Delay of tympanic membrane wound healing in rats with topical application of a tyrosine kinase inhibitor

Comparison of the effects of human fetal umbilical cord-derived hyaluronic acid and fibroblast-derived exosomes on wound healing in rats

INTRODUCTION

Exosomes and hyaluronic acid influence tissue regeneration and may be used as an alternative to more conventional wound treatment methods. This study compared how well hyaluronic acid from the human umbilical cord and exosomes from fibroblast cells heal burn wounds in a preclinical model.

METHODS

Ninety-six male Westar rats were used and allocated into four groups: The treatment group received 10% hyaluronic acid (HA); the treatment group received 300 l of exosome solution (EX); the treatment group received phenytoin (PC); the negative control group received no treatment (NC). The wound healing process was evaluated after 3, 6, 9, and 12 days. Histopathological analysis was done on the skin biopsy taken from the wounds. Re-epithelialization, inflammatory cells (PMNs), lymphocytes (LYMs), granulation tissue, collagen maturation (fibrosis), and eschar formation parameters were assessed for histopathological evaluation. On a scale from 0 to 4, each parameter received a score.

RESULTS

Compared to the PC and NC groups, the median score for re-epithelialization was greater in the HA and EX groups (P < 0.05). At three days, PMN abundance distinguished the PC and NC groups from the HA and EX groups (P < 0.01). Compared to the PC and NC groups, the HA and EX groups had a lower median LYM score (P < 0.01). We found no statistical difference between the four groups for granulation tissue and fibrosis (P > 0.05). The EX group had a lower average score for eschar formation than the PC, NC, and HA groups (P < 0.01). The HA and EX groups demonstrated faster healing in the clinical and microscopic examinations than the NC and PC groups.

CONCLUSION

The results showed that hyaluronic acid and exosomes improved wound healing. Also, the study demonstrated that hyaluronic acid has better effects in the re-epithelization. The exosome was more effective than HA in eschar formation. Both compounds were more influential in the PMNs and LYMs parameters than other groups. The combination of both compounds should be assessed further to achieve better therapeutic effects on wound healing.

Decellularized tympanic membrane scaffold with bone marrow mesenchymal stem cells for repairing tympanic membrane perforation

BACKGROUND

Tympanic membrane perforation (TMP) is a common disease in otology, and few acellular techniques have been reported for repairing this condition. Decellularized extracellular matrix (ECM) scaffolds have been used in organ reconstruction.

OBJECTIVE

This study on tissue engineering aimed to develop a tympanic membrane (TM) scaffold prepared using detergent immersion and bone marrow mesenchymal stem cells (BMSCs) as repair materials to reconstruct the TM.

RESULTS

General structure was observed that the decellularized TM scaffold with BMSCs retained the original intact anatomical ECM structure, with no cell residue, as observed using scanning electron microscopy (SEM), and exhibited low immunogenicity. Therefore, we seeded the decellularized TM scaffold with BMSCs for recellularization. Histology and eosin staining, SEM and immunofluorescence in vivo showed that the recellularized TM patch had a natural ultrastructure and was suitable for the migration and proliferation of BMSCs. The auditory brainstem response (ABR) evaluated after recellularized TM patch repair was slightly higher than that of the normal TM, but the difference was not significant.

CONCLUSION

The synthetic ECM scaffold provides temporary physical support for the three-dimensional growth of cells during the tissue developmental stage. The scaffold stimulates cells to secrete their own ECM required for tissue regeneration. The recellularized TM patch shows potential as a natural, ultrastructure biological material for TM reconstruction.

