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| Silicate, borosilicate, and borate bioactive glass scaffolds with controllable degradation rate for bone tissue engineering applications. II. In vitro and in vivo biological evaluation.
June 12, 2010 at 7:35 AM
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| | Silicate, borosilicate, and borate bioactive glass scaffolds with controllable degradation rate for bone tissue engineering applications. II. In vitro and in vivo biological evaluation. J Biomed Mater Res A. 2010 Jun 10; Authors: Fu Q, Rahaman MN, Bal BS, Bonewald LF, Kuroki K, Brown RF In Part I, the in vitro degradation of bioactive glass scaffolds with a microstructure similar to that of human trabecular bone, but with three different compositions, was investigated as a function of immersion time in a simulated body fluid. The glasses consisted of a silicate (13-93) composition, a borosilicate composition (designated 13-93B1), and a borate composition (13-93B3), in which one-third or all of the SiO(2) content of 13-93 was replaced by B(2)O(3), respectively. This work is an extension of Part I, to investigate the effect of the glass composition on the in vitro response of osteogenic MLO-A5 cells to these scaffolds, and on the ability of the scaffolds to support tissue infiltration in a rat subcutaneous implantation model. The results of assays for cell viability and alkaline phosphatase activity showed that the slower degrading silicate 13-93 and borosilicate 13-93B1 scaffolds were far better than the borate 13-93B3 scaffolds in supporting cell proliferation and function. However, all three groups of scaffolds showed the ability to support tissue infiltration in vivo after implantation for 6 weeks. The results indicate that the required bioactivity and degradation rate may be achieved by substituting an appropriate amount of SiO(2) in 13-93 glass with B(2)O(3), and that these trabecular glass scaffolds could serve as substrates for the repair and regeneration of contained bone defects. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 20540099 [PubMed - as supplied by publisher] | | |
| The mechanism of stem cell differentiation into smooth muscle cells.
June 12, 2010 at 7:35 AM
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| | The mechanism of stem cell differentiation into smooth muscle cells. Thromb Haemost. 2010 Jun 10;104(3) Authors: Xiao Q, Wang G, Luo Z, Xu Q Stem cells represent one of the most promising areas in biological and medical research. All stem cells are defined as having two basic properties: unlimited self-renewal and the broad potential to differentiate in vitro, via "progenitor cells", into somatic cells of many tissue types, in which smooth muscle cell (SMC) differentiation is a complicated and not well defined process. It is known that serum response factors (SRF) and co-activator myocardin are essential transcription factors in SMC differentiation. Upstream activators or regulators for the transcription factors have been recently identified, such as reactive oxygen species, histone deacetylases, microRNAs and extracellular matrix (ECM) proteins and integrins. In this review we, therefore, aim to briefly summarise recent progress in the mechanism of stem cell differentiation into SMCs to highlight the potential targets for promoting/inhibiting SMC differentiation useful for vessel-tissue engineering and treatment of vascular disease. PMID: 20539914 [PubMed - as supplied by publisher] | | |
| Future perspective of induced pluripotent stem cell for diagnosis, drug screening and treatment of human diseases.
June 12, 2010 at 7:35 AM
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| | Future perspective of induced pluripotent stem cell for diagnosis, drug screening and treatment of human diseases. Thromb Haemost. 2010 Jun 10;104(1) Authors: Lian Q, Chow Y, Esteban MA, Pei D, Tse HF Recent advances in stem cell biology have transformed the understanding of cell physiology and developmental biology such that it can now play a more prominent role in the clinical application of stem cell and regenerative medicine. Success in the generation of human induced pluripotent stem cells (iPS) as well as related emerging technology on the iPS platform provide great promise in the development of regenerative medicine. Human iPS cells show almost identical properties to human embryonic stem cells (ESC) in pluripotency, but avoid many of their limitations of use. In addition, investigations into reprogramming of somatic cells to pluripotent stem cells facilitate a deeper understanding of human stem cell biology. The iPS cell technology has offered a unique platform for studying the pathogenesis of human disease, pharmacological and toxicological testing, and cell-based therapy. Nevertheless, significant challenges remain to be overcome before the promise of human iPS cell technology can be realised. PMID: 20539907 [PubMed - as supplied by publisher] | | |
| Translational potential of human embryonic and induced pluripotent stem cells for myocardial repair: Insights from experimental models.
