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| Hybrid PGS-PCL microfibrous scaffolds with improved mechanical and biological properties.
July 30, 2010 at 10:22 PM
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| | Hybrid PGS-PCL microfibrous scaffolds with improved mechanical and biological properties. J Tissue Eng Regen Med. 2010 Jul 28; Authors: Sant S, Hwang CM, Lee SH, Khademhosseini A Poly(glycerol sebacate) (PGS) is a biodegradable elastomer that has generated great interest as a scaffold material due to its desirable mechanical properties. However, the use of PGS in tissue engineering is limited by difficulties in casting micro- and nanofibrous structures, due to high temperatures and vacuum required for its curing and limited solubility of the cured polymer. In this paper, we developed microfibrous scaffolds made from blends of PGS and poly(epsilon-caprolactone) (PCL) using a standard electrospinning set-up. At a given PGS:PCL ratio, higher voltage resulted in significantly smaller fibre diameters (reduced from approximately 4 microm to 2.8 microm; p < 0.05). Further increase in voltage resulted in the fusion of fibres. Similarly, higher PGS concentrations in the polymer blend resulted in significantly increased fibre diameter (p < 0.01). We further compared the mechanical properties of electrospun PGS:PCL scaffolds with those made from PCL. Scaffolds with higher PGS concentrations showed higher elastic modulus (EM), ultimate tensile strength (UTS) and ultimate elongation (UE) (p < 0.01) without the need for thermal curing or photocrosslinking. Biological evaluation of these scaffolds showed significantly improved HUVEC attachment and proliferation compared to PCL-only scaffolds (p < 0.05). Thus, we have demonstrated that simple blends of PGS prepolymer with PCL can be used to fabricate microfibrous scaffolds with mechanical properties in the range of a human aortic valve leaflet. Copyright (c) 2010 John Wiley & Sons, Ltd. PMID: 20669260 [PubMed - as supplied by publisher] | | |
| Feasibility of using sodium chloride as a tracer for the characterization of the distribution of matter in complex multi-compartment 3D bioreactors for stem cell culture.
July 30, 2010 at 10:22 PM
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| | Feasibility of using sodium chloride as a tracer for the characterization of the distribution of matter in complex multi-compartment 3D bioreactors for stem cell culture. Int J Artif Organs. 2010 Jun;33(6):399-404 Authors: Gerlach JC, Witaschek T, Strobel C, Brayfield CA, Bornemann R, Catapano G, Zeilinger K The experimental characterization of the distribution of matter in complex multi-compartment three-dimensional membrane bioreactors for human cell culture is complicated by tracer interactions with the membranes and other bioreactor constituents. This is due to the fact that membranes with a high specific surface area often feature a hydrophobic chemical backbone that may adsorb tracers often used to this purpose, such as proteins and dyes. Membrane selectivity, and its worsening caused by protein adsorption, may also hinder tracer transfer across neighboring compartments, thus preventing effective characterization of the distribution of matter in the whole bioreactor. ?Tracer experiments with sodium chloride (NaCl) may overcome some of these limitations and be effectively used to characterize the distribution of matter in complex 3D multi-compartments membrane bioreactors for stem cell culture. NaCl freely permeates most used membranes, it does not adsorb on uncharged membranes, and its concentration may be accurately measured in terms of solution conductivity. In this preliminary study, the feasibility of complex multi-compartment membrane bioreactors was investigated with a NaCl concentration pulse challenge to characterize how their distribution of matter changes when they are operated under different conditions. In particular, bioreactors consisting of three different membrane types stacked on top of one another to form a 3D network were characterized under different feed conditions. PMID: 20669145 [PubMed - in process] | | |
| Perfusion enhances solute transfer into the shell of hollow fiber membrane bioreactors for bone tissue engineering.
July 30, 2010 at 10:22 PM
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| | Perfusion enhances solute transfer into the shell of hollow fiber membrane bioreactors for bone tissue engineering. Int J Artif Organs. 2010 Jun;33(6):381-90 Authors: De Napoli IE, Catapano G Preparation of tissue engineered (TE) 3D constructs to repair large bone defects is limited by the difficult supply of nutrients and oxygen to cells in the innermost regions of constructs cultured in bioreactors. Poor oxygenation negatively affects cell viability and function. Bioreactor design optimization may help relieve these limitations. Bioreactors in which cells are cultured outside bundles of hollow fiber membranes (HFMBs) are structurally similar to natural bone. HFMB operation in pure diffusion has been reported to suffice for fibroblasts, but is deemed insufficient for bone cells. In this paper, the effect of perfusion flows in the cell compartment on solute transfer was investigated in HFMBs differing in design and operating conditions. HFMBs were designed and operated using values of non-dimensional groups that ensured solutes transfer towards the cell compartment mainly by diffusion; in the presence of low to high Starling flows; in the presence of pulsatile radial flows obtained by periodically stopping the solution flow leaving the bioreactor using a pinch valve. Distribution of matter in cell-free HFMBs was evaluated with tracer experiments in an optimized apparatus. Effectiveness of solute transfer to cell compartment was assessed based on the bioreactor response in terms of the shell volume actively involved in mass transfer (VMTA ) according to transport models developed specifically for the purpose. VMTA increased with increasing Starling flows. In the pulsatile radial flow mode, tracer concentration in the shell increased 3 times faster than at high Starling flows. This suggests that controlled perfusion flows in HFMBs might enable the engineering of large TE bone constructs. PMID: 20669143 [PubMed - in process] | | |
| A three-dimensional traction/torsion bioreactor system for tissue engineering.
