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| Site-specific tissue inhibitor of metalloproteinase-1 governs the matrix metalloproteinases-dependent degradation of crosslinked collagen scaffolds and is correlated with interleukin-10.
July 28, 2010 at 5:23 PM
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| | Site-specific tissue inhibitor of metalloproteinase-1 governs the matrix metalloproteinases-dependent degradation of crosslinked collagen scaffolds and is correlated with interleukin-10. J Tissue Eng Regen Med. 2010 Jul 26; Authors: Ye Q, van Amerongen MJ, Sandham JA, Bank RA, van Luyn MJ, Harmsen MC We have previously shown that the foreign body reaction (FBR) against crosslinked collagen type I (Col-I) differs between subcutaneous and epicardial implantation sites; Col-I was quickly degraded epicardially, whereas degradation was attenuated subcutaneously. The current study set out to dissect the nature and regulation of the MMP-based degradation of implanted Col-I in mice during the FBR. Immunohistochemistry showed that MMP-2, MMP-8 and MMP-13 were present in subcutaneous and epicardial implants, whereas only MMP-9 was also present epicardially. Western blotting showed that MMP-8 and MMP-9 were mainly present in their inactive proform. In contrast, collagenase MMP-13 and gelatinase MMP-2 were the predominant active MMPs at both sites. Interestingly, the major MMP inhibitor TIMP-1 was solely observed in subcutaneous implants, which is why MMP-13 and MMP-2 are not able to degrade the collagen scaffold at the subcutaneous implantation site. Interleukin 10 (IL-10), a potent inducer of TIMP-1 expression, was also mainly detected subcutaneously; giant cells were the main source. Therefore, we surmise that IL-10, through regulation of the balance between MMPs and TIMP-1, suppresses the FBR against implanted biomaterials. Together, our findings would provide cues and clues to improve future therapies in regenerative medicine that are based on the tuned regulation of the degradation of biomaterial scaffolds. Copyright (c) 2010 John Wiley & Sons, Ltd. PMID: 20661871 [PubMed - as supplied by publisher] | | |
| Immune-related zinc finger gene ZFAT is an essential transcriptional regulator for hematopoietic differentiation in blood islands.
July 28, 2010 at 5:23 PM
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| | Immune-related zinc finger gene ZFAT is an essential transcriptional regulator for hematopoietic differentiation in blood islands. Proc Natl Acad Sci U S A. 2010 Jul 26; Authors: Tsunoda T, Takashima Y, Tanaka Y, Fujimoto T, Doi K, Hirose Y, Koyanagi M, Yoshida Y, Okamura T, Kuroki M, Sasazuki T, Shirasawa S TAL1 plays pivotal roles in vascular and hematopoietic developments through the complex with LMO2 and GATA1. Hemangioblasts, which have a differentiation potential for both endothelial and hematopoietic lineages, arise in the primitive streak and migrate into the yolk sac to form blood islands, where primitive hematopoiesis occurs. ZFAT (a zinc-finger gene in autoimmune thyroid disease susceptibility region / an immune-related transcriptional regulator containing 18 C(2)H(2)-type zinc-finger domains and one AT-hook) was originally identified as an immune-related transcriptional regulator containing 18 C(2)H(2)-type zinc-finger domains and one AT-hook, and is highly conserved among species. ZFAT is thought to be a critical transcription factor involved in immune-regulation and apoptosis; however, developmental roles for ZFAT remain unknown. Here we show that Zfat-deficient (Zfat (-/-)) mice are embryonic-lethal, with impaired differentiation of hematopoietic progenitor cells in blood islands, where ZFAT is exactly expressed. Expression levels of Tal1, Lmo2, and Gata1 in Zfat (-/-) yolk sacs are much reduced compared with those of wild-type mice, and ChIP-PCR analysis revealed that ZFAT binds promoter regions for these genes in vivo. Furthermore, profound reduction in TAL1, LMO2, and GATA1 protein expressions are observed in Zfat (-/-) blood islands. Taken together, these results suggest that ZFAT is indispensable for mouse embryonic development and functions as a critical transcription factor for primitive hematopoiesis through direct-regulation of Tal1, Lmo2, and Gata1. Elucidation of ZFAT functions in hematopoiesis might lead to a better understanding of transcriptional networks in differentiation and cellular programs of hematopoietic lineage and provide useful information for applied medicine in stem cell therapy. PMID: 20660741 [PubMed - as supplied by publisher] | | |
| Case Control Series of Intrathecal Autologous Bone Marrow Mesenchymal Stem Cell Therapy for Chronic Spinal Cord Injury.
