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

Bioelectret Materials and Their Bioelectric Effects for Tissue Repair: A Review

Biophysical and clinical medical studies have confirmed that biological tissue lesions and trauma are related to the damage of an intrinsic electret (i.e., endogenous electric field), such as wound healing, embryonic development, the occurrence of various diseases, immune regulation, tissue regeneration, and cancer metastasis. As exogenous electrical signals, such as conductivity, piezoelectricity, ferroelectricity, and pyroelectricity, bioelectroactives can regulate the endogenous electric field, thus controlling the function of cells and promoting the repair and regeneration of tissues. Materials, once polarized, can harness their inherent polarized static electric fields to generate an electric field through direct stimulation or indirect interactions facilitated by physical signals, such as friction, ultrasound, or mechanical stimulation. The interaction with the biological microenvironment allows for the regulation and compensation of polarized electric signals in damaged tissue microenvironments, leading to tissue regeneration and repair. The technique shows great promise for applications in the field of tissue regeneration. In this paper, the generation and change of the endogenous electric field and the regulation of exogenous electroactive substances are expounded, and the latest research progress of the electret and its biological effects in the field of tissue repair include bone repair, nerve repair, drug penetration promotion, wound healing, etc. Finally, the opportunities and challenges of electret materials in tissue repair were summarized. Exploring the research and development of new polarized materials and the mechanism of regulating endogenous electric field changes may provide new insights and innovative methods for tissue repair and disease treatment in biological applications.

Preparation and Structure-Property Relationship Study of Piezoelectric-Conductive Composite Polymer Nanofiber Materials for Bone Tissue Engineering

This study aimed to develop Janus-, cross-network-, and coaxial-structured piezoelectric-conductive polymer nanofibers through electrospinning to mimic the piezoelectricity of bone and facilitate the conduction of electrical signals in bone tissue repair. These nanofibers were constructed using the piezoelectric polymer polyvinylidene fluoride, and the conductive fillers reduced graphene oxide and polypyrrole. The influence of structural features on the electroactivity of the fibers was also explored. The morphology and components of the various structural samples were characterized using SEM, TEM, and FTIR. The electroactivity of the materials was assessed with a quasi-static d33 meter and the four-probe method. The results revealed that the piezoelectric-conductive phases were successfully integrated. The Janus-structured nanofibers demonstrated the best electroactivity, with a piezoelectric constant d33 of 24.5 pC/N and conductivity of 6.78 × 10-2 S/m. The tensile tests and MIP measurements showed that all samples had porosity levels exceeding 70%. The tensile strength of the Janus and cross-network structures exceeded that of the periosteum (3-4 MPa), with average pore sizes of 1194.36 and 2264.46 nm, respectively. These properties indicated good mechanical performance, allowing material support while preventing fibroblast invasion. The CCK-8 and ALP tests indicated that the Janus-structured samples were biocompatible and significantly promoted the proliferation of MC3T3-E1 cells.

New hope for esophageal stricture prevention: A prospective single-center trial on acellular dermal matrix

BACKGROUND

Given the high incidence of esophageal cancer in China, an increasing number of patients there are undergoing endoscopic mucosal dissection (ESD). Although the 5-year survival rate after ESD can exceed 95%, esophageal stricture, the most common and serious postoperative complication, affects the long-term prognosis of patients and the quality of life. Autologous mucosal grafts have proven to be successful in preventing stricture after ESD for early esophageal cancer.

AIM

To examine the viability of acellular dermal matrix (ADM) as an alternative to autologous mucosa for the prevention of stricture after ESD.

METHODS

This is a prospective, single-center, controlled study. Consecutive patients who underwent ESD surgery and were willing to undergo autologous mucosal transplantation were recruited between January 1 and December 31, 2017. Consecutive patients who underwent ESD surgery and were willing to undergo ADM transplantation were recruited between January 1 to December 31, 2019. A final three-year follow-up of patients who received transplants was conducted.

RESULTS

Based on the current incidence of esophageal stricture, the sample size required for both the autologous mucosal graft group and the ADM group was calculated to be 160 cases. Due to various factors, a total of 20 patients with autologous mucosal grafts and 25 with ADM grafts were recruited. Based on the inclusion exclusion and withdrawal criteria, 9 patients ultimately received autologous mucosal grafts and completed the follow-up, while 11 patients received ADM grafts and completed the follow-up. Finally, there were 2 cases of stenosis in the autologous mucosal transplantation group with a stenosis rate of 22.22% and 2 cases of stenosis in the ADM transplantation group with a stenosis rate of 18.18%, with no significant difference noted between the groups (P = 0.94).

CONCLUSION

In this prospective, single-center, controlled trial, we compared the effectiveness of autologous mucosa transplantation and ADM for the prevention of esophageal stricture. Due to certain condition limitations, we were unable to recruit sufficient subjects meeting our target requirements. However, we implemented strict inclusion, exclusion, and withdrawal criteria and successfully completed three years of follow-up, resulting in valuable clinical insights. Based on our findings, we hypothesize that ADM may be similarly effective to autologous mucosal transplantation in the prevention of esophageal stricture, offering a comparable and alternative approach. This study provides a new therapeutic idea and direction for the prevention of esophageal stricture.

