| Pyromellitamide gelators: exponential rate of aggregation, hierarchical assembly, and their viscoelastic response to anions.
January 6, 2010 at 10:45 am
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| | Pyromellitamide gelators: exponential rate of aggregation, hierarchical assembly, and their viscoelastic response to anions. Langmuir. 2009 Aug 4;25(15):8586-92 Authors: Tong KW, Dehn S, Webb JE, Nakamura K, Braet F, Thordarson P The gelation and aggregation properties of a newly synthesized structurally simplified tetrahexyl pyromellitamide 2 have been studied and compared to the previously reported tetra(ethylhexanoate) pyromellitide 1, indicating that the ester groups in the latter significantly impede its aggregation. Morphology studies (AFM and TEM) on the aggregates formed by tetrahexyl pyromellitamide 2 in cyclohexane revealed highly uniform aggregates with different dimensions at different starting concentrations, suggesting that this molecule aggregates in a hierarchical fashion from a one-dimensional supramolecular polymer through hollow tubes or compressed helices to a network structure and then to a gel. This hypothesis is further supported by viscosity measurements that indicate a crossover point where individual supramolecular fibers get entangled at concentrations above ca. 3 mM in cyclohexane. Addition of 1 equiv of tetraalkylammonium salts of chloride or bromide, however, caused the viscosities of these pyromellitamide solutions to drop by a factor of 2-3 orders of magnitude, demonstrating the sensitivity of these aggregates to the presence of small anions. The sensitivity to anions does depend on the solubility of the salts used as small anion salts with little solubility in cyclohexane did not show this effect. Time-dependent viscosity studies showed that the aggregation of pyromellitamide 2 follows an exponential rate law, possibly related to the columnar rearrangements that are associated with the observed 6 angstroms contraction in d spacing in the XRD pattern of these gels. These results, particularly on the importance of kinetics of aggregation of self-assembled pyromellitamide gels, will be useful for future development of related materials for a number of applications, including tissue engineering and drug delivery. PMID: 20050045 [PubMed - in process] |
| Heparin-based nanoparticles.
January 6, 2010 at 10:45 am
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| | Heparin-based nanoparticles. Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2010 Jan;2(1):77-87 Authors: Kemp MM, Linhardt RJ The combination of nanoparticles and biological molecules is of intense interest because of the synergistic properties offered by such newly synthesized composites. Heparin (HP), conjugated to nanomaterials, has recently been investigated for its chemical and biological properties. HP has a number of biological activities that can be enhanced when composited with nanoparticles. In addition, HP improves the biocompatibility of nanoparticles improving their performance in various biological applications. A variety of recent research combines HP and nanomaterials for a myriad of applications. HP has been conjugated to the surface of the nanoparticles, such as magnetic and metallic nanoparticles, or biodegradable and nondegradable synthetic polymers. HP has also been incorporated into the nanoparticles. There are numerous possibilities for material composites and chemistries that incorporate HP. This opens the door for novel applications ranging from improving anticoagulant activity, for anticancer and antitumor therapy, to tissue engineering and biosensors. This review examines the different possibilities of HP-based nanoparticle composites and their medicinal or biological applications. PMID: 20049832 [PubMed - in process] |
| Nanofibrous composites for tissue engineering applications.
January 6, 2010 at 10:45 am
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| | Nanofibrous composites for tissue engineering applications. Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2009 Jul;1(4):369-90 Authors: McCullen SD, Ramaswamy S, Clarke LI, Gorga RE Development of artificial matrices for tissue engineering is a crucial area of research in the field of regenerative medicine. Successful tissue scaffolds, in analogy with the natural mammalian extracellular matrix (ECM), are multi-component, fibrous, and on the nanoscale. In addition, to this key morphology, artificial scaffolds must have mechanical, chemical, surface, and electrical properties that match the ECM or basement membrane of the specific tissue desired. In particular, these material properties may vary significantly for the four primary tissues in the body: nerve, muscle, epithelial, and connective. In order to address this complex array of attributes with a polymeric material, a nanocomposite approach, employing a blend of materials, addition of a particle to enhance particular properties, or a surface treatment, is likely to be required. In this review, we examine nanocomposite approaches to address these diverse needs as a function of tissue type. The review is intended as a bridge between material scientists and biomedical researchers to give basic background information on tissue biology to the former, and on material processing approaches to the latter, in a general manner, and specifically review fibrous nanocomposite materials that have previously been used for cell studies, either in vivo or in vitro. PMID: 20049804 [PubMed - in process] |
| Nanostructured polymer scaffolds for tissue engineering and regenerative medicine.
