined with bFGF are a feasible and effective method for providing the long-term graft success rate of the perforations with extensive epithelialization.

The short- and long-term adverse effects of FGF-2 on tympanic membrane perforations

SUMMARY

The objective of this study was to investigate the short- and long-term adverse effects of fibroblast growth factor-2 treatment of tympanic membrane perforations. A total of 134 patients with traumatic tympanic membrane perforations were randomly divided into two groups: an observational group and a fibroblast growth factor-2 treatment group. The closure rate, closure time and principal side-effects were compared between the groups at 6 and 12 months. At 6 months, 131 patients were examined to determine healing outcomes and short-term side-effects. The total closure rate differed significantly between the fibroblast growth factor-2 and observational groups (95.5% vs 73.4, p #x003C; 0.01). The fibroblast growth factor-treated group exhibited a significantly shorter closure time than the observational group (11.9±3.1 days vs 52.6 ± 18.1 days, p = 0.00). Three patients with secondary otitis media with effusion, and three with reperforations, were noted in the fibroblast growth factor-2 group. We additionally performed long-term follow-up on 89.1% of the patients in the observational group and 92.5% of the patients in the fibroblast growth factor-2 group; follow-up was performed 16-42 months after perforation closure. Only a small perforation of the pars flaccida developed in the fibroblast growth factor-2 group. No middle ear cholesteatoma was noted in either group. This study suggests that the topical application of fibroblast growth factor-2 to human traumatic tympanic membranes is safe. Otorrhoea was the most common short-term side-effect; other less common side-effects included otitis media with effusion and reperforation. No serious long-term side-effects were found.

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.

Gelatin hydrogel with basic fibroblast growth factor for tympanic membrane regeneration

HYPOTHESIS

In this developmental research study that aimed to develop tympanic membrane regeneration therapy, we devised a method of sustained bFGF formulation release using gelatin hydrogel in a guinea pig eardrum perforation model.

BACKGROUND

Basic fibroblast growth factor (bFGF) can promote perforation closure. In addition, several studies of bFGF formulations have used gelatin hydrogel-bFGF coupled electrostatically to a gelatin polymer. BFGF is released gradually as a result of degradation of the gelatin polymer, and studies have shown that the long-term pharmacologic effects of bFGF can be maintained.

METHODS

Using a CO(2) laser, total tympanic membrane perforations were created in 24 guinea pig ears and divided into 3 groups: the bFGF-gelatin hydrogel group(n = 8), the saline-gelatin hydrogel group (n = 8), and the control group (n = 8). Either a bFGF formulation or saline was impregnated into gelatin hydrogen and implanted into the perforated tympanic membrane.

RESULTS

All ear drums of the control group showed large perforations at even the 30th postoperative day. The perforation persisted in 3 of 8 ears in the saline-gelatin hydrogel group, and the tympanic membranes that had achieved closure were thinned, whereas all ears in the bFGF-gelatin hydrogel group achieved closure of the perforation. In the ears in which a normal tympanic membrane had regenerated, histologic observation with hematoxylin and eosin staining revealed that, although mucosal and epithelial layer regeneration had occurred in the saline-gelatin hydrogel group, the bFGF-gelatin hydrogel group showed regeneration of the fibrous layer in addition to the other 2 layers.

CONCLUSION

These data suggest that hydrogel impregnated with bFGF induces regeneration of the tympanic membrane and can conservatively treat tympanic membrane perforation.

Clinical analysis of secondary acquired cholesteatoma

OBJECTIVE

This study aimed to analyze the clinical features of patients who underwent surgery for secondary acquired cholesteatoma (SAC).

MATERIALS AND METHODS

The subjects were 30 patients who underwent surgery for SAC in 30 ears. We investigated the age distribution, sex, tympanic membrane (TM) findings, temporal bone pneumatization, morphology of TM epidermis invasion, extent of cholesteatoma invasion, ossicular erosion, surgical methods and surgical results.

RESULTS

There were 10 males (33.3%) and 20 females (66.6%), with a mean age 54.9 years. The TM perforation was medium-sized or larger in 27 ears (90%). Temporal bone pneumatization was poor or bad in 90% (18/20) of the evaluated ears. The cholesteatoma invaded from the malleus manubrium to the promontory in 23 ears (76.7%). There were no patients in whom the cholesteatoma invaded the antrum or mastoid. The ossicles were affected in 19 ears (63.3%). Ossiculoplasty with a columella on the stapes was the most frequent procedure, performed for 16 ears (53.3%). There were no hearing results with a postoperative air-bone gap of more than 31 dB.

