Topical application of transforming growth factor-β1 in acute traumatic tympanic membrane perforations: an experimental study in rats

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.

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.

Evaluation of the in vivo wound healing potential of the lipid fraction from activated platelet-rich plasma

Previous in vitro studies suggest a direct relevance for the peptide-free lipid fraction (LF) of platelet-rich plasma (PRP) in biological mechanisms related to wound healing. However, there are no scientific reports to date on the wound healing activities of this lipid component in vivo. Thus, the present study provides a scientific evaluation for the wound healing potential of the lipid portion of the activated PRP. For the wound healing activity assessment, in vivo full-thickness excisional wounds were created on the dorsal skin of Sprague-Dawley rats. Lipid extract from pooled PRP was applied topically to the wounds on 0, 3, and 7 days after injury. Histological assessment of epidermal and dermal regeneration, granulation tissue thickness and angiogenesis by Sirius red and Masson's trichrome staining, in addition to immunohistochemical staining for transforming growth factor beta-1 (TGF-β1), collagen type I (COL I), and collagen type III (COL III) were performed on skin biopsies at 3, 7 and 14 days. The total histological scores of the LF group were significantly higher than the 25% dimethylsulfoxide-control group. According to the immunohistochemical staining, the observed expression changes for TGF-β1, COL I and III at 3, 7, and 14 days after wounding were significantly better in the study group than the control group. Furthermore, COL I/III ratio in the lipid extract-treated group at day 14 was much higher than that of the control group. Meanwhile, analysis of the data also indicated that the LF has less positive effects on all evaluated parameters than PRP. From the present data, it could be concluded that the peptide-free LF of PRP has potent wound healing capacity in vivo for cutaneous wounds, although not as much as that of PRP. Strengthening our understanding of the wound healing potential of lipid components of PRP and platelet-derived lipid factors may provide new avenues for improving the healing process of a wound with elevated protease activity.

Outlook for Tissue Engineering of the Tympanic Membrane

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

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.

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.

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.