June 12, 2010 at 7:35 AM
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| | Translational potential of human embryonic and induced pluripotent stem cells for myocardial repair: Insights from experimental models. Thromb Haemost. 2010 Jun 10;104(1) Authors: Kong CW, Akar FG, Li RA Heart diseases have been a major cause of death worldwide, including developed countries. Indeed, loss of non-regenerative, terminally differentiated cardiomyocytes (CMs) due to aging or diseases is irreversible. Current therapeutic regimes are palliative in nature, and in the case of end-stage heart failure, transplantation remains the last resort. However, this option is significantly hampered by a severe shortage of donor cells and organs. Human embryonic stem cells (hESCs) can self-renew while maintaining their pluripotency to differentiate into all cell types. More recently, direct reprogramming of adult somatic cells to become pluripotent hES-like cells (a.k.a. induced pluripotent stem cells or iPSCs) has been achieved. The availability of hESCs and iPSCs, and their successful differentiation into genuine human heart cells have enabled researchers to gain novel insights into the early development of the human heart as well as to pursue the revolutionary paradigm of heart regeneration. Here we review our current knowledge of hESC-/iPSC-derived CMs in the context of two fundamental operating principles of CMs (i.e. electrophysiology and Ca2+-handling), the resultant limitations and potential solutions in relation to their translation into clinical (bioartificial pacemaker, myocardial repair) and other applications (e.g. as models for human heart disease and cardiotoxicity screening). PMID: 20539906 [PubMed - as supplied by publisher] | | |
| Cell communication and tissue engineering.
June 12, 2010 at 7:35 AM
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| | Cell communication and tissue engineering. Commun Integr Biol. 2010 Jan;3(1):53-6 Authors: Rossello RA, H D Gap junction intercellular communication (GJIC) is ubiquitous in the majority of cells and is indispensable for proper development and function of most tissues. The loss of gap junction mediated cell to cell communication leads to compromised development in many tissues and organs, and also facilitates tumorigenesis and autonomous cell behavior in cancerous cells. Because cells embedded in an extracellular matrix constantly interact through gap junctions to coordinate normal tissue functions and homeostasis, our group hypothesized that increasing cell to cell communication, via genetically engineering cells to overexpress gap junction proteins, could improve cell signaling and increase differentiation in interior regions of engineered tissue equivalents. In a recent paper,1 we presented a platform to regenerate full 3D equivalents of engineered tissue, providing a strategy to overcome a barrier in regenerative medicine. These findings suggest that both targeted delivery and cell-based strategies can be used as treatments to enhance communication in 3D living tissue.2 In this addendum, we address the effects of extracellular calcium (Ca(2+) (e)) on intracellular calcium (Ca(2+) (i)), GJIC and osteogenic differentiation under conditions in which bone marrow stromal cells (BMSCs) also exhibit higher cell-to-cell communication. As a key secondary messenger in many biological processes, the levels of Ca(2+) (e) and Ca(2+) (i) play a role in cell differentiation and may be a tunable signal in tissue regeneration. Higher cell-to-cell communication was achieved by both genetically engineering cells to overexpress connexin 43 (Cx43) and by a high density cell seeding technique, denoted micromass seeding (MM). The results presented in this addendum show that the intensity and duration of a second messenger, like calcium, can be augmented in a platform that enables higher cell-to-cell communication. The ability to modulate calcium signaling, combined with our previous approaches to modulate GJIC, may have an impact on tissue regeneration and therapies for communication incompetent cells, such as those associated with heart disease and certain types of cancer. PMID: 20539784 [PubMed - in process] | | |
| Parthenogenic blastocysts derived from cumulus-free in vitro matured human oocytes.
June 12, 2010 at 7:35 AM
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| | Parthenogenic blastocysts derived from cumulus-free in vitro matured human oocytes. PLoS One. 2010;5(6):e10979 Authors: McElroy SL, Byrne JA, Chavez SL, Behr B, Hsueh AJ, Westphal LM, Reijo Pera RA BACKGROUND: Approximately 20% of oocytes are classified as immature and discarded following intracytoplasmic sperm injection (ICSI) procedures. These oocytes are obtained from gonadotropin-stimulated patients, and are routinely removed from the cumulus cells which normally would mature the oocytes. Given the ready access to these human oocytes, they represent a potential resource for both clinical and basic science application. However culture conditions for the maturation of cumulus-free oocytes have not been optimized. We aimed to improve maturation conditions for cumulus-free oocytes via culture with ovarian paracrine/autocrine factors identified by single cell analysis. METHODOLOGY/PRINCIPAL FINDING: Immature human oocytes were matured in vitro via supplementation with ovarian paracrine/autocrine factors that were selected based on expression of ligands in the cumulus cells and their corresponding receptors in oocytes. Matured oocytes were artificially activated to assess developmental competence. Gene expression profiles of parthenotes were compared to IVF/ICSI embryos at morula and blastocyst stages. Following incubation in medium supplemented with ovarian factors (BDNF, IGF-I, estradiol, GDNF, FGF2 and leptin), a greater percentage of oocytes demonstrated nuclear maturation and subsequently, underwent parthenogenesis relative to control. Similarly, cytoplasmic maturation was also improved as indicated by development to blastocyst stage. Parthenogenic blastocysts exhibited mRNA expression profiles similar to those of blastocysts obtained after IVF/ICSI with the exception for MKLP2 and PEG1. CONCLUSIONS/SIGNIFICANCE: Human cumulus-free oocytes from hormone-stimulated cycles are capable of developing to blastocysts when cultured with ovarian factor supplementation. Our improved IVM culture conditions may be used for obtaining mature oocytes for clinical purposes and/or for derivation of embryonic stem cells following parthenogenesis or nuclear transfer. PMID: 20539753 [PubMed - in process] | | |
| Photomodulatable fluorescent proteins for imaging cell dynamics and cell fate.
