Biochemical properties of tissue-engineered cartilage

Double network hydrogels encapsulating genetically modified dedifferentiated chondrocytes for auricular cartilage regeneration

Microtia profoundly affects patients' appearance and psychological well-being. Tissue engineering ear cartilage scaffolds have emerged as the most promising solution for ear reconstruction. However, constructing tissue engineering ear cartilage scaffolds requires multiple passaging of chondrocytes, resulting in their dedifferentiation and loss of their special phenotypes and functions. To tackle these issues, here we employ guanidinobenzoic acid (GBA) modified generation 5 polyamidoamine (PAMAM) dendrimers (PG) as a Runx1 plasmid carrier to construct PG/pRunx1 polyplex nanoparticles. The PG/pRunx1 polyplexes are transfected into human auricular chondrocytes, significantly mitigating chondrocyte dedifferentiation and enhancing cartilage regeneration during the in vitro culture. Furthermore, we develop highly porous double-network hydrogels based on methacrylate-functionalized and oxidized chondroitin sulfate and carbohydrazide-modified gelatin and the hydrogels possessed both dynamic adaptability and mechanical support characteristics by reversible dynamic covalent crosslinking and static covalent crosslinking, serving as an ideal scaffold for tissue engineering. Consequently, chondrocytes treated with PG/pRunx1 polyplex nanoparticles are incorporated into the hydrogels to construct tissue-engineered auricular cartilage scaffolds. After subcutaneous implantation in nude mice, the scaffolds containing chondrocytes treated with PG/pRunx1 nanoparticles showed more mature cartilaginous tissue, characterized by prominent ECM deposition and enhanced chondrogenesis. Therefore, this research provides a novel strategy for the development of tissue-engineered auricular cartilage scaffolds.

Endocrine Petrified Ear: Associated Endocrine Conditions in Auricular Calcification/Ossification (A Sample-Focused Analysis)

Petrified ear (PE), an exceptional entity, stands for the calcification ± ossification of auricular cartilage (CAC/OAC); its pathogenic traits are still an open matter. Endocrine panel represents one of the most important; yet, no standard protocol of assessments is available. Our objective was to highlight most recent PE data and associated endocrine (versus non-endocrine) ailments in terms of presentation, imagery tools, hormonal assessments, biopsy, outcome, pathogenic features. This was a comprehensive review via PubMed search (January 2000-March 2024). A total of 75 PE subjects included: 46 case reports/series (N = 49) and two imagery-based retrospective studies (N = 26) with CAC/OAC prevalence of 7-23% (N = 251) amid routine head/temporal bone CT scans. Endocrine PE (EPE): N = 23, male/female ratio = 10.5; average age = 56.78, ranges: 22-79; non-EPE cohort: N = 26; male/female ratio = 1.88, mean age = 49.44; ranges: 18-75 (+a single pediatric case).The longest post-diagnosis follow-up was of 6-7 years. The diagnosis of PE and endocrine anomalies was synchronous or not (time gap of 10-20 years). A novel case in point (calcified EPE amid autoimmune poly-endocrine syndrome type 2 with a 10-year post-diagnosis documented follow-up) was introduced. We re-analyzed EPE and re-classified another five subjects as such. Hence, the final EPE cohort (N = 50) showed: adrenal insufficiency was the most frequent endocrine condition (36%) followed by hypopituitarism (22%) and hypothyroidism (18%); 39% of the patients with adrenal failure had Addison's disease; primary type represented 72% of all cases with hypothyroidism; an endocrine autoimmune (any type) component was diagnosed in 18%. We propose the term of "endocrine petrified ear" and a workflow algorithm to assess the potential hormonal/metabolic background in PE.

Hydrogel composite mimics biological tissues

A novel composite hydrogel was developed that shows remarkable similarities to load bearing biological tissues. The composite gel consisting of a poly(vinyl alcohol (PVA) matrix filled with poly(acrylic acid) (PAA) microgel particles exhibits osmotic and mechanical properties that are qualitatively different from regular gels. In the PVA/PAA system the swollen PAA particles "inflate" the PVA network. The swelling of the PAA is limited by the tensile stress P_el developing in the PVA matrix. P_el increases with increasing swelling degree, which is opposite to the decrease of the elastic pressure observed in regular gels. The maximum tensile stress Pmaxel can be identified as a quantity that defines the load bearing ability of the composite gel. Systematic osmotic swelling pressure measurements have been made on PVA/PAA gels to determine the effects of PVA stiffness, PAA crosslink density, and Ca²⁺ ion concentration on Pmaxel. It is found that Pmaxel increases with the stiffness of the PVA matrix, and decreases with (i) increasing crosslink density of the PAA and (ii) increasing Ca²⁺ ion concentration. Small angle neutron scattering (SANS) measurements indicate only a weak interaction between the PVA and PAA gels. It is demonstrated that the osmotic swelling pressure of PVA/PAA composite gels reproduces the osmotic behavior of healthy and osteoarthritic cartilage.

