Dynamic sealing of lung air leaks by the transplantation of tissue engineered cell sheets

Dual-color FISH analyses of xenogeneic human fibroblast sheets transplanted to repair lung pleural defects in an immunocompromised rat model

BACKGROUND

Pulmonary air leaks (PALs) due to visceral pleura injury during surgery is frequently observed after pulmonary resections and the complication is difficult to avoid in thoracic surgery. The development of postoperative PALs is the most common cause of prolonged hospitalization. Previously, we reported that PALs sealants using autologous dermal fibroblast sheets (DFSs) harvested from temperature-responsive culture dishes successfully closed intraoperative PALs during lung resection.

OBJECTIVE

In this study, we investigated the fate of human DFSs xenogenetically transplanted onto lung surfaces to seal PALs of immunocompromised rat. Dual-color FISH analyses of human fibroblast was employed to detect transplantation human cells on the lung surface.

RESULTS

One month after transplantation, FISH analyses revealed that transplanted human fibroblasts still composed a sheet-structure, and histology also showed that beneath the sheet's angiogenesis migrating into the sheets was observed from the recipient tissues. FISH analyses revealed that even at 3 months after transplantation, the transplanted human fibroblasts still remained in the sheet. Dual-color FISH analyses of the transplanted human fibroblasts were sparsely present as a result of the cells reaching the end of their lifespan, the cells producing extracellular matrix, and remained inside the cell sheet and did not invade the lungs of the host.

CONCLUSIONS

DFS-transplanted human fibroblasts showed that they are retained within cell sheets and do not invade the lungs of the host.

Reproducible Preparation of Primary Rat Hepatocyte Sheets Using a Thermoresponsive Culture Dish

Hepatocyte transplantation has been utilized as a therapy for congenital metabolic liver diseases such as hemophilia and for liver function support in acute liver failure. Hepatocyte sheet technology using a thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-grafted dish is expected to provide an efficient cell transplantation method because the resulting hepatocyte sheet possesses extracellular matrix (ECM) on the basal surface, which enhances attachment to the target sites. However, the cultured hepatocytes consume large amounts of oxygen, leading to the loss of a few hepatocytes within the confluent culture sheet owing to a lack of oxygen. To circumvent this problem, this work demonstrates the shortening of diffusion distance, that is, the medium depth, to accelerate oxygen supply from the gas phase/medium interface to the cultured hepatocytes, allowing them to form a monolayer hepatocyte sheet. Incubation of hepatocytes with medium at a depth of 1.3 mm facilitates confluent culture of hepatocytes for 72 h, whereas viable hepatocytes decreased at 2.6 mm depth. Hepatocyte sheets are formed on a 0.5 μg/cm2 fibronectin-physisorbed PIPAAm-grafted dish during 72 h incubation at 37°C. Detachment of the cultured hepatocyte sheet from the PIPAAm-grafted dish where the surface becomes hydrophilic at 20°C is accomplished by scraping the periphery of the sheet using a cell scraper. Furthermore, the apical side of the hepatocyte sheet can be physically grabbed using a gelatin-coated membrane, and the sheet with ECM on the basal surface can be readily transferred to the target site after melting the coated gelatin at 37°C. Both methods are beneficial for creating tissue models by layering with another type of cell sheets, and for quick transplantation, such as into the subcutaneous space and orthotopic transplantation on the surface of the liver.

Evaluating and developing sealants for the prevention of pulmonary air leakage: A systematic review of animal models

Sealants may provide a solution for pulmonary air leakage (PAL), but their clinical application is debatable. For sealant comparison, standardized animal models are lacking. This systematic review aims to assess methodology and quality of animal models for PAL and sealant evaluation. All animal models investigating lung sealing devices (e.g., staplers, glues, energy devices) to prevent or treat PAL were retrieved systematically from Embase, Pubmed and Web of science. Methodological study characteristics, risk of bias, reporting quality and publication bias were assessed. A total of 71 studies were included (N  =  75 experiments, N  =  1659 animals). Six different species and 18 strains were described; 92% of experiments used healthy animals, disease models were used in only six studies. Lesions to produce PAL were heterogenous, and only 11 studies used a previously reported technique, encompassing N  =  5 unique lesions. Clinically relevant outcomes were used in the minority of studies (imaging 16%, air leak 10.7%, air leak duration 4%). Reporting quality was poor, but revealed an upward trend per decade. Overall, high risk of bias was present, and only 18.7% used a negative control group. All but one study without control groups claimed positive outcomes (95.8%), in contrast to 84.3% using positive or negative control groups, which also concluded equivocal, adverse or inconclusive outcomes. In conclusion, animal studies evaluating sealants for prevention of PAL are heterogenous and of poor reporting quality. Using negative control groups, disease models and quantifiable outcomes seem important to increase validity and relevance. Further research is needed to reach consensus for model development and standardization.

