Structural and Mechanical Comparison of Human Ear, Alar, and Septal Cartilage

Implanted cartilaginous grafts following rhinoplasty: A retrospective histopathological study

To describe histopathological features of rhinoplasty-related implanted cartilages, 83 cartilages surgically removed from 42 patients (2 men and 40 women) with a median age of 28.0 years (range, 21-47 years) following correction/revision rhinoplasty were examined. These cartilages included 16 autologous costal cartilages (ACCs), 14 irradiated homologous costal cartilages (IHCCs), 24 autologous nasal cartilages (ANCs), 2 irradiated homologous nasal cartilages (IHNCs), 14 autologous ear cartilages (ECs) and 13 combined cartilaginous grafts. The median chondrocytic viability in ACCs (35.9%) was higher than that of IHCCs (0.0%) and ECs (21.4%) (both, P<0.001), and showed no significant differences compared with the viability in ANCs (41.3%) (P=0.455). The median organized rate of chondroid matrix in ACCs, IHCCs, ANCs and ECs was 2.5, 1.4, 0.9 and 2.0%, respectively, and there were no significant differences among them (P=0.909). The present study revealed not only enlarged chondrocytic lacunae, chondrocytic cloning and binucleated/trinucleated chondrocytes, but also a possible transition between chondrocytes and fibroblasts in 6 ACCs, 3 ANCs and 1 EC, lipomembranous fat necrosis (LFN)-like bodies in 15 ACCs, 14 IHCCs, 3 ANCs and 5 ECs, and chondrocytic vacuolar changes in 15 ACCs, 22 ANCs, 2 IHNCs and 16 ECs. A histological transition between LFN-like bodies and chondrocytic vacuoles was focally observed in 2 ACCs and 1 ANC. The present findings suggested that the stability of implanted cartilage did not depend on chondrocytic viability only. Viable chondrocytes preserve implanted chondroid matrix, but also may, in part, induce organization through their transformation into fibroblasts. LFN-like bodies are considered to be an underrecognized form of vacuolar change-related chondrocytic necrosis.

Composite Thickness and Stiffness Analysis of the Nasal Septum

Background: The nasal septum supports the structure of the nose and is frequently manipulated during septorhinoplasty. Objective: To compare measurements of thickness and compressive Young's modulus (YM) between different regions of nasal septa from human anatomic specimens. Study Design: Case series. Methods: Cartilaginous septa from human anatomic specimens were dissected. Septum thickness was measured at 24 points with regular intervals using a digital caliper. Compressive YM was determined at 14 regions using a force gauge. Two-tailed student's t-tests were used to compare the average thickness and YM between different regions. Results: Septa from 40 human anatomic specimens were included, with age ranging from 50 to 89. Fifty percent of specimens were female. The mean (standard deviation) thickness of the septum was 1.75 (0.76) mm. The mean YM was 2.38 (1.29) MPa. The septum was thickest near the maxillary crest (3.09 [1.17] mm) and the keystone area (2.52 [0.91] mm) and thinnest near the anterior septal angle (1.29 [0.58] mm). The septum was most stiff posteriorly (2.90 [1.32] MPa) and least stiff anteriorly (1.80 [1.15] MPa). Conclusion: The nasal septum is thickest posteriorly, inferiorly, and along its bony edges. The septum is stiffest posteriorly, ventrally, and along its bony edges.

Differential Expression of Noncoding RNAs Revealed Enhancer RNA AC016735.2 as a Potential Pathogenic Marker of Congenital Microtia Patients

PURPOSE

Congenital microtia is a complex maxillofacial malformation with various risk factors. This study aimed to find potential pathogenic noncoding RNAs for congenital microtia patients.

METHODS

We collected 3 pairs of residual ear cartilage samples and corresponding normal ear cartilage samples from nonsyndromic congenital microtia patients for microarray experiments. The differentially expressed RNAs were screened, and enrichment analysis and correlation expression analysis were performed to elucidate the function of the differentially expressed genes (DEGs). We further investigated the most significantly differentially expressed long noncoding RNA (lncRNA), AC016735.2, through follow-up analyses including RT-qPCR and Western blotting, to validate its differential expression in residual ear cartilage compared with normal ear cartilage. SiRNA was designed to study the regulatory role of AC016735.2, and cell proliferation experiments were conducted to explore its impact on residual ear chondrocytes.

RESULTS

Analysis of the microarray data revealed a total of 1079 differentially expressed RNAs, including 305 mRNAs and x lncRNAs, using a threshold of FC>1.5 and P<0.05 for mRNA, and FC>1.0 and P<0.05 for lncRNA. Enrichment analysis indicated that these genes are mainly involved in extracellular matrix regulation and embryonic development. AC016735.2 showed the highest differential expression among the eRNAs, being upregulated in residual ear cartilage. It acts in cis to regulate the nearby coding gene ZFP36L2, indirectly affecting downstream genes such as BMP4, TWSG1, COL2A1, and COL9A2.

CONCLUSION

Significant differences were observed in the expression of lncRNAs and mRNAs between residual ear cartilage and normal auricular cartilage tissues in the same genetic background of congenital microtia. These differentially expressed lncRNAs and mRNAs may play crucial roles in the occurrence and development of microtia through pathways associated with extracellular matrix regulation and gastrulation. Particularly, AC016735.2, an eRNA acting in cis, could serve as a potential pathogenic noncoding gene.

Second Harmonic Imaging of Nasal, Auricular, and Costal Cartilage

OBJECTIVE

There is little knowledge about the histological organization of facial and costal cartilages in terms of matrix structure and cell morphology. Second harmonic generation (SHG) imaging is a nonlinear imaging technique that capitalizes on signal generation from highly ordered macromolecules such as collagen fibers. The purpose of this study was to use SHG microscopy to image collagen extracellular matrix (ECM) structure, chondrocyte size, and density of these cartilages.

STUDY DESIGN

Experimental.

METHODS

Surgical remnants of septal, lower lateral, rib, and auricular cartilages were collected following surgery, sectioned into 0.5-1 mm thick samples and fixed to facilitate batch process imaging. A Leica TCS SP8 MP Microscope and multiphoton laser were used to image the specimens. Images were analyzed for cell size, cell density, and collagen fiber directionality patterns using ImageJ.

