Generative surgery of cultured autologous auricular chondrocytes for nasal augmentation

Cartilage Tissue Engineering for Nasal Alar and Auricular Reconstruction: A Critical Review of the Literature and Implications for Practice in Dermatologic Surgery

BACKGROUND

Reconstructing defects requiring replacement of nasal or auricular cartilage after Mohs micrographic surgery can at times be challenging. While autologous cartilage grafting is considered the mainstay for repair, it may be limited by cartilage quality/quantity, donor site availability/morbidity, and surgical complications. Tissue-engineered cartilage has recently shown promise for repairing properly selected facial defects.

OBJECTIVE

To (1) provide a comprehensive overview of the literature on the use of tissue-engineered cartilage for nasal alar and auricular defects, and (2) discuss this technology's advantages and future implications for dermatologic surgery.

MATERIALS AND METHODS

A literature search was performed using PubMed/MEDLINE and Google Scholar databases. Studies discussing nasal alar or auricular cartilage tissue engineering were included.

RESULTS

Twenty-seven studies were included. Using minimal donor tissue, tissue-engineered cartilage can create patient-specific, three-dimensional constructs that are biomechanically and histologically similar to human cartilage. The constructs maintain their shape and structural integrity after implantation into animal and human models.

CONCLUSION

Tissue-engineered cartilage may be able to replace native cartilage in reconstructing nasal alar and auricular defects given its ability to overcome several limitations of autologous cartilage grafting. Although further research is necessary, dermatologic surgeons should be aware of this innovative technique and its future implications.

Novel method for correcting cephalic rotation in Asian nasal tip plasty

BACKGROUND

To correct nasal tip cephalic rotation, SEG made of cartilage or Medpor are often used in rhinoplasty. These techniques require extensive experience for the surgeon, and not all patients can accept this procedure. In this research, we introduce a new method to correct nasal tip cephalic rotation that is relatively simple and rapid.

METHODS

Fifty-nine patients who had rhinoplasty using our scaffold were enrolled in the study between January 2020 and January 2021. The authors evaluated the change of nasolabial angel by photogrammetry using standardized clinical photogrammetric techniques. Patients' satisfaction regarding postoperative results was also surveyed.

RESULTS

The mean postoperative follow-up duration was 12 months. No complication (infection, extrusion, and displacement) was happened in all patients. Analysis showed our scaffold can correct nasal tip cephalic rotation effectively (98.61±1.21 preoperatively and 89.68±0.99 postoperatively, P<0.0001). And the patient satisfaction rate is 98%.

CONCLUSION

We constructed an integrated scaffold by simply folding and suturing a high-density polyethylene sheet (Su-Por) sheet to correct nasal tip cephalic rotation. Using the scaffold we designed, we did not need to alter the structure of the nasal septum, which reduced the operative duration and simplified the surgical procedure.

Experience With Autologous Nasal Septum Cartilage Combined With Conchal Cartilage in Nasal Tip Reconstruction

OBJECTIVE

There has been an increase in use of autologous costal cartilage for nasal tip shaping material. However, there are deficiencies in using this plastic material, such as a hard nasal tip, poor nasal tip elasticity and mobility postoperatively, and some nasal tip skin thinning that allows the shape of the cartilage grafts to be felt on the surface of the nasal tip skin. To address these problems, we have combined autologous nasal septum cartilage and conchal cartilage as nasal tip graft materials, which achieve a natural shape and realistic touch postoperatively.

METHODS

From January 2017 to September 2019, a total of 47 patients with nasal septal cartilage combined with conchal cartilage transplantation for nasal tip plasty were screened for a retrospective study. They were followed up and evaluated for 6 to 25 months postoperatively. The operation was performed through an incision in the nose. During the operation, a piece of septal cartilage was cut to make a columella strut. Using one side of the cavitas conchae and cymba conchae cartilage as the graft material, 2 long strips of cartilage were excised for the septum extension graft, and a piece of cap cartilage was transplanted to the top of the nasal tip cartilage scaffold.