January 6, 2010 at 10:45 am
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| | Nanostructured polymer scaffolds for tissue engineering and regenerative medicine. Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2009 Mar;1(2):226-36 Authors: Smith IO, Liu XH, Smith LA, Ma PX The structural features of tissue engineering scaffolds affect cell response and must be engineered to support cell adhesion, proliferation and differentiation. The scaffold acts as an interim synthetic extracellular matrix (ECM) that cells interact with prior to forming a new tissue. In this review, bone tissue engineering is used as the primary example for the sake of brevity. We focus on nanofibrous scaffolds and the incorporation of other components including other nanofeatures into the scaffold structure. Since the ECM is comprised in large part of collagen fibers, between 50 and 500 nm in diameter, well-designed nanofibrous scaffolds mimic this structure. Our group has developed a novel thermally induced phase separation (TIPS) process in which a solution of biodegradable polymer is cast into a porous scaffold, resulting in a nanofibrous pore-wall structure. These nanoscale fibers have a diameter (50-500 nm) comparable to those collagen fibers found in the ECM. This process can then be combined with a porogen leaching technique, also developed by our group, to engineer an interconnected pore structure that promotes cell migration and tissue ingrowth in three dimensions. To improve upon efforts to incorporate a ceramic component into polymer scaffolds by mixing, our group has also developed a technique where apatite crystals are grown onto biodegradable polymer scaffolds by soaking them in simulated body fluid (SBF). By changing the polymer used, the concentration of ions in the SBF and by varying the treatment time, the size and distribution of these crystals are varied. Work is currently being done to improve the distribution of these crystals throughout three-dimensional scaffolds and to create nanoscale apatite deposits that better mimic those found in the ECM. In both nanofibrous and composite scaffolds, cell adhesion, proliferation and differentiation improved when compared to control scaffolds. Additionally, composite scaffolds showed a decrease in incidence of apoptosis when compared to polymer control in bone tissue engineering. Nanoparticles have been integrated into the nanostructured scaffolds to deliver biologically active molecules such as growth and differentiation factors to regulate cell behavior for optimal tissue regeneration. PMID: 20049793 [PubMed - in process] |
| Current status of nanotechnology approaches for cardiovascular disease: a personal perspective.
January 6, 2010 at 10:45 am
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| | Current status of nanotechnology approaches for cardiovascular disease: a personal perspective. Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2009 Mar;1(2):149-55 Authors: Buxton DB Nanotechnology is poised to have an increasing impact on cardiovascular health in coming years. Diagnostically, multiplexed point-of-care devices will enable rapid genotyping and biomarker measurement to optimize and tailor therapies for the individual patient. Nanoparticle-based molecular imaging agents will take advantage of targeted agents to provide increased insight into disease pathways rather then simply providing structural and functional information. Drug delivery will be impacted by targeting of nanoparticle-encapsulated drugs to the site of action, increasing the effective concentration and decreasing systemic dosage and side effects. Controlled and tailored release of drugs from polymers will improve control of pharmacokinetics and bioavailability. The application of nanotechnology to tissue engineering will facilitate the fabrication of better tissue implants in vitro, and provide scaffolds to promote regeneration in vivo taking advantage of the body's own repair mechanisms. Medical devices will benefit from the development of nanostructured surfaces and coatings to provide better control of thrombogenicity and infection. Taken together, these new technologies have enormous potential for improving the diagnosis and treatment of cardiovascular diseases. PMID: 20049786 [PubMed - in process] |
| Nanotechnology and orthopedics: a personal perspective.
