In Vitro Regeneration of Patient-specific Ear-shaped Cartilage and Its First Clinical Application for Auricular Reconstruction

Contribution of perichondrium to the mechanical properties of auricular cartilage

The poor mechanical strength of tissue-engineered auricular cartilage which is possibly due to the lack of perichondrium limits its application in auricular reconstruction surgery. However, there is insufficient research and no reliable data to support this. This study aims to investigate the contribution of perichondrium to the mechanical strength of auricular cartilage under loading. Rabbit auricular cartilage was harvested and classified into two groups. The perichondrium was removed in Group A and was left intact in Group B. Young's modulus, stress relaxation slope, and relaxation amout were analyzed through tensile and compressive tests using a material testing machine. Group B exhibited significantly higher Young's modulus in both the tensile and compressive tests (p < 0.05), lower relaxation slope (p < 0.05 in tensile test, p = 0.65 in compressive test), and lower relaxation amout (p < 0.05 in tensile test, p < 0.01 in compressive test). Our results showed that the perichondrium has a definite contribution to the mechanical properties of ear cartilage. This study may provide new insights to researchers focusing on improving the mechanical strength of tissue-engineered auricular cartilage.

Ethanol treatment of nanoPGA/PCL composite scaffolds enhances human chondrocyte development in the cellular microenvironment of tissue-engineered auricle constructs

A major obstacle for tissue engineering ear-shaped cartilage is poorly developed tissue comprising cell-scaffold constructs. To address this issue, bioresorbable scaffolds of poly-ε-caprolactone (PCL) and polyglycolic acid nanofibers (nanoPGA) were evaluated using an ethanol treatment step before auricular chondrocyte scaffold seeding, an approach considered to enhance scaffold hydrophilicity and cartilage regeneration. Auricular chondrocytes were isolated from canine ears and human surgical samples discarded during otoplasty, including microtia reconstruction. Canine chondrocytes were seeded onto PCL and nanoPGA sheets either with or without ethanol treatment to examine cellular adhesion in vitro. Human chondrocytes were seeded onto three-dimensional bioresorbable composite scaffolds (PCL with surface coverage of nanoPGA) either with or without ethanol treatment and then implanted into athymic mice for 10 and 20 weeks. On construct retrieval, scanning electron microscopy showed canine auricular chondrocytes seeded onto ethanol-treated scaffolds in vitro developed extended cell processes contacting scaffold surfaces, a result suggesting cell-scaffold adhesion and a favorable microenvironment compared to the same cells with limited processes over untreated scaffolds. Adhesion of canine chondrocytes was statistically significantly greater (p ≤ 0.05) for ethanol-treated compared to untreated scaffold sheets. After implantation for 10 weeks, constructs of human auricular chondrocytes seeded onto ethanol-treated scaffolds were covered with glossy cartilage while constructs consisting of the same cells seeded onto untreated scaffolds revealed sparse connective tissue and cartilage regeneration. Following 10 weeks of implantation, RT-qPCR analyses of chondrocytes grown on ethanol-treated scaffolds showed greater expression levels for several cartilage-related genes compared to cells developed on untreated scaffolds with statistically significantly increased SRY-box transcription factor 5 (SOX5) and decreased interleukin-1α (inflammation-related) expression levels (p ≤ 0.05). Ethanol treatment of scaffolds led to increased cartilage production for 20- compared to 10-week constructs. While hydrophilicity of scaffolds was not assessed directly in the present findings, a possible factor supporting the summary data is that hydrophilicity may be enhanced for ethanol-treated nanoPGA/PCL scaffolds, an effect leading to improvement of chondrocyte adhesion, the cellular microenvironment and cartilage regeneration in tissue-engineered auricle constructs.

3D bioprinting in cardiac tissue engineering

Heart disease is the main cause of death worldwide. Because death of the myocardium is irreversible, it remains a significant clinical challenge to rescue myocardial deficiency. Cardiac tissue engineering (CTE) is a promising strategy for repairing heart defects and offers platforms for studying cardiac tissue. Numerous achievements have been made in CTE in the past decades based on various advanced engineering approaches. 3D bioprinting has attracted much attention due to its ability to integrate multiple cells within printed scaffolds with complex 3D structures, and many advancements in bioprinted CTE have been reported recently. Herein, we review the recent progress in 3D bioprinting for CTE. After a brief overview of CTE with conventional methods, the current 3D printing strategies are discussed. Bioink formulations based on various biomaterials are introduced, and strategies utilizing composite bioinks are further discussed. Moreover, several applications including heart patches, tissue-engineered cardiac muscle, and other bionic structures created via 3D bioprinting are summarized. Finally, we discuss several crucial challenges and present our perspective on 3D bioprinting techniques in the field of CTE.

Achievements and Challenges in Transplantation of Mesenchymal Stem Cells in Otorhinolaryngology

Otorhinolaryngology enrolls head and neck surgery in various tissues such as ear, nose, and throat (ENT) that govern different activities such as hearing, breathing, smelling, production of vocal sounds, the balance, deglutition, facial animation, air filtration and humidification, and articulation during speech, while absence of these functions can lead to high morbidity and even mortality. Conventional therapies for head and neck damaged tissues include grafts, transplants, and artificial materials, but grafts have limited availability and cause morbidity in the donor site. To improve these limitations, regenerative medicine, as a novel and rapidly growing field, has opened a new therapeutic window in otorhinolaryngology by using cell transplantation to target the healing and replacement of injured tissues. There is a high risk of rejection and tumor formation for transplantation of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs); mesenchymal stem cells (MSCs) lack these drawbacks. They have easy expansion and antiapoptotic properties with a wide range of healing and aesthetic functions that make them a novel candidate in otorhinolaryngology for craniofacial defects and diseases and hold immense promise for bone tissue healing; even the tissue sources and types of MSCs, the method of cell introduction and their preparation quality can influence the final outcome in the injured tissue. In this review, we demonstrated the anti-inflammatory and immunomodulatory properties of MSCs, from different sources, to be safely used for cell-based therapies in otorhinolaryngology, while their achievements and challenges have been described too.

Hydrogels in the treatment of rheumatoid arthritis: drug delivery systems and artificial matrices for dynamic in vitro models

Rheumatoid arthritis (RA) is an autoimmune and chronic inflammatory disorder that mostly affects the synovial joints and can promote both cartilage and bone tissue destruction. Several conservative treatments are available to relieve pain and control the inflammation; however, traditional drugs administration are not fully effective and present severe undesired side effects. Hydrogels are a very attractive platform as a drug delivery system to guarantee these handicaps are reduced, and the therapeutic effect from the drugs is maximized. Furthermore, hydrogels can mimic the physiological microenvironment and have the mechanical behavior needed for use as cartilage in vitro model. The testing of these advanced delivery systems is still bound to animal disease models that have shown low predictability. Alternatively, hydrogel-based human dynamic in vitro systems can be used to model diseases, bypassing some of the animal testing problems. RA dynamic disease models are still in an embryonary stage since advances regarding healthy and inflamed cartilage models are currently giving the first steps regarding complexity increase. Herein, recent studies using hydrogels in the treatment of RA, featuring different hydrogel formulations are discussed. Besides, their use as artificial extracellular matrices in dynamic in vitro articular cartilage is also reviewed.

Design Challenges in Polymeric Scaffolds for Tissue Engineering

Numerous surgical procedures are daily performed worldwide to replace and repair damaged tissue. Tissue engineering is the field devoted to the regeneration of damaged tissue through the incorporation of cells in biocompatible and biodegradable porous constructs, known as scaffolds. The scaffolds act as host biomaterials of the incubating cells, guiding their attachment, growth, differentiation, proliferation, phenotype, and migration for the development of new tissue. Furthermore, cellular behavior and fate are bound to the biodegradation of the scaffold during tissue generation. This article provides a critical appraisal of how key biomaterial scaffold parameters, such as structure architecture, biochemistry, mechanical behavior, and biodegradability, impart the needed morphological, structural, and biochemical cues for eliciting cell behavior in various tissue engineering applications. Particular emphasis is given on specific scaffold attributes pertaining to skin and brain tissue generation, where further progress is needed (skin) or the research is at a relatively primitive stage (brain), and the enumeration of some of the most important challenges regarding scaffold constructs for tissue engineering.

