Cell Sheet Transplantation for Esophageal Stricture Prevention after Endoscopic Submucosal Dissection in a Porcine Model

Betulin gel alleviates esophageal stricture following endoscopic submucosal dissection: an animal study

BACKGROUND

Esophageal stenosis is a troublesome complication after circumferential ESD. This study examined the efficacy of betulin gel in preventing esophageal stenosis after ESD in a porcine model.

METHODS

Twelve pigs were randomized to betulin group and control group evenly. At the distal esophagus, circumferential ESD was performed in all animals. In the betulin group, betulin gel was applied at days 1, 3, and 7. Endoscopy examination was performed at day 3, 1 week, 2 weeks, and 4 weeks post-ESD. Then pigs were killed for macroscopic and histologic esophageal evaluation.

RESULTS

The rate of esophageal stricture was lower in the betulin group (53.3 ± 12.5% vs 88.3% ± 2.9, p = 0.02). Betulin-treated pigs had lower dysphagia score (2.0 ± 0 vs 3.3 ± 0.5, p < 0.001), less weight loss (11.78% ± 2.16 vs 15.85% ± 3.63, p = 0.04), and better passability of the open and closed biopsies forceps (83.33% vs. 0%, p = 0.015, and 100% vs. 0%, p = 0.002) 4 weeks post-ESD. Histologically, better re-epithelization (63.2 ± 10.7 mm vs 22.8 ± 10.1 mm, p < 0.001), slighter submucosal fibrosis (0.95 ± 0.17 mm vs 2.32 ± 0.48 mm, p = 0.002), lower muscularis propria damage score (1 vs 3, p < 0.001), and less inflammatory cells (307 vs 675 per high-power field, p = 0.002) were noted in the betulin group. The expression levels of TGF-β1, collagen i, collagen III, and α-SMA were significantly lower in the betulin group compared to the control group (p < 0.05).

CONCLUSIONS

Betulin gel shows promise in reducing fibrosis, enhancing repair, and preventing esophageal stricture after ESD, suggesting a potential new strategy for prevention.

Scaffold-free 3D culture systems for stem cell-based tissue regeneration

Recent advances in scaffold-free three-dimensional (3D) culture methods have significantly enhanced the potential of stem cell-based therapies in regenerative medicine. This cutting-edge technology circumvents the use of exogenous biomaterial and prevents its associated complications. The 3D culture system preserves crucial intercellular interactions and extracellular matrix support, closely mimicking natural biological niches. Therefore, stem cells cultured in 3D formats exhibit distinct characteristics, showcasing their capabilities in promoting angiogenesis and immunomodulation. This review aims to elucidate foundational technologies and recent breakthroughs in 3D scaffold-free stem cell engineering, offering comprehensive guidance for researchers to advance this technology across various clinical applications. We first introduce the various sources of stem cells and provide a comparative analysis of two-dimensional (2D) and 3D culture systems. Given the advantages of 3D culture systems, we delve into the specific fabrication and harvesting techniques for cell sheets and spheroids. Furthermore, we explore their applications in pre-clinical studies, particularly in large animal models and clinical trials. We also discuss multidisciplinary strategies to overcome existing limitations such as insufficient efficacy, hostile microenvironments, and the need for scalability and standardization of stem cell-based products.

Strategies for Preventing Esophageal Stenosis After Endoscopic Submucosal Dissection and Progress in Stem Cell-Based Therapies

Endoscopic submucosal dissection (ESD) has been widely used in the early neoplasia of the esophagus. However, postoperative esophageal stenosis is a big problem, particularly when a large circumferential proportion of esophageal mucosa is resected. Currently, there are several methods available to prevent esophageal stenosis after ESD, including steroid administration, esophageal stent implantation, and endoscopic balloon dilation (EBD). However, the therapeutic effects of these are not yet satisfactory. Stem cell-based therapies has shown promising potential in reconstructing tissue structure and restoring tissue function. In this study, we discussed the current strategies for preventing esophageal stenosis after ESD and perspectives of stem cell-based therapies for the prevention of esophageal stenosis.