Prevention of esophageal stricture after endoscopic submucosal dissection of squamous cell carcinoma using a 20-French nasogastric tube combined with oral steroid administration

BACKGROUND

Esophageal stricture is a major complication after esophageal endoscopic submucosal dissection (ESD) and when the mucosal defect exceeds 3/4 of the circumference. Various preventive methods have been reported to prevent stenosis. However, in the case of circumferential ESD, there is no way to prevent luminal stenosis effectively. This retrospective study aimed to evaluate the efficacy of 20-French nasogastric tubes (NGT) combined with oral steroids for the prevention of esophageal stricture after endoscopic submucosal dissection.

METHODS

Between January 2012 and December 2021, we enrolled 57 patients with post-ESD mucosal defects exceeding 3/4 of the esophageal circumference. Of them, the initial seven patients received oral steroid therapy and the subsequent 50 patients received 20-French NGT placements combined with oral steroid therapy. We retrospectively evaluated the rates of strictures and refractory strictures and explored risk factors for strictures with 20-French NGT.

RESULTS

The overall esophageal stricture rate was 42.1% (24/57). In the noncircumferential group, the esophageal stricture rate in patients with only oral steroid to prevent esophageal stricture was 85.7% (6/7), while the esophageal stricture rate was only 4.3% (1/23) in those with 20-French NGT placements and oral steroid. All 27 patients with whole-circumferential resection received 20-French NGT placements. The stricture rate was 63.0% (17/27), and the refractory stricture rate was 17.6% (3/27).

CONCLUSION

Using a 20-French NGT placement combined with oral steroid administration is an easy and safe alternative to prevent esophageal stricture after ESD, especially for patients with noncircumferential mucosal defects. Further studies are needed to develop an effective stricture prevention method for post-ESD whole-circumferential mucosal defects of the esophagus.

Complete Circumferential Endoscopic Submucosal Dissection for Esophageal Cancer Leaving an Island of Normal Mucosa

Esophageal stricture caused by complete circumferential endoscopic submucosal dissection (ESD) of extensive esophageal squamous cell carcinoma (ESCC) is a major concern and can result in a low quality of life. Normal mucosa may remain within a complete circumferential lesion of ESCC in some cases. We herein report a case of ESCC in which a complete circumferential lesion was treated with ESD while leaving an island of normal mucosa within it. This case demonstrates that preserving areas of normal mucosa within lesions during complete circumferential ESD is not technically difficult and may be an effective measure for preventing esophageal stricture.

Engineering of MSCs sheet for the prevention of myocardial ischemia and for left ventricle remodeling

Tissue engineering combines cell biology and material science to construct tissues or organs for disease modeling, drug testing, and regenerative medicine. The cell sheet is a newly developed tissue engineering technology that has brought about scaffold-free tissue and shows great application potential. In this review, we summarized recent progress and future possibilities in preclinical research into and clinical applications of cell sheets fabricated by differing cell types from various sources for cardiac tissue repair, and the manufacturing strategies and promising application potential of 3D cell-dense tissue constructed from cell sheets. Special attention was paid to the mechanisms of mesenchymal stem cell (MSC) sheets in the prevention of myocardial ischemia and left ventricle remodeling. Comparing MSCs sheets with other types of cell sheets and 3D cardiac tissues, engineering tissues' potential safety and effectiveness concerns were also discussed.

BMP-2/TGF-β1 gene insertion into ligament-derived stem cells sheet promotes tendon-bone healing in a mouse

Bone morphogenetic protein-2 (BMP-2) and transforming growth factor-β1 (TGF-β1) reportedly induce the osteogenic and tenogenic differentiation of anterior cruciate ligament (ACL)-derived stem cells (LDSCs), respectively. However, few studies have investigated the effect of BMP-2/TGF-β1 on the differentiation of LDSC. We developed a BMP-2/TGF-β1 gene insertion into an LDSC cell sheet that promotes tendon-bone healing in a mouse ACL reconstruction (ACLR) model. CD34⁺ LDSCs were isolated from human ACL stump tissues, virally transduced to express BMP-2 or TGF-β1, and then embedded within cell sheets. All mice underwent ACLR using an autograft wrapped with a cell sheet and were randomly divided into three groups: BMP-2-, TGF-β1-, and BMP-2/TGF-β1-transduced. At 4 and 8 weeks, tendon-bone healing was evaluated by micro-CT, biomechanical test, and histological analysis. BMP-2 and TGF-β1 promoted the osteogenic and tenogenic differentiation of LDSC in vitro. BMP-2/TGF-β1-transduced LDSC sheet application contributed to early improvement in mean failure load and graft stiffness, accelerated maturation of the tendon-bone junction, and inhibited bone tunnel widening. Furthermore, reduced M1 macrophage infiltration and a higher M2 macrophage percentage were observed in the BMP-2/TGF-β1-transduced LDSC group. This work demonstrated that BMP-2 and TGF-β1 promoted CD34⁺ LDSCs osteogenic and tenogenic differentiation in vitro and in vivo, which accelerated the tendon-bone healing after ACLR using autografts wrapped with cell sheets in a mouse model.