July 28, 2010 at 5:23 PM
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| | Case Control Series of Intrathecal Autologous Bone Marrow Mesenchymal Stem Cell Therapy for Chronic Spinal Cord Injury. Neurorehabil Neural Repair. 2010 Jul 26; Authors: Kishk NA, Gabr H, Hamdy S, Afifi L, Abokresha N, Mahmoud H, Wafaie A, Bilal D BACKGROUND: Autologous bone marrow mesenchymal cells that include stem cells (MSCs) are a clinically attractive cellular therapy option to try to treat severe spinal cord injury (SCI). OBJECTIVE: To study the possible value of MSCs injected intrathecally to enhance rehabilitation. METHODS: This case control, convenience sample included 64 patients, at a mean of 3.6 years after SCI. Forty-four subjects received monthly intrathecal autologous MSCs for 6 months and 20 subjects, who would not agree to the procedures, served as controls. All subjects received rehabilitation therapies 3 times weekly. Subjects were evaluated at entry and at 12 months after completing the 6-months intervention. By the ASIA Impairment Scale, ASIA grading of completeness of injury, Ashworth Spasticity Scale, Functional Ambulation Classification, and bladder and bowel control questionnaire. RESULTS: No differences were found in baseline measures and descriptors between the MSC group and control group. Although a higher percentage of the MSC group increased motor scores by 1-2 points and changed from ASIA A to B, no significant between-group improvements were found in clinical measures. Adverse effects of cells included spasticity and, in 24 out of the 43 patients developed neuropathic pain. One subject with a history of post-infectious myelitis developed encephalomyelitis after her third injection. CONCLUSION: Autologus MSCs may have side effects and may be contraindicated in patients with a history of myelitis. Their utility in treating chronic traumatic SCI needs further study in pre-clinical models and in randomized controlled trials before they should be offered to patients. PMID: 20660620 [PubMed - as supplied by publisher] | | |
| Quiescence and Activation of Stem and Precursor Cell Populations in the Subependymal Zone of the Mammalian Brain Are Associated with Distinct Cellular and Extracellular Matrix Signals.
July 28, 2010 at 5:23 PM
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| | Quiescence and Activation of Stem and Precursor Cell Populations in the Subependymal Zone of the Mammalian Brain Are Associated with Distinct Cellular and Extracellular Matrix Signals. J Neurosci. 2010 Jul 21;30(29):9771-9781 Authors: Kazanis I, Lathia JD, Vadakkan TJ, Raborn E, Wan R, Mughal MR, Eckley DM, Sasaki T, Patton B, Mattson MP, Hirschi KK, Dickinson ME, Ffrench-Constant C The subependymal zone (SEZ) of the lateral ventricles is one of the areas of the adult brain where new neurons are continuously generated from neural stem cells (NSCs), via rapidly dividing precursors. This neurogenic niche is a complex cellular and extracellular microenvironment, highly vascularized compared to non-neurogenic periventricular areas, within which NSCs and precursors exhibit distinct behavior. Here, we investigate the possible mechanisms by which extracellular matrix molecules and their receptors might regulate this differential behavior. We show that NSCs and precursors proceed through mitosis in the same domains within the SEZ of adult male mice-albeit with NSCs nearer ependymal cells-and that distance from the ventricle is a stronger limiting factor for neurogenic activity than distance from blood vessels. Furthermore, we show that NSCs and precursors are embedded in a laminin-rich extracellular matrix, to which they can both contribute. Importantly, they express differential levels of extracellular matrix receptors, with NSCs expressing low levels of alpha6beta1 integrin, syndecan-1, and lutheran, and in vivo blocking of beta1 integrin selectively induced the proliferation and ectopic migration of precursors. Finally, when NSCs are activated to reconstitute the niche after depletion of precursors, expression of laminin receptors is upregulated. These results indicate that the distinct behavior of adult NSCs and precursors is not necessarily regulated via exposure to differential extracellular signals, but rather via intrinsic regulation of their interaction with their microenvironment. PMID: 20660259 [PubMed - as supplied by publisher] | | |
| Expression of Huntington's disease protein results in apoptotic neurons in the brains of cloned transgenic pigs.
July 28, 2010 at 5:23 PM
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| | Expression of Huntington's disease protein results in apoptotic neurons in the brains of cloned transgenic pigs. Hum Mol Genet. 2010 Jul 21; Authors: Yang D, Wang CE, Zhao B, Li W, Ouyang Z, Liu Z, Yang H, Fan P, O'Neill A, Gu W, Yi H, Li S, Lai L, Li XJ Neurodegeneration is a hallmark of many neurological diseases, including Alzheimer's, Parkinson's, and the polyglutamine diseases, which are all caused by misfolded proteins that accumulate in neuronal cells of the brain. Although apoptosis is believed to contribute to neurodegeneration in these cases, genetic mouse models of these diseases often fail to replicate apoptosis and overt neurodegeneration in the brain. Using nuclear transfer, we generated transgenic Huntington's disease (HD) pigs that express N-terminal (208 amino acids) mutant huntingtin with an expanded polyglutamine tract (105Q). Postnatal death, dyskinesia, and chorea-like movement were observed in some transgenic pigs expressing mutant huntingtin. Importantly, the transgenic HD pigs, unlike mice expressing the same transgene, displayed typical apoptotic neurons with DNA fragmentation in their brains. Also, expression of mutant huntingtin resulted in more neurons with activated caspase-3 in transgenic pig brains than in transgenic mouse brains. Our findings suggest that species differences determine neuropathology and underscore the importance of large mammalian animals for modeling neurological disorders. PMID: 20660116 [PubMed - as supplied by publisher] | | |
| Embryoid bodies formation and differentiation from mouse embryonic stem cells in collagen/Matrigel scaffolds.