RESULTS

SHG images of septal specimens show mesh-like structure of the ECM. There appears to be a superficial layer, characterized by flattened lacunae and middle zone, marked by circular lacunae clusters, similar to what is observed in articular cartilage. The structure of the ECM depicts a visible orientation perpendicular to the surface of the perichondrium. Cell size and density analysis through ImageJ suggests variety across cartilage types. Directionality analysis indicates that the collagen in the ECM displays preferred direction.

CONCLUSION

This study establishes clear extracellular models of facial and costal cartilages. Limitations include heterogeneous cartilage thickness due to processing difficulties. Further studies include automating the cutting process to increase uniformity of tissue thickness and increasing sample size to further validate results.

LEVEL OF EVIDENCE

2 Laryngoscope, 133:3370-3377, 2023.

Combining bioengineered human skin with bioprinted cartilage for ear reconstruction

Microtia is a congenital disorder that manifests as a malformation of the external ear leading to psychosocial problems in affected children. Here, we present a tissue-engineered treatment approach based on a bioprinted autologous auricular cartilage construct (EarCartilage) combined with a bioengineered human pigmented and prevascularized dermo-epidermal skin substitute (EarSkin) tested in immunocompromised rats. We confirmed that human-engineered blood capillaries of EarSkin connected to the recipient's vasculature within 1 week, enabling rapid blood perfusion and epidermal maturation. Bioengineered EarSkin displayed a stratified epidermis containing mature keratinocytes and melanocytes. The latter resided within the basal layer of the epidermis and efficiently restored the skin color. Further, in vivo tests demonstrated favorable mechanical stability of EarCartilage along with enhanced extracellular matrix deposition. In conclusion, EarCartilage combined with EarSkin represents a novel approach for the treatment of microtia with the potential to circumvent existing limitations and improve the aesthetic outcome of microtia reconstruction.

Human nasal cartilage: Functional properties and structure-function relationships for the development of tissue engineering design criteria

Nose reconstruction often requires scarce cartilage grafts. Nasal cartilage properties must be determined to serve as design criteria for engineering grafts. Thus, mechanical and biochemical properties were obtained in multiple locations of human nasal septum, upper lateral cartilage (ULC), and lower lateral cartilage (LLC). Within each region, no statistical differences among locations were detected, but anisotropy at some septum locations was noted. In the LLC, the tensile modulus and ultimate tensile strength (UTS) in the inferior-superior direction were statistically greater than in the anterior-posterior direction. Cartilage from all regions exhibited hyperelasticity in tension, but regions varied in degree of hyalinicity (i.e., Col II:Col I ratio). The septum contained the most collagen II and least collagen I and III, making it more hyaline than the ULC and LLC. The septum had a greater aggregate modulus, UTS, and lower total collagen/wet weight (Col/WW) than the ULC and LLC. The ULC had greater tensile modulus, DNA/WW, and lower glycosaminoglycan/WW than the septum and LLC. The ULC had a greater pyridinoline/Col than the septum. Histological staining suggested the presence of chondrons in all regions. In the ULC and LLC, tensile modulus correlated with total collagen content, while aggregate modulus correlated with pyridinoline content and weakly with pentosidine content. However, future studies should be performed to validate these proposed structure-function relationships. This study of human nasal cartilage provides 1) crucial design criteria for nasal cartilage tissue engineering efforts, 2) quantification of major and minor collagen subtypes and crosslinks, and 3) structure-function relationships. Surprisingly, the large mechanical properties found, particularly in the septum, suggests that nasal cartilage may experience higher-than-expected mechanical loads. STATEMENT OF SIGNIFICANCE: While tissue engineering holds promise to generate much-needed cartilage grafts for nasal reconstruction, little is known about nasal cartilage from an engineering perspective. In this study, the mechanical and biochemical properties of the septum, upper lateral cartilage (ULC), and lower lateral cartilage (LLC) were evaluated using cartilage-specific methods. For the first time in this tissue, all major and minor collagens and collagen crosslinks were measured, demonstrating that the septum was more hyaline than the ULC and LLC. Additionally, new structure-function relationships in the ULC and LLC were identified. This study greatly expands upon the quantitative understanding of human nasal cartilage and provides crucial engineering design criteria for much-needed nasal cartilage tissue engineering efforts.

A Novel Ear Cartilage Caudal Septal Extension Graft

In cases of weak or deficient caudal septum, the caudal septum extension graft (CSEG) is the most commonly used reconstructive method. In the current study we introduce a newly-designed conchal cartilage CSEG and evaluate its cosmetic and functional outcomes. The graft has an average length of 3 ± 0.3 cm and composed of a distal double-layered part, which is 3 to 4 mm wide and a proximal single-layered part, which is 1.2 to 1.7 cm wide. The graft design allows the proximal single-layered part to be fixed on either sides of the caudal septum while keeping the distal double-layered segment in the midline. The study included 230 patients, of which 83% were revisions, all patients completed a validated patient-reported outcome measure (PROM) questionnaire pre- and postoperatively. The PROMs used were either the Nasal Obstruction Symptom Evaluation (NOSE) survey or the Standardized Cosmesis and Health Nasal Outcomes Survey (SCHNOS). During the mean follow-up period of 18.2 months (range: 9-192 months) no serious complications were encountered and only six cases (2.3%) required minor revisions of the CSEG.Using the proposed conchal cartilage, CSEG resulted in an improved cosmetic and functional outcome as evidenced by the significant postoperative improvement in the NOSE, SCHNOS-O, and SCHNOS-C scores with a p-value <0.001, <0.05, and <0.0001, respectively. The graft provided adequate tensile strength and support to the nasal tip, which resulted in improved tip projection, rotation, definition, and symmetry, while maintaining a degree of flexibility and elasticity which is much more than that of the rib or even the septum thus resulting in the most natural feel of the nasal tip lobule.

Regeneration of Rabbit Auricular Cartilage After the Intravenous Stem Cell Injection

Background

The restoration of auricular cartilage is a major problem of otolaryngology. The low regenerative capacity of cartilage requires alternative approaches such as cell and tissue engineering. Stem cells are one of the ways to repair auricular cartilage damages. The aim of the investigation was the regeneration of an artificial defect of the auricular cartilage of rabbits after the intravenous injection of stem cells.

