Fabrication of transplantable human oral mucosal epithelial cell sheets using temperature-responsive culture inserts without feeder layer cells

Bioorthogonal targeted cell membrane vesicles/cell-sheet composites reduce postoperative tumor recurrence and scar formation of melanoma

While surgical resection is the predominant clinical strategy in the treatment of melanoma, postoperative recurrence and undetectable metastasis are both pernicious drawbacks to this otherwise highly successful approach. Furthermore, the deep cavities result from tumor excision can leave long lasting wounds which are slow to heal and often leave visible scars. These unmet needs are addressed in the present work through the use of a multidimensional strategy, and also promotes wound healing and scar reduction. In the first phase, cell membrane-derived nanovesicles (NVs) are engineered to show PD-1 and dibenzocyclooctyne (DBCO). These are capable of reactivating T cells by blocking the PD-1/PD-L1 pathway. In the second phase, azido (N3) labeled mesenchymal stem cells (MSCs) are cultured into cell sheets using tissue engineering, then apply directly to surgical wounds to enhance tissue repair. Owing to the complementary association between DBCO and N3 groups, PD-1 NVs were accumulated at the site of excision. This strategy can inhibit postoperative tumor recurrence and metastasis, whilst also promoting wound healing and reducing scar formation. The results of this study set a precedent for a new and innovative multidimensional therapeutic strategy in the postoperative treatment of melanoma.

Immortalised canine buccal epithelial cells' CXCL8 secretion is affected by allergen extracts, Toll-like receptor ligands, IL-17A and calcitriol

Epithelial cells are known to produce mediators which can influence the behaviour of neighbouring immune cells. Although the oral mucosa has gained increased interest as a route to induce allergy desensitisation and mucosal pathogen immunisation in dogs, there is only limited knowledge on the factors which impact mediator secretion by canine oral epithelial cells. The study’s objective was to enlarge the knowledge on the stimuli that can influence the secretion of some pro- and anti-inflammatory cytokines and the chemokine CXCL8 by canine buccal epithelial cells. To investigate this, buccal epithelial cells were isolated from a biopsy of a dog and immortalised by lentiviral transduction of the SV40 large T antigen. The cells were stained with a CD49f and cytokeratin 3 antibody to confirm their epithelial origin. Cells were incubated with allergen extracts, Toll-like receptor ligands (TLRL), recombinant cytokines and vitamin A and D metabolites. Subsequently, the secretion of the cytokines interleukin (IL)-4, IL-6, IL-10, IL-17A, IFN-γ, TGF-β1 and the chemokine CXCL8 was assayed by ELISA. Immortalised canine buccal epithelial cells stained positive for CD49f but not for cytokeratin 3. The cells produced detectable amounts of CXCL8 and TGF-β1. A Dermatophagoides farinae extract, an Alternaria alternata extract, Pam3CSK4, heat-killed Listeria monocytogenes, FSL-1, flagellin and canine recombinant IL-17A significantly increased CXCL8 secretion, while the vitamin D metabolite calcitriol significantly suppressed the production of this chemokine. This study showed that certain allergens, TLRL, IL-17A and calcitriol modulate CXCL8 secretion in a cell line of canine buccal epithelial cells.

Posology and Serum-/Xeno-Free Engineered Adipose Stromal Cells Cell Sheets

Well-characterized adipose stem cells and chemically defined culture media are important factors that control the production of the cell sheet, used in translational medicine. In this study, we have developed and engineered multilayer adipose stem cell cell sheets (ASCCSs) using chemically defined/serum-free culture media: undifferentiated or differentiated into osteoblasts and chondrocytes. In addition, using the cell sheet transmittance, we estimated the number of cells per cell sheet. Undifferentiated ASCCSs were engineered in 10 days, using serum-free/xeno-free culture media. They were CD29⁺, CD73⁺, CD90⁺, CD105+, HLA-A+, and HLA-DR-. ASCCSs differentiated into chondrocytes and osteoblasts were also engineered using chemically defined and animal-free culture media, in only 14 days. The addition of an ROCK inhibitor improved the chondrocyte cell sheet engineering. The decrease in the cell sheet transmittance rate was higher for the osteoblast cell sheets due to the intracellular Ca²⁺ accumulation. The estimation of cell number per cell sheet was carried out with the transmittance, which will provide important information for cell sheet posology. In conclusion, three types of ASCCSs were engineered using serum-free, xeno-free culture media, expressing their specific markers. Their transmittance measurement allowed estimating the number of cells per cell sheet, with a non-invasive methodology.

GMP compliant isolation of mucosal epithelial cells and fibroblasts from biopsy samples for clinical tissue engineering

Engineered epithelial cell sheets for clinical replacement of non-functional upper aerodigestive tract mucosa are regulated as medicinal products and should be manufactured to the standards of good manufacturing practice (GMP). The current gold standard for growth of epithelial cells for research utilises growth arrested murine 3T3 J2 feeder layers, which are not available for use as a GMP compliant raw material. Using porcine mucosal tissue, we demonstrate a new method for obtaining and growing non-keratinised squamous epithelial cells and fibroblast cells from a single biopsy, replacing the 3T3 J2 with a growth arrested primary fibroblast feeder layer and using pooled Human Platelet lysate (HPL) as the media serum supplement to replace foetal bovine serum (FBS). The initial isolation of the cells was semi-automated using an Octodissociator and the resultant cell suspension cryopreservation for future use. When compared to the gold standard of 3T3 J2 and FBS containing medium there was no reduction in growth, viability, stem cell population or ability to differentiate to mature epithelial cells. Furthermore, this method was replicated with Human buccal tissue, providing cells of sufficient quality and number to create a tissue engineered sheet.

