Epidermal growth factor and basic fibroblast growth factor are induced in guinea-pig tympanic membrane following traumatic perforation

Thymosin beta-4 - A potential tool in healing middle ear lesions in adult mammals

Acute tympanic membrane perforations primarily occur due to injury or infection in humans. In acute cases, nearly 80-94 % of the perforations heal spontaneously. In chronic cases, non-surgical treatment becomes significantly limited, and the perforation can be restored only by myringoplasty. In addition to classical grafts such as the fascia or cartilage, promising results have been reported with various biological materials including silk or acellular collagen. However, despite of all the efforts, healing remains insufficient. Consequentially, a need for substances which actively promote tympanic cell migration and proliferation is deemed essential. In our study, we utilized Thymosin beta-4 (TB4), a 43aa peptide possessing many regenerative properties in various organ systems. Our aim was to reveal the impact of externally administered TB4 regarding impairments of the middle ear, particularly the tympanic membrane. We harvested tympanic membranes from adult mice and treated these with TB4 or PBS on both collagen gel matrixes and in the form of floating, ex vivo explants. Cell migration and proliferation was measured, while immunocytochemical analyses were performed to determine cell type and the nature of the targeted molecules. We discovered the peptide affects the behavior of epidermal and epithelial cells of the tympanic membrane in vitro. Moreover, as our initial results imply, it is not the differentiated, yet most likely the local epidermal progenitor cells which are the primary targets of the molecule. Our present results unveil a new, thus far undiscovered field regarding clinical utilization for TB4 in the future.

Histopathological Evaluation of Platelet-Rich Plasma Effect in Acute Tympanic Membrane Perforation

Platelet-rich plasma (PRP) is a reliable and has low side-effect profile and has beneficial effects on wound healing. Its investigatory effects on wound-healing process were shown on various tissues. This study aims to investigate PRP's local application effects to perforated rat TM in terms of healing and histopatological outcomes. Twenty-two Wistar rats were used in the study. The rats' ears were examined with a pediatric endoscope (2.7 mm, 0°), and the TM posterior quadrant of their right ear was perforated with a 20-gauge needle. After this procedure, the rats were divided into two equal groups. A spongel with PRP was applied on the perforated TM in the first group, and spongel with standard saline solution was applied on the second group. Following the sacrifice, the middle air bullas were carefully dissected and removed for histopathological examination. Hematoxylin eosin (for fibroblasts, lymphocyte, collagen fibers) and immunohistochemical staining were done for epithelial growth factor receptor (EGFR), fibroblast growth factor receptor (FGFR1), and vascular endothelial growth factor (VEGF) staining for histopathologic examinations. There was not a significant difference between the two groups for lymphocyte. There was a significant difference between control and study groups for collagen and EGFR (P < 0.05). Although the mean value of FGF- and VEGF-positive cells was higher in the study group than in the control group, the difference was not significant (P > 0.05). PRP is an effective autologous material for the healing process of acute TM perforations in a rat model, as demonstrated in the present study. We think that the use of PRP for acute TM perforations can have a positive effect on the healing process by increasing the level of growth factors, especially EGFR. In addition, an increase in collagen can also have a positive effect on healing.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-021-02912-2.

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

Objective

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

Methods

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

Results

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

Conclusions

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

Effect of Basic Fibroblast Growth Factor on Perforated Chinchilla Tympanic Membranes

Basic fibroblast growth factor (bFGF) is a polypeptide mitogen which stimulates proliferation of epidermal and connective tissue cells. When applied to tympanic membrane perforations it has been reported to enhance healing and produce connective tissue hyperplasia. Previous work with animal models has shown that hyperplastic alterations of the tympanic membrane play an essential role in cholesteatoma development. This study was designed to further investigate the hyperplastic effects of bFGF and to determine if it might induce cholesteatoma formation during the healing process.

Ten chinchillas received bilateral tympanic membrane perforations. In each animal, three doses of bFGF (400 nanograms per dose) were applied to the perforated tympanic membrane on one side; the opposite (control) ear received saline alone. The animals were terminated at either two or four weeks and studied histologically.

Although the dosage and administration schedule used were consistent with previous studies utilizing other rodent species, there was little evidence that bFGF affected tympanic membrane healing in chinchillas. In both control and bFGF-treated ears, dense connective tissue occupied the lamina propria of the tympanic membrane, providing an effective barrier against ingrowth of skin toward the middle ear. No cholesteatomas developed in any animals included in the study.

The results of this work indicate that the risk of cholesteatoma formation following administration of bFGF is minimal when it is applied short-term to acute perforations.

A moist edge environment aids the regeneration of traumatic tympanic membrane perforations

OBJECTIVE

To review the history of moist therapy used to regenerate traumatic tympanic membrane perforations.