Materials and Methods

The study was carried out on rabbits. A narrow strip of auricular cartilage was surgically removed. A previously prepared suspension of homologous mesenchymal stem cells (5 million) in 0.5 ml physiological solution was injected into the vein of the opposite ear. Tissue samples from the site of the injury were collected after 1, 2, and 3 months. Histological examinations of the tissues were carried out after staining with fuchsin-eosin, azure II-eosin, and according to Weigert. In addition, the amount of interleukin-6 (IL-6) and the transforming growth factor β1 (TGF-β1) in the blood serum were determined.

Results

The main method of healing is the formation of a connective tissue scar. Yret, an increase of the number of fibroblasts and single islands of the newly formed auricular cartilage was found, which indicates the migration of the injected stem cells to the site of the damage and settling there. The intravenous injection of stem cells did not affect the secretion of pro-inflammatory IL-6, but significantly increased the amount of TGF-β1.

Conclusions

We assume that regenerative processes were stimulated. Nevertheless, they were aimed at quickly restoring the tissue integrity through the typical stages of scar formation. The restoration of cartilage integrity requires additional regulatory factors which will determine the chondrogenic differentiation of stem cells.

Genome-wide association study reveals that the IBSP locus affects ear size in cattle

Ear size is a classical model for hot climate adaptation following the evolution, but the genetic basis of the traits associated with ear size remains to be elucidated. Here, we performed a genome-wide association study on 158 cattle to explain the genetic mechanism of ear size. One region on BTA6 between 36.79 and 38.80 Mb included 50 suggestive SNPs and 4 significant SNPs that were significantly associated with ear size. The most significant locus (P = 1.30 × 10-8) was a missense mutation (T250I) on the seventh exon of integrin-binding sialoprotein (IBSP), which had an allele substitution effect of 23.46 cm2 for ear size. Furthermore, this mutation will cause changes in the three-dimensional structure of the protein. To further identify genes underlying this typical feature, we performed a genome scan among nine cattle breeds with different ear sizes by using SweeD. Results suggested that IBSP was under positive selection among four breeds with relatively large ear sizes. The expression levels of IBSP in ear tissues of large- and small-ear cattle were significantly different. A haplotype diversity survey of this missense mutation in worldwide cattle breeds strongly implied that the origin of this missense mutation event was Bos taurus. These findings have important theoretical importance for the exploration of major genes associated with ear size and provide important molecular markers for the identification of cattle germplasm resources.

Investigation on Filaments for 3D Printing of Nasal Septum Cartilage Implant

Septoplasty is a widely used method in treating deviated septum. Although it is successfully implemented, there are problems with excessive bleeding, septal perforation, or infections. The use of anatomically shaped implants could help overcome these problems. This paper focuses on assessing the possibility of the usage of a nasal septum cartilage implant 3D printed from various market-available filaments. Five different types of laments were used, two of which claim to be suitable for medical use. A combination of modeling, mechanical (bending, compression), structural (FTIR), thermal (DSC, MFR), surface (contact angle), microscopic (optical), degradation (2 M HCl, 5 M NaOH, and 0.01 M PBS), printability, and cell viability (MTT) analyses allowed us to assess the suitability of materials for manufacturing implants. Bioflex had the most applicable properties among the tested materials, but despite the overall good performance, cell viability studies showed toxicity of the material in MTT test. The results of the study show that selected filaments were not suitable for nasal cartilage implants. The poor cell viability of Bioflex could be improved by surface modification. Further research on biocompatible elastic materials for 3D printing is needed either by the synthesis of new materials or by modifying existing ones.

A novel device for investigating structure-function relationships and mechanoadaptation of biological tissues

Exploring the structure-function relationships of cartilage on a microstructural level is crucial for tissue engineering approaches aiming to restore function. Therefore, a combination of mechanical testing with cell and tissue-level imaging would allow for longitudinal studying loading mechanisms, biological responses and mechanoadaptation of tissues at a microstructural level. This paper describes the design and validation of FELIX, a custom-built device for non-destructive image-guided micromechanical evaluation of biological tissues and tissue-engineered constructs. It combines multiphoton microscopy with non-destructive mechanical testing of native soft tissues. Ten silicone samples of the same size were mechanically tested with FELIX by different users to assess the repeatability and reproducibility. The results indicate that FELIX can successfully substitute mechanical testing protocols with a commercial device without compromising precision. Furthermore, FELIX demonstrated consistent results across repeated measurements, with very small deviations. Therefore, FELIX can be used to accurately measure biomechanical properties by different users for separate studies. Additionally, cell nuclei and collagen of porcine articular cartilage were successfully imaged under compression. Cell viability remained high in chondrocytes cultured in agarose over 21 days. Furthermore, there were no signs of contamination indicating a cell friendly, sterile environment for longitudinal studies. In conclusion, this work demonstrates that FELIX can consistently quantify mechanical measures without compromising precision. Furthermore, it is biocompatible allowing for longitudinal measurements.

Mechanical Properties and Functions of Elastin: An Overview

Human tissues must be elastic, much like other materials that work under continuous loads without losing functionality. The elasticity of tissues is provided by elastin, a unique protein of the extracellular matrix (ECM) of mammals. Its function is to endow soft tissues with low stiffness, high and fully reversible extensibility, and efficient elastic-energy storage. Depending on the mechanical functions, the amount and distribution of elastin-rich elastic fibers vary between and within tissues and organs. The article presents a concise overview of the mechanical properties of elastin and its role in the elasticity of soft tissues. Both the occurrence of elastin and the relationship between its spatial arrangement and mechanical functions in a given tissue or organ are overviewed. As elastin in tissues occurs only in the form of elastic fibers, the current state of knowledge about their mechanical characteristics, as well as certain aspects of degradation of these fibers and their mechanical performance, is presented. The overview also outlines the latest understanding of the molecular basis of unique physical characteristics of elastin and, in particular, the origin of the driving force of elastic recoil after stretching.