CONCLUSIONS

Although SAC is rare, it is important for the clinician to keep this type of cholesteatoma in mind.

Can myringoplasty close the air-bone gap?

OBJECTIVE

The aim of this study is to evaluate whether closure of a tympanic membrane perforation with an intact ossicular chain results in a closure of the air-bone gap.

STUDY DESIGN

Prospectively collected data from 154 patients undergoing temporalis fascia myringoplasty for chronic otitis media simplex were identified.

SETTING

Tertiary referral center.

PATIENTS

Between 2001 and 2009, overall, 106 patients with a central tympanic membrane perforation and, an intact ossicular chain were further analyzed.

INTERVENTIONS

All patients underwent myringoplasty using temporalis fascia in an underlay technique.

MAIN OUTCOME MEASURES

Comparison of the preoperative and postoperative hearing results in patients undergoing myringoplasty for chronic otitis media simplex.

RESULTS

The mean postoperative air-bone gap (ABG) was 8.2 dB for the frequencies 0.5 to 4 kHz. Eighty-three patients (78%) showed postoperatively a mean ABG of 10 dB or lower. The ABG difference (improvement) was statistically significant for each single frequency (0.5, 1, 2, 3, and 4 kHz) (p < 0.0001). There is a linear correlation between the preoperative tympanic membrane perforation size and the postoperative ABG (p = 0.0017) for the frequencies 0.5 to 4 kHz. No statistical significant correlation was seen between the state of the middle-ear mucosa, temporal bone pneumatization, tympanometric middle-ear/mastoid volume, and the postoperative ABG.

CONCLUSION

Complete ABG closure by myringoplasty could be achieved in only approximately 20% of the cases. 80% respectively presented with a mean residual ABG of 8 dB. We found a significant linear correlation between the preoperative size of the tympanic membrane perforation and the postoperative ABG, whereas mastoid volume, temporal bone pneumatization, and the condition of the mucosa did not affect the outcome.

Tissue engineering of the tympanic membrane

Tympanic membrane (TM) perforations are common, with current treatments for chronic perforations involving surgery, using various graft materials, from autologous cartilage or fascia through to paper patch. Recent research developments in this field have begun applying the principles of tissue engineering, with appropriate scaffolds, cells, and bioactive molecules (BMs). This has revolutionized the therapeutic approach due to the availability of a wide range of materials with appropriate compatibility and mechanical properties to regenerate the membrane acoustics and may also represent a paradigm shift in the management of TM perforations in an outpatient setting without surgery. However, many factors need to be considered in the fabrication of a bioengineered TM. This review discusses the issues associated with current treatment and examines TM wound healing relevant to the construction of a bioengineered TM. It also describes the tissue-engineering approach to TM regeneration by summarizing currently used scaffolds, BMs, and cells in TM wound healing. Finally, it considers the design of scaffolds, delivery of BMs, and cell engraftment toward potential clinical application.

The impact of platelet-derived growth factor on closure of chronic tympanic membrane perforations: a randomized, double-blind, placebo-controlled study

OBJECTIVE

Patients with tympanic membrane (TM) perforations often have infections, and repetitive topical treatment may be required. These infections can be prevented by permanent closure of the TM perforation. Different surgical treatment options have been described, but noninvasive techniques may be preferred as they carry less risk than surgery. One noninvasive approach is to induce wound healing by application of growth factors. The effect and clinical use of applying topical platelet-derived growth factor (PDGF) for decrease of size and closure of chronic TM perforations is evaluated.

STUDY DESIGN

Prospective, randomized, placebo-controlled, double-blind study.

SETTING

Tertiary referral center.

PATIENTS

Twenty patients with chronic suppurative otitis media without cholesteatoma for more than 3 months.

INTERVENTION

Topical treatment with PDGF or placebo applied weekly to the TM for 6 weeks.

MAIN OUTCOME MEASURES

Success rate, defined as a reduction of perforation size of 50% or more to determine relative changes of the perforation size; effect of initial size and location of TM perforation on success rate; and air and bone conduction thresholds to determine air-bone gap measured before treatment.