Transplantation of hybrid adipose-derived stem cell sheet with autologous peritoneum: An in vivo feasibility study

Introduction

In regenerative medicine, cell sheet engineering has various advantages, including the retention of cells at the transplantation site for a longer period and the local delivery of growth factors and cytokines. Adipose-derived stem cell (ASC) is widely used owing to their various functions such as wound healing, immunomodulation, and nerve regeneration, in addition to their ability to differentiate into adipocytes, chondrocytes, and osteoblasts. ASC sheet generated using cell sheet engineering is considered effective in preventing anastomotic leakage, a serious postoperative complication in gastrointestinal surgery. However, the ASC sheet is too soft, thin, and brittle to handle with laparoscopic forceps during the operation. Therefore, we considered using the peritoneum, which is stiff and easy to collect while operating, as an alternative support. In this study, we explored the feasibility of using the peritoneum as a support for the precise transplantation of ASC sheets during surgery.

Methods

ASCs were isolated from the subcutaneous fat of the inguinal region of Sprague-Dawley (SD) transgenic rats expressing green fluorescent protein. ASCs were cultured until passage 3, seeded in temperature-responsive culture dishes, and the resulting ASC sheet was harvested at more than 80% confluency. Non-transgenic SD rats were used for transplant experiments. The wall peritoneum was harvested from SD rats following laparotomy, and hybrid adipose-derived stem cell (HASC) sheet was prepared by laminating the peritoneum with ASC sheet. The cell sheets were transplanted on the backs of SD rats following the incision. On post-transplantation days 3 and 7, the specimens were extracted. ASC and HASC sheets were then compared macroscopically and histopathologically.

Results

HASC sheet transplantation was macroscopically and histopathologically more effective than ASC sheet transplantation. The peritoneum provided sufficient stiffness as a support for precise transplantation.

Conclusion

The newly developed HASC sheet, which combine the advantages of ASC sheet with those of the peritoneum, could be more useful for clinical application than the ASC sheet alone.

The Potential of Cell Sheet Technology for Beta Cell Replacement Therapy

Purpose of Review

Here, we review the use of cell sheet technology using different cell types and its potential for restoring the extracellular matrix microenvironment, perfusion, and immunomodulatory action on islets and beta cells.

Recent Findings

Cell sheets can be produced with different fabrication techniques ranging from the widely used temperature responsive system to the magnetic system. A variety of cells have been used to produce cell sheets including skin fibroblasts, smooth muscle cells, human umbilical vein endothelial cells, and mesenchymal stem cells.

Summary

CST would allow to recreate the ECM of islets which would provide cues to support islet survival and improvement of islet function. Depending on the used cell type, different additional supporting properties like immunoprotection or cues for better revascularization could be provided. Furthermore, CST offers the possibility to use other implantation sites than inside the liver. Further research should focus on cell sheet thickness and size to generate a potential translational therapy.

A potential preventive method for scar stenosis after esophageal endoscopic mucosal resection using human amniotic epithelial cells in a porcine model

Objectives

The current methods employed for esophageal endoscopic mucosal resection (EMR) involve the risk of adverse postprocedural complications. Therefore, this study aimed to develop a new method to prevent stenosis following a resection procedure using human amniotic epithelial cells in a porcine model.

Methods

With the consent of a woman who underwent a cesarean section, amniotic epithelial cells were isolated from the amniotic membrane of the delivered placenta. Six swine were used for this study. Under general anesthesia, four EMRs using cap‐fitted microscope ulcers were performed on each porcine esophagus. Of the four ulcers, the two on the oral side were treated by injecting human amniotic epithelial (AE group) cells, and the remaining two on the anal side were left untreated (control group). One week after the procedure, the swine were sacrificed, and the ulcers were evaluated. The epithelialization rate was calculated by dividing the length of the epithelialized portion of each section by the length of the ulcer, which was determined using an optical microscope. Moreover, the mucosal thickening in each section was measured in terms of diameter.

Results

The epithelialization rate was significantly higher in the AE group than in the control group. Mucosal thickening was not significantly different between the groups.

Conclusions

Transplanting amniotic epithelial cells into the ulcer promoted ulcer epithelialization. Amniotic epithelial cell transplantation is a potential method for the management of ulcer scar stenosis following esophageal endoscopic submucosal dissection.

