Rat tracheal cartilage regeneration using mesenchymal stem cells derived from human iPS cells.

Tracheal cartilage provides structural support to the airways to enable breathing. However, it can become damaged or impaired, sometimes requiring surgical resection and reconstruction. Previously, we clinically applied an artificial trachea composed of a polypropylene mesh and collagen sponge, with a favorable postoperative course. However, the artificial trachea presents a limitation, as the mesh is not biodegradable and cannot be used in pediatric patients. Compared to a polypropylene mesh, regenerated cartilage represents an ideal material for reconstruction of the damaged trachea. The use of mesenchymal stem cells (MSCs) as a source for cartilage regeneration has gained widespread acceptance, but challenges such as the invasiveness of harvesting and limited cell supply, persist. Therefore, we focused on the potential of human induced pluripotent stem cell (hiPSC)-derived mesenchymal stem cells (iMSCs) for tracheal cartilage regeneration. In this study, we aimed to regenerate tracheal cartilage on an artificial trachea as a preliminary step to replace the polypropylene mesh. iMSCs were induced from hiPSCs through neural crest cells and transplanted with a polypropylene mesh covered with a collagen sponge into the damaged tracheal cartilage in immunodeficient rats. Human nuclear antigen (HNA)-positive cells were observed in all six rats at 4 weeks and in six out of seven rats at 12 weeks after transplantation, indicating that transplanted iMSCs survived within the tracheal cartilage defects of rats. The HNA-positive cells co-expressed SOX9, and type II collagen was detected around HNA-positive cells in four of six rats at 4 weeks and in three of seven rats at 12 weeks after transplantation, reflecting cartilage-like tissue regeneration. These results indicate that the transplanted iMSCs could differentiate into chondrogenic cells and promote tracheal cartilage regeneration. iMSC transplantation thus represents a promising approach for human tracheal reconstruction.

An Infection Model for SARS-CoV-2 Using Rat Transplanted with hiPSC-Airway Epithelial Cells.

Investigating the infection mechanism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the airway epithelium and developing effective defense strategies against infection are important. To achieve this, establishing appropriate infection models is crucial. Therefore, various in vitro models, such as cell lines and primary cultures, and in vivo models involving animals that exhibit SARS-CoV-2 infection and genetically humanized animals have been used as animal models. However, no animal model has been established that allows infection experiments with human cells under the physiological environment of airway epithelia. Therefore, we aimed to establish a novel animal model that enables infection experiments using human cells. Human induced pluripotent stem cell-derived airway epithelial cell-transplanted nude rats (hiPSC-AEC rats) were used, and infection studies were performed by spraying lentiviral pseudoviruses containing SARS-CoV-2 spike protein and the GFP gene on the tracheae. After infection, immunohistochemical analyses revealed the existence of GFP-positive-infected transplanted cells in the epithelial and submucosal layers. In this study, a SARS-CoV-2 infection animal model including human cells was established mimicking infection through respiration, and we demonstrated that the hiPSC-AEC rat could be used as an animal model for basic research and the development of therapeutic methods for human-specific respiratory infectious diseases.

Modified method for tracheoesophageal fistula closure in intractable cases.

OBJECTIVE: Tracheoesophageal puncture (TEP) is one of the most established methods for voice reacquisition following total laryngectomy. The most difficult complication following TEP is the management of saliva leakage or secretion into the trachea due to TE fistula enlargement. In this study, we devised a new strategy to close TE fistulas and confirmed its safety and effectiveness. METHODS: Skin incision: If the tracheal mucosa around the voice prosthesis appears intact and normal, an arcuate incision, from 10 to 2 o'clock, is made on the skin 5 mm superior to the edge of the stoma. However, if the surrounding tracheal mucosa is fragile because of leaking, the incision is made on the superior edge of the stoma, with later reconstruction of the posterior tracheal wall. Separation of the trachea and esophagus: If the esophagotracheal spatium appears normal and is easy to dissect, the connective pipes can be found easily. After cutting the pipe, a ligature alone is sufficient for the tracheal side; however, the esophageal wall is closed with Gambee sutures. If the esophagotracheal spatium is compromised and the posterior tracheal wall is fragile (due to saliva leakage), we remove the posterior wall and reconstruct the area using the superior skin flap. We performed our novel method on four patients with intractable conditions; postradiotherapy for laryngeal cancer, total pharyngo-laryngo-esophagectomy (TPLE) with jejunum reconstruction, TPLE with gastric lifting reconstruction, and in a patient who underwent cervicothoracic incisional drainage for descending necrotizing mediastinitis. RESULTS: None of the cases showed postoperative leakage from the fistula, and oral intake was resumed without difficulty. CONCLUSION: This study showed that this strategy based on TE fistula conditions is effective even in difficult-to-treat cases.