RESULTS

Randomization made matching pretreatment perforation size of the 2 study groups impossible, and the initial rate perforation/TM was significantly smaller in the PDGF group. No difference between the 2 groups was found for perforation/TM less than 10%. However, success rate did not differ significantly between the 2 groups (power = 0.8), and the effect of PDGF was found to be small (-2%; standard deviation, ±49%). Initial size and position of the TM perforation were not significant factors determining success. Mean air-bone gap for the frequencies of 0.5, 1, 2, and 4 kHz was 22.5 dB.

CONCLUSION

The topical application of PDGF as an office treatment for chronic otitis media is not a favorable alternative to surgery.

Basic fibroblast growth factor combined with atelocollagen for closing chronic tympanic membrane perforations in 87 patients

OBJECTIVE

To present the clinical results of closing chronic tympanic membrane (TM) perforations using basic fibroblast growth factor (bFGF) combined with an atelocollagen/silicone bilayer membrane patch.

STUDY DESIGN

Closure of TM perforations in 87 patients was attempted using bFGF, which is thought to promote the regeneration of TM tissues by facilitating the growth of fibroblasts and collagen fibers.

METHODS

Under an operating microscope, the margin of the perforation was trimmed, and a piece of an atelocollagen/silicone bilayer membrane was placed in the perforation with the silicon layer facing outward and then infiltrated with 0.1 ml of trafermin. Data obtained from patient records included patient age, perforation size, and duration of treatment, with a focus on hearing improvement and complete TM closure.

RESULTS

The mean perforation size before treatment was 14.4%. Complete closure of the TM perforation was achieved in 80 patients (92.0%), whereas pinholes remained in 5 patients (8.7%), and small perforations were observed in 2 patients (2.3%). In the patients with complete closure, the TM perforations closed after an average 1.8 treatments, and hearing improved by 13.6 dB.

CONCLUSION

This study demonstrated that bFGF combined with atelocollagen is effective for the conservative treatment of TM perforation.

Utilization of fresh human tympanic membranes for structural analysis and cytokeratin immunocytochemistry implementing resin techniques

CONCLUSIONS

The results of this study have demonstrated for the first time that tympanic membrane (TM) structure is preserved following removal of fresh, normal tissue from patients undergoing surgery. Greater clarity has been demonstrated using resin sections than in previous studies on paraffin sections. Of particular note, cytokeratin (CK) immunocytochemistry was successfully performed on resin sections, which has not been previously reported. This may have potential applications for future work involving tissues that express CKs.

OBJECTIVES

To analyse the structure of normal, fresh human TM specimens after surgical removal and to evaluate their CK immunocytochemistry using resin techniques, neither of which have been demonstrated previously.

MATERIAL AND METHODS

Seven TM specimens were removed during surgery and then preserved in a modified Karnovsky's fixative. Semi-thin and thin sections were examined by means of light and electron microscopy, respectively. For comparison purposes, paraffin block-embedded specimens were also sectioned. CK immunocytochemistry was performed on semi-thin sections using standard immunoperoxidase techniques, with expression being demonstrated using light microscopy.

RESULTS

The three-layer architecture of the TM was preserved. The morphology of the TM was vastly superior in the semi-thin resin sections than in the thicker paraffin sections. The outer, middle and inner layers were clearly demonstrated. The integrity of the outer epithelial layer was maintained, with an outer keratinizing stratum corneum and underlying stratum granulosum, stratum spinosum and stratum basale layers resting on the basal lamina. The thin inner mucosal layer was also viable, consisting of simple squamous or cuboidal cells. Preservation of the middle lamina propria was achieved, with demonstration of the outer radial and inner circular fibres. CK immunocytochemistry utilizing resin techniques provided excellent staining of CK 7 and 8 in the inner layer, with positive staining of CK 5 and 10 in the outer layer.

Tympanic membrane changes in central tympanic membrane perforations

PURPOSE

The objective of this study was to evaluate the histopathological changes in central tympanic membrane perforations caused by chronic otitis media without cholesteatoma.

MATERIALS AND METHODS

Twenty-nine temporal bones from 25 patients (13 male patients and 12 female patients) with central tympanic membrane perforations-18 chronic otitis media with perforation and 11 chronic otitis media with perforation caused by ventilation tubes-and 30 aged-matched normal temporal bones were included in this study. A scale was used to evaluate the extension of the migration of stratified squamous epithelium in the inner surface of the tympanic membrane. The thickness of tympanic membranes was measured halfway between the annular ligament and the perforation and compared with that of the normal bones. The presence of tympanosclerosis and papillary projections of squamous epithelium was also noted.