July 30, 2010 at 10:22 PM
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| | A three-dimensional traction/torsion bioreactor system for tissue engineering. Int J Artif Organs. 2010 Jun;33(6):362-9 Authors: Scaglione S, Zerega B, Badano R, Benatti U, Fato M, Quarto R Purpose: The aim of this study was to design, develop and validate a simple, compact bioreactor system for tissue engineering. The resulting bioreactor was designed to achieve ease-of-use and low costs for automated cell-culturing procedures onto three-dimensional scaffolds under controlled torsion/traction regimes. ?Methods: Highly porous poly-caprolactone-based scaffolds were used as substrates colonized by fibroblast cells (3T3 cell line). Constructs were placed within the cylindrical culture chamber, clumped at the ends and exposed to controlled sequences of torsional stimuli (forward/back-forward sequential cycles of 100 degrees from neutral position at a rate of 600 degrees /min) through a stepper-motor; working settings were defined via PC by an easy user-interface. Cell adhesion, morphology, cytoskeletal fiber orientation and gene expression of extracellular matrix proteins (collagen type I, tenascin C, collagen type III) were evaluated after three days of torsional stimulation in the bioreactor system. ?Results and Conclusions: The 3D bioreactor system was validated in terms of sterility, experimental reproducibility and flexibility. Cells adhered well onto the polymeric scaffolds. Collagen type I, tenascin C and collagen type III gene expression were significantly up-regulated when cells were cultured under torsion in the bioreactor for three days. In conclusion, we have developed a simple, efficient and versatile 3D cell-culture system to engineer ligament grafts. This system can be used either as a model to investigate mechanisms of tissue development or as a graft manufacturing system for possible clinical use in the field of regenerative medicine. PMID: 20669141 [PubMed - in process] | | |
| Effects of low concentrated BMP-7 administered by co-cultivation or plasmid transfection on human osteoarthritic chondrocytes.
July 30, 2010 at 10:22 PM
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| | Effects of low concentrated BMP-7 administered by co-cultivation or plasmid transfection on human osteoarthritic chondrocytes. Int J Artif Organs. 2010 Jun;33(6):339-47 Authors: Gavenis K, Schneider U, Wallich R, Mueller-Rath R, Schmidt-Rohlfing B, Andereya S Introduction: While BMP-7 has proven to be one of the most potent growth factors in cartilage tissue engineering, protein concentration and route of administration remain a matter of debate. Here we investigated the effects of a low concentration of BMP-7 on human osteoarthritic chondrocytes administered by protein co-cultivation and plasmid transfection. Methods: Freshly released (P0) or in vitro propagated chondrocytes (P2) were cultivated in a collagen type-I gel for 3 weeks in vitro or in nude mice. Seeded chondrocytes were treated with 50 ng/mL BMP-7 directly added to the medium or were subject to transient BMP-7 plasmid transfection prior to gel cultivation. Untreated specimens served as a control. After recovery, samples were investigated by histological and immunohistochemical staining and real-time PCR. Results: In vitro, collagen type-II protein production was enhanced, and it was stored mainly pericellularly. Collagen type-II and aggrecan gene expression were enhanced in both treatment groups. After nude mouse cultivation, col-II protein production was further enhanced, but specimens of the BMP-7 transfection group revealed a clustering of col-II positive cells. Gene expression was strongly upregulated, chondrocyte number was increased and the differentiated phenotype prevailed. In general, freshly released chondrocytes (P0) proved to be superior to chondrocytes pre-amplified in vitro (P2). Conclusions: Both BMP-7 co-cultivation and plasmid transfection of human osteoarthritic chondrocytes led to improved cartilage repair tissue. Nevertheless, the col-II distribution following BMP-7 co-cultivation was homogeneous, while samples produced by transient transfection revealed a col-II clustering. PMID: 20669139 [PubMed - in process] | | |
| The National Stem Cell Therapy Patient Registry of Malaysia-Measuring Clinical Outcomes of Stem Cell Therapy.
July 30, 2010 at 10:22 PM
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| | The National Stem Cell Therapy Patient Registry of Malaysia-Measuring Clinical Outcomes of Stem Cell Therapy. Stem Cell Rev. 2010 Jul 29; Authors: Loke SC, Chin SP, Sivanandam S, Goh PP, Ng RK, Saw KY, Lim TO Very few registries worldwide focus on clinical outcomes of stem cell therapy (SCT) as the large number of applications and rapid development of the field complicates registry design considerably. The National Stem Cell Therapy Patient Registry of Malaysia aims to accommodate this by using a main protocol which covers the overall design and administration of the registry, and condition-specific sub-protocols which deal with outcome measures. The registry will start with a few sub-protocols covering existing modes of SCT in Malaysia, with new sub-protocols released periodically as the need arises. PMID: 20669056 [PubMed - as supplied by publisher] | | |
| Hypertrophy, gene expression, and beating of neonatal cardiac myocytes are affected by microdomain heterogeneity in 3D.