Engineering Biological Tissues from the Bottom-Up: Recent Advances and Future Prospects

Tissue engineering provides a powerful solution for current organ shortages, and researchers have cultured blood vessels, heart tissues, and bone tissues in vitro. However, traditional top-down tissue engineering has suffered two challenges: vascularization and reconfigurability of functional units. With the continuous development of micro-nano technology and biomaterial technology, bottom-up tissue engineering as a promising approach for organ and tissue modular reconstruction has gradually developed. In this article, relevant advances in living blocks fabrication and assembly techniques for creation of higher-order bioarchitectures are described. After a critical overview of this technology, a discussion of practical challenges is provided, and future development prospects are proposed.

Adipose-Derived Stem Cell Sheets Improve Early Biomechanical Graft Strength in Rabbits After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Although various reconstruction techniques are available for anterior cruciate ligament (ACL) injuries, a long recovery time is required before patients return to sports activities, as the reconstructed ACL requires time to regain strength. To date, several studies have reported use of mesenchymal stem cells in orthopaedic surgery; however, no studies have used adipose-derived stem cell (ADSC) sheets in ACL reconstruction (ACLR).

HYPOTHESIS

ADSC sheet transplantation can improve biomechanical strength of the autograft used in ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 68 healthy Japanese white rabbits underwent unilateral ACLR with a semitendinosus tendon autograft after random enrollment into a control group (no sheet; n = 34) and a sheet group (ADSC sheet; n = 34). At 2, 4, 8, 16, and 24 weeks after surgery, rabbits in each group were sacrificed to evaluate tendon-bone healing using histological staining, micro-computed tomography, and biomechanical testing. At 24 weeks, scanning transmission electron microscopy of the graft midsubstance was performed.

RESULTS

The ultimate failure load for the control and sheet groups, respectively, was as follows: 17.2 ± 5.5 versus 37.3 ± 10.3 (P = .01) at 2 weeks, 28.6 ± 1.9 versus 47.4 ± 10.4 (P = .003) at 4 weeks, 53.0 ± 14.3 versus 48.1 ± 9.3 (P = .59) at 8 weeks, 66.2 ± 9.3 versus 95.2 ± 43.1 (P = .24) at 16 weeks, and 66.7 ± 27.3 versus 85.3 ± 29.5 (P = .39) at 24 weeks. The histological score was also significantly higher in the sheet group compared with the control group at early stages up to 8 weeks. On micro-computed tomography, relative to the control group, the bone tunnel area was significantly narrower in the sheet group at 4 weeks, and the bone volume/tissue volume of the tendon-bone interface was significantly greater at 24 weeks. Scanning transmission electron microscopy at 24 weeks indicated that the mean collagen fiber diameter in the midsubstance was significantly greater, as was the occupation ratio of collagen fibers per field of view, in the sheet group.

CONCLUSION

ADSC sheets improved biomechanical strength, prevented bone tunnel enlargement, and promoted tendon-bone interface healing and graft midsubstance healing in an in vivo rabbit model.

CLINICAL RELEVANCE

ADSC sheets may be useful for early tendon-bone healing and graft maturation in ACLR.

Conductive Polymeric-Based Electroactive Scaffolds for Tissue Engineering Applications: Current Progress and Challenges from Biomaterials and Manufacturing Perspectives

The practice of combining external stimulation therapy alongside stimuli-responsive bio-scaffolds has shown massive potential for tissue engineering applications. One promising example is the combination of electrical stimulation (ES) and electroactive scaffolds because ES could enhance cell adhesion and proliferation as well as modulating cellular specialization. Even though electroactive scaffolds have the potential to revolutionize the field of tissue engineering due to their ability to distribute ES directly to the target tissues, the development of effective electroactive scaffolds with specific properties remains a major issue in their practical uses. Conductive polymers (CPs) offer ease of modification that allows for tailoring the scaffold's various properties, making them an attractive option for conductive component in electroactive scaffolds. This review provides an up-to-date narrative of the progress of CPs-based electroactive scaffolds and the challenge of their use in various tissue engineering applications from biomaterials perspectives. The general issues with CP-based scaffolds relevant to its application as electroactive scaffolds were discussed, followed by a more specific discussion in their applications for specific tissues, including bone, nerve, skin, skeletal muscle and cardiac muscle scaffolds. Furthermore, this review also highlighted the importance of the manufacturing process relative to the scaffold's performance, with particular emphasis on additive manufacturing, and various strategies to overcome the CPs' limitations in the development of electroactive scaffolds.

