Tissue engineering applications in otolaryngology-The state of translation

Tissue engineering in otology: a review of achievements

Tissue engineering application in otology spans a distance from the pinna to auditory nerve covered with specialized tissues and functions such as sense of hearing and aesthetics. It holds the potential to address the barriers of lack of donor tissue, poor tissue match, and transplant rejection through provision of new and healthy tissues similar to the host and possesses the capacity to renew, to regenerate, and to repair in-vivo and was shown to be a bypasses for any need to immunosuppression. This review aims to investigate the application of tissue engineering in otology and to evaluate the achievements and challenges in external, middle and inner ear sections. Since gaining the recent knowledge and training on use of different scaffolds is essential for otology specialists and who look for the recovery of ear function and aesthetics of patients, it is shown in this review how utilizing tissue engineering and cell transplantation, regenerative medicine can provide advancements in hearing and ear aesthetics to fit different patients' needs.

Tissue engineering in otorhinolaryngology: A knowledge-based analysis

Objective

To analyze the impact, performance, degree of specialization, and collaboration patterns of the worldwide scientific production on tissue engineering in otorhinolaryngology at the level of countries and institutions.

Methods

Two different techniques were used, performance and science mapping analyses, using as samples all the available documents regarding tissue engineering focused on otorhinolaryngology applications. The dataset was retrieved from the Core Collection of the Web of Science database from 1900 to 2020. Social structure was analyzed using science mapping analysis with VOSviewer software.

Results

The United States was the main producer, followed by Germany, and Japan. Malaysia and Germany had the highest Relative Specialization Index, indicating their greater relative interest in this area compared to other countries. The social structure analysis showed that the United States and Germany had significant co-authorship relationships with other countries. The University of California System, Kyoto University, and Harvard University were the leading institutions producing literature in this field. These latter two institutions showed the largest number of collaborations, although most of them were with institutions within their own country. There was a lack of connections between different communities of research.

Conclusion

The United States is the main country driving progress in this research area, housing the most notable institutions. However, significant collaborations between these research centers are currently lacking. Encouraging greater cooperation among these institutions and their researchers would promote the exchange of knowledge, ultimately facilitating and accelerating advancements in this field.

Validation of airway porcine epithelial cells as an alternative to human in vitro preclinical studies

Animal models are currently used in several fields of biomedical research as useful alternatives to human-based studies. However, the obtained results do not always effectively translate into clinical applications, due to interspecies anatomical and physiological differences. Detailed comparability studies are therefore required to verify whether the selected animal species could be a representative model for the disease or for cellular process under investigation. This has proven to be fundamental to obtaining reliable data from preclinical studies. Among the different species, swine is deemed an excellent animal model in many fields of biological research, and has been largely used in respiratory medicine, considering the high homology between human and swine airways. In the context of in vitro studies, the validation of porcine airway epithelial cells as an alternative to human epithelial cells is crucial. In this paper, porcine and human tracheal and bronchial epithelial cells are compared in terms of in vivo tissue architecture and in vitro cell behaviour under standard and airlifted conditions, analyzing the regenerative, proliferative and differentiative potentials of these cells. We report multiple analogies between the two species, validating the employment of porcine airway epithelial cells for most in vitro preclinical studies, although with some limitations due to species-related divergences.

Analysis of cognitive framework and biomedical translation of tissue engineering in otolaryngology

Tissue engineering is a relatively recent research area aimed at developing artificial tissues that can restore, maintain, or even improve the anatomical and/or functional integrity of injured tissues. Otolaryngology, as a leading surgical specialty in head and neck surgery, is a candidate for the use of these advanced therapies and medicinal products developed. Nevertheless, a knowledge-based analysis of both areas together is still needed. The dataset was retrieved from the Web of Science database from 1900 to 2020. SciMAT software was used to perform the science mapping analysis and the data for the biomedical translation identification was obtained from the iCite platform. Regarding the analysis of the cognitive structure, we find consolidated research lines, such as the generation of cartilage for use as a graft in reconstructive surgery, reconstruction of microtia, or the closure of perforations of the tympanic membrane. This last research area occupies the most relevant clinical translation with the rest of the areas presenting a lower translational level. In conclusion, Tissue engineering is still in an early translational stage in otolaryngology, otology being the field where most advances have been achieved. Therefore, although otolaryngologists should play an active role in translational research in tissue engineering, greater multidisciplinary efforts are required to promote and encourage the translation of potential clinical applications of tissue engineering for routine clinical use.