STUDY DESIGN

Literature review.

METHODS

The literature on topical agents used to treat traumatic tympanic membrane perforations was reviewed, and the advantages and disadvantages of moist therapy were analysed.

RESULTS

A total of 76 studies were included in the analysis. Topical applications of certain agents (e.g. growth factors, Ofloxacin Otic Solution, and insulin solutions) to the moist edges of traumatic tympanic membrane perforations shortened closure times and improved closure rates.

CONCLUSION

Dry tympanic membrane perforation edges may be associated with crust formation and centrifugal migration, delaying perforation closure. On the contrary, moist edges inhibit necrosis at the perforation margins, stimulate proliferation of granulation tissue and aid eardrum healing. Thus, moist perforation margins upon topical application of solutions of appropriate agents aid the regeneration of traumatic tympanic membrane perforations.

Rat model of chronic tympanic membrane perforation: A longitudinal histological evaluation of underlying mechanisms

OBJECTIVE

To evaluate histologically the progressive development and underlying mechanisms of chronic tympanic membrane perforation (TMP) in a rat model using a two-weeks ventilation tube (VT) treatment combined with topical application of mitomycin C/dexamethasone (VT-M/D), compared with normal tympanic membrane and acute TMPs.

METHODS

Fifty male Sprague-Dawley rats were divided into three experimental groups: a normal control group (n = 5), an acute TMP group (n = 5) (i.e. 3 days post-myringotomy) and a VT-M/D group (n = 40). The TMs were regularly assessed by otoscopy. The normal control animals were sacrificed on day 0 and the acute TMP group was sacrificed 3 days post-myringotomy for histological and immunohistochemical evaluations. The VT-M/D group was sacrificed at various time points - 14 and 17 days, 3, 4, 6, 8 and 10 weeks.

RESULTS

On longitudinal histological examination, compared with normal TM and acute TMP, the perforation edges at the later time points illustrated thickened stratified squamous epithelium rimming around the edges, significant increase in keratin and collagen deposition, increased macrophage infiltration as well as reduced cellular proliferation. Three phases of TMP healing process were identified - the acute healing phase (3-17 days), the transition phase (3-4 weeks) and the chronic phase (6-10 weeks).

CONCLUSION

Based on the histological results of this study, the progressive development of chronic TMPs appeared to be associated with increased epidermal thickening, collagen and keratin deposition, macrophage infiltration and reduced cellular proliferation. After the 3-4 weeks of transition phase, the TMPs seemed to have transformed into a non-healing chronic TMP between 6 and 10 weeks.

Enhanced expression of hepatocyte growth factor in the healing of experimental acute tympanic membrane perforation

OBJECTIVES

The present study was performed to investigate the expression of hepatocyte (HGF), epidermal (EGF) and vascular endothelial (VEGF) growth factors in the course of healing of experimental tympanic membrane (TM) perforations in rats. The goal was to explain the role of these growth factors in the healing process of TM and to assess the possibility of their future application as healing promoters.

METHODS

Seventy rats were used, of which 10 served as controls and the others had their TM perforated. The experimental animals were divided into six subgroups on the basis of time points (01, 03, 05, 07, 09, 15 day after injury). Videootoscopy and histology were employed to assess the morphology of the healing process. The expressions of HGF, EGF and VEGF were evaluated using Western blot analysis. Tissue localization of HGF was determined by the immunofluorescence method.

RESULTS

HGF was hardly detectable in normal TM; however, a significant increase was noted in its expression starting from the third day after injury throughout the follow-up period, with the highest level on day 05. The analysis of HGF tissue localization with immunofluorescence revealed diffuse staining in the cytoplasm of proliferating epithelial cells. The expression of EGF was elevated on the first day after injury, not reaching statistical significance, and then returned to the level observed in the control TM. No significant differences were noted in the expression of VEGF.

CONCLUSION

High expression of HGF during the healing process of acute TM perforations makes it a promising candidate for further studies oriented towards its possible use in augmentation of TM healing.

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.

Analysis of gene expression profiles in tympanic membrane following perforation using PCR Array in rats--preliminary investigation

OBJECTIVES

The goal of this work was to identify genes, known to be involved in the skin wound healing, that express differentially in the healthy and injured tympanic membrane (TM), and designate the molecules potentially beneficial for treatment of TM perforation. The molecular mechanisms controlling the course of TM regeneration are far from being elucidated.

METHODS

Twenty rats had their tympanic membranes perforated, while four served as a control. Animals were sacrificed on either days 1, 2, 3, 5 and 10 post injury, and TMs were immediately dissected and frozen in liquid nitrogen. Total TM RNA was isolated and reversely transcribed. qPCR was performed using Rat Wound Healing RT(2) Profiler PCR Array (QIAGEN) containing primers for 84 genes.

