| Interactive effects of mechanical stretching and extracellular matrix proteins on initiating osteogenic differentiation of human mesenchymal stem cells.
October 2, 2009 at 7:57 am
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| | Interactive effects of mechanical stretching and extracellular matrix proteins on initiating osteogenic differentiation of human mesenchymal stem cells. J Cell Biochem. 2009 Sep 30; Authors: Huang CH, Chen MH, Young TH, Jeng JH, Chen YJ Human mesenchymal stem cells (hMSCs) are characterized by their abilities to differentiate into different lineages, including osteoblasts. Besides soluble factors, mechanical strain and extracellular matrix (ECM) proteins play important roles in osteogenic differentiation of hMSCs. However, interactions between them are still not fully understood. The purpose of this study was to investigate the combined effects of insoluble chemical and mechanical factors (ECM proteins vs. cyclic stretching) in driving hMSCs into osteogenic differentiation. To avoid the influence from osteogenic supplements, hMSCs were cultured in regular medium and subjected to cyclic mechanical stretching using a Flexcell Tension system (3% elongation at 0.1 Hz) when they were grown on substrates coated with various ECM proteins (collagen I (Col I), vitronectin (VN), fibronectin (FN), and laminin (LN)). Using alkaline phosphatase (ALP) activity and mineralized matrix deposition as respective indicators of the early and late stages of osteogenesis, we report herein that all of the ECM proteins tested supported hMSC differentiation into osteogenic phenotypes in the absence of osteogenic supplements. Moreover, cyclic mechanical stretching activated the phosphorylation of focal adhesion kinase (FAK), upregulated the transcription and phosphorylation of core-binding factor alpha-1 (Cbfa1), and subsequently increased ALP activity and mineralized matrix deposition. Among the ECM proteins tested, FN and LN exhibited greater effects of supporting stretching-induced osteogenic differentiation than did Col I and VN. The ability of ECM proteins and mechanical stretching to regulate osteogenesis in hMSCs can be exploited in bone tissue engineering via approximate matrix design or application of mechanical stimulation. J. Cell. Biochem. (c) 2009 Wiley-Liss, Inc. PMID: 19795386 [PubMed - as supplied by publisher] |
| Geometry and force control of cell function.
October 2, 2009 at 7:57 am
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| | Geometry and force control of cell function. J Cell Biochem. 2009 Sep 30; Authors: Freytes DO, Wan LQ, Vunjak-Novakovic G Tissue engineering is becoming increasingly ambitious in its efforts to create functional human tissues, and to provide stem cell scientists with culture systems of high biological fidelity. Novel engineering designs are being guided by biological principles, in an attempt to recapitulate more faithfully the complexities of native cellular milieu. Three-dimensional (3D) scaffolds are being designed to mimic native-like cell environments and thereby elicit native-like cell responses. Also, the traditional focus on molecular regulatory factors is shifting towards the combined application of molecular and physical factors. Finally, methods are becoming available for the coordinated presentation of molecular and physical factors in the form of controllable spatial and temporal gradients. Taken together, these recent developments enable the interrogation of cellular behavior within dynamic culture settings designed to mimic some aspects of native tissue development, disease, or regeneration. We discuss here these advanced cell culture environments, with emphasis on the derivation of design principles from the development (the biomimetic paradigm) and the geometry-force control of cell function (the biophysical regulation paradigm). J. Cell. Biochem. (c) 2009 Wiley-Liss, Inc. PMID: 19795385 [PubMed - as supplied by publisher] |
| Comparison of the effect of cryopreservation protocols on the histology of bioengineered tissues.
October 2, 2009 at 7:57 am
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| | Comparison of the effect of cryopreservation protocols on the histology of bioengineered tissues. Histol Histopathol. 2009 Dec;24(12):1531-40 Authors: Serrato D, Nieto-Aguilar R, Garzón I, Roda O, Campos A, Alaminos M The purpose of this study was to compare the effects of five different cryopreservation protocols on the histology of bioengineered tissues. Although several artificial tissues have been developed to the date by tissue engineering, classical histological analysis methods and techniques must be optimized for these new tissues with special properties. The results of this study showed that the use of volatile solutions (formaldehyde, glutaraldehyde, glacial acetic acid and acetone) was not able to prevent the formation of large ice crystals that, in turn, can alter the structure of the artificial tissues. However, preincubation of the tissues in different concentrations of a carbon hydrate (glucose, maltose or trehalose) resulted in a better preservation of the tissue structure. We conclude that the best protocol that allows for an efficient analysis of the bioengineered tissues with very few artifacts is preincubation of the tissues in 0.300M or 0.400M trehalose for 30 or 120 min prior to OCT (optimal cutting temperature) embedding and cryosectioning. For all those reasons, we recommend the use of a cryoprotective agent before OCT embedding of human artificial tissues. PMID: 19795352 [PubMed - in process] |
| Assuring consumer safety without animals: Applications for tissue engineering.