RESULTS

The time between the operation and follow-up was greater than 6 months, with the range of follow-up and evaluation being from 6 to 25 months. Forty-six patients were satisfied with the shape of the nose. One patient complained that the nasal tip was round and large after 1 month postoperatively, but after 6 months, he was satisfied with the shape of the nasal tip after daily use of a nasal clip. In one male case, the implant was removed more than 7 months postoperatively because of hematoma and infection secondary to nasal trauma. There were 2 cases of nasal tip numbness, both of which recovered spontaneously after 12 months. After the operation, the shape of the nasal tip was round, no cartilage contour was seen on the surface, no collapse of upper nasal tip, no obvious deviation of the nasal dorsum and columella, and no deformation and displacement of the nasal tip cartilage scaffold. At the 6-month follow-up visit, each patient palpated the nasal tip for evaluation. Most patients felt their nose felt realistic and that they had good nasal tip motion. Only 1 patient felt that the nasal tip and the nasal dorsum were moving together when the tip of the nose was being pushed.

CONCLUSIONS

Nasal septum cartilage and conchal cartilage can be combined as a graft material for reconstruction of the nasal tip. This technique uses different characteristics of each of the 2 cartilages to achieve a more realistic and esthetic outcome.

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.

New Concepts in Dorsal Nasal Augmentation

Dorsal augmentation is commonly indicated in many primary and secondary aesthetic nose surgeries. Throughout the history, various synthetic and autogenous materials have been used for dorsal augmentation. In this article, we give an overview of basic concepts of cartilage grafting, review new concepts of dorsal augmentation, and discuss some emerging engineering modalities.

In vivo evaluation of a regenerative approach to nasal dorsum augmentation with a polycaprolactone-based implant

Background

Alternative techniques for nasal dorsum augmentation are of paramount importance in reconstructive and plastic surgery. In contrast to autologous cartilage grafts, tissue-engineered grafts can be created de novo and yield low–none donor site morbidity as compared to autologous grafts like rib or ear cartilage. To address this demand, this study investigated the in vivo regenerative potential of polycaprolactone-based implants as an alternative to autologous cartilage grafting during rhinoplasty.

Methods

Implants were placed at the nasal dorsum in two groups of minipigs and kept in situ for 2 and 6 months, respectively. Subsequently, the implants were harvested and examined by histology (hematoxylin–eosin, alcian blue, and safranin O) and immunostaining (collagen I and collagen II). Further analysis was performed to measure diameter and distance of polycaprolactone struts.

Results

Histological examination revealed a persistent formation of connective tissue with some spots resembling a cartilaginous-like matrix after 6 months. In such areas, cells of chondrocyte appearance could be identified. There was a significant decrease in strut diameter but a non-significant difference in strut distance.

Conclusion

Our results indicated that the investigated polycaprolactone-based implants have shown a regenerative and stable nasal dorsum augmentation after 6 months in vivo. Thus, we believe that customized polycaprolactone-based implants could become an alternative technique for nasal dorsum augmentation without the need for autologous cartilage grafts.

Application of a Porous Polyethylene Spreader Graft for Nasal Lengthening in Asian Patients

BACKGROUND

Rhinoplasty maneuvers to lengthen the nose include placing an alloplastic implant, caudally rotating the lower lateral cartilage (LLC), and stretching the soft tissue skin envelope (STSE) downward. Tissue tension associated with these procedures can result in implant extrusion or tip retraction.

OBJECTIVES

The authors performed rhinoplasty with implantation of porous polyethylene (Medpor). The Medpor device enabled transfer of tension from the LLC and STSE to the juncture of the septal cartilage and upper lateral cartilage (ULC), thereby stabilizing the nasal structures.

METHODS

Twenty-six patients who underwent rhinoplasty with nasal augmentation and lengthening were evaluated in a prospective study. Two pieces of Medpor were placed as a spreader graft, and a third piece was inserted as a columellar strut. The released LLC was rotated caudally, and the domal segments were wrapped over the caudally projected tip of the implant. Surgical outcomes were assessed with a patient satisfaction questionnaire and by photogrammetry.