Genetically engineered chondrocytes overexpressing elastin improve cell retention and chondrogenesis in a three-dimensional GelMA culture system

Elastic cartilage possesses many elastic fibers and has a high degree of elasticity. However, insufficient elastic fiber production remains unsolved in elastic cartilage tissue engineering. Exogenous elastin is difficult to degrade and violates cell proliferation and migration during cartilage regeneration. Moreover, exogenous elastic fibers are difficult to assemble with endogenous extracellular matrix components. We produced genetically engineered chondrocytes overexpressing elastin to boost endogenous elastic fiber production. After identifying that genetic manipulation hardly impacted the cell viability and chondrogenesis of chondrocytes, we co-cultured genetically engineered chondrocytes with untreated chondrocytes in a three-dimensional gelatin methacryloyl (GelMA) system. In vitro study showed that the co-culture system produced more elastic fibers and increased cell retention, resulting in strengthened mechanics than the control system with untreated chondrocytes. Moreover, in vivo implantation revealed that the co-culture GelMA system greatly resisted host tissue invasion by promoting elastic fiber production and cartilage tissue regeneration compared with the control system. In summary, our study indicated that genetically engineered chondrocytes overexpressing elastin are efficient and safe for promoting elastic fiber production and cartilage regeneration in elastic cartilage tissue engineering.

What Is the Best Candidate to Replace the Tarsus? A Biomechanical, Histological, and Optical Study Comparing Five Grafts

Purpose

Reconstruction of the posterior lamella after eyelid tumor removal is challenging and not consensual. Tarsus is the most suitable graft, but is only available in small amounts. Herein, we aim to determine the most appropriate way to replace the tarsus by comparing the biomechanical, histological, and optical properties of five commonly used grafts.

Methods

This study was conducted at the University hospital of Nice between June 2019 and June 2020. Five posterior lamella grafts (tarsus, conchal cartilage, sclera, hard palate, and dermis) were harvested in five fresh frozen cadavers. Biomechanical properties were assessed by tractometry. Collagen and elastin fibers were analyzed by using histological analysis and optical characterization with the second harmonic generation imaging.

Results

The mean Young's modulus was 8.92 MPa (range, 2.90-22.90 MPa), 1.05 MPa (range, 0.39-1.76 MPa), 8.72 MPa (range, 2.0-23.50 MPa), 2.57 MPa (range, 0.41-4.35 MPa), and 1.44 MPa (range, 0.71-2.30 MPa) for the tarsus, the conchal cartilage, the sclera, the hard palate mucosa, and the dermis, respectively. The mean tensile strength was 3 MPa (range, 1.70-6.88 MPa), 0.54 MPa (range, 0.13-0.79 MPa), 2.87 MPa (range, 1.23-5.40 MPa), 1.4 MPa (range, 0.21-2.40 MPa) and 1.0 MPa (range, 0.46-1.43 MPa) for the tarsus, the conchal cartilage, the sclera, the hard palate mucosa, and the dermis, respectively. Hard palate mucosa was the closest to the tarsus regarding the ratio of elastin and collagen fibers. The average second harmonic generation intensity was 221 arbitrary units (a.u.) (range, 165-362 a.u.), 182 a.u. (range, 35-259 a.u.), 369 a.u. (range, 206-533 a.u.), 108 a.u. (range, 34-208 a.u.), and 244 a.u. (range, 195-388 a.u.) for the tarsus, the conchal cartilage, the sclera, the hard palate mucosa, and the dermis, respectively. The hard palate mucosa and the dermis were the closest to the tarsus regarding the collagen fiber size and orientation, respectively.

Conclusions

By attributing 2 points for each characteristic (biomechanical, histological, and optical), the hard palate mucosa and the sclera seem to be the most suitable grafts to replace the tarsus.

Translational Relevance

The aim of this article was to assess the biomechanical, histological and optical characteristics of five of the most commonly used tarsal grafts; this may be helpful in decisions for clinical practice.

Non-Mulberry Silk Fiber-Based Composite Scaffolds Containing Millichannels for Auricular Cartilage Regeneration

Tissue engineering has made significant progress as a cartilage repair alternative. It is crucial to promote cell proliferation and migration within three-dimensional (3D) bulk scaffolds for tissue regeneration through either chemical gradients or physical channels. In this study, by developing optimized silk fiber-based composite scaffolds, millimeter-scaled channels were created in the corresponding scaffolds via facile physical percussive drilling and subsequently utilized for auricular cartilage regeneration. We found that by the introduction of poly-l-lactic acid porous microspheres (PLLA PMs), the channels incorporated into the Antheraea pernyi (Ap) silk fiber-based scaffolds were reinforced, and the mechanical features were well maintained. Moreover, Ap silk fiber-based scaffolds reinforced by PLLA PMs containing channels (CMAF) exhibited excellent chondrocyte proliferation, migration, and synthesis of cartilage-specific extracellular matrix (ECM) in vitro. The biological evaluation in vivo revealed that CMAF had a higher chondrogenic capability for an even deposition of the specific ECM component. This study suggested that multihierarchical CMAF may have potential application for auricular cartilage regeneration.

Off-the-Shelf Nipple Engineering: Neonipple Formation via Implantation of Scaffolded Decellularized Ovine Xenograft

BACKGROUND

Nipple reconstruction is widely regarded as the final step in postmastectomy breast reconstruction. While grafts, local flaps, or combination approaches have been used in nipple reconstruction, none has been able to achieve reliable long-term projection preservation. In response, we have sought to bioengineer neonipples in situ via the implantation of processed, decellularized cartilage xenografts placed within 3-dimensional-printed polylactic acid (PLA) scaffolds.

MATERIALS AND METHODS

External nipple scaffolds were designed in-house and 3-dimensional-printed with PLA filament. Decellularized ovine xenograft infill was prepared and processed by mincing or zesting. All nipple scaffolds were placed subcutaneously on the dorsa of Sprague-Dawley rats and explanted after 1, 3, and 6 months for analysis.

RESULTS

Explanted nipple scaffolds demonstrated gross maintenance of scaffold shape, diameter, and projection with accompanying increases in tissue volume. Histologic analyses revealed preservation of native cartilage architecture after 6 months without evidence of degradation. Analysis of formed tissue within the scaffolds revealed a progressive invasion of fibrovascular tissue with identifiable vascular channels and adipose tissue after 6 months in vivo. Confined compression testing revealed equilibrium moduli of both minced and zested samples that were within the expected range of previously reported human nipple tissue, while these data revealed no differences in the mechanical properties of the neotissue between time points or processing techniques.