RESULTS

Statistically significant changes in the expression of 42 genes were found in various stages of TM healing. The increased expression of genes taking part in the inflammatory reaction (interleukin 6, granulocyte and macrophage chemotactic proteins) was observed from day 2. The expression of several genes of extracellular matrix components and their remodeling enzymes was also changed. Among growth factor genes: Vegfa, Igf1 and Hbegf showed increased expression at the beginning of the healing process, while Hgf expression was highest on day 3.

CONCLUSIONS

Several changes in the expression of genes involved in remodeling of extracellular matrix point to important role of connective tissue in TM healing. The molecules accelerating this process, like HbEGF and HGF, seem to be good candidates for further evaluation of their possible use in clinical treatment.

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.

Healing of laser-induced tympanic membrane perforations in rats: no contribution of granulocyte colony-stimulating factor or Gelfoam

OBJECTIVES

To study whether granulocyte colony-stimulating factor together with Gelfoam (absorbable gelatin sponge, USP) could enhance the healing of freshly perforated tympanic membranes. The frequency and occurrence of different immunocompetent cells and collagen types was noted.

METHODS

Laser perforations were made in the tympanic membrane of rats that were sacrificed at different time intervals post-myringotomy: Day 1, 3, 6, and 12. Tympanic membrane specimens were embedded and sections were stained with hematoxylin/eosin and an immunohistochemical technique was used, with antibodies against macrophages, B-cells, T-cells, and type I-IV collagens. Semi-quantification was performed after counting positive cells, mean values were calculated and analyzed statistically.

RESULTS

All perforations, except one, had closed by Day 12 and no difference was observed between experimental and control ears at the other time points. Gelfoam was still present in a high amount at Day 12. The sections were initially stained positive for type I and II collagen, but after Day 6, the regenerating tissue stained positive for mainly type III and IV collagens. Results showed that the recruitment of macrophages, B-cells, and T-cells could not be mapped with a statistical significance.

CONCLUSIONS

This study showed that at 6-12 days post-laser myringotomy, type III and IV collagen has replaced the collagen type II that normally constitutes the healthy tympanic membrane. There is a concern for excessive scarring involving adjacent structures. It was also seen that the combination of Gelfoam and granulocyte colony-stimulating factor or saline did not affect the healing times in perforated tympanic membranes. No significant results regarding the inflammatory cell recruitment could be obtained on the studied time points or between experimental and control ears, except for in the Gelfoam matrix.

The role of vascular endothelial growth factors and fibroblast growth factors in angiogenesis during otitis media

The middle ear response to otitis media includes transformation and hyperplasia of the mucosal epithelium and subepithelial connective tissue. Significant neovascularization is also noted, which occurs both to support the hypertrophied mucosa and to mediate the increased trafficking of leukocytes. We investigated the role of two known potent angiogenic growth factor families, the fibroblast growth factors (FGFs) and vascular endothelial growth factors (VEGFs), in middle ear mucosal angiogenesis. DNA microarrays were used to evaluate the expression of FGFs and VEGFs, as well as their receptors and unique signaling proteins, in the middle ears of mice undergoing a complete course of acute bacterial otitis media. In addition, a member of each family was introduced to the middle ear submucosal compartment of the normal middle ears of guinea pigs, by a continuous-release osmotic minipump system over 1 week. During the course of bacterial otitis media, a significant regulation of a number of genes important for angiogenesis was identified. Histologic evaluation of middle ear mucosa following micropump infusion of both FGF1 and VEGF-A showed significant angiogenesis at the site of infusion in comparison to control saline infusion. These results support a role for FGFs and VEGFs in the neovascularization of the middle ear mucosa during otitis media, and offer a potential avenue for therapeutic intervention.

Tympanic membrane wound healing in rats assessed by transcriptome profiling

OBJECTIVES/HYPOTHESIS

The aim of this study is to elucidate transcriptional changes that occur in response to tympanic membrane (TM) perforation in rats and to infer key genes and molecular events in the healing process.

STUDY DESIGN

A prospective cohort study of 393 male Sprague-Dawley (Rattus norvegicus) rats.

METHODS

Sprague-Dawley rats were randomly allocated into either control or perforation groups spanning a 7-day time period. Perforation groups consisted of 12-hour, 24-hour, 36-hour, 2-day, 3-day, 4-day, 5-day, six-day, and 7-day time points. The left TMs of all perforation groups were perforated and the RNA extracted at the specified time point postperforation. Subsequent analysis was performed using Agilent's 4 × 44 k whole rat genome arrays (40 in total) to assess wound-healing gene expression over a 7-day time period.

