| The beauty of being a variant: H2A.Z and the SWR1 complex in plants.
February 5, 2010 at 9:08 AM
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| | The beauty of being a variant: H2A.Z and the SWR1 complex in plants. Mol Plant. 2009 Jul;2(4):565-77 Authors: March-Díaz R, Reyes JC Numerous studies have shown that the nucleosome is a dynamic structure that strongly influences gene expression. Dynamism concerns different nucleosomal characteristics, including position, posttranslational modifications, and histone composition. Thus, within the nucleosome, canonical histones can be exchanged by histone variant proteins with specific functions-a process known as 'histone replacement'. The histone variant H2A.Z has an important function in transcription and, during the last few years, its role in plant development and immune response has become evident. Compiling genetic and biochemical studies from several laboratories has revealed that plants contain a multiprotein complex, similar to the SWR1/SRCAP complex from yeast and animals, involved in H2A.Z deposition. Despite intense research in different organisms, the mechanism by which H2A.Z influences transcription is still unknown. However, recent results from Arabidopsis have shown a strong inver! se correlation between H2A.Z and DNA methylation, suggesting that H2A.Z might protect genes from silencing. PMID: 19825639 [PubMed - indexed for MEDLINE] | | |
| Repair of left ventricular aneurysm: ten-year experience in Chinese patients.
February 5, 2010 at 9:08 AM
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| | Repair of left ventricular aneurysm: ten-year experience in Chinese patients. Chin Med J (Engl). 2009 Sep 5;122(17):1963-8 Authors: Fan HG, Zheng Z, Feng W, Yuan X, Wang W, Hu SS BACKGROUND: A large transmural myocardial infarction often results in a dyskinetic or akinetic left ventricular aneurysm (LVA). This study aimed to explore the early and long-term clinical outcomes and to identify predictors for survivals and hospital re-admission after the repair of left ventricular aneurysm. METHODS: We followed up 497 patients who had undergone LVA repair from a single center in China between 1995 and 2005. The perioperative parameters were recorded. Risk factors for early mortality and long-term results were analyzed by multivariate Logistic regression. Cox's proportional hazard model was used to calculate risk factors for major adverse cardiac and cerebrovascular events, cause of death and re-admission. Kaplan-Meier curve was employed to analyze long-term survival. RESULTS: The operative mortality was 2.0%. The long-term mortality was 11.1% and cardiac causes contributed to 61.8% of the overall long-term mortality. Four hundred and thirty-two! patients survived during the follow-up period and 37.5% of them had been re-admitted at least one time. One hundred and five patients experienced major adverse cardiac and cerebrovascular events. Survival analysis exhibited that the probability of survival at 1 and 5 years after operation was 96% and 86% respectively. Previous atrial fibrillation was the independent risk factor for early mortality. Independent risk factors for long-term mortality were poor left ventricular ejection fraction and stroke,and risk factors for cardiac mortality were intraventricular block, stroke and poor left ventricular ejection fraction. Stroke, intraventricular block and advanced age were independent risk factors for major adverse cardiac and cerebrovascular events, and New York Heart Association (NYHA) class III-IV was the only risk factor for hospital re-admission. CONCLUSIONS: Postinfarction LVA can be repaired and satisfying early and long-term clinical outcome can be obtained. Endovent! ricular circular plasty technique is the better choice than li! near rep air in patients with large LVA. Survival is affected in patients with poor heart function, intraventricular block and stroke. PMID: 19781378 [PubMed - indexed for MEDLINE] | | |
| Expression patterns of FGF receptors in the developing mammalian cochlea.
February 5, 2010 at 9:08 AM
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| | Expression patterns of FGF receptors in the developing mammalian cochlea. Dev Dyn. 2010 Feb 3; Authors: Hayashi T, Ray CA, Younkins C, Bermingham-McDonogh O Many studies have shown the importance of the fibroblast growth factor (FGF) family of factors in the development of the mammalian cochlea. There are four fibroblast growth factor receptors (FGFR1-4) and all four are expressed in the cochlea during development. While there are examples in the literature of expression patterns of some of the receptors at specific stages of cochlear development there has been no systematic study. We have assembled a full analysis of the patterns of receptor expression during cochlear development for all four Fgfrs using in situ hybridization. We have analyzed the expression patterns from embryonic day 13.5 through postnatal ages. We find that Fgfr1, 2, and 3 are expressed in the epithelium of the cochlear duct and Fgfr4 is limited in its expression to the mesenchyme surrounding the duct. We compare the receptor expression pattern to markers of the sensory domain (p27(kip1)) and the early hair cells (math1). Developmental Dynamics, 2! 010. (c) 2010 Wiley-Liss, Inc. PMID: 20131355 [PubMed - as supplied by publisher] | | |
| Intracellular Na(+) and Ca(2+) modulation increases the tensile properties of developing engineered articular cartilage.