State of the art of clinical applications of Tissue Engineering in 2021

Tissue engineering (TE) was introduced almost 30 years ago as a potential technique for regenerating human tissues. However, despite promising laboratory findings, the complexity of the human body, scientific hurdles, and lack of persistent long-term funding still hamper its translation towards clinical applications. In this report, we compile an inventory of clinically applied TE medical products relevant to surgery. A review of the literature, including articles published within the period from 1991 to 2020, was performed according to the PRISMA protocol, using databanks PubMed, Cochrane Library, Web of Science, and Clinicaltrials.gov. We identified 1039 full-length articles as eligible; due to the scarcity of clinical, randomised, controlled trials and case studies, we extended our search towards a broad surgical spectrum. Forty papers involved clinical TE studies. Amongst these, 7 were related to TE protocols for cartilage applied in the reconstruction of nose, ear, and trachea. Nine papers reported TE protocols for articular cartilage, 9 for urological purposes, 7 described TE strategies for cardiovascular aims, and 8 for dermal applications. However, only two clinical studies reported on three-dimensional (3D) and functional long-lasting TE constructs. The concept of generating 3D TE constructs and organs based on autologous molecules and cells is intriguing and promising. The first translational tissue-engineered products and techniques have been clinically implemented. However, despite the 30 years of research and development in this field, TE is still in its clinical infancy. Multiple experimental, ethical, budgetary, and regulatory difficulties hinder its rapid translation. Nevertheless, the first clinical applications show great promise and indicate that the translation towards clinical medical implementation has finally started.

Immune-Inflammatory Responses of an Acellular Cartilage Matrix Biomimetic Scaffold in a Xenotransplantation Goat Model for Cartilage Tissue Engineering

The rapid development of tissue engineering and regenerative medicine has introduced a new strategy for ear reconstruction, successfully regenerating human-ear-shaped cartilage and achieving the first clinical breakthrough using a polyglycolic acid/polylactic acid (PGA/PLA) scaffold. However, its clinical repair varies greatly among individuals, and the quality of regenerated cartilage is unstable, which seriously limits further clinical application. Acellular cartilage matrix (ACM), with a cartilage-specific microenvironment, good biocompatibility, and potential to promote cell proliferation, has been used to regenerate homogeneous ear-shaped cartilage in immunocompromised nude mice. However, there is no evidence on whether ACM will regenerate homogeneous cartilage tissue in large animals or has the potential for clinical transformation. In this study, xenogeneic ACM assisted with gelatin (GT) with or without autologous chondrocytes was implanted subcutaneously into goats to establish a xenotransplantation model and compared with a PGA/PLA scaffold to evaluate the immune-inflammatory response and quality of regenerated cartilage. The results confirmed the superiority of the ACM/GT, which has the potential capacity to promote cell proliferation and cartilage formation. Although there is a slight immune-inflammatory response in large animals, it does not affect the quality of the regenerated cartilage and forms homogeneous and mature cartilage. The current study provides detailed insights into the immune-inflammatory response of the xenogeneic ACM/GT and also provides scientific evidence for future clinical application of ACM/GT in cartilage tissue engineering.

Auricular reconstruction: where are we now? A critical literature review

PURPOSE

Deformities of the external ear can affect psychosocial well-being and hearing. Current gold-standard reconstructive treatment is autologous costal cartilage grafting despite the vast morbidity profile. Tissue engineering using stem cells and 3D printing can create patient-specific reconstructed auricles with superior cosmetic outcomes and reduced morbidity. This review critically analyses recent and breakthrough research in the field of regenerative medicine for the pinna, considering gaps in current literature and suggesting further steps to identify whether this could be the new gold-standard.

METHODS

A literature review was conducted. PubMed (MEDLINE) and Cochrane databases were searched using key terms regenerative medicine, tissue engineering, 3D printing, biofabrication, auricular reconstruction, auricular cartilage, chondrocyte, outer ear and pinna. Studies in which tissue-engineered auricles were implanted into animal or human subjects were included. Exclusion criteria included articles not in English and not published within the last ten years. Titles, abstracts and full texts were screened. Reference searching was conducted and significant breakthrough studies included.

RESULTS

8 studies, 6 animal and 2 human, were selected for inclusion. Strengths and weaknesses of each are discussed. Common limitations include a lack of human studies, small sample sizes and short follow-up times.

CONCLUSION

Regenerative medicine holds significant potential to improve auricular reconstruction. To date there are no large multi-centred human studies in which tissue-engineered auricles have been implanted. However, recent human studies suggest promising results, raising the ever-growing possibility that tissue engineering is the future of auricular reconstruction. We aim to continue developing knowledge in this field.

Hybrid Three-Dimensional-Printed Ear Tissue Scaffold With Autologous Cartilage Mitigates Soft Tissue Complications

OBJECTIVES/HYPOTHESIS

To analyze the use of highly translatable three-dimensional (3D)-printed auricular scaffolds with and without novel cartilage tissue inserts in a rodent model.

STUDY DESIGN

Preclinical rodent animal model.

METHODS

This prospective study assessed a single-stage 3D-printed auricular bioscaffold with or without porcine cartilage tissue inserts in an athymic rodent model. Digital Imaging and Communications in Medicine computed tomography images of a human auricle were segmented to create an external anatomic envelope filled with orthogonally interconnected spherical pores. Scaffolds with and without tissue inset sites were 3D printed by laser sintering bioresorbable polycaprolactone, then implanted subcutaneously in five rats for each group.

RESULTS

Ten athymic rats were studied to a goal of 24 weeks postoperatively. Precise anatomic similarity and scaffold integrity were maintained in both scaffold conditions throughout experimentation with grossly visible tissue ingrowth and angiogenesis upon explantation. Cartilage-seeded scaffolds had relatively lower rates of nonsurgical site complications compared to unseeded scaffolds with relatively increased surgical site ulceration, though neither met statistical significance. Histology revealed robust soft tissue infiltration and vascularization in both seeded and unseeded scaffolds, and demonstrated impressive maintenance of viable cartilage in cartilage-seeded scaffolds. Radiology confirmed soft tissue infiltration in all scaffolds, and biomechanical modeling suggested amelioration of stress in scaffolds implanted with cartilage.

CONCLUSIONS

A hybrid approach incorporating cartilage insets into 3D-printed bioscaffolds suggests enhanced clinical and histological outcomes. These data demonstrate the potential to integrate point-of-care tissue engineering techniques into 3D printing to generate alternatives to current reconstructive surgery techniques and avoid the demands of traditional tissue engineering.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:1008-1015, 2021.

Improving In Vitro Cartilage Generation by Co-Culturing Adipose-Derived Stem Cells and Chondrocytes on an Allograft Adipose Matrix Framework

BACKGROUND

Microtia is an inherited condition that results in varying degrees of external ear deformities; the most extreme form is anotia. Effective surgical reconstruction techniques have been developed. However, these usually require multistage procedures and have other inherent disadvantages. Tissue engineering technologies offer new approaches in the field of external ear reconstruction. In this setting, chondrocytes are cultured in the laboratory with the aim of creating bioengineered cartilage matrices. However, cartilage engineering has many challenges, including difficulty in culturing sufficient chondrocytes. To overcome these hurdles, the authors propose a novel model of cartilage engineering that involves co-culturing chondrocytes and adipose-derived stem cells on an allograft adipose-derived extracellular matrix scaffold.