July 28, 2010 at 5:23 PM
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| | Embryoid bodies formation and differentiation from mouse embryonic stem cells in collagen/Matrigel scaffolds. J Genet Genomics. 2010 Jul;37(7):451-460 Authors: Zhou J, Zhang Y, Lin Q, Liu Z, Wang H, Duan C, Wang Y, Hao T, Wu K, Wang C Embryonic stem (ES) cells have the potential to develop into any type of tissue and are considered as a promising source of seeding cells for tissue engineering and transplantation therapy. The main catalyst for ES cells differentiation is the growth into embryoid bodies (EBs), which are utilized widely as the trigger of in vitro differentiation. In this study, a novel method for generating EBs from mouse ES cells through culture in collagen/Matrigel scaffolds was successfully established. When single ES cells were seeded in three dimensional collagen/Matrigel scaffolds, they grew into aggregates gradually and formed simple EBs with circular structures. After 7 days' culture, they formed into cystic EBs that would eventually differentiate into the three embryonic germ layers. Evaluation of the EBs in terms of morphology and potential to differentiate indicated that they were typical in structure and could generate various cell types; they were also able to form into tissue-like structures. Moreover, with introduction of ascorbic acid, ES cells differentiated into cardiomyocytes efficiently and started contracting synchronously at day 19. The results demonstrated that collagen/Matrigel scaffolds supported EBs formation and their subsequent differentiation in a single three dimensional environment. PMID: 20659709 [PubMed - as supplied by publisher] | | |
| Role of Lef1 in sustaining self-renewal in mouse embryonic stem cells.
July 28, 2010 at 5:23 PM
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| | Role of Lef1 in sustaining self-renewal in mouse embryonic stem cells. J Genet Genomics. 2010 Jul;37(7):441-449 Authors: Huang C, Qin D Embryonic stem cells (ESCs) can self-renew indefinitely while maintaining the ability to generate all three germ-layer derivatives. Despite the importance of ESCs in developmental biology and their potential impact on regenerative medicine, the molecular mechanisms controlling ESC behavior are incompletely understood. Previously, activation of the canonical Wnt signaling pathway has been shown to contribute to mouse ESC self-renewal. Here we report that ectopic expression of Lef1, a component of the Wnt signaling pathway, has a positive effect on the self-renewal of mouse ESCs. Lef1 up-regulates Oct4 promoter activity and physically interacts with Nanog, two key components of the ESC pluripotency machinery. Moreover, siRNA for Lef1 induced mouse ESC differentiation. Our results thus suggest that in response to Wnt signaling Lef1 binds to stabilized beta-catenin and helps maintain the undifferentiated status of ESCs through modulation of Oct4 and Nanog. PMID: 20659708 [PubMed - as supplied by publisher] | | |
| Accessing Protein Methyltransferase and Demethylase Enzymology Using Microfluidic Capillary Electrophoresis.
July 28, 2010 at 5:23 PM
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| | Accessing Protein Methyltransferase and Demethylase Enzymology Using Microfluidic Capillary Electrophoresis. Chem Biol. 2010 Jul 30;17(7):695-704 Authors: Wigle TJ, Provencher LM, Norris JL, Jin J, Brown PJ, Frye SV, Janzen WP The discovery of small molecules targeting the >80 enzymes that add (methyltransferases) or remove (demethylases) methyl marks from lysine and arginine residues, most notably present in histone tails, may yield unprecedented chemotherapeutic agents and facilitate regenerative medicine. To better enable chemical exploration of these proteins, we have developed a highly quantitative microfluidic capillary electrophoresis assay to enable full mechanistic studies of these enzymes and the kinetics of their inhibition. This technology separates small biomolecules, i.e., peptides, based on their charge-to-mass ratio. Methylation, however, does not alter the charge of peptide substrates. To overcome this limitation, we have employed a methylation-sensitive endoproteinase strategy to separate methylated from unmethylated peptides. The assay was validated on a lysine methyltransferase (G9a) and a lysine demethylase (LSD1) and was employed to investigate the inhibition of G9a by small molecules. PMID: 20659682 [PubMed - as supplied by publisher] | | |
| Liquid-liquid two phase systems for the production of porous hydrogels and hydrogel microspheres for biomedical applications: A tutorial review.