CONCLUSIONS

These preliminary data support potential use of decellularized allograft to foster healthy tissue ingrowth within a PLA scaffold, thereby offering a novel solution to current limitations in nipple reconstruction.

Comparison of Surgical Outcomes Between Ossicle-Cartilage Composite Graft and Synthetic Ossicular Prosthesis for Ossicular Reconstruction

OBJECTIVE

To propose a modified technique of ossiculoplasty using an ossicle-cartilage composite graft (OCCG) and compare its hearing outcome and protrusion rate with those of a synthetic prosthesis.

METHODS

Autologous tragal or homologous septal cartilage was combined with an ossicle to create an umbrella shape OCCG. A total of 302 ossiculoplasty surgeries performed in a single university hospital between 1997 and 2006 were retrospectively reviewed based on the prosthesis type-OCCG or polymaleinate ionomeric prosthesis (IONOS®). Data includes demographic profiles, audiometric outcomes, intraoperative findings, and post-operative complications and was categorized by the follow-up periods.

RESULTS

Ossicle-cartilage composite graft was used for 175 patients and IONOS® for 127 patients. The mean post-operative air-bone gap (ABG) of the OCCG group was 22.36 dB, which was better than the IONOS® group of 25.08 dB (P = .015). The successful ABG closure rate of less than 20 dB was also higher in the OCCG group compared to the IONOS® group (38.3% vs 26.8%, P = .036). The ABG between the pre- and post-operative conditions exhibited a significant difference between the 2 groups (P = .006). In the data divided into 3 groups according to the follow-up period, the OCCG group showed a better outcome in the long-term follow-up with 0 cases of protrusion during the follow-up period in the OCCG group compared to 8 cases of the IONOS® group (P = .018).

CONCLUSION

Ossiculoplasty with OCCG exhibited satisfactory audiometric outcomes and low complication rates. Ossicle-cartilage composite graft can be a good option with sufficient informed consent and preliminary screening of transmitted diseases.

Progress of 3D Printing Techniques for Nasal Cartilage Regeneration

Once cartilage is damaged, its self-repair capacity is very limited. The strategy of tissue engineering has brought a new idea for repairing cartilage defect and cartilage regeneration. In particular, nasal cartilage regeneration is a challenge because of the steady increase in nasal reconstruction after oncologic resection, trauma, or rhinoplasty. From this perspective, three-dimensional (3D) printing has emerged as a promising technology to address the complexity of nasal cartilage regeneration, using patient's image data and computer-aided deposition of cells and biomaterials to precisely fabricate complex, personalized tissue-engineered constructs. In this review, we summarized the major progress of three prevalent 3D printing approaches, including inkjet-based printing, extrusion-based printing and laser-assisted printing. Examples are highlighted to illustrate 3D printing for nasal cartilage regeneration, with special focus on the selection of seeded cell, scaffolds and growth factors. The purpose of this paper is to systematically review recent research about the challenges and progress and look forward to the future of 3D printing techniques for nasal cartilage regeneration.Level of Evidence III This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com/00266 .

Bioprinting of Chondrocyte Stem Cell Co-Cultures for Auricular Cartilage Regeneration

Advances in 3D bioprinting allows not only controlled deposition of cells or cell-laden hydrogels but also flexibility in creating constructs that match the anatomical features of the patient. This is especially the case for reconstructing the pinna (ear), which is a large feature of the face and made from elastic cartilage that primarily relies on diffusion for nutrient transfer. The selection of cell lines for reconstructing this cartilage becomes a crucial step in clinical translation. Chondrocytes and mesenchymal stem cells are both studied extensively in the area of cartilage regeneration as they are capable of producing cartilage in vitro. However, such monoculture systems involve unfavorable processes and produce cartilage with suboptimal characteristics. Co-cultures of these cell types are known to alleviate these limitations to produce synergically active chondrocytes and cartilage. The current study utilized a 3D bioprinted scaffold made from combined gelatine methacryloyl and methacrylated hyaluronic acid (GelMA/HAMA) to interrogate monocultures and co-cultures of human septal chondrocytes (primary chondrocytes, PCs) and human bone marrow-derived mesenchymal stem cells (BM-hMSCs). This study is also the first to examine co-cultures of healthy human chondrocytes with human BM-hMSCs encapsulated in GelMA/HAMA bioprinted scaffolds. Findings revealed that the combination of MSCs and PCs not only yielded cell proliferation that mimicked MSCs but also produced chondrogenic expressions that mimicked PCs. These findings suggested that co-cultures of BM-hMSCs and healthy septal PCs can be employed to replace monocultures in chondrogenic studies for cartilage regeneration in this model. The opportunity for MSCs used to replace PCs alleviates the requirement of large cartilage biopsies that would otherwise be needed for sufficient cell numbers and therefore can be employed for clinical applications.

Multiscale Strain Transfer in Cartilage

The transfer of stress and strain signals between the extracellular matrix (ECM) and cells is crucial for biochemical and biomechanical cues that are required for tissue morphogenesis, differentiation, growth, and homeostasis. In cartilage tissue, the heterogeneity in spatial variation of ECM molecules leads to a depth-dependent non-uniform strain transfer and alters the magnitude of forces sensed by cells in articular and fibrocartilage, influencing chondrocyte metabolism and biochemical response. It is not fully established how these nonuniform forces ultimately influence cartilage health, maintenance, and integrity. To comprehend tissue remodelling in health and disease, it is fundamental to investigate how these forces, the ECM, and cells interrelate. However, not much is known about the relationship between applied mechanical stimulus and resulting spatial variations in magnitude and sense of mechanical stimuli within the chondrocyte’s microenvironment. Investigating multiscale strain transfer and hierarchical structure-function relationships in cartilage is key to unravelling how cells receive signals and how they are transformed into biosynthetic responses. Therefore, this article first reviews different cartilage types and chondrocyte mechanosensing. Following this, multiscale strain transfer through cartilage tissue and the involvement of individual ECM components are discussed. Finally, insights to further understand multiscale strain transfer in cartilage are outlined.