METHODS

Auricular chondrocytes from porcine ear were characterized. Adipose-derived stem cells were isolated and expanded from human lipoaspirate. Then, the auricular chondrocytes were cultured on the allograft adipose matrix either alone or with the adipose-derived stem cells at different ratios and examined histologically.

RESULTS

Cartilage induction was most prominent when the cells were co-cultured on the allograft adipose matrix at a ratio of 1:9 (auricular chondrocyte-to-adipose-derived stem cell ratio). Furthermore, because of the xenogeneic nature of the experiment, the authors were able to determine that the adipose-derived stem cells contributed to chondrogenesis by means of a paracrine stimulation of the chondrocytes.

CONCLUSIONS

In this situation, adipose-derived stem cells provide sufficient support to induce the formation of cartilage when the number of auricular chondrocytes available is limited. This novel model of cartilage engineering provides a setting for using the patient's own chondrocytes and adipose tissue to create a customized ear framework that could be further used for surgical reconstruction.

Ex Vivo Generation and Characterization of Human Hyaline and Elastic Cartilaginous Microtissues for Tissue Engineering Applications

Considering the high prevalence of cartilage-associated pathologies, low self-repair capacity and limitations of current repair techniques, tissue engineering (TE) strategies have emerged as a promising alternative in this field. Three-dimensional culture techniques have gained attention in recent years, showing their ability to provide the most biomimetic environment for the cells under culture conditions, enabling the cells to fabricate natural, 3D functional microtissues (MTs). In this sense, the aim of this study was to generate, characterize and compare scaffold-free human hyaline and elastic cartilage-derived MTs (HC-MTs and EC-MTs, respectively) under expansion (EM) and chondrogenic media (CM). MTs were generated by using agarose microchips and evaluated ex vivo for 28 days. The MTs generated were subjected to morphometric assessment and cell viability, metabolic activity and histological analyses. Results suggest that the use of CM improves the biomimicry of the MTs obtained in terms of morphology, viability and extracellular matrix (ECM) synthesis with respect to the use of EM. Moreover, the overall results indicate a faster and more sensitive response of the EC-derived cells to the use of CM as compared to HC chondrocytes. Finally, future preclinical in vivo studies are still needed to determine the potential clinical usefulness of these novel advanced therapy products.

Recent advances in bioprinting technologies for engineering different cartilage-based tissues

Inadequate self-repair and regenerative efficiency of the cartilage tissues has motivated the researchers to devise advanced and effective strategies to resolve this issue. Introduction of bioprinting to tissue engineering has paved the way for fabricating complex biomimetic engineered constructs. In this context, the current review gears off with the discussion of standard and advanced 3D/4D printing technologies and their implications for the repair of different cartilage tissues, namely, articular, meniscal, nasoseptal, auricular, costal, and tracheal cartilage. The review is then directed towards highlighting the current stem cell opportunities. On a concluding note, associated critical issues and prospects for future developments, particularly in this sphere of personalized medicines have been discussed.

3D Cartilage Regeneration With Certain Shape and Mechanical Strength Based on Engineered Cartilage Gel and Decalcified Bone Matrix

Scaffold-free cartilage-sheet technology can stably regenerate high-quality cartilage tissue in vivo. However, uncontrolled shape maintenance and mechanical strength greatly hinder its clinical translation. Decalcified bone matrix (DBM) has high porosity, a suitable pore structure, and good biocompatibility, as well as controlled shape and mechanical strength. In this study, cartilage sheet was prepared into engineered cartilage gel (ECG) and combined with DBM to explore the feasibility of regenerating 3D cartilage with controlled shape and mechanical strength. The results indicated that ECG cultured in vitro for 3 days (3 d) and 15 days (15 d) showed good biocompatibility with DBM, and the ECG–DBM constructs successfully regenerated viable 3D cartilage with typical mature cartilage features in both nude mice and autologous goats. Additionally, the regenerated cartilage had comparable mechanical properties to native cartilage and maintained its original shape. To further determine the optimal seeding parameters for ECG, the 3 d ECG regenerated using human chondrocytes was diluted in different concentrations (1:3, 1:2, and 1:1) for seeding and in vivo implantation. The results showed that the regenerated cartilage in the 1:2 group exhibited better shape maintenance and homogeneity than the other groups. The current study established a novel mode of 3D cartilage regeneration based on the design concept of steel (DBM)-reinforced concrete (ECG) and successfully regenerated homogenous and mature 3D cartilage with controlled shape and mechanical strength, which hopefully provides an ideal cartilage graft for the repair of various cartilage defects.

[In vitro regeneration of tissue engineered cartilage and its clinical application for nasal reconstruction]

OBJECTIVE

To explore the clinical application and effectiveness of a personalized tissue engineered cartilage with seed cells derived from ear or nasal septal cartilage and poly-glycolic acid (PGA)/poly-lactic acid (PLA) as scaffold in patients with nasal reconstruction.

METHODS

Between March 2014 and October 2015, 4 cases of acquired nasal defects and 1 case of congenital nasal deformity were admitted. The patient with congenital nasal deformity was a 4-year-old boy, and the source of seed cells was nasal septal cartilage. The other 4 patients were 3 males and 1 female, aged 24-33 years, with an average of 28.5 years. They all had multiple nasal subunit defects caused by trauma and the source of seed cells was auricular cartilage. The tissue engineered cartilage framework was constructed in the shape of normal human nasal alar cartilage and L-shaped silicone prosthesis with seed cells from cartilage and PGA-PLA compound biodegradable scaffold. The boy underwent nasal deformity correction and silicone prosthesis implantation in the first stage, and the prosthesis was removed and implanted with tissue engineered cartilage in the second stage; the remaining 4 adult patients all used expanded forehead flaps for nasal reconstruction. All 5 patients underwent 1-4 nasal revisions. The implanted tissue engineered cartilage was observed during the operation and taken from 2 patients for histological examination.

RESULTS

All the incisions healed by first intention after the tissue engineered cartilage implantation, and the expanded forehead flaps survived. Postoperative low fever occurred in 3 patients. No complications such as infection, obvious immune rejection response, and tissue engineered cartilage protrusion were found in all patients. All patients were followed up 9-74 months (mean，54.8 months). During follow-up, the patients had no obvious discomfort in the nose and the ventilation function were good. All patients were satisfied with the nasal contour. Early-stage histological examination showed the typical cartilage characteristics in 1 patient after the implantation of tissue engineered cartilage. Late-stage histological examination in 1 patient of tissue engineered cartilage showed the characteristics of fibrous connective tissue; and the other showed there was remaining cartilage.

CONCLUSION

The safety of tissue engineered cartilage constructed in vitro for reconstruction is preliminarily confirmed, but the effectiveness still needs further verification.

Design of Temperature-Responsive Cell Culture Surfaces for Cell Sheet Engineering

Temperature-responsive cell culture surfaces, which modulate cell attachment/detachment characteristics with temperature, have been used to fabricate cell sheets. Extensive study on fabrication of cell sheet with the temperature-responsive cell culture surface, manipulation, and transplantation of the cell sheet has established the interdisciplinary field of cell sheet engineering, in which engineering, biological, and medical fields closely collaborate. Such collaboration has pioneered cell sheet engineering, making it a promising and attractive technology in tissue engineering and regenerative medicine. This review introduces concepts of cell sheet engineering, followed by designs for the fabrication of various types of temperature-responsive cell culture surfaces and technologies for cell sheet manipulation. The development of various methods for the fabrication of temperature-responsive cell culture surfaces was also summarized. The availability of cell sheet engineering for the treatment and regeneration of damaged human tissue has also been described, providing examples of the clinical application of cell sheet transplantation in humans.