RESULTS

The extension of the migration of stratified squamous epithelium in the inner surface of the tympanic membrane was observed in 11 of the 29 perforations (38%). The thickness of tympanic membranes was significantly different between the perforation groups and the control group. Of the 29 tympanic membranes, 13 (44%) had tympanosclerosis and 8 (28%) revealed papillary projections of squamous epithelium.

CONCLUSIONS

Our study shows that a central tympanic perforation should not merely be considered as a simple defect. Most of the tympanic membranes showed one or more signs of sequelae or persistent abnormalities such as tympanosclerosis, papillary projections, thickening, and ingrowth without significant differences between the 2 central perforation groups.

Tympanic membrane perforation repair with acellular porcine submucosa

OBJECTIVES

To evaluate the efficacy of acellular porcine small intestine submucosa in the repair of chronic tympanic membrane perforations. Although tympanoplasty with autologous temporalis fascia and cartilage is common practice in the repair of chronic tympanic membrane perforations, these materials are associated with increased operative time and have variable availability and quality in individual patients. Recently, new materials for tympanoplasty have been explored, including acellular human dermis. Small intestine submucosa (Surgisis) is an inexpensive and readily available alternative to autologous and cadaveric grafts. In this study, we examined the use of small intestine submucosa in the repair of chronic tympanic membrane perforations in a chinchilla model.

STUDY DESIGN

Prospective pilot study using 10 adult chinchillas.

METHODS

Chronic tympanic membrane perforations were created in 10 adult chinchillas for a total of 20 perforations. Each animal underwent observation in one ear and repair with either autologous cartilage or small intestine submucosa in the opposite ear with Type I tympanoplasty.

RESULTS

A total of 20 chronic membrane perforations were created, with zero healing spontaneously after 8 weeks. In tympanoplasties performed in five chinchillas with small intestine submucosa, five of five (100%) remained healed 6 weeks postoperatively, whereas three of five (60%) remained healed with cartilage repair. Histologic analysis was performed in both successful cartilage and small intestine submucosa repairs.

CONCLUSION

These results suggest that small intestine submucosa is a viable alternative to autologous and cadaveric grafts in tympanoplasty. A larger randomized study in humans is indicated to evaluate this material in clinical practice.

[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.

Vibration characteristics and function of atelectatic segments in the tympanic membrane in fresh human cadaveric temporal bones

Dimeric segments are commonly encountered in otological practice. They may be associated with a mild conductive hearing loss and often coexist with other tympanic membrane and middle ear abnormalities. Some otologists have advocated surgical management but the consequences of dimeric segment stiffening, shielding or excision and grafting on acoustic transfer to the stapes footplate has been poorly explored. In this study, laser Doppler vibrometry was used to measure vibrations at the tympanic membrane and the stapes footplate in the fresh cadaveric human temporal bone. The dimeric segment vibrates more than the adjacent, thicker normal tympanic membrane. Shielding or excision and grafting of the dimeric segment with thicker and stiffer materials has little effect on displacement at the stapes footplate.

AlloDerm tympanoplasty of tympanic membrane perforations

PURPOSE

To study the effectiveness of AlloDerm (LifeCell Corporation, Branchburg, NJ) as a graft material in underlay tympanoplasty by comparison to autologous fascia in a chronic tympanic membrane perforation animal model.

MATERIALS AND METHODS

Seventeen chinchillas underwent creation of bilateral chronic tympanic membrane perforations over a 6-week period. Twenty-two stable perforations were divided equally between the experimental AlloDerm and control fascia graft groups. The grafts were surgically placed through a postauricular tympanomeatal flap. The tympanic membranes were examined at 4 and 10 weeks and then harvested for histopathological analysis. Tympanoplasty operative times, perforation closure rates, and gross and histological analyses were compared between the AlloDerm and fascia grafts.

RESULTS

A statistically significant difference in mean surgical time was recorded between the AlloDerm (47 minutes) and fascia (68 minutes) grafting procedures (t test, P =.001). Perforation closure was achieved in 90% of the AlloDerm and 100% of the fascia treated tympanic membranes. Gross and histopathologic inspections revealed no significant differences. Microscopically, AlloDerm and fascia grafts had similar inflammatory responses, but AlloDerm showed increased fibroblast infiltration and neovascularization.

CONCLUSION

The avoidance of donor site morbidity, reduction of surgical time, and excellent gross and histologic outcomes in this animal model reveal that AlloDerm could be a safe, cost-effective alternative to autologous fascia. Further study would be necessary in human clinical trials.

