Collagen Type Distribution in the Healthy Human Tympanic Membrane

Comparison of subcutaneous soft tissue versus temporalis fascia as a tympanoplasty graft material: a retrospective cohort study

OBJECTIVE

This research compares the efficacy of subcutaneous soft tissue and temporalis fascia in tympanic membrane grafting for large tympanic membrane perforations.

METHODS

A retrospective cohort study compared tympanic membrane graft success rate and hearing outcomes in 248 patients who underwent tympanoplasty using subcutaneous soft tissue (n = 118) or temporalis fascia (n = 130) via the post-auricular approach.

RESULTS

Comparable results were observed in both groups. Tympanic membrane graft success rate was 98.3 per cent (116 ears) in the subcutaneous soft tissue group and 98.5 per cent (128 ears) in the temporalis fascia group. The rate of air-bone gap closure within 20 dB was 54.2 per cent (64 ears) and 60.0 per cent (78 ears) in the soft tissue and temporalis fascia groups, respectively (p = 0.360).

CONCLUSION

Subcutaneous soft tissue is a reliable and readily available tympanic membrane graft material in both revision and primary tympanoplasty for large tympanic membrane perforations.

Characterization of middle ear soft tissue damping and its role in sound transmission

Damping plays an important role in the middle ear (ME) sound transmission system. However, how to mechanically characterize the damping of ME soft tissues and the role of damping in ME sound transmission have not yet reached a consensus. In this paper, a finite element (FE) model of the partial external and ME of the human ear, considering both Rayleigh damping and viscoelastic damping for different soft tissues, is developed to quantitatively investigate the damping in soft tissues effects on the wide-frequency response of the ME sound transmission system. The model-derived results can capture the high-frequency (above 2 kHz) fluctuations and obtain the 0.9 kHz resonant frequency (RF) of the stapes velocity transfer function (SVTF) response. The results show that the damping of pars tensa (PT), stapedial annular ligament (SAL) and incudostapedial joints (ISJ) can help smooth the broadband response of the umbo and stapes footplate (SFP). It is found that, between 1 and 8 kHz, the damping of the PT increases the magnitude and phase delay of the SVTF above 2 kHz while the damping of the ISJ can avoid excessive phase delay of the SVTF, which is important in maintaining the synchronization in high-frequency vibration but has not been revealed before. Below 1 kHz, the damping of the SAL plays a more important role, and it can decrease the magnitude but increases the phase delay of the SVTF. This study has implications for a better understanding of the mechanism of ME sound transmission.

Dominant Stickler Syndrome

The Stickler syndromes are a group of genetic connective tissue disorders associated with an increased risk of rhegmatogenous retinal detachment, deafness, cleft palate, and premature arthritis. This review article focuses on the molecular genetics of the autosomal dominant forms of the disease. Pathogenic variants in COL2A1 causing Stickler syndrome usually result in haploinsufficiency of the protein, whereas pathogenic variants of type XI collagen more usually exert dominant negative effects. The severity of the disease phenotype is thus dependent on the location and nature of the mutation, as well as the normal developmental role of the respective protein.

Evaluation of acoustic changes in and the healing outcomes of rat eardrums with pars tensa and pars flaccida perforations

Objectives

To systematically explore the differences in acoustic changes and healing outcomes of tympanic membranes (TMs) with pars flaccida perforation (PFP) and pars tensa perforation (PTP).

Methods

We created PFPs and PTPs of various sizes in Sprague-Dawley rats, and evaluated TM umbo velocity and hearing function using laser Doppler vibrometry and auditory brainstem response (ABR) measurement before and immediately after perforation. Two weeks later, hearing was reevaluated and TMs were investigated by immunohistochemical staining.

Results

Small PFPs and PTPs did not significantly affect umbo velocity and hearing function. Large PFPs increased umbo velocity loss at low frequency (1.5 kHz) and elevated ABR thresholds within 1-2 kHz. Large PTP caused significant velocity loss at low frequencies from 1.5 to 3.5 kHz and threshold elevations at full frequencies (1-2 kHz). Two weeks after the perforation, the hearing function of rats with healed PFPs recovered completely. However, high-frequency hearing loss (16-32 kHz) persisted in rats with healed PTPs. Morphological staining revealed that no increase in the thickness and obvious increase in collagen I level of regenerated par flaccida; regenerated pars tensa exhibited obvious increase in thickness and increased collagen I, while the collagen II regeneration was limited with discontinuous and disordered structure in regenerated pars tensa.

Conclusion

The hearing loss caused by large PFP limits at low frequencies while large PTP can lead to hearing loss at wide range frequencies. PFP and PTP have different functional outcomes after spontaneous healing, which is determined by the discrepant structure reconstruction and collagen regeneration.

Mechanics of Total Drum Replacement Tympanoplasty Studied With Wideband Acoustic Immittance

OBJECTIVE

Poor hearing outcomes often persist following total drum replacement tympanoplasty. To understand the mechanics of the reconstructed eardrum, we measured wideband acoustic immittance and compared the mechanical characteristics of fascia-grafted ears with the normal tympanic membrane.