A Scarless Healing Tale: Comparing Homeostasis and Wound Healing of Oral Mucosa With Skin and Oesophagus

Epithelial tissues are the most rapidly dividing tissues in the body, holding a natural ability for renewal and regeneration. This ability is crucial for survival as epithelia are essential to provide the ultimate barrier against the external environment, protecting the underlying tissues. Tissue stem and progenitor cells are responsible for self-renewal and repair during homeostasis and following injury. Upon wounding, epithelial tissues undergo different phases of haemostasis, inflammation, proliferation and remodelling, often resulting in fibrosis and scarring. In this review, we explore the phenotypic differences between the skin, the oesophagus and the oral mucosa. We discuss the plasticity of these epithelial stem cells and contribution of different fibroblast subpopulations for tissue regeneration and wound healing. While these epithelial tissues share global mechanisms of stem cell behaviour for tissue renewal and regeneration, the oral mucosa is known for its outstanding healing potential with minimal scarring. We aim to provide an updated review of recent studies that combined cell therapy with bioengineering exporting the unique scarless properties of the oral mucosa to improve skin and oesophageal wound healing and to reduce fibrotic tissue formation. These advances open new avenues toward the ultimate goal of achieving scarless wound healing.

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.

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.

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.

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.

Tailored cell sheet engineering using microstereolithography and electrochemical cell transfer

Postoperative adhesion and occlusion remain a serious issue associated with various surgeries, including endoscopic surgery, in which proliferated fibrous tissues stick to adjacent tissues and often cause severe complications. Cell sheet engineering has emerged as an effective approach not only for cell transplantation but also for the treatment of postoperative adhesion and occlusion. However, as the tissues in the body, such as middle ear and small intestine, and typical operative sites are non-flat and spatially complicated, tailored cell sheets with three-dimensional (3D) configurations may lead to widespread use of this approach. In the present study, we used microstereolithography, biocompatible gold plating, and electrochemical cell detachment to achieve this purpose. Various objects with dimensions ranging from millimeter- to micrometer-scale were fabricated with photocurable resin using lab-made equipment for microstereolithography. To coat the fabricated objects with a thin gold layer, conventional cyanide-based gold plating was unusable because it severely damaged almost all cells. Electroless non-cyanide gold plating we prepared was cytocompatible and suitable for electrochemical cell detachment. Cell sheets on the gold-plated substrate could be directly transplanted into a mouse intraperitoneally using electrochemical cell detachment. We further demonstrated that cell sheets grown on gold-coated 3D objects were rapidly detached along with the desorption of electroactive-oligopeptide monolayer and transferred to a surrounding hydrogel. This approach may provide a promising strategy to prepare and directly transplant tailor-made cell sheets with suitable configurations.

Formation of Large Scaffold-Free 3-D Aggregates in a Cell Culture Dish by Ultrasound Standing Wave Trapping

Cellular aggregates that mimic cell-cell interactions in vitro are essential for biological research. This study introduces a method to form large scaffold-free 3-D aggregates in a clinically ubiquitous cell culture dish using kilohertz-order ultrasound standing wave trapping (USWT). We fabricated an aggregate formation system in which a 60-mm dish was set above a Langevin transducer via water. The transducer was excited at 110.8 kHz, and then C2C12 myoblasts were injected into the dish and trapped at the node position of the standing wave. The diameter and thickness of the formed aggregate were 8 and 2.7 mm, respectively, which are larger than those of aggregates formed previously by USWT. Moreover, we confirmed that >94% of cells constituting the aggregates survived 9 h, and the protein expression of cells was not altered significantly. This method can be applied to form aggregates with high functionality, which contributes to the development of biological research methodology.

Thermally-triggered fabrication of cell sheets for tissue engineering and regenerative medicine

Cell transplantation is a promising approach for promoting tissue regeneration in the treatment of damaged tissues or organs. Although cells have conventionally been delivered by direct injection to damaged tissues, cell injection has limited efficiency to deliver therapeutic cells to the target sites. Progress in tissue engineering has moved scaffold-based cell/tissue delivery into the mainstream of tissue regeneration. A variety of scaffolds can be fabricated from natural or synthetic polymers to provide the appropriate culture conditions for cell growth and achieve in-vitro tissue formation. Tissue engineering has now become the primary approach for cell-based therapies. However, there are still serious limitations, particularly for engineering of cell-dense tissues. "Cell sheet engineering" is a scaffold-free tissue technology that holds even greater promise in the field of tissue engineering and regenerative medicine. Thermoresponsive poly(N-isopropylacrylamide)-grafted surfaces allow the fabrication of a tissue-like cell monolayer, a "cell sheet", and efficiently delivers this cell-dense tissue to damaged sites without the use of scaffolds. At present, this unique approach has been applied to human clinical studies in regenerative medicine. Furthermore, this thermally triggered cell manipulation system allows us to produce various types of 3D tissue models not only for regenerative medicine but also for tissue modeling, which can be used for drug discovery. Here, new cell sheet-based technologies are described including vascularization for scaled-up 3D tissue constructs, induced pluripotent stem (iPS) cell technology for human cell sheet fabrication and microfabrication for arranging tissue microstructures, all of which are expected to produce more complex tissues based on cell sheet tissue engineering.

