Double-layered Cell Research Articles

What is Multi-extreme THz ESR? Developments and its Applications

AbstractThis review explores the multi-extreme THz ESR system in Kobe, Japan, with a focus on pulsed magnetic fields, mechanical detection, and high pressure as central elements of multi-extreme THz ESR. Initially, it discusses the advantages of multi-frequency THz ESR using mini-pulsed and 55 T‒pulsed magnetic fields, with typical examples featuring the finite Haldane chain substance Y2BaNi0.96Mg0.04O5 and the deformed diamond chain antiferromagnet Cu3(CO3)2(OH)2 (Azurite). The measurement efficiency and the measurement beyond the magnetic phase transition, in contrast to the conventional superconducting magnet, are discussed. Second, the high sensitivity obtained from the use of a nano-membrane for mechanical detection is shown. Also shown are the high-temperature (280 K) THz ESR results for DPPH powder and a Cu(C4H4N2)(NO3)2 (CuPzN) single crystal, with the combination of a nano-membrane device and a high-power source, a gyrotron. Finally, the high-pressure THz ESR results for KCuCl3 using a transmission-type double-layered pressure cell are shown, along with the application of the thermally detected high-pressure THz ESR.

Synthesis and Characterization of DOTAM-Based Sideromycins for Bacterial Imaging and Antimicrobial Therapy.

The rise of antimicrobial resistance, especially in Gram-negative bacteria, calls for novel diagnostics and antibiotics. To efficiently penetrate their double-layered cell membrane, we conjugated the potent antibiotics daptomycin, vancomycin, and sorangicin A to catechol siderophores, which are actively internalized by the bacterial iron uptake machinery. LC-MS/MS uptake measurements of sorangicin derivatives verified that the conjugation led to a 100- to 525-fold enhanced uptake into bacteria compared to the free drug. However, the transfer to the cytosol was insufficient, which explains their lack of antibiotic efficacy. Potent antimicrobial effects were observed for the daptomycin conjugate 7 (∼1 μM) against multidrug-resistant Acinetobacter baumannii. A cyanin-7 label aside the daptomycin warhead furnished the theranostic 13 that retained its antibiotic activity and was also able to label ESKAPE bacteria, as demonstrated by microscopy and fluorescence assays. 13 and the cyanin-7 imaging conjugate 14 were stable in human plasma and had low plasma protein binding and cytotoxicity.

Probing the Double-Layered Cotyledon Cell Structure of Navy Beans: Barrier Effect of the Protein Matrix on In Vitro Starch Digestion

The microstructure of legumes plays a crucial role in regulating starch digestion and postprandial glycemic responses. Starch granules are double encapsulated within the outer cell wall and the inner protein matrix of legume cotyledon cells. Despite progress in understanding the role of cell walls in delaying starch digestion, the role of the protein matrix has received little research attention. The aim of this study was to evaluate if the protein matrix and cell wall may present combined physical barriers retarding enzyme hydrolysis of intracellular starch. Intact cotyledon cells were isolated from navy beans and used to assess the barrier effect of the protein matrix on the digestion of starch under conditions simulating the upper gastrointestinal tract. The cells were pretreated with pepsin at 37 °C and pH 2.0 for 1, 4, or 24 h and without pepsin for 24 h (control) to facilitate removal of the intracellular protein matrix prior to cooking and simulated in vitro digestion. A longer pretreatment time resulted in a lower protein content of the cells and a higher initial rate and extent of starch hydrolysis. We suggest that in addition to the primary cell wall barrier, the protein matrix provides a secondary barrier restricting the accessibility of α-amylase to starch. This study provides a new fundamental understanding of the relationship between the structural organization of legume cotyledon cells and starch digestion that could inform the design of novel low glycemic index foods.

Double-layered two-directional somatopleural cell migration during chicken body wall development revealed with local fluorescent tissue labeling.