July 28, 2010 at 5:23 PM
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| | Liquid-liquid two phase systems for the production of porous hydrogels and hydrogel microspheres for biomedical applications: A tutorial review. Acta Biomater. 2010 Jul 23; Authors: Elbert DL Macroporous hydrogels may have direct applications in regenerative medicine as scaffolds to support tissue formation. Hydrogel microspheres may be used as drug delivery vehicles or as building blocks to assemble modular scaffolds. A variety of techniques exist to produce macroporous hydrogels and hydrogel microspheres. A subset of these relies on liquid-liquid two phase systems. Within this subset, vastly different types of polymerization processes are found. In this review, the history, terminology and classification of liquid-liquid two phase polymerization and crosslinking are described. Instructive examples of hydrogel microsphere and macroporous scaffold formation by precipitation/dispersion, emulsion and suspension polymerizations are used to illustrate the nature of these processes. The role of the kinetics of phase separation in determining the morphology of scaffolds and microspheres is also delineated. Brief descriptions of miniemulsion, microemulsion polymerization and ionotropic gelation are also included. PMID: 20659596 [PubMed - as supplied by publisher] | | |
| High-content screening of small compounds on human embryonic stem cells.
July 28, 2010 at 5:23 PM
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| | High-content screening of small compounds on human embryonic stem cells. Biochem Soc Trans. 2010 Aug 1;38(4):1046-50 Authors: Barbaric I, Gokhale PJ, Andrews PW Human ES (embryonic stem) cells and iPS (induced pluripotent stem) cells have been heralded as a source of differentiated cells that could be used in the treatment of degenerative diseases, such as Parkinson's disease or diabetes. Despite the great potential for their use in regenerative therapy, the challenge remains to understand the basic biology of these remarkable cells, in order to differentiate them into any functional cell type. Given the scale of the task, high-throughput screening of agents and culture conditions offers one way to accelerate these studies. The screening of small-compound libraries is particularly amenable to such high-throughput methods. Coupled with high-content screening technology that enables simultaneous assessment of multiple cellular features in an automated and quantitative way, this approach is proving powerful in identifying both small molecules as tools for manipulating stem cell fates and novel mechanisms of differentiation not previously associated with stem cell biology. Such screens performed on human ES cells also demonstrate the usefulness of human ES/iPS cells as cellular models for pharmacological testing of drug efficacy and toxicity, possibly a more imminent use of these cells than in regenerative medicine. PMID: 20659001 [PubMed - in process] | | |
| Evaluating the utility of cardiomyocytes from human pluripotent stem cells for drug screening.
July 28, 2010 at 5:23 PM
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| | Evaluating the utility of cardiomyocytes from human pluripotent stem cells for drug screening. Biochem Soc Trans. 2010 Aug 1;38(4):1037-45 Authors: Dick E, Rajamohan D, Ronksley J, Denning C Functional cardiomyocytes can now be derived routinely from hPSCs (human pluripotent stem cells), which collectively include embryonic and induced pluripotent stem cells. This technology presents new opportunities to develop pharmacologically relevant in vitro screens to detect cardiotoxicity, with a view to improving patient safety while reducing the economic burden to industry arising from high drug attrition rates. In the present article, we consider the need for human cardiomyocytes in drug-screening campaigns and review the strategies used to differentiate hPSCs towards the cardiac lineage. During early stages of differentiation, hPSC-cardiomyocytes display gene expression profiles, ultra-structures, ion channel functionality and pharmacological responses reminiscent of an embryonic phenotype, but maturation during extended time in culture has been demonstrated convincingly. Notably, hPSC-cardiomyocytes have been shown to respond in a highly predictable manner to over 40 compounds that have a known pharmacological effect on the human heart. This suggests that further development and validation of the hPSC-cardiomyocyte model as a tool for assessing cardiotoxicity is warranted. PMID: 20659000 [PubMed - in process] | | |
| Role of stem-cell-derived hepatic endoderm in human drug discovery.
July 28, 2010 at 5:23 PM
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| | Role of stem-cell-derived hepatic endoderm in human drug discovery. Biochem Soc Trans. 2010 Aug 1;38(4):1033-6 Authors: Medine CN, Greenhough S, Hay DC Accurate prediction of human drug toxicity is a vital part of the drug discovery process. However, the safety evaluation process is hindered by the availability and quality of primary human liver models with which to study drug toxicity. In an attempt to overcome this limitation, research has focused on deriving human hepatocytes from a number of sources, including progenitors from fetal and adult liver, human cell lines derived from liver tumours, immortalized human hepatocytes and pluripotent stem cells. The major hurdles in developing scalable and high-fidelity human hepatocytes from hepatic cell lines and fetal and adult progenitors have been limited organ availability, homogeneous cell purification, short-term cell culture, and the rapid loss of hepatocyte phenotype and function in culture. Therefore it has been necessary to find alternative sources of human hepatocytes which circumvent these issues. The research in our group has focused on generating human hepatic endoderm from the scalable pluripotent stem cell populations, human embryonic stem cells and induced pluripotent stem cells. We have developed efficient and scalable models of human hepatocyte differentiation from these cell populations. Moreover, stem-cell-derived hepatic endoderm displays many of the functional attributes of primary human hepatocytes. Our research is now focused on developing defined culture systems and improving cell culture microenvironments in order to improve our understanding of the mechanisms regulating human liver development. This will in turn facilitate the generation of broad-range functioning hepatic endoderm in vitro. By taking these approaches, we believe that it will be possible to improve the predictive nature of our in vitro models, revolutionizing the manner in which industry measures human drug toxicity and having an impact on drug attrition. PMID: 20658999 [PubMed - in process] | | |
| Periostin advances atherosclerotic and rheumatic cardiac valve degeneration by inducing angiogenesis and MMP production in humans and rodents.