RESULTS

Patients were monitored for an average of 9.6 months. The patients' mean nasolabial angle (NLA) was 106.2° ± 4.7° preoperatively and 94.3° ± 3.7° postoperatively (t < 0.0001). Most patients were fairly or completely satisfied with the operative outcome. One patient had impending implant extrusion and underwent explanation.

CONCLUSIONS

Medpor material is easy to shape and is sufficiently strong to function as a spreader graft and withstand the tension associated with repositioning of the LLC and STSE.

LEVEL OF EVIDENCE 4

Autotransplantation of Monkey Ear Perichondrium-Derived Progenitor Cells for Cartilage Reconstruction

We recently developed a promising regenerative method based on the xenotransplantation of human cartilage progenitor cells, demonstrating self-renewing elastic cartilage reconstruction with expected long-term tissue restoration. However, it remains unclear whether autotransplantation of cartilage progenitors may work by a similar principle in immunocompetent individuals. We used a nonhuman primate (monkey) model to assess the safety and efficacy of our regenerative approach because the model shares characteristics with humans in terms of biological functions, including anatomical features. First, we identified the expandable and multipotent progenitor population from monkey ear perichondrium and succeeded in inducing chondrocyte differentiation in vitro. Second, in vivo transplanted progenitor cells were capable of reconstructing elastic cartilage by xenotransplantation into an immunodeficient mouse. Finally, the autologous monkey progenitor cells were transplanted into the subcutaneous region of a craniofacial section and developed mature elastic cartilage of their own 3 months after transplantation. Furthermore, we attempted to develop a clinically relevant, noninvasive monitoring method using magnetic resonance imaging (MRI). Collectively, this report shows that the autologous transplantation of cartilage progenitors is potentially effective for reconstructing elastic cartilage. This principle will be invaluable for repairing craniofacial injuries and abnormalities in the context of plastic and reconstructive surgery.

Correction of secondary deformity after Nuss procedure for pectus excavatum by means of cultured autologous cartilage cell injection

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Different strategies are available for the re-correction after pectus excavatum surgery.

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We cultured and propagated chondrocytes taken from a patient’s auricular cartilage.

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The cultured chondrocytes are transplanted to the concave part of the chest.

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The chest shape improved and the transplanted cells consolidated, forming part of the chest wall.

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Transplantation of cultured chondrocytes is a useful treatment for pectus excavatum.

Introduction

For some cases of pectus excavatum, ideal chest shape cannot be achieved solely by performing the Nuss procedure. This manuscript presents a case where the residual deformity following Nuss was corrected using injection-transplantation of cultured autologous chondrocytes.

Presentation of case

The treatment was performed for an 18-year-old male, who sought improvement of his chest shape after previously undergoing the Nuss procedure. A 1 cm² auricular cartilage piece was harvested from his ear. Chondrocytes were isolated from the cartilage piece and were cultured. The cultured chondrocytes were processed into gel form and were injection-transplanted to the deformed region of the patient's chest. The grafted chondrocytes consolidated in one month, presenting elasticity equivalent to ordinary costal cartilage. The patient's chest remains in an optimal shape after a one-year postoperative follow up.

Discussion

Secondary correction of the chest deformity after previous operation for pectus excavatum is often tricky, because of the possible adhesion of the lungs or pericardium with the thoracic wall. Transplantation of cultured autologous chondrocytes does not require intra-thoracic maneuvers, and so is less invasive than other surgical interventions. Hence, priority can be placed, in some cases, on the chondrocyte transplantation rather than the re-correction of the thorax with the Nuss procedure or Ravitch procedure.

Conclusion

Transplantation of cultured autologous chondrocytes is recommended as a useful option for secondary correction of chest deformity after the Nuss procedure.