Prevention of Stricture after Endoscopic Submucosal Dissection for Superficial Esophageal Cancer: A Review of the Literature

Endoscopic resection has been the standard treatment for intramucosal esophageal cancers (ECs) because of the low risk of lymph node metastases in the lesions. In recent years, endoscopic submucosal dissection (ESD), which can resect large ECs, has been performed. However, the risk of esophageal stricture after ESD is high when the mucosal defect caused by the treatment exceeds 3/4 of the circumference of the lumen. Despite the subsequent high risk of luminal stricture, ESD has been performed even in cases of circumferential EC. In such cases, it is necessary to take measures to prevent stricture. Therefore, in this review, we aimed to clarify the current status of stricture prevention methods after esophageal ESD based on previous literature. Although various prophylactic methods have been reported to have stricture-preventing effects, steroid injection therapy and oral steroid administration are mainstream. However, in cases of circumferential EC, both steroid injection therapy and oral steroid administration cannot effectively prevent luminal stricture. To solve this issue, clinical applications, such as tissue shielding methods with polyglycolic acid sheet, autologous oral mucosal epithelial sheet transplantation, and stent placement, have been developed. However, effective prophylaxis of post-ESD mucosal defects of the esophagus is still unclear. Therefore, further studies in this research field are needed.

Regenerative medicine for the upper gastrointestinal tract

The main surgical strategy for gastrointestinal tract malignancy is en bloc resection, which consists of not only resection of the involved organs but also simultaneous resection of the surrounding or adjacent mesenteries that contain lymph vessels and nodes. After resection of the diseased organs, the defect of the gastrointestinal conduit is replaced with organs located downstream, such as the stomach and jejunum. However, esophageal and gastric reconstruction using these natural substitutes is associated with a diminished quality of life due to the loss of the reserve function, damage to the antireflux barrier, and dumping syndrome. Thus, replacement of the deficit after resection with the patient's own regenerated tissue to compensate for the lost function and tissue using regenerative medicine will be an ideal treatment. Many researchers have been trying to construct artificial organs through tissue engineering techniques; however, none have yet succeeded in growing a whole organ because of the complicated functions these organs perform, such as the processing and absorption of nutrients. While exciting results have been reported with regard to tissue engineering techniques concerning the upper gastrointestinal tract, such as the esophagus and stomach, most of these achievements have been observed in animal models, and few successful approaches in the clinical setting have been reported for the replacement of mucosal defects. We review the recent progress in regenerative medicine in relation to the upper gastrointestinal tract, such as the esophagus and stomach. We also focus on the functional capacity of regenerated tissue and its role as a culture system to recapitulate the mechanisms underlying infectious disease. With the emergence of technology such as the fabrication of decellularized constructs, organoids and cell sheet medicine, collaboration between gastrointestinal surgery and regenerative medicine is expected to help establish novel therapeutic modalities in the future.

Transplantation of autologous oral mucosal epithelial cell sheets inhibits the development of acquired external auditory canal atresia in a rabbit model

Acquired external auditory canal atresia is characterized by fibrous tissue formation in the ear canal, hearing loss and chronic otorrhea. Although the disease can be treated surgically, the recurrence rate is high. This study explored whether autologous oral mucosal epithelial cell sheets could be used as a novel therapy for ear canal atresia. We succeeded in generating a rabbit model of acquired external auditory canal atresia by dissecting the skin of the ear canal. Endoscopic and histological findings in this model indicated that atresia developed over a 4-week period and was not inhibited by the placement of polyglycolic acid sheets immediately after skin dissection. By contrast, transplantation of autologous oral mucosal epithelial cell sheets, which had been fabricated by culture on temperature-responsive inserts without a feeder layer, prevented the development of atresia during the 4-week period after skin dissection. Transplantation of autologous epithelial cell sheets after surgical treatment of acquired external auditory canal atresia could be a promising new method to reduce the risk of disease recurrence. STATEMENT OF SIGNIFICANCE: Acquired external auditory canal atresia is characterized by fibrous tissue formation in the ear canal, which leads to hearing loss and chronic otorrhea. Although surgical treatments are available, the recurrence rate is high. In this study, we successfully generated a rabbit model of acquired external auditory canal atresia by dissecting the skin of the ear canal. Furthermore, we utilized this new animal model to investigate whether the transplantation of autologous oral mucosal epithelial cell sheets could be used as a novel therapy for ear canal atresia. Our results raise the possibility that the transplantation of autologous epithelial cell sheets after surgical treatment of ear canal atresia could be a promising new method to reduce the risk of disease recurrence.

Adjuvanting Allergen Extracts for Sublingual Immunotherapy: Calcitriol Downregulates CXCL8 Production in Primary Sublingual Epithelial Cells

Application of allergens onto the sublingual epithelium is used to desensitize allergic individuals, a treatment known as sublingual immunotherapy. However, the response of sublingual epithelial cells to house dust mite allergen and potential tolerance-promoting adjuvants such as Toll-like receptor (TLR) ligands and calcitriol has not been investigated. In order to study this, primary sublingual epithelial cells were isolated from dogs and cultured in vitro. After 24-h incubation with a Dermatophagoides farinae extract, a Dermatophagoides pteronyssinus extract, TLR2 ligands (FSL-1, heat-killed Listeria monocytogenes, Pam3CSK4), a TLR3 ligand (poly I:C), a TLR4 ligand [lipopolysaccharide (LPS)], and calcitriol (1,25-dihydroxyvitamin D₃), viability of the cells was analyzed using an MTT test, and their secretion of interleukin 6 (IL-6), IL-10, CXCL8, and transforming growth factor β1 (TGF-β1) was measured by enzyme-linked immunosorbent assay. Additionally, to evaluate its potential effect as an adjuvant, sublingual epithelial cells were incubated with calcitriol in combination with a D. farinae extract followed by measurement of CXCL8 secretion. Furthermore, the effect of D. farinae and calcitriol on the transcriptome was assessed by RNA sequencing. The viability of the sublingual epithelial cells was significantly decreased by poly I:C, but not by the other stimuli. CXCL8 secretion was significantly increased by D. farinae extract and all TLR ligands apart from LPS. Calcitriol significantly decreased CXCL8 secretion, and coadministration with D. farinae extract reduced CXCL8 concentrations to levels seen in unstimulated sublingual epithelial cells. Although detectable, TGF-β1 secretion could not be modulated by any of the stimuli. Interleukin 6 and IL-10 could not be detected at the protein or at the mRNA level. It can be concluded that a D. farinae extract and TLR ligands augment the secretion of the proinflammatory chemokine CXCL8, which might interfere with sublingual desensitization. On the other hand, CXCL8 secretion was reduced by coapplication of calcitriol and a D. farinae extract. Calcitriol therefore seems to be a suitable candidate to be used as adjuvant during sublingual immunotherapy.