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 novel alveolar epithelial cell sheet fabricated under feeder-free conditions for potential use in pulmonary regenerative therapy

Introduction

Methods

Results

Conclusions

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Alveolar epithelial cells were cultured and expanded under feeder-free conditions.

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Alveolar epithelial cell sheets were generated using temperature-responsive dishes.

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Alveolar epithelial cell sheets engrafted after transplantation onto rat lung.

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The sheets retained alveolar epithelial cell characteristics after transplantation.

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These cell sheets potentially could be used for pulmonary regenerative therapy.

Thermoresponsive interfaces obtained using poly(N-isopropylacrylamide)-based copolymer for bioseparation and tissue engineering applications

Poly(N-isopropylacrylamide) (PNIPAAm) is the most well-known and widely used stimuli-responsive polymer in the biomedical field owing to its ability to undergo temperature-dependent hydration and dehydration with temperature variations, causing hydrophilic and hydrophobic alterations. This temperature-dependent property of PNIPAAm provides functionality to interfaces containing PNIPAAm. Notably, the hydrophilic and hydrophobic alterations caused by the change in the temperature-responsive property of PNIPAAm-modified interfaces induce temperature-modulated interactions with biomolecules, proteins, and cells. This intrinsic property of PNIPAAm can be effectively used in various biomedical applications, particularly in bioseparation and tissue engineering applications, owing to the functionality of PNIPAAm-modified interfaces based on the temperature modulation of the interaction between PNIPAAm-modified interfaces and biomolecules and cells. This review focuses on PNIPAAm-modified interfaces in terms of preparation method, properties, and their applications. Advances in PNIPAAm-modified interfaces for existing and developing applications are also summarized.

Bio-artificial pleura using autologous dermal fibroblast sheets to mitigate air leaks during thoracoscopic lung resection

Lung air leaks (LALs) due to visceral pleura injury during surgery are a difficult-to-avoid complication in thoracic surgery (TS). Reliable LAL closure is an important patient management issue after TS. We demonstrated both safeties of transplantation of a cultured human autologous dermal fibroblast sheet (DFS) to LALs. From May 2016 to March 2018, five patients who underwent thoracoscopic lung resection met all the inclusion criteria. Skin biopsies were acquired from each patient to source autologous dermal cells for DFS fabrication. During the primary culture, fibroblasts migrated from the dermal tissue pieces and proliferated to form cell monolayers. These fibroblasts were subcultured to confluence. Transplantable DFSs were fabricated from these subcultured fibroblasts that were trypsinized and seeded onto temperature-responsive culture dishes. After 10 days of fabrication culture, intact patient-specific DFS were harvested. DFSs were analyzed for fibroblast cell content and tissue contaminants prior to application. For closing intraoperative LAL, mean number of transplanted autologous DFS per patient was 6 ± 2 sheets. Mean chest drainage duration was 5.0 ± 4.8 days. The two patients with major LAL had a drainage duration of more than 7 days. All patients currently have no LAL recurrence after discharge. DFSs effectively maintain LAL closure via remodeling of the deposited extracellular matrix. The use of autologous DFSs to permanently close air leaks using a patient-derived source is expected to reduce surgical complications during high-risk lung resections.

Scaffold-Free Bio-3D Printing Using Spheroids as "Bio-Inks" for Tissue (Re-)Construction and Drug Response Tests

In recent years, scaffold-free bio-3D printing using cell aggregates (spheroids) as "bio-inks" has attracted increasing attention as a method for 3D cell construction. Bio-3D printing uses a technique called the Kenzan method, wherein spheroids are placed one-by-one in a microneedle array (the "Kenzan") using a bio-3D printer. The bio-3D printer is a machine that was developed to perform bio-3D printing automatically. Recently, it has been reported that cell constructs can be produced by a bio-3D printer using spheroids composed of many types of cells and that this can contribute to tissue (re-)construction. This progress report summarizes the production and effectiveness of various cell constructs prepared using bio-3D printers. It also considers the future issues and prospects of various cell constructs obtained by using this method for further development of scaffold-free 3D cell constructions.