RESULTS

Over a 7-day time course and at nine time points that encompassed the wounding and progression of healing, a total of 3,262 genes were differentially expressed. In this study the transcripts most upregulated occurred at 12 hours. These were Stefin A2 (344-fold), Stefin 2 (143-fold), and Natriuretic peptide precursor type B (222-fold). Those most downregulated also occurred at 12 hours. These were alcohol dehydrogenase 7 (13.1-fold) and gamma-butyrobetaine hydroxylase (10.4-fold). Results were validated by quantitative real-time polymerase chain reaction.

CONCLUSIONS

The findings of this study provide a baseline against which to identify disease-related molecular signatures, biomarkers, and to develop new treatments for TM conditions based on molecular evidence.

Keratinocyte growth factor 1, fibroblast growth factor 2 and 10 in the healing tympanic membrane following perforation in rats

The aim of this study was to provide a transcriptome profile of Keratinocyte Growth Factor (KGF)-1, Fibroblast Growth Factor (FGF) 2 and FGF10 (KGF2) in the healing rat tympanic membrane (TM) over 7 days and an immunohistochemical account over 14 days following perforation. KGF1, FGF2, and FGF10 play important roles in TM wound healing. The tympanic membranes of rats were perforated and sacrificed at time points over a 14-day period following perforation. The normalized signal intensities and immunohistochemical protein expression patterns at each time point for KGF1, FGF2, and FGF10 are presented. The primary role of both KGF1 and FGF2 appeared to be in the proliferation and migration of keratinocytes. Whereas the role of KGF1 appeared to be exclusively concerned with increased proliferation and migration at the perforation site, the continued expression of FGF2, beyond perforation closure, suggested it has an additional role to play. FGF10 (KGF2), whilst possessing the highest sequence homologous to KGF1, has a different role in TM wound healing. The effect of FGF10 on keratinocytes in wound healing appeared to emanate from the connective tissue layer.

The role of epidermal growth factor in the healing tympanic membrane following perforation in rats

Epidermal Growth Factor (EGF) has been identified as playing a critical role in the wound healing process. The objective of this study is to investigate the role that EGF plays in rat tympanic membrane (TM) wound healing using two techniques, microarray and immunohistochemistry. The tympanic membranes of rats were perforated using a sterile needle and sacrificed at time points during 2 weeks following perforation. The normalized signal intensities at the time points for EGF and associated genes are presented. The rat EGF mRNA did not change significantly between time points. Five associated proteins, including heparin-binding EGF-like growth factor were found to be differentially expressed above a two fold threshold at 12 h following perforation. EGF staining was found at low levels in the uninjured TM. Levels of EGF staining increased at 24 h in the basal keratinocyte layer, became diffusely elevated in the specimen at 36 h, before a second peak in staining of the keratinocyte layer at Day 4. The staining of EGF corresponds to its multiple roles in TM wound healing.

The importance of vascular endothelial growth factor in the healing of acute tympanic membrane perforation

PURPOSE

The purpose of this study was to determine the more important growth factor expression between basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) in the healing of acute tympanic membrane (TM) perforation.

MATERIALS AND METHODS

Bilateral perforations of the TM were created in 12 rats. The TM perforations in the right ears were treated with dexamethasone, and left ears were designated as the control group. The TM was examined for the growth factor expression immunohistochemically in the epithelial and fibrous layers according to the rate of TM perforation healing.

RESULTS

The mean spontaneous healing time of the TM perforations was 11.0 +/- 2.0 days. However, dexamethasone-treated group showed no evidence of closure. The bFGF and VEGF expression were significantly correlated with the rate of healing of acute TM perforations. The VEGF expression was decreased both in the epithelial and fibrous layers, but bFGF expression was decreased only in the epithelial layer in the dexamethasone-treated group. The VEGF was expressed to a lesser degree than bFGF in the dexamethasone-treated group.

CONCLUSION

Vascular endothelial growth factor is the more specific and important growth factor than bFGF in the healing of acute TM perforation.

Platelet-rich plasma improves healing of tympanic membrane perforations: experimental study

Objective:

The aim of this study was to investigate the effect of local application of platelet-rich plasma to perforated rat tympanic membranes, in terms of healing time and histopathological outcome.

Methods:

Eighty-eight tympanic membranes of 44 rats were given a standard 3 mm perforation, and platelet-rich plasma was applied to the right tympanic membrane perforations. The left tympanic membranes were left to heal spontaneously, as controls. The 44 rats were divided into two groups. In group one, comprising 20 rats, daily otomicroscopic examination of the tympanic membrane perforations was performed. The 24 rats in group two were subdivided into four subgroups of six rats each; these subgroups were sacrificed sequentially on days three, seven, 14 and 28 for histopathological examination, regardless of tympanic membrane healing stage.