Tissue engineering for otorhinolaryngology-head and neck surgery

Tissue regeneration in otorhinolaryngology-head and neck surgery is a diverse area filled with specialized tissues and functions. Head and neck structures govern many of the 5 senses, swallowing, breathing, communication, facial animation, and aesthetics. Loss of these functions can have a severe negative effect on patient quality of life. Regenerative medicine techniques have the potential to restore these functions while minimizing the risks associated with traditional reconstruction techniques. This article serves as a review and update on some of the regenerative medicine research in this field. A description of the predominant clinical problems is presented, followed by a discussion of some of the most promising research working toward a solution. There are many noteworthy findings appropriate for inclusion, but limitations preclude mention of them all. This article focuses on laryngeal surgery, craniofacial reconstruction and plastic surgery, and otology and hearing.

Extensively Expanded Auricular Chondrocytes Form Neocartilage In Vivo

OBJECTIVE

Our goal was to engineer cartilage in vivo using auricular chondrocytes that underwent clinically relevant expansion and using methodologies that could be easily translated into health care practice.

DESIGN

Sheep and human chondrocytes were isolated from auricular cartilage biopsies and expanded in vitro. To reverse dedifferentiation, expanded cells were either mixed with cryopreserved P0 chondrocytes at the time of seeding onto porous collagen scaffolds or proliferated with basic fibroblast growth factor (bFGF). After 2-week in vitro incubation, seeded scaffolds were implanted subcutaneously in nude mice for 6 weeks. The neocartilage quality was evaluated histologically; DNA and glycosaminoglycans were quantified. Cell proliferation rates and collagen gene expression profiles were assessed.

RESULTS

Clinically sufficient over 500-fold chondrocyte expansion was achieved at passage 3 (P3); cell dedifferentiation was confirmed by the simultaneous COL1A1/3A1 gene upregulation and COL2A1 downregulation. The chondrogenic phenotype of sheep but not human P3 cells was rescued by addition of cryopreserved P0 chondrocytes. With bFGF supplementation, chondrocytes achieved clinically sufficient expansion at P2; COL2A1 expression was not rescued but COL1A1/3A1genes were downregulated. Although bFGF failed to rescue COL2A1 expression during chondrocyte expansion in vitro, elastic neocartilage with obvious collagen II expression was observed on porous collagen scaffolds after implantation in mice for 6 weeks.

CONCLUSIONS

Both animal and human auricular chondrocytes expanded with low-concentration bFGF supplementation formed high-quality elastic neocartilage on porous collagen scaffolds in vivo.

Growth factor stimulation improves the structure and properties of scaffold-free engineered auricular cartilage constructs

The reconstruction of the external ear to correct congenital deformities or repair following trauma remains a significant challenge in reconstructive surgery. Previously, we have developed a novel approach to create scaffold-free, tissue engineering elastic cartilage constructs directly from a small population of donor cells. Although the developed constructs appeared to adopt the structural appearance of native auricular cartilage, the constructs displayed limited expression and poor localization of elastin. In the present study, the effect of growth factor supplementation (insulin, IGF-1, or TGF-β1) was investigated to stimulate elastogenesis as well as to improve overall tissue formation. Using rabbit auricular chondrocytes, bioreactor-cultivated constructs supplemented with either insulin or IGF-1 displayed increased deposition of cartilaginous ECM, improved mechanical properties, and thicknesses comparable to native auricular cartilage after 4 weeks of growth. Similarly, growth factor supplementation resulted in increased expression and improved localization of elastin, primarily restricted within the cartilaginous region of the tissue construct. Additional studies were conducted to determine whether scaffold-free engineered auricular cartilage constructs could be developed in the 3D shape of the external ear. Isolated auricular chondrocytes were grown in rapid-prototyped tissue culture molds with additional insulin or IGF-1 supplementation during bioreactor cultivation. Using this approach, the developed tissue constructs were flexible and had a 3D shape in very good agreement to the culture mold (average error <400 µm). While scaffold-free, engineered auricular cartilage constructs can be created with both the appropriate tissue structure and 3D shape of the external ear, future studies will be aimed assessing potential changes in construct shape and properties after subcutaneous implantation.