Scaffold-free: A developing technique in field of tissue engineering

Scaffold-free tissue engineering can be considered as a rapidly developing technique in the field of tissue engineering. In the areas of regenerative medicine and wound healing, there is a demand of techniques where no scaffolds are used for the development of desired tissue. These techniques will overcome the problems of rejection and tissue failure which are common with scaffolds. Main breakthrough of scaffold free tissue engineering was after invention of 3-D printers which made it possible to print complex tissues which were not possible by conventional methods. Mathematical modeling is a prediction technique is used in tissue engineering for simulation of the model to be constructed. Coming to scaffold-free technique, mathematical modeling is necessary for the processing of the model that has to be bio-printed so as to avoid and changes in the final construct. Tissue construct is developed by use of non-destructive imaging techniques i.e. computed tomography (CT) and magnetic resonance imaging (MRI).In this review, we discussed about various mathematical models and the models which are widely used in bioprinting techniques such as Cellular Potts Model (CPM) and Cellular Particle Dynamic (CPD) model. Later, developed of 3-D tissue construct using micro CT scan images was explained. Finally, we discussed about scaffold free techniques such as 3-D bioprinting and cell sheet technology. In this manuscript, we proposed a cell sheet based bioprinting technique where mesenchymal stem cells (MSCs) on the surface of thermoresponsive polymer were subjected to mechanosensing either by introducing acoustic energies or stress created by polymeric strain energy function. Mechanosensing stimulus will trigger the intracellular signal transduction pathway leading to differentiation of the MSCs into desired cells.

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.

Characteristic differences of cell sheets composed of mesenchymal stem cells with different tissue origins

INTRODUCTION

Stem cell therapy with mesenchymal stem cells (MSCs) has been widely used in many clinical trials, and therapy with MSC sheets shows promise for patients. However, there are few reports characterizing MSC sheets. In the present study, the properties of MSC sheets derived from bone marrow, adipose tissue, and umbilical cord were evaluated.

METHODS

Cell sheets were fabricated with MSCs from different tissue origins in temperature-responsive cell culture dishes with and without pre-coating of fetal bovine serum (FBS). MSC adhesion behavior in the culture dish was observed. Secretion of cytokines related to cell proliferation and immune regulation from MSC sheets was investigated by ELISA. The adhesion properties of the MSC sheets were investigated by time-lapse microscopy.

RESULTS

Different cell adhesion and proliferation rates in temperature-responsive cell culture dishes were observed among the three types of MSCs. FBS pre-coating of the dishes enhanced cell attachment and proliferation in all cell types. Harvested cell sheets showed high attachment capacity to tissue culture polystyrene dish surfaces.

CONCLUSIONS

MSC sheets can be fabricated from MSCs from different tissue origins using temperature-responsive cell culture dishes. The fabricated MSC sheets could be useful in cell transplantation therapies by choosing appropriate types of MSCs that secrete therapeutic cytokines for the targeted diseases.

Off-the-Shelf Cell Sheets as a Pleural Substitute for Closing Visceral Pleural Injuries

During pulmonary resections, removal of visceral pleura is frequently required, resulting in lung air leakage (LAL) and bleeding. Especially persistent LAL after pulmonary surgery has negative consequences. Current surgical procedures are ineffective in closing these visceral pleural injuries. Previously, the authors' laboratory has developed a novel and effective LAL sealant using tissue-engineered cell sheets harvested from temperature-responsive culture dishes. The clinical application of fresh fibroblast sheets (FSs) is limited by several problems related to the cell culture period, mass production, preservation, and transportation. Therefore, cryopreservation of FSs and feasibility of off-the-shelf FSs for repairing visceral pleural defects were investigated. Over 3 to 6 months, harvested skin-derived FSs in Dulbecco's modified Eagle's medium supplemented with 10% dimethyl sulfoxide were stored in an atmosphere of liquid nitrogen. The amounts of cytokines (basic fibroblast growth factor [bFGF] and vascular endothelial growth factor) released from frozen-thawed FSs were determined. bFGF levels were significantly elevated in frozen-thawed FSs compared with fresh FSs. After a visceral pleural injury model was created, a frozen-thawed skin-derived FS was transplanted directly to the defect. One month after transplantation, the frozen-thawed FS remained on the pleural surface, resulting in permanent closure, suggesting that cells in the off-the-shelf FS had the ability to proliferate and release various cytokines. Frozen-thawed FSs were useful for closing LALs during pulmonary surgery as an off-the-shelf technique and would be used as a pleural substitute.