The thoracic ventral body wall consists of the rib, the sternum, the intercostal muscles, and the connective tissues surrounding them. The ribs and the intercostal muscles are derived from the somite. The connective tissues are derived from the somatic layer of the lateral plate mesoderm, somatopleure. The lateral growth of the somatopleure forms the primary ventral body wall. The migration of somitic cells into the somatopleure generates the secondary body wall. As the migrating behavior of the somatopleural cells during secondary body wall formation is still unclear, we investigate here the migratory behavior of the somatopleural cells in the thorax during chicken ventral body wall development by labeling the thoracic somatopleural cells one-somite-wide by DiI labeling or gene transfection of the enhanced green fluorescent protein and observe their distribution assisted by the tissue-clearing technique FRUIT. Our labeling experiments revealed the rostral migration of the somatopleural cells into a deep part of the thoracic body wall in embryonic day 6.5 chickens. For embryonic day 8.5 chickens, these deep-migrating somatopleural cells were found around the sternal ribs. Thus, we identified the double-layered two-directional migrating pathways of the somatopleural cells: the rostral migration of the deep somatopleural cells and the lateral migration of the superficial somatopleural cells. Our findings imply that the rostral migration of deep somatopleural cells and the lateral migration of superficial ones might be associated with the developing sternal ribs and the innervation of the thoracic cutaneous nerves, respectively.

Multilayered Cell Sheets of Cardiac Reprogrammed Cells for the Evaluation of Drug Cytotoxicity.

Various cell-culture systems have been used to evaluate drug toxicity in vitro. However, factors that affect cytotoxicity outcomes in drug toxicity evaluation systems remain elusive. In this study, we used multilayered sheets of cardiac-mimetic cells, which were reprogrammed from human fibroblasts, to investigate the effects of the layer number on drug cytotoxicity outcomes. Cell sheets of cardiac-mimetic cells were fabricated by reprogramming of human fibroblasts into cardiac-mimetic cells via coculture with cardiac cells and electric stimulation, as previously described. Double-layered cell sheets were prepared by stacking the cell sheets. The mono- and double-layered cell sheets were treated with 5-fluorouracil (5-FU), an anticancer drug, in vitro. Subsequently, apoptosis and lipid peroxidation were analyzed. Furthermore, effects of cardiac-mimetic cell density on cytotoxicity outcomes were evaluated by culturing cells in monolayer at various cell densities. The double-layered cell sheets exhibited lower cytotoxicity in terms of apoptosis and lipid peroxidation than the mono-layered sheets at the same 5-FU dose. In addition, the double-layered cell sheets showed better preservation of mitochondrial function and plasma membrane integrity than the monolayer sheets. The lower cytotoxicity outcomes in the double-layered cell sheets may be due to the higher intercellular interactions, as the cytotoxicity of 5-FU decreased with cell density in monolayer cultures of cardiac-mimetic cells. The layer number of cardiac-mimetic cell sheets affects drug cytotoxicity outcomes in drug toxicity tests. The in vitro cellular configuration that more closely mimics the in vivo configuration in the evaluation systems seems to exhibit lower cytotoxicity in response to drug.

Visible-light-driven photocatalytic disinfection of Aspergillus fumigatus under germinative biomorph: Efficiency and mechanism

The photocatalytic disinfection efficiency of fungi spores, especially Aspergillus spores, is much lower compared with bacteria and virus, particularly under visible light. It is quite necessary to develop new strategies and explore the mechanism for enhanced the visible-light-driven photocatalytic disinfection of Aspergillus spores. In this work, the visible-light-driven photocatalytic disinfection of Aspergillus fumigatus spores (a common Aspergillus species) under different biomorph were analysed by the prepared photocatalysts, such as g-C3N4 nanosheet, bulk Bi4O7, and g-C3N4/Bi4O7. When the A. fumigatus spores were under dormant biomorph, the prepared photocatalysts revealed barely photocatalytic disinfection efficiency. Whereas the A. fumigatus spores germinated (that is swelling and germination), the photocatalytic disinfection efficiency was remarkably enhanced. About 81% of the germinated A. fumigatus spores were inactivated by the optimal g-C3N4/Bi4O7-40 (the initial concentration is 1 × 104 CFU/mL). During the photocatalytic disinfection, the superoxide radicals (O2−), hydroxyl radicals (OH) were the prominent active constituents which were formed by the adsorbed oxygen and the adsorbed H2O. When the A. fumigatus spores were under dormant biomorph, the dense and complex cell wall could well protect from O2− and OH attacked. Significantly, when the A. fumigatus spores were under germinative biomorph, the double-layered cell wall remodeled and the metabolism accelerated which brought about the frequent exchange of substances between intracellular and extracellular. O2− and OH could likely interact with the germinated A. fumigatus spores, and decompose the cell wall and cytoplasm.