July 28, 2010 at 5:23 PM
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| | Periostin advances atherosclerotic and rheumatic cardiac valve degeneration by inducing angiogenesis and MMP production in humans and rodents. J Clin Invest. 2010 Jul 1;120(7):2292-306 Authors: Hakuno D, Kimura N, Yoshioka M, Mukai M, Kimura T, Okada Y, Yozu R, Shukunami C, Hiraki Y, Kudo A, Ogawa S, Fukuda K Valvular heart disease (VHD) is the term given to any disease process involving one or more of the heart valves. The condition can be congenital or acquired, for example as a result of atherosclerosis or rheumatic fever. Despite its clinical importance, the molecular mechanisms underlying VHD remain unknown. We investigated the pathophysiologic role and molecular mechanism of periostin, a protein that plays critical roles in cardiac valve development, in degenerative VHD. Unexpectedly, we found that periostin levels were drastically increased in infiltrated inflammatory cells and myofibroblasts in areas of angiogenesis in human atherosclerotic and rheumatic VHD, whereas periostin was localized to the subendothelial layer in normal valves. The expression patterns of periostin and chondromodulin I, an angioinhibitory factor that maintains cardiac valvular function, were mutually exclusive. In WT mice, a high-fat diet markedly increased aortic valve thickening, annular fibrosis, and MMP-2 and MMP-13 expression levels, concomitant with increased periostin expression; these changes were attenuated in periostin-knockout mice. In vitro and ex vivo studies revealed that periostin promoted tube formation and mobilization of ECs. Furthermore, periostin prominently increased MMP secretion from cultured valvular interstitial cells, ECs, and macrophages in a cell type-specific manner. These findings indicate that, in contrast to chondromodulin I, periostin plays an essential role in the progression of cardiac valve complex degeneration by inducing angiogenesis and MMP production. PMID: 20551517 [PubMed - indexed for MEDLINE] | | |
| IV.1. Scaffolds & surfaces.
July 28, 2010 at 5:23 PM
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| | IV.1. Scaffolds & surfaces. Stud Health Technol Inform. 2010;152:187-201 Authors: Partap S, Lyons F, O'Brien FJ PMID: 20407195 [PubMed - indexed for MEDLINE] | | |
| Defined high protein content surfaces for stem cell culture.
July 28, 2010 at 5:23 PM
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| | Defined high protein content surfaces for stem cell culture. Biomaterials. 2010 Jul;31(19):5137-42 Authors: Doran MR, Frith JE, Prowse AB, Fitzpatrick J, Wolvetang EJ, Munro TP, Gray PP, Cooper-White JJ Unlocking the clinical potential of stem cell based therapies requires firstly elucidation of the biological mechanisms which direct stem cell fate decisions and thereafter, technical advances which allow these processes to be driven in a fully defined culture environment. Strategies for the generation of defined surfaces for human embryonic stem cell (hESC) and mesenchymal stem cell (MSC) culture remain in their infancy. In this paper we outline a simple, effective and efficient method for presenting proteins or peptides on an otherwise non-fouling Layer-by-Layer (LbL) self-assembled surface of hyaluronic acid (HA) and chitosan (CHI). We are able to generate a surface that has both good temporal stability and the ability to direct biological outcomes based on its defined surface composition. Surface functionalization is achieved through suspending the selected extracellular matrix (ECM) protein domain or extracted full-length protein in buffer containing a cross-linking agent (N-hydroxysulfosuccinimide/N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride) over the LbL HA-CHI surface and then allowing the solvent to evaporate overnight. This simple, but important step results in remarkable protein deposition efficiencies often exceeding 50%, whereas traditional cross-linking methods result in such poor deposition of non-collagenous proteins that a.) quantification of bound amounts of protein is outside the resolution of commonly utilized protein assays, and b.) these surfaces are both unable to support cell attachment and growth. The utility of the protein-modified HA-CHI surfaces is demonstrated through the identification of specific hESC attachment efficiencies and through directing MSC osteogenic outcomes on these fully defined surfaces. This simple and scalable method is shown to enable the development of defined stem cell culture conditions, as well as the elucidation of the fundamental biological processes necessary for the realization of stem cell based therapies. PMID: 20378164 [PubMed - indexed for MEDLINE] | | |
| Oxygen mass transfer in a human tissue-engineered trachea.
