Outlook for Tissue Engineering of the Tympanic Membrane

Manufacturing Radially Aligned PCL Nanofibers Reinforced With Sulfated Levan and Evaluation of its Biological Activity for Healing Tympanic Membrane Perforations

The main objective of this study is to construct radially aligned PCL nanofibers reinforced with levan polymer and investigate their in vitro biological activities thoroughly. First Halomonas levan (HL) polysaccharide is hydrolyzed (hHL) and subjected to sulfation to attain Sulfated hydrolyzed Halomonas levan (ShHL)-based material indicating heparin mimetic properties. Then, optimization studies are carried out to produce coaxially generated radially aligned Poly(caprolactone) (PCL) -ShHL nanofibers via electrospinning. The obtained nanofibers are characterized with Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray (FESEM-EDX) analysis, and mechanical, contact angle measurement, biodegradability, and swelling tests as well. Afterward, cytotoxicity of artificial tympanic membranes is analyzed by MTT (3-(4,5-Dimethylthiazol-2-yl) -2,5 Diphenyltetrazolium Bromide) test, and their impacts on cell proliferation, cellular adhesion, wound healing processes are explored. Furthermore, an additional FESEM imaging is performed to manifest the interactions between fibroblasts and nanofibers. According to analytical measurements it is detected that PCL-ShHL nanofibers i) are smaller in fiber diameter, ii) are more biodegradable, iii) are more hydrophilic, and iv) demonstrated superior mechanical properties compared to PCL nanofibers. Moreover, it is also deciphered that PCL-ShHL nanofibers strongly elevated cellular adhesion, proliferation, and in vitro wound healing features compared to PCL nanofibers. According to obtained results it is assumed that newly synthetized levan and PCL mediated nanofibers are very encouraging for healing tympanic membrane perforations.

Polyacrylamide/Gel-Based Self-Healing Artificial Tympanic Membrane for Drug Delivery of Otitis Treatment

One of the bacterial infections caused by tympanic membrane perforation is otitis media (OM). Middle ear inflammation causes continuous pain and can be accompanied by aftereffects such as facial nerve paralysis if repeated chronically. Therefore, it is necessary to develop an artificial tympanic membrane (TM) that can effectively regenerate the eardrum due to the easy implantation and removal of OM inflammation. In this study, we synthesized hydrogel by mixing gelatin and polyacrylamide. Cefuroxime sodium salt was then incorporated into this hydrogel to both regenerate the TM and treat OM. Cytotoxicity experiments confirmed the biocompatibility of hydrogels equipped with antibiotics, and we conducted drug release and antibacterial experiments to examine continuous drug release. Through experiments, we have verified the excellent biocompatibility, drug release ability, and antibacterial effectiveness of hydrogel. It holds the potential to serve as an effective strategy for treating OM and regenerating TM as a drug delivery substance.

Antimicrobial poly (1,4-butylene carbonate): Preparation, characterization, and potential applications as a material for tympanic membrane repair

Perforation of the tympanic membrane (TM) is a common condition that often requires a scaffold as a support for surgery. However, because of the external environment of the auditory canal, the scaffold could become bacterially infected and prevent the TM from healing. As a result, the perfect scaffold should have both antibacterial and biomimetic qualities. In this study, the biodegradable biomaterial poly(1,4-butylene carbonate) (PBC) films containing levofloxacin (LEV) was successfully prepared for the first time. The results showed that the hydrophilicity of the LEV/PBC film was improved after the addition of LEV, and the tensile strength was also complied with the requirements of the standard. The created antibacterial film demonstrated excellent antibacterial properties. In vitro hemolysis experiments revealed no risk of hemolysis for the new material, and the cytotoxicity study further confirmed its non-cytotoxic nature. Overall, LEV was a good component of PBC/LEV film, which is expected to be used for TM repair in the future.

Three-Dimensional-Printed GelMA-KerMA Composite Patches as an Innovative Platform for Potential Tissue Engineering of Tympanic Membrane Perforations