Umbilical Cord Mesenchymal Stromal Cells for Cartilage Regeneration Applications

Chondropathies are increasing worldwide, but effective treatments are currently lacking. Mesenchymal stromal cell (MSCs) transplantation represents a promising approach to counteract the degenerative and inflammatory environment characterizing those pathologies, such as osteoarthritis (OA) and rheumatoid arthritis (RA). Umbilical cord- (UC-) MSCs gained increasing interest due to their multilineage differentiation potential, immunomodulatory, and anti-inflammatory properties as well as higher proliferation rates, abundant supply along with no risks for the donor compared to adult MSCs. In addition, UC-MSCs are physiologically adapted to survive in an ischemic and nutrient-poor environment as well as to produce an extracellular matrix (ECM) similar to that of the cartilage. All these characteristics make UC-MSCs a pivotal source for a stem cell-based treatment of chondropathies. In this review, the regenerative potential of UC-MSCs for the treatment of cartilage diseases will be discussed focusing on in vitro, in vivo, and clinical studies.

Craniofacial implants in a failed autologous reconstruction of microtia: a case report

Plastic surgical reconstruction is considered to be the gold standard for the repair of microtia as the results are permanent and constructed from the patient's own tissue; however, the multiple surgeries required and the difficulty in attaining adequate cosmetic results often result in patients choosing a prosthesis as a long-term rehabilitation. Advances in osseointegration in the craniofacial region have improved the outcomes with auricular prosthetics by providing a reliable method of attachment of the prosthesis and increasing patient acceptance. A case presentation illustrates the results of both treatment modalities and examines the outcomes on the same patient.

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

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

The in vivo chondrogenesis of cartilage stem/progenitor cells from auricular cartilage and the perichondrium

Bone marrow-derived stem cells are commonly studied for cartilage tissue engineering and regeneration medicine applications, but their ossification tendency and their limited capacity for chondrogenic differentiation depending on the donor age limit their clinical application. Cartilage stem/progenitor cells are ideal seeding cells, as cartilage stem/progenitor cells from auricular cartilage and the perichondrium have the inherent advantages of chondrogenesis capacity and an easy and nontraumatic harvesting process, displaying promise for applications. The identification and comparison of cartilage stem/progenitor cells from auricular cartilage and the perichondrium in vitro were explored in our previous study, but the in vivo chondrogenesis of these cells has not been fully examined. In the current study, we explored the ectopic chondrogenesis of cartilage stem progenitor/cells from auricular cartilage and the perichondrium after chondrogenic induction in vitro. Our results suggest that stem/progenitor cells from auricular cartilage exhibit significantly better chondrogenesis than those from the perichondrium in vivo, with upregulated chondrogenic genes and a stable cartilage phenotype, as well as good mechanical properties, indicating that stem/progenitor cells from auricular cartilage could be one type of ideal seeding cells for cartilage tissue engineering.

[Surgical treatment progress of acquired auricular defects]

Objective

To review the surgical treatment progress in repair and reconstruction of acquired auricle defects.

Methods

The related literature concerning the surgical methods and techniques for acquired auricle defects was reviewed and summarized.

Results

In order to attain an aesthetic ear with a clear structure, the location, size, and condition of surrounding skin must be taken into account when planning excision and repair. The application of tissue engineering and digital technology for acquired auricle defects can achieve a satisfactory effectiveness.

Conclusion

The surgical programs for acquired auricular defects have been constantly improved in recent years, and the emerging medical technologies also play a promoting role in the process, which providing a great deal of reference for obtaining structurally clear and stereoscopic auricle.

A pilot study comparing mechanical properties of tissue-engineered cartilages and various endogenous cartilages

BACKGROUND

Mechanical properties of tissue-engineered cartilage and a variety of endogenous cartilage were measured. The main goal was to evaluate if the tissue-engineered cartilage have similar mechanical characteristics to be replaced with rib cartilage in microtia reconstruction. Such study lays the foundation for future human clinical trials for microtia reconstruction.

METHOD

Atomic force microscopy and compression testing were used to measure the viscoelasticity of tissue-engineered cartilage (stem cell seeded on Poly lactic co-glycolytic acid nanofibers and Pellet) and endogenous cartilage: conchal bowl, microtic ears, preauricular remnants, and rib. Atomic force microscopy, calculates biomaterial elasticity through force-deformation measurement and Hertz model. Compression testing determines the stress relaxation by measuring slope of stress reduction at 10% strain.