Phonosurgery training using Japanese deer larynx.

OBJECTIVE: To develop phonosurgery skills, surgical training of the actual larynx is essential. In our institution, the Japanese deer (Cervus Nippon aplodontids) larynx is used in phonosurgery training. This study aimed to examine the similarities and differences between the Japanese deer and human larynx and to demonstrate their utility in vocal surgery practice. METHODS: A comparative study was conducted using 30 Japanese deer larynges and 51 human donor larynges, evaluating the overall framework, dimensions, and angle of the thyroid cartilage, vocal cord length, and location of the arytenoid cartilage muscular process. The changes and movements of the vocal folds during contraction and relaxation of each internal laryngeal muscle were also visually analyzed. RESULTS: The larynx size of Japanese deer is intermediate between that of human males and females. The adduction and abduction of the vocal folds induced by contraction of the posterior and lateral cricoarytenoid muscles, as well as the extension of the vocal folds induced by contraction of the cricothyroid muscle, behaved in the same manner as in the human larynx. CONCLUSION: The morphology of the Japanese deer larynx is similar to that of the human larynx, making it suitable for use in dissection and surgical practice. Owing to the recent animal damage problem and the popularity of gibier cuisine, large quantities of Japanese deer larynx are available at low prices. We believe that the Japanese deer larynx is the most appropriate animal for phonosurgery training so far.

Outcomes of laryngeal framework surgeries for unilateral vocal cord paralysis in the elderly patients.

OBJECTIVE: Laryngeal framework surgery is a widely accepted treatment for unilateral vocal fold paralysis with good functional outcomes. Recently, with the aging of the population, opportunities to perform this procedure in elderly patients have increased; however, the safety and efficacy of this procedure in elderly patients has not been established. Therefore, this study aimed to investigate the safety and functional outcomes of laryngeal framework surgery in elderly patients. METHODS: Between January 2008 and December 2017, 97 patients with unilateral vocal fold paralysis underwent laryngeal framework surgery, and 71 among them completed pre- and post-operative voice function evaluations. The clinical course of these 71 patients were retrospectively reviewed. RESULTS: Out of 71 patients, 35 were assigned to the younger group (< 65 years) and 36 to the elderly group (≥ 65 years). Complications included post-operative edema and submucosal hematoma that were safely managed in all cases, and no differences were identified between the groups. Significant improvements were observed in maximum phonation time (MPT), mean flow rate, alternating current/direct current ratio, pitch perturbation quotient, amplitude perturbation quotient, and noise-to-harmonic ratio in both groups, and multivariate analysis of variance revealed greater improvement in the younger group in MPT. CONCLUSION: Laryngeal framework surgeries for unilateral vocal fold paralysis are safe and effective, regardless of age. Better improvement was observed in the younger group in the MPT suggesting that the effects of laryngeal framework surgeries is more likely to be present in the younger group than in the elderly.

Complications including dysphagia following transoral non-robotic surgery for pharyngeal and laryngeal squamous cell carcinoma: A retrospective multicenter study.