Pathological Process of Prompt Connection between Host and Donor Tissue Vasculature Causing Rapid Perfusion of the Engineered Donor Tissue after Transplantation

The shortage of donors for transplantation therapy is a serious issue worldwide. Tissue engineering is considered a potential solution to this problem. Connection and perfusion in engineered tissues after transplantation is vital for the survival of the transplanted tissue, especially for tissues requiring blood perfusion to receive nutrients, such as the heart. A myocardial cell sheet containing an endothelial cell network structure was fabricated in vitro using cell sheet technology. Transplantation of the three-dimensional (3D) tissue by layering myocardial sheets could ameliorate ischemic heart disease in a rat model. The endothelial cell network in the 3D tissue was able to rapidly connect to host vasculature and begin perfusion within 24 h after transplantation. In this review, we compare and discuss the engineered tissue⁻host vasculature connection process between tissue engineered constructs with hydrogels and cell sheets by histological analysis. This review provides information that may be useful for further improvements of in vivo engineered tissue vascularization techniques.

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.

Endoscopic submucosal dissection for superficial esophageal cancer

Endoscopic submucosal dissection (ESD) has evolved into a viable treatment modality for superficial esophageal cancer. ESD offers a distinct advantage given the ability to perform en bloc resection enabling accurate histopathologic assessment. Data from published literature has established ESD as the preferred option in the treatment of superficial squamous cell carcinoma with complete resection rates of 78-100%, and a low rate recurrence of 0-2.6%. En bloc resection for esophageal SCC is curative for tumors with M1 (intrapethelial) or M2 (invasion into the lamina propria) involvement with no lymphovascular invasion. Tumors that contain lymphovascular invasion or submucosal invasion greater than 200 μm should be treated as advanced carcinomas due to the increased risk of lymph node metastasis. In contrast, the role of ESD in Barrett's esophagus is more limited due to the high rate of efficacy of EMR. A randomized control trial comparing EMR and ESD strategies found a higher R0 resection rate for ESD, but no significant difference in complete remission from neoplasia at 3 month follow up. Endoscopic ultrasound (EUS) has a limited role in the evaluation of superficial esophageal cancer. Alternatively, detailed endoscopic assessment along with magnification endoscopy or narrow band imaging, may provide greater utility than EUS. The most common adverse events of ESD in the esophagus include perforation and stricture. Perforation can often be managed by defect closure along with non-operative conservative management. Steroid administration with either topical or local injection can be effective management in stricture prevention. Continued refinement of ESD technique and innovation will overcome some of the current limitations of ESD and enable curative resection of superficial esophageal cancer as an alternative to invasive surgery.

Preserving the Mucosa to the Maximum Possible Extent for Endoscopic Submucosal Dissection of Subcircumferential Superficial Esophageal Carcinoma

Aim

To show our unique strategy of endoscopic submucosal dissection (ESD) for esophageal squamous cell carcinoma larger than the subcircumference.

Methods

From April 2011, we used a mucosal preservation method called the log bridge (LB) method for the lesion larger than the subcircumference. The patients in whom the circumference of the mucosal defect was 5/6 to <1 were classified into the LB group; those who underwent whole circumferential ESD were classified into the non-LB group. The data were collected retrospectively and were compared between the two groups.

Results

Eighteen patients into the LB group and 7 into the non-LB group were classified. The median number of endoscopic balloon dilation sessions after ESD in the LB group tended to be lower than that in the non-LB group. The mean period until complete epithelialization after ESD was significantly shorter in the LB group. The rates of curative resection were 100% (7/7) in the non-LB group and 61.1% (11/18) in the LB group. However, there was no local recurrence in either group for approximately two years.

Conclusion

In cases involving subcircumferential esophageal lesions, the LB method is useful for achieving rapid healing and might be related to a reduced degree of esophageal stricture.

The liver surface as a favorable site for islet cell sheet transplantation in type 1 diabetes model mice

INTRODUCTION

Islet transplantation is one of the most promising therapeutic approaches for patients with severe type 1 diabetes mellitus (T1DM). Transplantation of engineered islet cell sheets holds great potential for treating T1DM as it enables the creation of stable neo-islet tissues. However, a large mass of islet cell sheets is required for the subcutaneous transplantation to reverse hyperglycemia in diabetic mice. Here, we investigated whether the liver surface could serve as an alternative site for islet cell sheet transplantation.

METHODS

Dispersed rat islet cells (0.8 × 106 cells) were cultured on laminin-332-coated thermoresponsive culture dishes. After 2 days of cultivation, we harvested the islet cell sheets by lowering the culture temperature using a support membrane with a gelatin gel. We transplanted two recovered islet cell sheets into the subcutaneous space or onto the liver surface of severe combined immunodeficiency (SCID) mice with streptozocin-induced diabetes.

RESULTS

In the liver surface group, the non-fasting blood glucose level decreased rapidly within several days after transplantation. In marked contrast, the hyperglycemia state was maintained in the subcutaneous space transplantation group. The levels of rat C-peptide and insulin in the liver surface group were significantly higher than those in the subcutaneous space group. An immunohistological analysis confirmed that most of the islet cells engrafted on the liver surface were insulin-positive. The CD31-positive endothelial cells formed vascular networks within the neo-islets and in the surrounding tissues. In contrast, viable islet cells were not found in the subcutaneous space group.