January 6, 2010 at 10:45 am
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| | Nanotechnology and orthopedics: a personal perspective. Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2009 Jan;1(1):6-10 Authors: Laurencin CT, Kumbar SG, Nukavarapu SP Bone is a nanocomposite material comprised of hierarchically arranged collagen fibrils, hydroxyapatite and proteoglycans in the nanometer scale. Cells are accustomed to interact with nanostructures, thus providing the cells with a natural bone-like environment that potentially enhance bone tissue regeneration/repair. In this direction, nanotechnology provides opportunities to fabricate as well as explore novel properties and phenomena of functional materials, devices, and systems at the nanometer-length scale. Recent studies have provided significant insights into the influence of topographical features in regulating cell behavior. Topographical features provide essential chemical and physical cues that cells can recognize and elicit desired cellular functions including preferential adhesion, migration, proliferation, and expression of specific cell phenotype to bring desired effects. The current article will address some of the nanotechnology implications in addressing issues related to orthopedic implants performance and tissue engineering approach to bone repair/regeneration. PMID: 20049774 [PubMed - in process] |
| Immobilization of fibronectin in chitosan substrates improves cell adhesion and proliferation.
January 6, 2010 at 10:45 am
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| | Immobilization of fibronectin in chitosan substrates improves cell adhesion and proliferation. J Tissue Eng Regen Med. 2010 Jan 4; Authors: Custódio CA, Alves CM, Reis RL, Mano JF Covalent grafting of biomolecules is a strategy to improve the biocompatibility and bioactivity of materials. However, it is critical to maintain the biological activity of the biomolecule upon its attachment to the surface. In the present study we compared the biological properties of chitosan, in which the surface was enriched with fibronectin (Fn), using two methodologies: chemical immobilization, using a water-soluble carbodiimide; and simple adsorption. X-ray photoelectron spectroscopy studies confirmed the successful immobilization of Fn onto modified membranes. SaOs-2 cells were seeded onto these surfaces to assess the biological consequences of such modifications. The presence of Fn stimulated cell adhesion on chitosan. It was found that after 7 days of culture in the presence of covalently attached Fn, the cells are confluent; significantly fewer cells were detected in unmodified film and in film with adsorbed Fn. This result is consistent with the fact that considerable desorption of Fn from chitosan takes place within 24 h in culture medium. This study showed that Fn may be easily covalently attached onto chitosan substrates, improving the biological performance of the material. The technique could find applications in tissue-engineering strategies, as the surface modification of chitosan-based substrates could be carried out in more complex geometries, such as in scaffolds or particles. Copyright (c) 2009 John Wiley & Sons, Ltd. PMID: 20049746 [PubMed - as supplied by publisher] |
| Isolation of amniotic epithelial stem cells.
January 6, 2010 at 10:45 am
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| | Isolation of amniotic epithelial stem cells. Curr Protoc Stem Cell Biol. 2010 Jan;Chapter 1:Unit 1E.3 Authors: Miki T, Marongiu F, Dorko K, Ellis EC, Strom SC Many of the cell types that can be isolated from placental tissues retain phenotypic plasticity that makes them an interesting source of cells for regenerative medicine. Several procedures for the isolation of stem cells from different parts of the placenta have been reported. This unit describes a detailed and simple protocol for the selective isolation of amniotic epithelial cells from human term placenta without disturbing the mesenchymal layer. We also introduce a simple density separation technique for the enrichment of the population for SSEA-4 positive cells. PMID: 20049689 [PubMed - in process] |
| BMP-2/PLGA Delayed-Release Microspheres Composite Graft, Selection of Bone Particulate Diameters, and Prevention of Aseptic Inflammation for Bone Tissue Engineering.