OBJECTIVE: Transoral surgery is a minimally invasive treatment but may cause severe dysphagia at a lower rate than chemoradiotherapy. METHODS: We compared clinical information, surgical complications, and swallowing function in patients who underwent transoral nonrobotic surgery for laryngo-pharyngeal squamous cell carcinoma between 2015 and 2021 in a multicenter retrospective study. RESULTS: Six hundred and forty patients were included. Postoperative bleeding was observed in 20 cases (3.1%), and the risk factor was advanced T category. Postoperative laryngeal edema was observed in 13 cases (2.0%), and the risk factors were prior radiotherapy, advanced T stage, and concurrent neck dissection in patients with resected HPC. Dysphagia requiring nutritional support was observed in 29 cases (4.5%) at 1 month postoperatively and in 19 cases (3.0%) at 1 year postoperatively, respectively. The risk factors for long-term dysphagia were prior radiotherapy and advanced T category. Short-term risk factors for dysphagia were prior radiotherapy, advanced T category, and concurrent neck dissection, while long-term risk factors for dysphagia were only prior radiotherapy and advanced T category. CONCLUSION: Prior radiotherapy, advanced T stage, and concurrent neck dissection increased the incidence of postoperative laryngeal edema and short-term dysphagia, but concurrent neck dissection did not affect long-term dysphagia. Such features should be considered when considering the indication for transoral surgery and postoperative management.

Anatomical variations in the superficial venous system of the neck: an image-based study using contrast-enhanced computed tomography.

PURPOSE: The superficial venous system (SVS) of the neck receives blood from the face and oral cavity. The SVS comprises the anterior jugular vein (AJV), external jugular vein (EJV), and facial vein (FV). Comprehensive knowledge of the normal anatomy and potential variations in the venous system is valuable in surgical and radiological procedures. This study aimed to update the anatomic knowledge of the SVS using a radiographic approach, which is a beneficial data source in clinical practice. METHODS: Contrast-enhanced computed tomography images of the neck of patients with head and neck cancer treated between 2017 and 2020 were retrospectively evaluated. Each side of the neck was counted separately. A total of 302 necks of 151 patients were enrolled in this study. RESULTS: The medial AJV was absent in 49.7% (75/151) of the patients on the left side, which was significantly greater than the 19.2% (29/151) on the right (p < 0.001). The left AJV drained into the right venous system in 6.6% (10/151) of the necks. In 48.3% (146/302) of the necks, the FV did not flow into the internal jugular vein but rather into the EJV or AJV; these findings were significantly more frequent than those reported in previous studies. The diameters of the veins were significantly larger when they received blood from the FV than when they were not connected to the FV. CONCLUSION: These findings indicate that the AJV has a rightward preference during its course. The course of the FV is diverse and affects the diameter of connected veins.

Thyroid Lobectomy Under Local Anesthesia Before Lung Transplantation Owing to Diffuse Panbronchiolitis: A Case Report.

We herein report a case of thyroid lobectomy performed under local anesthesia for thyroid cancer in a patient who was at a high risk for general anesthesia due to diffuse panbronchiolitis. Although thyroid surgery has been performed in the past under local anesthesia in low-risk patients, thyroid surgery is now rarely performed under local anesthesia. If they are performed, thyroid surgery under local anesthesia is usually performed under monitored anesthesia care; sedation is considered safe and does not cause discomfort to patients. The present patient's respiratory function was poor, raising concerns that once intubated, extubation may not be possible because of the potential deterioration of respiratory function caused by the suppression of spontaneous breathing. Therefore, sedatives were avoided to maintain spontaneous breathing as much as possible. In such high-risk patients, additional care is required to ensure that the procedure is completed with minimal discomfort from pain or dyspnea. Maintaining a slightly upright position and raising the anesthesia screen are necessary to ensure a large space in front of the patient's face. In addition, an appropriate skin incision should be made to obtain a wide field of vision, and local anesthetic injections should be administered frequently to preemptively counter pain. Atropine sulfate was administered to reduce salivation and swallowing. Energy devices effectively reduced blood loss and operative time. Controlling intraoperative pain and bleeding is important, and the methods and techniques are also beneficial in surgery under general anesthesia.

Changes in the Proportion of Each Cell Type After hiPSC-Derived Airway Epithelia Transplantation.