Viability evaluation of layered cell sheets after ultraviolet light irradiation of 222 nm

Introduction

The objective of this study was to evaluate the cell viability of layered cell sheets, irradiated with 222 nm UV light.

Methods

UV transmittance of 222 nm and 254 nm was evaluated when the cell sheets of NCTC Clone 929 cells were irradiated UV light. Cell viability was evaluated after irradiation of 222 nm using 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. Following irradiation of two layered cell sheets at 500 mJ/cm², the cell damage of lower layers was evaluated by a colony formation and MTT assays.

Results

The UV transmittance of 222 nm was 10 times less than that of 254 nm. A MTT assay revealed that cells of cell sheets irradiated at 222 nm was less damaged than those at 254 nm, when irradiated at 5 mJ/cm². Cell colonies were formed for cells of lower layers irradiated at 222 nm whereas no colony formation was observed for those irradiated at 254 nm. Significantly higher MTT activity was observed for cells of lower layers irradiated at 222 nm than at 254 nm.

Conclusions

It is concluded that 222 nm irradiation is biologically safe for cell viability.

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The cell viability of two-layered cell sheets was evaluated after irradiation of UV light at 222 nm.

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UV light at 222 nm is safer to the lower layer than the conventional UV light at 254 nm.

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The reason can be attributed to the lower transmission of UV light at 222 nm through cell sheets.

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UV light at 222 nm could be one of promising tools to be required for the sterilization in the field of regenerative therapy.

Esophageal regenerative therapy using cell sheet technology

We have been conducting research on esophageal regenerative therapy using cell sheet technology. In particular, in the endoscopic field, we have pushed forward clinical research on endoscopic transplantation of cultured autologous oral mucosal epithelial cell sheets to esophageal ulcer after endoscopic submucosal dissection (ESD). We started research in this direction using animal models in 2004 and performed clinical research in 2012 in collaboration with Nagasaki University and Karolinska Institute. Although in full-circumferential cases it was difficult to prevent esophageal stricture after ESD, there were no complications and stricture could be suppressed. The cell sheet technology is still in its infancy. However, we are convinced that it has a high potential for application in various areas of gastrointestinal science. In this review, we focus on the pre-clinical and clinical trial results obtained and on the theoretical aspects of (1) stricture prevention, (2) esophageal tissue engineering research, and (3) endoscopic transplantation, and review the esophageal regenerative therapy by cell sheet technology.

A stable protocol for the fabrication of transplantable human oral mucosal epithelial cell sheets for clinical application

Introduction

Cultured stratified epithelial cell sheets have been clinically utilized as transplantable grafts for the regeneration of epithelial tissues, such as the esophagus, cornea, skin, and intraoral cavity. These cell sheets are expected to gain widespread use as regenerative medicine products and save many patients. For this purpose, establishing and disseminating the stale protocol of fabricating the cell sheet is crucial. The fabrication of cultured stratified epithelial cell sheets consists of many important steps, and since the patients' epithelial cell conditions vary widely and are sometimes unstable, the qualities of the epithelial cell grafts are likewise potentially unstable. Therefore, in this paper, we report the stable protocol for fabrication of the transplantable cell sheet particularly from patient-derived oral mucosal tissues.

Methods

Serum extracted from blood and buccal mucosal tissue were collected in Nagasaki University and transported to Tokyo Women's Medical University. Oral mucosal epithelial cells were collected by minimum trypsin method, and this treatment was studied whether to be a critical procedure. After 14 days cultivation, cultured cells were examined whether to be transplantable as cell sheets.

Results

We successfully transported buccal mucosal tissue and serum without damage and contamination. Oral mucosal epithelial cells were collected with high viability by minimum trypsin method. Finally, we succeeded to stably fabricate oral mucosal epithelial cell sheets in all 10 patients.

Conclusions

We established a stable protocol for the fabrication of human oral mucosal epithelial cell sheets and their transportation in clinical settings in this study. These methodologies could also be basis for transplantation therapy using cultured cell sheets of various types other than oral mucosal epithelial cell and will contribute largely to the future development of regenerative medicine.

Thermoresponsive polymers and their biomedical application in tissue engineering - a review

Thermoresponsive polymers hold great potential in the biomedical field, since they enable the fabrication of cell sheets, in situ drug delivery and 3D-printing under physiological conditions. In this review we provide an overview of several thermoresponsive polymers and their application, with focus on poly(N-isopropylacrylamide)-surfaces for cell sheet engineering. Basic knowledge of important processes like protein adsorption on surfaces and cell adhesion is provided. For different thermoresponsive polymers, namely PNIPAm, Pluronics, elastin-like polypeptides (ELP) and poly(N-vinylcaprolactam) (PNVCL), synthesis and basic chemical and physical properties have been described and the mechanism of their thermoresponsive behavior highlighted. Fabrication methods of thermoresponsive surfaces have been discussed, focusing on PNIPAm, and describing several methods in detail. The latter part of this review is dedicated to the application of the thermoresponsive polymers and with regard to cell sheet engineering, the process of temperature-dependent cell sheet detachment is explained. We provide insight into several applications of PNIPAm surfaces in cell sheet engineering. For Pluronics, ELP and PNVCL we show their application in the field of drug delivery and tissue engineering. We conclude, that research of thermoresponsive polymers has made big progress in recent years, especially for PNIPAm since the 1990s. However, manifold research possibilities, e.g. in surface fabrication and 3D-printing and further translational applications are conceivable in near future.

Identification and In Vitro Expansion of Buccal Epithelial Cells

Ex vivo-expanded buccal mucosal epithelial (BME) cell transplantation has been used to reconstruct the ocular surface. Methods for enrichment and maintenance of BME progenitor cells in ex vivo cultures may improve the outcome of BME cell transplantation. However, the parameter of cell seeding density in this context has largely been neglected. This study investigates how varying cell seeding density influences BME cell proliferation and differentiation on tissue culture polystyrene (TCPS). The highest cell proliferation activity was seen when cells were seeded at 5×10⁴ cells/cm². Both below and above this density, the cell proliferation rate decreased sharply. Differential immunofluorescence analysis of surface markers associated with the BME progenitor cell population (p63, CK19, and ABCG2), the differentiated cell marker CK10 and connexin 50 (Cx50) revealed that the initial cell seeding density also significantly affected the progenitor cell marker expression profile. Hence, this study demonstrates that seeding density has a profound effect on the proliferation and differentiation of BME stem cells in vitro, and this is relevant to downstream cell therapy applications.