January 6, 2010 at 10:45 am
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| | BMP-2/PLGA Delayed-Release Microspheres Composite Graft, Selection of Bone Particulate Diameters, and Prevention of Aseptic Inflammation for Bone Tissue Engineering. Ann Biomed Eng. 2010 Jan 5; Authors: Ji Y, Xu GP, Zhang ZP, Xia JJ, Yan JL, Pan SH Autogenous bone grafts are widely used in the repair of bone defects. Growth factors such as bone morphogenetic protein 2 (BMP-2) can induce bone regeneration and enhance bone growth. The combination of an autogenous bone graft and BMP-2 may provide a better osteogenic effect than either treatment alone, but BMP-2 is easily inactivated in body fluid. The objective of this study was to develop a technique that can better preserve the in vivo activity of BMP-2 incorporated in bone grafts. In this study, we first prepared BMP-2/poly(lactic-co-glycolic acid) (PLGA) delayed-release microspheres, and then combined collagen, the delayed-release microspheres, and rat autologous bone particulates to form four groups of composite grafts with different combinations: collagen in group A; collagen combined with bone particulates in group B; collagen combined with BMP-2/PLGA delayed-release microspheres in group C; and collagen combined with both bone particulates and BMP-2/PLGA delayed-release microspheres in group D. The four groups of composite grafts were implanted into the gluteus maximus pockets in rats. The ectopic osteogenesis and ALP level in group D (experimental group) were compared with those in groups A, B, and C (control groups) to study whether it had higher osteogenic capability. Results showed that the composite graft design increased the utility of BMP-2 and reduced the required dose of BMP-2 and volume of autologous bone. The selection of bone particulate diameter had an impact on the osteogenetic potential of bone grafts. Collagen prevented the occurrence of aseptic inflammation and improved the osteoinductivity of BMP-2. These results showed that this composite graft design is effective and feasible for use in bone repair. PMID: 20049636 [PubMed - as supplied by publisher] |
| Stem cells derived from cord blood in transplantation and regenerative medicine.
January 6, 2010 at 10:45 am
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| | Stem cells derived from cord blood in transplantation and regenerative medicine. Dtsch Arztebl Int. 2009 Dec;106(50):831-6 Authors: Reimann V, Creutzig U, Kögler G BACKGROUND: Physicians of any specialty may be the first persons to whom prospective parents turn for information about the acquisition and storage of stem cells derived from cord blood. Stem cells can potentially be used to treat many diseases, yet they are not a panacea. This article provides an overview of their current and possible future applications. METHODS: Original papers were retrieved by a selective search of the literature, and the Internet sites and advertising brochures of private stem cell banks were also examined. RESULTS: Allogeneic hematopoietic stem cells derived from umbilical cord blood (obtained from healthy donors, rather than from the patient to be treated) have been in routine use worldwide for more than ten years in the treatment of hematopoietic diseases. Experiments in cell culture and in animal models suggest that these cells might be of therapeutic use in regenerative medicine, but also show that this potential can be realized only if the cells are not cryopreserved. There is as yet no routine clinical application of autologous hematopoietic stem cells from cord blood (self-donation of blood), even though cord blood has been stored in private banks for more than ten years. CONCLUSIONS: Autologous stem cells from cord blood have poor prospects for use in regenerative medicine, because they have to be cryopreserved until use. Physicians should tell prospective parents that they have no reason to feel guilty if they choose not to store cord blood in a private bank. PMID: 20049094 [PubMed - in process] |
| Interaction of wingless protein (Wnt), transforming growth factor-beta1, and hyaluronan production in fetal and postnatal fibroblasts.