Tympanic membrane (TM) perforations, primarily induced by middle ear infections, the introduction of foreign objects into the ear, and acoustic trauma, lead to hearing abnormalities and ear infections. We describe the design and fabrication of a novel composite patch containing photocrosslinkable gelatin methacryloyl (GelMA) and keratin methacryloyl (KerMA) hydrogels. GelMA-KerMA patches containing conical microneedles in their design were developed using the digital light processing (DLP) 3D printing approach. Following this, the patches were biofunctionalized by applying a coaxial coating with PVA nanoparticles loaded with gentamicin (GEN) and fibroblast growth factor (FGF-2) with the Electrohydrodynamic Atomization (EHDA) method. The developed nanoparticle-coated 3D-printed patches were evaluated in terms of their chemical, morphological, mechanical, swelling, and degradation behavior. In addition, the GEN and FGF-2 release profiles, antimicrobial properties, and biocompatibility of the patches were examined in vitro. The morphological assessment verified the successful fabrication and nanoparticle coating of the 3D-printed GelMA-KerMA patches. The outcomes of antibacterial tests demonstrated that GEN@PVA/GelMA-KerMA patches exhibited substantial antibacterial efficacy against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Furthermore, cell culture studies revealed that GelMA-KerMA patches were biocompatible with human adipose-derived mesenchymal stem cells (hADMSC) and supported cell attachment and proliferation without any cytotoxicity. These findings indicated that biofunctional 3D-printed GelMA-KerMA patches have the potential to be a promising therapeutic approach for addressing TM perforations.

Collagen Matrix to Restore the Tympanic Membrane: Developing a Novel Platform to Treat Perforations

Modern otology faces challenges in treating tympanic membrane (TM) perforations. Instead of surgical intervention, alternative treatments using biomaterials are emerging. Recently, we developed a robust collagen membrane using semipermeable barrier-assisted electrophoretic deposition (SBA-EPD). In this study, a collagen graft shaped like a sponge through SBA-EPD was used to treat acute and chronic TM perforations in a chinchilla model. A total of 24 ears from 12 adult male chinchillas were used in the study. They were organized into four groups. The first two groups had acute TM perforations and the last two had chronic TM perforations. We used the first and third groups as controls, meaning they did not receive the implant treatment. The second and fourth groups, however, were treated with the collagen graft implant. Otoscopic assessments were conducted on days 14 and 35, with histological evaluations and TM vibrational studies performed on day 35. The groups treated with the collagen graft showed fewer inflammatory changes, improved structural recovery, and nearly normal TM vibrational properties compared to the controls. The porous collagen scaffold successfully enhanced TM regeneration, showing high biocompatibility and biodegradation potential. These findings could pave the way for clinical trials and present a new approach for treating TM perforations.

Chronic tympanic membrane perforation repair with a collagen-based scaffold: An in vivo model

OBJECTIVE

The aim of this study was to assess the in vivo efficacy of a novel regenerative collagen-based scaffold developed by the Royal College of Surgeons in Ireland in a chronic tympanic membrane perforation (TMP) using a chinchilla model.

METHODS

Bilateral TMPs were induced in 17 mixed gender chinchillas using tympanic membrane resection followed by a mixture of topical Mitomycin C and dexamethasone for 3 days. These were monitored with weekly otoscopy for 8 weeks. Animals were excluded if signs of infection developed in the follow up period (n = 8). At 8 weeks, intervention began and 18 TMPs were assigned to either treatment with the collagen-based scaffold (treated group) or spontaneous healing (control group). Animals were euthanized 6 weeks post-intervention. Otoscopic imaging and auditory brain response (ABR) were conducted at baseline, 8 weeks post-TMP induction and 6 weeks post-intervention. All TMPs were then evaluated at 6 weeks post-intervention and bullae underwent histologic evaluation.

RESULTS

At 6 weeks post-intervention, otoscopic imaging demonstrated various degrees of healing in the treated ears. The treated group was noted to have an increased rate of healing when compared to the control group. Histologic evaluation demonstrated a variation in the degree of perforation healing within groups, with some animals in the treated group showing high levels of perforation healing. At 8 weeks after the TMP procedure, most of the animals had worsened hearing response. At 6-week post the collagen-based scaffold treatment, about 50 % (4/8) of the treated ears had improved in hearing response as compared to those of non-treated ears.

CONCLUSION

Given the initial histologic evidence of partial healing in scaffold-treated ears, the post-intervention period should be extended to monitor the potential for complete healing. Given the overall positive findings related to healing with the scaffold-treated ears, this material warrants further investigation.