Properties of the Nasal Cartilage, from Development to Adulthood: A Scoping Review

OBJECTIVE

Nasal septum cartilage is a hyaline cartilage that provides structural support to the nasal cavity and midface. Currently, information on its cellular and mechanical properties is widely dispersed and has often been inferred from studies conducted on other cartilage types such as the knee. A detailed understanding of nasal cartilage properties is important for several biological, clinical, and engineering disciplines. The objectives of this scoping review are to (1) consolidate actual existing knowledge on nasal cartilage properties and (2) identify gaps of knowledge and research questions requiring future investigations.

DESIGN

This scoping review incorporated articles identified using PROSPERO, Cochrane Library (CDSR and Central), WOS BIOSIS, WOS Core Collection, and ProQuest Dissertations and Theses Global databases. Following the screening process, 86 articles were considered. Articles were categorized into three groups: growth, extracellular matrix, and mechanical properties.

RESULTS

Most articles investigated growth properties followed by extracellular matrix and mechanical properties. NSC cartilage is not uniform. Nasal cartilage growth varies with age and location. Similarly, extracellular matrix composition and mechanical properties are location-specific within the NSC. Moreover, most articles included in the review investigate these properties in isolation and only very few articles demonstrate the interrelationship between multiple cartilage properties.

CONCLUSIONS

This scoping review presents a first comprehensive description of research on NSC properties with a focus on NSC growth, extracellular matrix and mechanical properties. It additionally identifies the needs (1) to understand how these various cartilage properties intersect and (2) for more granular, standardized assessment protocols to describe NSC.

Advanced Hydrogels for Cartilage Tissue Engineering: Recent Progress and Future Directions

Cartilage is a tension- and load-bearing tissue and has a limited capacity for intrinsic self-healing. While microfracture and arthroplasty are the conventional methods for cartilage repair, these methods are unable to completely heal the damaged tissue. The need to overcome the restrictions of these therapies for cartilage regeneration has expanded the field of cartilage tissue engineering (CTE), in which novel engineering and biological approaches are introduced to accelerate the development of new biomimetic cartilage to replace the injured tissue. Until now, a wide range of hydrogels and cell sources have been employed for CTE to either recapitulate microenvironmental cues during a new tissue growth or to compel the recovery of cartilaginous structures via manipulating biochemical and biomechanical properties of the original tissue. Towards modifying current cartilage treatments, advanced hydrogels have been designed and synthesized in recent years to improve network crosslinking and self-recovery of implanted scaffolds after damage in vivo. This review focused on the recent advances in CTE, especially self-healing hydrogels. The article firstly presents the cartilage tissue, its defects, and treatments. Subsequently, introduces CTE and summarizes the polymeric hydrogels and their advances. Furthermore, characterizations, the advantages, and disadvantages of advanced hydrogels such as multi-materials, IPNs, nanomaterials, and supramolecular are discussed. Afterward, the self-healing hydrogels in CTE, mechanisms, and the physical and chemical methods for the synthesis of such hydrogels for improving the reformation of CTE are introduced. The article then briefly describes the fabrication methods in CTE. Finally, this review presents a conclusion of prevalent challenges and future outlooks for self-healing hydrogels in CTE applications.

Bioprinting of Collagen Type I and II via Aerosol Jet Printing for the Replication of Dense Collagenous Tissues

Collagen has grown increasingly present in bioprinting, however collagen bioprinting has mostly been limited to the extrusion printing of collagen type I to form weak collagen hydrogels. While these weak collagen hydrogels have their applications, synthetic polymers are often required to reinforce gel-laden constructs that aim to replicate dense collagenous tissues found in vivo. In this study, aerosol jet printing (AJP) was used to print and process collagen type I and II into dense constructs with a greater capacity to replicate the dense collagenous ECM found in connective tissues. Collagen type I and II was isolated from animal tissues to form solutions for printing. Collagen type I and II constructs were printed with 576 layers and measured to have average effective elastic moduli of 241.3 ± 94.3 and 196.6 ± 86.0 kPa (±SD), respectively, without any chemical modification. Collagen type II solutions were measured to be less viscous than type I and both collagen type I and II exhibited a drop in viscosity due to AJP. Circular dichroism and SDS-PAGE showed collagen type I to be more vulnerable to structural changes due to the stresses of the aerosol formation step of aerosol jet printing while the collagen type II triple helix was largely unaffected. SEM illustrated that distinct layers remained in the aerosol jet print constructs. The results show that aerosol jet printing should be considered an effective way to process collagen type I and II into stiff dense constructs with suitable mechanical properties for the replication of dense collagenous connective tissues.

Enhanced cellular migration and prolonged chondrogenic differentiation in decellularized cartilage scaffolds under dynamic culture conditions

Lesions of aural, nasal and tracheal cartilage are frequently reconstructed by complex surgeries which are based on harvesting autologous cartilage from other locations such as the rib. Cartilage tissue engineering (CTE) is regarded as a promising alternative to attain vital cartilage. Nevertheless, CTE with nearly natural properties poses a significant challenge to research due to the complex reciprocal interactions between cells and extracellular matrix which have to be imitated and which are still not fully understood. Thus, we used a custom-made glass bioreactor to enhance cell migration into decellularized porcine cartilage scaffolds (DECM) and mimic physiological conditions. The DECM seeded with human nasal chondrocytes (HPCH) were cultured in the glass reactor for 6 weeks and examined by histological and immunohistochemical staining, biochemical analyses and real time-PCR at 14, 28 and 42 days. The migration depth and the number of migrated cells were quantified by computational analysis. Compared to the static cultivation, the dynamic culture (DC) fostered migration of HPCH into deeper tissue layers. Furthermore, cultivation in the bioreactor enhanced differentiation of the cells during the first 14 days, but differentiation diminished in the course of further cultivation. We consider the DC in the presented bioreactor as a promising tool to facilitate CTE and to help to better understand the complex physiological processes during cartilage regeneration. Maintaining differentiation of chondrocytes and improving cellular migration by further optimizing culture conditions is an important prerequisite for future clinical application.