June 12, 2010 at 7:35 AM
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| | Photomodulatable fluorescent proteins for imaging cell dynamics and cell fate. Organogenesis. 2009 Oct;5(4):217-26 Authors: Nowotschin S, Hadjantonakis AK An organism arises from the coordinate generation of different cell types and the stereotypical organization of these cells into tissues and organs. Even so, the dynamic behaviors, as well as the ultimate fates, of cells driving the morphogenesis of an organism, or even an individual organ, remain largely unknown. Continued innovations in optical imaging modalities, along with the discovery and evolution of improved genetically-encoded fluorescent protein reporters in combination with model organism, stem cell and tissue engineering paradigms are providing the means to investigate these unresolved questions. The emergence of fluorescent proteins whose spectral properties can be photomodulated is one of the most significant new developments in the field of cell biology where they are primarily used for studying protein dynamics in cells. Likewise, the use of photomodulatable fluorescent proteins holds great promise for use in developmental biology. Photomodulatable fluorescent proteins also represent attractive and emergent tools for studying cell dynamics in complex populations by facilitating the labeling and tracking of individual or defined groups of cells. Here, we review the currently available photomodulatable fluorescent proteins and their application in model organisms. We also discuss prospects for their use in mice, and by extension in embryonic stem cell and tissue engineering paradigms. PMID: 20539741 [PubMed - in process] | | |
| Efficient siRNA-mediated prolonged gene silencing in human amniotic fluid stem cells.
June 12, 2010 at 7:35 AM
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| | Efficient siRNA-mediated prolonged gene silencing in human amniotic fluid stem cells. Nat Protoc. 2010;5(6):1081-95 Authors: Rosner M, Siegel N, Fuchs C, Slabina N, Dolznig H, Hengstschläger M Human amniotic fluid stem cells (hAFSCs) are a very promising new type of fetal stem cells with numerous applications for basic science and cell-based therapies. They harbor a high differentiation potential and a low risk for tumor development, can be grown in large quantities and do not raise the ethical concerns associated with embryonic stem cells. RNA interference (RNAi) is a powerful technology to explain specific gene functions and has important implications for the clinical usage of tissue engineering. We provide a straightforward, 72-h-long protocol for siRNA-mediated gene silencing in hAFSCs. The lipid-based forward transfection protocol described in this article is the first RNAi approach for prolonged gene knockdown in hAFSCs. This protocol allows efficient, functional and reproducible gene knockdown in human stem cells over a prolonged period of time ( approximately 2 weeks). We also show the successful use of this protocol in primary nontransformed nonimmortalized fibroblasts, cervical adenocarcinoma cells, transformed embryonic kidney cells, immortalized endometrial stromal cells and acute monocytic leukemia cells, suggesting a wide spectrum of applications in various cell types. PMID: 20539284 [PubMed - in process] | | |
| In vitro cartilage tissue engineering using cancellous bone matrix gelatin as a biodegradable scaffold.
June 12, 2010 at 7:35 AM
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| | In vitro cartilage tissue engineering using cancellous bone matrix gelatin as a biodegradable scaffold. Biomed Mater. 2010 Jun 11;5(4):045003 Authors: Yang B, Yin Z, Cao J, Shi Z, Zhang Z, Song H, Liu F, Caterson B In this study, we constructed tissue-engineered cartilage using allogeneic cancellous bone matrix gelatin (BMG) as a scaffold. Allogeneic BMG was prepared by sequential defatting, demineralization and denaturation. Isolated rabbit chondrocytes were seeded onto allogeneic cancellous BMG, and cell-BMG constructs were harvested after 1, 3 and 6 weeks for evaluation by hematoxylin and eosin staining for overall morphology, toluidine blue for extracellular matrix (ECM) proteoglycans, immunohistochemical staining for collagen type II and a transmission electron microscope for examining cellular microstructure on BMG. The prepared BMG was highly porous with mechanical strength adjustable by duration of demineralization and was easily trimmed for tissue repair. Cancellous BMG showed favorable porosity for cell habitation and metabolism material exchange with larger pore sizes (100-500 microm) than in cortical BMG (5-15 microm), allowing cell penetration. Cancellous BMG also showed good biocompatibility, which supported chondrocyte proliferation and sustained their differentiated phenotype in culture for up to 6 weeks. Rich and evenly distributed cartilage ECM proteoglycans and collagen type II were observed around chondrocytes on the surface and inside the pores throughout the cancellous BMG. Considering the large supply of banked bone allografts and relatively convenient preparation, our study suggests that allogeneic cancellous BMG is a promising scaffold for cartilage tissue engineering. PMID: 20539056 [PubMed - as supplied by publisher] | | |
| Integration of porosity and bio-functionalization to form a 3D scaffold: cell culture studies and in vitro degradation.