The preclinical and clinical progress of cell sheet engineering in regenerative medicine

Cell therapy is an accessible method for curing damaged organs or tissues. Yet, this approach is limited by the delivery efficiency of cell suspension injection. Over recent years, biological scaffolds have emerged as carriers of delivering therapeutic cells to the target sites. Although they can be regarded as revolutionary research output and promote the development of tissue engineering, the defect of biological scaffolds in repairing cell-dense tissues is apparent. Cell sheet engineering (CSE) is a novel technique that supports enzyme-free cell detachment in the shape of a sheet-like structure. Compared with the traditional method of enzymatic digestion, products harvested by this technique retain extracellular matrix (ECM) secreted by cells as well as cell-matrix and intercellular junctions established during in vitro culture. Herein, we discussed the current status and recent progress of CSE in basic research and clinical application by reviewing relevant articles that have been published, hoping to provide a reference for the development of CSE in the field of stem cells and regenerative medicine.

Endoscopic Submucosal Dissection for Esophageal Cancer: Current and Future

Endoscopic submucosal dissection (ESD) has been widely used to treat superficial esophageal cancer. The advantages of esophageal ESD include a high en bloc resection rate and accurate pathological diagnosis. It enables local resection of the primary tumor and accurate identification of the risk factors for lymph node metastasis, including depth, vascular invasion, and types of invasion. Even in cases with clinical T1b-SM cancer, ESD and additional treatment can achieve radical cure, depending on the risk of lymph node metastasis. Esophageal ESD will be increasingly vital in minimally invasive and effective esophageal cancer treatment. This article describes the current status and prospects of esophageal ESD.

Tissue Engineering for Gastrointestinal and Genitourinary Tracts

The gastrointestinal and genitourinary tracts share several similarities. Primarily, these tissues are composed of hollow structures lined by an epithelium through which materials need to flow with the help of peristalsis brought by muscle contraction. In the case of the gastrointestinal tract, solid or liquid food must circulate to be digested and absorbed and the waste products eliminated. In the case of the urinary tract, the urine produced by the kidneys must flow to the bladder, where it is stored until its elimination from the body. Finally, in the case of the vagina, it must allow the evacuation of blood during menstruation, accommodate the male sexual organ during coitus, and is the natural way to birth a child. The present review describes the anatomy, pathologies, and treatments of such organs, emphasizing tissue engineering strategies.

Advances in the application of regenerative medicine in prevention of post-endoscopic submucosal dissection for esophageal stenosis

Endoscopic submucosal dissection (ESD) is a curative treatment for superficial esophageal cancer with distinct advantages. However, esophageal stenosis after ESD remains a tough problem, especially after large circumferential proportion of esophageal mucosa is removed, which limits the wide use of ESD, especially in circumferential lesions. In this scenario, preventive procedures are highly recommended against post-ESD esophageal stenosis. However, the efficacy and safety of traditional prophylactic methods (steroids, metal and biodegradable stents, balloon dilation, radial incision, etc.) are not satisfactory and novel strategies need to be developed. Regenerative medicine has been showing enormous potential in the reconstruction of organs including the esophagus. In this review, we aimed to describe the current status of regenerative medicine in prevention of post-ESD esophageal stenosis. Cell injection, cell sheet transplantation, and extracellular matrix implantation have been proved effective. However, numerous obstacles still exist and further studies are necessary.

Regenerative medicine for childhood gastrointestinal diseases

Several paediatric gastrointestinal diseases result in life-shortening organ failure. For many of these conditions, current therapeutic options are suboptimal and may not offer a cure. Regenerative medicine is an inter-disciplinary field involving biologists, engineers, and clinicians that aims to produce cell and tissue-based therapies to overcome organ failure. Exciting advances in stem cell biology, materials science, and bioengineering bring engineered gastrointestinal cell and tissue therapies to the verge of clinical trial. In this review, we summarise the requirements for bioengineered therapies, the possible sources of the various cellular and non-cellular components, and the progress towards clinical translation of oesophageal and intestinal tissue engineering to date.

