In vitro elastic cartilage reconstruction using human auricular perichondrial chondroprogenitor cell-derived micro 3D spheroids

Small spheroids for head and neck cartilage tissue engineering

The demand for cartilage reconstruction in the head and neck region arises frequently due to trauma, malignancies, and hereditary diseases. Traditional tissue engineering produces cartilage from a small biopsy by combining biomaterials and expanded cells. However, this top-down approach is associated with several limitations, including the non-uniform distribution of cells, lack of physiological cell-cell and cell-matrix interactions, and compromised mechanical properties and tissue architecture. The capacity of cells to aggregate into microtissues enables an alternative bottom-up approach to producing cartilage with or without further scaffolding support. Here we explored the optimal conditions for obtaining small spheroids from head and neck cartilage tissues. We used chondrocytes (CCs) and chondroprogenitors (CPCs) isolated from auricular and nasoseptal cartilage to prepare spheroids using ultra-low attachment (ULA) plates or micromass cultures. Different cell densities were tested to estimate the minimal cell number required for optimal spheroid formation. Furthermore, we evaluated the influence of key chondrogenic cytokines, such as transforming growth factor (TGF)-β, connective tissue growth factor (CTGF), and insulin-like growth factor (IGF)-1, on spheroid morphology and the production of cartilage extracellular matrix (ECM) components. Spheroids expressing cartilage markers were formed with 2.5 × 104 cells in a commercially available chondrogenic differentiation medium on ULA plates but not in conventional micromass cultures. Differences were seen in auricular and nasal spheroids with respect to growth patterns and response to cytokine composition. Auricular spheroids were larger and showed size increase in culture, whereas nasal aggregates tended to shrink. Cytokines differentially influenced spheroid growth, and ECM structure and composition. Under all tested conditions, both spheroid types generated one or more cartilage ECM components, including elastin, which was also found in nasal spheroids despite their hyaline origin. Our results suggest that spheroid cultures can offer a viable approach to generating mature cartilage tissue without a biomaterial scaffold. Furthermore, nasal CCs and CPCs can be used to generate elastic cartilage. The findings of the study provide technical insights toward the goal of obtaining cartilage microtissues that can be potentially used for reconstructive procedures of HNC cartilage defects.

Advances in the Development of Auricular Cartilage Bioimplants

Conditions such as congenital abnormalities, cancer, infections, and trauma can severely impact the integrity of the auricular cartilage, resulting in the need for a replacement structure. Current implants, carved from the patient's rib, involve multiple surgeries and carry risks of adverse events such as contamination, rejection, and reabsorption. Tissue engineering aims to develop lifelong auricular bioimplants using different methods, different cell types, growth factors and maintenance media formulations, and scaffolding materials compatible with the host. This review aims to examine the progress in auricular bioengineering, focusing on improvements derived from in vivo models and clinical trials, as well as the author's suggestions to enhance the methods. For this scope review, 30 articles were retrieved through Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, plus 6 manually selected articles. The methods reported in the articles were categorized into four levels according to the development phases: source of cells, cell media supplementation, scaffold, or scaffold-free methods, and experimental in vivo or clinical approaches. Many methods have demonstrated potential for the development of bioimplants; four clinical trials reported a structure like the external ear that could be maintained after overcoming post-transplant inflammation. However, several challenges must be solved, such as obtaining a structure that accurately replicates the shape and size of the patient's healthy contralateral auricle and improvements to avoid immunological rejection and resorption of the bioimplant.

Craniofacial chondrogenesis in organoids from human stem cell-derived neural crest cells

Knowledge of cell signaling pathways that drive human neural crest differentiation into craniofacial chondrocytes is incomplete, yet essential for using stem cells to regenerate craniomaxillofacial structures. To accelerate translational progress, we developed a differentiation protocol that generated self-organizing craniofacial cartilage organoids from human embryonic stem cell-derived neural crest stem cells. Histological staining of cartilage organoids revealed tissue architecture and staining typical of elastic cartilage. Protein and post-translational modification (PTM) mass spectrometry and snRNA-seq data showed that chondrocyte organoids expressed robust levels of cartilage extracellular matrix (ECM) components: many collagens, aggrecan, perlecan, proteoglycans, and elastic fibers. We identified two populations of chondroprogenitor cells, mesenchyme cells and nascent chondrocytes, and the growth factors involved in paracrine signaling between them. We show that ECM components secreted by chondrocytes not only create a structurally resilient matrix that defines cartilage, but also play a pivotal autocrine cell signaling role in determining chondrocyte fate.

1064nm Nd:YAG laser promotes chondrocytes regeneration and cartilage reshaping by upregulating local estrogen levels

Cartilage is frequently used as a scaffolds for repairing and reconstructing body surface organs. However, after successful plastic surgery, transplanted cartilage scaffolds often exhibit deformation and absorption over time. To enhance the shaping stability of cartilage scaffolds and improve patients' satisfaction after reconstructions, we employed the ear folding models in New Zealand rabbits to confirm whether the 1064nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser could promote cartilage reshaping. There was an increase in collagen and aromatase (Cyp19) expression within the ear cartilage after laser treatment. Moreover, we have found that the Cyp19 inhibitor can inhibit the laser's effect on cartilage shaping and reduce collagen and Cyp19 expression. The overall findings suggest that treatment with 1064nm Nd:YAG laser irradiation can enhance estrogen levels in local cartilage tissues by upregulating Cyp19 expression in chondrocytes through photobiomodulation, thereby promoting the proliferation and collagen secretion of chondrocytes to improve cartilage reshaping and stability.

