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| Effectiveness factor and diffusion limitations in collagen gel modules containing HepG2 cells.
July 24, 2010 at 7:10 AM
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| | Effectiveness factor and diffusion limitations in collagen gel modules containing HepG2 cells. J Tissue Eng Regen Med. 2010 Jul 23; Authors: Corstorphine L, Sefton MV A major obstacle in tissue engineering is overcoming hypoxia in thick, three-dimensional (3D) engineered tissues, which is caused by the diffusional limitations of oxygen and lack of internal vasculature to facilitate mass transfer. Modular tissue engineering is a bio-mimetic strategy that forms scalable, vascularized and uniform 3D constructs by assembling small (sub-mm), cell-containing modules. It was previously assumed that mass transfer resistance within the individual modules was negligible, due to their small size. In the present study, this assumption was tested using theoretical analysis of oxygen transport within the module (effectiveness factor) and experimental studies. Small (400 microm diameter post-contraction) and large (700 microm diameter post-contraction) HepG2-collagen modules were made for a range of seeding densities (2 x 10(6)-1 x 10(7) cells/ml collagen). Cell density, distribution and morphology within the modules showed that the small modules were capable of sustaining high cell densities (8.0 x 10(7) +/- 4.4 x 10(7) cells/cm(3)) with negligible mass transfer inhibition. Conversely, large modules developed a necrotic core and had significantly (p < 0.05) reduced cell densities (1.5 x 10(7) +/- 9.2 x 10(6) cells/cm(3)). It was also observed that the embedded cells responded quickly to the oxygen availability, by proliferating or dying, to reach a sustainable density of approximately 8000 cells/module. Furthermore, a simple effectiveness factor calculation was successful in estimating the maximum cell density per module. The results gathered in this study confirm the previous assumption that the small-diameter modules avoid the internal mass transfer limitations that are often observed in larger constructs. Copyright (c) 2010 John Wiley & Sons, Ltd. PMID: 20653045 [PubMed - as supplied by publisher] | | |
| In situ functionalization of wet-spun fibre meshes for bone tissue engineering.
July 24, 2010 at 7:10 AM
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| | In situ functionalization of wet-spun fibre meshes for bone tissue engineering. J Tissue Eng Regen Med. 2010 Jul 23; Authors: Leonor IB, Rodrigues MT, Gomes ME, Reis RL Bone tissue engineering success strongly depends on our ability to develop new materials combining osteoconductive, osteoinductive and osteogenic properties. Recent studies suggest that biomaterials incorporating silanol (Si--OH) groups promote and maintain osteogenesis. The purpose of the present research work was to provide evidence that using wet-spinning technologies and a calcium silicate solution as a coagulation bath, it was possible to develop an in situ functionalization methodology to obtain 3D wet-spun fibre meshes with Si--OH groups, through a simple, economic and reliable process. SPCL (blend of starch with polycaprolactone) fibre meshes were produced by wet-spinning, using a calcium silicate solution as a non-solvent and functionalized in situ with Si--OH groups. In vitro tests, using goat bone marrow stromal cells (GBMSCs), showed that SPCL-Si scaffolds sustained cell viability and proliferation. Furthermore, high ALP activity and matrix production indicated that Si--OH groups improve cellular functionality towards the osteoblastic phenotype. Using this methodology, and assembling several wet-spun fibre meshes, 3D meshes can be developed, aiming at designing osteoconductive/osteoinductive 3D structures capable of stimulating bone ingrowth in vivo. Copyright (c) 2010 John Wiley & Sons, Ltd. PMID: 20653041 [PubMed - as supplied by publisher] | | |
| Kidney Stem/Progenitor Cells: Differentiate, Sort Out or Reprogram?