July 28, 2010 at 5:23 PM
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| | Oxygen mass transfer in a human tissue-engineered trachea. Biomaterials. 2010 Jul;31(19):5131-6 Authors: Curcio E, Macchiarini P, De Bartolo L On June 2008, the first human tissue-engineered trachea replacement was performed using decellularized (de-antigenised) cadaveric donor trachea, seeded with recipient epithelial cells on the internal surface of the graft and mesenchymal stem-cell-derived chondrocytes on the external. During the follow-up, cytological analysis at 4 postoperative days showed a migration of the stem-cells derived chondrocytes from the outer to the inner surface of the first 2 cm of the graft length. With the aim to rationalize these clinical findings, and under the hypothesis that cellular migration is driven by the oxygen gradients developing from the external part of the construct (exposed to O(2) deficiency) towards the better oxygenated epithelial region, an accurate computational model of oxygen transport in the trachea engineered construct was developed and solved using finite element method (FEM). Results confirm that critical limitation to oxygen transport prevalently occurs from proximal to middle section, within the first 2.8 cm of longitudinal length, in good agreement with experimental observation. In the proximal section, recognized as the most critical part of the engineered construct, the severe O(2) mass transfer limitation causes a drastic reduction of the diffusive flux within a distance of 650 microm. At cell density of 1 x 10(7)cells/cm(3), the 30% c.a of the total section area is under oxygen deficiency (O(2) partial pressure below the critical threshold of 38 mmHg). Along the whole tracheal construct, the Thiele modulus ranges within 2.3 and 3.7 in the external chondrocyte compartment, confirming thus the importance of the mass transfer limitation to oxygen diffusion rate. In general, the efficiency of the O(2) transport reduces considerably in the region close to proximal section. PMID: 20378162 [PubMed - indexed for MEDLINE] | | |
| The effects of co-culture with fibroblasts and angiogenic growth factors on microvascular maturation and multi-cellular lumen formation in HUVEC-oriented polymer fibre constructs.
July 28, 2010 at 5:23 PM
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| | The effects of co-culture with fibroblasts and angiogenic growth factors on microvascular maturation and multi-cellular lumen formation in HUVEC-oriented polymer fibre constructs. Biomaterials. 2010 Jul;31(19):5091-9 Authors: Sukmana I, Vermette P In the present study, polymer monofilaments were embedded in fibrin seeded with human umbilical vein endothelial cells (HUVEC) to guide HUVEC attachment and migration in order to form oriented vessel-like structures between adjacent monofilaments. Histology and fluorescent fibrin experiments confirmed that microvessel-like structures, which were developing between polymer monofilaments embedded in fibrin, contained a lumen. The effect of human fibroblasts and growth factors (VEGF and bFGF) over the microvessel formation process was tested. The effects of VEGF and bFGF were dose-dependent. The effect of VEGF was optimum at the lower concentration tested (2 ng/mL), while that of bFGF was optimum at the higher tested concentration (20 ng/mL). Furthermore, the use of fibroblasts significantly improved the maturation of the microvessels compared to control and to samples cultured with VEGF and bFGF. PMID: 20347133 [PubMed - indexed for MEDLINE] | | |
| Aortic valve repair for congenital and balloon-induced aortic regurgitation.
July 28, 2010 at 5:23 PM
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| | Aortic valve repair for congenital and balloon-induced aortic regurgitation. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2010;13(1):60-5 Authors: Jonas RA Current techniques for aortic valve replacement in the child carry multiple disadvantages. Longer-term follow-up of the Ross procedure has documented disappointing late results for an increasing proportion of patients. Many challenges continue to face the development of a tissue-engineered valve with growth potential. In this setting, aortic valve repair is a useful temporizing procedure that allows a child to have an excellent quality of life, free from the need for anticoagulation and the risk of thromboembolism. Repair techniques are primarily based on the use of autologous pericardium to extend leaflets and support prolapsing leaflets. These methods appear to be particularly applicable in the setting of balloon-induced aortic valve regurgitation. An increasing number of centers are reporting satisfactory midterm results with aortic valve repair. PMID: 20307863 [PubMed - indexed for MEDLINE] | | |
| Potential of an injectable chitosan/starch/beta-glycerol phosphate hydrogel for sustaining normal chondrocyte function.
July 28, 2010 at 5:23 PM
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| | Potential of an injectable chitosan/starch/beta-glycerol phosphate hydrogel for sustaining normal chondrocyte function. Int J Pharm. 2010 May 31;391(1-2):115-24 Authors: Ngoenkam J, Faikrua A, Yasothornsrikul S, Viyoch J An injectable hydrogel for chondrocyte delivery was developed by blending chitosan and starch derived from various sources with beta-glycerol phosphate (beta-GP) in the expectation that it would retain a liquid state at room temperature and gel at raised temperatures. Rheological investigation indicated that the system consisting of chitosan derived from crab shell and corn starch at 4:1 by weight ratio (1.53%, w/v of total polymers), and 6.0% (w/v) beta-GP (C/S/GP system) exhibited the sharpest sol-gel transition at 37+/-2 degrees C. The C/S/GP hydrogel was gradually degraded by 67% within 56 days in PBS containing 0.02 mg/ml lysozyme. The presence of starch in the system increased the water absorption of the hydrogel when compared to the system without starch. SEM observation revealed to the interior structure of the C/S/GP hydrogel having interconnected pore structure (average pore size 26.4 microm) whereas the pore size of the hydrogel without starch was 19.8 microm. The hydrogel also showed an ability to maintain chondrocyte phenotype as shown by cell morphology and expression of type II collagen mRNA and protein. In vivo study revealed that the gel was formed rapidly and localized at the injection site. PMID: 20206248 [PubMed - indexed for MEDLINE] | | |
| A micro-channel-well system for culture and differentiation of embryonic stem cells on different types of substrate.