June 12, 2010 at 7:35 AM
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| | Integration of porosity and bio-functionalization to form a 3D scaffold: cell culture studies and in vitro degradation. Biomed Mater. 2010 Jun 11;5(4):045001 Authors: Mittal A, Negi P, Garkhal K, Verma S, Kumar N In this study, porous poly(lactide-co-glycolide) (PLGA) (50/50) microspheres have been fabricated by the gas-foaming technique using ammonium bicarbonate as a gas-foaming agent. Microspheres of different porosities have been formulated by varying the concentration of the gas-foaming agent (0%, 5%, 10% and 15% w/v). These microspheres were characterized for particle size, porosity and average pore size, morphology, water uptake ratio and surface area and it was found that the porosity, pore size and surface area increased on increasing the concentration of the gas-foaming agent. Further, the effect of porosity on degradation behavior was evaluated over a 12 week period by measuring changes in mass, pH, molecular weight and morphology. Porosity was found to have an inverse relationship with degradation rate. To render the surface of the microspheres biomimetic, peptide P-15 was coupled to the surface of these microspheres. In vitro cell viability, proliferation and morphological evaluation were carried out on these microsphere scaffolds using MG-63 cell line to study the effect of the porosity and pore size of scaffolds and to evaluate the effect of P-15 on cell growth on porous scaffolds. MTT assay, actin, alizarin staining and SEM revealed the potential of biomimetic porous PLGA (50/50) microspheres as scaffolds for tissue engineering. As shown in graphical representation, an attempt has been made to correlate the cell behavior on the scaffolds (growth, proliferation and cell death) with the concurrent degradation of the porous microsphere scaffold as a function of time. PMID: 20539055 [PubMed - as supplied by publisher] | | |
| Production and isolation of NG2(+) oligodendrocyte precursors from human embryonic stem cells in defined serum-free medium.
June 12, 2010 at 7:35 AM
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| | Production and isolation of NG2(+) oligodendrocyte precursors from human embryonic stem cells in defined serum-free medium. Stem Cell Res. 2010 Jun 8; Authors: Sundberg M, Skottman H, Suuronen R, Narkilahti S Human embryonic stem cells (hESCs) are a promising source of oligodendrocyte precursor cells (OPCs) and oligodendrocytes. These cells can be used to repair myelin in central nervous system deficits such as multiple sclerosis or traumas such as spinal cord injury. Here, we introduce a novel differentiation method for the production of OPCs from hESCs. OPCs were differentiated as spheres in defined serum-free medium supplemented with recombinant human growth factors. A broad gene expression analysis revealed that this OPC population expressed Olig1/2, Sox10, PDGFR, Nkx2.2, Nkx6.2, oligodendrocyte-myelin glycoprotein, myelin basic protein (MBP), and proteolipid protein (PLP). According to quantitative RT-PCR analyses addition of ciliary neurotrophic factor (CNTF) upregulated the Olig2 mRNA levels in the OPC population. According to the flow cytometry analyses the OPC population was >90% NG2-positive, >80% PDGFR-positive, and >60% CD44-positive, and further matured into O4- (45%) and GalC- (80%) positive oligodendrocyte populations when cultured on top of human extracellular matrix proteins, which were used instead of Matrigel. In addition, OPCs matured into myelin-forming cells when cocultured with neuronal cells. The multilayered myelin sheet formation around axons was detected with transmission electron microscopy in cocultures. Further, the OPC populations could be purified with sorting of NG2(+) cells. These NG2(+) cells reformed spheres that remained stable during prolonged culturing (7weeks), and matured into GalC-positive oligodendrocytes. Importantly, these NG2(+) spheres were free of pluripotent Tra1-81, Oct-4, and CD326-positive hESCs. Thus, this method is suitable for the efficient production of OPCs and in the future for therapeutic graft production. PMID: 20538536 [PubMed - as supplied by publisher] | | |
| Three dimensionally flocculated proangiogenic microgels for neovascularization.
June 12, 2010 at 7:35 AM
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| | Three dimensionally flocculated proangiogenic microgels for neovascularization. Biomaterials. 2010 Jun 8; Authors: Devolder RJ, Kong HJ Microparticles encapsulating regenerative medicines have been used in tissue engineering because of their several advantages, including non-invasive drug delivery and controllable drug release rates. However, microparticles implanted in tissue defects are readily displaced by external mechanical forces, decreasing their regenerative efficacy. We hypothesized that a drug-encapsulated colloidal gel formed through colloidal attraction between microparticles would resist displacement at an implant site, and subsequently improve therapeutic efficacy. This hypothesis was examined using a colloidal gel formed from the mixing of negatively charged microgels composed of poly(ethylene glycol) (PEG) and poly(sodium acrylate), and positively charged microgels composed of PEG and poly(vinyl benzyl trimethyl ammonium chloride). The structural strength of the colloidal gel could be tuned with the zeta potential and volumetric ratios of the oppositely charged microgels. Furthermore, the implantation of the colloidal gel, encapsulating vascular endothelial growth factor, significantly increased the vascular density while limiting host inflammation, as compared with the implantation of unary microgel suspensions. This study demonstrates an enhancement in the efficacy of microparticle drug delivery systems by tuning rheological properties of suspensions, which should be useful for the design of a wide array of particulate systems for both tissue engineering and drug delivery. PMID: 20538334 [PubMed - as supplied by publisher] | | |
| Regulating orientation and phenotype of primary vascular smooth muscle cells by biodegradable films patterned with arrays of microchannels and discontinuous microwalls.