STUDY DESIGN

Prospective comparison study.

SETTING

Tertiary care center.

METHODS

Patients who underwent uncomplicated total drum replacement with temporalis fascia grafts were identified. Ears with healed grafts, an aerated middle ear, and no other conductive abnormalities were included. All patients underwent pre- and postoperative audiometry. Wideband acoustic immittance was measured with absorbance and impedance computed. Fascia-grafted ears were compared with normal unoperated ears.

RESULTS

Eleven fascia-grafted ears without complications were included. Postoperatively, the median air-bone gap was 15 dB (250-4000 Hz), with variation across frequency and between ears. Fifty-six control ears were included. Absorbance of fascia-grafted ears was significantly lower than that of normal ears at 1 to 4 kHz (P < .05) but similar below 1 kHz. Impedance magnitude demonstrated deeper and sharper resonant notches in fascia-grafted ears than normal ears (P < .05), suggesting lower mechanical resistance of the fascia graft.

CONCLUSION

The mechanics of fascia-grafted ears differ from the normal tympanic membrane by having lower absorbance at mid- to high frequencies and thus poor sound transmission. The lower resistance in fascia-grafted ears may be due to poor coupling of the graft to the malleus. To improve sound transmission, grafts for tympanic membrane reconstructions would benefit from refined mechanical properties.

Auditory dysfunction in type 2 Stickler Syndrome

PURPOSE

To present the extent and site of lesion of auditory dysfunction in a large cohort of individuals with type 2 Stickler Syndrome. Type 2 Stickler Syndrome results from a mutation in the gene coding for α-1 type XI pro-collagen, which has been identified in the human vitreous, cartilage and the cochlea of the mouse. The condition is characterised by classic ocular abnormalities, auditory dysfunction, osteoarthropathy and oro-facial dysplasia.

METHODS

This is a population study which used a combination of audiometric, tympanometric, and self-report measures on a series of 65 individuals (mean age 29.2 years, range 3-70, female 63.1%) with genetically confirmed type 2 Stickler Syndrome.

RESULTS

Hearing impairment was identified in at least one ear for 69% of individuals. Analysis against age-matched normative data showed that reduced hearing sensitivity was present across all test frequencies. Sensorineural hearing loss was most common (77% of ears), with conductive (3%), mixed (7%) and no hearing loss (13%), respectively. The proportion of hypermobile tympanic membranes (24%) was less than previously documented in type 1 Stickler Syndrome. When present, this appears to arise as a direct result of collagen abnormalities in the middle ear. Self-report measures of speech and spatial hearing in sound were comparable to a non-syndromic cohort with similar audiometric thresholds.

CONCLUSIONS

Auditory impairment in type 2 Stickler Syndrome is predominantly associated with cochlear hearing loss of varying severities across affected individuals. The impact on hearing thresholds can be seen across the frequency range, suggesting a contribution of defective collagen throughout the cochlea. Self-report questionnaires showed that difficulties understanding speech, and spatial information in sound (such as that used for localisation), were worse than a young, normal-hearing population but comparable to a non-syndromic cohort with similar audiometric thresholds. Therefore, it is likely that hearing loss in type 2 Stickler Syndrome arises in the auditory periphery, without significant central processing deficits.

Biomimetic Tympanic Membrane Replacement Made by Melt Electrowriting

The tympanic membrane (TM) transfers sound waves from the air into mechanical motion for the ossicular chain. This requires a high sensitivity to small dynamic pressure changes and resistance to large quasi-static pressure differences. The TM achieves this by providing a layered structure of about 100µm in thickness, a low flexural stiffness, and a high tensile strength. Chronically infected middle ears require reconstruction of a large area of the TM. However, current clinical treatment can cause a reduction in hearing. With the novel additive manufacturing technique of melt electrowriting (MEW), it is for the first time possible to fabricate highly organized and biodegradable membranes within the dimensions of the TM. Scaffold designs of various fiber composition are analyzed mechanically and acoustically. It can be demonstrated that by customizing fiber orientation, fiber diameter, and number of layers the desired properties of the TM can be met. An applied thin collagen layer seals the micropores of the MEW-printed membrane while keeping the favorable mechanical and acoustical characteristics. The determined properties are beneficial for implantation, closely match those of the human TM, and support the growth of a neo-epithelial layer. This proves the possibilities to create a biomimimetic TM replacement using MEW.

Necessities, opportunities, and challenges for tympanic membrane perforation scaffolding-based bioengineering

Tympanic membrane (TM) perforation is a global clinical dilemma. It occurs as a consequence of object penetration, blast trauma, barotrauma, and middle ear diseases. TM perforation may lead to otitis media, retraction pockets, cholesteatoma, and conductive deafness. Molecular therapies may not be suitable to treat perforation because there is no underlying tissue matrix to support epithelium bridging. Chronic perforations are usually reconstructed with autologous grafts via surgical myringoplasty. Surgical treatment is uncomfortable for the patients. The grafting materials are not perfect because they produce an opaque membrane, fail in up to 20% of cases, and are suboptimal to restore acoustic function. Millions of patients from developing parts of the world have not got access to surgical grafting due to operational complexities, lack of surgical resources, and high cost. These shortcomings emphasize bioengineering to improve placement options, healing rate, hearing outcomes, and minimize surgical procedures. This review highlights cellular, structural, pathophysiological, and perforation specific determinants that affect healing, acoustic and surgical outcomes; and integrates necessities relevant to bioengineered scaffolds. This study further summarizes scaffolding components, progress in scaffolding strategies and design, and engenders limitations and challenges for optimal bioengineering of chronic perforation.