Results:

In group one, the mean tympanic membrane healing times for tympanic membrane perforations receiving platelet-rich plasma and controls were respectively 10.2 ± 2.1 and 13.0 ± 2.9 days (mean ± standard deviation). This difference was statistically significant (p < 0.001). In group two, histopathological evaluation of tympanic membrane perforation healing at days three, seven, 14 and 28 did not reveal any statistically significant difference, individually or within the four groups as a whole.

Conclusion:

These findings suggest that earlier healing of tympanic membrane perforations occurred in the platelet-rich plasma group compared with the control group. These findings suggest that platelet-rich plasma is effective in accelerating tympanic membrane perforation healing, and that it may be effective in human subjects, particularly as it is an autologous material.

[Tympanic membrane perforation and tympanoplasty]

OBJECTIVES

To report anatomic and physiologic characteristics of the tympanic membrane, to discuss the etiology and pathogenesis of tympanic perforation, and to discuss its management.

MATERIAL AND METHODS

After a review of the literature, different surgical techniques and the postoperative results were evaluated.

RESULTS

The rate of tympanic membrane closure is greater than 90% for the majority of authors. Age, mucosa inflammation, pathological contralateral ear (perforation, otitis media, cholesteatoma), and surgical experience influence this result.

DISCUSSION

Even if surgical results are good, abstention must always be proposed and all complications must be explained.

CONCLUSION

Palisade cartilage tympanoplasty is an effective technique for both tympanic membrane closures.

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

An animal model of chronic tympanic membrane (TM) perforation is needed for experiments on supporting wound healing of TM perforations. The epidermal growth factor receptor (EGFR) has been implicated in the regulation of wound healing. The object of this study was to investigate the efficacy of topical EGFR-inhibitor (erlotinib) to arrest wound healing of experimental TM perforation in rats. Bilateral instrumental myringotomies were performed in 13 male rats. A solution of erlotinib (10 mg/mL) was applied to one TM of each animal and vehicle only (control group) to the other side. The application procedure was repeated on both sides daily for 12 consecutive days. Thereafter, tympanic membranes were observed weekly for a total of 30 days. The mean healing period was found to be 12.1 days in the group with erlotinib and 6.4 days in the control group. The difference was significant. We observed differences in the histologic parameters between erlotinib group and control group. The inhibition of EGFR by topical application of erlotinib did delay the healing rate of myringotomies but seems not to be suitable to create a chronic TM perforation in rat.

Healing of subacute tympanic membrane perforations in chinchillas treated with epidermal growth factor and pentoxifylline

HYPOTHESIS

The aims of the present study were to determine the effect of epidermal growth factor (EGF) and pentoxifylline on subacute tympanic membrane (TM) perforations and to quantify the healing rate of such perforations treated with these drugs alone or in combination.

BACKGROUND

It is known that EGF modulates in vitro and in vivo proliferation of epithelial and endothelial cells. Pentoxifylline is a methylxanthine that has been used to treat experimental skin flaps and venous leg ulcers. Data in the literature regarding this subject are contradictory, and quantitative data regarding the effects of EGF and pentoxifylline on TM perforation healing are scarce.

METHODS

We studied 50 chinchillas submitted to TM perforation. On postoperative Day 30, eight were selected for histologic analysis. Of the remaining 42, those presenting little or no healing were distributed into four groups: control, EGF, pentoxifylline, and EGF combined with pentoxifylline.

RESULTS

Histologic analysis showed that the observation period adopted was sufficient to consider the TM perforations subacute. We found significant differences between the study groups and the control group in the healing rate of subacute TM perforations during a 30-day period (analysis of variance; p < 0.001), which was 30.3% for the EGF group, 3.6% for the pentoxifylline group, 16.5% for the EGF-pentoxifylline group, and 8.7% for the control group.

CONCLUSIONS

The use of EGF promoted healing of subacute TM perforations in chinchillas, and the use of pentoxifylline did not. The combination of the two had no synergistic effect on the healing of these perforations.

Effectiveness of MeroGel hyaluronic acid on tympanic membrane perforations

CONCLUSIONS

Our results support the proposition that hyaluronic acid (HA) provides a moist wound-healing environment to aid in the healing process of tympanic membrane perforation. A single MeroGel administration can be effective as well as daily topical HA application in the treatment of tympanic membrane perforations. A single application of esterified HA may be more suitable for patients and also for otolaryngologists.

OBJECTIVE

The purpose of the present study was to evaluate the effectiveness of a single MeroGel application on traumatic tympanic membrane perforations in rats.