Overcoming barriers: a review on innovations in drug delivery to the middle and inner ear

Despite significant advances in the development of therapeutics for hearing loss, drug delivery to the middle and inner ear remains a challenge. As conventional oral or intravascular administration are ineffective due to poor bioavailability and impermeability of the blood-labyrinth-barrier, localized delivery is becoming a preferable approach for certain drugs. Even then, localized delivery to the ear precludes continual drug delivery due to the invasive and potentially traumatic procedures required to access the middle and inner ear. To address this, the preclinical development of controlled release therapeutics and drug delivery devices have greatly advanced, with some now showing promise clinically. This review will discuss the existing challenges in drug development for treating the most prevalent and damaging hearing disorders, in particular otitis media, perforation of the tympanic membrane, cholesteatoma and sensorineural hearing loss. We will then address novel developments in drug delivery that address these including novel controlled release therapeutics such as hydrogel and nanotechnology and finally, novel device delivery approaches such as microfluidic systems and cochlear prosthesis-mediated delivery. The aim of this review is to investigate how drugs can reach the middle and inner ear more efficiently and how recent innovations could be applied in aiding drug delivery in certain pathologic contexts.

Multimodal additive manufacturing of biomimetic tympanic membrane replacements with near tissue-like acousto-mechanical and biological properties

The three additive manufacturing techniques fused deposition modeling, gel plotting and melt electrowriting were combined to develop a mimicry of the tympanic membrane (TM) to tackle large TM perforations caused by chronic otitis media. The mimicry of the collagen fiber orientation of the TM was accompanied by a study of multiple funnel-shaped mimics of the TM morphology, resulting in mechanical and acoustic properties similar to those of the eardrum. For the different 3D printing techniques used, the process parameters were optimized to allow reasonable microfiber arrangements within the melt electrowriting setup. Interestingly, the fiber pattern was less important for the acousto-mechanical properties than the overall morphology. Furthermore, the behavior of keratinocytes and fibroblasts is crucial for the repair of the TM, and an in vitro study showed a high biocompatibility of both primary cell types while mimicking the respective cell layers of the TM. A simulation of the in vivo ingrowth of both cell types resulted in a cell growth orientation similar to the original collagen fiber orientation of the TM. Overall, the combined approach showed all the necessary parameters to support the growth of a neo-epithelial layer with a similar structure and morphology to the original membrane. It therefore offers a suitable alternative to autologous materials for the treatment of chronic otitis media. STATEMENT OF SIGNIFICANCE: Millions of people worldwide suffer from chronic middle ear infections. Although the tympanic membrane (TM) can be reconstructed with autologous materials, the grafts used for this purpose require extensive manual preparation during surgery. This affects not only the hearing ability but also the stability of the reconstructed TM, especially in the case of full TM reconstruction. The synthetic alternative presented here mimicked not only the fibrous structure of the TM but also its morphology, resulting in similar acousto-mechanical properties. Furthermore, its high biocompatibility supported the migration of keratinocytes and fibroblasts to form a neo-epithelial layer. Overall, this completely new TM replacement was achieved by combining three different additive manufacturing processes.

Application of Silk-Fibroin-Based Hydrogels in Tissue Engineering

Silk fibroin (SF) is an excellent protein-based biomaterial produced by the degumming and purification of silk from cocoons of the Bombyx mori through alkali or enzymatic treatments. SF exhibits excellent biological properties, such as mechanical properties, biocompatibility, biodegradability, bioabsorbability, low immunogenicity, and tunability, making it a versatile material widely applied in biological fields, particularly in tissue engineering. In tissue engineering, SF is often fabricated into hydrogel form, with the advantages of added materials. SF hydrogels have mostly been studied for their use in tissue regeneration by enhancing cell activity at the tissue defect site or counteracting tissue-damage-related factors. This review focuses on SF hydrogels, firstly summarizing the fabrication and properties of SF and SF hydrogels and then detailing the regenerative effects of SF hydrogels as scaffolds in cartilage, bone, skin, cornea, teeth, and eardrum in recent years.

The impact of adding platelet-rich plasma during fat graft myringoplasty for managing medium-sized tympanic membrane perforations: A prospective randomized case-control study

PURPOSE

This study aimed to evaluate the effect of adding platelet-rich plasma (PRP) during FGM to close medium-sized TM perforations.

METHODS

This prospective randomized case-control study was conducted from February 2017 to March 2022. We included 320 patients with a medium-sized TM perforation with inactive mucosal otitis media. Transcanal FGM managed all patients under general or local anesthesia according to the patient preference. According to PRP, patients were divided into two groups: the first with PRP (170 patients) and the other without PRP (150 patients). We evaluated the closure rate of both groups one month, six months, and one year after the surgery. Also, we assessed the audiological performance before and one year after the operation for the patients with a successful closure.