January 6, 2010 at 10:45 am
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| | Interaction of wingless protein (Wnt), transforming growth factor-beta1, and hyaluronan production in fetal and postnatal fibroblasts. Plast Reconstr Surg. 2010 Jan;125(1):74-88 Authors: Carre AL, James AW, MacLeod L, Kong W, Kawai K, Longaker MT, Lorenz HP BACKGROUND: Mammalian fetal skin injury heals scarlessly. The intrinsic differences between embryonic and adult fibroblasts that underlie this observation are poorly understood. Several studies have linked Wnt proteins with skin morphogenesis. The authors' study aimed to establish a correlation between beta-catenin-dependent (canonical) Wnt protein, transforming growth factor (TGF)-beta1, and the expression of hyaluronan synthesis enzymes during scarless versus scarring wound healing. METHODS: Wnt signaling was quantified after 1.5-mm skin wounds were created in BAT-gal fetal (e16.5) and postnatal (p1) mice. Canonical Wnt signals were localized by X-gal staining and quantified with quantitative real-time polymerase chain reaction. Primary embryonic and postnatal mouse dermal fibroblasts were treated with recombinant Wnt3a or TGF-beta1. Proliferation was assayed by bromodeoxyuridine incorporation. Gene expression of enzymes that regulate hyaluronan production and turnover was examined by quantitative real-time polymerase chain reaction (hyaluronan synthases or HAS1-3, hyaluronadase-2), as well as other target genes for Wnt and TGF-beta (Axin2, TGF-beta1, TGF-beta3, type 1 collagen, proliferating cell nuclear antigen). RESULTS: Canonical Wnt signaling increased following wounding in postnatal, but not fetal, mice. In vitro, rmWnt3a increased postnatal fibroblast proliferation but not in embryonic cells. Both Wnt3a and TGF-beta1 induced HAS2 and HAS3 gene expression in embryonic fibroblasts, while HAS1 and Hyal2 were induced in postnatal fibroblasts. Finally, rmWnt3a significantly increased type I collagen expression, particularly in postnatal fibroblasts, and influenced expression of TGF-beta isoforms. CONCLUSIONS: Increased canonical Wnt signaling occurs during postnatal but not fetal cutaneous wound repair. Fetal and postnatal fibroblasts have a disparate response to rmWnt3a in vitro. rmWnt3a affects postnatal fibroblasts in a similar fashion to rhTGF-beta1, a known profibrotic cytokine. PMID: 20048602 [PubMed - in process] |
| Genetic and biochemical definition of the Hedgehog receptor.
January 6, 2010 at 10:45 am
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| | Genetic and biochemical definition of the Hedgehog receptor. Genes Dev. 2010 Jan 1;24(1):57-71 Authors: Zheng X, Mann RK, Sever N, Beachy PA Although the transporter-like protein Patched (Ptc) is genetically implicated in reception of the extracellular Hedgehog (Hh) protein signal, a clear definition of the Hh receptor is complicated by the existence of additional Hh-binding proteins and, in Drosophila, by the lack of physical evidence for direct binding of Hh to Ptc. Here we show that activity of Ihog (Interference hedgehog), or of its close relative Boi (Brother of Ihog), is absolutely required for Hh biological response and for sequestration of the Hh protein to limit long-range signaling. We demonstrate that Ihog interacts directly with Ptc, is required for presentation of Ptc on the cell surface, and that Ihog and Ptc are both required for high-affinity Hh binding. On the basis of their joint roles in ligand binding, signal transduction, and receptor trafficking, we conclude that Ihog and Ptc together constitute the Drosophila Hh receptor. PMID: 20048000 [PubMed - in process] |
| Tendon augmentation grafts: a systematic review.
January 6, 2010 at 10:45 am
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| | Tendon augmentation grafts: a systematic review. Br Med Bull. 2010 Jan 4; Authors: Longo UG, Lamberti A, Maffulli N, Denaro V Introduction Several biomaterials are available to bridge large tendon defects or reinforce tenuous tendon repairs. Methods We performed a comprehensive search of PubMed, Medline, Cochrane, CINAHL, and Embase databases using various combinations of the commercial names of each scaffold and the keywords 'tendon', 'rotator cuff', 'supraspinatus tendon', 'Achilles tendon', 'scaffold', 'biomaterials', 'extracellular matrix', 'substitute', and 'devices' over the years 1966-2009. All articles relevant to the subject were retrieved, and their bibliographies hand searched for further references in the context to biomaterials for tendon repair. Results Many biomaterials are available for tendon augmentation. Scanty evidence is available for the use of these scaffolds. Discussion The emerging field of tissue engineering holds the promise to use biomaterials for tendon augmentation. Preliminary studies support the idea that these biomaterials have the ability to provide an alternative for tendon augmentation. However, available data are lacking to allow definitive conclusion on the use of biomaterials for tendon augmentation. Additionally, the prevalence of postoperative complications encountered with their use varies within the different studies. Conclusion Rather than providing strong evidence for or against the use of these materials for tendon augmentation, this study instead generates potential areas for additional prospective investigation. PMID: 20047971 [PubMed - as supplied by publisher] |
| A versatile pH sensitive chondroitin sulfate-PEG tissue adhesive and hydrogel.