Poly(N-isopropylacrylamide)-based thermoresponsive surfaces provide new types of biomedical applications

Thermoresponsive surfaces, prepared by grafting of poly(N-isopropylacrylamide) (PIPAAm) or its copolymers, have been investigated for biomedical applications. Thermoresponsive cell culture dishes that show controlled cell adhesion and detachment following external temperature changes, represent a promising application of thermoresponsive surfaces. These dishes can be used to fabricate cell sheets, which are currently used as effective therapies for patients. Thermoresponsive microcarriers for large-scale cell cultivation have also been developed by taking advantage of the thermally modulated cell adhesion and detachment properties of thermoresponsive surfaces. Furthermore, thermoresponsive bioseparation systems using thermoresponsive surfaces for separating and purifying pharmaceutical proteins and therapeutic cells have been developed, with the separation systems able to maintain their activity and biological potency throughout the procedure. These applications of thermoresponsive surfaces have been improved with progress in preparation techniques of thermoresponsive surfaces, such as polymerization methods, and surface modification techniques. In the present review, the various types of PIPAAm-based thermoresponsive surfaces are summarized by describing their preparation methods, properties, and successful biomedical applications.

Bio-artificial pleura using an autologous dermal fibroblast sheet

Air leaks (ALs) are observed after pulmonary resections, and without proper treatment, can produce severe complications. AL prevention is a critical objective for managing patients after pulmonary resection. This study applied autologous dermal fibroblast sheets (DFS) to close ALs. For sealing ALs in a 44-year-old male human patient with multiple bullae, a 5 × 15-mm section of skin was surgically excised. From this skin specimen, primary dermal fibroblasts were isolated and cultured for 4 weeks to produce DFSs that were harvested after a 10-day culture. ALs were completely sealed using surgical placement of these autologous DFSs. DFS were found to be a durable long-term AL sealant, exhibiting requisite flexibility, elasticity, durability, biocompatibility, and usability, resulting reliable AL closure. DFS should prove to be an extremely useful tissue-engineered pleura substitute.

Hepatocyte Transplantation: Cell Sheet Technology for Liver Cell Transplantation

Purpose of Review

We will review the recent developments of cell sheet technology as a feasible tissue engineering approach. Specifically, we will focus on the technological advancement for engineering functional liver tissue using cell sheet technology, and the associated therapeutic effect of cell sheets for liver diseases, highlighting hemophilia.

Recent Findings

Cell-based therapies using hepatocytes have recently been explored as a new therapeutic modality for patients with many forms of liver disease. We have developed a cell sheet technology, which allows cells to be harvested in a monolithic layer format. We have succeeded in fabricating functional liver tissues in mice by stacking the cell sheets composed of primary hepatocytes. As a curative measure for hemophilia, we have also succeeded in treating hemophilia mice by transplanting of cells sheets composed of genetically modified autologous cells.

Summary

Tissue engineering using cell sheet technology provides the opportunity to create new therapeutic options for patients with various types of liver diseases.

Application of the cell sheet technique in tissue engineering

The development and application of the tissue engineering technique has shown a significant potential in regenerative medicine. However, the limitations of conventional tissue engineering methods (cell suspensions, scaffolds and/or growth factors) restrict its application in certain fields. The novel cell sheet technique can overcome such disadvantages. Cultured cells can be harvested as intact sheets without the use of proteolytic enzymes, such as trypsin or dispase, which can result in cell damage and loss of differentiated phenotypes. The cell sheet is a complete layer, which contains extracellular matrix, ion channel, growth factor receptors, nexin and other important cell surface proteins. Mesenchymal stem cells (MSCs), which have the potential for multiple differentiation, are promising candidate seed cells for tissue engineering. The MSC sheet technique may have potential in the fields of regenerative medicine and tissue engineering in general. Additionally, induced pluripotent stem cell and embryonic stem cell-derived cell sheets have been proposed for tissue regeneration. Currently, the application of cell sheet for tissue reconstruction includes: Direct recipient sites implantation, superposition of cell sheets to construct three-dimensional structure for implantation, or cell sheet combined with scaffolds. The present review discusses the progress in cell sheet techniques, particularly stem cell sheet techniques, in tissue engineering.

An immunocompetent, orthotopic mouse model of epithelial ovarian cancer utilizing tissue engineered tumor cell sheets