June 12, 2010 at 7:35 AM
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| | Regulating orientation and phenotype of primary vascular smooth muscle cells by biodegradable films patterned with arrays of microchannels and discontinuous microwalls. Biomaterials. 2010 Aug;31(24):6228-6238 Authors: Cao Y, Poon YF, Feng J, Rayatpisheh S, Chan V, Chan-Park MB Vascular smooth muscle cells (vSMCs) cultured in vitro are known to exhibit phenotype hyperplasticity. This plasticity is potentially very useful in tissue engineering of blood vessels. The synthetic phenotype is necessary for cell proliferation on the tissue scaffold but the cells must ultimately assume a quiescent, contractile phenotype for normal vascular function. In vitro control of vSMC phenotype has been challenging. This study shows that microchannel scaffolds with discontinuous walls can support primary vSMC proliferation and, when the cells reach confluence inside the channels, transform the cell phenotype towards greater contractility and promote cell alignment. A thorough time-resolved study was undertaken to characterize the expression of the contractile proteins alpha-actin, calponin, myosin heavy chain (MHC) and smoothelin as a function of time and initial cell density on microchannel scaffolds. The results consistently indicate that primary vSMCs cultured on the microchannel substrate substantially align parallel to the microwalls, become more elongated and significantly increase their expression of contractile proteins only when the cells reach confluence. MHC immunostaining was visible in the micropatterned cells after confluence but not in flat substrate cells or non-confluent micropatterned cells, which further verifies the increased contractility of the confluent channel-constrained vSMCs. The higher total amount of deposited elastin and collagen in confluent flat cultures than in confluent micropatterned cultures also provides confirmation of the higher contractility of the channel-constrained cells. These results establish that our microchanneled film can trigger the switch of primary vSMCs from a proliferative state to a more contractile phenotype at confluence. PMID: 20537704 [PubMed - as supplied by publisher] | | |
| myc maintains embryonic stem cell pluripotency and self-renewal.
June 12, 2010 at 7:35 AM
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| | myc maintains embryonic stem cell pluripotency and self-renewal. Differentiation. 2010 May 26; Authors: Varlakhanova NV, Cotterman RF, Devries WN, Morgan J, Donahue LR, Murray S, Knowles BB, Knoepfler PS While endogenous Myc (c-myc) and Mycn (N-myc) have been reported to be separately dispensable for murine embryonic stem cell (mESC) function, myc greatly enhances induced pluripotent stem (iPS) cell formation and overexpressed c-myc confers LIF-independence upon mESC. To address the role of myc genes in ESC and in pluripotency generally, we conditionally knocked out both c- and N-myc using myc doubly homozygously floxed mESC lines (cDKO). Both lines of myc cDKO mESC exhibited severely disrupted self-renewal, pluripotency, and survival along with enhanced differentiation. Chimeric embryos injected with DKO mESC most often completely failed to develop or in rare cases survived but with severe defects. The essential nature of myc for self-renewal and pluripotency is at least in part mediated through orchestrating pluripotency-related cell cycle and metabolic programs. This study demonstrates that endogenous myc genes are essential for mESC pluripotency and self-renewal as well as providing the first evidence that myc genes are required for early embryogenesis, suggesting potential mechanisms of myc contribution to iPS cell formation. PMID: 20537458 [PubMed - as supplied by publisher] | | |
| Improvement of Stem Cell Viability in Hyaluronic Acid Hydrogels Using Dextran Microspheres.
June 12, 2010 at 7:35 AM
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| | Improvement of Stem Cell Viability in Hyaluronic Acid Hydrogels Using Dextran Microspheres. J Biomater Sci Polym Ed. 2010 Jun 9; Authors: Kim BS, Choi JS, Kim JD, Yeo TY, Cho YW Although hyaluronic acid (HA) has been widely used in clinics as an injectable biomaterial, it may not be appropriate as an injectable stem cell carrier because highly hydrophilic HA hydrogels provide an unfavorable environment in which the encapsulated stem cells are likely to be constrained to a round shape, thereby losing their native morphology. Herein, we hypothesized that dextran microspheres (DMs) can improve stem cell viability in HA hydrogels because they can act as substrates for stem cell adhesion, spreading and proliferation. DMs with a mean diameter of 80 mum were mixed with HA hydrogels. Human adipose-derived stem cells (hASCs) were isolated from human adipose tissue and seeded into the DM-incorporated HA hydrogels. When compared with the hydrogels alone, the number of viable cells was significantly increased in the presence of the DMs. Initially, hASCs appeared to be round in the HA hydrogels. At 12 h after seeding, the hASCs apparently attached onto the DMs and became slightly flattened. One day after seeding, the hASCs seemed to spread onto the surface of the DMs. Fluorescence micrography of live and dead cells confirmed that the cell viability was significantly improved by use of the DMs in HA hydrogels. Overall results demonstrated that the microsphere/hydrogel composite supported stem cell survival and spreading. These characteristics show the potential for use of the composite in cell-delivery and tissue-engineering applications. PMID: 20537250 [PubMed - as supplied by publisher] | | |
| Fabrication and Characterization of Waterborne Biodegradable Polyurethanes 3-Dimensional Porous Scaffolds for Vascular Tissue Engineering.