February 5, 2010 at 9:08 AM
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| | Intracellular Na(+) and Ca(2+) modulation increases the tensile properties of developing engineered articular cartilage. Arthritis Rheum. 2010 Jan 13; Authors: Natoli RM, Skaalure S, Bijlani S, Chen KX, Hu J, Athanasiou KA OBJECTIVE.: Significant collagen content and tensile properties are difficult to achieve in articular cartilage tissue engineering. This study investigated whether treating developing tissue engineered cartilage constructs with modulators of intracellular Na(+) or Ca(2+) could increase collagen concentration and tensile properties. METHODS.: Inhibitors of Na(+) ion transporters and increasers of intracellular Ca(2+) were investigated for their ability to affect articular cartilage development in a scaffold-less, 3D chondrocyte culture. Using a systematic approach, ouabain (Na(+)/K(+) ATPase inhibitor), bumetanide (Na(+)/K(+)/2Cl(-) tritransporter inhibitor), histamine (cAMP activator), and ionomycin (a Ca(2+) ionophore) were applied to tissue engineered constructs for 1 hr per day on days 10-14 of culture and examined at 2 or 4 wks. Gross morphology, biochemical content, and compressive and tensile mechanical properties of the constructs were assayed. RESULTS.: An! alysis showed that 20 muM ouabain, 0.3 muM ionomycin, or their combination increased the tensile modulus by 40-95% compared to untreated controls and resulted in increased collagen normalized to wet weight. In constructs exposed to ouabain, the increased collagen per wet weight was secondary to decreased GAG production on a per cell basis. Treatment with 20 muM ouabain also increased the neo-tissue's ultimate tensile strength 56-86% at 4 wks. Other construct properties, such as construct growth and collagen type I production, were affected differently by Na(+) modulation with ouabain versus Ca(2+) modulation with ionomycin. CONCLUSIONS.: These data are the first to show that treatments known to alter intracellular ion concentrations are a viable method for increasing the mechanical properties of engineered articular cartilage and identify potentially important relationships to hydrostatic pressure mechanotransduction. Ouabain and ionomycin may be useful pharmacological agen! ts for increasing tensile integrity and directing construct ma! turation . PMID: 20131245 [PubMed - as supplied by publisher] | | |
| Application of Recombinant Fusion Proteins for Tissue Engineering.
February 5, 2010 at 9:08 AM
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| | Application of Recombinant Fusion Proteins for Tissue Engineering. Ann Biomed Eng. 2010 Feb 4; Authors: Nagaoka M, Jiang HL, Hoshiba T, Akaike T, Cho CS Extracellular matrix (ECM) plays important roles in tissue engineering because cellular growth and differentiation, in the two-dimensional cell culture as well as in the three-dimensional space of the developing organism, require ECM with which the cells can interact. Also, the development of new synthetic ECMs is very important because ECMs facilitate the localization and delivery of cells to the specific sites in the body. Therefore, the development of synthetic ECMs to replace the natural ECMs is increasingly essential and promising in tissue engineering. Recombinant genetic engineering method has enabled the synthesis of protein-based polymers with precisely controlled functionalities for the development of new synthetic ECMs. In this review, the design and construction of structure-based recombinant fusion proteins such as elastin-like polymers (ELPs) and silk-like polymers (SLPs), cell-bound growth factor-based recombinant fusion proteins such as basic fibro! blast growth factor (bFGF) and epidermal growth factor (EGF), hybrid system composed of recombinant protein and synthetic polymer, and E-cadherin-based fusion protein by recombinant genetic engineering were explained for application of the synthetic ECMs. Modulation of mechanical properties, stimuli-sensitivity, biodegradation and cell recognition can be achieved through precise control of sequence, length, hydrophobicity and cell binding domain by recombinant genetic engineering. PMID: 20131097 [PubMed - as supplied by publisher] | | |
| Chemical Synthesis, Characterization, and Biocompatibility Study of Hydroxyapatite/Chitosan Phosphate Nanocomposite for Bone Tissue Engineering Applications.