Despite the development of a myriad of anticancer drugs that appeared promising in preclinical ovarian cancer animal models, they failed to predict efficacy in clinical testing. To improve the accuracy of preclinical testing of efficacy and toxicity, including pharmacokinetic and pharmacodynamic evaluations, a novel animal model was developed and characterized. In this study, murine ID8 (epithelial ovarian cancer [EOC]) cells as injected cell suspensions (ICS) and as intact cultured monolayer cell sheets (CS) were injected or surgically grafted, respectively, into the left ovarian bursa of 6-8 week-old, female C57BL/6 black mice and evaluated at 8 and 12 weeks after engraftment. Tumor volumes at 8 weeks were as follows: 30.712 ± 18.800 mm(3) versus 55.837 ± 10.711 mm(3) for ICS and CS, respectively, p = 0.0990 (n = 5). At 12 weeks, tumor volumes were 128.129 ± 44.018 mm(3) versus 283.953 ± 71.676 mm(3) for ICS and CS, respectively, p = 0.0112 (n = 5). The ovarian weights at 8 and 12 weeks were 0.02138 ± 0.01038 g versus 0.04954 ± 0.00667 g for ICS and CS, respectively (8 weeks), p = 0.00602 (n = 5); and 0.10594 ± 0.03043 g versus 0.39264 ± 0.09271 g for ICS and CS, respectively (12 weeks), p = 0.0008 (n = 5). These results confirm a significant accelerated tumorigenesis in CS-derived tumors compared with ICS-derived tumors when measured by tumor volume/time and ovarian weight/time. Furthermore, the CS-derived tumors closely replicated the metastatic spread found in human EOC and histopathological identity with the primary tumor of origin.

Respiratory Tissue Engineering: Current Status and Opportunities for the Future

Currently, lung disease and major airway trauma constitute a major global healthcare burden with limited treatment options. Airway diseases such as chronic obstructive pulmonary disease and cystic fibrosis have been identified as the fifth highest cause of mortality worldwide and are estimated to rise to fourth place by 2030. Alternate approaches and therapeutic modalities are urgently needed to improve clinical outcomes for chronic lung disease. This can be achieved through tissue engineering of the respiratory tract. Interest is growing in the use of airway tissue-engineered constructs as both a research tool, to further our understanding of airway pathology, validate new drugs, and pave the way for novel drug therapies, and also as regenerative medical devices or as an alternative to transplant tissue. This review provides a concise summary of the field of respiratory tissue engineering to date. An initial overview of airway anatomy and physiology is given, followed by a description of the stem cell populations and signaling processes involved in parenchymal healing and tissue repair. We then focus on the different biomaterials and tissue-engineered systems employed in upper and lower respiratory tract engineering and give a final perspective of the opportunities and challenges facing the field of respiratory tissue engineering.

Cell sheet-based tissue engineering for fabricating 3-dimensional heart tissues

In addition to stem cell biology, tissue engineering is an essential research field for regenerative medicine. In contrast to cell injection, bioengineered tissue transplantation minimizes cell loss and has the potential to repair tissue defects. A popular approach is scaffold-based tissue engineering, which utilizes a biodegradable polymer scaffold for seeding cells; however, new techniques of cell sheet-based tissue engineering have been developed. Cell sheets are harvested from temperature-responsive culture dishes by simply lowering the temperature. Monolayer or stacked cell sheets are transplantable directly onto damaged tissues and cell sheet transplantation has already been clinically applied. Cardiac cell sheet stacking produces pulsatile heart tissue; however, lack of vasculature limits the viable tissue thickness to 3 layers. Multistep transplantation of triple-layer cardiac cell sheets cocultured with endothelial cells has been used to form thick vascularized cardiac tissue in vivo. Furthermore, in vitro functional blood vessel formation within 3-dimensional (3D) tissues has been realized by successfully imitating in vivo conditions. Triple-layer cardiac cell sheets containing endothelial cells were layered on vascular beds and the constructs were media-perfused using novel bioreactor systems. Interestingly, cocultured endothelial cells migrate into the vascular beds and form perfusable blood vessels. An in vitro multistep procedure has also enabled the fabrication of thick, vascularized heart tissues. Cell sheet-based tissue engineering has revealed great potential to fabricate 3D cardiac tissues and should contribute to future treatment of severe heart diseases and human tissue model production.

Micro-patterned cell-sheets fabricated with stamping-force-controlled micro-contact printing

Cell-sheet-engineering based regenerative medicine is successfully applied to clinical studies, though cell sheets contain uniformly distributed cells. For the further application to complex tissues/organs, cell sheets with a multi-cellular pattern were highly demanded. Micro-contact printing is a quite useful technique for patterning proteins contained in extracellular matrix (ECM). Because ECM is a kind of cellular adherent molecules, ECM-patterned cell culture surface is capable of aligning cells on the pattern of ECM. However, a manual printing is difficult, because a stamp made from polydimethylsiloxane (PDMS) is easily deformed, and a printed pattern is also crushed. This study focused on the deformability of PDMS stamp and discussed an appropriate stamping force in micro-contact printing. Considering in availability in a medical or biological laboratory, a method for assessing the stamp deformability was developed by using stiffness measurement with a general microscope. An automated stamping system composed of a load cell and an automated actuator was prepared and allowed to improve the quality of stamped pattern by controlling an appropriate stamping force of 0.1 N. Using the system and the control of appropriate stamping force, the pattern of 8-mm-diameter 80-μm-stripe fibronectin was fabricated on the surface of temperature-responsive cell culture dish. After cell-seeding and cell culture, a co-culture system with the micro-pattern of both fibroblasts and endothelial cells was completed. Furthermore, by reducing temperature to 20 °C, the co-cultured cell sheet with the micro-pattern was successfully harvested. As a result, the method would not only provide a high-quality ECM pattern but also a breakthrough technique to fabricate multi-cellular-patterned cell sheets for the next generation of regenerative medicine and tissue engineering.