Distribution of fluoroquinolones in the two aqueous compartments of Escherichia coli

The double-layered cell envelope of Gram-negative bacteria and active drug efflux present a formidable barrier for antimicrobial compounds to penetrate. Fluoroquinolones are among the few classes of antimicrobials that are clinically useful in the treatment of Gram-negative bacterial infection. Previous studies on fluoroquinolone accumulation measured total bacteria associated compounds, rather than the cytoplasmic accumulation. Fluoroquinolones target the type II topoisomerases in the cytoplasm. Thus, the cytoplasmic accumulation is expected to be more relevant to the potency of the drugs. Here, we fractionated and measured the concentration of nine fluoroquinolone compounds in the periplasm and the cytoplasm of two strains of E. coli cells, a parent strain and its isogenic efflux-deficient tolC knockout strain. The potency of the drugs was determined using the minimum inhibitory concentration (MIC) assay. We found that all fluoroquinolones tested accumulated at much higher concentrations in the periplasm than in the cytoplasm. The periplasmic concentrations were 2–15 folds higher than the cytoplasmic concentration, while the actual distribution ratio varies drastically among the compounds tested. Good correlation between the MIC and the cytoplasmic accumulation, but not whole cell accumulation, was observed using a pair of isogenic wild type and drug-efflux deficient strains.

A novel method to align cells in a cardiac tissue-like construct fabricated by cell sheet-based tissue engineering.

Fabrication of cardiac tissue from human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) has received great interest, but a major challenge facing researchers is the alignment of cardiomyocytes in the same direction to optimize force generation. We have developed a novel method of fabricating a cardiac tissue-like construct with aligned cells based on the unidirectional stretching of an hiPS-CM sheet. A square cell sheet was harvested from a temperature-responsive culture dish and placed on a silicone surface, and an extending force was imposed on the silicone to stretch the cell sheet along one direction. To enable evaluation of cardiomyocyte morphology in vitro, a cell sheet was constructed by coculture of hiPS-CMs and human adipose-derived stem cells. In separate experiments, a stretched double-layered cell sheet constructed from hiPS-CMs alone was transplanted onto the muscle of an athymic rat, and its features were compared with those of a nonstretched (control) cell sheet. Immediately after stretching, the stretched cell sheet was significantly longer than the control cell sheet. Immunohistological analysis revealed that the cardiomyocytes showed unidirectional alignment in the stretched cell sheet but random directionality in the control cell sheet. Two weeks after transplantation, immunohistology demonstrated that the stretched cell sheet had retained the unidirectionality of its myocardial fibers and had an orientation intensity that was higher than that of the control cell sheet after transplantation or the stretched cell sheet before transplantation. Our technique provides a simple method of aligning an hiPS-CM-derived cardiac tissue-like construct without the use of a scaffold.

Enhancement of absorption and haze with hybrid anchoring of dye-doped cholesteric liquid crystals.

We demonstrated that hybrid anchoring of dye-doped cholesteric liquid crystals (ChLCs) could be used for the simultaneous control of haze and transmittance. Hybrid anchoring of ChLCs can be obtained by the vertical anchoring at one substrate surface and planar anchoring at the other substrate surface. In a ChLC cell with hybrid anchoring, the LCs near the planar alignment layer are in the planar state, while those near the vertical alignment layer are in the focal-conic state. In the initial opaque state, the incident light can be absorbed by the LC mixture in the planar state and scattered by the LCs in the focal-conic state. The ChLC cell with hybrid anchoring exhibited lower transmittance and haze value than those of a focal-conic state in a ChLC cell with vertical anchoring. The cell can be switched to the transparent state without use of a complicated drive scheme at a driving voltage significantly lower than that for a double-layered cell.