Middle ear effusions and structure of the tympanic membrane

OBJECTIVE

To study the effect of various middle ear effusions on the structure of the lamina propria of the tympanic membrane.

METHODS

Sterile and infective middle ear effusions were induced by obstruction of the eustachian tube in specific pathogen-free (SPF) rats and in rats with upper airway infections (URI), respectively. The condition of the tympanic membrane was monitored at regular intervals. After varying survival times, the animals were killed and the tympanic membranes processed for light and electron microscopy.

RESULTS

Sterile effusions always resulted in tympanosclerotic lesions. These lesions did not develop in the presence of primary-infected effusions. These effusions had a severe destructive effect on the lamina propria, followed by fibrosis. Generally, secondary infection did not markedly affect preexisting tympanosclerotic lesions. Moreover, calcification disappeared when re-aeration of the middle ear occurred, but the abnormal collagen depositions persisted.

CONCLUSIONS

Both sterile and infective effusions result in comprehensive irreversible changes in the lamina propria of the pars tensa. The development of tympanosclerosis is confined to sterile effusions. Mechanical injury and compromised vascularization of the lamina propria are likely to be important etiological factors in the development of tympanosclerosis.

Effects of platelet-derived growth factor-AA on the healing process of tympanic membrane perforation

PURPOSE

Platelet-derived growth factor basic 30-kD disulfide-bonded dimer of A and B chains (PDGF-AA, PDGF AB, PDGF-BB) and a cytokine, promoting wound healing by its mitogenicity for fibroblast and by stimulating the production of fibronectin and hyaluronic acid. This article investigates the effect of PDGF on the healing process of tympanic membrane (TM) perforation.

MATERIALS AND METHODS

The pars tensa of the posterior aspect of the TM of rats was excised and treated with 2 microg of PDGF-AA or placebo. The animals were killed at 3, 5, 7, 9, 11, 15, and 28 days after operation. The healing process of TM perforation was observed with a telescope and light microscope. The temporal bones were also immunohistochemically examined for PDGF-alpha receptor (PDGF-R(alpha)) and fibronectin.

RESULTS

All PDGF-AA-treated TM were completely closed by 5 days after surgery, whereas some of the placebo-treated TM were not closed at 15 postoperative days. PDGF-AA induced the most prominent proliferation of the connective tissue by 9 postoperative days, after which the growth of the connective tissue decreased. By the 4th postoperative week, the PDGF-treated TM were slightly thicker than normal TM. An intense expression of fibronectin was detected in the connective tissue layer of the TM that were treated with PDGF-AA. PDGF-R(alpha) was expressed in the epithelial layer of both the PDGF-treated and control TM.

CONCLUSION

These results show that PDGF-AA speeds up the healing process of TM defect, improves the rate of healing, and prevents atrophic changes in the healed TM by promoting the connective tissue growth. The use of PDGF-AA can be an effective alternative to surgery for managing TM perforations.

Effect of healed tympanic membrane perforations on umbo velocity in the rat

Heterodyne laser interferometry was used to measure tympanic membrane (TM) velocity at the umbo during acoustic stimulation in 2 groups of rats. The control group had a normal TM, while in the other group the TM was perforated and then allowed to heal for at least 28 days. Umbo velocity functions for constant sound pressure level stimuli were obtained for test tones between 0.3 and 40.0 kHz in each animal. The results revealed that velocity was the same in the control and healed TMs below 3.0 kHz. Above 5.0 kHz, the velocity response in the healed ear was between 3 and 12 dB smaller than in the control ears. Histologic evaluation of the healed perforation revealed a thick fibrous reaction between the epidermal and lamina propria layers. The results indicated that the added mass of the scar tissue changed the middle- and high-frequency TM responses.

Mast cell clusters in pars tensa membranae tympani in acute otitis media: a possible role in perforation healing

Mast cells are known to reside in pars flaccida membranae tympani and other parts of the middle ear mucosa in both rats and humans. However, the normal pars tensa contains no or only a few mast cells along the manubrial vessels. We examined the pars tensa of 25 rats in an experimental model of acute otitis media and found 13 mast cell clusters in 6 membranes. A majority of clusters were located in the anterior, superior quadrant and contained from 3 to 23 cells. The mast cells resided immediately under the inner epithelial lining or in the intermediate, fibrous layer. In two membranes mast cell clusters were found in the margin of apparently healed spontaneous perforations. We conclude that mast cells in some cases infiltrate pars tensa membranae tympani in the late and receding phase of acute otitis media. As these cell clusters in some cases were found immediately around apparently healed membrane perforations, we propose that the mast cell might participate in the repair processes of tympanic membrane perforation healing. This is supported by recent studies in wound healing and functions of a number of mast cell mediators.