PLLA Porous Microsphere-Reinforced Silk-Based Scaffolds for Auricular Cartilage Regeneration

Microtia, frequently encountered in plastic surgery practice, is usually corrected by auricular reconstruction with prostheses or autologous cartilages. In recent decades, however, cartilage tissue engineering has been emerging as a promising alternative for its minimal invasion and low immunogenicity. As a critical factor for tissue engineering, scaffolds are expected to be sufficiently porous and stiff to facilitate chondrogenesis. In this work, we introduce novel poly-l-lactic acid (PLLA) porous microsphere-reinforced silk-based hybrid (SBH) scaffolds with a multihierarchical porous structure. The scaffolds are fabricated by embedding PLLA porous microspheres (PMs) into a blending matrix of silk fibroin (SF) and gelatin solution, followed by mixing with a degummed silk fiber mesh and freeze-drying process. Through adjusting the amount of PLLA PMs, the mechanical strength approximates to natural cartilage and also balanced physical properties were realized. Biological evaluations of SBH scaffolds, both in vitro and in vivo, were conducted and PM-free plain silk-based (PSB) scaffolds were applied as control. Overall, it suggests that the incorporation of PLLA PMs remarkably improves mechanical properties and the capability to promote chondrogenesis of SBH scaffolds, and that SBH scaffolds appear to be a promising construct for potential applications in auricular cartilage tissue engineering and relevant fields.

Precision Medicine in Ossiculoplasty

INTRODUCTION

Long term results of ossiculoplasty surgery are considered poor with displacement and extrusion amongst the common reasons for failure. Application of 3Dimensional (3D) printing may help overcome some of these barriers, however digital methods to attain accurate 3D morphological studies of ossicular anatomy are lacking, exacerbated by the limitation of resolution of clinical imaging.

METHODS

20 human cadaveric temporal bones were assessed using micro computed tomography (CT) imaging to demonstrate the lowest resolution required for accurate 3D reconstruction. The bones were then scanned using conebeam CT (125 μm) and helical CT (0.6 mm). 3D reconstruction using clinical imaging techniques with microCT imaging (40 μm resolution) as a reference was assessed. The incus was chosen as the focus of study. Two different methods of 3D printing techniques were assessed.

RESULTS

A minimum resolution of 100 μm was needed for adequate 3D reconstruction of the ossicular chain. Conebeam CT gave the most accurate data on 3D analysis, producing the smallest mean variation in surface topography data relative to microCT (mean difference 0.037 mm, p < 0.001). Though the incus varied in shape in between people, paired matches were identical. Thus, the contralateral side can be used for 3D printing source data if the ipsilateral incus is missing. Laser based 3D printing was superior to extrusion based printing to achieve the resolution demands for 3D printed ossicles.

CONCLUSION

Resolution of modern imaging allows 3D reconstructions and 3D printing of human ossicles with good accuracy, though it is important to pay attention to thresholding during this process.

A photo-crosslinkable cartilage-derived extracellular matrix bioink for auricular cartilage tissue engineering

Three-dimensional (3D) bioprinting of patient-specific auricular cartilage constructs could aid in the reconstruction process of traumatically injured or congenitally deformed ear cartilage. To achieve this, a hydrogel-based bioink is required that recapitulates the complex cartilage microenvironment. Tissue-derived decellularized extracellular matrix (dECM)-based hydrogels have been used as bioinks for cell-based 3D bioprinting because they contain tissue-specific ECM components that play a vital role in cell adhesion, growth, and differentiation. In this study, porcine auricular cartilage tissues were isolated and decellularized, and the decellularized cartilage tissues were characterized by histology, biochemical assay, and proteomics. This cartilage-derived dECM (cdECM) was subsequently processed into a photo-crosslinkable hydrogel using methacrylation (cdECMMA) and mixed with chondrocytes to create a printable bioink. The rheological properties, printability, and in vitro biological properties of the cdECMMA bioink were examined. The results showed cdECM was obtained with complete removal of cellular components while preserving major ECM proteins. After methacrylation, the cdECMMA bioinks were printed in anatomical ear shape and exhibited adequate mechanical properties and structural integrity. Specifically, auricular chondrocytes in the printed cdECMMA hydrogel constructs maintained their viability and proliferation capacity and eventually produced cartilage ECM components, including collagen and glycosaminoglycans (GAGs). The potential of cell-based bioprinting using this cartilage-specific dECMMA bioink is demonstrated as an alternative option for auricular cartilage reconstruction.

3D Printed Biomimetic PCL Scaffold as Framework Interspersed With Collagen for Long Segment Tracheal Replacement

The rapid development of tissue engineering technology has provided new methods for tracheal replacement. However, none of the previously developed biomimetic tracheas exhibit both the anatomy (separated-ring structure) and mechanical behavior (radial rigidity and longitudinal flexibility) mimicking those of native trachea, which greatly restricts their clinical application. Herein, we proposed a biomimetic scaffold with a separated-ring structure: a polycaprolactone (PCL) scaffold with a ring-hollow alternating structure was three-dimensionally printed as a framework, and collagen sponge was embedded in the hollows amid the PCL rings by pouring followed by lyophilization. The biomimetic scaffold exhibited bionic radial rigidity based on compressive tests and longitudinal flexibility based on three-point bending tests. Furthermore, the biomimetic scaffold was recolonized by chondrocytes and developed tracheal cartilage in vitro. In vivo experiments showed substantial deposition of tracheal cartilage and formation of a biomimetic trachea mimicking the native trachea both structurally and mechanically. Finally, a long-segment tracheal replacement experiment in a rabbit model showed that the engineered biomimetic trachea elicited a satisfactory repair outcome. These results highlight the advantage of a biomimetic trachea with a separated-ring structure that mimics the native trachea both structurally and mechanically and demonstrates its promise in repairing long-segment tracheal defects.

Biofabrication of a shape-stable auricular structure for the reconstruction of ear deformities

Bioengineering of the human auricle remains a significant challenge, where the complex and unique shape, the generation of high-quality neocartilage, and shape preservation are key factors. Future regenerative medicine–based approaches for auricular cartilage reconstruction will benefit from a smart combination of various strategies. Our approach to fabrication of an ear-shaped construct uses hybrid bioprinting techniques, a recently identified progenitor cell population, previously validated biomaterials, and a smart scaffold design. Specifically, we generated a 3D-printed polycaprolactone (PCL) scaffold via fused deposition modeling, photocrosslinked a human auricular cartilage progenitor cell–laden gelatin methacryloyl (gelMA) hydrogel within the scaffold, and cultured the bioengineered structure in vitro in chondrogenic media for 30 days. Our results show that the fabrication process maintains the viability and chondrogenic phenotype of the cells, that the compressive properties of the combined PCL and gelMA hybrid auricular constructs are similar to native auricular cartilage, and that biofabricated hybrid auricular structures exhibit excellent shape fidelity compared with the 3D digital model along with deposition of cartilage-like matrix in both peripheral and central areas of the auricular structure. Our strategy affords an anatomically enhanced auricular structure with appropriate mechanical properties, ensures adequate preservation of the auricular shape during a dynamic in vitro culture period, and enables chondrogenically potent progenitor cells to produce abundant cartilage-like matrix throughout the auricular construct. The combination of smart scaffold design with 3D bioprinting and cartilage progenitor cells holds promise for the development of clinically translatable regenerative medicine strategies for auricular reconstruction.

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First application of human auricular cartilage progenitor cells for bioprinting.

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Dual-printing of hybrid ear-shaped constructs with excellent shape fidelity over time.

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Strategy and design ensured adequate deposition of cartilage-like matrix throughout large auricular constructs.