Native and synthetic scaffolds for limbal epithelial stem cell transplantation

Limbal stem cell deficiency (LSCD) is a complex blinding disease of the cornea, which cannot be treated with conventional corneal transplants. Instead, a stem cell (SC) graft is required to replenish the limbal epithelial stem cell (LESC) reservoir, which is ultimately responsible for regenerating the corneal epithelium. Current therapies utilize limbal tissue biopsies that harbor LESCs as well as tissue culture expanded cells. Typically, this tissue is placed on a scaffold that supports the formation of corneal epithelial cell sheets, which are then transferred to diseased eyes. A wide range of biological and synthetic materials have been identified as carrier substrates for LESC, some of which have been used in the clinic, including amniotic membrane, fibrin, and silicon hydrogel contact lenses, each with their own advantages and limitations. This review will provide a brief background of LSCD, focusing on bio-scaffolds that have been utilized in limbal stem cell transplantation (LSCT) and materials that are being developed as potentially novel therapeutics for patients with this disease.

STATEMENT OF SIGNIFICANCE

The outcome of patients with corneal blindness that receive stem cell grafts to restore eye health and correct vision varies considerably and may be due to the different biological and synthetic scaffolds used to deliver these cells to the ocular surface. This review will highlight the positive attributes and limitations of the myriad of carriers developed for clinical use as well as those that are being trialled in pre-clinical models. The overall focus is on developing a standardized therapy for patients, however due to the multiple causes of corneal blindness, a personal regenerative medicine approach may be the best option.

Oral epithelial cell sheets engraftment for esophageal strictures after endoscopic submucosal dissection of squamous cell carcinoma and airplane transportation

Endoscopic submucosal dissection (ESD) permits en bloc removal of superficial oesophageal squamous cell carcinoma (ESCC). However, post-procedure stricture is common after ESD for widespread tumours, and multiple endoscopic balloon dilation (EBD) procedures are required. We aimed to evaluate the safety and effectiveness of endoscopic transplantation of tissue-engineered autologous oral mucosal epithelial cell sheets that had been transported by air over a distance of 1200 km in controlling postprocedural oesophageal stricture. Ten patients who underwent complete circular or semicircular ESD for ESCC were transplanted with cell sheets. The safety of the entire process including cell sheet preparation, transport, ESD and cell sheet transplantation was assessed. The incidence of oesophageal stricture, number of EBD sessions, and time until epithelialization were investigated. Each ESD was successfully performed, with subsequent cell sheet engrafting carried out safely. Following cell sheet transplantation, the luminal stenosis rate was 40%, while the median number of EBD sessions was 0. The median post-ESD ulcer healing period was rather short at 36 days. There were no significant complications at any stage of the process. Cell sheet transplantation and preparation at distant sites and transportation by air could be a safe and promising regenerative medicine technology.

Regenerative medicine for the esophagus

Advances in tissue engineering techniques have made it possible to use human cells as biological material. This has enabled pharmacological studies to be conducted to investigate drug effects and toxicity, to clarify the mechanisms underlying diseases, and to elucidate how they compensate for impaired organ function. Many researchers have tried to construct artificial organs using these techniques, but none has succeeded in growing a whole organ. Unlike other digestive organs with complicated functions, such as the processing and absorption of nutrients, the esophagus has the relatively simple function of transporting content, which can be replicated easily by a substitute. In regenerative medicine, various combinations of materials have been applied, including scaffolding, cell sources, and bioreactors. Exciting results of tissue engineering techniques for the esophagus have been reported. In animal models, replacing full-thickness and full-circumferential defects remains challenging because of stenosis and leakage after implantation. Although many reports have manipulated various scaffolds, most have emphasized the importance of both epithelial and mesenchymal cells for the prevention of stenosis. However, the results of repair of partial full-thickness defects and mucosal defects have been promising. Two successful approaches for the replacement of mucosal defects in a clinical setting have been reported, although in contrast to the many animal models, there are few pilot studies in humans. We review the recent results and evaluate the future of regenerative medicine for the esophagus.

Approaches for stricture prevention after esophageal endoscopic resection

BACKGROUND AND AIMS

Endoscopic resection of extensive esophageal lesions has become more common as endoscopic resection techniques and equipment have developed. However, extensive esophageal endoscopic resections can cause postoperative esophageal strictures, which have a negative impact on the quality of life of patients. We aimed to review current treatments and innovative approaches to prevent esophageal strictures after widespread endoscopic resection of esophageal lesions.

METHODS

We performed a comprehensive literature search from 2000 to 2016 using predetermined search terms to identify relevant articles and summarized their results as a narrative review.

RESULTS

A total of 21 original articles and case series were identified. A circumferential mucosal defect involving more than three fourths of the esophageal luminal circumference was the primary risk factor for developing an esophageal stricture after endoscopic resection. Oral and injectable steroid therapy demonstrated promise in preventing post-endoscopic submucosal dissection esophageal strictures, with both strategies significantly reducing the number of required endoscopic balloon dilations. More data are needed on prophylactic self-expandable metal stents, local botulinum toxin injection, and oral tranilast as a strategy to prevent post-endoscopic submucosal dissection esophageal strictures. Although preliminary studies of tissue-shielding resection sites with polyglycolic acid sheets and fibrin glue and autologous cell sheet transplantation have demonstrated promising results, additional larger validation studies are needed.

CONCLUSIONS

Oral and locally injected/administered steroids are first-line options for the prevention of esophageal strictures, but additional innovative solutions are being developed.