MATERIALS AND METHODS

The posterior quadrant of the tympanic membranes in both ears of 24 male pathogen-free Sprague-Dawley rats was perforated with a 20-gauge needle. Subjects were divided into two groups: MeroGel and daily topical HA-treated groups. All subjects were sacrificed and histopathological examinations of the tympanic bullas were carried out.

RESULTS

Perforations of controls, and MeroGel- and daily HA-treated groups closed in 17/24 (70.8%), 11/12 (91.7%), and 12/12 (100%) ears, respectively. There was a significant difference between control and MeroGel-treated groups, and also between control and daily topical HA-treated groups for the presence of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), lymphocytes and collagen fibrils (p<0.05), whereas there was no significant difference between MeroGel- and daily topical HA-treated groups (p>0.05).

Spontaneous healing of various tympanic membrane perforations in the rat

OBJECTIVES

To investigate the spontaneous healing process of various types of perforation and the location of the epithelial generation center in the tympanic membrane of rats.

MATERIAL AND METHODS

Various types of perforation were made in the ears of 50 rats and the healing process was observed using light and electron microscopy.

RESULTS

Epithelia hyperplasia could not be seen at the edge of the perforations, but occurred in the annulus and handle of malleus regions during the early stage of healing. There was no correlation between the healing time and the size of the perforations. When one ear was perforated, no changes were observed in the intact ear on the other side. The epithelium did not migrate into the tympanic cavity in the posterior marginal perforations. All the perforations healed, although the manubria of the malleus were damaged.

CONCLUSIONS

The perforations healed by means of epithelial migration. The epithelial generation center was located near the annulus and the handle of the malleus, and therefore protection of these two regions is very important in middle ear surgery.

Miringoplastia com a utilização de um novo material biossintético

A miringoplastia é uma cirurgia com a finalidade de controlar a infecção no ouvido médio, reconstruir o mecanismo de transmissão sonora para a janela oval e proteger a janela redonda. São descritos diversos materiais para reconstruir a membrana timpânica, destacando-se a fáscia do músculo temporal, pericôndrio do tragus, cartilagem, dura-máter, tecido placentário, entre outros. OBJETIVO: Este trabalho tem objetivo de demonstrar o efeito de um novo biomaterial, a membrana de látex natural com polilisina, desenvolvida no laboratório de Neuroquímica do Departamento de Bioquímica da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo - USP. FORMA DE ESTUDO: Coorte Longitudinal. MATERIAL E MÉTODO: O biomaterial utilizado é estimulante da neovascularização e crescimento tecidual organizado em diferentes órgãos e tecidos, sendo um material inócuo e não rejeitado pelo organismo. Foi usada a biomembrana de látex com polilisina como um implante transitório para o fechamento da perfuração da membrana timpânica. A membrana foi colocada na face externa dos bordos da membrana timpânica e a fáscia temporal na face interna da mesma. Foram estudadas 238 orelhas com perfuração de membrana timpânica por seqüela de otite média crônica, submetidas a miringoplastia com enxerto de fáscia de músculo temporal e a membrana de látex natural, com idades de 7 a 76 anos. Apresentavam uma ou mais miringoplastias anteriores sem sucesso 41 dos casos. RESULTADO: Como ressaltamos preliminarmente, verificamos pega do enxerto em 90,5% das orelhas (181), sendo fechamento de perfuração amplas, 96; médias, 73 e 12 pequenas. Verificamos intensa vascularização em 100% dos enxertos, o que não é habitual quando não se usa a membrana de látex natural. CONCLUSÃO: Conclue-se que o biomaterial usado merece nossa atenção quanto ao seu uso como implante transitório em miringoplastias, melhorando o processo de revascularização da membrana timpânica remanescente.

The Role of Growth Factors for Disease and Therapy in Diseases of the Head and Neck

Growth factors are a large family of polypeptide molecules that regulate cell division in many tissues by autocrine or paracrine mechanisms. Depending on what receptors are activated, growth factors can initiate mitogenic, antiproliferative, or trophic effects, that is, growth factors act as positive or negative modulators of cell proliferation. Therefore, growth factors do not only play an important role in embryonic development and adult tissue homeostasis, but also in pathological situations like infection, wound healing, and tumorigenesis. Consequently, the application of growth factors, or vice versa the application of substances which are directed against growth factors like antigrowth factor antibodies, may have therapeutic applications. This review provides a brief account of what we know regarding growth factors in otorhinolaryngology, particularly in the field of otology, wound healing, oncology, peripheral nerve regeneration, and rhinology.