RESULTS

The closure rate was 87.6 % in the first group and 72.7 % in the second group, with a statistically significant difference between both groups as the P-value, was 0.001. Successful closure of the ABG to <10 dB occurred in 95.3 % of group A and 90.8 % of group B without a statistically significant difference between both groups (P-value = 0.163).

CONCLUSIONS

This prospective comparative study on a relatively large number of patients revealed that FGM effectively closed medium-sized TM perforations. It also significantly improved postoperative audiological performance in both groups. Adding PRP during the FGM enhanced the closure success and the healing process without recorded complications. We recommend using the PRP in the routine FGM for closing medium-sized TM perforations.

3D printing technology and applied materials in eardrum regeneration

Tympanic membrane perforation is a common condition in clinical otolaryngology. Although some eardrum patients can self-heal, a long period of non-healing perforation leads to persistent otitis media, conductive deafness, and poor quality of life. Tympanic membrane repair with autologous materials requires a second incision, and the sampling site may get infected. It is challenging to repair tympanic membranes while maintaining high functionality, safety, affordability, and aesthetics. 3D bioprinting can be used to fabricate tissue patches with materials, factors, and cells in a design manner. This paper reviews 3D printing technology that is being used widely in recent years to construct eardrum stents and the utilized applied materials for tympanic membrane repair. The paper begins with an introduction of the physiological structure of the tympanic membrane, briefly reviews the current clinical method thereafter, highlights the recent 3D printing-related strategies in tympanic membrane repair, describes the materials and cells that might play an important role in 3D printing, and finally provides a perspective of this field.

Interfacing Perforated Eardrums with Graphene-Based Membranes for Broadband Hearing Recovery

Eardrum perforation and associated hearing loss is a global health problem. Grafting perforated eardrum with autologous tissues in clinic can restore low-frequency hearing but often leaves poor recovery of high-frequency hearing. In this study, the potential of incorporating a thin multilayered graphene membrane (MGM) into the eardrum for broadband hearing recovery in rats is examined. The MGM shows good biocompatibility and biostability to promote the growth of eardrum cells in a regulated manner with little sign of tissue rejection and inflammatory response. After three weeks of implantation, the MGM is found to be encapsulated by a thin layer of newly grown tissue on both sides without a significant folded overgrowth that is often seen in natural healing. The perforation is well sealed, and broadband hearing recovery (1-32 kHz) is enabled and maintained for at least 2 months. Mechanical simulations show that the high elastic modulus of MGM and thin thickness of the reconstructed eardrum play a critical role in the recovery of high-frequency hearing. This work demonstrates the promise of the use of MGM as a functional graft for perforated eardrum to recover hearing in the broadband frequency region and suggests a new acoustics-related medical application for graphene-related 2D materials.

An Evaluation of the Drug Permeability Properties of Human Cadaveric In Situ Tympanic and Round Window Membranes

It is estimated that hearing loss currently affects more than 1.5 billion people, or approximately 20% of the global population; however, presently, there are no Food and Drug Administration-approved therapeutics or prophylactics for this condition. While continued research on the development of otoprotective drugs to target this clear unmet need is an obvious path, there are numerous challenges to translating promising therapeutic candidates into human clinical testing. The screening of promising drug candidates relies exclusively on preclinical models. Current models do not permit the rapid high-throughput screening of promising drug candidates, and their relevance to clinical scenarios is often ambiguous. With the current study, we seek to understand the drug permeability properties of the cadaveric tympanic and round window membranes with the goal of generating knowledge that could inform the design and/or evaluation of in vitro organotypic models. The development of such models could enable the early high-throughput screening of topical therapeutic candidates and should address some of the limitations of currently used animal models.

Fabrication strategies and biomedical applications of three-dimensional bacterial cellulose-based scaffolds: A review

Bacterial cellulose (BC), an extracellular polysaccharide, is a versatile biopolymer due to its intrinsic physicochemical properties, broad-spectrum applications, and remarkable achievements in different fields, especially in the biomedical field. Presently, the focus of BC-related research is on the development of scaffolds containing other materials for in-vitro and in-vivo biomedical applications. To this end, prime research objectives concern the biocompatibility of BC and the development of three-dimensional (3D) BC-based scaffolds. This review summarizes the techniques used to develop 3D BC scaffolds and discusses their potential merits and limitations. In addition, we discuss the various biomedical applications of BC-based scaffolds for which the 3D BC matrix confers desired structural and conformational features. Overall, this review provides comprehensive coverage of the idea, requirements, synthetic strategies, and current and prospective applications of 3D BC scaffolds, and thus, should be useful for researchers working with polysaccharides, biopolymers, or composite materials.

