Biomedical subjects

Tatsuya Shimizu

Publications and source records attributed to Tatsuya Shimizu.

At least 19 recordsLinked to original sources

PubMed2006

Pulsatile myocardial tubes fabricated with cell sheet engineering.

BACKGROUND: Tissue engineering approaches involving the direct transplantation of cardiac patches have received significant attention as alternative methods for the treatment of damaged hearts. In contrast, we used cardiomyocyte sheets harvested from temperature-responsive culture dishes to create pulsatile myocardial tubes and examined their in vivo function and survival. METHODS AND RESULTS: Neonatal rat cardiomyocyte sheets were sequentially wrapped around a resected adult rat thoracic aorta and transplanted in place of the abdominal aorta of athymic rats (n=17). Four weeks after transplantation, the myocardial tubes demonstrated spontaneous and synchronous pulsations independent of the host heartbeat. Independent graft pressures with a magnitude of 5.9+/-1.7 mm Hg due to their independent pulsations were also observed (n=4). Additionally, histological examination and transmission electron microscopy indicated that the beating tubes were composed of cardiac tissues that resemble the native heart. Finally, when myocardial tubes used for aortic replacement were compared with grafts implanted in the abdominal cavity (n=7), we observed significantly increased tissue thickness, as well as expression of brain natriuretic peptide, myosin heavy chain-alpha, and myosin heavy chain-beta. CONCLUSIONS: Functional myocardial tubes that have the potential for circulatory support can be created with cell sheet engineering. These results also suggest that pulsation due to host blood flow within the lumen of the myocardial tubes has a profound effect on stimulating cardiomyocyte hypertrophy and growth. These results demonstrate a novel approach for the future development of engineered cardiac tissues with the ability for independent cardiac assistance.

Animals↗

PubMed2006

Cell delivery in regenerative medicine: the cell sheet engineering approach.

Recently, cell-based therapies have developed as a foundation for regenerative medicine. General approaches for cell delivery have thus far involved the use of direct injection of single cell suspensions into the target tissues. Additionally, tissue engineering with the general paradigm of seeding cells into biodegradable scaffolds has also evolved as a method for the reconstruction of various tissues and organs. With success in clinical trials, regenerative therapies using these approaches have therefore garnered significant interest and attention. As a novel alternative, we have developed cell sheet engineering using temperature-responsive culture dishes, which allows for the non-invasive harvest of cultured cells as intact sheets along with their deposited extracellular matrix. Using this approach, cell sheets can be directly transplanted to host tissues without the use of scaffolding or carrier materials, or used to create in vitro tissue constructs via the layering of individual cell sheets. In addition to simple transplantation, cell sheet engineered constructs have also been applied for alternative therapies such as endoscopic transplantation, combinatorial tissue reconstruction, and polysurgery to overcome limitations of regenerative therapies and cell delivery using conventional approaches.

Acrylic Resins↗

PubMed2006

Electrical coupling of cardiomyocyte sheets occurs rapidly via functional gap junction formation.

Previously, we have successfully created pulsatile myocardial tissue grafts using our novel technology, "cell sheet engineering", that layers cell sheets fabricated on temperature-responsive culture dishes to form three-dimensional (3-D) structures. Electrical coupling is established between layered neonatal rat cardiomyocyte sheets, resulting in the synchronized beating of 3-D myocardial tissues. However, the mechanism by which these layered cardiomyocyte sheets communicate electrically is not well-understood. In this study, we used a multiple-electrode extracellular recording system and demonstrated that bilayer cardiomyocyte sheets coupled electrically with slight delays 34+/-2 min (mean+/-SEM) after layering. These delays gradually decreased and the electrical actions of layered cell sheets were completely coupled 46+/-3 min (mean+/-SEM) after initial layering. Immunohistological analysis showed that connexin43, a gap junction (GJ)-related protein, existed not only at cell-to-cell interfaces but also on the free cell membrane in the cardiomyocyte sheet. Additionally, neither connexin40 nor connexin45, but only connexin43 was detected between bilayer cardiomyocyte sheets within 30 min after layering. Dye transfer assay demonstrated that the exchange of small molecules via GJs occurred within 30 min. The cell sheet manipulation technique using the temperature-responsive culture dishes has substantial advances and the exciting potential in the fields of cell and tissue physiology, as well as tissue engineering.