Engineered autologous cartilage tissue for nasal reconstruction after tumour resection: an observational first-in-human trial

BACKGROUND

Autologous native cartilage from the nasal septum, ear, or rib is the standard material for surgical reconstruction of the nasal alar lobule after two-layer excision of non-melanoma skin cancer. We assessed whether engineered autologous cartilage grafts allow safe and functional alar lobule restoration.

METHODS

In a first-in-human trial, we recruited five patients at the University Hospital Basel (Basel, Switzerland). To be eligible, patients had to be aged at least 18 years and have a two-layer defect (≥50% size of alar subunit) after excision of non-melanoma skin cancer on the alar lobule. Chondrocytes (isolated from a 6 mm cartilage biopsy sample from the nasal septum harvested under local anaesthesia during collection of tumour biopsy sample) were expanded, seeded, and cultured with autologous serum onto collagen type I and type III membranes in the course of 4 weeks. The resulting engineered cartilage grafts (25 mm × 25 mm × 2 mm) were shaped intra-operatively and implanted after tumour excision under paramedian forehead or nasolabial flaps, as in standard reconstruction with native cartilage. During flap refinement after 6 months, we took biopsy samples of repair tissues and histologically analysed them. The primary outcomes were safety and feasibility of the procedure, assessed 12 months after reconstruction. At least 1 year after implantation, when reconstruction is typically stabilised, we assessed patient satisfaction and functional outcomes (alar cutaneous sensibility, structural stability, and respiratory flow rate).

FINDINGS

Between Dec 13, 2010, and Feb 6, 2012, we enrolled two women and three men aged 76-88 years. All engineered grafts contained a mixed hyaline and fibrous cartilage matrix. 6 months after implantation, reconstructed tissues displayed fibromuscular fatty structures typical of the alar lobule. After 1 year, all patients were satisfied with the aesthetic and functional outcomes and no adverse events had been recorded. Cutaneous sensibility and structural stability of the reconstructed area were clinically satisfactory, with adequate respiratory function.

INTERPRETATION

Autologous nasal cartilage tissues can be engineered and clinically used for functional restoration of alar lobules. Engineered cartilage should now be assessed for other challenging facial reconstructions.

FUNDING

Foundation of the Department of Surgery, University Hospital Basel; and Krebsliga beider Basel.

Two-stage transplantation of cell-engineered autologous auricular chondrocytes to regenerate chondrofat composite tissue: clinical application in regenerative surgery

BACKGROUND

The authors have developed a unique multilayered culture method that expands to large volumes elastic chondrocytes from a small piece of human auricular cartilage. In this study, the authors applied the two-stage transplantation method for cultured auricular chondrocytes to difficult cases of nasal/chin reconstruction where subcutaneous tissue is thin or scarred.

METHODS

Auricular chondrocytes were cultured and expanded to sufficiently large volumes, and then, in a two-stage transplantation process, injection-transplanted into a patient's lower abdomen, where they were regenerated into larger chondrofat composite tissue in 6 months and used as a material for nasal/chin reconstruction. The authors then performed histologic and electron microscopic analysis of serial cross-sections and magnetic resonance imaging analysis of the chondrofat composite tissue.

RESULTS

The cultured auricular chondrocytes consistency regenerated intraabdominally to a larger, stable neocartilage, with adherent fat tissue within 6 months. Eighteen patients (nose, n = 14; chin, n = 4) underwent this procedure, and the chondrofat composite tissue was stable after 1 to 5 years' postoperative follow-up. The chondrofat composite tissue maintained good shape, with no major complications. Magnetic resonance imaging showed that the chondrofat composite tissue was regenerated and vascularized in the abdomen in all 18 cases (100 percent). Infection and total absorption were not seen. Only partial absorption was noted (5.6 percent).

CONCLUSIONS

The chondrofat composite tissue was found to be a new innovative graft material in which neocartilage is regenerated to be continuous with fat tissue by means of the neoperichondrium. It has thereby become possible to perform the previously impossible simultaneous reconstruction of cartilage and fat tissue.