February 5, 2010 at 9:08 AM
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| | Chemical Synthesis, Characterization, and Biocompatibility Study of Hydroxyapatite/Chitosan Phosphate Nanocomposite for Bone Tissue Engineering Applications. Int J Biomater. 2009;2009:512417 Authors: Pramanik N, Mishra D, Banerjee I, Maiti TK, Bhargava P, Pramanik P A novel bioanalogue hydroxyapatite (HAp)/chitosan phosphate (CSP) nanocomposite has been synthesized by a solution-based chemical methodology with varying HAp contents from 10 to 60% (w/w). The interfacial bonding interaction between HAp and CSP has been investigated through Fourier transform infrared absorption spectra (FTIR) and x-ray diffraction (XRD). The surface morphology of the composite and the homogeneous dispersion of nanoparticles in the polymer matrix have been investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The mechanical properties of the composite are found to be improved significantly with increase in nanoparticle contents. Cytotoxicity test using murine L929 fibroblast confirms that the nanocomposite is cytocompatible. Primary murine osteoblast cell culture study proves that the nanocomposite is osteocompatible and highly in vitro osteogenic. The use of CSP promotes the homogeneous ! distribution of particles in the polymer matrix through its pendant phosphate groups along with particle-polymer interfacial interactions. The prepared HAp/CSP nanocomposite with uniform microstructure may be used in bone tissue engineering applications. PMID: 20130797 [PubMed - as supplied by publisher] | | |
| Applications of Nanobiotechnology in Ophthalmology - Part I.
February 5, 2010 at 9:08 AM
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| | Applications of Nanobiotechnology in Ophthalmology - Part I. Ophthalmic Res. 2010 Feb 3;44(1):1-16 Authors: Nguyen P, Meyyappan M, Yiu SC Much progress has been achieved in the field of nanotechnology and its applications in ophthalmology. It is evident that drug delivery, gene therapy, implantable devices and regenerative medicine are some of the key areas of active research. To the best of our knowledge, there is limited review work on this subject area in the current literature. To assist the interested clinicians and scientists, this bipartite commentary will focus the discussion on emerging researches in nano-ophthalmology and other enabling technologies that soon may be available in the clinician's armamentarium to maintain and restore eye sight. This installment will focus on recent discoveries in drug delivery, gene therapy, imaging and visual prostheses; the second installment will discuss the impact of nanotechnology on artificial environment, cell-nanostructure interaction, other enabling nano-ophthalmic technologies, and safety and biocompatibility of nanostructures. We will take this op! portunity to introduce some exciting nano-ophthalmic applications under investigation in our laboratory. The accomplishments by the scientific community are tremendous and the future prospects are wide open. PMID: 20130441 [PubMed - as supplied by publisher] | | |
| Diabetes Induced Changes in Rat Mesenchymal Stem Cells.
February 5, 2010 at 9:08 AM
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| | Diabetes Induced Changes in Rat Mesenchymal Stem Cells. Cells Tissues Organs. 2010 Feb 3; Authors: Stolzing A, Sellers D, Llewelyn O, Scutt A Diabetes mellitus, the single most important cause of vascular disease in the industrialized world, is also associated with bone loss and impaired fracture healing. Mesenchymal stem cells (MSCs) have the potential to differentiate into osteoblasts, chondrocytes and adipocytes and other mesenchymal cells and play a central role in bone formation and repair. Because of this, we have investigated the possibility that diabetes has direct effects on MSCs in vivo and that this might represent a cellular basis for diabetes-induced osteoporosis. We isolated MSCs from rats with streptozotocin-induced diabetes and analysed them ex vivo for their ability to proliferate and differentiate in the fibroblastic colony-forming unit assay. Effects of diabetes on bone metabolism in vivo were determined by analysing tibiae from control and diabetic animals by quantitative computerized tomography. The total number of colonies and osteoblastic colonies staining positive for alkaline ph! osphatase were quantified and both colony size and number were found to be significantly reduced in diabetic rats. The changes appear to be mediated by the induction of apoptosis and senescence by advanced glycation end products (AGEs), together with an increase in the receptor for AGEs (RAGE). These changes were paralleled by extensive loss of trabecular bone in the tibiae of the diabetic animals. These data suggest that MSCs become exhausted during diabetes and lose their differentiation potential, leading to a net loss of trabecular bone. Therefore, direct effects on MSCs may be responsible for some of the orthopaedic effects associated with diabetes. PMID: 20130391 [PubMed - as supplied by publisher] | | |
| Magnetic manipulation device for the optimization of cell processing conditions.