Biosafety evaluation of culture-expanded human chondrocytes with growth factor cocktail: a preclinical study

The scarcity of chondrocytes is a major challenge for cartilage tissue engineering. Monolayer expansion is necessary to amplify the limited number of chondrocytes needed for clinical application. Growth factors are often added to improve monolayer culture conditions, promoting proliferation, and enhancing chondrogenesis. Limited knowledge on the biosafety of the cell products manipulated with growth factors in culture has driven this study to evaluate the impact of growth factor cocktail supplements in chondrocyte culture medium on chondrocyte genetic stability and tumorigenicity. The growth factors were basic fibroblast growth factor (b-FGF), transforming growth factor β2 (TGF β2), insulin-like growth factor 1 (IGF-1), insulin-transferrin-selenium (ITS), and platelet-derived growth factor (PD-GF). Nasal septal chondrocytes cultured in growth factor cocktail exhibited a significantly high proliferative capacity. Comet assay revealed no significant DNA damage. Flow cytometry showed chondrocytes were mostly at G0-G1 phase, exhibiting normal cell cycle profile with no aneuploidy. We observed a decreased tumour suppressor genes’ expression (p53, p21, pRB) and no TP53 mutations or tumour formation after 6 months of implantation in nude mice. Our data suggest growth factor cocktail has a low risk of inducing genotoxic and tumorigenic effects on chondrocytes up to passage 6 with 16.6 population doublings. This preclinical tumorigenicity and genetic instability evaluation is crucial for further clinical works.

3D Bioprinting and the Future of Surgery

Introduction: The disciplines of 3D bioprinting and surgery have witnessed incremental transformations over the last century. 3D bioprinting is a convergence of biology and engineering technologies, mirroring the clinical need to produce viable biological tissue through advancements in printing, regenerative medicine and materials science. To outline the current and future challenges of 3D bioprinting technology in surgery. Methods: A comprehensive literature search was undertaken using the MEDLINE, EMBASE and Google Scholar databases between 2000 and 2019. A narrative synthesis of the resulting literature was produced to discuss 3D bioprinting, current and future challenges, the role in personalized medicine and transplantation surgery and the global 3D bioprinting market. Results: The next 20 years will see the advent of bioprinted implants for surgical use, however the path to clinical incorporation will be fraught with an array of ethical, regulatory and technical challenges of which each must be surmounted. Previous clinical cases where regulatory processes have been bypassed have led to poor outcomes and controversy. Speculated roles of 3D bioprinting in surgery include the production of de novo organs for transplantation and use of autologous cellular material for personalized medicine. The promise of these technologies has sparked an industrial revolution, leading to an exponential growth of the 3D bioprinting market worth billions of dollars. Conclusion: Effective translation requires the input of scientists, engineers, clinicians, and regulatory bodies: there is a need for a collaborative effort to translate this impactful technology into a real-world healthcare setting and potentially transform the future of surgery.

A photo-crosslinkable cartilage-derived extracellular matrix bioink for auricular cartilage tissue engineering

Three-dimensional (3D) bioprinting of patient-specific auricular cartilage constructs could aid in the reconstruction process of traumatically injured or congenitally deformed ear cartilage. To achieve this, a hydrogel-based bioink is required that recapitulates the complex cartilage microenvironment. Tissue-derived decellularized extracellular matrix (dECM)-based hydrogels have been used as bioinks for cell-based 3D bioprinting because they contain tissue-specific ECM components that play a vital role in cell adhesion, growth, and differentiation. In this study, porcine auricular cartilage tissues were isolated and decellularized, and the decellularized cartilage tissues were characterized by histology, biochemical assay, and proteomics. This cartilage-derived dECM (cdECM) was subsequently processed into a photo-crosslinkable hydrogel using methacrylation (cdECMMA) and mixed with chondrocytes to create a printable bioink. The rheological properties, printability, and in vitro biological properties of the cdECMMA bioink were examined. The results showed cdECM was obtained with complete removal of cellular components while preserving major ECM proteins. After methacrylation, the cdECMMA bioinks were printed in anatomical ear shape and exhibited adequate mechanical properties and structural integrity. Specifically, auricular chondrocytes in the printed cdECMMA hydrogel constructs maintained their viability and proliferation capacity and eventually produced cartilage ECM components, including collagen and glycosaminoglycans (GAGs). The potential of cell-based bioprinting using this cartilage-specific dECMMA bioink is demonstrated as an alternative option for auricular cartilage reconstruction.

Development of a Method for Scaffold-Free Elastic Cartilage Creation

Microtia is a congenital aplasia of the auricular cartilage. Conventionally, autologous costal cartilage grafts are collected and shaped for transplantation. However, in this method, excessive invasion occurs due to limitations in the costal cartilage collection. Due to deformation over time after transplantation of the shaped graft, problems with long-term morphological maintenance exist. Additionally, the lack of elasticity with costal cartilage grafts is worth mentioning, as costal cartilage is a type of hyaline cartilage. Medical plastic materials have been transplanted as alternatives to costal cartilage, but transplant rejection and deformation over time are inevitable. It is imperative to create tissues for transplantation using cells of biological origin. Hence, cartilage tissues were developed using a biodegradable scaffold material. However, such materials suffer from transplant rejection and biodegradation, causing the transplanted cartilage tissue to deform due to a lack of elasticity. To address this problem, we established a method for creating elastic cartilage tissue for transplantation with autologous cells without using scaffold materials. Chondrocyte progenitor cells were collected from perichondrial tissue of the ear cartilage. By using a multilayer culture and a three-dimensional rotating suspension culture vessel system, we succeeded in creating scaffold-free elastic cartilage from cartilage progenitor cells.

Porous fish collagen for cartilage tissue engineering

Cartilage defects repair is still a challenge in clinical practice until now. Although many breakthroughs have been achieved in cartilage repair using tissue engineering technology, there are still no scaffolds available for large-scale clinical applications. Currently, fish collagen (FC) is a natural source that is considered as an alternative to mammal-derived collagen in engineering cartilage tissue due to its excellent biocompatibility, suitable biodegradability, lack of immunogenicity, rich sources, low cost and minimal risk of transmitting zoonoses, which implies great potential for use in cartilage regeneration. Herein, we successfully prepared three-dimensional porous FC scaffolds from three different concentrations of FC (0.5%, 1% and 2%) by freeze-drying technology. Our results indicated that increasing the FC concentration resulted in comparable levels of suitable biodegradability and good biocompatibility but lead to a concurrent decrease in pore size and porosity and a significant increase in water absorption capacity and mechanical properties; further, initial scaffold dimension was only sustained in the 2% FC concentration. Moreover, the in vivo immunological evaluation suggested that the FC scaffold evoke low immunogenicity. In addition, our results confirmed that the porous FC scaffold facilitated cartilage formation both in vitro and when placed subcutaneously in rabbits. The gross and autopsy outcomes at 12 weeks postoperation suggested that the porous FC scaffold achieved superior cartilage repair effect than what was observed in the empty group with no scaffold. Overall, our results demonstrated that porous FC scaffolds represent a promising prospective natural material for use in engineering cartilage for clinical applications.

Bioprinting: From Tissue and Organ Development to in Vitro Models

Bioprinting techniques have been flourishing in the field of biofabrication with pronounced and exponential developments in the past years. Novel biomaterial inks used for the formation of bioinks have been developed, allowing the manufacturing of in vitro models and implants tested preclinically with a certain degree of success. Furthermore, incredible advances in cell biology, namely, in pluripotent stem cells, have also contributed to the latest milestones where more relevant tissues or organ-like constructs with a certain degree of functionality can already be obtained. These incredible strides have been possible with a multitude of multidisciplinary teams around the world, working to make bioprinted tissues and organs more relevant and functional. Yet, there is still a long way to go until these biofabricated constructs will be able to reach the clinics. In this review, we summarize the main bioprinting activities linking them to tissue and organ development and physiology. Most bioprinting approaches focus on mimicking fully matured tissues. Future bioprinting strategies might pursue earlier developmental stages of tissues and organs. The continuous convergence of the experts in the fields of material sciences, cell biology, engineering, and many other disciplines will gradually allow us to overcome the barriers identified on the demanding path toward manufacturing and adoption of tissue and organ replacements.