Development of electrospun, biomimetic tympanic membrane implants with tunable mechanical and oscillatory properties for myringoplasty

Most commonly, autologous grafts are used in tympanic membrane (TM) reconstruction. However, apart from the limited availability and the increased surgical risk, they cannot replicate the full functionality of the human TM properly. Hence, biomimetic synthetic TM implants have been developed in our project to overcome these drawbacks. These innovative TM implants are made from synthetic biopolymer polycaprolactone (PCL) and silk fibroin (SF) by electrospinning technology. Static and dynamic experiments have shown that the mechanical and oscillatory behavior of the TM implants can be tuned by adjusting the solution concentration, the SF and PCL mixing ratio and the electrospinning parameters. In addition, candidates for TM implants could have comparable acousto-mechanical properties to human TMs. Finally, these candidates were further validated in in vitro experiments by performing TM reconstruction in human cadaver temporal bones. The reconstructed TM with SF-PCL blend membranes fully recovered the acoustic vibration when the perforation was smaller than 50%. Furthermore, the handling, medium adhesion and transparency of the developed TM implants were similar to those of human TMs.

Tissue engineering and regenerative medicine strategies for the repair of tympanic membrane perforations

Despite the high success rate of autologous grafts in tympanic membrane repair, clinical alternatives are required for the closure of unresponsive chronic perforations that can lead to recurring infection and hearing loss. Tissue engineering and regenerative medicine approaches have emerged as another strategy to repair the eardrum, in addition to negating the need for donor tissue harvest and related surgical iatrogenicities. This review highlights the main approaches using biomaterials, growth factors, and cell therapies towards the healing of complex TM perforations. In addition, we discuss the challenges and advances for the development of reliable animal models, which will allow the optimisation and development of novel techniques. Finally, we indicate technologies that are currently used clinically and others that are closer to the market. The advances here discussed on tissue engineering and regenerative medicine strategies applied to the field of TM perforations will allow otologists, surgeons, and researchers to better bring novel technologies to the bedside as well as to develop new ones.

The Dorsal Skinfold Chamber as a New Tympanic Membrane Wound Healing Model: Intravital Insights into the Pathophysiology of Epithelialized Wounds

BACKGROUND

Tympanic membrane perforations (TMPs) are a common complication of trauma and infection. Persisting perforations result from the unique location of the tympanic membrane. The wound is surrounded by air of the middle ear and the external auditory canal. The inadequate wound bed, growth factor, and blood supply lead to circular epithelialization of the perforation's edge and premature interruption of defect closure. Orthotopic animal models use mechanical or chemical tympanic membrane laceration to identify bioactive wound dressings and overcome premature epithelialization. However, all orthotopic models essentially lack repetitive visualization of the biomaterial-wound interface. Therefore, recent progress in 3D printing of customized wound dressings has not yet been transferred to the unique wound setup of the TMP. Here, we present a novel application for the mice dorsal skinfold chamber (DSC) with an epithelialized full-thickness defect as TMP model.

METHODS

A circular 2-mm defect was cut into the extended dorsal skinfold using a biopsy punch. The skinfold was either perforated through both skin layers without prior preparation or perforated on 1 side, following resection of the opposing skin layer. In both groups, the wound was sealed with a coverslip or left unclosed (n = 4). All animals were examined for epithelialization of the edge (histology), size of the perforation (planimetry), neovascularization (repetitive intravital fluorescence microscopy), and inflammation (immunohistology).

RESULTS

The edge of the perforation was overgrown by the cornified squamous epithelium in all pre-parations. Reduction in the perforation's size was enhanced by application of a coverslip. Microsurgical preparation before biopsy punch perforation and sealing with a coverslip enabled repetitive high-quality intravital fluorescence microscopy. However, spontaneous reduction of the perforation occurred frequently. Therefore, the direct biopsy punch perforation without microsurgical preparation was favorable: spontaneous reduction did not occur throughout 21 days. Moreover, the visualization of the neovascularization was sufficient in intravital microscopy.

CONCLUSIONS

The DSC full-thickness defect is a valuable supplement to orthotopic TMP models. Repetitive intravital microscopy of the epithelialized edge enables investigation of the underlying pathophysiology during the transition from the inflammation to the proliferation phase of wound healing. Using established analysis procedures, the present model provides an effective platform for the screening of bioactive materials and transferring progress in tissue engineering to the special conditions of tympanic membrane wound healing.