July 30, 2010 at 10:22 PM
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| | Hypertrophy, gene expression, and beating of neonatal cardiac myocytes are affected by microdomain heterogeneity in 3D. Biomed Microdevices. 2010 Jul 29; Authors: Curtis MW, Sharma S, Desai TA, Russell B Cardiac myocytes are known to be influenced by the rigidity and topography of their physical microenvironment. It was hypothesized that 3D heterogeneity introduced by purely physical microdomains regulates cardiac myocyte size and contraction. This was tested in vitro using polymeric microstructures (G' = 1.66 GPa) suspended with random orientation in 3D by a soft Matrigel matrix (G' = 22.9 Pa). After 10 days of culture, the presence of 100 mum-long microstructures in 3D gels induced fold increases in neonatal rat ventricular myocyte size (1.61 +/- 0.06, p < 0.01) and total protein/cell ratios (1.43 +/- 0.08, p < 0.05) that were comparable to those induced chemically by 50 muM phenylephrine treatment. Upon attachment to microstructures, individual myocytes also had larger cross-sectional areas (1.57 +/- 0.05, p < 0.01) and higher average rates of spontaneous contraction (2.01 +/- 0.08, p < 0.01) than unattached myocytes. Furthermore, the inclusion of microstructures in myocyte-seeded gels caused significant increases in the expression of beta-1 adrenergic receptor (beta1-AR, 1.19 +/- 0.01), cardiac ankyrin repeat protein (CARP, 1.26 +/- 0.02), and sarcoplasmic reticulum calcium-ATPase (SERCA2, 1.59 +/- 0.12, p < 0.05), genes implicated in hypertrophy and contractile activity. Together, the results demonstrate that cardiac myocyte behavior can be controlled through local 3D microdomains alone. This approach of defining physical cues as independent features may help to advance the elemental design considerations for scaffolds in cardiac tissue engineering and therapeutic microdevices. PMID: 20668947 [PubMed - as supplied by publisher] | | |
| An Adult Myometrial Pluripotential Precursor that Promotes Healing of Damaged Muscular Tissues.
July 30, 2010 at 10:22 PM
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| | An Adult Myometrial Pluripotential Precursor that Promotes Healing of Damaged Muscular Tissues. In Vivo. 2010 Jul-Aug;24(4):431-41 Authors: Gálvez BG, MartÃn NS, Salama-Cohen P, Lazcano JJ, Coronado MJ, Lamelas ML, Alvarez-Barrientes A, Eiró N, Vizoso F, RodrÃguez C The use of adult stem cells for tissue and organ regeneration constitutes a promising alternative therapy in many human diseases that are currently not treatable. We have isolated a new cell type from mouse adult uterine biopsies (murine adult myometrial precursors or mAMPs) by means of using a simple and non-invasive approach. These cells have been characterized by surface markers, being positive for CD31, CD34, CD44, CD117, Stro-1 and Sca-1. A similar cell population (hAMPs) was isolated from human biopsies. AMPs can differentiate in vitro into a number of mesodermal (smooth and skeletal muscle, osteoblasts and adipocytes) as well as epidermal lineages (all neural lineages). AMPs are unusual adult stem cells as they still express some embryonic antigens and remain undifferentiated through a high number of passages before entering senescence. Importantly, when injected into animal models of muscular disease, AMPs can regenerate new muscle fibers, and promote functional muscular recovery. Moreover, these cells can regenerate the uterine lining after wound healing, reconstructing the uterine muscular architecture. In addition, these cells can form new vessels both in vitro and in vivo. We believe that these cells have superior features to other known adult stem cells and, consequently, their use holds great promise for regenerative medicine, drug development and basic research. PMID: 20668309 [PubMed - in process] | | |
| The wnt signaling pathway as a potential target for therapies to enhance bone repair.
July 30, 2010 at 10:22 PM
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| | The wnt signaling pathway as a potential target for therapies to enhance bone repair. Sci Transl Med. 2010 Jul 28;2(42):42ps36 Authors: Einhorn TA The development of new technologies to enhance skeletal healing after fracture or surgery is an important goal of musculoskeletal regenerative medicine. Although the bone morphogenetic proteins have shown some efficacy in this area, there is a need for more effective and less expensive therapies for bone repair and regeneration. A recent report demonstrating that Wnt signaling could be used to stimulate bone healing may provide a new direction for designing anabolic therapies for the skeleton. The identification of human phenotypes demonstrating robust bone formation as a result of mutations in Wnt signaling provides a strong basis for pursuing this area of investigation. PMID: 20668295 [PubMed - in process] | | |
| Cell-Mediated Neuroprotection in a Mouse Model of Human Tauopathy.
July 30, 2010 at 10:22 PM
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| | Cell-Mediated Neuroprotection in a Mouse Model of Human Tauopathy. J Neurosci. 2010 Jul 28;30(30):9973-9983 Authors: Hampton DW, Webber DJ, Bilican B, Goedert M, Spillantini MG, Chandran S Tau protein in a hyperphosphorylated state makes up the intracellular inclusions of several neurodegenerative diseases, including Alzheimer's disease and cases of frontotemporal dementia. Mutations in Tau cause familial forms of frontotemporal dementia, establishing that dysfunction of tau protein is sufficient to cause neurodegeneration and dementia. Transgenic mice expressing human mutant tau in neurons exhibit the essential features of tauopathies, including neurodegeneration and abundant filaments composed of hyperphosphorylated tau. Here we show that a previously described mouse line transgenic for human P301S tau exhibits an age-related, layer-specific loss of superficial cortical neurons, similar to what has been observed in human frontotemporal dementias. We also show that focal neural precursor cell implantation, resulting in glial cell differentiation, leads to the sustained rescue of cortical neurons. Together with evidence indicating that astrocyte transplantation may be neuroprotective, our findings suggest a beneficial role for glial cell-based repair in neurodegenerative diseases. PMID: 20668182 [PubMed - as supplied by publisher] | | |
| Cardiac stem cell therapy: progress from the bench to bedside.
July 30, 2010 at 10:22 PM
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| | Cardiac stem cell therapy: progress from the bench to bedside. Heart. 2010 Jul 28; Authors: Lovell MJ, Mathur A In the rush to assess the role of stem cell therapy for cardiovascular disease the details of translation are easily overlooked. This review summarises the progress to date in translating the exciting preclinical results of cardiac repair into man and considers the questions that this area of research has stimulated about the challenges of moving from bench to bedside. PMID: 20668107 [PubMed - as supplied by publisher] | | |
| Enhanced proteolytic degradation of molecularly engineered PEG hydrogels in response to MMP-1 and MMP-2.