January 6, 2010 at 10:45 am
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| | A versatile pH sensitive chondroitin sulfate-PEG tissue adhesive and hydrogel. Biomaterials. 2010 Jan 2; Authors: Strehin I, Nahas Z, Arora K, Nguyen T, Elisseeff J We developed a chondroitin sulfate-polyethylene glycol (CS-PEG) adhesive hydrogel with numerous potential biomedical applications. The carboxyl groups on chondroitin sulfate (CS) chains were functionalized with N-hydroxysuccinimide (NHS) to yield chondroitin sulfate succinimidyl succinate (CS-NHS). Following purification, the CS-NHS molecule can react with primary amines to form amide bonds. Hence, using six arm polyethylene glycol amine PEG-(NH(2))(6) as a crosslinker we formed a hydrogel which was covalently bound to proteins in tissue via amide bonds. By varying the initial pH of the precursor solutions, the hydrogel stiffness, swelling properties, and kinetics of gelation could be controlled. The sealing/adhesive strength could also be modified by varying the damping and storage modulus properties of the material. The adhesive strength of the material with cartilage tissue was shown to be ten times higher than that of fibrin glue. Cells encapsulated or in direct contact with the material remained viable and metabolically active. Furthermore, CS-PEG material produced minimal inflammatory response when implanted subcutaneously in a rat model and enzymatic degradation was demonstrated in vitro. This work establishes an adhesive hydrogel derived from biological and synthetic components with potential application in wound healing and regenerative medicine. PMID: 20047758 [PubMed - as supplied by publisher] |
| Small Molecules and Stem Cells. Potency and Lineage Commitment: The New Quest for the Fountain of Youth.
January 6, 2010 at 10:45 am
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| | Small Molecules and Stem Cells. Potency and Lineage Commitment: The New Quest for the Fountain of Youth. J Med Chem. 2010 Jan 4; Authors: Lukaszewicz AI, McMillan MK, Kahn M PMID: 20047330 [PubMed - as supplied by publisher] |
| Stem cells in musculoskeletal engineered tissue.
January 6, 2010 at 10:45 am
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| | Stem cells in musculoskeletal engineered tissue. Curr Opin Biotechnol. 2009 Oct;20(5):537-44 Authors: Deans TL, Elisseeff JH PMID: 19879127 [PubMed - indexed for MEDLINE] |
| [Experimental study on expanded polytetrafluoroethylene as wound covering]
January 6, 2010 at 10:45 am
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| | [Experimental study on expanded polytetrafluoroethylene as wound covering] Zhonghua Shao Shang Za Zhi. 2009 Apr;25(2):133-6 Authors: Tian T, Li YC, Zhou B, Zhang PJ OBJECTIVE: To assess the feasibility of a polymer material-expanded polytetrafluoroethylene (ePTFE) as wound covering. METHODS: Forty-five Sprague Dawley (SD) rats inflicted with open wound on the back were divided into 3 groups, each group 15 rats. Wounds in the autograft group were covered with autologous skin. Wounds in the allograft group were covered with skin from 15 Wistar rats (donor). Wounds in the experiment group were covered with ePTFE. Wound healing in each group was observed with naked eye. Tissue specimens collected on 3rd, 7th, and 14th post-operative day (POD) respectively were stained with HE and examined under light microscope. Macrophages, lymphocytes and fibroblasts were quantified. IL-2 and IFN-gamma levels in the infiltrating mononuclear cells were assessed by immunohistochemistry with expression of gray value. RESULTS: Wounds in rats of autograft group and experiment group healed well without redness, swelling or infection. Rejection was evident in the allograft group rats on 8th POD, including epidermis degeneration and focal necrosis in different degree, plus red swelling on wound edge. The numbers of macrophages, fibroblasts, lymphocytes in allograft group were significantly higher than those in autograft group and experiment group (P < 0.01). The average gray values of IL-2 and IFN-gamma of allograft group on 7th POD were 129 +/- 7 and 113.7 +/- 2.7, which were significantly lower than those in the experiment group (144 +/- 8, 137.3 +/- 1.9, respectively, P < 0.01) and allograft group (189 +/- 6, 180.3 +/- 3.7, respectively, P < 0.01). CONCLUSIONS: ePTFE will induce minimal inflammatory response and foreign body reaction. It is unlikely to cause side effect when applied to wound surface for a prolonged period. Thus, it is suitable to use ePTFE as wound surface covering. PMID: 19799040 [PubMed - indexed for MEDLINE] |
| Influence of micro-well biomimetic topography on intestinal epithelial Caco-2 cell phenotype.