Cellular events and behaviors after grafting of stratified squamous epithelial cell sheet onto a hydrated collagen gel

Autologous stratified squamous epithelial cell sheets have been successfully used to treat epithelial defects in tissues such as the cornea and the esophagus. However, the regenerative cellular events occurring in the grafted epithelial cells are unclear in the early stages of wound healing. In this study, we created an in vitro grafting model using cultured normal human epidermal keratinocyte (NHEK) sheets and a type I collagen gel to investigate the cellular processes that occur within the grafted cell sheet. Cultured NHEK cells successfully became a stratified squamous cell sheet resembling epithelial tissue, retained expression of cellular integrins and adhesion proteins, and adhered successfully to a type I collagen gel. After culture on the collagen gel, expression of E‐cadherin, and β‐catenin decreased in the cells of the basal layer of the grafted cell sheet, resembling events characteristic of a partial epithelial–mesenchymal transition (EMT). These basal cells also induced migration of the cell sheet. Those phenomena are consistent with the essential events that occur in the wound‐healing process observed previously in cell studies. Therefore, the epithelial cell sheet grafted onto a type I collagen gel is a suitable model in vitro to study cellular events and behaviors. Furthermore, we also addressed the therapeutic mechanisms by which the epithelial cell sheet promotes wound healing.

Concise review: transplantation of cultured oral mucosal epithelial cells for treating limbal stem cell deficiency-current status and future perspectives

A number of diseases and external factors can deplete limbal stem cells, causing pain and visual loss. Ten years have passed since the first transplantation of cultured oral mucosal epithelial cells in humans, representing the first autologous cell-based therapy for severe bilateral limbal stem cell deficiency. Its steady increase in popularity since then can be attributed to the accumulating evidence of its efficacy in reverting limbal stem cell deficiency. In this review, the focus is on clinical, and to a lesser degree laboratory, features of cultured oral mucosal epithelial transplants over the past 10 years. Comparisons with other available technologies are made. Avenues for research to stimulate further improvements in clinical results and allow worldwide distribution of limbal stem cell therapy based on oral mucosal cells are discussed. These include storage and transportation of cultured oral mucosal epithelial sheets and in vivo culture of oral mucosal epithelial cells.

Culture of Oral Mucosal Epithelial Cells for the Purpose of Treating Limbal Stem Cell Deficiency

The cornea is critical for normal vision as it allows allowing light transmission to the retina. The corneal epithelium is renewed by limbal epithelial cells (LEC), which are located in the periphery of the cornea, the limbus. Damage or disease involving LEC may lead to various clinical presentations of limbal stem cell deficiency (LSCD). Both severe pain and blindness may result. Transplantation of cultured autologous oral mucosal epithelial cell sheet (CAOMECS) represents the first use of a cultured non-limbal autologous cell type to treat this disease. Among non-limbal cell types, CAOMECS and conjunctival epithelial cells are the only laboratory cultured cell sources that have been explored in humans. Thus far, the expression of p63 is the only predictor of clinical outcome following transplantation to correct LSCD. The optimal culture method and substrate for CAOMECS is not established. The present review focuses on cell culture methods, with particular emphasis on substrates. Most culture protocols for CAOMECS used amniotic membrane as a substrate and included the xenogeneic components fetal bovine serum and murine 3T3 fibroblasts. However, it has been demonstrated that tissue-engineered epithelial cell sheet grafts can be successfully fabricated using temperature-responsive culture surfaces and autologous serum. In the studies using different substrates for culture of CAOMECS, the quantitative expression of p63 was generally poorly reported; thus, more research is warranted with quantification of phenotypic data. Further research is required to develop a culture system for CAOMECS that mimics the natural environment of oral/limbal/corneal epithelial cells without the need for undefined foreign materials such as serum and feeder cells.

Autologous human nasal epithelial cell sheet using temperature-responsive culture insert for transplantation after middle ear surgery

Postoperative mucosal regeneration of the middle ear cavity and the mastoid cavity is of great importance after middle ear surgery. However, the epithelialization of the mucosa in the middle ear is retarded because chronic inflammation without epithelialization aggravates gas exchange and clinical function. These environmental conditions in the middle ear lead to postoperative retraction and adhesion of the newly-formed tympanic membrane. Therefore, if the mucosa on the exposed middle ear bone surface can be rapidly regenerated after surgery, the surgical treatments for cholesteatoma and adhesive middle ear disease can potentially be improved. In this study, we successfully generated a cell sheet designed for the postoperative treatment of cholesteatoma. We used nasal cells to create an artificial middle ear mucosal cell sheet with a three-dimensional (3D) configuration similar to that of the middle ear mucosa. The sheets consisted of multi-layered mucosal epithelia and lower connective tissue and were similar to normal middle ear mucosa. This result indicates that tissue-engineered mucosal cell sheets would be useful to minimize complications after surgical operations in the middle ear and future clinical applications are expected. Copyright © 2015 John Wiley & Sons, Ltd.

How to prevent contamination with Candida albicans during the fabrication of transplantable oral mucosal epithelial cell sheets

We have utilized patients' own oral mucosa as a cell source for the fabrication of transplantable epithelial cell sheets to treat limbal stem cell deficiency and mucosal defects after endoscopic submucosal dissection of esophageal cancer. Because there are abundant microbiotas in the human oral cavity, the oral mucosa was sterilized and 40 μg/mL gentamicin and 0.27 μg/mL amphotericin B were added to the culture medium in our protocol. Although an oral surgeon carefully checked each patient's oral cavity and although candidiasis was not observed before taking the biopsy, contamination with Candida albicans (C. albicans) was detected in the conditioned medium during cell sheet fabrication. After adding 1 μg/mL amphotericin B to the transportation medium during transport from Nagasaki University Hospital to Tokyo Women's Medical University, which are 1200 km apart, no proliferation of C. albicans was observed. These results indicated that the supplementation of transportation medium with antimycotics would be useful for preventing contamination with C. albicans derived from the oral mucosa without hampering cell proliferation.

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Normal human oral mucosal epithelial cells were cultured in a clinical setting.

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Contamination with Candida albicans was detected in the culture.

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The culture medium included 0.27 μg/mL amphotericin B.

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Contamination was prevented by 1 μg/mL amphotericin B in the medium for transportation of the oral tissue.