Novel therapies using cell sheets engineered from allogeneic mesenchymal stem/stromal cells

Mesenchymal stem/stromal cells (MSCs) have long been recognized to help regenerate tissues, by exploiting their intrinsic potentials for differentiation and secretion of therapeutic paracrine factors together with feasibility for cell banking. These unique MSC properties are attractive to provide effective new cell-based therapies for unmet medical needs. Currently, the infusion of suspended MSCs is accepted as a promising therapy to treat systemic inflammatory diseases. However, low cell engraftment/retention in target organs and off-target entrapment using conventional cell infusion must be improved to provide reliable localized disease treatments. Cell sheet technology offers an alternative: three-dimensional (3D) tissue-like structures can be harvested from culture using mild temperature reduction, and transplanted directly onto target tissue sites without suturing, yielding stable cell engraftment and prolonged cell retention in situ without off-target losses. Engineered MSC sheets directly address two major cell therapy strategies based on their therapeutic benefits: (1) tissue replacements based on mult-ilineage differentiation capacities, focusing on cartilage regeneration in this review, and (2) enhancement of tissue recovery via paracrine signaling, employing their various secreted cytokines to promote neovascularization. MSCs also have production benefits as a promising allogeneic cell source by exploiting their reliable proliferative capacity to facilitate expansion and sustainable cell banking for off-the-shelf therapies. This article reviews the advantages of both MSCs as allogeneic cell sources in contrast with autologous cell sources, and allogeneic MSC sheets engineered on thermo-responsive cell dishes as determined in basic studies and clinical achievements, indicating promise to provide robust new cell therapies to future patients.

Extracellular vesicles from adipose stromal cells combined with a thermoresponsive hydrogel prevent esophageal stricture after extensive endoscopic submucosal dissection in a porcine model

In this study, we investigated the combination of extracellular (nano) vesicles (EVs) from pig adipose tissue-derived stromal cells (ADSCs) and a thermoresponsive gel, Pluronic® F-127 (PF-127), to prevent stricture formation after endoscopic resection in a porcine model. ADSC EVs were produced at a liter scale by a high-yielding turbulence approach from ADSCs 3D cultured in bioreactors and characterized in terms of size, morphology and membrane markers. The thermoresponsive property of the PF-127 gel was assessed by rheology. The pro-regenerative potency of ADSC EVs was investigated ex vivo in esophageal biopsies under starvation. In vivo tests were performed in a porcine model after extended esophageal endoscopic mucosal dissection (ESD). Pigs were randomized into 3 groups: control (n = 6), gel (n = 6) or a combination of 1.45 × 1012 EVs + gel (n = 6). Application of gel ± EVs was performed just after ESD with a follow-up finalized on day 21 post-ESD. There was a trend towards less feeding disorder in the EV + gel group in comparison with the gel and the control groups (16.67% vs. 66.7% vs. 83.33%, respectively) but without reaching a statistically significant difference. A significant decrease in the esophageal stricture rate was confirmed by endoscopic, radiological and histological examination for the EV + gel group. A decrease in the mean fibrosis area and larger regenerated muscularis mucosae were observed for the EV + gel group. In summary, the application of EVs + gel after extended esophageal endoscopic resection succeeded in preventing stricture formation with an anti-fibrotic effect. This nano-therapy may be of interest to tackle an unmet medical need considering that esophageal stricture is the most challenging delayed complication after extended superficial cancer resection by endoscopy.

Circumferential esophageal replacement by a decellularized esophageal matrix in a porcine model

BACKGROUND

Tissue engineering is an attractive alternative to conventional esophageal replacement techniques using intra-abdominal organs which are associated with a substantial morbidity. The objective was to evaluate the feasibility of esophageal replacement by an allogenic decellularized esophagus in a porcine model. Secondary objectives were to evaluate the benefit of decellularized esophagus recellularization with autologous bone marrow mesenchymal stromal cells and omental maturation of the decellularized esophagus.

METHODS

Eighteen pigs divided into 4 experimental groups according to mesenchymal stromal cells recellularization and omental maturation underwent a 5-cm long circumferential replacement of the thoracic esophagus. Turbo green florescent protein labelling was used for in vivo mesenchymal stromal cells tracking. The graft area was covered by a stent for 3 months. Clinical and histologic outcomes were analyzed over a 6-month period.