CONCLUSIONS

Compared with the subcutaneous space, a relatively small mass of islet cell sheets was enough to achieve normoglycemia in diabetic mice when the liver surface was selected as the transplantation site. Our results demonstrate that the optimization of the transplantation site for islet cell sheets leads to significant improvements in the therapeutic efficiency for T1DM.

Electroactive polymers for tissue regeneration: Developments and perspectives

Human body motion can generate a biological electric field and a current, creating a voltage gradient of -10 to -90 mV across cell membranes. In turn, this gradient triggers cells to transmit signals that alter cell proliferation and differentiation. Several cell types, counting osteoblasts, neurons and cardiomyocytes, are relatively sensitive to electrical signal stimulation. Employment of electrical signals in modulating cell proliferation and differentiation inspires us to use the electroactive polymers to achieve electrical stimulation for repairing impaired tissues. Electroactive polymers have found numerous applications in biomedicine due to their capability in effectively delivering electrical signals to the seeded cells, such as biosensing, tissue regeneration, drug delivery, and biomedical implants. Here we will summarize the electrical characteristics of electroactive polymers, which enables them to electrically influence cellular function and behavior, including conducting polymers, piezoelectric polymers, and polyelectrolyte gels. We will also discuss the biological response to these electroactive polymers under electrical stimulation. In particular, we focus this review on their applications in regenerating different tissues, including bone, nerve, heart muscle, cartilage and skin. Additionally, we discuss the challenges in tissue regeneration applications of electroactive polymers. We conclude that electroactive polymers have a great potential as regenerative biomaterials, due to their ability to stimulate desirable outcomes in various electrically responsive cells.

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.

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.

Utility of double endoscopic intraluminal operation for esophageal cancer

OBJECTIVES

Endoscopic submucosal dissection (ESD) is a more difficult technique for esophageal cancer than for gastric cancer because the working space for esophageal ESD is small. Further, the difficulty level gradually increases depending on the size of the carcinoma. To overcome these difficulties, double endoscopic intraluminal operation (DEILO), which enables the resection of mucosal lesions using two fine endoscopes and monopolar shears, was reported previously. Here, we report the utility of DEILO for esophageal cancer.

METHODS

A total of 26 esophageal cancer patients (19 men and seven women) with 26 lesions treated using DEILO between 2011 and 2014 at Gunma University Hospital were included. We evaluated the utility and safety of DEILO for early esophageal cancer.

RESULTS

For all patients (100%), the DEILO procedure was performed successfully, and en bloc resection was achieved. The median operation time, postoperative hospital stay, and the longitudinal dimension of resected specimens were 123 min (range 45-236 min), 5 days, and 32 mm, respectively. Perioperative perforation, pneumothorax, and mediastinal emphysema were not recognized. Only one patient was diagnosed with a postoperative hemorrhage, but the bleeding was successfully treated by bleeding vessel coagulation.

CONCLUSION

DEILO has good utility as a technique of ESD for early esophageal cancers. Additional improvement and advancement of the procedure will increase the indication of DEILO.

The application of cell sheet engineering in the vascularization of tissue regeneration

Scaffold-free cell sheet engineering (CSE) is a new technology to regenerate injured or damaged tissues, which has shown promising potential in tissue regeneration. CSE uses a thermosensitive surface to form a dense cell sheet that can be detached when temperature decreases. The detached cell sheet can be stacked on top of one another according to the thickness of cell sheet for the specific tissue regeneration application. One of the key challenges of tissue engineering is vascularization. CSE technique provides excellent microenvironment for vascularization since the technique can maintain the intact cell matrix that is crucial for angiogenesis. In this review paper, we will highlight the principle technique of CSE and its application in tissue regeneration.

Topical hemostatic powder promotes reepithelialization and reduces scar formation after extensive esophageal mucosal resection

The development of techniques for endoscopic resection has provided new strategies for radical conservative treatment of superficial esophageal neoplasms, even those that are circumferential, such as Barrett's neoplasia. However, it is necessary to prevent the formation of scar tissue that can be responsible for esophageal strictures following circumferential resection. Preliminary data have suggested the possible efficacy of a hemostatic powder in the promotion of wound healing. The study aims to assess the effectiveness of Hemospray (Cook Medical) in a swine model of post-endoscopic esophageal stricture. Our prospective controlled study included 21 pigs. A 6-cm circumferential submucosal dissection of the esophagus (CESD) was performed in each pig. Group 1 (n = 11) only underwent CESD and Group 2 (n = 10) had repeated Hemospray applications after CESD. Clinical, endoscopic, and radiological monitoring were performed, blood levels of four inflammatory or pro-fibrotic cytokines were assessed, and histological analysis was performed. Median esophageal diameter was greater in the group treated with Hemospray (2 mm [1-3] vs. 3 mm [2-4], P = 0.01), and the rate of symptomatic esophageal stricture was 100% and 60% in Groups 1 and 2, respectively (P = 0.09). The thicknesses of esophageal fibrosis and inflammatory cell infiltrate were significantly lower in Group 2 than in Group 1 (P = 0.002 and 0.0003, respectively). The length of the neoepithelium was greater in Group 2 than in Group 1 (P = 0.0004). Transforming growth factor-β levels were significantly lower in Group 2 than in Group 1 (P = 0.01). The application of Hemospray after esophageal CESD reduces scar tissue formation and promotes reepithelialization, and therefore is a promising therapeutic approach in the prevention of post-endoscopic esophageal stricture.