Action Potentials↗

PubMed2006

Monolayered mesenchymal stem cells repair scarred myocardium after myocardial infarction.

Mesenchymal stem cells are multipotent cells that can differentiate into cardiomyocytes and vascular endothelial cells. Here we show, using cell sheet technology, that monolayered mesenchymal stem cells have multipotent and self-propagating properties after transplantation into infarcted rat hearts. We cultured adipose tissue-derived mesenchymal stem cells characterized by flow cytometry using temperature-responsive culture dishes. Four weeks after coronary ligation, we transplanted the monolayered mesenchymal stem cells onto the scarred myocardium. After transplantation, the engrafted sheet gradually grew to form a thick stratum that included newly formed vessels, undifferentiated cells and few cardiomyocytes. The mesenchymal stem cell sheet also acted through paracrine pathways to trigger angiogenesis. Unlike a fibroblast cell sheet, the monolayered mesenchymal stem cells reversed wall thinning in the scar area and improved cardiac function in rats with myocardial infarction. Thus, transplantation of monolayered mesenchymal stem cells may be a new therapeutic strategy for cardiac tissue regeneration.

Animals↗

PubMed2006

Pulsatile cardiac tissue grafts using a novel three-dimensional cell sheet manipulation technique functionally integrates with the host heart, in vivo.

We devised a method of fabricating easily transplantable scaffoldless 3D heart tissue, made with a novel cell-sheet (CS) technology from cultured cardiomyocytes using a fibrin polymer coated dish. In the present study, we tested in vivo electrical communication which is essential for improving heart function between the host heart and the grafted CS. The epicardial surface of the ventricle of an anesthetized open-chest nude rat was ablated by applying a heated metal. Bilayered CS was obtained from neonatal rat primary culture. CS was transplanted onto the injured myocardial surface (sMI) (sMI+sheet group). The rats were allowed to recover for 1 to 4 weeks, to stabilize the grafts. Action potentials (APs) from the excised perfused heart were monitored by the fluorescence signal of di-4ANEPPS with a high speed charge-coupled device camera. The APs were observed under epicardial pacing of the host heart or the CS grafts. The pacing threshold of the current output was measured in the sMI+sheet group and in the nongrafted sMI group at the center of the sMI and in the normal zone (Nz). Bidirectional AP propagation between the sMI and Nz was observed in the sMI+sheet group (n=14), but was blocked at the marginal area of the sMI in the sMI group (n=9). The ratio of the pacing threshold (sMI/Nz) was significantly lower in the sMI+sheet than in the sMI group (3.0+/-0.7, 19.0+/-6.1 respectively P<0.05). There were neither spontaneous nor pacing-induced arrhythmias in these two groups. Bidirectional smooth AP propagation between the host heart and the grafted CS was observed. This finding suggested functional integration of this CS graft with the host heart without serious arrhythmia.

Action Potentials↗

PubMed2006

Longer preservation of cardiac performance by sheet-shaped myoblast implantation in dilated cardiomyopathic hamsters.

OBJECTIVES: Cell therapy is a promising strategy for ischemic cardiomyopathy. However, the direct injection method has limitations for generalized cell delivery, especially in dilated cardiomyopathy (DCM). We hypothesized that a sheet-shaped myoblast graft would be superior to direct injection for improving cardiac performance in DCM. METHODS: Male 27-week-old BIO TO-2 (DCM) hamsters that showed moderate cardiac remodeling were used as recipients. Myoblasts isolated from BIO F1B hamsters were cultured on dishes coated with poly(N-isopropylacrylamide), a temperature-responsive polymer, and spontaneously detached as a sheet-shaped graft at 20 degrees C without enzymatic treatment. Three different therapies were conducted: (1) sheet-shaped myoblast graft implantation (S group, n=29); (2) myoblast injection (M group, n=28); and (3) sham operation (C group, n=28). In the S group, two sheet-shaped myoblast grafts were implanted on the left ventricle (LV) wall, and in the M group, myoblasts were injected into the right ventricle (RV) and LV walls. RESULTS: After the sheet-shaped myoblast grafts were implanted, echocardiography demonstrated that the dilated LV dimension was significantly reduced, whereas the hearts in other groups showed a progression of LV dilation. The fractional shortening in the M and C groups decreased significantly while that in the S group was maintained at the preoperative level for 3 months after the operation. Histological examination demonstrated that in the S group, the LV wall thickness was increased, with viable myoblasts, and myocardial fibrosis was decreased compared with the other groups. Immunohistochemical staining demonstrated alpha-sarcoglycan and beta-sarcoglycan expression on the basement membrane of the cardiomyocytes in the S group but not in the other groups. The life expectancy was significantly prolonged in the S group. CONCLUSION: Sheet-shaped myoblast graft implantation improved cardiac performance and prolonged life expectancy, associated with a reduction in myocardial fibrosis and re-organization of the cytoskeletal proteins in DCM hamsters. Thus, sheet-shaped autologous myoblast graft implantation may induce restoration of the heart in DCM.