Developing a novel meatal areolar tissue autograft for minimally invasive tympanoplasty

BACKGROUND

We developed an easy and minimally invasive method of transmeatal tympanoplasty using meatal areolar tissue (MAT) grafts to achieve less postoperative morbidity or surgical scarring. We compared the functional and anatomical results of the developed method with conventional endaural tympanoplasty with a temporalis fascia (TF) graft.

METHODS

In this retrospective cohort study, 58 patients (59 ears) with simple chronic otitis media who underwent type I tympanoplasty between January 2016 and August 2018 were included. All surgeries were performed in a tertiary referral hospital and by the same senior surgeon. The tympanic membrane (TM) was repaired with either a TF or an MAT graft.

RESULTS

Healing of the perforated TM and improvement in a hearing test by air-bone gap (ABG) closure were identified. Postoperative wound conditions were also evaluated. Twenty-eight ears were grafted with MAT, and 31 ears were grafted with TF. Graft success was observed in 26 patients (92.9%) in the MAT group and 28 patients (90.3%) in the TF group. Both groups showed functional improvement compared with the preoperative measurements. The postoperative pure tone audiogram (p = 0.737), ABG closure (p = 0.547), and graft success rate (p = 0.726) were not significantly different between the two groups. Neither wound dehiscence nor keloid formation was observed in our patients.

CONCLUSION

Both MAT and TF grafts revealed satisfactory surgical and functional results. Compared with the conventional endaural approach with TF grafts, the new transmeatal approach method with an MAT graft causes relatively minimal trauma and results in better wound cosmetics. This method represents an easy, minimally invasive surgery and shows comparatively good results.

Expression of collagen type III in healing tympanic membrane

OBJECTIVES

Type III collagen plays significant role in skin wound healing, forming provisional matrix guiding the inflammatory cells and fibroblasts into the wound site. Our preliminary study performed on rat's tympanic membrane (TM) using Rat Wound Healing RT2 Profiler PCR Array revealed up-regulated expression of collagen type III α1 chain mRNA also during healing of TM. This study was undertaken to confirm and evaluate collagen type III protein expression and distribution during TM healing process.

METHODS

Sixty rats were used, of which 10 served as controls and the others had their TM perforated. The experimental animals were divided into five subgroups on the basis of time points (03, 06, 09, 14, 20 day after injury). Videootoscopy and histology were employed to assess morphology of the healing process. The expression of collagen type III was evaluated using Western blot analysis and its tissue localization was determined by the immunohistochemical method.

RESULTS

The expression of collagen type III remained on the same level as in control TM up to day 06. On day 09 abrupt (p = 0.01) increase of the collagen type III expression was observed and it maintained on the same level to the end of observation period. In perforated TM collagen type III was detected in the healing area along the perforation border and around dilated blood vessels. On day 14 and 20 collagen type III was found in the connective tissue filling up the TM previous defect.

CONCLUSIONS

Taking into consideration our recent and previous data, as well as results obtained by other authors, is seems possible that the increase of collagen type III expression in the late stage of TM healing contributes to proper scar formation.

Application of mesenchymal stem cell for tympanic membrane regeneration by tissue engineering approach

Regeneration is a biological process of cell renewal that takes place in damaged tissues or organs. It is naturally stimulated by the release of different growth factors, cytokines, surface molecules, and stem cells at the wounded sites. The tympanic membrane (TM) is an essential component of the hearing process in the auditory system, which can amplify and transmit sound vibrations through a chain of mobile ossicles. Middle ear infection, external sound pressure, insertion of sharp objects into the ear, and severe trauma are the main causes of TM perforations (TMPs), which could result in deficient hearing function. So far, otolaryngologists have employed surgical procedures (myringoplasty or tympanoplasty) to close the perforated eardrum. Because of limitations such as side effects, discomfort, and high cost to patients, there is a need for better alternatives to surgical procedures. Tissue engineering is a promising tool that can overcome the operational risk and restore, maintain, and improve the function of the TM using a range of biocompatible scaffolds, commercially available growth factors, and stem cells. Currently, multipotent mesenchymal stem cells (MSCs) are a good therapeutic option for the treatment of TMPs because of their self-renewing, and autocrine and paracrine activities. As there are fewer risks of isolation in the use of MSCs for the treatment of TMPs, they are more advantageous for tissue regeneration. The delivery of either MSCs alone or a combination of MSCs with biomaterials and growth factors (GFs) at the ruptured TM sites may enhance the activation of epithelial stem cell markers and increase the migration and proliferation of keratinocytes resulting in faster closure of TMPs. This review focuses on the current strategies used to treat TMPs and the importance of MSCs in TM regeneration. Particularly, we have discussed the synergistic effect of MSCs and scaffolds or GFs or scaffolds/GFs in TM regeneration. Finally, with the advancement of tissue engineering technologies such as 3D and 4D bioprinting, MSCs can be used to design patient-specific scaffolds, which may contain physical and chemical guidance cues to improve the extent and rate of targeted tissue regeneration.