No radical treatment is available for the regeneration of dysfunction and defects in airway epithelia. Artificial tracheae made of polypropylene and collagen sponge were used in clinical studies to reconstitute tracheae after resection. For early epithelialization of the luminal surface of the artificial trachea, a model was established, that is, an artificial trachea covered with human-induced pluripotent stem cell-derived airway epithelial cells (hiPSC-AECs) was transplanted into a tracheal defect in an immunodeficient rat. Unlike the cell types of hiPSC-derived cells that are currently used in clinical studies, AECs maintain tissues by proliferation and differentiation of basal cells into various cell types that constitute AECs constantly. Therefore, post-transplantation, the proportion of each cell type, such as ciliated and goblet cells, may change; however, no studies have examined this possibility. In this study, using our hiPSC-AEC-transplanted rat model, we investigated changes in the proportion of each cell type in hiPSC-AECs pre-transplantation and post-transplantation. As a result, the proportion of each cell type changed post-transplantation. The proportion of ciliated, basal, and club cells increased, and the proportion of goblet cells decreased post-transplantation. In addition, the proportion of each cell type in engrafted hiPSC-AECs is more similar to the proportion of each cell type in normal proximal airway tissue than the proportion of each cell type pre-transplantation. The results of this study are useful for the development of therapeutic techniques using hiPSC-AEC transplantation.

Expression of FOXI1 and POU2F3 varies among different salivary gland neoplasms and is higher in Warthin tumor.

PURPOSE: Salivary gland tumors are histologically diverse. Ionocytes and tuft cells, rare epithelial cells found in normal salivary glands, might be associated with salivary tumors. Here, we explored the expression of FOXI1 and POU2F3, master regulators of ionocytes and tuft cells, respectively, for common salivary neoplasms using immunohistochemistry. METHODS: We analyzed normal salivary tissues and nine salivary gland tumors; Warthin tumors (WT), pleomorphic adenomas (PA), basal cell adenomas, and oncocytomas were benign, whereas mucoepidermoid, adenoid cystic, acinic cell, salivary duct carcinomas, and polymorphous adenocarcinomas were malignant. RESULTS: Normal salivary glands contained a few FOXI1- and POU2F3-positive cells in the ducts instead of the acini, consistent with ionocytes and tuft cells, respectively. Among the benign tumors, only WTs and PAs consistently expressed FOXI1 (10/10 and 9/10, respectively). The median H-score of WTs was significantly higher than that of PAs (17.5 vs. 4, P = 0.01). While WTs and PAs harbored POU2F3-positive cells (10/10 and 9/10, respectively), the median H-score was higher in WTs than in PAs (10.5 vs 4, respectively). Furthermore, WTs exhibited a unique staining pattern of FOXI1- and POU2F3-positive cells, which were present in luminal and abluminal locations, respectively. Whereas none of the malignant tumors expressed FOXI1, only adenoid cystic carcinoma consistently expressed POU2F3 (5/5), with a median H-score of 4. CONCLUSION: The expression patterns of the characteristic transcription factors found in ionocytes and tuft cells vary among salivary gland tumor types and are higher in WT, which might be relevant for understanding and diagnosing salivary gland neoplasms.

Mucosal melanoma of the head and neck: a retrospective analysis of 34 cases in Japan.

PURPOSE: Mucosal melanoma of the head and neck (MMHN) is a rare condition. This study aimed to investigate oncological outcomes of surgical intervention in patients with MMHN. MATERIALS AND METHODS: The study included 34 patients with MMHN who underwent surgical resection as initial treatment at 10 institutions in Japan between July 2005 and June 2015. Results: The 5-year overall survival (OS), local control rate (LCR), disease-free survival (DFS), and disease-specific survival (DSS) rates were 48.7%, 53.4%, 32.4%, and 55.1%, respectively. Based on multivariate analysis, no independent prognostic factors for the 5-year OS and DSS were found. Based on univariate analysis, the 5-year LCR was worse in patients with lesions in the nasal cavity and paranasal sinuses than in the oral cavity and pharynx. However, no differences in oncological outcomes were identified in relation to primary sites, and postoperative radiotherapy (PORT) and adjuvant systemic therapy did not contribute to improvements in the 5-year OS. CONCLUSIONS: No independent prognostic factors for the 5-year OS or DSS were identified. Regional or distant recurrences are often identified, regardless of local control with surgical resection. Difficult control of MMHN with conventional therapeutic strategies, such as surgical intervention, PORT, and systemic therapy, has been suggested.