February 5, 2010 at 9:08 AM
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| | Magnetic manipulation device for the optimization of cell processing conditions. J Biosci Bioeng. 2010 Feb;109(2):182-188 Authors: Ito H, Kato R, Ino K, Honda H Variability in human cell phenotypes make it's advancements in optimized cell processing necessary for personalized cell therapy. Here we propose a strategy of palm-top sized device to assist physically manipulating cells for optimizing cell preparations. For the design of such a device, we combined two conventional approaches: multi-well plate formatting and magnetic cell handling using magnetite cationic liposomes (MCLs). From our previous works, we showed the labeling applications of MCL on adhesive cells for various tissue engineering approaches. To feasibly transfer cells in multi-well plate, we here evaluated the magnetic response of MCL-labeled suspension type cells. The cell handling performance of Jurkat cells proved to be faster and more robust compared to MACS (Magnetic Cell Sorting) bead methods. To further confirm our strategy, prototype palm-top sized device "magnetic manipulation device (MMD)" was designed. In the device, the actual cell transportat! ion efficacy of Jurkat cells was satisfying. Moreover, as a model of the most distributed clinical cell processing, primary peripheral blood mononuclear cells (PBMCs) from different volunteers were evaluated. By MMD, individual PBMCs indicated to have optimum Interleukin-2 (IL-2) concentrations for the expansion. Such huge differences of individual cells indicated that MMD, our proposing efficient and self-contained support tool, could assist the feasible and cost-effective optimization of cell processing in clinical facilities. PMID: 20129105 [PubMed - as supplied by publisher] | | |
| Effect of Monosaccharides Composing Glycosaminoglycans on Type 2 Collagen Accumulation in a Three-Dimensional Culture of Chondrocytes.
February 5, 2010 at 9:08 AM
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| | Effect of Monosaccharides Composing Glycosaminoglycans on Type 2 Collagen Accumulation in a Three-Dimensional Culture of Chondrocytes. J Biosci Bioeng. 2010 Jan;109(1):51-54 Authors: Kagita E, Ikeda M, Wakitani S, Takagi M The effect of the addition of monosaccharides composing glycosaminoglycans (GAGs) on the accumulation of type 2 collagen (COL(II)) in a three-dimensional (3D) culture of porcine chondrocyte cells was investigated for possible application to cartilage regenerative medicine. Primary chondrocytes from porcine cartilage were cultivated in three-dimension employing atelo collagen gel for 3 weeks with the addition of several saccharides. The addition of d-glucuronic acid (d-GlcA), N-acetyl-d-galactosamine (d-GalNAc), chondroitin sulfate C (CSC), d-galactose, N-acetyl-d-glucosamine, and l-iduronic acid increased markedly not aggrecan but COL(II) accumulation although the addition of d-fructose and d-mannose not composing GAGs did not show such an effect. The addition of d-GlcA and d-GalNAc had no synergistic effect. The addition of CSC, d-GlcA, and d-GalNAc also increased COL(II) mRNA expression while aggrecan mRNA expression was not increased by these compounds. In conc! lusion, the addition of monosaccharides composing GAGs might be valuable for increasing COL(II) accumulation in the 3D culture of chondrocytes. PMID: 20129082 [PubMed - as supplied by publisher] | | |
| Characterization of microRNAs Involved in Embryonic Stem Cell States.