Evaluating the effects of IADHFL on inhibiting DPP-IV activity and expression in Caco-2 cells and contributing to the amount of insulin released from INS-1 cells in vitro.

Dipeptidyl peptidase-IV (DPP-IV) is a serine exo-peptidase that can inactivate incretins by removing N-terminal dipeptides. Currently, inhibiting the DPP-IV activity is a common treatment for type 2 diabetes (T2D). The goal of this study is to investigate whether IADHFL, a novel DPP-IV inhibitory peptide identified from bighead carp (Hypophthalmichthys nobilis), has the potential to modulate T2D. IADHFL remained stable after simulated gastrointestinal digestion and significantly decreased the activity and expression of both soluble and membrane-bound DPP-IV after 24 h and 48 h of treatment. Intact peptide absorption was observed, but a percentage of the peptide was degraded while passing through a monolayer of Caco-2 cells. In addition, a double-layered cell model showed that the peptide could increase insulin secretion from INS-1 cells after glucose treatments of 2.8 mM and 16.7 mM. Finally, IADHFL could regulate the expression levels of genes associated with insulin secretion and T2D in INS-1 cells.

Reversible Cell Layering for Heterogeneous Cell Assembly Mediated by Ionic Cross-Linking of Chitosan and a Functionalized Cell Surface Membrane

Current heterogeneous cell assembly techniques in coculture systems rely on irreversible cell layering or a cell separation membrane. However, the techniques possess major drawbacks of inefficiency in direct interactions of the assembled cell layers and cell separation following coculture, which hamper characterization and therapeutic applications of the cells following coculture. Here, we develop a reversible cell layering platform for assembly of heterogeneous cells that allows both active direct cell–cell interactions and facile cell separation. Anionic maleimide-chondroitin-sulfate is grafted onto the surface membrane of myogenic C2C12 cells and human mesenchymal stem cells (hMSCs) to modify the surface charge of the cells without cytotoxicity. A highly porous chitosan thin film is formed in situ interspacing between the heterogeneous cell layers via ionic cross-linking of cationic chitosan and anionic functionalized cells, forming compactly assembled double-layered cell constructs. The chitosan film ...

Double-layered cell transfer technology for bone regeneration.

For cell-based medicine, to mimic in vivo cellular localization, various tissue engineering approaches have been studied to obtain a desirable arrangement of cells on scaffold materials. We have developed a novel method of cell manipulation called “cell transfer technology”, enabling the transfer of cultured cells onto scaffold materials, and controlling cell topology. Here we show that using this technique, two different cell types can be transferred onto a scaffold surface as stable double layers or in patterned arrangements. Various combinations of adherent cells were transferred to a scaffold, amniotic membrane, in overlapping bilayers (double-layered cell transfer), and transferred cells showed stability upon deformations of the material including folding and trimming. Transplantation of mesenchymal stem cells from periodontal ligaments (PDLSC) and osteoblasts, using double-layered cell transfer significantly enhanced bone formation, when compared to single cell type transplantation. Our findings suggest that this double-layer cell transfer is useful to produce a cell transplantation material that can bear two cell layers. Moreover, the transplantation of an amniotic membrane with PDLSCs/osteoblasts by cell transfer technology has therapeutic potential for bone defects. We conclude that cell transfer technology provides a novel and unique cell transplantation method for bone regeneration.

Rapid fabrication system for three-dimensional tissues using cell sheet engineering and centrifugation.