Suitability of Ex Vivo-Expanded Microtic Perichondrocytes for Auricular Reconstruction

Tissue engineering (TE) techniques offer solutions for tissue regeneration but require large quantities of cells. For microtia patients, TE methods represent a unique opportunity for therapies with low donor-site morbidity and reliance on the surgeon's individual expertise. Microtia-derived chondrocytes and perichondrocytes are considered a valuable cell source for autologous reconstruction of the pinna. The aim of this study was to investigate the suitability of perichondrocytes from microtia patients for autologous reconstruction in comparison to healthy perichondrocytes and microtia chondrocytes. Perichondrocytes were isolated via two different methods: explant culture and enzymatic digestion. The isolated cells were analyzed in vitro for their chondrogenic cell properties. We examined migration activity, colony-forming ability, expression of mesenchymal stem cell markers, and gene expression profile. We found that microtic perichondrocytes exhibit similar chondrogenic properties compared to chondrocytes in vitro. We investigated the behavior in three-dimensional cell cultures (spheroids and scaffold-based 3D cell cultures) and assessed the expression of cartilage-specific proteins via immunohistochemistry, e.g., collagen II, which was detected in all samples. Our results show that perichondrocytes from microtia patients are comparable to healthy perichondrocytes and chondrocytes in terms of chondrogenic cell properties and could therefore be a promising cell source for auricular reconstruction.

Extracellular Vesicles Derived from Auricular Chondrocytes Facilitate Cartilage Differentiation of Adipose-Derived Mesenchymal Stem Cells

PURPOSE

Adipose-derived mesenchymal stem cell (ADSC)-based therapies have been utilized for cartilage regeneration because of their multi-lineage differentiation ability. However, commonly used cartilage inducers such as the transforming growth factor beta-3 (TGF-β3) may be prone to cartilage dedifferentiation and hypertrophy. The directional differentiation of elastic cartilage is limited nowadays. Extracellular vesicles (EVs) have been reported to influence the specific differentiation of mesenchymal stem cells (MSCs) by reflecting the composition of the parental cells. However, the role of auricular chondrogenic-derived EVs (AC-EVs) in elastic chondrogenic differentiation of ADSCs has not yet been reported.

RESULTS

AC-EVs isolated from the external ears of swine exhibited a positive effect on cell proliferation and migration. Furthermore, AC-EVs efficiently promoted chondrogenic differentiation of ADSCs in pellet culture, as shown by the elevated levels of COL2A1, ACAN, and SOX-9 expression. Moreover, there was a significantly higher expression of elastin and a lower expression of the fibrotic marker COL1A1 in comparison with that achieved with TGF-β3. The staining results demonstrated that AC-EVs promoted the deposition of cartilage-specific matrix, which is in good concordance with the real-time polymerase chain reaction (RT-PCR) results.

CONCLUSIONS

Auricular chondrogenic-derived EVs are a crucial component in elastic chondrogenic differentiation and other biological behaviors of ADSCs, which may be a useful ingredient for cartilage tissue engineering and external ear reconstruction.

NO LEVEL ASSIGNED

This journal requires that authors 42 assign a level of evidence to each submission to which 43 Evidence-Based Medicine rankings are applicable. This 44 excludes Review Articles, Book Reviews, and manuscripts 45 that concern Basic Science, Animal Studies, Cadaver 46 Studies, and Experimental Studies. For a full description of 47 these Evidence-Based Medicine ratings, please refer to the 48 Table oôf Contents or the online Instructions to Authors 49 www.springer.com/00266 .

The application and progress of stem cells in auricular cartilage regeneration: a systematic review

Background: The treatment of microtia or acquired ear deformities by surgery is a significant challenge for plastic and ENT surgeons; one of the most difficult points is constructing the scaffold for auricular reconstruction. As a type of cell with multiple differentiation potentials, stem cells play an essential role in the construction of cartilage scaffolds, and therefore have received widespread attention in ear reconstructive research. Methods: A literature search was conducted for peer-reviewed articles between 2005 and 2023 with the following keywords: stem cells; auricular cartilage; ear cartilage; conchal cartilage; auricular reconstruction, regeneration, and reparation of chondrocytes; tissue engineering in the following databases: PubMed, MEDLINE, Cochrane, and Ovid. Results: Thirty-three research articles were finally selected and their main characteristics were summarized. Adipose-derived stem cells (ADSCs), bone marrow mesenchymal stem cells (BMMSCs), perichondrial stem/progenitor cells (PPCs), and cartilage stem/progenitor cells (CSPCs) were mainly used in chondrocyte regeneration. Injecting the stem cells into the cartilage niche directly, co-culturing the stem cells with the auricular cartilage cells, and inducing the cells in the chondrogenic medium in vitro were the main methods that have been demonstrated in the studies. The chondrogenic ability of these cells was observed in vitro, and they also maintained good elasticity and morphology after implantation in vivo for a period of time. Conclusion: ADSC, BMMSC, PPC, and CSPC were the main stem cells that have been researched in craniofacial cartilage reconstruction, the regenerative cartilage performed highly similar to normal cartilage, and the test of AGA and type II collagen content also proved the cartilage property of the neo-cartilage. However, stem cell reconstruction of the auricle is still in the initial stage of animal experiments, transplantation with such scaffolds in large animals is still lacking, and there is still a long way to go.