July 24, 2010 at 7:10 AM
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| | Kidney Stem/Progenitor Cells: Differentiate, Sort Out or Reprogram? Stem Cells. 2010 Jul 22; Authors: Pleniceanu O, Harari-Steinberg O, Dekel B End stage renal disease (ESRD) is defined as the inability of the kidneys to remove waste products and excess fluid from the blood. ESRD progresses from earlier stages of chronic kidney disease (CKD) and occurs when the glomerular filtration rate (GFR) is below 15 mL/min/1.73 m2. CKD and ESRD are dramatically rising due to increasing aging population, population demographics and the growing rate of diabetes and hypertension.Identification of multipotential stem/progenitor populations in mammalian tissues is important for therapeutic applications and for understanding developmental processes and tissue homeostasis. Progenitor populations are ideal targets for gene therapy, cell transplantation and tissue engineering. The demand for kidney progenitors is increasing due to severe shortage of donor organs. Because dialysis and transplantation are currently the only successful therapies for ESRD, cell therapy offers an alternative approach for kidney diseases. However, this approach may be relevant only in earlier stages of CKD, when kidney function and histology are still preserved, allowing for the integration of cells and/or for their paracrine effects, but not when small and fibrotic end-stage kidneys develop. While blood and bone marrow derived stem cells hold a therapeutic promise, they are devoid of nephrogenic potential, emphasizing the need to seek kidney stem cells beyond known extra-renal sources. Moreover, controversies regarding the existence of a true adult kidney stem cell highlight the importance of studying cell-based therapies using pluripotent cells, progenitor cells from fetal kidney or de-differentiated/reprogrammed adult kidney cells. PMID: 20652959 [PubMed - as supplied by publisher] | | |
| Chondrogenic differentiation of human mesenchymal stem cells in micro-masses is impaired by high doses of the chemokine CXCL7.
July 24, 2010 at 7:10 AM
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| | Chondrogenic differentiation of human mesenchymal stem cells in micro-masses is impaired by high doses of the chemokine CXCL7. J Tissue Eng Regen Med. 2010 Jul 22; Authors: Kalwitz G, Neumann K, Ringe J, Sezer O, Sittinger M, Endres M, Kaps C Chemokines have been shown to recruit human mesenchymal stem cells (MSCs) and are suggested to be promising candidates for in situ tissue engineering. The aim of our study was to analyse the effect of CXCL7, a chemokine that has the capacity to recruit MSCs, on the chondrogenic differentiation of MSCs. Bone marrow-derived MSCs were cultured in high-density micro-masses under serum-free conditions and were co-stimulated with 0-100 nM CXCL7 in the presence of 10 ng/ml transforming growth factor-beta3 (TGFbeta3). Micro-masses stimulated without growth factors and chemokines served as controls. Histological staining of proteoglycan, immunostaining of type II collagen, staining of mineralized matrix according to von Kossa as well as real-time gene expression analysis of typical chondrogenic and osteogenic marker genes showed that the TGFbeta3-mediated chondrogenic development of MSCs was not impaired by 0-50 nM CXCL7. Micro-masses stimulated with TGFbeta3 and CXCL7 developed chondrogenic cells and formed a cartilaginous matrix rich in proteoglycans, accompanied by the induction of typical chondrogenic marker genes, such as cartilage oligomeric matrix protein, aggrecan, type IIalpha1 collagen and by regulation of matrix metalloproteinases and their inhibitors. As assessed by histological staining, MSCs showed a significantly reduced deposition of proteoglycan and a mildly mineralized matrix when stimulated with TGFbeta3 in the presence of 100 nM CXCL7. Induction of osteogenic marker genes such as osteocalcin was not evident. These results suggest that low doses of CXCL7 do not impair the chondrogenic differentiation of bone marrow-derived stem cells and may suited for in situ cartilage tissue engineering. Copyright (c) 2010 John Wiley & Sons, Ltd. PMID: 20652876 [PubMed - as supplied by publisher] | | |
| Ceramic materials lead to underestimated DNA quantifications: a method for reliable measurements.
July 24, 2010 at 7:10 AM
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| | Ceramic materials lead to underestimated DNA quantifications: a method for reliable measurements. Eur Cell Mater. 2010;20:38-44 Authors: Piccinini E, Sadr N, Martin I In the context of investigating cell-material interactions or of material-guided generation of tissues, DNA quantification represents an elective method to precisely assess the number of cells attached or embedded within different substrates. Nonetheless, nucleic acids are known to electrostatically bind to ceramics, a class of materials commonly employed in orthopaedic implants and bone tissue engineering scaffolds. This phenomenon is expected to lead to a relevant underestimation of the DNA amount, resulting in erroneous experimental readouts. The present work aims at *lpar;i) investigating the effects of DNA-ceramic bond occurrence on DNA quantification, and (ii) developing a method to reliably extract and accurately quantify DNA in ceramic-containing specimens. A cell-free model was adopted to study DNA-ceramic binding, highlighting an evident DNA loss (up to 90%) over a wide range of DNA/ceramic ratios (w/w). A phosphate buffer-based (800mM) enzymatic extraction protocol was developed and its efficacy in terms of reliable DNA extraction and measurement was confirmed with commonly used fluorometric assays, for various ceramic substrates. The proposed buffered DNA extraction technique was validated in a cell-based experiment showing 95% DNA retrieval in a cell seeding experiment, demonstrating a 3.5-fold increase in measured DNA amount as compared to a conventional enzymatic extraction protocol. In conclusion, the proposed phosphate buffer method consistently improves the DNA extraction process assuring unbiased analysis of samples and allowing accurate and sensitive cell number quantification on ceramic containing substrates. PMID: 20652860 [PubMed - in process] | | |
| Co-culture Based Blood-brain Barrier In Vitro Model, a Tissue Engineering Approach using Immortalized Cell Lines for Drug Transport Study.