February 5, 2010 at 9:08 AM
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| | Characterization of microRNAs Involved in Embryonic Stem Cell States. Stem Cells Dev. 2010 Feb 3; Authors: Stadler BM, Ivanovska I, Mehta K, Song S, Nelson A, Tan Y, Mathieu J, Darby GC, Blau CA, Ware C, Peters G, Miller DG, Shen L, Cleary M, Ruohola-Baker H Studies of embryonic stem cells (ESCs) reveal that these cell lines can be derived from differing stages of embryonic development. We analyzed common changes in the expression of microRNAs (miRNAs) and mRNAs in nine different human embryonic stem cell (hESC) lines during early commitment and further examined the expression of key ESC-enriched miRNAs in earlier developmental states in several species. We show that several previously defined hESC-enriched miRNA groups (the miR-302, -17, and -515 families, and the miR-371-373 cluster) and several other hESC-enriched miRNAs are downregulated rapidly in response to differentiation. We further found that mRNAs upregulated upon differentiation are enriched in potential target sites for these hESC-enriched miRNAs. Interestingly, we also observed that the expression of ESC-enriched miRNAs bearing identical seed sequences changed dynamically while the cells transitioned through early embryonic states. In human and monkey ES! Cs, as well as human induced pluripotent stem cells (iPSCs), the miR-371-373 cluster was consistently upregulated, while the miR-302 family was mildly downregulated when the cells were chemically treated to regress to an earlier developmental state. Similarly, miR-302b, but not mmu-miR-295, was expressed at higher levels in murine epiblast stem cells (mEpiSC) as compared to an earlier developmental state, mouse ESCs. These results raise the possibility that the relative expression of related miRNAs might serve as diagnostic indicators in defining the developmental state of embryonic cells and other stem cell lines, such as iPSCs. These data also raise the possibility that miRNAs bearing identical seed sequences could have specific functions during separable stages of early embryonic development. PMID: 20128659 [PubMed - as supplied by publisher] | | |
| Diverse roles of the vasculature within the neural stem cell niche.
February 5, 2010 at 9:08 AM
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| | Diverse roles of the vasculature within the neural stem cell niche. Regen Med. 2009 Nov;4(6):879-97 Authors: Goldberg JS, Hirschi KK An interdependent relationship between the vascular and nervous systems begins during the earliest stages of development and persists through the mammalian lifespan. Accordingly, the process of adult neurogenesis involves the coordinated response of both systems to maintain a specialized microenvironment (niche) that tips the scale towards maintenance or regeneration, as needed. Understanding the nature and regulation of this balance will provide a foundation on which the potential for molecular- and stem cell-based therapies can be developed to treat prevalent CNS diseases and disorders. The vasculature is cited as a prominent feature within the adult subventricular zone and subgranular zone, known adult neural stem cell niches, helping to retain neural stem and progenitor cell potential. The vascular compartment within the neural stem cell niche has the unique opportunity to not only regulate neural stem and progenitor cells through direct contact with, and para! crine signaling from, endothelial and mural cells that make up blood vessels, but also integrates systemic signals into the local microenvironment via distribution of soluble factors from blood circulation to regulate stem cell niche behavior. Understanding the intricate role that the vasculature plays to influence neural stem cells in the context of niche regulation will help to bridge the gap from bench to bedside for the development of regeneration-based therapies for the CNS. PMID: 19903006 [PubMed - indexed for MEDLINE] | | |
| Using stem cells to mend the retina in ocular disease.
February 5, 2010 at 9:08 AM
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| | Using stem cells to mend the retina in ocular disease. Regen Med. 2009 Nov;4(6):855-64 Authors: Bull ND, Martin KR Retinal degenerative diseases are the leading cause of incurable blindness worldwide. Furthermore, existing pharmacological and surgical interventions are only partially effective in halting disease progression, thus adjunctive neuroprotective strategies are desperately needed to preserve vision. Stem cells appear to possess inherent neuroprotective abilities, at least in part by providing neurotrophic support to injured neurons. Advances in stem cell biology offer the hope of new therapies for a broad range of neurodegenerative conditions, including those of the retina. Experimental cell-mediated therapies also hint at the tantalizing possibility of achieving retinal neuronal replacement and regeneration, once cells are lost to the disease process. This article summarizes the latest advances in cell therapies for neuroprotection and regeneration in neurodegenerative pathologies of both the inner and outer retina. PMID: 19903004 [PubMed - indexed for MEDLINE] | | |
| Plasticity of stem cells derived from adult periodontal ligament.