July 30, 2010 at 10:22 PM
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| | Enhanced proteolytic degradation of molecularly engineered PEG hydrogels in response to MMP-1 and MMP-2. Biomaterials. 2010 Jul 26; Authors: Patterson J, Hubbell JA Bioactive hydrogels formed by Michael-type addition reactions of end-functionalized poly(ethylene glycol) macromers with cysteine-containing peptides have been described as extracellular matrix mimetics and tissue engineering scaffolds. Although these materials have shown favorable behavior in vivo in tissue repair, we sought to develop materials formulations that would be more rapidly responsive to cell-induced enzymatic remodeling. In this study, protease-sensitive peptides that have increased k(cat) values were characterized and evaluated for their effects on gel degradability. Biochemical properties for soluble peptides and hydrogels were examined for matrix metalloproteinase (MMP)-1 and MMP-2. The most efficient peptide substrates in some cases overlap and in other cases differ between the two enzymes tested, and a range of k(cat) values was obtained. For each enzyme, hydrogels formed using the peptides with higher k(cat) values degraded faster than a reference with lower k(cat). Fibroblasts showed increased cell spreading and proliferation when cultured in 3D hydrogels with faster degrading peptides, and more cell invasion from aortic ring segments embedded in the hydrogels was observed. These faster degrading gels should provide matrices that are easier for cells to remodel and lead to increased cellular infiltration and potentially more robust healing in vivo. PMID: 20667588 [PubMed - as supplied by publisher] | | |
| Three-dimensional microstructured tissue scaffolds fabricated by two-photon laser scanning photolithography.
July 30, 2010 at 10:22 PM
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| | Three-dimensional microstructured tissue scaffolds fabricated by two-photon laser scanning photolithography. Biomaterials. 2010 Jul 25; Authors: Hsieh TM, Benjamin Ng CW, Narayanan K, Wan AC, Ying JY Current tissue engineering scaffolds fabricated via solvent casting and porogen leaching methods suffer from the lack of control over parameters such as interconnectivity and pore geometry, properties that are a function of the fabrication process. The progress of tissue engineering would thus benefit from the ability to design scaffolds that facilitate cell-cell interactions, and provide mass transfer characteristics necessary for good cell viability and function. In this research, we have developed two-photon laser scanning photolithography (TPLSP) for the fabrication of three-dimensional (3D) microstructured scaffolds with high resolution and fidelity. Modification of our two-photon setup allowed for a scan height of 30 mm and a scan speed of 30 mm/s, making it more amenable to scaffold fabrication. Scaffold production was adapted to computer-aided design (CAD)/computer-aided manufacturing (CAM) technology, to achieve the desired length scales from the submicron level and up. A commercially available photocurable resin that exhibited favorable ultraviolet-visible (UV-vis) transparency, cell compatibility and reproducibility in fabrication was used as the scaffold material. As a proof-of-concept, a microporous, cubic scaffold was fabricated for the purpose of hepatocyte culture. Primary hepatocytes could be uniformly seeded on these scaffolds as observed by confocal fluorescence microscopy. Albumin and urea assays demonstrated that hepatocytes cultured in the 3D scaffold maintained higher levels of liver-specific function over a period of 6 days as compared to the monolayer control. These results may be attributed to the high local concentration of soluble factors within the scaffold, which is important for maintaining the hepatocyte phenotype. Our study illustrates the potential of TPLSP as a new platform for the fabrication of designed, well-controlled, 3D microstructured tissue scaffolds. PMID: 20667410 [PubMed - as supplied by publisher] | | |
| Defining Cell Identity by Comprehensive Gene Expression Profiling.
July 30, 2010 at 10:22 PM
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| | Defining Cell Identity by Comprehensive Gene Expression Profiling. Curr Med Chem. 2010 Jul 29; Authors: Toyoda M, Hamatani T, Okada H, Matsumoto K, Saito H, Umezawa A The human body is composed of 60 trillion cells, which have their origin in a fertilized egg. During development, the potential of a cell or tissue can be achieved by environmental manipulation. Then, what molecular determinants underlie or accompany the potential of the cells? To obtain a broader understanding of these problems, it is important to analyze all transcripts / genes in a wide selection of cell types. The development of microarray technologies, which allow us to undertake parallel analyses of many genes, has led to a new era in medical science. In this review, we show that the global expression data have clearly elucidated discernible major trends of the phenomenon in preimplantation development and epithelial-mesenchymal transition, and of the character of marrow stromal cells, which are attracting a great deal of attention as they represent a valuable source of cells for regenerative medicine. One of the interesting results is obtained from microarray data of marrow stromal cells: OP9 cells that have been recognized as a type of niche-constituting preadipocyte derived from marrow stroma, are found to be chondroblasts. We also describe what effect each type of expression data would bring to reproductive and regenerative medicine, as well as offering an excellent model of cell differentiation in biology. PMID: 20666720 [PubMed - as supplied by publisher] | | |
| Micro-Cavitary Hydrogel Mediating Phase Transfer Cell Culture for Cartilage Tissue Engineering.