Evaluation of facial tissue stresses under medical devices post application of a cyanoacrylate liquid skin protectant: An integrated experimental-computational study

Medical device‐related pressure ulcers (PUs) (injuries) are a subclass of PUs, associated with pressure and/or shear applied by a medical device onto the skin. Clinical application of a cyanoacrylate liquid skin protectant (CLSP) under the contours of skin‐contacting medical devices to shield an intact skin from the sustained mechanical loads that are applied by medical devices is a preventative option, but no computer modelling work has been reported to assess the biomechanical efficacy of such interventions. Here, we investigated the biomechanical protective effect of a polymerised cyanoacrylate coating using three‐dimensional, anatomically realistic finite element models of the ear with oxygen cannula and the mouth with endotracheal attachment device, informed by experimental studies. We have compared tissue stress exposures under the devices at these facial sites between conditions where the cyanoacrylate skin protectant has been applied or where the device was contacting the skin directly, without the shielding of the cyanoacrylate coating. The CLSP considerably reduced the skin stress concentration levels and overall tissue stress exposures under the aforementioned medical devices. This demonstrates strong biomechanical effectiveness of the studied cyanoacrylate‐based skin protectant in prevention of facial medical device‐related injuries at small, curved and thereby difficult to protect facial sites.

Non-mulberry silk fiber-based scaffolds reinforced by PLLA porous microspheres for auricular cartilage: An in vitro study

Designing clinical applicable polymeric composite scaffolds for auricular cartilage tissue engineering requires appropriate mechanical strength and biological characteristics. In this study, silk fiber-based scaffolds co-reinforced with poly-L-lactic acid porous microspheres (PLLA PMs) combined with either Bombyx mori (Bm) or Antheraea pernyi (Ap) silk fibers were fabricated as inspired by the "steel bars reinforced concrete" structure in architecture and their chondrogenic functions were also investigated. We found that the Ap silk fiber-based scaffolds reinforced by PLLA PMs (MAF) exhibited superior physical properties (the mechanical properties in particular) as compared to the Bm silk fiber-based scaffolds reinforced by PLLA PMs (MBF). Furthermore, in vitro evaluation of chondrogenic potential showed that the MAF provided better cell adhesion, viability, proliferation and GAG secretion than the MBF. Therefore, the MAF are promising in auricular cartilage tissue engineering and relevant plastic surgery-related applications.

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.

The Challenge of Cartilage Integration: Understanding a Major Barrier to Chondral Repair

Articular cartilage defects caused by injury frequently lead to osteoarthritis, a painful and costly disease. Despite widely used surgical methods to treat articular cartilage defects and a plethora of research into regenerative strategies as treatments, long-term clinical outcomes are not satisfactory. Failure to integrate repair tissue with native cartilage is a recurring issue in surgical and tissue-engineered strategies, seeing eventual degradation of the regenerated or surrounding tissue. This review delves into the current understanding of why continuous and robust integration with native cartilage is so difficult to achieve. Both the intrinsic limitations of chondrocytes to remodel injured cartilage, and the significant challenges posed by a compromised biomechanical environment are described. Recent scaffold and cell-based techniques to repair cartilage are also discussed, and limitations of existing methods to evaluate integrative repair. In particular, the importance of evaluating the mechanical integrity of the interface between native and repair tissue is highlighted as a meaningful assessment of any strategy to repair this load-bearing tissue. Impact statement The failure to integrate grafts or biomaterials with native cartilage is a major barrier to cartilage repair. An in-depth understanding of the reasons cartilage integration remains a challenge is required to inform cartilage repair strategies. In particular, this review highlights that integration of cartilage repair strategies is frequently assessed in terms of the continuity of tissue, but not the mechanical integrity. Given the load-bearing nature of cartilage, evaluating integration in terms of interfacial strength is essential to assessing the potential success of cartilage repair methods.

Will Tissue-Engineering Strategies Bring New Hope for the Reconstruction of Nasal Septal Cartilage?

The nasal septal cartilage plays an important role in the growth of midface and as a vertical strut preventing the collapse of the nasal bones. The repair of nasal cartilage defects remains a major challenge in reconstructive surgery. The tissue engineering strategy in the development of tissue has opened a new perspective to generate functional tissue for transplantation. Given the poor regenerative properties of cartilage and a limited amount of autologous cartilage availability, intense interest has evoked for tissue engineering approaches for cartilage development to provide better outcomes for patients who require nasal septal reconstruction. Despite numerous attempts to substitute the shapely hyaline cartilage in the nasal cartilages, many significant challenges remained unanswered. The aim of this research was to carry out a critical review of the literature on research work carried out on the development of septal cartilage using a tissue engineering approach, concerning different cell sources, scaffolds and growth factors, as well as its clinical pathway and trials have already been carried out.

Assessment of nanoindentation in stiffness measurement of soft biomaterials: kidney, liver, spleen and uterus

Nanoindentation technology with high spatial resolution and force sensitivity is widely used to measure the mechanical properties of hard biomaterials and tissues. However, its reliability to analyze soft biomaterials and organs has not been tested. Here, we evaluated the utility of nanoindentation to measure the passive mechanical properties of soft biological specimen. Kidney, liver, spleen and uterus samples were harvested from C57BL/6 N mice. We assessed test-retest repeatability in biological specimen and hydrogel controls using Bland-Altman diagrams, intraclass correlation coefficients (ICCs) and the within-subject coefficients of variation (COVs). The results were calculated using Hertzian, JKR and Oliver & Pharr models. Similar to hydrogels, Bland-Altman plots of all biological specimen showed good reliability in stiffness test and retest examinations. In gels, ICCs were larger than 0.8 and COVs were smaller than 15% in all three models. In kidney, liver, spleen and uterus, ICCs were consistently larger than 0.8 only in the Hertzian model but not in the JKR and Oliver & Pharr models. Similarly, COVs were consistently smaller than 15% in kidney, liver, spleen and uterus only in the Hertzian model but not in the other models. We conclude that nanoindentation technology is feasible in detecting the stiffness of kidney, liver, spleen and uterus. The Hertzian model is the preferred method to provide reliable results on ex vivo organ stiffness of the biological specimen under study.

Collagen: quantification, biomechanics, and role of minor subtypes in cartilage

Collagen is a ubiquitous biomaterial in vertebrate animals. Although each of its 28 subtypes contributes to the functions of many different tissues in the body, most studies on collagen or collagenous tissues have focussed on only one or two subtypes. With recent developments in analytical chemistry, especially mass spectrometry, significant advances have been made toward quantifying the different collagen subtypes in various tissues; however, high-throughput and low-cost methods for collagen subtype quantification do not yet exist. In this Review, we introduce the roles of collagen subtypes and crosslinks, and describe modern assays that enable a deep understanding of tissue physiology and disease states. Using cartilage as a model tissue, we describe the roles of major and minor collagen subtypes in detail; discuss known and unknown structure-function relationships; and show how tissue engineers may harness the functional characteristics of collagen to engineer robust neotissues.