Impact of cervical lymph node metastasis on transoral surgery for hypopharyngeal squamous cell carcinoma: A retrospective multicenter study.

BACKGROUND: Hypopharyngeal carcinoma is likely to spread to the lymph nodes, but there is no established strategy for management in transoral surgery. METHODS: We compared oncologic and functional outcomes in a retrospective multicenter study of patients who underwent transoral surgery for hypopharyngeal carcinoma between 2015 and 2021. RESULTS: Two-hundred and thirty-two patients were included. Comparing patients with and without adjuvant radiotherapy, 3-year regional recurrence-free survival (RRFS) was not significantly different in pN2b and pN2c, but was significantly worse in pN3b without adjuvant radiotherapy. In patients without neck dissection, the 3-year RRFS was 85.6%, 76.8%, and 70.0% for T1, T2, and T3 primary lesions, respectively, and was significantly worse for T2 or higher (p = 0.035). CONCLUSIONS: In the absence of extracapsular invasion, regional control did not deteriorate without adjuvant therapy. If prophylactic neck dissection is not performed, careful follow-up is necessary if the primary lesion is T2 or greater.

The Effect of Noise on Deep Learning for Classification of Pathological Voice.

OBJECTIVE: This study aimed to evaluate the significance of background noise in machine learning models assessing the GRBAS scale for voice disorders. METHODS: A dataset of 1406 voice samples was collected from retrospective data, and a 5-layer 1D convolutional neural network (CNN) model was constructed using TensorFlow. The dataset was divided into training, validation, and test data. Gaussian noise was added to test samples at various intensities to assess the model's noise resilience. The model's performance was evaluated using accuracy, F1 score, and quadratic weighted Cohen's kappa score. RESULTS: The model's performance on the GRBAS scale generally declined with increasing noise intensities. For the G scale, accuracy dropped from 70.9% (original) to 8.5% (at the highest noise), F1 score from 69.2% to 1.3%, and Cohen's kappa from 0.679 to 0.0. Similar declines were observed for the remaining RBAS components. CONCLUSION: The model's performance was affected by background noise, with substantial decreases in evaluation metrics as noise levels intensified. Future research should explore noise-tolerant techniques, such as data augmentation, to improve the model's noise resilience in real-world settings. LEVEL OF EVIDENCE: This study evaluates a machine learning model using a single dataset without comparative controls. Given its non-comparative design and specific focus, it aligns with Level 4 evidence (Case-series) under the 2011 OCEBM guidelines Laryngoscope, 134:3537-3541, 2024.

Comparative Study of Immunodeficient Rat Strains in Engraftment of Human-Induced Pluripotent Stem Cell-Derived Airway Epithelia.

The airway epithelia (AE) play a role in the clearance of foreign substances through ciliary motility and mucus secreted. We developed an artificial trachea that is made of collagen sponges and polypropylene mesh for the regeneration of the tracheal defect, and it was used for a clinical study. Then, a model in which the luminal surface of an artificial trachea was covered with a human-induced pluripotent stem cell-derived AE (hiPSC-AE) was transplanted into the tracheal defect of nude rats to promote epithelialization. In the future, this model was expected to be applied to research on infectious diseases and drug discovery as a trachea-humanized rat model. However, at present, sufficient engraftment has not been achieved to evaluate functional recovery in transplanted cells. Therefore, this study focused on immunosuppression in recipient rats. Nude rats lack T cell function and are widely used for transplantation experiments; however, more severe immunosuppressed recipients are preferred for xenotransplantation. Several strains of immunodeficient rats were created as rats that exhibit more severe immunodeficiency until now. In this study, to establish a trachea-humanized rat model in which human AE function can be analyzed to improve engraftment efficiency, engraftment efficiency in nude rats and X-linked severe combined immunodeficiency (X-SCID) rats following hiPSC-AE transplantation was compared. In the analysis of the proportion of engrafted cells in total cells at the graft site, the engraftment efficiency of epithelial cells tended to be high in X-SCID rats, although no statistical difference was found between the two groups, whereas the engraftment efficiency of mesenchymal cells was higher in X-SCID rats. Furthermore, the number of immune cells that accumulated in the grafts showed that a pan T cell marker, that is, CD3-positive cells, did not differ between the two strains; however, CD45-positive cells and major histocompatibility complex (MHC) class II-positive cells significantly decreased in X-SCID rats. These results indicate that X-SCID rats are more useful for the transplantation of hiPSC-AE into the tracheae to generate trachea-humanized rat models.