Tympanic Membrane Collagen Expression by Dynamically Cultured Human Mesenchymal Stromal Cell/Star-Branched Poly(ε-Caprolactone) Nonwoven Constructs

The tympanic membrane (TM) primes the sound transmission mechanism due to special fibrous layers mainly of collagens II, III, and IV as a product of TM fibroblasts, while type I is less represented. In this study, human mesenchymal stromal cells (hMSCs) were cultured on star-branched poly(ε-caprolactone) (*PCL)-based nonwovens using a TM bioreactor and proper differentiating factors to induce the expression of the TM collagen types. The cell cultures were carried out for one week under static and dynamic conditions. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) were used to assess collagen expression. A Finite Element Model was applied to calculate the stress distribution on the scaffolds under dynamic culture. Nanohydroxyapatite (HA) was used as a filler to change density and tensile strength of *PCL scaffolds. In dynamically cultured *PCL constructs, fibroblast surface marker was overexpressed, and collagen type II was revealed via IHC. Collagen types I, III and IV were also detected. Von Mises stress maps showed that during the bioreactor motion, the maximum stress in *PCL was double that in HA/*PCL scaffolds. By using a *PCL nonwoven scaffold, with suitable physico-mechanical properties, an oscillatory culture, and proper differentiative factors, hMSCs were committed into fibroblast lineage-producing TM-like collagens.

High-Frequency Conductive Hearing following Total Drum Replacement Tympanoplasty

OBJECTIVES

Conventional reporting of posttympanoplasty hearing outcomes use a pure-tone averaged air-bone gap (ABG) largely representing a low-frequency sound conduction. Few studies report high-frequency conductive hearing outcomes. Herein, we evaluate high-frequency ABG in patients following temporalis fascia total drum replacement.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary care center.

SUBJECTS AND METHODS

All patients who underwent type 1 tympanoplasty using a lateral graft total drum replacement technique between August 2016 and February 2019 were identified. Patients with pre- and postoperative audiograms were included. Low-frequency ABG was calculated as the mean ABG at 250, 500, and 1000 Hz. High-frequency ABG was calculated at 4 KHz. Pre- and postoperative ABGs were compared.

RESULTS

Twenty-three patients were included, and the mean age at surgery was 44 years (range, 9-68 years). Perforation etiology was from trauma (n = 14) or chronic otitis media (n = 9). Preoperative mean low-frequency ABG was 27.8 ± 12.6 dB and mean high-frequency ABG was 21.5 ± 15.1 dB (P = .044). Postoperatively, the mean low-frequency ABG was significantly reduced by 15.5 ± 13.3 dB (P < .001) while the mean high-frequency ABG insignificantly changed (reduced by 2.6 ± 16.2 dB, P = .450).

CONCLUSION

In a series of patients undergoing temporalis fascia total drum replacement, low-frequency ABG improved; however, high-frequency conductive hearing loss persists. Conventional methods of reporting ABG may not identify persistent high-frequency ABG. These results merit further study across a range of tympanoplasty graft materials and surgical techniques.

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.

Expression of collagens type I and V in healing rat's tympanic membrane

OBJECTIVES

Our preliminary study performed on perforated rat's tympanic membrane (TM) using Rat Wound Healing RT2 Profiler PCR Array showed significantly increased levels of mRNA for collagens type I and V. Enhanced expression of those genes does not assure that their protein products are indeed present, and in what quantity. Therefore, this study was undertaken to analyze the collagen type I and V content in the healing TM.

METHODS

Sixty rats were used, of which 10 served as controls and the others had their TM perforated. The experimental animals were divided into five subgroups on the basis of time points (03, 06, 09, 14, 20 day after injury). Videootoscopy and histology were employed to assess the morphology of the healing process. The expression of collagen type I and V was evaluated using Western blot analysis. Tissue localization of collagens was determined by the immunofluorescence method.

RESULTS

The collagen type I expression was three times higher on the third day after injury and remained on that level for whole period of observation, up to day 20. The increase of the collagen type V expression was gradual, reaching the highest level on day 14 following injury. In comparison to the control TM statistically significant increase in the level of expression was observed starting from day 09 to the end of observation period. In healing TM immunofluorescent labeling of collagen type I and V was seen on the surface of remnants of previous lamina propria and in the loose proliferating fibrous tissue. On day 20 immunofluorescence was present mainly on the surface of thin connective tissue layers forming the scar in the place of previous perforation.

CONCLUSION

Although the collagens type I and V are present only in subepithelial layer in the normal rat's TM they play significant role in TM healing process.