The effects of hyaluronic acid, epidermal growth factor, and mitomycin in an experimental model of acute traumatic tympanic membrane perforation

HYPOTHESIS

The goal of this study was to evaluate the effects of hyaluronic acid, epidermal growth factor, and mitomycin C on the healing of acute experimental traumatic perforations of the tympanic membrane.

BACKGROUND

Most acute perforations of the tympanic membrane heal spontaneously. However, some form of surgical treatment (i.e., myringoplasty) is needed for nonhealing perforations. Because the closure occurs by squamous epithelial migration, drugs that stimulate this regenerative process may aid in the closure of the perforation, obviating the need for more extensive treatments.

METHODS

Bilateral perforations of the tympanic membrane were created in 30 rats, divided into three groups (A, B, C). The perforations in the right ears were treated with hyaluronic acid, epidermal growth factor, or mitomycin C. Those in the left ears were left untreated for comparison. To examine the healing process in different periods, 5 animals were killed in each group at days 3, 5, 7, 9 and 14. The other 5 animals in each group were observed daily to determine the duration of perforation closures. Thirty surgical specimens (5 right sides from each group and all 15 left sides in all groups) were histopathologically examined for tympanic membrane thickness, fibroblastic reaction, neovascularization, and crust morphology.

RESULTS

Hyaluronic acid and epidermal growth factor applications significantly shortened the healing in acute experimental traumatic perforations of the tympanic membrane (p = 0.0432); however, the difference between them was not significant (p = 0.3160). On the other side, tympanic membrane perforations treated with topical mitomycin C showed no evidence of closure. There were no significant differences in the histologic parameters between the treated groups and their contralateral control ears.

CONCLUSION

Hyaluronic acid and epidermal growth factor accelerated the closure of acute tympanic membrane perforations in rats. This may make them clinically useful in augmenting the efficiency of conservative treatments of acute perforations of the tympanic membrane.

Induction of growth factor expression is reduced during healing of tympanic membrane perforations in glucocorticoid-treated rats

The participation of growth factors in wound healing of tympanic membranes (TMs) is established. To determine the possible role of these growth factors in normal healing, we examined the regulation of keratinocyte growth factor (KGF), transforming growth factor-alpha (TGF-alpha), and basic fibroblast growth factor (bFGF) messenger RNA (mRNA) expression in wounded TMs of glucocorticoid-treated rats; these rats have severe wound healing abnormalities. Induction of KGF, TGF-alpha, and bFGF mRNA expression after TM injury was significantly reduced in these rats. Moreover, we found that the average number of bromodeoxyuridine-positive cells in a glucocorticoid-treated group was significantly lower than that in controls. The data suggest that reduced expression of these genes might be partially responsible for the wound healing defects seen in these animals. These results provide a possible explanation for the beneficial effect of exogenous KGF, TGF-alpha, or bFGF in treatment of wound healing disorders of the TM.

Topical treatment with growth factors for tympanic membrane perforations: progress towards clinical application

Basic scientific research has demonstrated that epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), platelet-derived growth factor-AA (PDGF-AA) and transforming growth factor-alpha (TGF-alpha) are induced by acute tympanic membrane (TM) perforation. The expression of these growth factors peaks during the inflammatory phase and then declines, suggesting their involvement in the healing process of the TM. Expression of EGF receptor, bFGF receptor, PDGF receptor and keratinocyte growth factor (KGF) receptor in the TM has also been reported. Identification of these receptors indicates that the target cells in the TM may be stimulated during the process of healing by the corresponding exogenous growth factor in vivo. Some reports from animal studies showed encouraging effects of EGF, bFGF and PDGF-AA in terms of accelerated or enhanced healing of acute and chronic TM perforations without significant adverse effects. Two reports of clinical trials of topical application of EGF or bFGF for TM perforations revealed mixed results. In this article special considerations for future directions of research into growth factors are discussed and related articles on healing of skin wounds and other lesions are reviewed. Further experimental and clinical studies on the mechanism of action of growth factors, timing of application, selection (either singly or in combination), delivery mode, dose and safety aspects, as well as more clinical trials, are warranted, and will pave the way for clinical application.

Creating a stable tympanic membrane perforation using mitomycin C

OBJECTIVE

To determine the ability of topically applied mitomycin C to create a stable tympanic membrane perforation.

STUDY DESIGN AND SETTING

Twenty-four rats underwent subtotal removal of the tympanic membranes bilaterally. Forty ears received 0.2 mg/ml of mitomycin C. The remaining 8 received phosphate-buffered saline solution (control). Photographs taken every 3 to 5 days for 44 days were digitally scanned and computer analyzed to calculate the percentage of residual perforation. Application of solutions, photography, and data analysis were performed in a blinded fashion.