June 12, 2010 at 7:35 AM
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| | Fabrication and Characterization of Waterborne Biodegradable Polyurethanes 3-Dimensional Porous Scaffolds for Vascular Tissue Engineering. J Biomater Sci Polym Ed. 2010 Jun 9; Authors: Jiang X, Yu F, Wang Z, Li J, Tan H, Ding M, Fu Q In this study, a series of 3-D interconnected porous scaffolds with various pore diameters and porosities was fabricated by freeze-drying with non-toxic biodegradable waterborne polyurethane (WBPU) emulsions of different concentration. The structures of these porous scaffolds were characterized by scanning electron microscopy (SEM), and the pore diameters were calculated using CIAS 3.0 software. The pores obtained were 3-D interconnected in the scaffolds. The scaffolds obtained at different pre-freeze temperatures showed a pore diameter ranging from 2.8 to 99.9 mum with a pre-freezing temperature of -60 degrees C and from 13.1 to 229.1 mum with a pre-freezing temperature of -25 degrees C. The scaffolds fabricated with WBPU emulsions of different concentration at the same pre-freezing temperature (-25 degrees C) had pores with mean pore diameter between 90.8 and 39.6 mum and porosity between 92.0 and 80.0%, depending on the emulsion concentration. The effect of porous structure of the scaffolds on adhesion and proliferation of human umbilical vein endothelial cells (HUVECs) cultured in vitro was evaluated using the MTT assay and environmental scanning electron microscopy (ESEM). It was found that the better adhesion and proliferation of HUVECs on 3-D scaffolds of WBPU with relative smaller pore diameter and lower porosity than those on scaffolds with larger pore and higher porosity and film. Our work suggests that fabricating a scaffold with controllable pore diameter and porosity could be a good method to be used in tissue-engineering applications to obtain carriers for cell culture in vitro. PMID: 20537246 [PubMed - as supplied by publisher] | | |
| Interleukins 4 and 13 modulate gene expression and promote proliferation of primary human tenocytes.
June 12, 2010 at 7:35 AM
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| | Interleukins 4 and 13 modulate gene expression and promote proliferation of primary human tenocytes. Fibrogenesis Tissue Repair. 2010 Jun 10;3(1):9 Authors: Courneya JP, Luzina IG, Zeller CB, Rasmussen JF, Bocharov A, Schon LC, Atamas SP ABSTRACT: BACKGROUND: Tendon disorders (tendinopathies) pose serious biomedical and socioeconomic problems. Despite diverse treatment approaches, the best treatment strategy remains unclear. Surgery remains the last resort because of the associated morbidity and inconsistent outcomes. We hypothesized that, similar to fibroblasts in various organs, tendon fibroblasts (tenocytes) might be responsive to stimulation with interleukins (ILs), particularly IL-4 and IL-13. These two cytokines share sequence homology, receptor chains and functional effects, including stimulation of fibrogenesis. It is unknown whether tenocytes are responsive to stimulation with IL-4 or IL-13. If true, local use of these cytokines might be used to facilitate tendon repair in patients with tendinopathies or used for tendon tissue-engineering approaches to facilitate tenocyte growth on scaffolds in culture. RESULTS: Tendon tissues that would normally be discarded were obtained during reconstructive surgery procedures performed for clinical indications. Primary tenocytes were derived from Achilles, posterior tibial, flexor digitorum longus and flexor hallucis longus tendon tissue samples. Reverse transcriptase quantitative PCR (RT-qPCR) experiments revealed that mRNAs for the receptor (R) chains IL-4Ralpha, IL-13Ralpha1 and IL-13Ralpha2, but not the common gamma-chain were present in all tested tendon tissues and in cultured tenocytes. Levels of IL-13R chain mRNAs were significantly higher than those of IL-4R mRNA. The cultures responded, in a dose-dependent fashion, to stimulation with recombinant human IL-4 or IL-13, by increasing proliferation rates 1.5 to 2.0-fold. The mRNA levels of 84 genes related to cell cycle regulation were measured by RT-qPCR after 6 h and 24 h of activation. The expression levels of several genes, notably CDK6 and CDKN2B changed more than twofold. In contrast to their effects on proliferation, stimulation with IL-4 or IL-13 had little if any effect on the levels of collagen mRNA or protein in cultured primary tenocytes. The mRNA levels of 84 other genes related to extracellular matrix and cell adhesion were also measured by RT-qPCR; expression of only five genes was consistently changed. CONCLUSIONS: Stimulation with IL-4 or IL-13 could be used to facilitate tendon repair in vivo or to aid in tendon tissue engineering, through stimulation of tenocyte proliferation. PMID: 20537133 [PubMed - as supplied by publisher] | | |
| Human stem cells as a model of motoneuron development and diseases.