Otopathologic evaluation of temporalis fascia grafts following successful tympanoplasty in humans

OBJECTIVE

Temporalis fascia is a commonly used graft material in tympanoplasty; however, little is known about how the histological structure of fascia remodels postimplantation. Herein, we aim to quantify the pre- and postoperative microstructure of temporalis fascia and compare histological findings to the native tympanic membrane (TM).

METHODS

Temporal bone specimens having undergone successful subtotal or total drum replacement using temporalis fascia were identified (n = 3). Surgically prepared preimplantation temporalis fascia (PreTF, n = 4) and normal TMs (n = 5) were used as controls. Multiple measurements of thickness of PreTF and of normal and fascia reconstructed TMs at the mesotympanum and hypotympanum were obtained. Collagen fiber patterns of normal and reconstructed TMs were histologically described.

RESULTS

In cases of fascia tympanoplasty, the mean time of surgery to death was 16 years (range 8-28 years). All cases contained an aerated middle ear without residual perforation. There was no significant difference between the thickness of PreTF and fascia of reconstructed TMs (234.9 ± 144.9 μm vs. 162.9 ± 71.9 μm, P = 0.1). The lamina propria and total thicknesses of controls (59.8 ± 39.3 μm and 83.7 ± 42.4 μm, respectively) were thinner than the PreTF and fascia-reconstructed TMs, respectively, in all cases (P ≤ 0.001, P ≤ 0.001). Reconstructed TMs contained a thick, longitudinal fiber structure that was qualitatively similar to PreTF.

CONCLUSION

Based on human temporal bone specimens, temporalis fascia does not significantly remodel, change thickness, or change fibrous structure following successful tympanoplasty. Results have implications for selection and surgical preparation of graft materials in TM reconstruction.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:E351-E358, 2018.

Fibrinogen-Based Collagen Fleece Graft Myringoplasty for Traumatic Tympanic Membrane Perforation

Background and Objectives

The aim of this study was to investigate how fibrinogen-based collagen fleece (Tachocomb®) graft myringoplasty (FCGM), performed under microscopic guidance, improves both hearing and tympanic membrane tissue repair in patients with traumatic tympanic membrane perforation (TMP).

Subjects and Methods

Between August 2009 and March 2015, a total of 52 patients with traumatic TMP visited the department of otorhinolaryngology at a secondary medical center. Twenty-nine of these underwent FCGM under microscopic guidance in our outpatient clinic. For each patient, we recorded the location and size of the perforation, the time elapsed from the onset of TMP until the myringoplasty, and the hearing level both before and after myringoplasty.

Results

The TMP closed completely in all cases (29 of 29 patients). After myringoplasty, the postoperative air-bone gap (ABG) differed significantly from the preoperative ABG. Three of the 29 patients (10.3%) experienced complications. Specifically, 2 presented with otorrhea after FCGM, but conservative management led to improvement without recurrence of perforation. One patient showed delayed facial palsy 1 week after the procedure. The condition of this patient also improved and the palsy was not permanent.

Conclusions

FCGM may be an effective treatment option in case of traumatic TMP. The procedure requires no hospitalization, and can be used to avoid traditional tympanoplasty.

Acceleration of Healing of Traumatic Tympanic Membrane Perforation in Rats by Implanted Collagen Membrane Integrated with Collagen-Binding Basic Fibroblast Growth Factor

Traumatic tympanic membrane (TM) perforation is very common in clinical practice. Several biomaterials have been reported to play a role in TM reparation, whereas their functional recovery is limited when used alone. Meanwhile, the administration of biofactors could promote functional recovery, but rapid distribution and short half-time obstruct their application. To study the effect of traumatic TM regeneration, we prepared collagen membrane (CM) integrated with collagen-binding basic fibroblast growth factor (CBD-bFGF) and implanted into the injury site of perforated TM in Sprague-Dawley rats. The study on CBD-bFGF in vitro showed that CBD-bFGF accelerated the proliferation of human fibroblast cell HS-865 biologically and was released from CM gradually. In vivo study, through the gross anatomy, auditory brainstem responses assay, histological staining, and transmission electron microscopy observation at d7, d14, and d28 after the acute TM perforation, we found that CBD-bFGF-integrated CM promoted the healing rate at an early stage (∼7 days), reduced the healing time of perforated TM, and notably retrieved the structure and hearing of TM. These findings suggest that CM modified with CBD-bFGF could be therapeutically appropriate for the treatment of TM perforation.

Fiber Arrangement in the Rat Tympanic Membrane

The fiber arrangement in the pars tensa of the rat tympanic membrane (TM) was observed using a high resolution scanning electron microscope. The entire pars tensa is composed of fibrils with diameter of approximately 25 nm. These fibrils can be grouped into radial, circular, parabolic, and oblique fibers as reported in other mammals. The radial fibrils interweave into a planar form rather than into discrete cylindrical fibers. Before attaching to the manubrium and tympanic ring, the radial fibrils bend and cross neighboring fibrils to form a random fibril network, and change their direction from perpendicular to somewhat parallel to the manubrium and tympanic ring. The circular fibrils form cylindrical fibers near the peripheral part of the TM while closer to the manubrium, they form planar bundles. The observed fiber morphology and arrangement may provide helpful information in improving numerical models for the TM's acoustical response and designing a fibrous graft for the repair of TM perforations. Anat Rec, 299:1531-1539, 2016. © 2016 Wiley Periodicals, Inc.