3D Bioprinting in Otolaryngology: A Review

The evolution of tissue engineering and 3D bioprinting has allowed for increased opportunities to generate musculoskeletal tissue grafts that can enhance functional and aesthetic outcomes in otolaryngology-head and neck surgery. Despite literature reporting successes in the fabrication of cartilage and bone scaffolds for applications in the head and neck, the full potential of this technology has yet to be realized. Otolaryngology as a field has always been at the forefront of new advancements and technology and is well poised to spearhead clinical application of these engineered tissues. In this review, current 3D bioprinting methods are described and an overview of potential cell types, bioinks, and bioactive factors available for musculoskeletal engineering using this technology is presented. The otologic, nasal, tracheal, and craniofacial bone applications of 3D bioprinting with a focus on engineered graft implantation in animal models to highlight the status of functional outcomes in vivo; a necessary step to future clinical translation are reviewed. Continued multidisciplinary efforts between material chemistry, biological sciences, and otolaryngologists will play a key role in the translation of engineered, 3D bioprinted constructs for head and neck surgery.

Ex Vivo Maturation of 3D-Printed, Chondrocyte-Laden, Polycaprolactone-Based Scaffolds Prior to Transplantation Improves Engineered Cartilage Substitute Properties and Integration

OBJECTIVE

The surgical management of nasal septal defects due to perforations, malformations, congenital cartilage absence, traumatic defects, or tumors would benefit from availability of optimally matured septal cartilage substitutes. Here, we aimed to improve in vitro maturation of 3-dimensional (3D)-printed, cell-laden polycaprolactone (PCL)-based scaffolds and test their in vivo performance in a rabbit auricular cartilage model.

DESIGN

Rabbit auricular chondrocytes were isolated, cultured, and seeded on 3D-printed PCL scaffolds. The scaffolds were cultured for 21 days in vitro under standard culture media and normoxia or in prochondrogenic and hypoxia conditions, respectively. Cell-laden scaffolds (as well as acellular controls) were implanted into perichondrium pockets of New Zealand white rabbit ears (N = 5 per group) and followed up for 12 weeks. At study end point, the tissue-engineered scaffolds were extracted and tested by histological, immunohistochemical, mechanical, and biochemical assays.

RESULTS

Scaffolds previously matured in vitro under prochondrogenic hypoxic conditions showed superior mechanical properties as well as improved patterns of cartilage matrix deposition, chondrogenic gene expression (COL1A1, COL2A1, ACAN, SOX9, COL10A1), and proteoglycan production in vivo, compared with scaffolds cultured in standard conditions.

CONCLUSIONS

In vitro maturation of engineered cartilage scaffolds under prochondrogenic conditions that better mimic the in vivo environment may be beneficial to improve functional properties of the engineered grafts. The proposed maturation strategy may also be of use for other tissue-engineered constructs and may ultimately impact survival and integration of the grafts in the damaged tissue microenvironment.

The Growing Medical Need for Tracheal Replacement: Reconstructive Strategies Should Overcome Their Limits

Breathing, being predominantly an automatic action, is often taken for granted. However, respiratory diseases affect millions of people globally, emerging as one of the major causes of disability and death overall. Among the respiratory dysfunctions, tracheal alterations have always represented a primary challenge for clinicians, biologists, and engineers. Indeed, in the case of wide structural alterations involving more than 50% of the tracheal length in adults or 30% in children, the available medical treatments are ineffective or inapplicable. So far, a plethora of reconstructive approaches have been proposed and clinically applied to face this growing, unmet medical need. Unfortunately, none of them has become a well-established and routinely applied clinical procedure to date. This review summarizes the main clinical reconstructive attempts and classifies them as non-tissue engineering and tissue engineering strategies. The analysis of the achievements and the main difficulties that still hinder this field, together with the evaluation of the forefront preclinical experiences in tracheal repair/replacement, is functional to promote a safer and more effective clinical translation in the near future.

Biocompatible Materials in Otorhinolaryngology and Their Antibacterial Properties

For decades, biomaterials have been commonly used in medicine for the replacement of human body tissue, precise drug-delivery systems, or as parts of medical devices that are essential for some treatment methods. Due to rapid progress in the field of new materials, updates on the state of knowledge about biomaterials are frequently needed. This article describes the clinical application of different types of biomaterials in the field of otorhinolaryngology, i.e., head and neck surgery, focusing on their antimicrobial properties. The variety of their applications includes cochlear implants, middle ear prostheses, voice prostheses, materials for osteosynthesis, and nasal packing after nasal/paranasal sinuses surgery. Ceramics, such as as hydroxyapatite, zirconia, or metals and metal alloys, still have applications in the head and neck region. Tissue engineering scaffolds and drug-eluting materials, such as polymers and polymer-based composites, are becoming more common. The restoration of life tissue and the ability to prevent microbial colonization should be taken into consideration when designing the materials to be used for implant production. The authors of this paper have reviewed publications available in PubMed from the last five years about the recent progress in this topic but also establish the state of knowledge of the most common application of biomaterials over the last few decades.