Regenerative Therapy Using Umbilical Cord Serum

Regenerative medicine is a branch of medicine that incorporates tissue-engineering, biomaterials, and cell therapy approaches to replace or repair damaged cells and tissues. Umbilical cord serum (UCS) is an important liquid component of cord blood, which has a reliable source of innumerable growth factors and biologically active molecules. Usually, serum can be prepared from different sources of blood. In therapeutic application, cord serum can be prepared and used in the form of eye drops for the treatment of severe dry eye diseases, ocular burns, glaucoma, persistent corneal epithelial defects and neurotrophic keratitis. In addition, cord serum combined with synthetic bio scaffold materials is used to regenerate different types of tissues including tympanic membrane regeneration, bone regeneration and nerve regeneration. Absence of animal origin viruses and bacteria, lack of xenoproteins and cost-effective features make cord serum a feasible choice as replacement of fetal bovine serum in cell culture techniques. Thus, this review emphasizes the role of cord serum in regenerative therapy and clinical uses.

Can Tissue Engineering Bring Hope to the Development of Human Tympanic Membrane?

The tympanic membrane (TM), more commonly known as the eardrum, consists of a thin layer of tissue in the human ear that receives sound vibrations from outside of the body and transmits them to the auditory ossicles. The TM perforations (TMPs) are a common ontological condition, which in some cases can result in permanent hearing loss. Despite the spontaneous healing capacity of the TM to regenerate in the majority of cases of acute perforation, chronic perforations require surgical interventions. However, the disadvantages of the surgical procedure include infection, anesthetic risks, and high failure of graft patency. The tissue engineering strategy, which includes the applications of a three-dimensional (3D) scaffold, cells, and biomolecules or a combination of them for the closure of chronic perforation, has been considered as an emerging treatment. Using this approach, emerging products are currently under development to regenerate the TM structure and its properties. This research aimed to highlight the problems with the current methods of TMP treatment, and critically evaluate the tissue engineering approaches, which may overcome these drawbacks. The focus of this review is on recent literature to critically discuss the emerging advanced materials used as a 3D scaffold in the development of a TM with cellular engineering, biomolecules, cells, and the fabrications of the TM and its pathway to the clinical application. In this review, we discuss the properties of TM and the advantages and disadvantages of the current clinical products for repair and replacement of the TM. Furthermore, we provide an overview of the in vitro and preclinical studies of emerging products over the past 5 years. The results of recent preclinical studies suggest that the tissue engineering field holds significant promise.

Silk Fibroin as a Functional Biomaterial for Tissue Engineering

Tissue engineering (TE) is the approach to combine cells with scaffold materials and appropriate growth factors to regenerate or replace damaged or degenerated tissue or organs. The scaffold material as a template for tissue formation plays the most important role in TE. Among scaffold materials, silk fibroin (SF), a natural protein with outstanding mechanical properties, biodegradability, biocompatibility, and bioresorbability has attracted significant attention for TE applications. SF is commonly dissolved into an aqueous solution and can be easily reconstructed into different material formats, including films, mats, hydrogels, and sponges via various fabrication techniques. These include spin coating, electrospinning, freeze drying, physical, and chemical crosslinking techniques. Furthermore, to facilitate fabrication of more complex SF-based scaffolds with high precision techniques including micro-patterning and bio-printing have recently been explored. This review introduces the physicochemical and mechanical properties of SF and looks into a range of SF-based scaffolds that have been recently developed. The typical TE applications of SF-based scaffolds including bone, cartilage, ligament, tendon, skin, wound healing, and tympanic membrane, will be highlighted and discussed, followed by future prospects and challenges needing to be addressed.

Comparative efficacy of platelet-rich plasma applied in myringoplasty: A systematic review and meta-analysis

BACKGROUND

Tympanic membrane (TM) perforation is quite common in the clinical setting. Chronic TM perforations require surgical treatments such as myringoplasty. Currently, platelet-rich plasma (PRP) is a novel, effective substance that is increasingly utilized for TM perforation repair. This study aims to evaluate the effectiveness of PRP in the application of TM perforation repair.

METHODS

A systematic search was conducted to screen the Medline, Embase, Cochrane, Scopus and Web of Science databases up to July 2020. Studies were identified in accordance with the selection criteria by two coauthors independently. Data regarding the healing and hearing outcomes were pooled and analyzed via Review Manager version 5.3 and STATA version 12.0 software. Odds ratio (OR) was utilized to compare the closure rate. Furthermore, the results of hearing improvements and incidence of complications were also compared to evaluate the effectiveness of PRP.