June 12, 2010 at 7:35 AM
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| | Human stem cells as a model of motoneuron development and diseases. Ann N Y Acad Sci. 2010 Jun;1198:192-200 Authors: Liu Y, Zhang SC Human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) possess the potential to become all cell and tissue types of the human body. Under chemically defined culture systems, hESCs and hiPSCs have been efficiently directed to functional spinal motoneurons and astrocytes. The differentiation process faithfully recapitulates the developmental process predicted from studies in vertebrate animals and human specimens, suggesting the usefulness of stem cell differentiation systems in understanding human cellular development. Motoneurons and astrocytes differentiated from genetically altered hESCs or disease hiPSCs exhibit predicted phenotypes. They thus offer a simplified dynamic model for analyzing pathological processes that lead to human motoneuron degeneration, which in turn may serve as a template for pharmaceutical screening. In addition, the human stem cell-derived motoneurons and astrocytes, including those specifically derived from a patient, may become a source for cell therapy. PMID: 20536934 [PubMed - in process] | | |
| Tissue engineering of skin and cornea.
June 12, 2010 at 7:35 AM
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| | Tissue engineering of skin and cornea. Ann N Y Acad Sci. 2010 Jun;1197:166-77 Authors: Paquet C, Larouche D, Bisson F, Proulx S, Simard-Bisson C, Gaudreault M, Robitaille H, Carrier P, Martel I, Duranceau L, Auger FA, Fradette J, Guérin SL, Germain L Human beings are greatly preoccupied with the unavoidable nature of aging. While the biological processes of senescence and aging are the subjects of intense investigations, the molecular mechanisms linking aging with disease and death are yet to be elucidated. Tissue engineering offers new models to study the various processes associated with aging. Using keratin 19 as a stem cell marker, our studies have revealed that stem cells are preserved in human skin reconstructed by tissue engineering and that the number of epithelial stem cells varies according to the donor's age. As with skin, human corneas can also be engineered in vitro. Among the epithelial cells used for reconstructing skin and corneas, significant age-dependent variations in the expression of the transcription factor Sp1 were observed. Culturing skin epithelial cells with a feeder layer extended their life span in culture, likely by preventing Sp1 degradation in epithelial cells, therefore demonstrating the pivotal role played by this transcription factor in cell proliferation. Finally, using the human tissue-engineered skin as a model, we linked Hsp27 activation with skin differentiation. PMID: 20536846 [PubMed - in process] | | |
| Osteogenic Potential of Human Mesenchymal Stem Cells and Human Embryonic Stem Cell-derived Mesodermal Progenitors: a Tissue Engineering Perspective.
June 12, 2010 at 7:35 AM
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| | Osteogenic Potential of Human Mesenchymal Stem Cells and Human Embryonic Stem Cell-derived Mesodermal Progenitors: a Tissue Engineering Perspective. Tissue Eng Part A. 2010 Jun 10; Authors: de Peppo GM, Sjovall P, Lennerås M, Strehl R, Hyllner J, Thomsen P, Karlsson C Introduction. Human mesenchymal stem cells (hMSC) are promising candidates for bone engineering and regeneration with a considerable number of experimental successes reported over the last years. However, hMSCs show several limitations for tissue engineering applications, which can be overcome by using human embryonic stem cell-derived mesodermal progenitors (hES-MPs). The aim of the present study was to investigate and compare the osteogenic differentiation potential of hMSCs and hES-MPs. Materials and Methods. The osteogenic differentiation and mineralization behavior of both cell types were evaluated at passage 5, 10, 15 and 20. The expression of COL1A1, RUNX2, OPN and OC was evaluated by RT-PCR, while mineralization was examined by photospectrometry, von Kossa staining and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). The immunoprofile of both cell types was investigated by flow cytometry. Results. We demonstrated that, under proper stimulation, hES-MPs undergo osteogenic differentiation and exhibit significantly increased mineralization ability compared to hMSCs after protracted expansion. hES-MPs were also found to express lower amount of human leukocyte antigens (HLA) class II proteins. Conclusions. The high osteogenic ability of hES-MPs, together with a low expression of HLA class II, make these cells an attractive alternative for bulk production of cells for bone engineering applications. PMID: 20536357 [PubMed - as supplied by publisher] | | |
| The role of Cdx2 in Barrett's metaplasia.