Development of scaffold-free elastic cartilaginous constructs with structural similarities to auricular cartilage

External ear reconstruction with autologous cartilage still remains one of the most difficult problems in the fields of plastic and reconstructive surgery. As the absence of tissue vascularization limits the ability to stimulate new tissue growth, relatively few surgical approaches are currently available (alloplastic implants or sculpted autologous cartilage grafts) to repair or reconstruct the auricle (or pinna) as a result of traumatic loss or congenital absence (e.g., microtia). Alternatively, tissue engineering can offer the potential to grow autogenous cartilage suitable for implantation. While tissue-engineered auricle cartilage constructs can be created, a substantial number of cells are required to generate sufficient quantities of tissue for reconstruction. Similarly, as routine cell expansion can elicit negative effects on chondrocyte function, we have developed an approach to generate large-sized engineered auricle constructs (≥3 cm(2)) directly from a small population of donor cells (20,000-40,000 cells/construct). Using rabbit donor cells, the developed bioreactor-cultivated constructs adopted structural-like characteristics similar to native auricular cartilage, including the development of distinct cartilaginous and perichondrium-like regions. Both alterations in media composition and seeding density had profound effects on the formation of engineered elastic tissue constructs in terms of cellularity, extracellular matrix accumulation, and tissue structure. Higher seeding densities and media containing sodium bicarbonate produced tissue constructs that were closer to the native tissue in terms of structure and composition. Future studies will be aimed at improving the accumulation of specific tissue constituents and determining the clinical effectiveness of this approach using a reconstructive animal model.

Current concepts and advances in the application of tissue engineering in otorhinolaryngology and head and neck surgery

OBJECTIVE

This paper reviews the progress in the rapidly expanding scientific discipline of tissue engineering, which may have an integral role in the future of otorhinolaryngology. This article seeks to inform on the current concepts and principles of tissue engineering, and describe the state of the art research and developments in this exciting field as applied to ENT and head and neck surgery.

METHOD

In order to carry out a comprehensive review of the literature spanning the past 30 years, a search of relevant publications was performed using the Web of Knowledge, Medline and PubMed databases.

RESULTS

This search identified 85 scholarly articles, which were utilised as the basis of this review.

CONCLUSION

Given the current rate of development of tissue engineering research, it is likely that tissue-engineered implants will be widely used in surgical practice, including ENT and head and neck surgery.

Soft versus hard implants in dorsal nasal augmentation: a comparative clinical study

BACKGROUND

Dorsal nasal augmentation plays an important role in cosmetic and reconstructive rhinoplasties performed to achieve an aesthetically pleasing result while creating facial harmony. Although it is known that the ideal implant should be biocompatible, biointegrated, nonabsorbable, and without inflammatory response, the selection of an ideal implant still remains controversial as to whether it should be biologic or synthetic. This study introduces a new question: ''What is better for the nasal dorsum, a soft or a hard implant?''.

METHODS

In this study, 21 women and 7 men with a mean age of 23.5 years underwent augmentation rhinoplasty between December 2007 and July 2011. Conchal and septal cartilage grafts and Medpor were categorized as hard implants and applied for 15 patients. Soft implants, inserted in 13 patients, included diced auricular cartilage wrapped in Surgicel sheets, dermofat blocks, and rolls of Prolene mesh.

RESULTS

Patient satisfaction was assessed through simple postoperative questionnaires. The satisfaction rate in the soft implant group was 100 %, whereas the overall satisfaction rate was 82.2 %. Unsatisfactory results and complications were recorded in the hard implant group, which had a dissatisfaction rate of 33.3 %, contributing to a general dissatisfaction rate of 17.8 % in the whole series.

CONCLUSION

The authors recommend soft implants for both aesthetic and reconstructive surgeries because of their better ability to achieve a dorsum with a smoother contour and pad. Soft implants have fewer complications and higher satisfaction rates and can be applied for most indications using both closed and open methods.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article.