RESULTS

A total of eight studies with 455 participants were eligible according to the selection criteria. Compared to conventional surgery, the OR of closure was 2.70 (95% CI: 1.27 to 5.76, P = 0.01, I2 = 0%) in randomized controlled trial (RCT) subgroup and 6.18 (95% CI: 2.22 to 17.25, P = 0.0005, I2 = 0) in non-RCT subgroup. The overall OR of closure was 3.69 (95% CI: 2.02 to 6.74, P<0.0001, I2 = 0%), suggesting a significant effect on the healing of TM perforation. Between preoperative and postoperative hearing results, there is no statistical difference between the PRP and the control groups. Additionally, the use of PRP resulted in a lower incidence of complication than the use of conventional approaches.

CONCLUSION

The application of PRP during the TM surgeries can enhance the closure rate, provide similar hearing improvements and decrease the incidence of postoperative complications. Given these advantages, PRP can be considered an effective treatment for TM regeneration.

[Experimental evidence for regenerative treatment of chronic tympanic membrane perforation]

OBJECTIVE

The aim of our study was an experimental evaluation of tissue engineering approach to chronic tympanic membrane perforation closure.

MATERIALS AND METHODS

Chronic tympanic membrane perforation models were created both sides in 12 chinchillas. Right sided perforations were divided into two equal groups (A and B) according to treatment; left sided perforations were used as a control group. Group A perforations were treated with collagen scaffold and fibroblast growth factor, group B perforations were treated with collagen scaffold only. During follow-up, we provided otovideoendoscopy for closure rates assessement every 2 weeks. In case of perforation closure, a morphological investigation of the regenerate was performed.

RESULTS

Group A perforations were totally closed 2 weeks after treatment in all animals. In group B, complete closure of perforation was achieved after the third treatment procedure in one case. There were no spontaneous perforation closure in the control group. According to morphological investigation, the restoration of trilaminar structure was observed only in tissue engineering group tympanic membranes.

Fabrication of tissue-engineered tympanic membrane patches using 3D-Printing technology

In recent years, scaffolds produced in 3D printing technology have become more widespread tool due to providing more advantages than traditional methods in tissue engineering applications. In this research, it was aimed to produce patches for the treatment of tympanic membrane perforations which caused significant hearing loss by using 3D printing method. Polylactic acid(PLA) scaffolds with Chitosan(CS) and Sodium Alginate(SA) added in various ratios were prepared for artificial eardrum patches. Different amounts of chitosan and sodium alginate added to PLA increased the biocompatibility of the produced scaffolds. The created patches were designed by mimicking the thickness of the natural tympanic membrane thanks to the precision provided by the 3D printed method. The produced scaffolds were analyzed separately for chemical, morphological, mechanical and biocompatibility properties. Scanning electron microscope (SEM), Fourier-transform infrared (FT-IR) spectroscopy was performed to observe the surface morphology and chemical structure of the scaffolds. Mechanical, thermal and physical properties, swelling and degradation behaviors were examined to fully analyze whole characteristic features of the samples. Cell culture study was also performed to demonstrate the biocompatibility properties of the fabricated scaffolds with human adipose tissue-derived mesenchymal stem cells (hAD-MSCs). 15 wt % PLA was selected as the control group and among all concentrations of CS and SA, groups containing 3 wt% CS and 3 wt% SA showed significantly superior and favorable features in printing quality. The research continued with these two scaffolds (3 wt% CS, and 3 wt% SA), which showed improved print quality when added to PLA. Overall, these results show that PLA/CS and PLA/SA 3D printed artificial patches have the potential to tissue engineering solutions to repair tympanic membrane perforation for people with hearing loss.

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.

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.

Advances in regenerative medicine for otolaryngology/head and neck surgery

Head and neck structures govern the vital functions of breathing and swallowing. Additionally, these structures facilitate our sense of self through vocal communication, hearing, facial animation, and physical appearance. Loss of these functions can lead to loss of life or greatly affect quality of life. Regenerative medicine is a rapidly developing field that aims to repair or replace damaged cells, tissues, and organs. Although the field is largely in its nascence, regenerative medicine holds promise for improving on conventional treatments for head and neck disorders or providing therapies where no current standard exists. This review presents milestones in the research of regenerative medicine in head and neck surgery.

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.