January 6, 2010 at 10:45 am
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| | Influence of micro-well biomimetic topography on intestinal epithelial Caco-2 cell phenotype. Biomaterials. 2009 Dec;30(36):6825-34 Authors: Wang L, Murthy SK, Fowle WH, Barabino GA, Carrier RL A microfabrication approach was utilized to create topographic analogs of intestinal crypts on a polymer substrate. It was hypothesized that biomimetic crypt-like micro-architecture may induce changes in small intestinal cell (i.e. Caco-2 cell) phenotype. A test pattern of micro-well features with similar dimensions (50, 100, and 500 microm diameter, 50 microm spacing, 120 microm in depth) to the crypt structures found in native basal lamina was produced in the surface of a poly(dimethylsiloxane) (PDMS) substrate. PDMS surfaces were coated with fibronectin, seeded with intestinal-epithelial-cell-like Caco-2 cells, and cultured up to fourteen days. The cells were able to crawl along the steep side walls and migrated from the bottom to the top of the well structures, completely covering the surface by 4-5 days in culture. The topography of the PDMS substrates influenced cell spreading after seeding; cells spread faster and in a more uniform fashion on flat surfaces than on those with micro-well structures, where cell protrusions extending to micro-well side walls was evident. Substrate topography also affected cell metabolic activity and differentiation; cells had higher mitochondrial activity but lower alkaline phosphatase activity at early time points in culture (2-3 days post-seeding) when seeded on micro-well patterned PDMS substrates compared to flat substrates. These results emphasize the importance of topographical design properties of a scaffolds used for tissue engineered intestine. PMID: 19766306 [PubMed - indexed for MEDLINE] |
| Quantitative analysis of the proliferation and differentiation of rat articular chondrocytes in alginate 3D culture.
January 6, 2010 at 10:45 am
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| | Quantitative analysis of the proliferation and differentiation of rat articular chondrocytes in alginate 3D culture. Iran Biomed J. 2009 Jul;13(3):153-60 Authors: Baghaban Eslaminejad M, Taghiyar L, Falahi F BACKGROUND: While articular chondrocytes are among those appropriate candidates for cartilage regeneration, the cell dedifferentiation during monolayer culture has limited their application. Several investigations have indicated the usefulness of alginate, but the topic of proliferation and differentiation of chondrocytes in alginate culture has still remained controversial. METHODS: Rat articular chondrocytes were released by enzymatic digestion, plated at 5 x 104 cells/cm2 and culture-expanded. Passaged-5 cells were then cultivated in alginate as 2-mm beads for a period of two months during which the expansion rate and the level of cell differentiation were determined by [3-(A, 5- dimethylthiazolyl- 2-yl)-1, 5-diphenyl tetrazolium bromide] assay and real-time PCR analysis respectively and compared with those of chondrocytes in monolayer culture. RESULTS: Average population doubling time in alginate cultures (10.04 +/- 0.9 days) tended to be significantly (P<0.05) higher than that in monolayer cultures (2.94 +/- 0.3 days). The period of alginate culture could be subdivided into expansion phase (Days 0-40); during which proliferation appeared to be high and differentiation phase (Days 40-60) during which the expression of cartilage-specific genes including collagen II and aggrecan tended to be upregulated. During both the proliferation and differentiation phases, the expression of collagen I was low. At chondrocytes monolayer cultures, the proliferating cells appeared to have a very low expression level of cartilage-specific genes and a high expression level of collagen I gene during the entire culture period (P<0.05). CONCLUSION: It seems that alginate provides conditions in which rat articular chondrocytes are able to undergo proliferation and differentiation in certain time point of cultivation period. PMID: 19688021 [PubMed - indexed for MEDLINE] |
| Starch-poly-epsilon-caprolactone microparticles reduce the needed amount of BMP-2.