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

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Effective enzymatic debridement of burn wounds depends on the denaturation status of collagen

The treatment of burn wounds by enzymatic debridement using bromelain has shown promising results in our burn center. However, inadequate debridement occurred in a few cases in which the etiology of the burn was attributed to relatively low temperature burns. We hypothesized that bromelain is ineffective in burns in which collagen denaturation, which occurs approximately at 65°C, has not taken place. Our objective was to assess whether there is a relationship between the denaturation of collagen and the ability of bromelain to debride acute scald burn wounds of different temperatures. Ex vivo human skin from four different donors was cut into 1x1 cm samples, and scald burns were produced by immersion in water at temperatures of 40°C, 50°C, 60°C, 70°C, and 100°C for 20 minutes. Denaturation of collagen was assessed with histology, using hematoxylin and eosin (H&E) staining and a fluorescently labeled collagen hybridizing peptide (CHP), and with second harmonic generation (SHG) microscopy. Burned samples and one control sample (room temperature) were weighed before and after application of enzymatic debridement to assess the efficacy of enzymatic debridement. After enzymatic debridement, a weight reduction of 80% was seen in the samples heated to 70°C and 100°C, whereas the other samples showed a reduction of 20%. Unfolding of collagen, loss of basket-weave arrangement, and necrosis was seen in samples heated to 60°C or higher. Evident CHP fluorescence, indicative of collagen denaturation, was seen in samples of 60°C, 70°C and 100°C. SHG intensity, signifying intact collagen, was significantly lower in the 70°C and 100°C group (P <.05) compared to the lower temperatures. In conclusion, denaturation of collagen in skin samples occurred between 60°C and 70°C and strongly correlated with the efficacy of enzymatic debridement. Therefore, enzymatic debridement with the use of bromelain is ineffective in scald burns lower than 60°C.

"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.

Thermo-Mechanical Behaviour of Human Nasal Cartilage

The aim of this study was to undergo a comprehensive analysis of the thermo-mechanical properties of nasal cartilages for the future design of a composite polymeric material to be used in human nose reconstruction surgery. A thermal and dynamic mechanical analysis (DMA) in tension and compression modes within the ranges 1 to 20 Hz and 30 °C to 250 °C was performed on human nasal cartilage. Differential scanning calorimetry (DSC), as well as characterization of the nasal septum (NS), upper lateral cartilages (ULC), and lower lateral cartilages (LLC) reveals the different nature of the binding water inside the studied specimens. Three peaks at 60–80 °C, 100–130 °C, and 200 °C were attributed to melting of the crystalline region of collagen matrix, water evaporation, and the strongly bound non-interstitial water in the cartilage and composite specimens, respectively. Thermogravimetric analysis (TGA) showed that the degradation of cartilage, composite, and subcutaneous tissue of the NS, ULC, and LLC take place in three thermal events (~37 °C, ~189 °C, and ~290 °C) showing that cartilage releases more water and more rapidly than the subcutaneous tissue. The water content of nasal cartilage was estimated to be 42 wt %. The results of the DMA analyses demonstrated that tensile mode is ruled by flow-independent behaviour produced by the time-dependent deformability of the solid cartilage matrix that is strongly frequency-dependent, showing an unstable crystalline region between 80–180 °C, an amorphous region at around 120 °C, and a clear glass transition point at 200 °C (780 kJ/mol). Instead, the unconfined compressive mode is clearly ruled by a flow-dependent process caused by the frictional force of the interstitial fluid that flows within the cartilage matrix resulting in higher stiffness (from 12 MPa at 1 Hz to 16 MPa at 20 Hz in storage modulus). The outcomes of this study will support the development of an artificial material to mimic the thermo-mechanical behaviour of the natural cartilage of the human nose.

Toward tissue-engineering of nasal cartilages

Nasal cartilage pathologies are common; for example, up to 80% of people are afflicted by deviated nasal septum conditions. Because cartilage provides the supportive framework of the nose, afflicted patients suffer low quality of life. To correct pathologies, graft cartilage is often required. Grafts are currently sourced from the patient's septum, ear, or rib. However, their use yields donor site morbidity and is limited by tissue quantity and quality. Additionally, rhinoplasty revision rates exceed 15%, exacerbating the shortage of graft cartilage. Alternative grafts, such as irradiated allogeneic rib cartilage, are associated with complications. Tissue-engineered neocartilage holds promise to address the limitations of current grafts. The engineering design process may be used to create suitable graft tissues. This process begins by identifying the surgeon's needs. Second, nasal cartilages' properties must be understood to define engineering design criteria. Limited investigations have examined nasal cartilage properties; numerous additional studies need to be performed to examine topographical variations, for example. Third, tissue-engineering processes must be applied to achieve the engineering design criteria. Within the recent past, strategies have frequently utilized human septal chondrocytes. As autologous and allogeneic rib graft cartilage is used, its suitability as a cell source should also be examined. Fourth, quantitative verification of engineered neocartilage is critical to check for successful achievement of the engineering design criteria. Finally, following the FDA paradigm, engineered neocartilage must be orthotopically validated in animals. Together, these steps delineate a path to engineer functional nasal neocartilages that may, ultimately, be used to treat human patients. STATEMENT OF SIGNIFICANCE: Nasal cartilage pathologies are common and lead to greatly diminished quality of life. The ability to correct pathologies is limited by cartilage graft quality and quantity, as well as donor site morbidity and surgical complications, such as infection and resorption. Despite the significance of nasal cartilage pathologies and high rhinoplasty revision rates (15%), little characterization and tissue-engineering work has been performed compared to other cartilages, such as articular cartilage. Furthermore, most work is published in clinical journals, with little in biomedical engineering. Therefore, this review discusses what nasal cartilage properties are known, summarizes the current state of nasal cartilage tissue-engineering, and makes recommendations via the engineering design process toward engineering functional nasal neocartilage to address current limitations.