October 2, 2009 at 7:57 am
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| | Assuring consumer safety without animals: Applications for tissue engineering. Organogenesis. 2009 Apr;5(2):67-72 Authors: Westmoreland C, Holmes AM Humans are exposed to a variety of chemicals in their everyday lives through interactions with the environment and through the use of consumer products. It is a basic requirement that these products are tested to assure they are safe under normal and reasonably foreseeable conditions of use. Within the European Union, the majority of tests used for generating toxicological data rely on animals. However recent changes in legislation (e.g., 7(th) amendment of the Cosmetics Directive and REACH) are driving researchers to develop and adopt non-animal alternative methods with which to assure human safety. Great strides have been made to this effect, but what other opportunities/technologies exist that could expedite this? Tissue engineering has increasing scope to contribute to replacing animals with scientifically robust alternatives in basic research and safety testing, but is this application of the technology being fully exploited? This review highlights how the consumer products industry is applying tissue engineering to ensure chemicals are safe for human use without using animals, and identifies areas for future development and application of the technology. PMID: 19794902 [PubMed - in process] |
| Senescent cultures of human dermal fibroblasts modified phenotype when immobilized in fibrin polymer.
October 2, 2009 at 7:57 am
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| | Senescent cultures of human dermal fibroblasts modified phenotype when immobilized in fibrin polymer. J Biomater Sci Polym Ed. 2009;20(13):1929-42 Authors: Acevedo CA, Brown DI, Young ME, Reyes JG One of the limitations in tissue engineering is the restricted ability to expand the number of cells, because somatic cells can duplicate a limited number of times before they lose the ability to divide, leading to a senescent state. Here we report that the interaction of senescent fibroblasts with fibrin polymer can modify the senescent phenotype and partially restore the ability of growth-arrested cells to continue replicating. Primary human dermal fibroblasts were grown to >90% SA/beta-Gal (senescence associated beta-galactosidase). The senescent cells were immobilized in fibrin-polymers by mixing fibrinogen and thrombin solutions. Immobilized senescent cell cultures grew, however, their growth arrested after 24 h of immobilization. The percentage of cells with a positive reaction at SA/beta-Gal did not decrease significantly after immobilization, but the intensity of the stain decreased. The glycolytic activity in immobilized senescent fibroblast was re-established at pre-senescent levels. In conclusion, fibrin induces changes in the phenotype of senescent human fibroblasts. This simple procedure could complement available tissue-engineering techniques to increase the amount of biomass seeded on a fibrin scaffold, which could be beyond senescence. PMID: 19793448 [PubMed - in process] |
| In vitro release of dexamethasone or bFGF from chitosan/hydroxyapatite scaffolds.
October 2, 2009 at 7:57 am
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| | In vitro release of dexamethasone or bFGF from chitosan/hydroxyapatite scaffolds. J Biomater Sci Polym Ed. 2009;20(13):1899-914 Authors: Tiğli RS, Akman AC, Gümüşderelioğlu M, Nohutçu RM Chitosan scaffolds containing dexamethasone (Dex) or basic fibroblast growth factor (bFGF) were developed to create alternative drug-delivery systems for possible tissue-engineering applications such as periodontal bone regeneration. Chitosan solutions (2% and 3% (w/v) in acetic acid) were prepared from chitosan flakes with high deacetylation degree (>85%), then these solutions were freeze-dried at -80 degrees C to obtain scaffolds with interconnected pore structures. Dex and bFGF were incorporated into scaffolds by embedding method (solvent sorption method). The initial loading amounts were varied as 300, 600 and 900 ng Dex per dry scaffold (average dry weight is 3 mg) and 50 or 100 ng bFGF per dry scaffold to a range of deliverable doses. Release studies which were conducted in Dulbecco's phosphate-buffered saline (DPBS) showed that 900 ng Dex loaded chitosan scaffolds in both compositions released total Dex during a 5-day period at a nearly constant rate after the initial burst. However, bFGF release from all scaffolds with both loading amounts (50 ng or 100 ng) was completed in 10 or 20 h. In order to prolong the release period of bFGF, composite scaffolds were fabricated in the presence of hydroxyapatite (HA) beads with average particle size of 40 mum. Sustained release of bFGF up to 7 days was achieved due to the electrostatic interactions between HA and bFGF molecules. These results suggested that chitosan scaffolds can be suitable for Dex release; however, the presence of HA in the chitosan scaffold is necessary to achieve the desired release period for bFGF. PMID: 19793446 [PubMed - in process] |
| A collagen sponge incorporating a hydroxyapatite/chondroitinsulfate composite as a scaffold for cartilage tissue engineering.