Local recurrence and metachronous multiple cancers after transoral nonrobotic surgery for pharyngeal and laryngeal squamous cell carcinoma: A retrospective multicenter study.

BACKGROUND: Late laryngopharyngeal cancers after transoral surgery include not only local recurrences but also metachronous multiple cancers. METHODS: We compared clinical information, surgical outcomes, and late laryngopharyngeal cancers in patients who underwent transoral nonrobotic surgery for laryngopharyngeal squamous cell carcinoma without lymph node metastases between 2015 and 2021 in a multicenter retrospective study. RESULTS: Four hundred and fifty-seven patients were included. Positive surgical margins were found in 121 patients (26.5%). Twenty-two patients (4.8%) received additional treatment. Positive horizontal margins of invasive carcinoma (p = 0.003) and positive horizontal margins of carcinoma in situ only (p = 0.032) were independent risk factors for local recurrence, and prior radiotherapy (p = 0.001) for metachronous multiple cancers. Local control was significantly worse without additional treatment (p = 0.049), but there was no significant difference in survival. CONCLUSIONS: Patients with positive margins had an increased frequency of local recurrence, but salvage therapy was effective.

The combination of soluble forms of PD-1 and PD-L1 as a predictive marker of PD-1 blockade in patients with advanced cancers: a multicenter retrospective study.

Introduction: The clinical relevance of soluble forms of programmed cell death-1 (sPD-1) and programmed cell death-ligand 1 (sPD-L1) remains unclear. We here investigated the relation between the efficacy of PD-1 blockade and pretreatment plasma levels of sPD-1 and sPD-L1 across a broad range of cancer types. Methods: We retrospectively analyzed clinical data from 171 patients with advanced solid tumors who received nivolumab or pembrolizumab monotherapy regardless of treatment line. The concentrations of sPD-1 and sPD-L1 were measured with a fully automated immunoassay (HISCL system). Results: The study subjects comprised patients with head and neck cancer (n = 50), urothelial cancer (n = 42), renal cell cancer (n = 37), gastric cancer (n = 20), esophageal cancer (n = 10), malignant pleural mesothelioma (n = 6), or microsatellite instability-high tumors (n = 6). High or low levels of sPD-1 or sPD-L1 were not significantly associated with progression-free survival (PFS) or overall survival (OS) for PD-1 blockade in the entire study population. Comparison of treatment outcomes according to combinations of high or low sPD-1 and sPD-L1 levels, however, revealed that patients with low sPD-1 and high sPD-L1 concentrations had a significantly poorer PFS (HR of 1.79 [95% CI, 1.13-2.83], p = 0.01) and a tendency toward poorer OS (HR of 1.70 [95% CI, 0.99-2.91], p = 0.05) compared with all other patients. Conclusion: Our findings suggest that the combination of low sPD-1 and high sPD-L1 levels is a potential negative biomarker for PD-1 blockade therapy.

Parathyroid carcinoma: impact of preoperative diagnosis on the choice of surgical procedure.