Past, Present, and Future of Soft-Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing

Millions of people worldwide experience disfigurement due to cancers, congenital defects, or trauma, leading to significant psychological, social, and economic disadvantage. Prosthetics aim to reduce their suffering by restoring aesthetics and function using synthetic materials that mimic the characteristics of native tissue. In the 1900s, natural materials used for thousands of years in prosthetics were replaced by synthetic polymers bringing about significant improvements in fabrication and greater realism and utility. These traditional methods have now been disrupted by the advanced manufacturing revolution, radically changing the materials, methods, and nature of prosthetics. In this report, traditional synthetic polymers and advanced prosthetic materials and manufacturing techniques are discussed, including a focus on prosthetic material degradation. New manufacturing approaches and future technological developments are also discussed in the context of specific tissues requiring aesthetic restoration, such as ear, nose, face, eye, breast, and hand. As advanced manufacturing moves from research into clinical practice, prosthetics can begin new age to significantly improve the quality of life for those suffering tissue loss or disfigurement.

Tissue engineering: from the bedside to the bench and back to the bedside

The field of Tissue Engineering and Regenerative Medicine has evolved rapidly over the past thirty years. This review will summarize its history, current status and direction through the lens of clinical need, its progress through science in the laboratory and application back into patients. We can take pride in the fact that much effort and progress began with the surgical problems of children and that many surgeons in the pediatric surgical specialties have become pioneers and investigators in this new field of science, engineering, and medicine. Although the field has yet to fulfill its great promise, there have been several examples where a therapy has progressed from the first idea to human application within a short span of time and, in many cases, it has been applied in the surgical care of children.

Protein profile of ear auricle cartilage and the important role of ITGB1/PTK2 in microtia

BACKGROUND

Microtia is a congenital malformation of the external ear that involves anything from a small reduction in size to a complete absence. The external ear is composed of elastic cartilage which is also the important skeleton of the outer ear. However no previous study explored the difference between abnormal elastic cartilage and normal cartilage in the molecular level.

METHODS

Microtia cartilage and normal cartilage tissue samples from patients subjected to autologous costal cartilage reconstruction were obtained in surgery. Total proteins were extracted and purified, and then proteomic analyzed via LC-MS/MS using DDA/DIA data collection methods. Proteins were also isolated with lysis beads and then analyzed via antibody chip. Differentially expressed proteins were identified in both experiments and further analyzed with functional enrichment analysis and KEGG pathway analysis. Valuable regulatory gene expression level was verified by RT-PCR.

RESULTS

A total of 4178 protein types were identified in the DDA experiment. A total of 2154 proteins were quantified, 172 of which were significantly upregulated and 82 downregulated in the microtia group (P < 0.05). Antibody chip detection allowed identification of 584 protein phosphorylation sites with 102 upregulation sites and 9 downregulation sites (P < 0.05). Differentially altered proteins were annotated to 143 KEGG pathways, while differentiated phosphate site-associated genes were annotated into 21 KEGG pathways. Two intersecting pathways, the PI3K/AKT/mTOR pathway and the focal adhesion pathway, may paly important role on ear auricle cartilage development. One item is significant in both differential protein expression and phosphorylation. Integrin beta-1, that is downregulated in protein quantification of the microtia group. The mean ITGB1 mRNA level of the microtia patient group was significantly lower than in the healthy control group (P = 0.0007 < 0.05). And the gene expression of downstream gene PTK2 was also decreased. (P = 0.0288 < 0.05).

CONCLUSION

The research locates the key protein Integrin Beta-1, and verified it at the mRNA level. The increasing level of ITGB1 and decreasing of PTK2 may play an important role in congenital ear deformity. This research will inspire more otolaryngologists and orthopedics doctors to pay attention to the etiology and mechanism of microtia.

Adipose-derived mesenchymal stem cell seeded Atelocollagen scaffolds for cardiac tissue engineering

ADMSCs were isolated from subcutaneous adipose tissue, characterized and cultured in vitro. GFP-labeled ADMSCs can grow and proliferate well on the Atelocollagen scaffolds, and induced by 5-aza the cells can differentiate into cardio-like cells. 3D cultured ADMSCs on Atelocollagen scaffolds were transplanted into mice ischemia myocardium, and have good biocompatibility with host cardio tissue.

Review of Plastic Surgery Biomaterials and Current Progress in Their 3D Manufacturing Technology

Plastic surgery is a broad field, including maxillofacial surgery, skin flaps and grafts, liposuction and body contouring, breast surgery, and facial cosmetic procedures. Due to the requirements of plastic surgery for the biological safety of materials, biomaterials are widely used because of its superior biocompatibility and biodegradability. Currently, there are many kinds of biomaterials clinically used in plastic surgery and their applications are diverse. Moreover, with the rise of three-dimensional printing technology in recent years, the macroscopically more precise and personalized bio-scaffolding materials with microporous structure have made good progress, which is thought to bring new development to biomaterials. Therefore, in this paper, we reviewed the plastic surgery biomaterials and current progress in their 3D manufacturing technology.

Cartilage tissue engineering for craniofacial reconstruction

Severe cartilage defects and congenital anomalies affect millions of people and involve considerable medical expenses. Tissue engineering offers many advantages over conventional treatments, as therapy can be tailored to specific defects using abundant bioengineered resources. This article introduces the basic concepts of cartilage tissue engineering and reviews recent progress in the field, with a focus on craniofacial reconstruction and facial aesthetics. The basic concepts of tissue engineering consist of cells, scaffolds, and stimuli. Generally, the cartilage tissue engineering process includes the following steps: harvesting autologous chondrogenic cells, cell expansion, redifferentiation, in vitro incubation with a scaffold, and transfer to patients. Despite the promising prospects of cartilage tissue engineering, problems and challenges still exist due to certain limitations. The limited proliferation of chondrocytes and their tendency to dedifferentiate necessitate further developments in stem cell technology and chondrocyte molecular biology. Progress should be made in designing fully biocompatible scaffolds with a minimal immune response to regenerate tissue effectively.

Current challenges in three-dimensional bioprinting heart tissues for cardiac surgery

SUMMARY

Previous attempts in cardiac bioengineering have failed to provide tissues for cardiac regeneration. Recent advances in 3-dimensional bioprinting technology using prevascularized myocardial microtissues as 'bioink' have provided a promising way forward. This review guides the reader to understand why myocardial tissue engineering is difficult to achieve and how revascularization and contractile function could be restored in 3-dimensional bioprinted heart tissue using patient-derived stem cells.

Tissue engineering applications in otolaryngology-The state of translation

While tissue engineering holds significant potential to address current limitations in reconstructive surgery of the head and neck, few constructs have made their way into routine clinical use. In this review, we aim to appraise the state of head and neck tissue engineering over the past five years, with a specific focus on otologic, nasal, craniofacial bone, and laryngotracheal applications. A comprehensive scoping search of the PubMed database was performed and over 2000 article hits were returned with 290 articles included in the final review. These publications have addressed the hallmark characteristics of tissue engineering (cellular source, scaffold, and growth signaling) for head and neck anatomical sites. While there have been promising reports of effective tissue engineered interventions in small groups of human patients, the majority of research remains constrained to in vitro and in vivo studies aimed at furthering the understanding of the biological processes involved in tissue engineering. Further, differences in functional and cosmetic properties of the ear, nose, airway, and craniofacial bone affect the emphasis of investigation at each site. While otolaryngologists currently play a role in tissue engineering translational research, continued multidisciplinary efforts will likely be required to push the state of translation towards tissue-engineered constructs available for routine clinical use.

LEVEL OF EVIDENCE

NA.