July 28, 2010 at 5:23 PM
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| | A micro-channel-well system for culture and differentiation of embryonic stem cells on different types of substrate. Biomed Microdevices. 2010 Jun;12(3):505-11 Authors: Liu L, Luo C, Ni X, Wang L, Yamauchi K, Nomura SM, Nakatsuji N, Chen Y We have developed a combined micro-channel and micro-well system for easy cell loading, culture and post-culture operation on a chip. To demonstrate the reliability of the system, on chip cell culture and differentiation were performed with different types of substrates made of culture dish, glass cover slide and polydimethylsiloaxe (PDMS). As expected, mouse embryo fibroblasts (MEF) showed different adhesion and growth rate on different substrates. When embryonic stem (ES) cells were co-cultured with MEFs, the formation of ES colonies is efficient on both glass and Petri dish, although PDMS could also be used. Finally, ES cell differentiation with neuron growth factors was performed on different substrates, showing clear advantages of using culture Petri dish over both glass and PDMS. PMID: 20177790 [PubMed - indexed for MEDLINE] | | |
| Reduced versican cleavage due to Adamts9 haploinsufficiency is associated with cardiac and aortic anomalies.
July 28, 2010 at 5:23 PM
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| | Reduced versican cleavage due to Adamts9 haploinsufficiency is associated with cardiac and aortic anomalies. Matrix Biol. 2010 May;29(4):304-16 Authors: Kern CB, Wessels A, McGarity J, Dixon LJ, Alston E, Argraves WS, Geeting D, Nelson CM, Menick DR, Apte SS Here, we demonstrate that ADAMTS9, a highly conserved versican-degrading protease, is required for correct cardiovascular development and adult homeostasis. Analysis of Adamts9(+/LacZ) adult mice revealed anomalies in the aortic wall, valvulosinus and valve leaflets. Abnormal myocardial projections and 'spongy' myocardium consistent with non-compaction of the left ventricle were also found in Adamts9(+/LacZ) mice. During development, Adamts9 was expressed in derivatives of the Secondary Heart Field, vascular smooth muscle cells in the arterial wall, mesenchymal cells of the valves, and non-myocardial cells of the ventricles, but expression also continued in the adult heart and ascending aorta. Thus, the adult cardiovascular anomalies found in Adamts9(+/LacZ) hearts could result from subtle developmental alterations in extracellular matrix remodeling or defects in adult homeostasis. The valvular and aortic anomalies of Adamts9(+/LacZ) hearts were associated with accumulation of versican and a decrease in cleaved versican relative to WT littermates. These data suggest a potentially important role for ADAMTS9 cleavage of versican, or other, as yet undefined substrates in development and allostasis of cardiovascular extracellular matrix. In addition, these studies identify ADAMTS9 as a potential candidate gene for congenital cardiac anomalies. Mouse models of ADAMTS9 deficiency may be useful to study myxomatous valve degeneration. PMID: 20096780 [PubMed - indexed for MEDLINE] | | |
| Enhanced differentiation of retinal progenitor cells using microfabricated topographical cues.
July 28, 2010 at 5:23 PM
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| | Enhanced differentiation of retinal progenitor cells using microfabricated topographical cues. Biomed Microdevices. 2010 Jun;12(3):363-9 Authors: Steedman MR, Tao SL, Klassen H, Desai TA Due to the retina's inability to replace photoreceptors lost during retinal degeneration, significant interest has been placed in methods to implant replacement cells. Polymer scaffolds are increasingly being studied as vehicles for cellular delivery to degenerated retinas. Previously, we fabricated poly(methyl methacrylate) thin film scaffolds that increased survival and integration of implanted retinal progenitor cells (RPCs). Additionally, these scaffolds minimized the trauma and cellular response associated with implantation of foreign bodies into mouse eyes. Here, we demonstrate that biodegradable polycaprolactone (PCL) thin film scaffolds can be fabricated with integrated microtopography. Microfabricated topography in a PCL thin film enhanced the attachment and organization of RPCs compared to unstructured surfaces. Using real-time quantitative polymerase chain reaction we also observed that attachment to microtopography induced cellular differentiation. RPCs grown on PCL thin films exhibited an increase in gene expression for the photoreceptor markers recoverin and rhodopsin, an increase in the glial and Müller cell marker GFAP, and a decrease in SOX2 gene expression (a marker for undifferentiated progenitor cells) compared to cells grown on unmodified tissue culture polystyrene (TCPS). PMID: 20077017 [PubMed - indexed for MEDLINE] | | |
| Analysis of Wnt pathway genes during ex vivo expansion and neutrophil differentiation of umbilical-cord-blood-derived CD34 cells.
