BackgroundBased on evidence from several other tissues, cartilage stem/progenitor cells in the auricular cartilage presumably contribute to tissue development or homeostasis of the auricle. However, no definitive studies have identified or characterized a stem/progenitor population in mice auricle.Methodology/Principal FindingsThe 5-bromo-2′-deoxyuridine (BrdU) label-retaining technique was used to label dividing cells in fetal mice. Observations one year following the labeling revealed that label-retaining cells (LRCs) were present specifically in auricular perichondrium at a rate of 0.08±0.06%, but LRCs were not present in chondrium. Furthermore, LRCs were successfully isolated and cultivated from auricular cartilage. Immunocytochemical analyses showed that LRCs express CD44 and integrin-α5. These LRCs, putative stem/progenitor cells, possess clonogenicity and chondrogenic capability in vitro.Conclusions/SignificanceWe have identified a population of putative cartilage stem/progenitor cells in the auricular perichondrium of mice. Further characterization and utilization of the cell population should improve our understanding of basic cartilage biology and lead to advances in cartilage tissue engineering and novel therapeutic strategies for patients with craniofacial defects, including long-term tissue restoration.

Although further study is required to determine factors leading to anastomotic obstruction and to optimize the results of microlymphatic surgery, the present LVSEA technique appears promising.

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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.

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Genetically engineered mice (GEM) are the gold standard for cancer modeling. However, strict recapitulation of stepwise carcinogenesis from a single tumor-initiating epithelial cell among genetically intact cells in adults is not feasible with the currently available techniques using GEM. In previous studies, we partially overcame this challenge by physically isolating organs from adult animals, followed by genetic engineering in organoids and subcutaneous inoculation in nude mice. Despite the establishment of suitable ex vivo carcinogenesis models for diverse tissues, tumor development remained ectopic and occurred under immunodeficient conditions. Further refinement was, therefore, necessary to establish ideal models. Given the poor prognosis and few models owing to the lack of gall bladder (GB)-specific Cre strain, we assumed that the development of authentic models would considerably benefit GB cancer research. Here, we established a novel model using GB organoids with mutant Kras and Trp53 loss generated in vitro by lentiviral Cre transduction and CRISPR/Cas9 gene editing, respectively. Organoid-derived subcutaneous tumor fragments were sutured to the outer surface of the GB in syngeneic mice, which developed orthotopic tumors that resembled human GB cancer in histological and transcriptional features. This model revealed the infiltration of similar subsets of immune cells in both subcutaneous and orthotopic tumors, confirming the appropriate immune environment during carcinogenesis. In addition, we accurately validated the in vivo efficacy of gemcitabine, a common therapeutic agent for GB cancer, in large cohorts. Taken together, this model may serve as a promising avatar of patients with GB cancer in drug discovery and precision medicine.

In healthy joints, hyaline cartilage covering the joint surfaces of bones provides cushioning due to its unique mechanical properties. However, because of its limited regenerative capacity, age-and sports-related injuries to this tissue may lead to degenerative arthropathies, prompting researchers to investigate a variety of cell sources. We recently succeeded in isolating human cartilage progenitor cells from ear elastic cartilage. Human cartilage progenitor cells have high chondrogenic and proliferative potential to form elastic cartilage with long-term tissue maintenance. However, it is unknown whether ear-derived cartilage progenitor cells can be used to reconstruct hyaline cartilage, which has different mechanical and histological properties from elastic cartilage. In our efforts to develop foundational technologies for joint hyaline cartilage repair and reconstruction, we conducted this study to obtain an answer to this question. We created an experimental canine model of knee joint cartilage damage, transplanted ear-derived autologous cartilage progenitor cells. The reconstructed cartilage was rich in proteoglycans and showed unique histological characteristics similar to joint hyaline cartilage. In addition, mechanical properties of the reconstructed tissues were higher than those of ear cartilage and equal to those of joint hyaline cartilage. This study suggested that joint hyaline cartilage was reconstructed from ear-derived cartilage progenitor cells. It also demonstrated that ear-derived cartilage progenitor cells, which can be harvested by a minimally invasive method, would be useful for reconstructing joint hyaline cartilage in patients with degenerative arthropathies. STEM CELLS 2014;32:816-821

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