Design, fabrication, and in vitro testing of novel three-dimensionally printed tympanic membrane grafts

The tympanic membrane (TM) is an exquisite structure that captures and transmits sound from the environment to the ossicular chain of the middle ear. The creation of TM grafts by multi-material three-dimensional (3D) printing may overcome limitations of current graft materials, e.g. temporalis muscle fascia, used for surgical reconstruction of the TM. TM graft scaffolds with either 8 or 16 circumferential and radial filament arrangements were fabricated by 3D printing of polydimethylsiloxane (PDMS), flex-polyactic acid (PLA) and polycaprolactone (PCL) materials followed by uniform infilling with a fibrin-collagen composite hydrogel. Digital opto-electronic holography (DOEH) and laser Doppler vibrometry (LDV) were used to measure acoustic properties including surface motions and velocity of TM grafts in response to sound. Mechanical properties were determined using dynamic mechanical analysis (DMA). Results were compared to fresh cadaveric human TMs and cadaveric temporalis fascia. Similar to the human TM, TM grafts exhibit simple surface motion patterns at lower frequencies (400 Hz), with a limited number of displacement maxima. At higher frequencies (>1000 Hz), their displacement patterns are highly organized with multiple areas of maximal displacement separated by regions of minimal displacement. By contrast, temporalis fascia exhibited asymmetric and less regular holographic patterns. Velocity across frequency sweeps (0.2-10 kHz) measured by LDV demonstrated consistent results for 3D printed grafts, while velocity for human fascia varied greatly between specimens. TM composite grafts of different scaffold print materials and varied filament count (8 or 16) displayed minimal, but measurable differences in DOEH and LDV at tested frequencies. TM graft mechanical load increased with higher filament count and is resilient over time, which differs from temporalis fascia, which loses over 70% of its load bearing properties during mechanical testing. This study demonstrates the design, fabrication and preliminary in vitro acoustic and mechanical evaluation of 3D printed TM grafts. Data illustrate the feasibility of creating TM grafts with acoustic properties that reflect sound induced motion patterns of the human TM; furthermore, 3D printed grafts have mechanical properties that demonstrate increased resistance to deformation compared to temporalis fascia.

Ciprofloxacin Decreases Collagen in Mouse Tympanic Membrane Fibroblasts

Objectives

To determine how collagen production by tympanic membrane fibroblasts is affected by ciprofloxacin at levels found in eardrops.

Study Design

Prospective, controlled, and blinded cell culture study.

Setting

Academic tertiary medical center.

Subjects

Cell culture of mouse fibroblasts.

Methods

A primary fibroblast culture was established from mouse tympanic membranes. Fibroblasts were cultured until they were 75% confluent, then treated with dilute hydrochloric acid (control) or ciprofloxacin (0.01% or 0.3%) for 24 or 72 hours for Western blotting and for 24 or 48 hours for cytotoxicity assay. Cells were observed with phase-contrast microscope. Western blotting was performed for collagen type 1 α1 (collagen 1A1) and α-tubulin.

Results

Fibroblasts treated with 0.01% and 0.3% ciprofloxacin for 24 hours had lower levels of collagen 1A1 ( P = .0005 and P < .0001, respectively) and α-tubulin (both P < .0001) than control fibroblasts. Collagen 1A1 and α-tubulin levels were lower in fibroblasts treated with 0.3% than with 0.01% ciprofloxacin ( P = .02 and P = .014). After 72 hours, 0.3% ciprofloxacin completely eliminated collagen 1A1 and α-tubulin ( P < .001). Cells treated with 0.01% ciprofloxacin for 72 hours also had lower collagen 1A1 ( P < .0001) and α-tubulin ( P = .005) as compared with the control. Seventy-two-hour incubation in 0.01% or 0.3% ciprofloxacin resulted in lower levels of collagen 1A1 ( P = .009 and P < .0001, respectively) and α-tubulin ( P = .007 and P < .0001, respectively) than 24-hour incubation. Cytotoxicity assay and phase-contrast microscopy mirrored these findings.

Conclusions

Treatment of tympanic membrane fibroblasts with 0.3% ciprofloxacin, as found in eardrops, reduces fibroblast viability and collagen and α-tubulin protein levels. These findings could explain tympanic membrane healing problems associated with quinolone eardrops.