October 2, 2009 at 7:57 am
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| | A collagen sponge incorporating a hydroxyapatite/chondroitinsulfate composite as a scaffold for cartilage tissue engineering. J Biomater Sci Polym Ed. 2009;20(13):1861-74 Authors: Ohyabu Y, Adegawa T, Yoshioka T, Ikoma T, Shinozaki K, Uemura T, Tanaka J Because cartilage has limited potential for self-repair, tissue engineering is expected to replace the present therapies for damaged cartilage, such as total knee arthroplasty. However, scaffolds suitable for cartilage tissue engineering have not been established. We synthesized a novel porous scaffold, a collagen sponge incorporating a hydroxyapatite/chondroitinsulfate composite (pCol-HAp/ChS), containing materials which resemble extracellular matrices in bone and cartilage tissues. In this report, the physical, mechanical and biological properties of the scaffold are compared with those of a collagen sponge (pCol) and pCol incorporating a hydroxyapatite composite (pCol-HAp). HAp/ChS had smaller crystals and a larger total surface area than HAp. SEM images of the three materials showed pCol-HAp/ChS to have the roughest surface. The mechanical properties suggest that pCol-HAp/ChS and pCol/HAp are similar, and superior to pCol. Seeding experiments showed a uniform distribution of mesenchymal stem cells (MSCs) in pCol-HAp/ChS and pCol/HAp. Histochemical staining after 2 weeks of culture revealed pCol-HAp/ChS to be the most chondrogenic. From these results, pCol-HAp/ChS is expected to be a candidate for a scaffold for cartilage tissue engineering in place of collagen sponge. PMID: 19793444 [PubMed - in process] |
| Stem cell therapy for cartilage regeneration in osteoarthritis.
October 2, 2009 at 7:57 am
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| | Stem cell therapy for cartilage regeneration in osteoarthritis. Expert Opin Biol Ther. 2009 Sep 30; Authors: Koelling S, Miosge N Enhancing the regeneration potential of hyaline cartilage tissue remains a great challenge. During embryonic development, some of the cells of the inner cell mass will turn into the mesoderm. This will be the founder of the mesenchymal cells in connective tissues of adult life, such as bone, tendon, muscle, and cartilage. Some of these embryonic mesenchymal cells are believed not to differentiate, but reside in each of the tissues. These are now collectively described as adult mesenchymal stem cells, which are thought to be capable of repairing injured tissue. We will briefly summarize the current knowledge about stem cell-related cells in cartilage tissue and carefully discuss the potential of the cell population we described recently as a starting-point for a regenerative therapy for osteoarthritis. We found that repair tissue from human articular cartilage during the late stages of osteoarthritis harbors a unique progenitor cell population, termed chondrogenic progenitor cells (CPC). These exhibit stem cell characteristics combined with a high chondrogenic potential. They offer new insights into the biology of progenitor cells and may be relevant in the development of novel therapeutic approaches for a cell-based therapy for late stages of osteoarthritis. PMID: 19793003 [PubMed - as supplied by publisher] |
| Modulating the Gelation Properties of Self-Assembling Peptide Amphiphiles.