January 6, 2010 at 10:45 am
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| | Starch-poly-epsilon-caprolactone microparticles reduce the needed amount of BMP-2. Clin Orthop Relat Res. 2009 Dec;467(12):3138-48 Authors: Balmayor ER, Feichtinger GA, Azevedo HS, van Griensven M, Reis RL BMP-2 is currently administered clinically using collagen matrices often requiring large amounts of BMP-2 due to burst release over a short period of time. We developed and tested a novel injectable drug delivery system consisting of starch-poly-epsilon-caprolactone microparticles for inducing osteogenesis and requiring smaller amounts of BMP-2. We evaluated BMP-2 encapsulation efficiency and the in vitro release profile by enzyme-linked immunosorbent assay. BMP-2 was rapidly released during the first 12 hours, followed by sustained release for up to 10 days. We then evaluated the osteogenic potential of dexamethasone (standard osteogenic induction agent) and BMP-2 after incorporation and during release using an osteo/myoblast cell line (C2C12). Alkaline phosphatase activity was increased by released BMP-2. Mineralization occurred after stimulation with BMP-2-loaded microparticles. A luciferase assay for osteocalcin promoter activity showed high levels of activity upon treatment with BMP-2-loaded microparticles. In contrast, no osteogenesis occurred in C2C12 cells using dexamethasone-loaded microparticles. However, human adipose stem cells exposed to the microparticles produced high amounts of alkaline phosphatase. The data suggest starch-poly-epsilon-caprolactone microparticles are suitable carriers for the incorporation and controlled release of glucocorticoids and growth factors. Specifically, they reduce the amount of BMP-2 needed and allow more sustained osteogenic effects. PMID: 19557487 [PubMed - indexed for MEDLINE] |
| Role of the oligodendroglial cytoskeleton in differentiation and myelination.
January 6, 2010 at 10:45 am
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| | Role of the oligodendroglial cytoskeleton in differentiation and myelination. Glia. 2009 Dec;57(16):1691-705 Authors: Bauer NG, Richter-Landsberg C, Ffrench-Constant C Oligodendrocytes, the myelin-forming cells of the central nervous system, are in culture characterized by an elaborate process network, terminating in flat membranous sheets that are rich in myelin-specific proteins and lipids, and spirally wrap axons forming a compact insulating layer in vivo. By analogy with other cell types, maintenance and stability of these processes, as well as the formation of the myelin sheath, likely rely on a pronounced cytoskeleton consisting of microtubules and microfilaments. While the specialized process of wrapping and compaction forming the myelin sheath is not well understood, considerably more is known about how cytoskeletal organization is mediated by extracellular and intracellular signals and other interaction partners during oligodendrocyte differentiation and myelination. Here, we review the current state of knowledge on the role of the oligodendrocyte cytoskeleton in differentiation with an emphasis on signal transduction mechanisms and will attempt to draw out implications for its significance in myelination. PMID: 19455583 [PubMed - indexed for MEDLINE] |
| A healthy get together.
January 6, 2010 at 4:45 am
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| | A healthy get together. Nature. 2009 Nov 12;462(7270):138 Authors: PMID: 19907447 [PubMed - indexed for MEDLINE] | | | 
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