Modeling Normal and Pathological Ear Cartilage in vitro Using Somatic Stem Cells in Three-Dimensional Culture

Microtia (underdeveloped ear) is a rare congenital dysmorphology affecting the development of the outer ear. Although human microtic cartilage has not been fully characterized, chondrogenic cells derived from this tissue have been proposed as a suitable source for autologous auricular reconstruction. The aim of this study was to further characterize native microtic cartilage and investigate the properties of cartilage stem/progenitor cells (CSPCs) derived from it. Two-dimensional (2D) systems are most commonly used to assess the chondrogenic potential of somatic stem cells in vitro, but limit cell interactions and differentiation. Hence here we investigated the behavior of microtic CSPCs in three-dimensional spheroid cultures. Remarkable similarities between human microtic cartilages from five patients, as compared to normal cartilage, were observed notwithstanding possibly different etiologies of the disease. Native microtic cartilage displayed poorly defined perichondrium and hyper-cellularity, an immature phenotype that resembled that of the normal developing human auricular cartilage we studied in parallel. Crucially, our analysis of microtic ears revealed for the first time that, unlike normal cartilage, microtic cartilages are vascularized. Importantly, CSPCs isolated from human microtic and normal ear cartilages were found to recapitulate many characteristics of pathological and healthy tissues, respectively, when allowed to differentiate as spheroids, but not in monolayer cultures. Noteworthily, starting from initially homogeneous cell pellets, CSPC spheroids spontaneously underwent a maturation process in culture, and formed two regions (inner and outer region) separated by a boundary, with distinct cell types that differed in chondrogenic commitment as indicated by expression of chondrogenic markers. Compared to normal ear-derived spheroids, microtic spheroids were asymmetric, hyper-cellularized and the inner and outer regions did not develop properly. Hence, their organization resembled that of native microtic cartilage. Together, our results identify novel features of microtic ears and highlight the importance of 3D self-organizing in vitro systems for better understanding somatic stem cell behavior and disease modeling. Our observations of ear-derived chondrogenic stem cell behavior have implications for choice of cells for tissue engineered reconstructive purposes and for modeling the etiopathogenesis of microtia.

An analytical study of neocartilage from microtia and otoplasty surgical remnants: A possible application for BMP7 in microtia development and regeneration

To investigate auricular reconstruction by tissue engineering means, this study compared cartilage regenerated from human chondrocytes obtained from either microtia or normal (conchal) tissues discarded from otoplasties. Isolated cells were expanded in vitro, seeded onto nanopolyglycolic acid (nanoPGA) sheets with or without addition of bone morphogenetic protein-7 (BMP7), and implanted in nude mice for 10 weeks. On specimen harvest, cartilage development was assessed by gross morphology, histology, and RT-qPCR and microarray analyses. Neocartilages from normal and microtia surgical tissues were found equivalent in their dimensions, qualitative degree of proteoglycan and elastic fiber staining, and quantitative gene expression levels of types II and III collagen, elastin, and SOX5. Microarray analysis, applied for the first time for normal and microtia neocartilage comparison, yielded no genes that were statistically significantly different in expression between these two sample groups. These results support use of microtia tissue as a cell source for normal auricular reconstruction. Comparison of normal and microtia cells, each seeded on nanoPGA and supplemented with BMP7 in a slow-release hydrogel, showed statistically significant differences in certain genes identified by microarray analysis. Such differences were also noted in several analyses comparing counterpart seeded cells without BMP7. Summary data suggest a possible application for BMP7 in microtia cartilage regeneration and encourage further studies to elucidate whether such genotypic differences translate to phenotypic characteristics of the human microtic ear. The present work advances understanding relevant to the potential clinical use of microtia surgical remnants as a suitable cell source for tissue engineering of the pinna.

Creating Cartilage in Tissue-Engineered Chamber Using Platelet-Rich Plasma Without Cell Culture

Background: Clinically available cartilage, such as large-volume tissue-engineered cartilage, is urgently required for various clinical applications. Tissue engineering chamber (TEC) models are a promising organ-level strategy for efficient enlargement of cells or tissues within the chamber. The conventional TEC technology is not suitable for cartilage culture, because it lacks the necessary chondrogenic growth factor, which is present in platelet-rich plasma (PRP). In this study, we added autogenous auricular cartilage fragments mixed with PRP in a TEC to obtain a large amount of engineered cartilage. Experiment: To prove the efficacy of this method, 48 New Zealand white rabbits were randomly divided into 4 groups: PRP, vascularized (Ves), PRP, PRP+Ves, and control. Auricular cartilage was harvested from the rabbits, cut into fragments (2 mm), and then injected into TECs. Cartilage constructs were harvested at week 8, and construct volumes were measured. Histological morphology, immunochemical staining, and mechanical strength were evaluated. Results: At week 8, PRP+Ves constructs developed a white, cartilage-like appearance. The volume of cartilage increased by 600% the original volume from 0.30 to 1.8 ± 0.1789 mL. Histological staining showed proliferation of edge chondrocytes in the embedded cartilage in the PRP and PRP+Ves groups. Furthermore, the cartilage constructs in the PRP+Ves group show mechanical characteristics similar to those of normal cartilage. Conclusions: Auricular cartilage fragments mixed with PRP and vascularization of the TEC showed a significantly increased cartilage tissue volume after 8 weeks of incubation in rabbits. Impact Statement Repair of defects of ear cartilage tissue has always been a huge challenge to plastic surgeons. In this article, a new method is presented to produce within 8 weeks auricular cartilage in a tissue engineering chamber without cell culture. Having such a method is a valuable step toward creating a large volume of functional cartilage tissue, which may lead to successful construction of normal auricular structure with minimal donor-site morbidity.

Phenotypic redifferentiation of dedifferentiated microtia chondrocytes through a three-dimensional chondrogenic culture system

Chondrocytes from microtia patients are a valuable cell source for the tissue-engineering of auricles. However, dedifferentiation of microtia chondrocytes remains an obstacle for clinical translation. Strategies, such as three-dimensional (3D) culture systems, and the use of chondrogenic growth factors, have successfully induced redifferentiation of dedifferentiated chondrocytes from healthy individuals. However, it remains unknown whether these strategies are similarly effective for microtia patient-derived chondrocytes, which may carry genomic defects. To address this issue, dedifferentiated microtia chondrocytes (DMCs) were cultured in a 3D chondrogenic culture system for 4-8 weeks to investigate their redifferentiated properties and to generate redifferentiated microtia chondrocytes (RMCs). To predict the degree and course of redifferentiation, RMCs at different time points were harvested and examined for cell morphology, cell proliferation, type II collagen expression at passaging, and chondrogenic capacity. We show that a 3D chondrogenic culture system can effectively induce DMCs to become redifferentiated, functional chondrocytes, enabling them to regenerate mature cartilage. Furthermore, RMCs achieved their full original function after culture in the chondrogenic culture system for 6-8 weeks. Interestingly, redifferentiation of microtia chondrocytes exhibited a time-dependent trend. Although the primary mechanism by which the 3D chondrogenic culture system regulated the transition of DMCs into RMCs remains unknown, the current study provides deeper insight into microtia chondrocytes and promotes clinical translation of tissue-engineered auricles.

Noninvasive in vivo 3D bioprinting

Three-dimensional (3D) printing technology has great potential in advancing clinical medicine. Currently, the in vivo application strategies for 3D-printed macroscale products are limited to surgical implantation or in situ 3D printing at the exposed trauma, both requiring exposure of the application site. Here, we show a digital near-infrared (NIR) photopolymerization (DNP)–based 3D printing technology that enables the noninvasive in vivo 3D bioprinting of tissue constructs. In this technology, the NIR is modulated into customized pattern by a digital micromirror device, and dynamically projected for spatially inducing the polymerization of monomer solutions. By ex vivo irradiation with the patterned NIR, the subcutaneously injected bioink can be noninvasively printed into customized tissue constructs in situ. Without surgery implantation, a personalized ear-like tissue constructs with chondrification and a muscle tissue repairable cell-laden conformal scaffold were obtained in vivo. This work provides a proof of concept of noninvasive in vivo 3D bioprinting.