Three-dimensional (3D) tissues can be reconstructed by cell sheet technology, and various clinical researches using these constructed tissues have already been initiated to regenerate damaged tissues. While 3D tissues can be easily fabricated by layering cell sheets, the attachment period for cell adhesion between a cell sheet and a culture dish, or double-layered cell sheets normally takes 20-30 min. This study proposed a more rapid fabrication system for bioengineered tissue using cell sheet technology and centrifugation. A C2C12 mouse myoblast sheet harvested from a temperature-responsive culture dish will attach tightly to a culture dish or another cell sheet at 37°C after a 20 min-incubation. However, the same cell sheet centrifuged (12-34 × g) for 3 min also attached tightly to a dish or another cell sheet at 37°C after only a 3 min-incubation. The manipulation time was reduced by approximately two-thirds by centrifugation. The rapid attachments were also cross-sectionally confirmed by optical coherence tomography. These rapidly constructed cell sheet-tissues using centrifugation showed active cell metabolism, cell viability, and very high production of vascular endothelial growth factor, like those prepared by the conventional method; indicating complete cell sheet-attachment without any cell damage. This new system will be a powerful tool in the fields of cell sheet-based tissue engineering and regenerative medicine, and accelerate the use of cell sheets in clinical applications.

175. Double-Layered Cell Sheets Transplantation That Achieves Durable Factor VIII Delivery in the Mouse Model of Hemophilia A

Hemophilia A is an inherited bleeding disorder caused by a deficiency of the procoagulant cofactor VIII (FVIII). Currently, the patients with hemophilia A are being treated through repeated intravenous injection of FVIII concentrates. Since FVIII is a secreted protein and the tight regulation of its expression is not necessary, ex vivo gene therapy strategies for hemophilia A might be good for the therapeutic alternative. We previously demonstrated that therapeutic levels of plasma FVIII were documented from hemophilia A mice over 300 days, in which lentivirally-engineered blood outgrowth endothelial cells (BOECs) sheet were implanted subcutaneously (Tatsumi K et.al. PLoS One 2013 8(12):e83280). To enhance the viability of the implanted BOECs which boost the FVIII expression, double-layered cell sheets transplantation was performed by placing the recovered BOECs sheet onto the fibroblast sheet directly. FVIII transduced BOECs and non-transduced fibroblasts were cultured on temperature-responsive culture dish independently. Both cells were recovered as a contiguous cell sheet. Subcutaneous co-transplantation studies of BOEC and fibroblast sheet indicated that all hemophilia A mice treated with cyclophosphamide expressed between 40-50 mU/mL levels of FVIII without developing anti-FVIII inhibitory antibodies over 200 days. In contrast, the hemophilia A mice without any prior immuno-suppressive treatment developed neutralizing anti-FVIII antibodies between 5-10 Bethesda units. These therapeutic FVIII levels were two times higher than the group of hemophilia A mice that were transplanted BOECs sheet alone. Histological examination in the part of the mice revealed that the combination of BOEC and fibroblast sheet was structured as flat clusters without any cells infiltration. In conclusion, tissue engineering approach using double-layered cell sheets are viable for persistent tissue survival and providing therapeutic values. This novel ex vivo gene transfer strategy can provide the safe and efficacious delivery of FVIII in hemophilia A and merits further assessment.

Double-layered silicon nitride antireflection coatings for multicrystalline silicon solar cells

Silicon nitride coating possesses both optical antireflection and electrical passivation effects for crystalline silicon solar cells. In this work, we employed a double-layered silicon nitride coating consisting of a top layer with a lower refractive index and a bottom layer (contacting the silicon wafer) with a higher refractive index for multicrystalline silicon solar cells. Double-layered silicon nitride coating provides a lower optical reflection and better surface passivation than those of single-layered silicon nitride. Details for optimizing the double-layered silicon nitride coating are presented. In order to get statistical conclusions, we fabricated a large number of multicrystalline silicon solar cells using the production line for both the double-layered and single-layered cell types. It was statistically demonstrated that the double-layered silicon nitride coating provided a consistent enhancement in the photovoltaic performance of multicrystalline silicon solar cells over those of the single-layered silicon nitride coating.