Three-Dimensional Bioprinting Scaffolding for Nasal Cartilage Defects: A Systematic Review

BACKGROUND

In recent years, three-dimensional (3D)-printing of tissue-engineered cartilaginous scaffolds is intended to close the surgical gap and provide bio-printed tissue designed to fit the specific geometric and functional requirements of each cartilage defect, avoiding donor site morbidity and offering a personalizing therapy.

METHODS

To investigate the role of 3D-bioprinting scaffolding for nasal cartilage defects repair a systematic review of the electronic databases for 3D-Bioprinting articles pertaining to nasal cartilage bio-modelling was performed. The primary focus was to investigate cellular source, type of scaffold utilization, biochemical evaluation, histological analysis, in-vitro study, in-vivo study, animal model used, length of research, and placement of experimental construct and translational investigation.

RESULTS

From 1011 publications, 16 studies were kept for analysis. About cellular sources described, most studies used primary chondrocyte cultures. The cartilage used for cell isolation was mostly nasal septum. The most common biomaterial used for scaffold creation was polycaprolactone alone or in combination. About mechanical evaluation, we found a high heterogeneity, making it difficult to extract any solid conclusion. Regarding biological and histological characteristics of each scaffold, we found that the expression of collagen type I, collagen Type II and other ECM components were the most common patterns evaluated through immunohistochemistry on in-vitro and in-vivo studies. Only two studies made an orthotopic placement of the scaffolds. However, in none of the studies analyzed, the scaffold was placed in a subperichondrial pocket to rigorously simulate the cartilage environment. In contrast, scaffolds were implanted in a subcutaneous plane in almost all of the studies included.

CONCLUSION

The role of 3D-bioprinting scaffolding for nasal cartilage defects repair is growing field. Despite the amount of information collected in the last years and the first surgical applications described recently in humans. Further investigations are needed due to the heterogeneity on mechanical evaluation parameters, the high level of heterotopic scaffold implantation and the need for quantitative histological data.

Advanced Strategies for Tissue Engineering in Regenerative Medicine: A Biofabrication and Biopolymer Perspective

Tissue engineering is known to encompass multiple aspects of science, medicine and engineering. The development of systems which are able to promote the growth of new cells and tissue components are vital in the treatment of severe tissue injury and damage. This can be done through a variety of different biofabrication strategies including the use of hydrogels, 3D bioprinted scaffolds and nanotechnology. The incorporation of stem cells into these systems and the advantage of this is also discussed. Biopolymers, those which have a natural original, have been particularly advantageous in tissue engineering systems as they are often found within the extracellular matrix of the human body. The utilization of biopolymers has become increasing popular as they are biocompatible, biodegradable and do not illicit an immune response when placed into the body. Tissue engineering systems for use with the eye are also discussed. This is of particular interest as the eye is known as an immune privileged site resulting in an extremely limited ability for natural cell regeneration.

Poly(vinyl alcohol)/Gelatin Scaffolds Allow Regeneration of Nasal Tissues

Need for regeneration and repair of nasal tissues occurs as a consequence of several pathologies affecting the nose, including, but not limited to infective diseases, traumas and tumor resections. A platform for nasal tissue regeneration was set up using poly(vinyl alcohol)/gelatin sponges with 20%–30% (w/w) gelatin content to be used as scaffolds, for their intrinsic hydrophilic, cell adhesive and shape recovery properties. We propose mesodermal progenitor cells (MPCs) isolated from the bone marrow as a unique stem cell source for obtaining different connective tissues of the nose, including vascular tissue. Finally, epithelial cell immune response to these scaffolds was assessed in vitro in an environment containing inflammatory molecules. The results showed that mesenchymal stromal cells (MSCs) deriving from MPCs could be used to differentiate into cartilage and fibrous tissue; whereas, in combination with endothelial cells still deriving from MPCs, into pre-vascularized bone. Finally, the scaffold did not significantly alter the epithelial cell response to inflammatory insults derived from interaction with bacterial molecules.

Regenerative Medicine of Epithelia: Lessons From the Past and Future Goals

This article explores examples of successful and unsuccessful regenerative medicine on human epithelia. To evaluate the applications of the first regenerated tissues, the analysis of the past successes and failures addresses some pending issues and lay the groundwork for developing new therapies. Research should still be encouraged to fill the gap between pathologies, clinical applications and what regenerative medicine can attain with current knowledge.