RESULTS

The median follow-up was 112 days [5; 205]. Two animals died during the first postoperative month, 2 experienced an anastomotic leakage, 13 experienced a graft area stenosis following stent migration of which 3 were sacrificed as initially planned after successful endoscopic treatment. The stent could be removed in 2 animals: the graft area showed a continuous mucosa without stenosis. After 3 months, the graft area showed a tissue specific regeneration with a mature epithelium and muscular cells. Clinical and histologic results were similar across experimental groups.

CONCLUSION

Circumferential esophageal replacement by a decellularized esophagus was feasible and allowed tissue remodeling toward an esophageal phenotype. We could not demonstrate any benefit provided by the omental maturation of the decellularized esophagus nor its recellularization with mesenchymal stromal cells.

Allogeneic epithelial cell sheet transplantation for preventing esophageal stricture after circumferential ESD in a porcine model: preliminary results

OBJECTIVES

Circumferential endoscopic submucosal dissection (ESD) for large lesions induces severe stricture, requiring subsequent treatment. We aimed to evaluate the efficacy of allogeneic epithelial cell sheet transplantation in preventing esophageal stricture after circumferential ESD in a porcine model.

MATERIALS AND METHODS

A total of 15 conventional pigs underwent a 4 cm long circumferential ESD in the mid-esophagus. Out of these animals, 11 were immediately subjected to allogeneic oral mucosal cell sheet transplantation at the resection site, whereas four pigs underwent circumferential ESD only. We performed upper endoscopy 1 and 2 weeks after ESD and assessed the degree of esophageal stricture and histologic characteristics.

RESULTS

Dysphagia scores and weight change ratios recorded 1 and 2 weeks after ESD did not differ between the two groups. The stricture rate 2 weeks after ESD was 100% in the control group and 90.9% in the cell sheet group (p = 1.000). The median mucosal constriction rates of the control and cell sheet groups were 73.5% (range 63.0-80.0%) and 53.8% (37.5-73.3%, p = .018), respectively. With regard to microscopic measurements, the length of re-epithelialization was greater in the cell sheet group than in the control group (2,495 µm vs. 369 µm, p = .008). Median fibrosis thickness and degree of muscle damage were not significantly different between groups.

CONCLUSIONS

Although allogeneic epithelial cell sheet transplantation showed greater re-epithelialization and less mucosal constriction of post-ESD ulcers, it was not sufficiently effective in preventing post-ESD stricture.

Progress of esophageal stricture prevention after endoscopic submucosal dissection by regenerative medicine and tissue engineering

Endoscopic submucosal dissection (ESD) has been widely accepted as an effective treatment for early esophageal cancer. However, post-ESD esophageal stricture remains a thorny issue. We herein review many strategies for preventing post-ESD esophageal stricture, as well as discuss their strengths and weaknesses. These strategies include pharmacological prophylaxis, esophageal stent and tissue engineering and regenerative medicine treatment. In this review, we summarize these studies and discuss the underlying progress and future directions of tissue engineering and regenerative medicine treatment.

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.

Strategies for treating oesophageal diseases with stem cells

There is a wide range of oesophageal diseases, the most general of which are inflammation, injury and tumours, and treatment methods are constantly being developed and updated. With an increasingly comprehensive understanding of stem cells and their characteristics of multilineage differentiation, self-renewal and homing as well as the combination of stem cells with regenerative medicine, tissue engineering and gene therapy, stem cells are playing an important role in the treatment of a variety of diseases. Mesenchymal stem cells have many advantages and are most commonly applied; however, most of these applications have been in experimental studies, with few related clinical trials for comparison. Therefore, the methods, positive significance and limitations of stem cells in the treatment of oesophageal diseases remain incompletely understood. Thus, the purpose of this paper is to review the current literature and summarize the efficacy of stem cells in the treatment of oesophageal diseases, including oesophageal ulceration, acute radiation-induced oesophageal injury, corrosive oesophageal injury, oesophageal stricture formation after endoscopic submucosal dissection and oesophageal reconstruction, as well as gene therapy for oesophageal cancer.

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.