Large Resistance Ratio for High Reliability of Multi-Level Storage in Phase-Change Memory

Reliability (or stability) of multi-level storage (MLS) is the critical characteristics for multi-level cells. In order to improve reliability of MLS of phase-change memory, there are two effective approaches, (i) enlargement of the ratio between resistance levels and (ii) reduction of scattering of resistance level. On the basis of our experimental results, it is demonstrated that the Ge2Sb2Te5-based double-layered cell has a high ratio of highest to lowest levels up to two-to-three orders of magnitude, implying high reliability. The cells exhibit the possibility of stable switching for four-level storage.

Development of a New Assay System for Evaluating the Permeability of Various Substances Through Three-Dimensional Tissue

A novel assay system with cell-dense three-dimensional (3D) tissue was developed for measuring the permeability of substances. In this paper, the permeabilities of various molecules containing nutrients, a cytokine, and a chemokine were examined and analyzed. A single-layered cell sheet was approximately 20 mum thick, and as the number of layers of these cell sheets increased, so did the total thickness of the tissue. The diffusion rates of glucose and pyruvic acid were reduced to approximately 30-40% by a single-layered cell sheet compared with the control without the cell sheet, and the diffusion of both substances were completely inhibited by a quadruple-layered cell sheet. The diffusion rate of creatinin was reduced to approximately 50% and 15-20% by a single-layered and by a quintuplet-layered cell sheet, respectively. On the other hand, the diffusion rate of stromal cell-derived factor 1alpha, vascular endothelial growth factor, beta2-microglobulin, and transferrin was reduced to approximately 10%, 5%, 20%, and 10%, by only a single-layered cell sheet, respectively. The diffusion of these substances were completely inhibited by a double-layered cell sheet. These results show that the permeability of substances through 3D tissue significantly decreased with the increase of the molecular weight. Therefore, the system could give a simulated living-tissue condition for measuring the permeability of substances. To our knowledge, this is the first report about measuring the permeability of substances through cell-dense 3D tissues without scaffolds. The assay system is believed to contribute to the progress of physiology, metabology, biochemistry, and pharmacokinetics. Further, the system may give some hints for developing a new dialysis membrane technology for an artificial kidney.

Electrical interaction between cardiomyocyte sheets separated by non-cardiomyocyte sheets in heterogeneous tissues

Electrical coupling between cardiomyocytes is important in synchronous beating and normal heart functions. Cardiomyocytes are also electrically coupled to non-cardiomyocytes. The electrical interactions between cardiomyocytes and non-cardiomyocytes, or those between separated cardiomyocytes, are important for normal heart function because abnormalities of the coupling and variation of the cell population induce pathological heart functions and arrhythmias. In this study the three-dimensional time course of the electrical interaction between two rat neonatal cardiomyocyte sheets separated by non-cardiomyocyte sheets was analysed by a multiple-electrode extracellular recording system. The two cardiomyocyte sheets separated by a single- or double-layered mouse fibroblast NIH3T3 cell sheet coupled electrically at 113 +/- 28 or 287 +/- 87 min after layering, respectively. The time course of the electrical coupling, when the single-layer NIH3T3 cell sheet was inserted, is similar to that of a layered cardiomyocyte sheet. Immunocytological analysis and dye transfer assay suggested the formation of gap junctions at heterocellular junctions of cardiomyocytes and NIH3T3 cells. On the other hand, when a double-layered NIH3T3 cell sheet was inserted, an incomplete electrical coupling of two cardiomyocyte sheets, including a conduction delay, was observed. The electrical coupling of cardiomyocyte sheets was completely blocked (conduction block) by insertion of a triple-layered NIH3T3 cell sheet, a communication-defective HeLa cell sheet or a Ca(2+)-antagonist LaCl(3)-treated cell sheet. These electrophysiological analyses of heterogeneously stacked cell sheets might provide insights into complex electrical conduction systems that resemble those of native or damaged heart and transplanted tissues.

Programming margin enlargement by material engineering for multilevel storage in phase-change memory

In this work, we investigate the effect of the material engineering on programming margin in the double-layered phase-change memory, which is the most important parameter for the stability of multilevel storage. Compared with the TiN/SbTeN cell, the TiSiN/GeSbTe double-layered cell exhibits the resistance ratio of the highest to lowest resistance levels up to two to three orders of magnitude, indicating much larger programming margin and thus higher stability and/or more available levels. Our calculation results show that the resistivities of the top heating layer and the phase-change layer have a significant effect on the programming margin.