Transplantation of cancerous cell sheets effectively generates tumour-bearing model mice

Tumour-bearing mice were created by transplanting cancerous cell sheets onto the subcutaneous tissue of the dorsal region, using luciferase gene-transfected mammary gland adenocarcinoma cells, 4T1-luc2, to investigate the tumourigenicity of the cell sheet relative to a conventional injection of cell suspension. Contiguous breast cancerous cell sheets were harvested from temperature-responsive culture dishes by reducing the temperature from 37 °C to 20 °C; the sheets were then transplanted onto the dorsal side of the mouse subcutaneous tissue, using a chitin-based supporting membrane. Cell suspensions obtained by trypsin digestion were subcutaneously injected into the dorsal region of mice. The tumour growth of the transplanted cancer cells was evaluated by the tumour volume and by the bioluminescence from luciferase-gene transfected cancer cells, using an in vivo imaging system. The cell sheet method improved the 4 T1-luc2 engraftment efficiency in living mouse tissues at the initial stage by 13-fold compared with that from injecting cell suspensions. On day 14 after the transplantation, the tumour formation at the transplanted area of cell sheet-transplanted mice also accelerated, and the mean tumour volume became 1116 mm³ , which was 10 times larger than that in cell suspension-transplanted mice. The cell sheets engrafted on the recipient tissues efficiently due to the preserved extracellular matrix on their basal sides, such that cancer cells were supplied with sufficient oxygen and nutrients from the host tissues to develop tumour tissues. Therefore, cancerous cell sheet-based transplantation is a promising method for efficiently creating cancer-bearing mice. Copyright © 2013 John Wiley & Sons, Ltd.

Intelligent Surfaces for Cell and Tissue Delivery

Cell transplantation remains a powerful approach for promising numerous biomedical applications to promote tissue regeneration. Therefore, smart delivery systems of therapeutic cells, as well as therapeutic oligonucleotides and proteins, are required. Although cells have been conventionally delivered by direct injection to target sites, a number of clinical studies showed a limitation due to poor cell retention and survival at the sites, resulting in insufficient effect on tissue/organ repair. Therefore, at present, numerous delivery strategies have been developed, and a variety of polymeric materials play important roles. For example, encapsulation in semi-permeable membrane made from biocompatible polymers (e.g. alginate-poly(l-lysine)-alginate) allows xenograft islets to be delivered in vivo without immune suppression. With progress in tissue engineering, scaffold-based cell/tissue delivery reached the mainstream for regenerating damaged tissues. Various kinds of scaffolds have been fabricated from natural and synthetic polymers, such as collagen or poly(l-lactic-co-glycolic acid), and allowed to provide appropriate nutritional conditions and spatial organization for cell growth. Whereas these scaffolds produce reliable architectures to design cell/tissue delivery, scaffold-free cell/tissue delivery also has opened up a new class technology in the field of regenerative medicine. Thermo-responsive poly(N-isopropylacrylamide)-grafted surfaces allow one to fabricate tissue-like cell monolayers, “cell sheets”, and deliver the cell-dense tissue with associated extra-cellular matrix (ECM) to damaged sites without scaffold implantation. The chapter focuses on unique cell/tissue delivery techniques using the intelligent surfaces. This technology has already been applied to human clinical studies for tissue regeneration, and microfabricated thermo-responsive surfaces are further developing for delivering more complex tissue.

Responsive systems for cell sheet detachment

Cell sheet engineering has been progressing rapidly during the past few years and has emerged as a novel approach for cell based therapy. Cell sheet harvest technology enables fabrication of viable, transplantable cell sheets for various tissue engineering applications. Currently, the majority of cell sheet studies use thermo-responsive systems for cell sheet detachment. However, other responsive systems began showing their potentials for cell sheet harvest. This review provides an overview of current techniques in creating cell sheets using different types of responsive systems including thermo-responsive, electro-responsive, photo-responsive, pH-responsive and magnetic systems. Their mechanism, approach, as well as applications for cell detachment have been introduced. Further development of these responsive systems will allow efficient cell sheet harvesting and patterning of cells to reconstruct complex tissue for broad clinical applications.

