Dose- and starting time-dependent effect of the application of EGF to the regeneration of traumatic eardrum

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.

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.

The effectiveness and safety of growth factors in the treatment of tympanic membrane perforations: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

To determine the clinical efficacy and safety of growth factors in the treatment of tympanic membrane (TM) perforations from randomized controlled trials (RCTs).

METHODS

Databases, including PubMed, EMBASE, Cochrane library, Ebsco, Ovid, Scopus, and Web of Science, were searched for articles in any language about studies on the treatment of TM perforations with growth factors. Inclusion criteria were: (1) randomized controlled trials (RCTs); (2) only patients with TM perforations included; and (3) any kinds of growth factors or related products were used as an intervention. Exclusion criteria were: (1) study was not reported as a full paper, only as an abstract; (2) review studies and case reports; and (3) an inability to extract valid data. Outcomes of interest included perforation closure rate, closure time, hearing improvement, and complications.

RESULTS

Nineteen RCTs with a total of 1335 participants were included. Growth factors effectively increased the rate of perforation closure [risk ratio (RR): 1.21 95% confidence interval (1.12, 1.30), p < 0.01] and shortened closure time [mean difference (MD): - 16.71 (- 22.74, - 10.15), p < 0.01]. There was no significant difference in hearing improvement [MD: 0.10 (- 0.50, 0.70), p = 0.74] or complications [RR: 1.49 (0.96, 2.32), p = 0.07] between the growth factor intervention group and the control group.

CONCLUSION

Growth factors are effective and safe in the treatment of TM perforations. However, better designed clinical trials should be carried out in the future to obtain more robust findings about the effectiveness of growth factors in the treatment of TM perforations.