July 30, 2010 at 10:22 PM
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| | Micro-Cavitary Hydrogel Mediating Phase Transfer Cell Culture for Cartilage Tissue Engineering. Tissue Eng Part A. 2010 Jul 28; Authors: Gong Y, Su K, Lau TT, Zhou R, Wang DA Hydrogels have been widely used as cell-laden vehicles for therapeutic transplantation in regenerative medicine. Although the advantages of biocompatibility and injectability for in situ grafting have made hydrogel a superior candidate in tissue engineering, there remain challenges in long-term efficacy of tissue development using hydrogel, especially when more sophisticated applications are demanded. The major bottleneck lies in environmental constraints for neo-tissue generation in the gel bulk such as proliferation of encapsulated cells (colonies) per se and also accommodation of their endogenously produced extracellular matrices (ECMs). In this study, we endeavor to develop an innovative tissue engineering system to overcome these drawbacks through a novel micro-cavitary hydrogel (MCG)-based scaffolding technology and a novel phase transfer cell culture (PTCC) strategy to enable phenotypically bona fide neo-tissue formation in an injectable artificial graft. For this purpose, microspherical cavities are created in cell-encapsulating hydrogel bulk via a retarded dissolution of co-encapsulated gelatin microspheres. Based on proliferation and affinity selection, the encapsulated cell colonies adjacent to the gel/cavity interface will spontaneously outgrow the hydrogel phase and sprout into cavities, enabling neo-tissue islets to fill up the voids and further expand throughout the whole system for full tissue regeneration. The design of MCG-PTCC strategy was elicited from an observation of a spontaneous dynamic outgrowth of chondrocytes from the edge of a cell-laden hydrogel construct over prolonged cultivation - a phenomenon named "edge flourish" (EF). This MCG-PTCC strategy potentially introduce a new application to hydrogels in the field of regenerative medicine through elevation of its role as a cell vehicle to a 3D-transplantable growth-guiding platform for further development of newly generated tissues that better fulfill the demanding criteria of scaffolds in therapeutic tissue regeneration. Keywords: Biomaterials; Hydrogel; Tissue Engineering; Phase Transfer Cell Culture; Regenerative Medicine. PMID: 20666616 [PubMed - as supplied by publisher] | | |
| Biodegradable Nanofibers-Reinforced Microfibrous Composite Scaffolds and the Bone Tissue Engineering.
July 30, 2010 at 10:22 PM
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| | Biodegradable Nanofibers-Reinforced Microfibrous Composite Scaffolds and the Bone Tissue Engineering. Tissue Eng Part A. 2010 Jul 28; Authors: Martins A, Pinho ED, Correlo V, Faria S, Marques A, Reis RL, Neves NM Native bone extracellular matrix (ECM) is a complex hierarchical fibrous composite structure, resulting from the assembling of collagen fibrils at several length scales, ranging from the macro to the nanoscale. The combination of nanofibers within microfibers following conventional reinforcement methodologies seems to be a feasible solution to the rational design of highly functional synthetic ECM substitutes. The present work aims at the development of bone ECM inspired structures, conjugating electrospun chitosan (Cht) nanofibers within biodegradable polymeric microfibers (poly(butylene succinate) - PBS and PBS/Cht), assembled in a fiber mesh structure. The nanofibers-reinforced composite fiber mesh scaffolds were seeded with human bone marrow mesenchymal stem cells (hBMSCs) and cultured under osteogenic differentiation conditions. These nanofibers-reinforced composite scaffolds sustained ECM deposition and mineralization, mainly in the PBS/Cht-based fiber meshes, as depicted by the increased amount of calcium phosphates produced by the osteogenic differentiated hBMSCs. The osteogenic genotype of the cultured hBMSCs was confirmed by the expression of osteoblastic genes, namely Alkaline Phosphatase, Osteopontin, Bone Sialoprotein and Osteocalcin, and the transcription factors Runx2 and Osterix, all involved in different stages of the osteogenesis. These data represent the first report on the biological functionality of nanofibers-reinforced composite scaffolds, envisaging the applicability of the developed structures for bone tissue engineering. PMID: 20666612 [PubMed - as supplied by publisher] | | |
| Use of tissue engineered nerve grafts consisting of a chitosan/ poly(lactic-co-glycolic acid)-based scaffold included with bridging 50-mm dog sciatic nerve gaps.
July 30, 2010 at 10:22 PM
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| | Use of tissue engineered nerve grafts consisting of a chitosan/ poly(lactic-co-glycolic acid)-based scaffold included with bridging 50-mm dog sciatic nerve gaps. Tissue Eng Part A. 2010 Jul 28; Authors: Ding F, Wu J, Yang Y, Hu W, Zhu Q, Tang X, Liu J, Gu X Bone marrow mesenchymal cells (MSCs) have attracted increasing research interest due to their possible use as support cells for nerve tissue engineering approaches. We developed a novel design of tissue engineered nerve grafts consisting of a chitosan/poly(lactic-co-glycolic acid) (PLGA)-based neural scaffold included with autologous MSCs. The graft was used as an alternative to nerve autografts for bridging 50-mm-long gaps in dog sciatic nerve, and the repair outcome at 6 months post nerve grafting was evaluated by a combination of electrophysiological assessment, FluoroGold retrograde tracing, and histological investigation to regenerated nerve tissue and reinnervated target muscle. The experimental results indicated that introduction of autologous MSCs to the chitosan/PLGA-based neural scaffold promoted sciatic nerve regeneration and functional recovery, demonstrating significant efficacy that was, to a certain degree, close to that by nerve autografting, a gold standard for treating large peripheral nerve gaps, and better than that by grafting with the chitosan/PLGA-based scaffold alone. PMID: 20666610 [PubMed - as supplied by publisher] | | |
| Fluid Shear Stress Promotes an Endothelial-like Phenotype during the Early Differentiation of Embryonic Stem Cells.