Application of regenerative medical technology using tissue-engineered cell sheets for endoscopic submucosal dissection of esophageal neoplasms

We have developed a technique for endoscopic transplantation of cultured autologous oral mucosal epithelial cell sheets to an esophageal ulcer following endoscopic submucosal dissection (ESD). The epithelial cell sheets successfully prevented esophageal stricture after ESD. Key technology is that epithelial cell sheets cultured from oral mucosal tissue and attached proteins can be harvested using cell sheet technology and can be transplanted to a wound site without the use of adhesive material. This regenerative procedure can promote the epithelialization of ulceration safely and effectively. In the near future, the development of advanced endoscopic treatment of regenerative medicine shows promise.

Tissue engineering of oral mucosa: a shared concept with skin

Tissue-engineered oral mucosa, in the form of epithelial cell sheets or full-thickness oral mucosa equivalents, is a potential solution for many patients with congenital defects or with tissue loss due to diseases or tumor excision following a craniofacial cancer diagnosis. In the laboratory, it further serves as an in vitro model, alternative to in vivo testing of oral care products, and provides insight into the behavior of the oral mucosal cells in healthy and pathological tissues. This review covers the old and new generation scaffold types and materials used in oral mucosa engineering; discusses similarities and differences between oral mucosa and skin, the methods developed to reconstruct oral mucosal defects; and ends with future perspectives on oral mucosa engineering.

Evidence of the survival of ectopically transplanted oral mucosal epithelial stem cells after repeated wounding of cornea

Tissue engineering has become an essential tool in the development of regenerative medicine. We have developed cell sheet-based techniques for use in regenerative medicine that have already been successfully used in clinical applications. Native corneal epithelium is produced from limbal stem cells located in the transition zone between the cornea and the bulbar conjunctiva. Limbal stem cell deficiency (LSCD) is a severe defect of the limbal stem cells leading to vision loss due to conjunctival epithelial invasion and neovascularization. Rabbit LSCD models were treated with transplantable autologous oral mucosal epithelial cell (OEC) sheets fabricated on temperature-responsive cell culture surfaces, after which, the ocular surfaces were clear and smooth with no observable defects. The central part of the reconstructed ocular surface was scraped and wounded, after which proliferating epithelial cells covered the scraped area within a few days. The ocular surfaces were clear and smooth even after repeated scrapings and consisted of only OECs or heterogeneously mixed with corneal epithelial cells. This study demonstrates that transplanted cell sheets containing oral mucosal epithelial stem cells could reconstruct the ocular surface to maintain cornea homeostasis; moreover, they provide an ideal microenvironment to support the proliferation of remaining native limbal stem cells.

Regenerative medicine: tissue-engineered cell sheet for the prevention of post-esophageal ESD stricture

Induced pluripotent stem (iPS) cells have captured the world's attention and directed an unprecedented focus on regenerative medicine. The potential of iPS cells to aid in the development of new treatments for various diseases is exciting, and researchers are only beginning to discover their potential benefits for humans. iPS cells are more effective if they are interconnected with tissues; however, new technologies are needed to create and transplant these tissues. This study introduces a new connection between endoscopy and regenerative medicine in gastroenterology through specifically addressing how cell sheet technology can be a viable method of tissue creation and transplantation.

Towards a defined, serum- and feeder-free culture of stratified human oral mucosal epithelium for ocular surface reconstruction

PURPOSE

Ocular surface reconstruction with cultivated oral mucosal epithelial transplantation technique is a viable treatment option for severe ocular surface injuries and diseases with limbal stem cell deficiency. Currently, this technique is based on utilization of xenogenic, allogenic or undefined components such as murine 3T3 feeders, serum and amniotic membrane. In this study, we aimed to find a more defined culture method to generate stratified human oral mucosal epithelium.

METHODS

In this study, we have examined the formation of stratified cell sheets from human oral mucosal epithelial cells under serum-free culture environment both in the absence and presence of fibroblast-conditioned culture medium and elevated epidermal growth factor (EGF) concentration.

RESULTS

In all examined culture conditions, the cultivated oral epithelial cells formed a stratified tissue, which was positive for keratins K3/12, K4 and K13. The tissue-engineered oral epithelia also expressed proliferation and progenitor markers Ki67 and p63 in the basal layer of the cell sheets, suggesting that the epithelia still had regenerative capacity. The cultures presented expression of tight junction proteins ZO-1 and occludin and high transepithelial electrical resistance values.

CONCLUSION

In this culture method, we have been able to produce stratified cell sheets successfully without serum, conditioning of the medium or increased EGF concentration. We provide a novel protocol to produce tight multi-layered epithelium with proliferative potential, which can be easily adapted for cultivated oral mucosal epithelial transplantation.

The regulation of epithelial cell proliferation and growth by IL-1 receptor antagonist

We have performed clinical translation of epithelial cell sheets fabricated on temperature-responsive culture surfaces to treat cornea and esophagus. In the preclinical study using animal models, we found epithelial cell growth potential varied among species. Canine epithelial cell growth was prominent, while rat one was poor under 3T3 feeder layer-free condition. The aim of the present study was to identify growth-promoting factors for epithelial cells. Conditioned medium of canine cell culture harvested at different time points showed different growth promotive activity for rat epithelial cells. Time-dependent gene expression was quantitatively evaluated for forty growth factors, and compared with conditioned medium results. Statistically significant promotive activity was observed with IL-1RA, and significant inhibitory activity was observed with IL-1α. Furthermore, neutralizing anti-IL-1α antibody also showed significant promotive activity. Human epidermal keratinocytes were promoted to proliferate by IL-1RA and neutralizing anti-IL-1α antibody, and showed well differentiation to form transplantable, squamous stratified epithelial cell sheets. These findings would be useful to fabricate reproducible, transplantable epithelial cell sheets for regenerative medicine.

Cell sheet technology for regeneration of esophageal mucosa

The progress of tissue-engineering technology has realized development of new therapies to treat various disorders by using cultured cells. Cell- and tissue-based therapies have been successfully applied to human patients, and several tissue-engineered products have been approved by the regulatory agencies and are commercially available. In the review article, we describe our experience of development and clinical application of cell sheet-based regenerative medicine. Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have been shown to be useful for removal of gastrointestinal neoplasms with less invasiveness compared with open surgery, especially in esophageal surgery. However, postoperative inflammation and stenosis are major complications observed after intensive mucosal resection. Therefore, we have developed novel regenerative medicine to prevent such complications and promote wound healing of esophageal mucosa after EMR or ESD. Transplantable oral mucosal epithelial cell sheets were fabricated from patients’ own oral mucosa. Immediately after EMR or ESD, fabricated autologous cell sheets were endoscopically transplanted to the ulcer sites. We performed a preclinical study with a canine model. In human clinical settings, cell culture and cell sheet fabrication were performed in clean rooms according to good manufacturing practice guidelines, and pharmaceutical drugs were used as supplements to culture medium in place of research regents used in animal study. We believe that cell-based regenerative medicine would be useful to improve quality of life of patients after EMR or ESD.