Fabrication of Functional Cell Sheets with Human Thyrocytes from Non-Tumorous Thyroid Tissue

Background

Engineered cell sheet transplantation has been considered an alternative physiological therapy for endocrine disorders. In this study, we attempted to fabricate functional human thyroid cell sheets using the engineering technology by culturing primary thyrocytes in free-feeder monolayers and assessed their proliferation and function in two different media.

Methods

The non-tumorous tissues (approximately 2 g) were dissected during surgery. Primary human thyroid cells were isolated by mechanical dispersion and treatment with isolation solution. The cells were cultured on tissue culture dishes or temperature-responsive culture dishes to induce the formation of detached cell sheets.

Results

Primary thyroid cells isolated from nine patients were positive for thyroid transcription factor 1, thyroglobulin (TG) and cytokeratin 7. Cell sheets with follicles were fabricated by cells incubated in both Dulbecco's Modified Eagle Medium (DMEM) and hepatocyte-defined medium (HDM) culture medium. The diameter and thickness of sheets fabricated in HDM were larger and thicker than those fabricated from DMEM. Furthermore, the cells incubated in HDM secreted higher levels of fT3 and fT4 than those incubated in DMEM. The thyroid peroxidase and TG mRNA of cells maintained in HDM were higher than those in cells maintained in DMEM.

Conclusion

HDM appears suitable as a culture medium for maintaining primary thyrocytes and fabricating functional cell sheets. These in vitro findings may contribute to the development of appropriate culture conditions for human thyrocytes as well as engineered functional cell sheets.

Evaluating the effect of injecting triamcinolone acetonide in two sessions for preventing esophageal stricture after endoscopic submucosal dissection

Background and study aims  Several previous reports indicate that endoscopic injection of triamcinolone acetonide (TA) after widespread endoscopic submucosal dissection (ESD) is effective for preventing esophageal stricture. We investigated the efficacy of injecting TA in two sessions for preventing stricture formation post-ESD. Patients and methods  Sixty-six consecutive patients with widespread mucosal defects that affected more than three-fourths of the circumference of the esophagus were included. The study group (n = 40) received TA injections over two sessions: immediately after and 14 days after ESD. The control group (n = 26) did not receive a TA injection. This study was performed retrospectively against historical controls. The primary endpoint of this study was frequency of stricture after TA injection. The secondary endpoint was number of required endoscopic balloon dilations (EBDs) after TA injection. Results  The post-ESD stricture rate among patients who had subcircumferential mucosal defects was 45.7 % in the study group (16/35 patients), which was significantly lower than the rate of 73.9 % in the control group (17/23 patients; P  = 0.031). The number of EBD procedures required was significantly lower in the study group (median 0, range 0 - 7) than in the control group (median 4, range 0 - 20; P  < 0.001). There was no significant difference between the study and control groups among the patients who had full circumferential mucosal defects. Conclusion  This study showed that performing two sessions of TA injection is an effective and safe treatment for prevention of esophageal stricture following subcircumferential ESD.

Prevention of esophageal stricture after endoscopic resection

Stricture formation after esophageal endoscopic resection has a negative impact on patients' quality of life because it causes dysphagia and requires multiple endoscopic dilations. Various methods by which to prevent stricture have recently been developed and reported. Among these methods, local steroid injection is the most commonly used and is currently considered the standard method for noncircumferential resection. However, local steroid injection has a limited effect on circumferential resection. Thus, oral steroid administration is used for such cases because it may have a stronger effect than local injection. Steroid treatment, both by local injection and oral administration, is effective and low-cost; however, it may cause fragility of the esophageal wall, resulting in adverse events such as perforation during balloon dilatation. Many innovative approaches have been developed, such as tissue-shielding methods with polyglycolic acid, tissue engineering approaches with autologous oral mucosal epithelial cell sheet transplantation, and stent insertion. These methods may be promising, but they are limited by a scarcity of data. Further investigations are needed to confirm the efficacy of these methods.

Autologous Flap Transfer for Esophageal Stricture Prevention After Endoscopic Submucosal Dissection in a Porcine Model

BACKGROUND

Esophageal stricture caused by endoscopic submucosal dissection for a mucosal defect that covers more than three quarters of the circumference of the esophagus has a high incidence. To date, no method for preventing such strictures has been widely recognized as effective in clinical practice.