Outlook for Tissue Engineering of the Tympanic Membrane

Tympanic membrane perforation is a common problem leading to hearing loss. Despite the autoregenerative activity of the eardrum, chronic perforations require surgery using different materials, from autologous tissue - fascia, cartilage, fat or perichondrium - to paper patch. However, both, surgical procedures (myringoplasty or tympanoplasty) and the materials employed, have a number of limitations. Therefore, the advances in this field are incorporating the principles of tissue engineering, which includes the use of scaffolds, biomolecules and cells. This discipline allows the development of new biocompatible materials that reproduce the structure and mechanical properties of the native tympanic membrane, while it seeks to implement new therapeutic approaches that can be performed in an outpatient setting. Moreover, the creation of an artificial tympanic membrane commercially available would reduce the duration of the surgery and costs. The present review analyzes the current treatment of tympanic perforations and examines the techniques of tissue engineering, either to develop bioartificial constructs, or for tympanic regeneration by using different scaffold materials, bioactive molecules and cells. Finally, it considers the aspects regarding the design of scaffolds, release of biomolecules and use of cells that must be taken into account in the tissue engineering of the eardrum. The possibility of developing new biomaterials, as well as constructs commercially available, makes tissue engineering a discipline with great potential, capable of overcoming the drawbacks of current surgical procedures.

Altered response of fibroblasts from human tympanosclerotic membrane to interacting mast cells: implication for tissue remodeling

Several lines of evidence suggest that a tympanosclerotic (TMS) lesion often develops secondary to acute and chronic otitis media. Histological findings indicate that fibroblasts and inflammatory cells, including mast cells, play a key role in the tympanosclerotic plaque formation. However, details on the functional characteristics of tympanosclerotic fibroblasts (Fs(TMS)) are scanty. Therefore the aim of our study was to examine the activity of human fibroblasts from tympanosclerotic lesions and to evaluate the influence of stimulated by crosslinking of IgE receptor mast cells (HMC-1(FcɛRI)) on fibroblast functional behavior. We observed that fibroblasts from normal tympanic membrane (Fs(TM)) released less TNF-α, TGF-β1 and IL-6 compared to Fs(TMS). Fs(TMS) but not Fs(TM) upon interaction with HMC-1(FcɛRI) released increased quantities of TNF-α and TGF-β1. Exposing the fibroblast to HMC-1(FcɛRI) cells resulted in an increased synthesis of proteins including collagen. We noted that the COL2A1 transcript level increased ∼5- and ∼12-fold in Fs(TM) and Fs(TMS) co-cultured with HMC-1(FcɛRI), respectively. Both Fs(TM) and Fs(TMS) upon maintenance in the primary culture released significant quantities of matrix metalloproteinase 9 (MMP-9). However, Fs(TMS) released ∼5-fold more MMP-9 activity compared to the Fs(TM) cultures. The mast cell-induced release of TNF-α, TGF-β1 and MMP-9 sustained for a longer time in Fs(TMS) cultures compared to Fs(TM). Concluding, our data strongly indicate that increased fibroblast sensitivity to mast cell stimulation greatly contributes to the excessive fibrosis and pathological remodeling of the tympanic membrane. We postulate that the persistency of the Fs(TMS) activated state could be an important factor in the pathogenesis of tympanosclerosis.

Scaffolds for tympanic membrane regeneration in rats

Tympanic membrane (TM) perforations lead to significant hearing loss and result in possible infection of the middle ear. Myringoplasty is commonly performed to repair chronic perforations. Although various grafts and materials have been used to promote TM regeneration, all have associated limitations. The aim of this study was to evaluate the efficacy and feasibility of two graft materials, silk fibroin scaffold (SFS) and porcine-derived acellular collagen type I/III scaffold (ACS), compared with two commonly used graft materials (paper patch and Gelfoam) for the promotion of TM regeneration. These scaffolds were implanted using on-lay myringoplasty in an acute TM perforation rat model. Surface morphology of the scaffolds was observed with scanning electron microscopy. The morphology of the TM was assessed at various time points postimplantation using otoscopy, light and electron microscopy, and functional outcomes by auditory brainstem responses. We found that SFS and ACS significantly accelerated the TM perforation closure, obtained optimal TM thickness, and resulted in better trilaminar morphology with well-organized collagen fibers and early restoration of hearing. However, paper patch and Gelfoam lost their scaffold function in the early stages and showed an inflammatory response, which may have contributed to delayed healing. This study indicates that compared with paper patch and Gelfoam, SFS and ACS are more effective in promoting an early TM regeneration and an improved hearing, suggesting that these scaffolds may be potential substitutes for clinical use.

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.

Hearing impairment in Stickler syndrome: a systematic review

Background

Stickler syndrome is a connective tissue disorder characterized by ocular, skeletal, orofacial and auditory defects. It is caused by mutations in different collagen genes, namely COL2A1, COL11A1 and COL11A2 (autosomal dominant inheritance), and COL9A1 and COL9A2 (autosomal recessive inheritance). The auditory phenotype in Stickler syndrome is inconsistently reported. Therefore we performed a systematic review of the literature to give an up-to-date overview of hearing loss in Stickler syndrome, and correlated it with the genotype.

Methods

English-language literature was reviewed through searches of PubMed and Web of Science, in order to find relevant articles describing auditory features in Stickler patients, along with genotype. Prevalences of hearing loss are calculated and correlated with the different affected genes and type of mutation.