FINDING

Tissue-engineered cartilage demonstrated elasticity (4.6kPa for pellet and 6.6kPa for PLGA) and stress relaxation properties (7.6 (SD 1.1) kPa/s for pellet) most similar to those of native conchal bowl cartilage (31.8 (SD 18) kPa for the elasticity and 15.1 (SD 2.1) kPa/s for stress relaxation factor). Rib cartilage was most dissimilar from the mechanical characteristics of conchal cartilage and demonstrated the highest elastic modulus (361 (SD 372) kPa). Moreover, except preauricular cartilage samples, the level of elastic modulus increased with age.

INTERPRETATION

The use of tissue-engineered cartilage developed via PLGA and Pellet methods, may be an appropriate substitute for rib cartilage in the reconstruction of microtic ears, however their mechanical characteristics still need to be improved and require further validation in animal studies.

Bioengineering pediatric scaffold-free auricular cartilaginous constructs

OBJECTIVE

The use of exogenous materials as scaffolds in cartilage tissue engineering has limited the clinical application of resultant constructs due to the risk of postoperative complications. In an effort to minimize such complications, we aim to generate human, scaffold-free auricular cartilaginous constructs.

STUDY DESIGN

Laboratory study using pediatric auricular cartilage.

METHODS

Remnant, normal pediatric auricular cartilage samples that would have otherwise been discarded were collected and digested to free cells. Harvested cells were cultured and expanded in vitro for two passages and plated as micromass cultures. The culture medium was replaced with a chemically defined chondrogenic medium, and cellular monolayers surrounding micromass cultures were continuously scraped off. Constructs were allowed to mature for a period of 8 weeks.

RESULTS

Micromass constructs showed mechanical stability and structurally resembled native auricular tissue, with a perichondrium-like layer of cells surrounding the inner cartilaginous zone. Constructs accumulated equivalent sulphated glycosaminoglycan and 50% of collagen content compared to native auricular cartilage by mass, while displaying 156% more cellularity.

CONCLUSIONS

High-density micromass cultures of pediatric auricular chondrocytes can generate stable cartilaginous constructs following prolonged chondrogenic inductions in vitro. This technique is an essential step toward the development of three-dimensional constructs to recreate clinically applicable auricular cartilaginous constructs.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E153-E158, 2017.

Encapsulation of human elastic cartilage-derived chondrocytes in nanostructured fibrin-agarose hydrogels

The generation of elastic cartilage substitutes for clinical use is still a challenge. In this study, we investigated the possibility of encapsulating human elastic cartilage-derived chondrocytes (HECDC) in biodegradable nanostructured fibrin-agarose hydrogels (NFAH). Viable HECDC from passage 2 were encapsulated in NFAH and maintained in culture conditions. Constructs were harvested for histochemical and immunohistochemical analyses after 1, 2, 3, 4 and 5 weeks of development ex vivo. Histological results demonstrated that it is possible to encapsulate HECDC in NFAH, and that HECDC were able to proliferate and form cells clusters expressing S-100 and vimentin. Additionally, histochemical and immunohistochemical analyses of the extracellular matrix (ECM) showed that HECDC synthetized different ECM molecules (type I and II collagen, elastic fibers and proteoglycans) in the NFAH ex vivo. In conclusion, this study suggests that NFAH can be used to generate biodegradable and biologically active constructs for cartilage tissue engineering applications. However, further cell differentiation, biomechanical and in vivo studies are still needed.

Reconstructive Surgery of Auricular Defects: An Overview

Context:

Despite the ongoing advances in surgical procedures and promising progress in bioengineering techniques, auricular reconstruction remains a significant challenge in plastic surgery. There are different causes for acquired auricular defects, including trauma, tumor ablation and burns. The management options for upper, middle and lower third auricular defects are briefly reviewed in the current paper.

Evidence Acquisition:

Original research papers investigating the plastic surgeons, otolaryngologists and maxillofacial surgeons in approaching the complicated issue of auricular reconstruction published from January 1995 to December 2014 were aggregated and used in the current study.

Results:

Utilizing autologous stem cell populations to treat craniofacial defects is a promising field of ongoing investigations. Studies show that cartilage stem/progenitor cells (CSPCs) are highly chondrogenic and can produce elastic reconstructive material with long-term tissue restoration.

Conclusions:

Auricular reconstruction surgery is a challenging plastic procedure that requires great expertise and expert knowledge of the various techniques available. Novel techniques in the fields of reconstructive bioengineering and regenerative medicine are promising but further research is required before widespread clinical application.