Cell Sheet-Based Tissue Engineering for Organizing Anisotropic Tissue Constructs Produced Using Microfabricated Thermoresponsive Substrates

In some native tissues, appropriate microstructures, including orientation of the cell/extracellular matrix, provide specific mechanical and biological functions. For example, skeletal muscle is made of oriented myofibers that is responsible for the mechanical function. Native artery and myocardial tissues are organized three-dimensionally by stacking sheet-like tissues of aligned cells. Therefore, to construct any kind of complex tissue, the microstructures of cells such as myotubes, smooth muscle cells, and cardiomyocytes also need to be organized three-dimensionally just as in the native tissues of the body. Cell sheet-based tissue engineering allows the production of scaffold-free engineered tissues through a layer-by-layer construction technique. Recently, using microfabricated thermoresponsive substrates, aligned cells are being harvested as single continuous cell sheets. The cell sheets act as anisotropic tissue units to build three-dimensional tissue constructs with the appropriate anisotropy. This cell sheet-based technology is straightforward and has the potential to engineer a wide variety of complex tissues. In addition, due to the scaffold-free cell-dense environment, the physical and biological cell-cell interactions of these cell sheet constructs exhibit unique cell behaviors. These advantages will provide important clues to enable the production of well-organized tissues that closely mimic the structure and function of native tissues, required for the future of tissue engineering.

Systematic review: the prevention of oesophageal stricture after endoscopic resection

BACKGROUND

Extensive endoscopic resections for the treatment of early oesophageal neoplasia can result in fibro-inflammatory strictures that require repeated interventions, which significantly alter the patients' quality of life.

AIMS

To review current evidence about the prevention of oesophageal strictures following endoscopic resections.

METHODS

Systematic search of PubMed and Embase from inception to March 2015 using appropriate keywords. All original publications in English were included, and articles on the treatment of oesophageal stricture were excluded.

RESULTS

Of the 461 hits, 62 studies were included in the analysis. Among the wound-protective strategies, polyglycolic acid sheets showed the most convincing evidence with a 37.5% stricture rate and excellent safety. Regenerative medicine, using cell sheets of autologous keratinocytes, resulted in a 25% stricture rate, although with cost and availability concerns. Among anti-proliferative treatment modalities, steroid treatment, either endoscopically injected triamcinolone in the resection wound or orally administered prednisolone, proved effective with an overall stricture rate of 13.5%, with safety concerns regarding late oesophageal perforations and infectious morbidity. Among mechanical treatment options, poorly effective and high-risk preventive balloon dilation tend to be replaced by prophylactic covered stent, with 18-28% stricture rates.

CONCLUSIONS

Although oral or locally injected steroids are promising options, no currently available technique is sufficiently efficient and devoid of significant safety concerns to recommend its routine use for the prevention of strictures after extensive endoscopic resection. Improving our knowledge in the mechanisms of oesophageal wound healing will guide the development of novel methods for stricture prevention.

Useful strategies to prevent severe stricture after endoscopic submucosal dissection for superficial esophageal neoplasm

The minimal invasiveness of endoscopic submucosal dissection (ESD) prompted us to apply this technique to large-size early esophageal squamous cell carcinoma and Barrett’s adenocarcinoma, despite the limitations in the study population and surveillance duration. A post-ESD ulceration of greater than three-fourths of esophageal circumference was advocated as an important risk factor for refractory strictures that require several sessions of dilation therapy. Most of the preoperative conditions are asymptomatic, but dilatation treatment for dysphagia associated with the stricture has potential risks of severe complications and a worsening of quality of life. Possible mechanisms of dysphasia were demonstrated based on dysmotility and pathological abnormalities at the site: (1) delayed mucosal healing; (2) severe inflammation and disorganized fibrosis with abundant extracellular matrices in the submucosa; and (3) atrophy in the muscularis proper. However, reports on the administration of anti-scarring agents, preventive dilation therapies, and regenerative medicine demonstrated limited success in stricture prevention, and there were discrepancies in the study designs and protocols of these reports. The development and consequent long-term assessments of new prophylactic technologies on the promotion of wound healing and control of the inflammatory/tumor microenvironment will require collaboration among various research fields because of the limited accuracy of preoperative staging and high-risk of local recurrence.