Results

313 patients (102 families) individually described in 46 articles were included. Hearing loss was found in 62.9%, mostly mild to moderate when reported. Hearing impairment was predominantly sensorineural (67.8%). Conductive (14.1%) and mixed (18.1%) hearing loss was primarily found in young patients or patients with a palatal defect. Overall, mutations in COL11A1 (82.5%) and COL11A2 (94.1%) seem to be more frequently associated with hearing impairment than mutations in COL2A1 (52.2%).

Conclusions

Hearing impairment in patients with Stickler syndrome is common. Sensorineural hearing loss predominates, but also conductive hearing loss, especially in children and patients with a palatal defect, may occur. The distinct disease-causing collagen genes are associated with a different prevalence of hearing impairment, but still large phenotypic variation exists. Regular auditory follow-up is strongly advised, particularly because many Stickler patients are visually impaired.

Matrix metalloproteinase-8/collagenase-2 in childhood otitis media with effusion

BACKGROUND

Matrix metalloproteinases (MMPs), gelatinases, have been associated with otitis media with effusion (OME), but the role of collagenase-2/matrix metalloproteinase-8 (MMP-8) in OME has not been studied previously. We studied the levels, isoenzyme distribution, and activation of MMP-8 in childhood OME, and also the levels of pro- and active forms of MMP-2 and -9 as well as 120 kDa gelatinase complexes were assessed.

METHODS

Seventy middle ear fluid (MEF) samples were collected from 54 children with OME and classified to mucoid (n = 39) or serous (n = 31). MMPs were studied from MEF samples by time-resolved immunofluorometric assay, Western immunoblotting, and gelatin-zymography.

RESULTS

MMP-8 was found in its active form in MEF of children with OME. MMP-8 levels were significantly higher in mucous relative to serous OME. The pro- or active MMP-2 and -9 were found in MEF, but no MEF type-specific differences were found.

CONCLUSION

Our results suggest that MMP-8 may play a role in the pathogenesis of childhood OME. New therapeutic strategies with MMP inhibitors targeting MMP-8, but allowing MMP-8 to carry out the protective action, may play a role in the future treatment of otitis media and OME. However, further studies of this topic are needed.

Cartilage-perichondrium: an ideal graft material?

Temporalis fascia has long been regarded as the ideal graft material for tympanic membrane repair. However it often does not seem to withstand negative middle ear pressure in the post operative period. Tragal cartilage with perichondrium would appear to be a better graft material with good hearing outcome. It can be obtained easily with cosmetically acceptable incision. In the present study, we have compared the graft properties of temporalis fascia verses tragal cartilage perichondrium with respect to healing, hearing and rate of post operative retraction or reperforation. 132 patients of chronic otitis media with pure conductive hearing loss were posted for tympanoplasty. Temporalis fascia graft was used in 71 patients and cartilage perichondrium (composite graft) was used in 61 patients. Post operative healing, hearing and rate of retraction or reperforation was compared for both the graft materials. All the patients were followed up for 2 years. Patients where temporalis fascia graft was used, 60 (84.5%) showed a good neotympanum, 7(9.85%) had reperforation and 5(7.04%) had retraction pockets. Patients where tragal cartilage perichondrium was used, 60(98.36%) showed a healed tympanic membrane and only 1(1.63%) had reperforation. None of the patients showed retraction pocket or cholestetoma. Postoperative hearing was accessed 6 months after surgery. Patients with temporalis fascia graft showed an air bone gap of less than 10 dB in 49 (82%) patients and more than 10 dB in 11 (18%) patients. Air bone gap closure with tragal cartilage perichondrium was less than 10 dB in 45 (78%) patients and more than 10 dB in 13 patients (22%). Tragal cartilage perichondrium (<0.5 mm) seems to be an ideal graft material for tympanic membrane in terms of postoperative healing and acoustic properties. It can easily withstand negative middle ear pressure which may have contributed to the development of otitis media and significantly affect healing outcomes in postoperative period. Tragal cartilage being composed of collagen type II is also physiologically similar to the nature of the tympanic membrane.

The early events in the healing of laser-produced tympanic membrane perforation

CONCLUSION

An immense keratinocyte activity with high cell turnover produced keratin that was delivered to span the perforation. The perforation size did not define the time to closure.

OBJECTIVES

Most tympanic membrane perforations heal spontaneously, whereas a fraction remains patent. A simple, nonsurgical cure for chronic perforations is required. Better understanding of the healing processes might enable the development of a simple medical cure. Therefore the structural events of the healing process were investigated, as well as its dynamics, by comparing perforation size with time to closure.

METHODS

Twenty-four Sprague-Dawley rats were myringotomized with a KTP laser. Different perforation sizes were produced. The 'early closing picture' was assessed with otomicroscopy and light and transmission electron microscopy at between 1 h and 2 weeks after myringotomy and perforation size was monitored until closure.

RESULTS

In all, 40% of the perforations were closed after 8 days and 89% at 12 days. The closing time did not directly correlate with perforation size. A wave of keratinocytes migrates towards the perforation site and disintegrates to form a keratin mass that eventually spans the perforation. A less intense activity is present near the annulus. The origin of the epithelial migration is probably regenerative centers.