The effects of keratinocyte growth factor on healing of tympanic membrane perforations

Tympanic membrane (TM) perforations heal by reepithelialization and fibrous layer proliferation. The rat TM model may be used to study growth factors that promote epithelialization and fibroblast proliferation, such as epidermal growth factor (EGF) and fibroblast growth factor (FGF). The authors previously evaluated the effects of FGF on tympanic membrane perforations and showed an enhanced rate of wound healing with preservation of normal structure and function. The same model was used to test keratinocyte growth factor (KGF, also called FGF-7). This growth factor has been shown to stimulate the migration and proliferation of keratinocytes. This is the first study investigating KGF in the tympanic membrane perforation model. Our results show that in contrast to FGF and EGF, KGF does not enhance the rate of wound healing, but rather results in a more organized wound repair process.

New artificial connective matrix made of fibrin monomers, elastin peptides and type I + III collagens: structural study, biocompatibility and use as tympanic membranes in rabbit

Experiments leading to the conception and development of a new artificial connective matrix based on collagen-elastin-fibrin associations are presented. Preliminary evaluation of this biomaterial as an artificial tympanic membrane is described. Morphological evaluation was performed by histopathological and scanning electron microscopic studies. Biocompatibility was documented by subcutaneous implantation and experimental grafting in rabbits was performed with histopathological studies of the tympanic grafted membranes. The positive results obtained in this experimental study enable future studies in humans to be prepared.

Spontaneous healing of traumatic tympanic membrane perforations in man: a century of experience

Widespread controversy exists concerning the treatment of traumatic tympanic membrane perforations. To elucidate the issue, a reference value for the rate of spontaneous tympanic membrane closure in man, to which the healing rates following different techniques of early surgical repair should be compared, was established on the basis of a review of more than 500 texts covering a century's literature on the traumatically perforated tympanic membrane. The spontaneous healing rate appeared to be close to 80 (78.7 per cent) in 760 evaluable cases of traumatic tympanic membrane perforations of all sorts diagnosed within 14 days post injury. A relative, causal-related variation of spontaneous healing could be demonstrated, and a pathogenetic classification of direct traumatic tympanic membrane perforations into ruptures induced by air-pressure changes, heat or corrosives, solids, and water pressures, is of proved clinical value and may have medico-legal validity. There is an obvious need for clinically controlled studies on the spontaneous healing of all kinds of traumatic perforations of the tympanic membrane in humans, and important elements in the design of future studies are advocated.

The histological appearance of the tympanic edge in contact with an indwelling ventilation tube (grommet)

This study describes the histological features of the tympanic membrane which has been in contact with an indwelling ventilation tube and considers the factors of tube type, time in situ, persistent aural discharge and the comparison to perforations residual to grommet extrusion. The specimens were obtained at the time of operative removal of a grommet. The 21 margins examined were characteristically hyperplastic and hyperkeratotic with a prominent granular layer. The squamous epithelium was from 8 to 25 cell layers thick and the connective tissue core was increased. Chronic inflammation was common. Features of chronic otitis media (respiratory epithelium, goblet cells and glandular tissue) were found in 7 margins (2 perforations and 5 grommet specimens). A theory of grommet extrusion is presented in this paper in the light of the histological findings.

Histological study of the thin replacement membrane of human tympanic membrane perforations

A histological study was done on the thin, nearly transparent replacement membrane of tympanic membrane perforations. Human tympanic membranes that were rejected for transplantation, were studied by light and electron microscopy. The abrupt reduction in thickness at the margin of the covered perforation, is entirely due to the reduction of the lamina propria. Even in the thinnest parts of the replacement membrane, a lamina propria is present, separated by continuous basement membranes from the epithelium and mucosa, and measuring no more than some 2-3 microns in thickness. This lamina propria consists of fibrils and interfibrillar matrix, but fibroblasts appear to be lacking. The epithelial layer does not contain basal cells, confirming the thesis that the upper layers are not generated by in situ proliferation, but that they have migrated from the periphery.