The operative procedure in the surgical treatment of parathyroid carcinoma differs from that of benign hyperparathyroidism. However, preoperative differentiation is often difficult. This study elucidated how clinicians diagnose parathyroid carcinoma and the relationship between preoperative diagnosis and the operative course. Using a retrospective chart review, twenty cases of parathyroid carcinoma from nine participating centers were examined. In 11 cases with preoperative suspicion of malignancy, at least one of these three features was found: elevated serum calcium level (>14 mg/dL), palpable mass, and irregular margin on ultrasonography. Although an intact parathyroid hormone (iPTH) threshold to suspect malignancy has not been established, six cases showed marked iPTH elevation exceeding 8.0 times the upper limit of normal. One case was excluded from analysis due to hemodialysis. Compared with the four cases that showed calcium elevation, the iPTH threshold might represent better sensitivity. Among 9 cases of benign preoperative diagnosis, six cases were performed with pericapsular resection. In three cases where malignancy was suspected in the middle of the operation, the recommended en bloc resection with ipsilateral thyroid lobectomy was not performed but a parathyroidectomy with surrounding soft tissue. In contrast, 10 preoperatively suspected cases underwent en bloc resection, and one case underwent pericapsular resection followed by supplementary ipsilateral hemithyroidectomy due to the uncertain pre- and intraoperative findings to determine the diagnosis. In conclusion, the surgical procedure for parathyroid carcinoma strongly depends on the preoperative diagnosis. The presence of excessive iPTH levels might contribute to improved preoperative diagnostic sensitivity for parathyroid carcinoma.

Local coordination of epithelial planar polarity in the maintenance and regeneration of the adult rat airway.

The maintenance of planar polarity in airway multiciliated cells (MCCs) has been poorly characterized. We recently reported that the direction of ciliary beating in a surgically inverted tracheal segment remained inverted beyond the time required for the turnover of cells, without adjustment to global distal-to-proximal polarity. We hypothesized that the local maintenance of tissue-level polarity occurs via locally reproduced cells. To provide further insight regarding this hypothetical property, we performed allotransplantation of an inverted tracheal segment between wild-type (donor) and tdTomato-expressing (host) rats, with and without scratching the mucosa of the transplants. The origin of cells in the transplants was assessed using tdTomato-specific immunostaining. Ciliary movement and structures were observed by high-speed video and electron microscopy to analyze MCC orientations. Variabilities in the orientations of closely and distantly located MCCs were analyzed to evaluate the local- and broad-scale coordination of polarity, respectively. The epithelium was maintained by donor-derived cells in the non-scratched inverted transplant over 6 months, beyond one cycle of turnover. The inverted orientation of MCCs was also maintained throughout the non-scratched transplant. MCCs regenerated in the scratched transplant were derived from the host and exhibited diverse orientations across the transplant. However, the orientations of adjacent regenerated MCCs were often coordinated, indicating that airway MCCs can locally coordinate their orientations. A steady-state airway may maintain MCC orientation by locally reproducing MCCs via the local coordination of polarity. This local coordination enables the formation and maintenance of tissue-level polarity in small regions after mucosal injury.

Laryngeal Cartilage Regeneration of Nude Rats by Transplantation of Mesenchymal Stem Cells Derived from Human-Induced Pluripotent Stem Cells.

Previous studies transplanted human-induced pluripotent stem cells (hiPSCs)-derived mesenchymal stem cells (iMSCs) into thyroid cartilage defect of X-liked severe combined immunodeficiency (X-SCID) rats and confirmed transplanted cell survival and cartilage regeneration. Thus, this study aimed to investigate the contribution of iMSC transplantation to thyroid cartilage regeneration of nude rats. iMSCs were induced from hiPSCs via a neural crest cell lineage. Then, clumps formed from an iMSC/extracellular matrix complex were transplanted into thyroid cartilage defects in nude rats. The larynx was removed and histological and immunohistochemical analyses were performed 4 or 8 weeks after the transplantation. Human nuclear antigen (HNA)-positive cells were observed in 11 of 12 (91.7%) rats, which indicated that transplanted iMSCs survived in thyroid cartilage defects in nude rats. HNA-positive cells co-expressed SOX9, and type II collagen was identified around HNA-positive cells in 8 of 12 rats (66.7%), which indicated cartilage-like regeneration. Cartilage-like regeneration in nude rats in this study was comparable to the previous report on X-SCID rats (HNA-positive cells were observed in all 14 rats and cartilage-like regeneration was observed in 10 of 14 rats). This result suggests that nude rats could be an alternative to X-SCID rats in thyroid cartilage regeneration experiments using iMSCs, and this nude rat cartilage transplantation model may develop cartilage regeneration research concerning fewer problems such as infection due to immunosuppression.