July 28, 2010 at 5:23 PM
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| | Analysis of Wnt pathway genes during ex vivo expansion and neutrophil differentiation of umbilical-cord-blood-derived CD34 cells. Vox Sang. 2010 Apr;98(3 Pt 1):e290-4 Authors: Gallagher RC, Tura-Ceide O, Turner M, Barclay R Previous work has shown that optimal ex vivo expansion and differentiation of CD34(+) progenitor cells into neutrophils is by addition of Flt3-L, SCF and G-CSF. Here we report that a variety of genes involved in the WNT pathway are transcriptionally active in both undifferentiated and differentiated umbilical cord blood CD34(+) cells, however statistically significant changes in gene expression are not always consistent across UCB samples. PMID: 20059757 [PubMed - indexed for MEDLINE] | | |
| Hypoxia enhances proliferation of mouse embryonic stem cell-derived neural stem cells.
July 28, 2010 at 5:23 PM
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| | Hypoxia enhances proliferation of mouse embryonic stem cell-derived neural stem cells. Biotechnol Bioeng. 2010 Jun 1;106(2):260-70 Authors: Rodrigues CA, Diogo MM, da Silva CL, Cabral JM Neural stem (NS) cells can provide a source of material with potential applications for neural drug testing, developmental studies, or novel treatments for neurodegenerative diseases. Herein, the ex vivo expansion of a model system of mouse embryonic stem (mES) cell-derived NS cells was characterized and optimized, cells being cultivated under adherent conditions. Culture was first optimized in terms of initial cell plating density and oxygen concentration, known to strongly influence brain-derived NS cells. To this end, the growth of cells cultured under hypoxic (2%, 5%, and 10% O(2)) and normoxic (20% O(2)) conditions was compared. The results showed that 2-5% oxygen, without affecting multipotency, led to fold increase values in total cell number about twice higher than observed under 20% oxygen (20-fold vs. 10-fold, respectively) this effect being more pronounced when cells were plated at low density. With an optimal cell density of 10(4) cells/cm(2), the maximum growth rates were 1.9 day(-1) under hypoxia versus 1.7 day(-1) under normoxia. Cell division kinetics analysis by flow cytometry based on PKH67 tracking showed that when cultured in hypoxia, cells are at least one divisional generation ahead compared to normoxia. In terms of cell cycle, a larger population in a quiescent G(0) phase was observed in normoxic conditions. The optimization of NS cell culture performed here represents an important step toward the generation of a large number of neural cells from a reduced initial population, envisaging the potential application of these cells in multiple settings. PMID: 20014442 [PubMed - indexed for MEDLINE] | | |
| A comparative study of seeding techniques and three-dimensional matrices for mesenchymal cell attachment.
July 28, 2010 at 5:23 PM
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| | A comparative study of seeding techniques and three-dimensional matrices for mesenchymal cell attachment. J Tissue Eng Regen Med. 2010 Jul 26; Authors: Griffon DJ, Abulencia JP, Ragetly GR, Fredericks LP, Chaieb S Mesenchymal stem cells (MSCs) offer significant potential as a cell source in tissue-engineering applications because of their multipotent ability. The objective of this study was to evaluate the behaviour of MSCs during the seeding phase, using four different seeding techniques (spinner flask, custom vacuum system combined with a perfused bioreactor or with an orbital shaker, and orbital shaker) with four different scaffold materials [polyglycolic acid, poly(lactic acid), calcium phosphate and chitosan-hyaluronic acid]. Scaffolds were selected for their structural and/or chemical similarity with bone or cartilage, and characterized via scanning electron microscopy (SEM) and measurement of fluid retention. Cell attachment was compared between seeding techniques and scaffolds via cell-binding kinetics, cell viability and DNA quantification. SEM was used to evaluate cell distribution throughout the constructs. We discovered from cell suspension kinetics and DNA data that the type of loading (i.e. direct or indirect) mainly influences the delivery of cells to their respective scaffolds, and that dynamic seeding in a spinner flask tended to improve the cellularity of polymer constructs, especially mesh. Regardless of the seeding method, bone marrow-derived MSCs displayed a superior affinity for calcium phosphate scaffolds, which may be related to their hydrophobicity. MSCs tended to aggregate into flat sheets, occluding the external pores of matrices and affecting cell distribution, regardless of seeding technique or scaffold. Taken together, these results provide insight into the design of future experiments using MSCs to engineer functional tissue. Copyright (c) 2010 John Wiley & Sons, Ltd. PMID: 20661904 [PubMed - as supplied by publisher] | | | | 
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