October 2, 2009 at 7:57 am
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| | Modulating the Gelation Properties of Self-Assembling Peptide Amphiphiles. ACS Nano. 2009 Sep 30; Authors: Anderson JM, Andukuri A, Lim DJ, Jun HW Peptide amphiphiles (PAs) are self-assembling molecules that form interwoven nanofiber gel networks. They have gained a lot of attention because of their excellent biocompatibility, adaptable peptide structure that allows for specific biochemical functionality, and nanofibrous assembly that mimics natural tissue formation. However, variations in molecule length, charge, and intermolecular bonding between different bioactive PAs cause contrasting mechanical properties. This potentially limits cell-delivery therapies because scaffold durability is needed to withstand the rigors of clinician handling and transport to wound implant sites. Additionally, the mechanical properties have critical influence on cellular behavior, as the elasticity and stiffness of biomaterials have been shown to affect cell spreading, migration, contraction, and differentiation. Several different PAs have been synthesized, each endowed with specific cellular adhesive ligands for directed biological response. We have investigated mechanical means for modulating and stabilizing the gelation properties of PA hydrogels in a controlled manner. A more stable, biologically inert PA (PA-S) was synthesized and combined with each of the bioactive PAs. Molar ratio (M(r) = PA/PA-S) combinations of 3:1, 1:1, and 1:3 were tested. All PA composites were characterized by observed nanostructure and rheological analysis measuring viscoelasticity. It was found that the PAs could be combined to successfully control and stabilize the gelation properties, allowing for a mechanically tunable scaffold with increased durability. Thus, the biological functionality and natural degradability of PAs can be provided in a more physiologically relevant microenvironment using our composite approach to modulate the mechanical properties, thereby improving the vast potential for cell encapsulation and other tissue engineering applications. PMID: 19791757 [PubMed - as supplied by publisher] |
| [New perspectives in medicine: stem cells]
October 2, 2009 at 7:57 am
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| | [New perspectives in medicine: stem cells] Pediatr Med Chir. 2009 May-Jun;31(3):104-16 Authors: Caramia G PMID: 19739489 [PubMed - indexed for MEDLINE] |
| Stem-cell projects falter.
October 2, 2009 at 7:57 am
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| | Stem-cell projects falter. Nature. 2009 Sep 3;461(7260):23 Authors: Dalton R PMID: 19727176 [PubMed - indexed for MEDLINE] |
| EVA-enhanced embedding medium for histological analysis of 3D porous scaffold material.
October 2, 2009 at 7:57 am
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| | EVA-enhanced embedding medium for histological analysis of 3D porous scaffold material. Micron. 2009 Oct;40(7):756-60 Authors: Lim JI, Lee YK When sectioning a 3D porous scaffold made of a soft elastomeric material embedded in paraffin medium, it is not easy to obtain a section because of the different mechanical properties of the paraffin and tissue/scaffold. We describe a new embedding material for histological analysis of various biomaterials that is composed of paraffin and ethylene vinyl acetate (EVA) resin (0, 3, 7, and 13 wt.%). 3D porous poly(L-lactide-epsilon-caprolactone) (PLCL) and chitosan scaffolds were fabricated to test the sectioning efficiency of the paraffin/EVA embedding material. The new embedding material was characterized by rheological analysis and solvent solubility testing in xylene and n-hexane. The hydrophilicity of the new material was assessed by contact angle measurement and its surface roughness was measured using AFM analysis. The staining efficiency of sections embedded in a paraffin/EVA mixture was determined by eosin staining of the chitosan scaffold and chitosan/collagen hybrid scaffold using a fluorescently labeled collagen. Section roughness decreased with increasing EVA content. The softening temperature of the paraffin/EVA mixture was similar to that of paraffin (50-60 degrees C by rheometer). The paraffin/EVA mixture dissolved completely in xylene after 30min at 50 degrees C, and after 30min in n-hexane at 60 degrees C. Therefore, the new embedding medium can be used for histological analysis of various biomaterials and natural tissues. PMID: 19473850 [PubMed - indexed for MEDLINE] |
| A closed-form structural model of planar fibrous tissue mechanics.
October 2, 2009 at 7:57 am
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| | A closed-form structural model of planar fibrous tissue mechanics. J Biomech. 2009 Jul 22;42(10):1424-8 Authors: Raghupathy R, Barocas VH Structural models of tissue mechanics, in which the tissue is represented as a sum or integral of fiber contributions for a distribution of fiber orientations, are a popular tool to represent the complex mechanical behavior of soft tissues. A significant practical challenge, however, is evaluation of the integral that defines the stress. Numerical integration is accurate but computationally demanding, posing an impediment to incorporation of structural models into large-scale finite-element simulations. In this paper, a closed-form analytic evaluation of the integral is derived for fibers distributed according to a von Mises distribution and an exponential fiber stress-strain law. PMID: 19457487 [PubMed - indexed for MEDLINE] | | | 
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