July 24, 2010 at 7:10 AM
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| | Co-culture Based Blood-brain Barrier In Vitro Model, a Tissue Engineering Approach using Immortalized Cell Lines for Drug Transport Study. Appl Biochem Biotechnol. 2010 Jul 24; Authors: Zhang Z, McGoron AJ, Crumpler ET, Li CZ This study evaluated the feasibility of using commercially available immortalized cell lines in building an in vitro blood-brain barrier (BBB) co-culture model for preliminary drug development studies. Astrocytes-derived acellular extracellular matrix (aECM) was introduced in the co-culture model to provide a novel biomimetic basement membrane for the endothelial cells to form tight junctions. Trans-Endothelial Electrical Resistance (TEER) and solute mass transport studies quantitatively evaluated the tight junction formation. Immuno-fluorescence microscopy and Western blot analysis qualitatively verified the expression of occludin, one of the tight junction proteins on the samples. Experimental data from a total of 13 experiments conclusively showed that the novel BBB in vitro co-culture model with aECM (CO + aECM) is promising in terms of establishing tight junction formation represented by TEER values, transport profiles, and tight junction protein expression when compared with traditional co-culture (CO) model setup or the endothelial cells cultured alone (EC). In vitro colorimetric sulforhodamine B (SRB) assay also revealed that the "CO + aECM" samples resulted in less cell loss on the basal sides of the insert membranes than traditional co-culture models. Our novel approach using immortalized cell lines with the addition of aECM was proven to be a feasible and repeatable alternative to the traditional BBB in vitro modeling. PMID: 20652765 [PubMed - as supplied by publisher] | | |
| Electrospun titanium dioxide nanofibers containing hydroxyapatite and silver nanoparticles as future implant materials.
July 24, 2010 at 7:10 AM
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| | Electrospun titanium dioxide nanofibers containing hydroxyapatite and silver nanoparticles as future implant materials. J Mater Sci Mater Med. 2010 Jul 22; Authors: Sheikh FA, Barakat NA, Kanjwal MA, Nirmala R, Lee JH, Kim H, Kim HY In this study, a good combination consisting of electrospun titanium dioxide (TiO(2)) nanofibers incorporated with high purity hydroxyapatite (HAp) nanoparticles (NPs) and antimicrobial silver NPs is introduced for hard tissue engineering applications. The synthesized nanofibers were characterized by various state of art techniques like; SEM, XRD, TEM, TEM EDS and XPS analyses. SEM results confirmed well oriented nanofibers and good dispersion of HAp and silver NPs, respectively. XRD results demonstrated well crystalline feature of three components used for electrospinning. Silver NPs were having a diameter in range of 5-8 nm indicated by TEM analysis. Moreover, TEM EDS analysis demonstrated the presence of each component with good dispersion over TiO(2) nanofiber. The surface analyses of nanofibers were investigated by XPS which indicated the presence of silver NPs on the surfaces of nanofibers. The obtained nanofibers were checked for antimicrobial activity by using two model organisms E. coli and S. aureus. Subsequently, antimicrobial tests have indicated that the prepared nanofibers do posses high bactericidal effect. Accordingly, these results strongly recommend the use of obtained nanofiber mats as future implant materials. PMID: 20652376 [PubMed - as supplied by publisher] | | |
| Hyperpolarization of human mesenchymal stem cells in response to magnetic force.
July 24, 2010 at 7:10 AM
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| | Hyperpolarization of human mesenchymal stem cells in response to magnetic force. IEEE Trans Nanobioscience. 2010 Mar;9(1):71-4 Authors: Kirkham GR, Elliot KJ, Keramane A, Salter DM, Dobson JP, El Haj AJ, Cartmell SH Magnetic particle tagging techniques are currently being applied to tissue engineering applications such as controlled differentiation of mesenchymal stem cells (MSC). In order to define key mechanotransducers underpinning these applications, the electrophysiological responses of human MSCs (hMSC) have been investigated. Ferromagnetic microparticles were coated with L-arginyl-glycyl-L-aspartic acid in order to target the application of dynamic force (6 pN) directly to cell surface integrins. Human MSCs demonstrated cell membrane hyperpolarization responses after the application of force, mediated by BK channels and intracellular calcium release. PMID: 20650701 [PubMed - in process] | | |
| Toward Clinical Application of Stem Cells for Cardiac Regeneration.