RESULTS

The mitomycin C treated ears had delayed closure time and healing rate (from day 0 to 25) compared to the control group. All controls healed by day 14. By day 44, 92.5% of the mitomycin C treated ears healed.

CONCLUSION

Mitomycin C prolongs the closure and healing rate of myringotomies in rat tympanic membranes.

SIGNIFICANCE

Myringotomy with concurrent mitomycin C application may be useful for creating an animal model for chronic tympanic membrane perforation and should be tested in human beings as a method to maintain myringotomy patency for long-term ventilation.

Induction of KGF, basic FGF, and TGFalpha mRNA expression during healing of experimental TM perforations

KGF (KGF), synthesized and secreted exclusively by stromal cells in epithelialized organs, specifically promotes proliferation of cells of epithelial origin, including keratinocytes. A related peptide, basic fibroblast growth factor (bFGF), has mitogenic properties for fibroblasts and endothelial cells. KGF expression is stimulated markedly in the skin during wound healing. To investigate the physiologic action of KGF in the healing of TM (TM) perforations, we examined KGF and KGF receptor (KGFR) mRNA transcript levels as well as those of bFGF and transforming growth factor-alpha (TGFalpha) in normal and wounded rat TM at varying intervals, using a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). We found KGF and TGFalpha mRNA expression to be induced rapidly, peaking 3 days after wounding and then declining. Expression of bFGF was induced gradually and remained increased until 7 days. In contrast, we found KGFR to be expressed in normal TM, remaining unchanged during TM repair. These results indicate that KGF and TGFalpha may mediate migration and proliferation of epithelial cells of the outer layer in the early stage of TM repair while bFGF may mediate the connective tissue reaction in the middle layer in a subsequent stage.

The effect of acidic fibroblast growth factor and live yeast cell derivative on tympanic membrane regeneration in a rat model

The current treatment of choice for chronic tympanic membrane perforations is surgery. Recent studies using various polypeptide growth factors to accelerate closure of tympanic membrane perforations in model systems have produced mixed results. This study evaluates the effect of acidic fibroblast growth factor (AFGF) and live yeast cell derivative (LYCD) on the rate of healing of acute tympanic membrane perforations in a rat model. Thirty-seven rats had both ears separately randomized in a blinded fashion to receive AFGF in one of three concentrations, LYCD, or a control solution. The rats initially underwent subtotal removal of the tympanic membranes bilaterally. Solutions were applied to the randomized ears daily for 3 days, starting at the time of the surgical perforation. The ears were photographed every 3 to 8 days for 35 days. The photographs were digitally scanned and a computer analysis was used to calculate the percentage of residual perforation. No significant difference in the rate of healing was observed for ears treated with AFGF or LYCD versus the controls. Given the potential advantages of medical treatment of tympanic membrane perforations and the established efficacy of growth factors in other model systems, however, further research is warranted.

Overlay versus underlay tympanoplasty. Part I: historical review of the literature

The history of otology is the history of the successful treatment of infections of the middle ear and the eardrum. Otologists have sought to restore hearing lost to infections of the eardrum since the 1600s. The development of instruments, techniques, and materials to treat infection is fascinating because of the serendipitous nature of the discoveries and the insight of the discoverers. This historical review describes the history of the treatment of infections of the ear and the development of modern techniques of ear surgery. Two contemporary methods of tympanic membrane repair are then described.

Effects of fibroblast growth factor on the healing process of tympanic membrane perforations in an animal model

After traumatic perforation of the tympanic membrane (TM), healing occurs spontaneously in most cases, although occasional perforations will fail to close. Healing of epithelia at any site involves cell movement, with injury providing the stimulus to initiate changes in the behavior of cells that are normally static. Epidermal proliferation at the margins of the TM perforation can be accelerated by using such growth factors as epidermal growth factor, basic fibroblast growth factor (bFGF) and hyaluronan. bFGF is chemotactic and mitogenic for both fibroblasts and endothelial cells and is also mitogenic for keratinocytes. The effect of bFGF is significant in the enhancement of fibroblast production and angiogenesis. In this study, bFGF was used to enhance the healing process of chronic TM perforations in a guinea pig animal model. Chronic perforations were created since acute TMs could heal spontaneously without using any bioactive substance. In all, 30 TMs of 15 guinea pigs were used. A thermal myringotomy loop was employed to create a subtotal TM perforation at the area of the pars tensa. After establishing a permanent, non-infected perforation, bFGF in buffered saline solution was applied as 400 ng/day to 15 ears, while the opposite (control) ear was treated with only saline solution. At 20 days, 13 of 15 perforations treated with bFGF had closed. Light microscopy was used to assess organization of the healed TMs. The effects of bFGF on the healing process of TM perforations were compared in treated and non-treated ears.