Animals↗

PubMed2006

Polysurgery of cell sheet grafts overcomes diffusion limits to produce thick, vascularized myocardial tissues.

Recently, the field of tissue engineering has progressed rapidly, but poor vascularization remains a major obstacle in bioengineering cell-dense tissues, limiting the viable size of constructs due to hypoxia, nutrient insufficiency, and waste accumulation. Therefore, new technologies for fabricating functional tissues with a well-organized vasculature are required. In the present study, neonatal rat cardiomyocytes were harvested as intact sheets from temperature-responsive culture dishes and stacked into cell-dense myocardial tissues. However, the thickness limit for layered cell sheets in subcutaneous tissue was approximately 80 microm (3 layers). To overcome this limitation, repeated transplantation of triple-layer grafts was performed at 1, 2, or 3 day intervals. The two overlaid grafts completely synchronized and the whole tissues survived without necrosis in the 1 or 2 day interval cases. Multistep transplantation also created approximately 1 mm thick myocardium with a well-organized microvascular network. Furthermore, functional multilayer grafts fabricated over a surgically connectable artery and vein revealed complete graft perfusion via the vessels and ectopic transplantation of the grafts was successfully performed using direct vessel anastomoses. These cultured cell sheet integration methods overcome long-standing barriers to producing thick, vascularized tissues, revealing a possible solution for the clinical repair of various damaged organs, including the impaired myocardium.

Animals↗

PubMed2006

An actuated pump on-chip powered by cultured cardiomyocytes.

Cellular functions are frequently exploited as processing components for integrated chemical systems such as biochemical reactors and bioassay systems. Here, we have created a new cell-based microsystem exploiting the intrinsic pulsatile mechanical functions of cardiomyocytes to build a cellular micropump on-chip using cardiomyocyte sheets as prototype bio-microactuators. We first demonstrate cell-based control of fluid motion in a model microchannel without check valves and evaluate the potential performance of the bio-actuation. For this purpose, a poly(dimethylsiloxane) (PDMS) microchip with a microchannel equipped with a diaphragm and a push-bar structure capable of harnessing collective cell fluid mechanical forces was coupled to a cultured pulsating cardiomyocyte sheet, activating cell-based fluid movement in the microchannel by actuating the diaphragm. Cell oscillation frequency and correlated fluid displacement in this system depended on temperature. When culture temperature was increased, collective cell contraction frequency remained cooperative and synchronous but increased, while displacement was slightly reduced. We then demonstrated directional fluid pumping within microchannels using cantilever-type micro-check valves made of polyimide. A directional flow rate of nL min(-1) was produced. This cell micropump system could be further developed as a self-actuated and efficient mechanochemical transducer requiring no external energy sources for various purposes in the future.

Animals↗

PubMed2006

Bioengineered cardiac cell sheet grafts have intrinsic angiogenic potential.

Previously, we have demonstrated the long-term survival of myocardial cell sheet constructs in vivo, with microvascular network formation throughout the engineered tissues. The understanding and control of these vascularization processes are a key factor for creating thicker functional tissues. Here, we show that cardiac cell sheets express angiogenesis-related genes and form endothelial cell networks in culture. After non-invasive harvest and stacking of cell sheets using temperature-responsive culture dishes, these endothelial cell networks are maintained and result in neovascularization upon in vivo transplantation. Interestingly, we also discovered that all of the graft vessels are derived from the grafts themselves and these vessels migrate to connect with the host vasculature. Finally, blood vessel formation within the grafts can be controlled by changing the ratio of endothelial cells. In conclusion, myocardial tissue grafts engineered with cell sheet technology have their own inherent potential for the in vivo neovascularization that can be regulated in vitro.

Animals↗

PubMed2006

Demonstration of a PDMS-based bio-microactuator using cultured cardiomyocytes to drive polymer micropillars.