Cell-engineered human elastic chondrocytes regenerate natural scaffold in vitro and neocartilage with neoperichondrium in the human body post-transplantation

We have developed a unique method that allows us to culture large volumes of chondrocyte expansion from a small piece of human elastic cartilage. The characteristic features of our culturing method are that fibroblast growth factor-2 (FGF2), which promotes proliferation of elastic chondrocytes, is added to a culture medium, and that cell-engineering techniques are adopted in the multilayered culture system that we have developed. We have subsequently discovered that once multilayered chondrocytes are transplanted into a human body, differentiation induction that makes use of surrounding tissue occurs in situ, and a large cartilage block is obtained through cartinogenesis and matrix formation. We have named this method two-stage transplantation. We have clinically applied this transplantation method to the congenital ear defect, microtia, and reported successful ear reconstruction. In our present study, we demonstrated that when FGF2 was added to elastic chondrocytes, the cell count increased and the level of hyaluronic acid, which is a major extracellular matrix (ECM) component, increased. We also demonstrated that these biochemical changes are reflected in the morphology, with the elastic chondrocytes themselves producing a matrix and fibers in vitro to form a natural scaffold. We then demonstrated that inside the natural scaffold thus formed, the cells overlap, connect intercellularly to each other, and reconstruct a cartilage-like three-dimensional structure in vitro. We further demonstrated by immunohistochemical analysis and electron microscopic analysis that when the multilayered chondrocytes are subsequently transplanted into a living body (abdominal subcutaneous region) in the two-stage transplantation process, neocartilage and neoperichondrium of elastic cartilage origin are regenerated 6 months after transplantation. Further, evaluation by dynamic mechanical analysis showed the regenerated neocartilage to have the same viscoelasticity as normal auricular cartilage. Using our multilayered culture system supplemented with FGF2, elastic chondrocytes produce an ECM and also exhibit an intercellular network; therefore, they are able to maintain tissue integrity post-transplantation. These findings realized a clinical application for generative cartilage surgery.

Advancing nasal reconstructive surgery: the application of tissue engineering technology

Cartilage tissue engineering is a rapidly progressing area of regenerative medicine with advances in cell biology and scaffold engineering constantly being investigated. Many groups are now capable of making neocartilage constructs with some level of morphological, biochemical, and histological likeness to native human cartilage tissues. The application of this useful technology in articular cartilage repair is well described in the literature; however, few studies have evaluated its application in head and neck reconstruction. Although there are many studies on auricular cartilage tissue engineering, there are few studies regarding cartilage tissue engineering for complex nasal reconstruction. This study therefore highlighted the challenges involved with nasal reconstruction, with special focus on nasal cartilage tissue, and examined how advancements made in cartilage tissue engineering research could be applied to improve the clinical outcomes of total nasal reconstructive surgery.

Chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells in self-gelling alginate discs reveals novel chondrogenic signature gene clusters

We have used a disc-shaped self-gelling alginate hydrogel as a scaffold for in vitro chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells. The comparison of monolayer cells and alginate embedded cells with or without differentiation medium allowed us to perform a detailed kinetic study of the expression of a range of genes and proteins known to be involved in chondrogenesis, using real-time polymerase chain reaction, fluorescence immunohistochemistry, and glycosaminoglycan measurement in the supernatant. mRNA encoding type II collagen (COL2), COL10, aggrecan, and SOX5, 6, and 9 were greatly elevated already at day 7, whereas COL1 and versican mRNA were gradually reduced. COL2 and aggrecan were dispersed throughout the extracellular matrix at day 21, whereas COL10 distribution was mainly intra/pericellular. COL1 seemed to be produced by only some of the cells. SOX proteins were predominantly localized in the nuclei. Then, using microarray analysis, we identified a signature cluster of extracellular matrix and transcription factor genes upregulated during chondrogenesis similar to COL2A1, and clusters of genes involved in immune responses, blood vessel development, and cell adhesion downregulated similar to the chemokine CXCL12. Analysis of the signature chondrogenic clusters, including novel potential marker genes identified here, may provide a better understanding of how the stem cell fate could be directed to produce perfect hyaline cartilage implants.