Functional Outcomes of Heparin-Binding Epidermal Growth Factor-Like Growth Factor for Regeneration of Chronic Tympanic Membrane Perforations in Mice

We aim to demonstrate that regeneration of chronic tympanic perforations with heparin-binding epidermal growth factor-like growth factor (HB-EGF) delivered by an injectable hydrogel restored hearing to levels similar to that of nonperforated tympanic membranes. Chronic tympanic membrane perforation is currently managed as an outpatient surgery with tympanoplasty. Due to the costs of this procedure in the developed world and a lack of accessibility and resources in developing countries, there is a great need for a new treatment that does not require surgery. In this study, we show in a mouse model through measurement of auditory brainstem response and distortion product otoacoustic emissions that tympanic perforations lead to hearing loss and this can be predominantly recovered with HB-EGF treatment (5 μg/mL). Our animal model suggests a return to function between 2 and 6 months after treatment. Auditory brainstem response thresholds had returned to the control levels at 2 months, but the distortion product otoacoustic emissions returned between 2 and 6 months. We also show how the vibration characteristics of the regenerated tympanic membrane, as measured by laser Doppler vibrometry, can be similar to that of an unperforated tympanic membrane. Using the best available methods for preclinical evaluation in animal models, it is likely that HB-EGF-like growth factor treatment leads to regeneration of chronic tympanic membrane perforations and restoration of the tympanic membrane to normal function, suggesting a potential route for nonsurgical treatment.

Heparin Binding Epidermal Growth Factor-Like Growth Factor Heals Chronic Tympanic Membrane Perforations With Advantage Over Fibroblast Growth Factor 2 and Epidermal Growth Factor in an Animal Model

HYPOTHESIS

That heparin binding epidermal growth factor-like growth factor (HB-EGF) heals chronic tympanic membrane (TM) perforations at higher rates than fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF) in an animal model.

BACKGROUND

A nonsurgical treatment for chronic TM perforation would benefit those unable to access surgery or those unable to have surgery, as well as reducing the cost of tympanoplasty. Growth factor (GF) treatments have been reported in the literature with variable success with the lack of a suitable animal providing a major obstacle.

METHODS

The GFs were tested in a validated mouse model of chronic TM perforation. A bioabsorbable hydrogel polymer was used to deliver the GF at a steady concentration as it dissolved over 4 weeks. A control (polymer only, n = 18) was compared to polymer loaded with HB-EGF (5 μg/ml, n = 18), FGF2 (100 μg/ml, n = 19), and EGF (250 μg/ml, n = 19). Perforations were inspected at 4 weeks.

RESULTS

The healing rates, as defined as 100% perforation closure, were control (5/18, 27.8%), HB-EGF (15/18, 83.3%), FGF2 (6/19, 31.6%), and EGF (3/19, 15.8%). There were no differences between FGF2 (p = 0.80) and EGF (p = 0.31) with control healing rates. HB-EGF (p = 0.000001) showed a significant difference for healing. The HB-EGF healed TMs showed layers similar to a normal TM, whereas the other groups showed a lack of epithelial migration.

CONCLUSION

This study confirms the advantage of HB-EGF over two other commonly used growth factors and is a promising nonsurgical treatment of chronic TM perforations.

Searching for a rat model of chronic tympanic membrane perforation: Healing delayed by mitomycin C/dexamethasone but not paper implantation or iterative myringotomy

OBJECTIVES

Surgical intervention such as myringoplasty or tympanoplasty is an option in the current clinical management of chronic tympanic membrane perforation (TMP). Animal models of chronic TMP are needed for pre-clinical testing of new materials and to improve existing techniques. We evaluated several reported animal model techniques from the literature for the creation of chronic TMPs. The aim of this study was to evaluate production of chronic TMPs in a rat model using topical mitomycin C/dexamethasone, paper insertion into middle ear cavity (MEC) or re-myringotomy.

METHODS

Forty male Sprague-Dawley rats underwent myringotomy of the right tympanic membrane (TM) and were randomly divided into 3 experimental groups: application of topical mitomycin C/dexamethasone, paper insertion into middle ear cavity, or re-myringotomy. Control perforations were allowed to close spontaneously. TMs were assessed regularly with otoscopy for 8 weeks. At the end of 8 weeks, animals were sacrificed for histology.