AIMS

We examined whether esophageal stricture caused by circumferential endoscopic submucosal dissection could be prevented by autologous flap transfer.

METHODS

Six pigs (N = 6) underwent circumferential esophageal endoscopic submucosal dissection under general anesthesia. For animals in the flap group (N = 3), an autologous flap was constructed and then placed at the resection site and secured with metal clips. Animals in the control group (N = 3) underwent endoscopic submucosal dissection only. Endoscopy was performed 3 weeks postoperative to evaluate the effects of flap transfer.

RESULTS

Animals in the flap group gained more weight than animals in the control group. At 3 weeks postoperative, animals in the flap group developed clinically slight stricture; in these animals, an endoscope could be passed through the stricture with slight resistance. In contrast, in the control group, significant stricture was observed, and the stricture was difficult to cross with an endoscope.

CONCLUSION

Autologous flap transfer after circumferential esophageal endoscopic submucosal dissection is a novel approach that remarkably decreases the degree of esophageal stricture that arises.

Transplantation of Adipose Tissue-Derived Stem Cell Sheet to Reduce Leakage After Partial Colectomy in A Rat Model

Anastomotic leakage is a disastrous complication after colorectal surgery. Although current methods for leakage prevention have different levels of clinical efficacy, they are until now imperfect solutions. Stem cell therapy using ASC sheets could provide a solution to this problem. ASCs are considered as promising candidates for promoting tissue healing because of their trophic and immunomodulatory properties. Here, we provide methods to produce high-density ASC sheets, that are transplanted onto a colorectal anastomosis in a rat model to reduce the leakage. ASCs formed cell sheets in thermo-responsive culture dishes that could be easily detached. On the day of the transplantation, a partial colectomy with a 5-suture colorectal anastomosis was performed. Animals were immediately transplanted with 1 ASC sheet per rat. ASC sheets adhered spontaneously to the anastomosis without any glue, suture, or any biomaterial. Animal groups were sacrificed 3 and 7 days postoperatively. Compared to transplanted animals, the incidence of anastomotic abscesses and leakage was higher in control animals. In our model, the transplantation of ASC sheets after colorectal anastomosis was successful and associated with a lower leakage rate.

Esophageal tissue engineering: from bench to bedside

For various esophageal diseases, the search for alternative techniques for tissue repair has led to significant developments in basic and translational research in the field of tissue engineering. Applied to the esophagus, this concept is based on the in vitro combination of elements judged necessary for in vivo implantation to promote esophageal tissue remodeling. Different methods are currently being explored to develop substitutes using cells, scaffolds, or a combination of both, according to the severity of lesions to be treated. In this review, we discuss recent advances in (1) cell sheet technology for preventing stricture after extended esophageal mucosectomy and (2) full-thickness circumferential esophageal replacement using tissue-engineered substitutes.

Re-thinking our understanding of immunity: Robustness in the tissue reconstruction system

Robustness, understood as the maintenance of specific functionalities of a given system against internal and external perturbations, is pervasive in today's biology. Yet precise applications of this notion to the immune system have been scarce. Here we show that the concept of robustness sheds light on tissue repair, and particularly on the crucial role the immune system plays in this process. We describe the specific mechanisms, including plasticity and redundancy, by which robustness is achieved in the tissue reconstruction system (TRS). In turn, tissue repair offers a very important test case for assessing the usefulness of the concept of robustness, and identifying different varieties of robustness.

Progress on the Prevention of Esophageal Stricture after Endoscopic Submucosal Dissection

Endoscopic submucosal dissection (ESD) has been widely accepted as an effective, minimally invasive treatment for superficial esophageal cancers. However, esophageal stricture often occurs in patients with large mucosal defects after ESD. In this review, we discuss various approaches recently researched to prevent esophageal strictures after ESD. These approaches can be classified as pharmacological treatments, esophageal stent treatments, and tissue engineering approaches. Most of the preventive approaches still have their limitations and require further research. With the improvement of current therapies, ESD can be more widely utilized as a minimally invasive treatment with minimal complications.