Bioprinting’s Introduction within the Context of the Convention on the Rights of Persons with Disabilities and Malaysia’s Persons with Disabilities Act 2008 through the Right to Science

Advances in bioprinting have enabled scientists to develop tissue and organs for the formation of artificial ears and noses, the treatment of injured joints because of arthritis, and the provision of medical care to people with disabilities. Malaysia’s disabled population can benefit from bioprinting because the United Nations Convention on the Rights of Persons with Disabilities (CRPD) and Malaysia’s Persons with Disabilities Act 2008 (PDA 2008) both include an indirect right to science expressed through the promotion of research and development (R&D), technology transfer, and new technologies. This qualitative study aims to identify relevant provisions within the CRPD and PDA 2008 that could support bioprinting research. This study utilises a multidisciplinary approach that combines biomedicine, law, and the social sciences. It analyses the travaux préparatoires of CRPD negotiations, the CRPD, the PDA 2008, and related documents for clues that negotiators once considered as the right to science. The results show that the travaux préparatoires of CRPD negotiations refer to biomedicine, while Article 4(1) (g)–(h) of the CRPD and Articles 9(1) (k) and 33(3) of the PDA 2008 refer to R&D, new technologies, and technology transfer, all of which indirectly imply the right to science and enable the introduction of bioprinting.

"Auricular reconstruction: A sociocultural, surgical and scientific perspective"

The functional and sociocultural role of the auricle has been prevalent in art, literature and history for millennia. It is no surprise, therefore, that auricular anomalies can be associated with affective disorders and impaired academic performance in children. The challenge of auricular reconstruction has captured the attention of surgical innovators for millennia with the earliest records of auricular reconstruction documented in the Edwin Smith Surgical Papyrus dating back to 3000 BCE. Since the 19th century, however, the interest in the ambition partial and total auricular reconstruction witnessed a rebirth, with refinements in frame construction, projection and skin coverage improving exponentially over the last two centuries. The gold standard auricular reconstruction practices today have their roots in these historical milestones, and form a solid foundation for the introduction of technological advancements such as 3D bioprinting and composite tissue allotransplantation into future auricular reconstruction practice. The aim of this review is to outline the sociocultural role of the auricle, the history and evolution of auricular reconstruction surgery and to provide an insight into potential future avenues of restoring auricular form and function.

A moldable thermosensitive hydroxypropyl chitin hydrogel for 3D cartilage regeneration in vitro and in vivo

Because of poor self-repair capacity, the repair of cartilage defect is always a great challenge in clinical treatment. In vitro cartilage regeneration provides a potential strategy for functional reconstruction of cartilage defect. Hydrogel has been known as an ideal cartilage regeneration scaffold. However, to date, in vitro cartilage regeneration based on hydrogel has not achieved satisfactory results. The current study explored the feasibility of in vitro 3D cartilage regeneration based on a moldable thermosensitive hydroxypropyl chitin (HPCH) hydrogel and its in vivo fate. The thermosensitive HPCH hydrogel was prepared and characterized. Goat auricular chondrocytes were encapsulated into the HPCH hydrogel to form a chondrocyte-hydrogel construct. The constructs were injected subcutaneously into nude mice or molded into different shapes for in vitro chondrogenic culture followed by in vivo implantation. The results demonstrated that the HPCH hydrogel possessed satisfactory gelation properties (gelation time < 18 s at 37 °C), biocompatibility (cell amount almost doubled within one week), and the ability to be applied as an injectable hydrogel for cartilage regeneration. All the constructs of in vitro culture basically maintained their original shapes (in vitro to initial: 110.8%) and displayed typical cartilaginous features with abundant lacunae and cartilage specific matrix deposition. These in vitro samples became more mature with prolonged in vivo implantation and largely maintained the original shape (in vivo to in vitro: 103.5%). These results suggested that the moldable thermosensitive HPCH hydrogel can serve as a promising scaffold for cartilage regeneration with defined shapes in vitro and in vivo. STATEMENT OF SIGNIFICANCE: Because of avascular and non-nervous characteristic of cartilage, in vitro regeneration plays an important role in reconstructing cartilage function. Hydrogel has been known as an ideal cartilage regeneration scaffold. However, to date, in vitro cartilage regeneration based on hydrogel has not achieved satisfactory results. The current study demonstrated that the chondrocyte-hydrogel construct generated by high density of chondrocytes encapsulated into a thermosensitive HPCH hydrogel could successfully regenerate in vitro typical cartilage-like tissue with defined shapes and further mature to form homogeneous cartilage with their original shapes after in vivo implantation. The current study indicated that the moldable thermosensitive HPCH hydrogel could serve as a promising scaffold for in vitro and in vivo cartilage regeneration with different shapes.

Advances in regenerative medicine for otolaryngology/head and neck surgery

Head and neck structures govern the vital functions of breathing and swallowing. Additionally, these structures facilitate our sense of self through vocal communication, hearing, facial animation, and physical appearance. Loss of these functions can lead to loss of life or greatly affect quality of life. Regenerative medicine is a rapidly developing field that aims to repair or replace damaged cells, tissues, and organs. Although the field is largely in its nascence, regenerative medicine holds promise for improving on conventional treatments for head and neck disorders or providing therapies where no current standard exists. This review presents milestones in the research of regenerative medicine in head and neck surgery.

Advancements in Soft-Tissue Prosthetics Part A: The Art of Imitating Life

Physical disfigurement due to congenital defects, trauma, or cancer causes considerable distress and physical impairment for millions of people worldwide; impacting their economic, psychological and social wellbeing. Since 3000 B.C., prosthetic devices have been used to address these issues by restoring both aesthetics and utility to those with disfigurement. Internationally, academic and industry researchers are constantly developing new materials and manufacturing techniques to provide higher quality and lower cost prostheses to those people who need them. New advanced technologies including 3D imaging, modeling, and printing are revolutionizing the way prostheses are now made. These new approaches are disrupting the traditional and manual art form of prosthetic production which are laborious and costly and are being replaced by more precise and quantitative processes which enable the rapid, low cost production of patient-specific prostheses. In this two part review, we provide a comprehensive report of past, present and emerging soft-tissue prosthetic materials and manufacturing techniques. In this review, part A, we examine, historically, the ideal properts of a polymeric material when applied in soft-tissue prosthetics. We also detail new research approaches to target specific tissues which commonly require aesthetic restoration (e.g. ear, nose and eyes) and discuss both traditional and advanced fabrication methods, from hand-crafted impression based approaches to advanced manufactured prosthetics. We discuss the chemistry and related details of most significant synthetic polymers used in soft-tissue prosthetics in Part B. As advanced manufacturing transitions from research into practice, the five millennia history of prosthetics enters a new age of economic, personalized, advanced soft tissue prosthetics and with this comes significantly improved quality of life for the people affected by tissue loss.

3D printing for tissue engineering in otolaryngology

Airway and other head and neck disorders affect hundreds of thousands of patients each year and most require surgical intervention. Among these, congenital deformity that affects newborns is particularly serious and can be life-threatening. In these cases, reconstructive surgery is resolutive but bears significant limitations, including the donor site morbidity and limited available tissue. In this context, tissue engineering represents a promising alternative approach for the surgical treatment of otolaryngologic disorders. In particular, 3D printing coupled with advanced imaging technologies offers the unique opportunity to reproduce the complex anatomy of native ear, nose, and throat, with its import in terms of functionality as well as aesthetics and the associated patient well-being. In this review, we provide a general overview of the main ear, nose and throat disorders and focus on the most recent scientific literature on 3D printing and bioprinting for their treatment.