Natural cellular functions are increasingly exploited for integrated chemical systems such as biochemical reactors and biosensors. We propose to utilize the intrinsic mechanical function of cardiomyocytes, converting chemical energy into mechanical energy. In this report, we demonstrate the working principle of our proposed poly(dimethylsiloxane) (PDMS) based cardiomyocyte bio-microactuator using fabricated PDMS micropillars driven to repetitive motion by attached pulsating cardiomyocytes. Sheets of PDMS embedded with an array of micropillars were fabricated and modified for cardiomyocyte attachment in culture. Primary neonatal rat cardiomyocytes were cultured on the array, attaching to the micropillars and substratum successfully, and exhibiting their typical spontaneous, pulsatile phenotype. Micropillars beat with the coupled cells spontaneously without any triggers. The beat frequency was 1.4 Hz at 37 degrees C and the displacement of the top of the pillar that beat most strongly in our observation was 2.8+/-0.2 microm. From this result, contractile forces of cultured cardiomyocytes were estimated to exceed 3.5 microN. The estimated force is far greater than that of a previously described hydrogel-based cardiomyocyte bio-microactuator (K. Morishima et al., in Micro Total Analysis Systems 2003, ed. M. A. Northrup et al., The Transducers Research Foundation, San Diego, CA, vol. 2, pp. 1125-1128). PDMS compatibility as a base material for bio-microactuator design using cultured cardiomyocytes was verified. This PDMS-based cell microactuator worked for about one week without exchange of the culture medium, and this system could be developed for various purposes in the future as self-actuated and efficient mechanochemical transducers without external energy source requirements.

Algorithms↗

PubMed2006

Cardiomyocyte bridging between hearts and bioengineered myocardial tissues with mesenchymal transition of mesothelial cells.

BACKGROUND: For the reconstruction of 3-dimensional (3D) tissues, we exploited an original method of tissue engineering that layers individual cell sheets harvested from temperature-responsive culture dishes. Stacked cardiomyocyte sheets demonstrated electrical and morphologic communication, resulting in synchronously beating myocardial tissue. When these bioengineered 3D tissue grafts are transplanted onto damaged hearts, gap junction communication between graft and host is likely critical for synchronized beating and functional improvement. In this study, these graft-to-heart morphologic communications were examined. METHODS: Neonatal rat cardiomyocyte sheets were harvested from temperature-responsive culture dishes and layered to create 3D tissues. These constructs were then transplanted onto infarcted rat hearts. Histologic analyses and transmission electron microscopy (TEM) were performed to examine morphologic communications. The passage of small molecules through functional gap junctions was also detected using a dye-transfer assay. RESULTS: Transplanted cardiomyocytes bridged between the grafts and hearts in intact areas. Connexin-43 staining and TEM revealed the existence of gap junctions and intercalated disks between the bridging cardiomyocytes. Furthermore, it was confirmed that a low-molecule fluorescent dye, calcein, was transferred from the grafts to the hearts via the bridging cardiomyocytes. Immunohistochemistry with anti-intercellular adhesion molecule-1 antibodies revealed that mesothelial cells in the epicardium scattered and transdifferentiated into mesenchymal cells between the graft and host. CONCLUSIONS: The direct attachment of layered cardiomyocyte sheets on the heart surface promotes mesothelial cell transdifferentiation and cardiomyocyte bridging, leading to functional communication via gap junctions. These results indicate that these bioengineered myocardial tissues may improve damaged heart function via synchronized beating.

Animals↗

PubMed2006

Grafted skeletal myoblast sheets attenuate myocardial remodeling in pacing-induced canine heart failure model.