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.

Acellular dermal matrix for esophageal stricture prevention after endoscopic submucosal dissection in a porcine model

BACKGROUND AND AIMS

Endoscopic submucosal dissection (ESD) is considered an effective treatment for early esophageal cancer and precancerous lesions. Esophageal stenosis is closely associated with quasi-circumferential ESD. We examined whether post-ESD esophageal stricture can be prevented by grafting an acellular dermal matrix (ADM) membrane.

METHODS

Fourteen Bama miniature pigs were randomly divided into an ADM group (n = 7) and a control group (n = 7). Semicircumferential ESD was performed at the distal esophagus in all animals, and in the ADM group an ADM patch graft was placed at the resection site and secured innovatively with metal clips. Animals in the control group underwent ESD only. Endoscopy was performed at 3 days, 1 week, 2 weeks, and 4 weeks post-ESD, and fluoroscopy was performed at 4 weeks for assessment of the degree of stenosis, after which the remodeled esophageal tissues were excised for histologic analysis.

RESULTS

No animals in the ADM group developed clinically significant esophageal stenosis, whereas 42.8% (3/7) in the control group did. The degree of stenosis was severe in the control group (39.8% vs 17.2%, respectively; P = .01). Animals in the ADM group had less feeding difficulty and lost less weight (-.9 kg vs -4.1 kg, respectively; P = .007). Histologically, complete mucosal epithelium, slight local inflammation, and organized collagenous fibers were observed in the ADM group.

CONCLUSIONS

ADM patch graft appears, after short-term observation, to be a potentially useful new treatment strategy for prevention of esophageal stricture after ESD. A metal clip fixation technique is effective for endoscopic graft attachment.

Oral administration of conditioned medium obtained from mesenchymal stem cell culture prevents subsequent stricture formation after esophageal submucosal dissection in pigs

BACKGROUND AND AIMS

Endoscopic submucosal dissection (ESD) for esophageal cancer often causes postoperative stricture when more than three fourths of the circumference of the esophagus is dissected. Mesenchymal stem cells are a valuable cell source in regenerative medicine, and conditioned medium (CM) obtained from mesenchymal stem cells reportedly inhibits inflammation. In this study we evaluated whether CM could prevent esophageal stricture after ESD.

METHODS

We resected a semi-circumference of pig esophagus by ESD. We prepared CM gel by mixing with 5% carboxymethyl cellulose and endoscopically applied it onto the wound bed immediately after ESD and on days 8 and 15 (weekly CM group) or administered it orally from days 1 to 4 (daily CM group). We also injected triamcinolone acetonide into the remaining submucosa immediately after ESD (steroid group). We killed the pigs on day 8 or day 22 to measure the stricture rate and to perform histologic analysis.

RESULTS

Stricture rate in weekly and daily CM groups and steroid groups were significantly lower than in the control group on day 22. Moreover, CM significantly attenuated the number of activated myofibroblasts and fiber thickness on day 22. CM also significantly decreased the infiltration of neutrophils and macrophages compared with the control group on day 8.

CONCLUSIONS

CM gel prevents esophageal stricture formation by suppressing myofibroblast activation and fibrosis after the infiltration of neutrophils and macrophages. Oral administration of CM gel is a promising treatment for the prevention of post-ESD stricture.

Adipose Tissue-Derived Stem Cell Sheet Application for Tissue Healing In Vivo: A Systematic Review