July 30, 2010 at 10:22 PM
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| | Fluid Shear Stress Promotes an Endothelial-like Phenotype during the Early Differentiation of Embryonic Stem Cells. Tissue Eng Part A. 2010 Jul 28; Authors: Ahsan T, Nerem RM Stem and progenitor cells are emerging as a potential source for cell-based therapies, in which large homogenous populations of differentiated cells are frequently deemed necessary for efficacy. Methods focused on biochemical cues have not yet yielded the numbers of endothelial cells thought necessary for cardiovascular applications. Interest in alternate methods has prompted the study of physical cues on stem and progenitor cell differentiation. In this study, fluid-based shear stress, at levels comparable to those experienced by endothelial cells in large vessels, was applied during the first few days of mouse embryonic stem cell differentiation. After two days of applied shear stress, there were increases in cell proliferation and in protein expression of endothelial markers (FLK1, VECAD, and PECAM). Furthermore, treatment increased the number of FLK1+ cells from 1% to 40%, which were then capable of forming vessel-like structures in vitro. Thus, shear stress may be used to direct differentiation of embryonic stem cells towards an endothelial-like phenotype, helping to address the cell sourcing issue in cardiovascular regenerative medicine and tissue engineering. PMID: 20666609 [PubMed - as supplied by publisher] | | |
| Central role for Dab2 in mesenchymal stem cardiac protein expression and functional consequences after engraftment in acute myocardial infarction.
July 30, 2010 at 10:22 PM
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| | Central role for Dab2 in mesenchymal stem cardiac protein expression and functional consequences after engraftment in acute myocardial infarction. Stem Cells Dev. 2010 Jul 28; Authors: Mayorga ME, Dong F, Sundararaman S, Huang Y, Jiang Y, Howe PH, Penn MS Adult mesenchymal stem cells (MSC) have been shown to spontaneously express cardiac proteins (CP) in vitro and to improve cardiac function after transplantation into experimentally induced acute myocardial infarction (AMI). However, if these effects are the result of MSC cardiac differentiation or a mere cooperative cellular interaction is a matter of active debate. Additionally, the molecular mechanisms involved in CP expression by adult stem cells in vitro and its possible benefit for cardiac regeneration and improved function remains unclear. Here we show that although MSC effectively engraft in AMI tissue, this engraftment leads to down-regulation of CP expression in the implanted MSC. We also found that pre-transplantation cardiac specification of MSC by exposure of the cells to TGFbeta1, led to sustained MSC CP expression without altering engraftment efficiency. This increase in CP expression was associated with greater improvement in cardiac function one and four weeks after AMI with TGFbeta1-pretreated MSC. We discovered that the TGFbeta1-enhanced cardiac potential of MSC was mediated by down-regulation of disabled-2 (Dab2) expression; suggesting an inverse correlation between Dab2 levels and CP expression/cardiac functional improvement following MSC engraftment. Our investigations further demonstrate that loss of Dab2 expression was sufficient to induce MSC CP expression and improve cardiac function following MSC engraftment after AMI. In summary, we define a novel role for the TGFbeta1 receptor adaptor protein Dab2 as a regulator of CP expression in MSC and its potential as a molecular target for the enhancement of stem cell cardiac specification for transplantation therapies. PMID: 20666606 [PubMed - as supplied by publisher] | | |
| Non-viral gene therapy strategies for keratinocytes, fibroblasts and endothelial progenitor cells for ex vivo gene transfer to skin wounds.
July 30, 2010 at 10:22 PM
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| | Non-viral gene therapy strategies for keratinocytes, fibroblasts and endothelial progenitor cells for ex vivo gene transfer to skin wounds. Tissue Eng Part C Methods. 2010 Jul 28; Authors: Dickens S, Van den Berge S, Hendrickx B, Verdonck K, Luttun A, Vranckx J In search for the most accurate non-viral gene transfer technique in epidermal and dermal supportive extracellular matrix studies, we investigated the efficiency of late generation liposomal transfection reagents and nucleofection of fibroblasts, endothelial progenitor cells and keratinocytes as essential representatives of the healing skin wound. Fibroblasts, keratinocytes and endothelial progenitor cells were grown under serum-reduced conditions and manipulated according to the optimized manufacturing protocols in vitro. Fugene(R) HD, EffecteneTM, PEI, and Lipofectin(R) were compared to Amaxa Nucleofection(R). A GFP-encoding reporter gene plasmid was incorporated and visualized by green fluorescence-activated cell sorting. Normal cell morphology was observed after transfection or nucleofection. For keratinocyte cell cultures, Fugene(R) HD resulted in highest transgene expression in human (41%) and porcine keratinocytes (42%). For endothelial progenitor cells, EffecteneTM was most successful for human derived cells (42%) whereas for porcine cells Nucleofection(R) was optimal (32%). However for fibroblasts, Nucleofection(R) resulted in highest transfection rates in human (50%) and porcine derived fibroblasts (60%). For specific epidermal cell studies Fugene(R) HD is preferable as gene transfer method, while EffecteneTM appears to be the most optimal agent for pro-angiogenic studies. When transfecting with Nucleofection(R), fibroblasts are the best gene carriers for overall ex vivo gene transfer strategies in wound healing or skin tissue engineering. PMID: 20666605 [PubMed - as supplied by publisher] | | |
| Cyclic Tensile Culture Promotes Fibroblastic Differentiation of Marrow Stromal Cells Encapsulated in Poly(Ethylene Glycol)-Based Hydrogels.