Invited Commentary

In recent years, stem cell therapy has received considerable attention as a novel therapeutic option for refractory congestive heart failure. Although the mechanisms through which these cells elicit functional improvement are yet to be fully determined, recent studies suggest that paracrine effects, rather than direct trans-differentiation of donor cells into cardiomyocytes, may predominate in augmenting postinfarction cardiac function. Progress in cell therapy, however, is hampered by suboptimal engraftment of donor cells into the myocardium, related to the extensive cell death that ensues from the hostile milieu into which the donor cells are introduced. This problem has stimulated further investigation of the use of bioengineered scaffolds as cell delivery vehicles, with the hope that these constructs may enhance cell retention and functional recovery. In this study, Hamdi and colleagues [1Hamdi H. Furuta A. Bellamy V. et al.Cell delivery: intramyocardial injections or epicardial deposition? A head-to-head comparison.Ann Thorac Surg. 2009; 87: 1196-1204Abstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar] evaluated the effect of differing cell delivery techniques on postinfarct heart function. Using skeletal myoblasts as donor cells in a rat infarct model, the authors compared the conventional intramyocardial injection technique with epicardial placement of two cell-seeded constructs, one made of a double-layered myoblast cell sheet and the other constructed from a cell-seeded Gelfoam (Pharmacia & Upjohn/Pfizer, New York, NY) patch. The authors concluded that the two epicardially delivered tissue scaffolds led to significant improvements in left ventricular ejection fraction (LVEF) compared with the controls injected with culture medium, whereas intramyocardial injection prevented further deterioration of ventricular function but did not improve LVEF. Histologic analysis also showed greater angiogenesis in the two epicardially treated groups. The major quandary posed by these findings is that the effects of the varying techniques of cell transfer were unrelated to the detectable persistence of the myoblasts at the studied time point. Analysis of cell engraftment revealed minimal donor cell retention, with residual human cells detected in only 2 of 7 hearts in each of the two groups treated with the epicardial scaffold. The authors attribute the between-group differences in LVEF to donor cell effects at earlier, unevaluated time points (ie, earlier than 1 month). Their analysis of cytokines 1 month after cell delivery showed no differences between groups that might explain differences in functional recovery, but this, like the absence of persistent donor cells, may merely be a reflection of the time point chosen. Somewhat surprisingly, end-systolic and end-diastolic volumes did not differ between groups. Thus, although the cell sheets and Gelfoam patch improved LVEF, they did not do so by reducing infarct expansion compared with intramyocardial injection. Ultimately, the lack of a demonstrable mechanism to explain the differences observed between groups somewhat limits the strength of the conclusions that can be drawn about the relative merits of these different cell delivery techniques. Regardless, this is a topical study that compares the conventional intramyocardial delivery method to two potentially attractive methods of epicardial delivery. The results are provocative, and should spur further investigation to determine whether there are intrinsic benefits in using biomaterials in the setting of a recent or remote myocardial infarction. If there are, what are the mechanisms through which these constructs exert synergistic effects with the seeded cells? The optimal cell type or mixture of cell types that is best suited to a particular scaffold material has not been determined, nor have the physical, electrical, or surface characteristics that render one cell type more appropriate for seeding than another. Those studies may eventually lead to the development of off-the-shelf bioengineered cell-seeded constructs that may sidestep the issues of cell harvesting, expansion, and delivery that complicate current applications of cell therapy. Cell Delivery: Intramyocardial Injections or Epicardial Deposition? A Head-to-Head ComparisonThe Annals of Thoracic SurgeryVol. 87Issue 4PreviewMultiple needle-based injections of cells in the myocardium are associated with a low engraftment rate, which may limit the benefits of the procedure. This study used skeletal myoblasts to perform a head-to-head comparison of conventional injections with epicardial deposition of scaffold-embedded cells. Full-Text PDF