Prevention of esophageal stricture after endoscopic submucosal dissection using tissue-engineered cell sheets

BACKGROUND & AIMS

The use of esophageal endoscopic submucosal dissection (ESD) to remove superficial esophageal neoplasms is gradually becoming more common in Japan. However, large-scale esophageal ESD often requires subsequent multiple balloon dilations to prevent postoperative esophageal stricture. We investigated the safety and efficacy of endoscopic transplantation of tissue-engineered autologous oral mucosal epithelial cell sheets in preventing formation of strictures after ESD.

METHODS

We performed an open-label, single-arm, single-institute study. We collected specimens of oral mucosal tissue from 9 patients with superficial esophageal neoplasms. Epithelial cell sheets were fabricated ex vivo by culturing isolated cells for 16 days on temperature-responsive cell culture surfaces. After a reduction in temperature, these sheets were endoscopically transplanted directly to the ulcer surfaces of patients who had just undergone ESD. All patients were monitored by endoscopy once a week until epithelialization was complete.

RESULTS

Autologous cell sheets were successfully transplanted to ulcer surfaces using an endoscope. Complete re-epithelialization occurred within a median time of 3.5 weeks. No patients experienced dysphagia, stricture, or other complications following the procedure, except for one patient who had a full circumferential ulceration that expanded to the esophagogastric junction.

CONCLUSIONS

Sutureless, endoscopic transplantation of carrier-free cell sheets composed of autologous oral mucosal epithelial cells safely and effectively promotes re-epithelialization of the esophagus after ESD. Patients in this study did not experience any serious complications. This procedure might be used to prevent stricture formation following ESD and improve patients' quality of life. Further study will be needed to show that stricture formation can be prevented.

Tracheal reconstruction by mesenchymal stem cells with small intestine submucosa in rabbits

AIM

The increasing number of newborns requiring intubation and artificial ventilation in the sophisticated premature and intensive care units of recent years has been followed by a concomitant increase in the number of children who develop tracheal stenosis as a sequela of prolonged intubation, with a consequent increasing need for tracheal surgical repair. The aim of this study was to evaluate tracheal reconstruction by monolayered autologous mesenchymal stem cells (MSCs) with small intestine submucosa (SIS) in a rabbit model.

METHODS

Twelve male rabbits were randomly divided into three groups: rabbits with tracheal defects without reconstruction (untreated group, n=4), rabbits with tracheal defects given porcine small intestine submucosa graft (SIS group, n=4), and rabbits with tracheal defects that underwent transplantation of monolayered mesenchymal stem cells on SIS (SIS+MSC group, n=4). Histological and endoscopic analyses were performed by hematoxylin-eosin staining (H&E), Prussian blue staining and endoscopy.

RESULTS

Tracheal stenosis in the SIS+MSC group was minimal, compared to the untreated group and SIS group. Specimens obtained from the untreated and SIS groups showed severe infiltration of inflammatory cells and granulation tissue formation into the trachea. In the SIS+MSC group, however, minimal infiltration of the inflammatory cells and granulation tissue formation were observed. Twelve weeks following the operation, regeneration of pseudostratified columnar epithelium was confirmed by H&E staining with minimal inflammatory cell infiltration in the SIS+MSC group. Moreover, Prussian blue staining clearly demonstrated the presence of labeled MSCs in the regenerated tissue of SIS+MSC group.

CONCLUSIONS

These results demonstrate that tracheal reconstruction by MSCs with SIS is effective in rabbits with tracheal defects with minimal mortality and morbidity, which appears to be a promising strategy in the treatment of tracheal defects.

Fabrication and validation of autologous human oral mucosal epithelial cell sheets to prevent stenosis after esophageal endoscopic submucosal dissection

OBJECTIVES

Human oral mucosal epithelial cells derived from 7 healthy volunteer donors were cultured in a clean room in a cell-processing center (CPC) according to good manufacturing practice guidelines. Cell culture and fabricated transplantable epithelial cell sheets were validated for treating ulcers after endoscopic mucosal dissection.

METHODS

The clonal growth and morphology of the human oral mucosal epithelial cells seeded on temperature-responsive surfaces were observed. During the cultivation, sterilization tests were performed to validate the environment in the CPC. To validate the purity and morphology of fabricated epithelial cell sheets, cell sheets harvested from temperature-responsive surfaces by temperature reduction were examined by histology and flow cytometry.

RESULTS

Human oral mucosal epithelial cells were successfully cultured and harvested as continuous cell sheets from temperature-responsive culture inserts without any animal-derived materials. During the cultivations, the sterile environment in the CPC was confirmed. The results of histological and flow cytometry analysis showed the high reproducibility of stratification and the purity of the fabricated human oral mucosal epithelial cell sheets.

CONCLUSIONS

The method for fabricating epithelial cell sheets shown in this study was suitable for the validation for clinical trials and suggested usability of the fabricated cell sheets.

Production of an optimized tissue-engineered pig connective tissue for the reconstruction of the urinary tract

Nonurological autologous tissues are used for urethral reconstruction to correct urinary tract disorders but are still leading to complications. Other substitutes have been studied on small animal models without great success. For preclinical tests, we selected the porcine model for its similarity to the human urinary tract. Up to now, porcine skin fibroblasts were not able to synthesize enough extracellular matrix under standard conditions to sustain the formation of an adequate tissue for transplantation purposes. Therefore, our goal was to optimize the harvesting site and culture conditions to obtain a thick and easy to handle porcine fibroblast tissue. The oral mucosa was found to be the ideal harvesting site, and a culture temperature of 39°C enabled the formation of a good porcine fibroblast sheet. We successfully superimpose three fibroblast sheets that merged into a thick and resistant tissue where physiological extracellular matrix was produced. Mechanical resistance evaluation by uniaxial traction on the three-layer fibroblast constructs also demonstrated its suitable properties. The production of this porcine connective tissue offers an interesting option in the field of urological tissue engineering. Autologous experiments on a larger animal model are now possible and accessible, allowing the performance of long-term in vivo studies.