February 5, 2010 at 9:08 AM
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| | Plasticity of stem cells derived from adult periodontal ligament. Regen Med. 2009 Nov;4(6):809-21 Authors: Huang CY, Pelaez D, Bendala JD, Garcia-Godoy F, Cheung HS BACKGROUND: The neural crest contains pluripotent cells that can give rise to neurons and glial cells of the peripheral nervous system, endocrine cells, connective tissue cells, muscle cells and pigment cells during embryonic development. Stem cells derived from the neural crest may still reside in neural crest derivatives including the periodontal ligament (PDL). However, the pluripotency of PDL-derived stem cells has not been investigated. AIM: To identify subpopulations of stem cells from the adult PDL and study their pluripotency. Human PDLs were harvested from impacted wisdom teeth (patients aged 19-22 years). RESULTS: This study demonstrated that subpopulations of PDL cells expressed embryonic stem cell markers (Oct4, Sox2, Nanog and Klf4) and a subset of neural crest markers (Nestin, Slug, p75 and Sox10). Such PDL cell subpopulations exhibited the potential to differentiate into neurogenic, cardiomyogenic, chondrogenic and osteogenic lineages. Furthermore, ! preliminary evidence suggesting insulin production of PDL cells might be indicative of the generation of cells of the endodermal lineage. CONCLUSION: These findings suggest that the PDL may contain pluripotent stem cells that originate from the neural crest. Our observations open the door to prospective autologous therapeutic applications for a variety of conditions. PMID: 19903001 [PubMed - indexed for MEDLINE] | | |
| A novel biosynthetic hybrid scaffold seeded with olfactory ensheathing cells for treatment of spinal cord injuries.
February 5, 2010 at 3:08 AM
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| | A novel biosynthetic hybrid scaffold seeded with olfactory ensheathing cells for treatment of spinal cord injuries. Chin Med J (Engl). 2009 Sep 5;122(17):2032-40 Authors: Qian LM, Zhang ZJ, Gong AH, Qin RJ, Sun XL, Cao XD, Liu JB, Jiang P, Chen YC BACKGROUND: Implantation of tissue-engineered scaffolds is one of the most promising therapeutic strategies for inducing nerve regenerations following spinal cord injuries. In this paper, we report a novel bioengineered hybrid scaffold comprised of three major extracellular matrix (ECM) proteins. METHODS: ECM-scaffolds (ECM-S) were prepared by gelling fibrinogen, fibronectin and laminin using fresh rat plasma. Olfactory ensheathing cells (OECs) were isolated from fresh rat olfactory mucosa, purified under differential adhesion, and assessed by immunofluorescent staining. OECs were seeded onto ECM-S and cultured. The effects of the scaffolds on the seeded cells were detected using the immunofluorescent staining, Western blotting, scanning electron microscopy and transmission electron microscopy. RESULTS: Tissue-engineered ECM-S could be easily molded into mat-like or cylindrical shapes and gelled by addition of fresh plasma. Observations by electron microscopy show! that the ECM-S forms a stable three-dimensional porous network. Studies on the effects of the ECM-S on the biological behaviors of OECs in vitro indicate that the scaffold can promote OEC adhesion, proliferation and process extensions. Additionally, OECs seeded on the scaffold maintained the expression of nerve growth factor, matrix metalloproteinase-3 and matrix metalloproteinase-9. CONCLUSION: We developed a biosynthetic hybrid gel which could be used as a scaffold for OEC transplantation; this gel can promote nerve regeneration following spinal cord injuries. PMID: 19781392 [PubMed - indexed for MEDLINE] | | |
| A mixture model for water uptake, degradation, erosion and drug release from polydisperse polymeric networks.
February 5, 2010 at 3:08 AM
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| | A mixture model for water uptake, degradation, erosion and drug release from polydisperse polymeric networks. Biomaterials. 2010 Feb 1; Authors: Soares JS, Zunino P We introduce a general class of mixture models suitable to describe water-dependent degradation and erosion of biodegradable polymers in conjunction with drug release. The ability to predict and quantify degradation and erosion has direct impact in a variety of biomedical applications and is a useful design tool for biodegradable implants and tissue engineering scaffolds. The model is based on a finite number of constituents describing the polydisperse polymeric system, each representing chains of an average size, and two additional constituents, water and drug. Hydrolytic degradation of individual chains occurs at the molecular level and mixture constituents diffuse individually accordingly to Fick's 1st law at the bulk level - such analysis confers a multi-scale aspect to the resulting reaction-diffusion system. A shift between two different types of behavior, each identified to surface or bulk erosion, is observed with the variation of a single non-dimensional ! parameter measuring the relative importance of the mechanisms of reaction and diffusion. Mass loss follows a sigmoid decrease in bulk eroding polymers, whereas decreases linearly in surface eroding polymers. Polydispersity influences degradation and erosion of bulk eroding polymers and drug release from unstable surface eroding matrices is dramatically enhanced in an erosion-controlled release. PMID: 20129660 [PubMed - as supplied by publisher] | | | |
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