Adipose tissue-derived stem cells (ASCs) are known to be tissue-healing promoters due to their cellular plasticity and secretion of paracrine factors. Cultured ASC sheets provide a novel method of ASC application and can retain ASCs at the targeted tissue. The purpose of this systematic review is to evaluate preclinical studies using ASC sheet transplantation therapy for promoting tissue healing. First, we searched databases to identify studies of ASC sheet therapy in different experimental animal models, and then determined the quality score of studies using SYRCLE's risk bias tool. A total of 18 included studies examined the role of ASC sheets on tissue healing and function in models for myocardial infarction, dilated cardiomyopathy, full-thickness skin wounds, hind limb ischemia, esophageal strictures, and oral ulcers. ASC sheet application after myocardial infarction improved survival rate, cardiac function, and capillary density and reduced the extent of fibrosis. Application of ASC sheets to a full-thickness skin wound decreased the wound size and stimulated wound maturation. In the hind limb ischemia model, ASC sheet application improved limb perfusion and capillary density, and decreased the amount of ischemic tissue and inflammation. ASC sheet application to mucosal wounds of the digestive tract accelerated wound healing and decreased the degree of stricture and fibrosis. Taken together, transplanted ASC sheets had a positive effect on tissue healing and reconstruction in these preclinical studies. The reported favorable effects of ASC sheet therapy in various tissue healing applications may be implemented in future translational studies. It is suggested that future preclinical animal model studies of ASC sheet therapy should concern standardization of culture techniques and investigate the mechanisms of action. In addition, clearly indicated experimental setups according to the SYRCLE's guidelines should improve study quality and validity.

Effects of adipose stem cell sheets on colon anastomotic leakage in an experimental model: Proof of principle

The most dreaded complication of colorectal surgery is anastomotic leakage. Adipose tissue-derived stem cell sheets (ASC sheets) prepared from temperature-responsive culture surfaces can be easily transplanted onto tissues. These sheets are proposed to improve cell transplant efficiency and enhance wound healing. The aim of this study was to investigate whether application of ASC sheets could prevent leakage of sutured colorectal anastomoses. Insufficient suturing of colorectal anastomoses was performed in Wistar rats to create a colorectal anastomotic leakage model. Rats were randomized to ASC sheet application or control group. Leakage, abscess formation, adhesion formation, anastomotic bursting pressure (ABP), and histology were evaluated on postoperative day 3 or 7. ASC sheet application significantly reduced anastomotic leakage compared to controls, without increased adhesion formation. ASC sheet transplantation resulted in more CD3+ T-cells and CD163+ anti-inflammatory macrophages at the anastomotic site than the control group. ABP, vessel density and collagen deposition were not different between groups. Using cell sheet technology, we generated ASC sheets that prevented disruption of sutured colorectal anastomoses as shown by reduced leakage. Increased numbers of anti-inflammatory macrophages and T-cells might have contributed to this positive effect.

ADSC-sheet Transplantation to Prevent Stricture after Extended Esophageal Endoscopic Submucosal Dissection

In past years, the cell-sheet construct has spurred wide interest in regenerative medicine, especially for reconstructive surgery procedures. The development of diversified technologies combining adipose tissue-derived stromal cells (ADSCs) with various biomaterials has led to the construction of numerous types of tissue-engineered substitutes, such as bone, cartilage, and adipose tissues from rodent, porcine, or human ADSCs. Extended esophageal endoscopic submucosal dissection (ESD) is responsible for esophageal stricture formation. Stricture prevention remains challenging, with no efficient treatments available. Previous studies reported the effectiveness of mucosal cell-sheet transplantation in a canine model and in humans. ADSCs are attributed anti-inflammatory properties, local immune modulating effects, neovascularization induction, and differentiation abilities into mesenchymal and non-mesenchymal lineages. This original study describes the endoscopic transplantation of an ADSC tissue-engineered construct to prevent esophageal stricture in a swine model. The ADSC construct was composed of two allogenic ADSC sheets layered upon each other on a paper support membrane. The ADSCs were labeled with the PKH67 fluorophore to allow probe-based confocal laser endomicroscopy (pCLE) monitoring. On the day of transplantation, a 5-cm and hemi-circumferential ESD known to induce esophageal stricture was performed. Animals were immediately endoscopically transplanted with 4 ADSC constructs. The complete adhesion of the ADSC constructs was obtained after 10 min of gentle application. Animals were sacrificed on day 28. All animals were successfully transplanted. Transplantation was confirmed on day 3 with a positive pCLE evaluation. Compared to transplanted animals, control animals developed severe strictures, with major fibrotic tissue development, more frequent alimentary trouble, and reduced weight gain. In our model, the transplantation of allogenic ADSCs, organized in double cell sheets, after extended ESD was successful and strongly associated with a lower esophageal stricture rate.