In Vitro Biofabrication of Tissues and Organs

In vitro fabrication of tissues and the regeneration of internal organs are no longer regarded as science fiction but as potential remedies for individuals suffering from chronic degenerative diseases. Tissue engineering has generated much interest from researchers in many fields, including cell and molecular biology, biomedical engineering, transplant medicine, and organic chemistry. Attempts to build tissues or organs in vitro have utilized both scaffold and scaffold-free approaches. Despite considerable progress, fabrication of three-dimensional tissue constructs in vitro remains a challenge. In this chapter, we introduce and discus current concepts of tissue engineering with particular focus on future clinical application.

Computational and bioengineered lungs as alternatives to whole animal, isolated organ, and cell-based lung models

Development of lung models for testing a drug substance or delivery system has been an intensive area of research. However, a model that mimics physiological and anatomical features of human lungs is yet to be established. Although in vitro lung models, developed and fine-tuned over the past few decades, were instrumental for the development of many commercially available drugs, they are suboptimal in reproducing the physiological microenvironment and complex anatomy of human lungs. Similarly, intersubject variability and high costs have been major limitations of using animals in the development and discovery of drugs used in the treatment of respiratory disorders. To address the complexity and limitations associated with in vivo and in vitro models, attempts have been made to develop in silico and tissue-engineered lung models that allow incorporation of various mechanical and biological factors that are otherwise difficult to reproduce in conventional cell or organ-based systems. The in silico models utilize the information obtained from in vitro and in vivo models and apply computational algorithms to incorporate multiple physiological parameters that can affect drug deposition, distribution, and disposition upon administration via the lungs. Bioengineered lungs, on the other hand, exhibit significant promise due to recent advances in stem or progenitor cell technologies. However, bioengineered approaches have met with limited success in terms of development of various components of the human respiratory system. In this review, we summarize the approaches used and advancements made toward the development of in silico and tissue-engineered lung models and discuss potential challenges associated with the development and efficacy of these models.

Autologous fibroblast transplantation at the vesico-ureteral junction as potential reconstructive cell replacement in an animal model

PURPOSE

To evaluate the cellular survival of donor fibroblasts after transplantation at the vesico-ureteral junction (VUJ) and to analyse their potential for reconstructive cell replacement in an animal model as autologous fibroblasts have been used as soft tissue augmentation material for scared and damaged tissue.

METHODS

Muscles biopsies were procured from the lower limb muscles of 4 pigs; cytoplasm of fibroblasts was labelled with nano-sized iron oxide particles. Six weeks after taking of the muscle biopsies, fibroblast transplantation was performed, 3 × 10(6) cells suspended in transplantation medium (in 1-ml syringes) were injected at the VUJ using the modified STING technique. Animals were killed 8 weeks later; seeded fibroblasts were identified using prussian blue staining protocol; histological evaluation and morphological analysis were performed by light microscopy (Mayer's haematoxylin-eosin staining); and bladders were scanned by MRI for visualization and localization of the iron-labelled donor cells.

RESULTS

Donor fibroblast cell colonization and cellular viability at the VUJ was demonstrated by MRI and histochemically indicating cellular uptake of iron particles at the VUJ. It was also evident that transplanted fibroblasts integrate into the extracellular matrix of the distal ureter augmenting ureteral host tissue.

CONCLUSIONS

Labelled implanted autologous fibroblasts were visualized by staining procedure as well as MRI scan demonstrating persistence at the VUJ, suggesting that in vitro expanded fibroblasts survived in vivo after transplantation.

Myocardial tissue engineering: toward a bioartificial pump

Regenerative therapies, including cell injection and bioengineered tissue transplantation, have the potential to treat severe heart failure. Direct implantation of isolated skeletal myoblasts and bone-marrow-derived cells has already been clinically performed and research on fabricating three-dimensional (3-D) cardiac grafts using tissue engineering technologies has also now been initiated. In contrast to conventional scaffold-based methods, we have proposed cell sheet-based tissue engineering, which involves stacking confluently cultured cell sheets to construct 3-D cell-dense tissues. Upon layering, individual cardiac cell sheets integrate to form a single, continuous, cell-dense tissue that resembles native cardiac tissue. The transplantation of layered cardiac cell sheets is able to repair damaged hearts. As the next step, we have attempted to promote neovascularization within bioengineered myocardial tissues to overcome the longstanding limitations of engineered tissue thickness. Finally, as a possible advanced therapy, we are now trying to fabricate functional myocardial tubes that may have a potential for circulatory support. Cell sheet-based tissue engineering technologies therefore show an enormous promise as a novel approach in the field of myocardial tissue engineering.