OBJECTIVE: To overcome problems related to the intramyocardial injection of cells, including cell loss and a limited graft area, we developed a cell delivery system that uses tissue-engineered myoblast grafts grown as sheets. Here, we assessed the feasibility and efficacy of our method in a canine dilated cardiomyopathy model. METHODS: Skeletal myoblasts were incubated on temperature-responsive culture dishes, and the sheets of cells were detached by decreasing the temperature. Twelve dogs were given continuous ventricular pacing at 230 beats/min for 4 weeks; then the myoblast sheets (n = 5) were grafted onto the left ventricular wall or a sham operation was performed (n = 7). The number of cells was adjusted to 1.5 approximately 2.5 x 10(6) cells per graft, and each dog received approximately 20 grafts. RESULTS: The cell sheets were easily grafted onto a large area of the left ventricular surface, and there were no serious sequelae. Four weeks after graft implantation, echocardiography demonstrated that the left ventricular ejection fraction (graft, 26.0% +/- 5.6%; control, 19.5% +/- 6.8%; P < .05) and fractional shortening (graft, 17.9% +/- 3.6%; control, 7.8% +/- 2.1%; P < .05) were significantly ameliorated with reduced left ventricular dilatation (graft, 7.3 +/- 1.3 cm2; control, 10.2 +/- 0.4 cm2; P < .05) and increased wall thickness (graft, 5.6 +/- 0.7 mm; control, 4.4 +/- 0.6 mm; P < .05). Histologic evidence indicated the grafted myoblasts had survived, accompanied by a significant reduction in fibrosis and apoptosis, and a significant increase in proliferation. CONCLUSIONS: Grafting of skeletal myoblast sheets attenuated cardiac remodeling and improved cardiac performance. This novel method was feasible and effective in a large animal model, suggesting an innovative and promising strategy for treating patients with end-stage dilated cardiomyopathy.

Animals↗

PubMed2006

Corneal epithelial stem cell delivery using cell sheet engineering: not lost in transplantation.

Cell-based therapies have now generated significant interest as novel drug delivery systems, with various adult cell types used in treating a wide range of diseases. To overcome the limits that restrict treatments for corneal surface dysfunction, corneal epithelial stem cells expanded ex vivo have been applied as an alternative approach. While previous studies used various carrier substrates, we present a novel method using cell sheet engineering with temperature-responsive culture dishes to create carrier-free corneal epithelial stem cell sheets that can be transplanted without sutures. Results from clinical trials reveal successful transplantation with the recovery of lost visual acuity in all cases. Cell sheet engineering, therefore, presents a novel method for the delivery of corneal epithelial stem cells, and can also be applied for other approaches of cellular therapeutics.

Corneal Transplantation↗

PubMed2006

Long-term survival and growth of pulsatile myocardial tissue grafts engineered by the layering of cardiomyocyte sheets.

Recently researchers have attempted to bioengineer three-dimensional (3-D) myocardial tissues using cultured cells in order to repair damaged hearts. In contrast to the conventional approach of seeding cells onto 3-D biodegradable scaffolds, we have explored a novel technology called cell sheet engineering, which layers cell sheets to construct functional tissue grafts. In this study, in vivo survival, function, and morphology of myocardial tissue grafts were examined. Neonatal rat cardiomyocytes were noninvasively harvested as contiguous cell sheets from temperature-responsive culture dishes simply by reducing the culture temperature. Cardiomyocyte sheets were then layered and transplanted into the subcutaneous tissues of athymic rats. The microvasculature of the grafts was rapidly organized within a few days with macroscopic graft beatings observed 3 days after transplantation and preserved up to one year. Size, conduction velocity, and contractile force of transplanted grafts increased in proportion to the host growth. Histological studies showed characteristic structures of heart tissue, including elongated cardiomyocytes, well-differentiated sarcomeres, and gap junctions within the grafts. In conclusion, long-term survival and growth of pulsatile myocardial tissue grafts fabricated by layering cell sheets were confirmed, demonstrating that myocardial tissue regeneration based on cell sheet engineering may prove useful for permanent myocardial tissue repair.

Animals↗

PubMed2006

Nestin expression in vascular malformations: a novel marker for proliferative endothelium.

Cavernous angiomas (CAs) and arteriovenous malformations (AVMs) sometimes show growth or de novo appearance. Proliferative capacity of the endothelium is evident in such malformations. Intermediate filament nestin is a newly identified marker for proliferative endothelium, which was originally detected in the neuroepithelial stem cells of the embryonal central nervous system. Immunohistochemical analysis of nestin was evaluated as a marker for proliferative capacity of endothelial cells by comparison with proliferating cell nuclear antigen (PCNA). Sixteen of 27 CAs and 13 of 20 AVMs were positive for nestin. Likewise, 12 of 27 CAs and 10 of 20 AVMs were positive for PCNA. Nestin staining was stronger in the typical malformative vessels of CAs than in AVMs, in both the endothelial cells and the interstitial cells. Newly formed endothelial cells expressed nestin strongly in the reactive tissues including organizing or encapsulated hematomas. These results suggest that neovascularization occurs in the process of repeated bleeding and remodeling of hematomas.