Fabrication of human oral mucosal epithelial cell sheets for treatment of esophageal ulceration by endoscopic submucosal dissection

BACKGROUND

Esophageal stenosis is one of the major complications of aggressive endoscopic resection. Tissue-engineered epithelial cell grafts have demonstrated effectiveness in promoting re-epithelialization and suppressing inflammation causing esophageal scarring and stenosis after endoscopic submucosal dissection (ESD) in an animal model.

OBJECTIVE

To confirm the reproducibility and efficacy of a human oral mucosal epithelial cell (hOMEC) sheet cultured on temperature-responsive surface in conformity with Good Manufacturing Practice guidelines.

DESIGN

A preclinical study.

SETTING

Good Manufacturing Practice grade cell-processing center, animal laboratory.

SUBJECTS

Canine esophageal ulcer models, which were made by ESD.

INTERVENTIONS

Oral mucosal specimens were obtained from 7 healthy volunteers.

MAIN OUTCOME MEASUREMENT

Fabricated and transplanted hOMEC sheets were subjected to histological analysis.

RESULTS

The reproducibility of the fabrication of hOMEC sheets was confirmed. In this method, animal-derived materials such as 3T3 feeder layer and fetal bovine serum were successfully excluded from the culture condition. Furthermore, the environment of the culture room and safety cabinet in the cell-processing center was maintained for obtaining sterility assurances during the fabrication. Transplanted hOMEC sheets after ESD were observed to graft onto canine esophageal ulcer surfaces.

LIMITATIONS

Small number of subjects, animal model.

CONCLUSIONS

Cultured hOMEC sheets were fabricated without animal-derived materials and demonstrated efficacy as a medical device that promotes re-epithelialization of an esophageal ulcer after ESD.

Preparation of keratinocyte culture medium for the clinical applications of regenerative medicine

Keratinocyte culture medium (KCM) has been used for the in vitro culture of keratinocytes and other types of epithelial cells, and the medium includes various ingredients. In this study, two modified KCMs were prepared. In the first, insulin, hydrocortisone and antibiotics that are normally included in KCM were replaced with clinically approved pharmaceutical agents, except transferrin and selenium; in the second, cholera toxin (CT) was replaced by L-isoproterenol (ISO). The modified KCMs were then compared to conventional KCM containing laboratory-grade reagents. Induced cell colony formations of canine oral mucosal epithelial cells cultured in both modified KCMs were found to be nearly equivalent to that in the control KCM, and there was no significant difference between the effect of CT and ISO. Canine oral mucosal cells proliferated to confluence in all three KCM formulations, with or without the use of 3T3 feeder layers. Cultured epithelial cells were harvested from temperature-responsive culture surfaces as an intact cell sheet, and the immunohistochemical analysis of the sheets showed that p63 and cytokeratin were expressed in the epithelial cell sheets cultured in all KCMs. Eventually, in the modified KCM formula, fetal bovine serum was replaced by autologous human serum, and the formula was found to be able to fabricate human oral mucosal epithelial cell sheets. These results indicated that the modified KCM was equally efficient as conventional KCM in the fabrication of transplantable stratified epithelial cell sheets.

Cell sheet engineering: a unique nanotechnology for scaffold-free tissue reconstruction with clinical applications in regenerative medicine

Cell sheet technology (CST) is based on the use of thermoresponsive polymers, poly(N-isopropylacrylamide) (PIPAAm). The surface of PIPAAms is formulated in such a way as to make its typical thickness <100 nm. In this review, we first focus on how the methods of PIPAAm-grafted surface preparations and functionalization are important to be able to harvest a functional cell sheet, to be further transplanted. Then, we present aspects of tissue mimics and three-dimensional reconstruction of a tissue in vitro. Finally, we give an overview of clinical applications and clinically relevant animal experimentations of the technology, such as cardiomyopathy, visual acuity, periodonty, oesophageal ulcerations and type 1 diabetes.

Temperature-responsive intelligent interfaces for biomolecular separation and cell sheet engineering

Temperature-responsive intelligent surfaces, prepared by the modification of an interface with poly(N-isopropylacrylamide) and its derivatives, have been used for biomedical applications. Such surfaces exhibit temperature-responsive hydrophilic/hydrophobic alterations with external temperature changes, which, in turn, result in thermally modulated interactions with biomolecules and cells. In this review, we focus on the application of these intelligent surfaces to chromatographic separation and cell cultures. Chromatographic separations using several types of intelligent surfaces are mentioned briefly, and various effects related to the separation of bioactive compounds are discussed, including wettability, copolymer composition and graft polymer architecture. Similarly, we also summarize temperature-responsive cell culture substrates that allow the recovery of confluent cell monolayers as contiguous living cell sheets for tissue-engineering applications. The key factors in temperature-dependent cell adhesion/detachment control are discussed from the viewpoint of grafting temperature-responsive polymers, and new methodologies for effective cell sheet culturing and the construction of thick tissues are summarized.

Reconstruction of functional tissues with cell sheet engineering

The field of tissue engineering has yielded several successes in early clinical trials of regenerative medicine using living cells seeded into biodegradable scaffolds. In contrast to methods that combine biomaterials with living cells, we have developed an approach that uses culture surfaces grafted with the temperature-responsive polymer poly(N-isoproplyacrylamide) that allows for controlled attachment and detachment of living cells via simple temperature changes. Using cultured cell sheets harvested from temperature-responsive surfaces, we have established cell sheet engineering to create functional tissue sheets to treat a wide range of diseases from corneal dysfunction to esophageal cancer, tracheal resection, and cardiac failure. Additionally, by exploiting the unique ability of cell sheets to generate three-dimensional tissues composed of only cultured cells and their deposited extracellular matrix, we have also developed methods to create thick vascularized tissues as well as, organ-like systems for the heart and liver. Cell sheet engineering therefore provides a novel alternative for regenerative medicine approaches that require the re-creation of functional tissue structures.