RESULTS

The closure of TMPs was significantly delayed by mitomycin C/dexamethasone (mean patency, 18.9 days; P≤0.01) compared with the control (mean patency, 7 days), but was not significantly delayed in the paper insertion group (mean patency, 9.4 days; P=0.74). Repeated myringotomy of closed perforations (mean number of myringotomies, 8.9 per ear) stimulated acceleration of closure rather than delay. Histologically, the mitomycin C/dexamethasone group had almost normal TM morphology, while the paper insertion group revealed inflammatory and granulomatous responses. The re-myringotomy group had a thickened TM fibrous layer with collagen deposition.

CONCLUSIONS

Mitomycin C/dexamethasone delayed TMP closure in rats but the effect was not sufficiently long-lasting to be defined as a chronic TMP. Neither paper insertion into middle ear cavity nor re-myringotomy created chronic TMP in rats.

Heparin binding-epidermal growth factor-like growth factor for the regeneration of chronic tympanic membrane perforations in mice

We aim to explore the role of epidermal growth factor (EGF) ligand shedding in tympanic membrane wound healing and to investigate the translation of its modulation in tissue engineering of chronic tympanic membrane perforations. Chronic suppurative otitis media (CSOM) is an infected chronic tympanic membrane perforation. Up to 200 million suffer from its associated hearing loss and it is the most common cause of pediatric hearing loss in developing countries. There is a need for nonsurgical treatment due to a worldwide lack of resources. In this study, we show that EGF ligand shedding is essential for tympanic membrane healing as it's inhibition, with KB-R7785, leads to chronic perforation in 87.9% (n=58) compared with 0% (n=20) of controls. We then show that heparin binding-EGF-like growth factor (5 μg/mL), which acts to shed EGF ligands, can regenerate chronic perforations in mouse models with 92% (22 of 24) compared with 38% (10 of 26), also with eustachian tube occlusion with 94% (18 of 19) compared with 9% (2 of 23) and with CSOM 100% (16 of 16) compared with 41% (7 of 17). We also show the nonototoxicity of this treatment and its hydrogel delivery vehicle. This provides preliminary data for a clinical trial where it could be delivered by nonspecialist trained healthcare workers and fulfill the clinical need for a nonsurgical treatment for chronic tympanic membrane perforation and CSOM.

Animal models of chronic tympanic membrane perforation: a 'time-out' to review evidence and standardize design

OBJECTIVE

To review the literature on techniques for creation of chronic tympanic membrane perforations (TMP) in animal models. Establishing such models in a laboratory setting will have value if they replicate many of the properties of the human clinical condition and can thus be used for investigation of novel grafting materials or other interventions.

METHODS

A literature search of the PubMed database (1950-August 2014) was performed. The search included all English-language literature published attempts on chronic or delayed TMP in animal models. Studies of non English-language or acute TMP were excluded.

RESULTS

Thirty-seven studies were identified. Various methods to create TMP in animals have been used including infolding technique, thermal injury, re-myringotomy, and topical agents including chemicals and growth factor receptor inhibitors. The most common type of animal utilized was chinchilla, followed by rat and guinea pig. Twenty three of the 37 studies reported success in achieving chronic TMP animal model while 14 studies solely delayed the healing of TMP. Numerous experimental limitations were identified including TMP patency duration of <8 weeks, lack of documentation of total number of animals attempted and absence of proof for chronicity with otoscopic and histologic evidence.

CONCLUSION

The existing literature demonstrates the need for an ideal chronic TMP animal model to allow the development of new treatments and evaluate the risk of their clinical application. Various identified techniques seem promising, however, a need was identified for standardization of experimental design and evidence to address multiple limitations.