Adolescent↗

PubMed2006

A new model of focal cerebral ischemia in the miniature pig.

OBJECT: The purpose of this set of studies is to design a minimally invasive, reproducible stroke model in the gyrencephalic brain. This paper provides information on both surgical technique and methods of quantification of ischemic damage to both gray and white matter in the miniature pig. METHODS: Sixteen male miniature pigs were randomly divided into three groups and underwent transcranial surgery involving a frontotemporal approach with orbital rim osteotomy for permanent middle cerebral artery occlusion (MCAO; five animals), permanent internal carotid artery occlusion (ICAO; six animals), and a sham operation (five animals). Histological mapping and magnetic resonance (MR) imaging were used to delineate the areas of ischemic damage. The volumes of infarction measured directly from MR images were 16.2 +/- 1.1, 1.5 +/- 0.5, and 0.0 +/- 0.0 cm3 (mean +/- standard deviation [SD], p < 0.001) in the MCAO, ICAO, and sham-operated groups, respectively. The areas of ischemia identified through histological analysis and MR imaging showed a good correlation (r2 = 0.86, p < 0.0001). Immunohistochemical staining with an amyloid precursor protein (APP) antibody was used to evaluate axonal damage and calculate a total APP score for axonal damage of 44.8 +/- 2.9 in the MCAO, 13.2 +/- 6.6 in the ICAO, and 0.0 +/- 0.0 (mean +/- SD, p < 0.002) in the sham-operated animals. CONCLUSIONS: This new model of focal cerebral ischemia induces a reproducible amount of ischemic damage in both gray and white matter, and has significant utility for studies of the pathophysiology of ischemia in the gyrencephalic brain and for assessment of the therapeutic efficacy of drugs prior to the initiation of human clinical trials.

Animals↗

PubMed2006

[Regenerative therapy for damaged heart].

Regeneration therapy has currently emerged as one of the promising treatments for the patients suffering from severe heart dysfunction. Direct transplantation of isolated myoblasts or bone marrow mononuclear cells, and recruitment of stem cells from bone marrow by G-CSF administration have been already clinically performed. As further advanced therapy, research on fabricating three-dimensional (3-D) cardiac grafts by tissue engineering technology has also now begun. Most popular approach of tissue engineering is using 3-D biodegradable scaffolds as alternatives of extracellular matrix. By contrast, we have successfully fabricated macroscopically beating myocardial tissue by layering cell sheets which are harvested from intelligent culture dishes grafted with temperature-responsive polymer in nano-scale. These regenerative medicines should rescue many patients.

Animals↗

PubMed2005

Tissue cardiomyoplasty using bioengineered contractile cardiomyocyte sheets to repair damaged myocardium: their integration with recipient myocardium.

BACKGROUND: We hypothesized that tissue-engineered contractile cardiomyocyte sheets without a scaffold would show histological and electrical integration with impaired myocardium, leading to the regeneration of infarcted myocardium. METHODS: Neonatal rat cardiomyocytes were cultured on Poly(N-isopropylacrylamide)-grafted polystyrene dishes and detached as a square cell sheet at 20 degrees C. Two sheets were stacked to make thicker contractile cardiac sheets. In cross-section, the stacked sheets looked like homogeneous heart-like tissue. Two weeks after rats were subjected to left anterior descending (LAD) ligation, two treatments were conducted: 1) cardiomyocyte sheet implantation (T group, n=10), and 2) fibroblast sheet implantation (F group, n=10). The control group underwent no additional treatment (C group, n=10). RESULTS: Echocardiography demonstrated that cardiac performance was significantly ameliorated in the T group 2, 4, and 8 weeks after implantation. The cardiomyocyte sheets became attached to the infarcted myocardium, showed angiogenesis, expressed connexin-43, and appeared as homogeneous tissue in the myocardium Electrophysiological experiments showed a QRS complex with one peak in the treated scar area in the T group, but two peaks, indicative of branch block, in that of the other groups. Furthermore, the threshold for pacing of the recipient heart was lower in the T group than in the other groups. CONCLUSIONS: Cardiomyocyte sheets integrated with the impaired myocardium and improved cardiac performance in a model of ischemic myocardium. Techniques using such tissue-engineered cell sheets are introducing the promising concept of tissue cardiomyoplasty to the field of regenerative medicine.

Animals↗