July 30, 2010 at 10:22 PM
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| | Cyclic Tensile Culture Promotes Fibroblastic Differentiation of Marrow Stromal Cells Encapsulated in Poly(Ethylene Glycol)-Based Hydrogels. Tissue Eng Part A. 2010 Jul 28; Authors: Doroski DM, Levenston ME, Temenoff JS To inform future efforts in tendon/ligament tissue engineering, our laboratory has developed a well-controlled model system with the ability to alter both external tensile loading parameters and local biochemical cues to better understand marrow stromal cell differentiation in response to both stimuli concurrently. In particular, the synthetic, poly(ethylene glycol)-based hydrogel material oligo(poly(ethylene glycol) fumarate) (OPF) has been explored as a cell carrier for this system. This biomaterial can be tailored to present covalently incorporated bioactive moieties and can be loaded in our custom cyclic tensile bioreactor for up to 28 days with no loss of material integrity. Human marrow stromal cells encapsulated in these OPF hydrogels were cultured (21 days) under cyclic tensile strain (10%, 1 Hz, 3 h of strain followed by 3 h without) or at 0% strain. No difference was observed in cell number due to mechanical stimulation or across time (n = 4), with cells remaining viable (n = 4) through 21 days. Cyclic strain significantly upregulated all tendon/ligament fibroblastic genes examined (collagen I, collagen III, and tenascin-C) by day 21 (n >/= 6), whereas genes for other pathways (osteogenic, chondrogenic, and adipogenic) did not increase. After 21 days, the presence of collagen I and tenascin-C was observed via immunostaining (n = 2). This study demonstrates the utility of this hydrogel/bioreactor system as a versatile, yet well-controlled, model environment to study marrow stromal cell differentiation toward the tendon/ligament phenotype under a variety of conditions. PMID: 20666585 [PubMed - as supplied by publisher] | | |
| Organ reengineering through development of a transplantable recellularized liver graft using decellularized liver matrix.
July 30, 2010 at 10:22 PM
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| | Organ reengineering through development of a transplantable recellularized liver graft using decellularized liver matrix. Nat Med. 2010 Jul;16(7):814-20 Authors: Uygun BE, Soto-Gutierrez A, Yagi H, Izamis ML, Guzzardi MA, Shulman C, Milwid J, Kobayashi N, Tilles A, Berthiaume F, Hertl M, Nahmias Y, Yarmush ML, Uygun K Orthotopic liver transplantation is the only available treatment for severe liver failure, but it is currently limited by organ shortage. One technical challenge that has thus far limited the development of a tissue-engineered liver graft is oxygen and nutrient transport. Here we demonstrate a novel approach to generate transplantable liver grafts using decellularized liver matrix. The decellularization process preserves the structural and functional characteristics of the native microvascular network, allowing efficient recellularization of the liver matrix with adult hepatocytes and subsequent perfusion for in vitro culture. The recellularized graft supports liver-specific function including albumin secretion, urea synthesis and cytochrome P450 expression at comparable levels to normal liver in vitro. The recellularized liver grafts can be transplanted into rats, supporting hepatocyte survival and function with minimal ischemic damage. These results provide a proof of principle for the generation of a transplantable liver graft as a potential treatment for liver disease. PMID: 20543851 [PubMed - indexed for MEDLINE] | | |
| Macrophages as mediators of tumor immunosurveillance.
July 30, 2010 at 10:22 PM
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| | Macrophages as mediators of tumor immunosurveillance. Trends Immunol. 2010 Jun;31(6):212-9 Authors: Jaiswal S, Chao MP, Majeti R, Weissman IL Tumor immunosurveillance is a well-established mechanism for regulation of tumor growth. In this regard, most studies have focused on the role of T- and NK-cells as the critical immune effector cells. However, macrophages play a major role in the recognition and clearance of foreign, aged, and damaged cells. Macrophage phagocytosis is negatively regulated via the receptor SIRPalpha upon binding to CD47, a ubiquitously expressed protein. We recently showed that CD47 is up-regulated in myeloid leukemia and migrating hematopoietic progenitors, and that the level of protein expression correlates with the ability to evade phagocytosis. These results implicate macrophages in the immunosurveillance of hematopoietic cells and leukemias. The ability of macrophages to phagocytose tumor cells might be exploited therapeutically by blocking the CD47-SIRPalpha interaction. PMID: 20452821 [PubMed - indexed for MEDLINE] | | |
| Application of acellular dermal matrix for intestinal elongation in animal models.
July 30, 2010 at 10:22 PM
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| | Application of acellular dermal matrix for intestinal elongation in animal models. World J Gastroenterol. 2010 Apr 28;16(16):2023-7 Authors: Xu HM, Wang ZJ, Han JG, Ma HC, Zhao B, Zhao BC AIM: To investigate the efficacy of acellular dermal matrix (ADM) for intestinal elongation in animal models. METHODS: Japanese white big-ear rabbits (n = 9) and Wuzhishan miniature pigs (n = 5) were used in the study. Home-made and commercial ADM materials were used as grafts, respectively. A 3-cm long graft was interposed in continuity with the small bowel and a side-to-side anastomosis, distal to the graft about 3-4 cm, was performed. The animals were sacrificed at 2 wk, 4 wk, 8 wk and 3 mo after surgery and the histological changes were evaluated under light microscope and electron microscope. RESULTS: The animals survived after the operation with no evidence of peritonitis and sepsis. Severe adhesions were found between the graft and surrounding intestine. The grafts were completely absorbed within postoperative two or three months except one. Histological observation showed inflammation in the grafts with fibrinoid necroses, infiltration of a large amount of neutrophils and leukomonocytes, and the degree varied in different stages. The neointestine with well-formed structures was not observed in the study. CONCLUSION: It is not suitable to use acellular dermal matrix alone as a scaffold for the intestinal elongation in animal models. PMID: 20419841 [PubMed - indexed for MEDLINE] | | |
| Autologous chondrocyte implantation in cartilage lesions of the knee: long-term evaluation with magnetic resonance imaging and delayed gadolinium-enhanced magnetic resonance imaging technique.