Regenerative therapies using cell sheet-based tissue engineering for cardiac disease

At present, cardiac diseases are a major cause of morbidity and mortality in the world. Recently, a cell-based regenerative medicine has appeared as one of the most potential and promising therapies for improving cardiac diseases. As a new generational cell-based regenerative therapy, tissue engineering is focused. Our laboratory has originally developed cell sheet-based scaffold-free tissue engineering. Three-dimensional myocardial tissue fabricated by stacking cardiomyocyte sheets, which are tightly interconnected to each other through gap junctions, beats simultaneously and macroscopically and shows the characteristic structures of native heart tissue. Cell sheet-based therapy cures the damaged heart function of animal models and is clinically applied. Cell sheet-based tissue engineering has a promising and enormous potential in myocardial tissue regenerative medicine and will cure many patients suffering from severe cardiac disease. This paper summarizes cell sheet-based tissue engineering and its satisfactory therapeutic effects on cardiac disease.

Anisotropic cell sheets for constructing three-dimensional tissue with well-organized cell orientation

Normal human dermal fibroblasts were aligned on micropatterned thermoresponsive surfaces simply by one-pot cell seeding. After they proliferated with maintaining their orientation, anisotropic cell sheets were harvested by reducing temperature to 20 °C. Surprisingly, the cell sheets showed different shrinking rates between vertical and parallel sides of the cell alignment (aspect ratio: approx. 3: 1), because actin fibers in the cell sheets were oriented with the same direction. The control of cell alignment provided not only a physical anisotropy but also biological impacts to the cell sheet. Vascular endothelial growth factor (VEGF) secreted by aligned fibroblasts was increased significantly, whereas transforming growth factor-β1 (TGF-β1) expression was the same level in anisotropic cell sheets as cell sheets having random cell orientations. Furthermore, although the amount of deposited type Ⅰ collagen was different non-significantly onto between cell sheets with and without controlled cell alignment, collagen deposited onto fibroblasts sheets with cell alignment also showed anisotropy, verified by a fluorescence imaging analysis. The physical and biological anisotropies of cell sheets were potentially useful to construct biomimetic tissues that were organized by aligned cells and/or extracellular matrix (ECM) including collagen in cell sheet-based regenerative medicine. Furthermore, due to the unique thermoresponsive property, the anisotropic cell sheets were successfully manipulated using a gelatin-coated plunger and were layered with maintaining their cell alignment. The combined use of the anisotropic cell sheet and cell sheet manipulation technique promises to create complex tissue that requires the three-dimensional control of their anisotropies, as one of the next-generation cell sheet technologies.

Characterization of the biological effect of fish fibrin glue in experiments on rats: immunological and coagulation studies

Fibrin glues (FG) of human or bovine origin are widely used for haemostasis and wound healing. In addition FGs are studied in many biomedical areas like cell therapy or tissue engineering. As any mammalian plasma products FG-s pose risk of transmission of bacteria, viruses, or prions and may compromise patient homeostasis. In this study, we examined coagulation parameters and immunological status of rats treated with salmon-derived FG. We evaluated the changes in thrombin time, prothrombin activity, and presence of antibodies on 46 Wistar rats. This study shows that salmon-derived FG, injected intraperitoneally, does not cause coagulation disturbances in the peripheral blood. After a first challenge with salmon-derived FG there were low but detectable amounts of antibodies revealed by ELISA and immunoblot. After a second administration there was substantial elevation of antibodies to FG components and other copurifying plasma proteins. Antibody reactivity to human Factor Va, revealed in three animals, was not associated with FG application. Taken together, blood immunological and coagulation parameters support the suitability of salmon-derived FG in the development of fibrin sealants for medical use.

Fabrication of a thermoresponsive cell culture dish: a key technology for cell sheet tissue engineering

This article reviews the properties and characterization of an intelligent thermoresponsive surface, which is a key technology for cell sheet-based tissue engineering. Intelligent thermoresponsive surfaces grafted with poly(N-isopropylacrylamide) exhibit hydrophilic/hydrophobic alteration in response to temperature change. Cultured cells are harvested on thermoresponsive cell culture dishes by decreasing the temperature without the use of digestive enzymes or chelating agents. Our group has developed cell sheet-based tissue engineering for therapeutic uses with single layer or multilayered cell sheets, which were recovered from the thermoresponsive cell culture dish. Using surface derivation techniques, we developed a new generation of thermoresponsive cell culture dishes to improve culture conditions. We also designed a new methodology for constructing well-defined organs using microfabrication techniques.