A Self-Adhesive Elastomeric Wound Scaffold for Sensitive Adhesion to Tissue

Pressure sensitive adhesives based on silicone materials are used particularly for skin adhesion, e.g., the fixation of electrocardiogram (ECG) electrodes or wound dressings. However, adhesion to sensitive tissue structures is not sufficiently addressed due to the risk of damage or rupture. We propose an approach in which a poly-(dimethylsiloxane) (PDMS)-based soft skin adhesive (SSA) acts as cellular scaffold for wound healing. Due to the intrinsically low surface free energy of silicone elastomers, functionalization strategies are needed to promote the attachment and spreading of eukaryotic cells. In the present work, the effect of physical adsorption of three different proteins on the adhesive properties of the soft skin adhesive was investigated. Fibronectin adsorption slightly affects adhesion but significantly improves the cellular interaction of L929 murine fibroblasts with the polymeric surface. Composite films were successfully attached to explanted tympanic membranes. This demonstrates the potential of protein functionalized SSA to act as an adhesive scaffold in delicate biomedical applications.

[Regeneration - A New Therapeutic Dimension in Otorhinolaryngology]

Regeneration as a therapeutic priniciple and regenerative medicine in general are promising new strategies to add new therapeutic dimensions to our current treatment options. Today, reconstructive surgery, drugs and implants such as the cochlear implant can replace the functions of damaged tissues. In contrast, regenerative therapies aim at the replacement of the damaged tissues themselves while at the same time replacing their lost tissue function. In this review article new technologies such as 3D-bioprinting and the application of decellularised tissues as biomaterials are introduced and explained. A summary of current preclinical and clinical regenerative studies in otorhinolaryngology is complementing these basic aspects.

Randomized Clinical Trial Comparing Bucket Handle and Cartilage Tympanoplasty Techniques for the Reconstruction of Subtotal or Anterior Tympanic Membrane Perforation

OBJECTIVE

The purpose of the study is to compare the clinical outcome of the two techniques of Bucket Handle Tympanoplasty and Cartilage Tympanoplasty in achieving success in graft survival as well as acceptable auditory results. 60 patients who suffered chronic otitis media with anterior perforation of the tympanic membrane were chosen. The patients were randomly assigned using Block Randomization Method of two groups including patients who underwent Bucket Handle Tympanoplasty (n = 30) or those that underwent Cartilage Tympanoplasty (n = 30). The patients were followed up for 1, 3, 6, and 12 months postoperatively.

RESULTS

The mean PTA was lower in Bucket Handle Tympanoplasty group as case group compared to Cartilage Tympanoplasty group as the control (P = 0.023). No significant statistical differences had identified passing through the time, in terms of PTA outcome (P Value = 0.547) and SRT outcome (P Value = 0.352), between Bucket Handle Tympanoplasty group and the Cartilage Tympanoplasty group. In total, postoperative tympanic membrane perforation was found in 10.0% of patients in Cartilage Tympanoplasty group and 13.3% in Bucket Handle Tympanoplasty group with no difference (P = 0.500).

CONCLUSIONS

Hearing improvements in both methods were similar.

REGISTRATION NUMBER

The trial is registered with IRCT2016022626773N1.

Efficacy of Platelet-Rich Plasma on Fat Grafts in the Repair of Tympanic Membrane Perforations: An Experimental Study

OBJECTIVE

We investigated the use of autologous platelet-rich plasma (PRP) to improve the success rate of fat graft myringoplasty in perforated tympanic membranes of rats.

MATERIALS AND METHODS

A total of 20 healthy Wistar albino female rats were divided into two groups. In Group 1, the left tympanic membranes were perforated and grafted with a fat graft that was harvested from the inguinal region. In Group 2, the left tympanic membranes were perforated, and a fat graft was also harvested from the inguinal region. Then, the fat was soaked in 0.5 mL PRP and grafted at the perforation. After the procedure, the rats were examined, and the graft situation was assessed at 3, 5, 7, 10, and 14 days. All of the rats were sacrificed 21 days after perforation, and a histopathological examination was made.

RESULTS

We compared fat graft histopathological and otomicroscopic findings between the groups. While we did not observe graft rejections in Group 2, we saw 1 case of graft rejection in Group 1. In the histopathological examination, PRP prevents fat graft resorption by the terms of the adipocyte area, granulation tissue area, and vacuolization area.

CONCLUSION

This study demonstrated the efficacy of fat grafts prepared with PRP on rat tympanic membranes. The fat graft with PRP did not statistically improve the success rate compared to the graft without PRP. Histopatologic findings of the study showed that PRP prevents fat graft resorption. Further studies are needed to further examine the advantages of the graft with PRP.

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.