July 30, 2010 at 10:22 PM
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| | Autologous chondrocyte implantation in cartilage lesions of the knee: long-term evaluation with magnetic resonance imaging and delayed gadolinium-enhanced magnetic resonance imaging technique. Am J Sports Med. 2010 May;38(5):943-9 Authors: Vasiliadis HS, Danielson B, Ljungberg M, McKeon B, Lindahl A, Peterson L BACKGROUND: Various treatment options are available for articular cartilage lesions, but controversy exists regarding the quality of the repair tissue and the durability of the results posttreatment. Noninvasive techniques are needed for the assessment of the repair tissue. HYPOTHESIS: Magnetic resonance imaging (MRI) with delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) can give valuable information regarding the quality and quantity of the repaired cartilage lesion. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Thirty-six knees in 31 patients were assessed 9 to 18 years after treatment with autologous chondrocyte implantation (ACI). All patients had isolated lesions. The knees were clinically evaluated with the Knee injury and Osteoarthritis Outcome Score and the dGEMRIC technique. The T1 value was measured for 2 regions of interest (ROIs), 1 in the repair tissue area (ROI 1) and 1 in the surrounding cartilage (ROI 2), giving information of the content of proteoglycans. RESULTS: The average T1 value in ROI 1 was 467.5 milliseconds and in ROI 2, 495.3 milliseconds, which yielded no significant difference, thus suggesting comparable levels of proteoglycans in the repair tissue and surrounding cartilage. Intralesional osteophytes were in 64% of the lesions, mainly in younger patients with osteochondritis dissecans lesions or a history of subchondral bone surgeries. Medium or large bone marrow edema was found in 14% of the knees and subchondral cysts, in 39%. There was no correlation between the KOOS and any MRI findings. CONCLUSION: Magnetic resonance imaging with dGEMRIC gives valuable information for the macroscopic appearance and micro-molecular quality of the repair tissue after ACI. Nine to 18 years posttreatment, the quality of the repair tissue is similar to the surrounding normal cartilage, although intralesional osteophytes, subchondral cysts, and bone marrow edema were common. The defect area is restored in most patients. However, there was no correlation between the dGEMRIC values and the KOOS outcomes. PMID: 20185841 [PubMed - indexed for MEDLINE] | | |
| Erythropoietin receptor response circuits.
July 30, 2010 at 10:22 PM
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| | Erythropoietin receptor response circuits. Curr Opin Hematol. 2010 May;17(3):169-76 Authors: Wojchowski DM, Sathyanarayana P, Dev A PURPOSE OF REVIEW: In 1985-1989, erythropoietin (EPO), its receptor (EPOR), and janus kinase 2 were cloned; established to be essential for definitive erythropoiesis; and initially intensely studied. Recently, new impetus, tools, and model systems have emerged to re-examine EPO/EPOR actions, and are addressed in this review. Impetus includes indications that EPO affects significantly more than standard erythroblast survival pathways, the development of novel erythropoiesis-stimulating agents, increasing evidence for EPO/EPOR cytoprotection of ischemically injured tissues, and potential EPO-mediated worsening of tumorigenesis. RECENT FINDINGS: New findings are reviewed in four functional contexts: (pro)erythroblast survival mechanisms, new candidate EPO/EPOR effects on erythroid cell development and new EPOR responses, EPOR downmodulation and trafficking, and novel erythropoiesis-stimulating agents. SUMMARY: As Current Opinion, this monograph seeks to summarize, and provoke, new EPO/EPOR action concepts. Specific problems addressed include: beyond (and before) BCL-XL, what key survival factors are deployed in early-stage proerythroblasts? Are distinct EPO/EPOR signals transduced in stage-selective fashions? Is erythroblast proliferation also modulated by EPO/EPOR signals? What functions are subserved by new noncanonical EPO/EPOR response factors (e.g. podocalyxin like-1, tribbles 3, reactive oxygen species, and nuclear factor kappa B)? What key regulators mediate EPOR inhibition and trafficking? And for emerging erythropoiesis-stimulating agents, to what extent do activities parallel EPOs (or differ in advantageous, potentially complicating ways, or both)? PMID: 20173635 [PubMed - indexed for MEDLINE] | | |
| A computer model of engineered cardiac monolayers.
July 30, 2010 at 5:22 PM
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| | A computer model of engineered cardiac monolayers. Biophys J. 2010 May 19;98(9):1762-71 Authors: Kim JM, Bursac N, Henriquez CS Engineered monolayers created using microabrasion and micropatterning methods have provided a simplified in vitro system to study the effects of anisotropy and fiber direction on electrical propagation. Interpreting the behavior in these culture systems has often been performed using classical computer models with continuous properties. However, such models do not account for the effects of random cell shapes, cell orientations, and cleft spaces inherent in these monolayers on the resulting wavefront conduction. This work presents a novel methodology for modeling a monolayer of cardiac tissue in which the factors governing cell shape, cell-to-cell coupling, and degree of cleft space are not constant but rather are treated as spatially random with assigned distributions. This modeling approach makes it possible to simulate wavefront propagation in a manner analogous to performing experiments on engineered monolayer tissues. Simulated results are compared to previously published measured data from monolayers used to investigate the role of cellular architecture on conduction velocities and anisotropy ratios. We also present an estimate for obtaining the electrical properties from these networks and demonstrate how variations in the discrete cellular architecture affect the macroscopic conductivities. The simulations support the common assumption that under normal ranges of coupling strength, tissues with relatively uniform distributions of cell shapes and connectivity can be represented using continuous models with conductivities derived from random discrete cellular architecture using either global or local estimates. The results also reveal that in the presence of abrupt changes in cell orientation, local estimates of tissue properties predict smoother changes in conductivity that may not adequately predict the discrete nature of propagation at the transition sites. PMID: 20441739 [PubMed - indexed for MEDLINE] | | | | 
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