Animal models of chronic tympanic membrane perforation: in response to plasminogen initiates and potentiates the healing of acute and chronic tympanic membrane perforations in mice

Tympanic membrane perforations (TMP) are relatively common but are typically not treated in their acute stage, as most will heal spontaneously in 7–10 days. Those cases which fail to heal within 3 months are called chronic TMP which attract surgical intervention (e.g. myringoplasty), typically with a temporalis fascia autograft. New materials for the repair of chronic TMP are being developed to address deficiencies in the performance of autografts by undergoing evaluation in animal models prior to clinical study. However, there is currently a lack of ideal chronic TMP animal models available, hindering the development of new treatments. Various techniques and animal species have been investigated for the creation of chronic TMP with varied success. In the present commentary, we bring to the attention of readers the recent report by Shen et al. in Journal of Translational Medicine. The study reported the creation of a chronic TMP animal model in plasminogen gene deficient mice. However, the short observation time (9, 19 days), lack of success rate and the scarcity of solid evidence (e.g. otoscopic & histologic images) to confirm the chronicity of TMP warrant a more thorough discussion.

Late crust formation as a predictor of healing of traumatic, dry, and minor-sized tympanic membrane perforations

OBJECTIVE

The goal of this study was to evaluate the effects of crust formation on the healing of traumatic, dry, and minor-sized tympanic membrane perforations (TMPs) in humans.

STUDY DESIGN

Case series with a chart review.

SETTING

Tertiary university hospital.

MATERIALS AND METHODS

The clinical records of patients with traumatic TMPs who met the case selection criteria were retrieved and categorized according to the presence of a crust and the timing of crust formation into three groups: no crust, early crust formation, and late crust formation. Healing outcomes (i.e., healing rate and time) in the three groups were analyzed.

RESULTS

In total, 83 patients were analyzed. The perforation closure rates were 92%, 100%, and 78% in the groups with no-crust, early crust formation, and late crust formation, respectively. No significant difference was seen between the groups with no-crust and with late crust formation (p>0.05). By contrast, closure rates differed significantly between the early and late crust formation groups (p<0.05). Overall, the no-crust and early crust formation groups showed shorter healing times compared with the late crust formation group (p<0.05). However, closure times did not differ significantly between groups with early crust formation and no crust (p>0.05).

CONCLUSIONS

Crust formation at the margin of a traumatic TMP may serve as a predictor of healing outcome. Compared with perforations with early crust formation or no crust, late crust formation can result in delayed healing and failure to close completely.

A comparison of epithelial-to-mesenchymal transition and re-epithelialization

Wound healing and cancer metastasis share a common starting point, namely, a change in the phenotype of some cells from stationary to motile. The term, epithelial-to-mesenchymal transition (EMT) describes the changes in molecular biology and cellular physiology that allow a cell to transition from a sedentary cell to a motile cell, a process that is relevant not only for cancer and regeneration, but also for normal development of multicellular organisms. The present review compares the similarities and differences in cellular response at the molecular level as tumor cells enter EMT or as keratinocytes begin the process of re-epithelialization of a wound. Looking toward clinical interventions that might modulate these processes, the mechanisms and outcomes of current and potential therapies are reviewed for both anti-cancer and pro-wound healing treatments related to the pathways that are central to EMT. Taken together, the comparison of re-epithelialization and tumor EMT serves as a starting point for the development of therapies that can selectively modulate different forms of EMT.

The influence of inhibition of the epidermal growth factor receptor on tympanic membrane wound healing in rats

Recently, a report on a bilateral tympanic membrane (TM) perforation in a patient after long-term treatment with erlotinib was published. The object of this study was to investigate the destructive potential of topical applied epidermal growth factor receptor (EGFR) inhibitors on wound healing of experimental TM perforation in rats by evaluating closure rates and histology. In 12 rats, erlotinib (10&#x00A0;mg/ml) was applied to one TM of each animal and cetuximab (5&#x00A0;mg/ml) to the other side daily for 12 consecutive days. Both the erlotinib group (11.8 days) and cetuximab group (9 days) had prolonged healing latencies compared to a reference value (7 days). We observed differences in the histologic parameters between both groups. Our results suggest that in normal TM, the inhibition of EGFR does not lead to a persistent perforation. However, in case of preexisting TM pathology, a spontaneous perforation in patients under long-term treatment of EGFR inhibitors seems to be possible.