June 12, 2010 at 7:35 AM
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| | The role of Cdx2 in Barrett's metaplasia. Biochem Soc Trans. 2010 Apr;38(2):364-9 Authors: Colleypriest BJ, Farrant JM, Slack JM, Tosh D Metaplasia (or transdifferentiation) is defined as the transformation of one tissue type to another. Clues to the molecular mechanisms that control the development of metaplasia are implied from knowledge of the transcription factors that specify tissue identity during normal embryonic development. Barrett's metaplasia describes the development of a columnar/intestinal phenotype in the squamous oesophageal epithelium and is the major risk factor for oesophageal adenocarcinoma. This particular type of cancer has a rapidly rising incidence and a dismal prognosis. The homoeotic transcription factor Cdx2 (Caudal-type homeobox 2) has been implicated as a master switch gene for intestine and therefore for Barrett's metaplasia. Normally, Cdx2 expression is restricted to the epithelium of the small and large intestine. Loss of Cdx2 function, or conditional deletion in the intestine, results in replacement of intestinal cells with a stratified squamous phenotype. In addition, Cdx2 is sufficient to provoke intestinal metaplasia in the stomach. In the present paper, we review the evidence for the role of Cdx2 in the development of Barrett's metaplasia. PMID: 20298184 [PubMed - indexed for MEDLINE] | | |
| Barrett's metaplasia: molecular mechanisms and nutritional influences.
June 12, 2010 at 7:35 AM
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| | Barrett's metaplasia: molecular mechanisms and nutritional influences. Biochem Soc Trans. 2010 Apr;38(2):313-9 Authors: Slack JM, Colleypriest BJ, Quinlan JM, Yu WY, Farrant MJ, Tosh D Barrett's metaplasia is discussed in the context of a general theory for the formation of metaplasias based on developmental biology. The phenotype of a particular tissue type becomes established during embryonic development by the expression of a specific set of transcription factors. If this combination becomes altered, then the tissue type can be altered. Such events may occur by mutation or by environmental effects on gene expression, normally within the stem cell population of the tissue. A macroscopic patch of metaplastic tissue will arise only if the new gene activity state is self-sustaining in the absence of its original causes, and if the new tissue type can outgrow the parent tissue type. An important candidate gene for the causation of Barrett's metaplasia is Cdx2 (Caudal-type homeobox 2). In normal development, this is expressed in the future intestine, but not the future foregut. Mouse knockout studies have shown that it is needed for intestinal development, and that its loss from adult intestine can lead to squamous transformations. It is also expressed in Barrett's metaplasia and can be activated in oesophageal cell cultures by treatment with bile acids. We have investigated the ability of Cdx2 to bring about intestinal transformations in oesophageal epithelium. Our results show that Cdx2 can activate a programme of intestinal gene expression when overexpressed in HET-1A cells, or in fetal epithelium, but not in the adult epithelium. This suggests that Cdx2, although necessary for formation of intestinal tissue, is not sufficient to provoke Barrett's metaplasia in adult life and that overexpression of additional transcription factors is necessary. In terms of diet and nutrition, there is a known association of Barrett's metaplasia with obesity. This may work through an increased risk of gastro-oesophageal reflux. Acid and bile are known to activate Cdx2 expression in oesophageal cells. It may also increase circulating levels of TNFalpha (tumour necrosis factor alpha), which activates Cdx2. In addition, there may be effects of diet on the composition of the bile. PMID: 20298175 [PubMed - indexed for MEDLINE] | | |
| Bone regeneration in sinus lifts: comparing tissue-engineered bone and iliac bone.
June 12, 2010 at 7:35 AM
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| | Bone regeneration in sinus lifts: comparing tissue-engineered bone and iliac bone. Br J Oral Maxillofac Surg. 2010 Mar;48(2):121-6 Authors: Voss P, Sauerbier S, Wiedmann-Al-Ahmad M, Zizelmann C, Stricker A, Schmelzeisen R, Gutwald R Lifting of the sinus floor is a standard procedure for bony augmentation that enables dental implantation. Although cultivated skin and mucosal grafts are often used in plastic and maxillofacial surgery, tissue-engineered bone has not achieved the same success. We present the clinical results of dental implants placed after the insertion of periosteum-derived, tissue-engineered bone grafts in sinus lifts. Periosteal cells were isolated from biopsy specimens of periosteum, resuspended and cultured. The cell suspension was soaked in polymer fleeces. The cell-polymer constructs were transplanted by sinus lift 8 weeks after harvesting. The patients (n=35) had either one or both sides operated on. Seventeen had a one-stage sinus lift with simultaneous implantation (54 implants). In 18 patients the implants were inserted 3 months after augmentation (64 implants). Selected cases were biopsied. A control group (41 patients: one stage=48 implants, two stage=135 implants) had augmentation with autologous bone only. They were followed up clinically and radiologically for at least 24 months. Both implants and augmentation were significantly more successful in the control group. Failure of augmentation of the tissue-engineered bone was more common after large areas had been augmented. Eleven implants were lost in the study group and only one in the control group. Lifting the sinus floor with autologous bone is more reliable than with tissue-engineered transplants. Although lamellar bone can be found in periosteum-derived, tissue-engineered transplants, the range of indications must be limited. PMID: 19487059 [PubMed - indexed for MEDLINE] | | | | 
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