July 24, 2010 at 7:10 AM
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| | Toward Clinical Application of Stem Cells for Cardiac Regeneration. Heart Lung Circ. 2010 Jul 20; Authors: Stubbs SL, Crook JM, Morrison WA, Newcomb AE Heart failure affects more than 10% of the Australian population over age 65, and the ageing population will ensure continued growth of this significant problem. There are various treatment options available, but the growing field of regenerative therapy offers promise to restore or replace tissue lost in those with either congenital or acquired cardiac defects. Stem cells have many potential properties, but they need multiple discussed qualities to succeed in this field such as ease of harvest and multiplication, and most importantly minimal ethical concerns. There are multiple cell types available and one of the challenges will be to find the most appropriate cell type for cardiac regeneration. Cardiac tissue engineering is being explored using both in vitro and in vivo techniques. In vitro methods are primarily limited in terms of the vascularisation and size of the construct. In vivo engineered constructs overcome these limitations in early models, but they are still not ready for human trials. This review aims to provide the reader with an outline of the cell-based and tissue engineering therapies currently being used and developed for cardiac regeneration, as well as some insight into the potential problems that may hamper its progress in the future. PMID: 20650685 [PubMed - as supplied by publisher] | | |
| Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes.
July 24, 2010 at 7:10 AM
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| | Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes. Osteoarthritis Cartilage. 2010 Jul 19; Authors: Buckley CT, Vinardell T, Kelly DJ BACKGROUND: For current tissue engineering or regenerative medicine strategies, chondrocyte- or mesenchymal stem cell (MSC)-seeded constructs are typically cultured in normoxic conditions (20% oxygen). However, within the knee joint capsule a lower oxygen tension exists. OBJECTIVE: The objective of this study was to investigate how chondrocytes and infrapatellar fad pad derived MSCs will respond to a low oxygen (5%) environment in 3D agarose culture. Our hypothesis was that culture in a low oxygen environment (5%) will enhance the functional properties of cartilaginous tissues engineered using both cell sources. EXPERIMENTAL DESIGN: Cell-encapsulated agarose hydrogel constructs (seeded with chondrocytes or infrapatellar fat pad derived MSCs) were prepared and cultured in a chemically defined serum-free medium in the presence (chondrocytes and MSCs) or absence (chondrocytes only) of transforming growth factor-beta3 (TGF-beta3) in normoxic (20%) or low oxygen (5%) conditions for 42 days. Constructs were assessed at days 0, 21 and 42 in terms of mechanical properties, biochemical content and histologically. RESULTS: Low oxygen tension (5%) was observed to promote extracellular matrix production by chondrocytes cultured in the absence of TGF-beta3, but was inhibitory in the presence of TGF-beta3. In contrast, a low oxygen tension enhanced chondrogenesis of infrapatellar fat pad constructs in the presence of TGF-beta3, leading to superior mechanical functionality compared to chondrocytes cultured in identical conditions. CONCLUSIONS: Extrapolating the results of this study to the in vivo setting, it would appear that joint fat pad derived MSCs may possess a superior potential to generate a functional repair tissue in low oxygen tensions. However, in the context of in vitro cartilage tissue engineering, chondrocytes maintained in normoxic conditions in the presence of TGF-beta3 generate the most mechanically functional tissue. PMID: 20650328 [PubMed - as supplied by publisher] | | |
| Adipose stroma induces branching morphogenesis of engineered epithelial tubules.
July 24, 2010 at 7:10 AM
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| | Adipose stroma induces branching morphogenesis of engineered epithelial tubules. Tissue Eng Part A. 2010 Jul 22; Authors: Pavlovich A, Manivannan S, Nelson CM The mammary gland and other treelike organs develop their characteristic fractal geometries through branching morphogenesis, a process in which the epithelium bifurcates and invades into the surrounding stroma. Controlling the pattern of branching is critical for engineering these organs. In vivo, the branching process is instructed by stromal-epithelial interactions and adipocytes form the largest component of the fatty stroma that surrounds the mammary epithelium. Here, we used microlithographic approaches to engineer a three-dimensional culture model that enables analysis of the effect of adipocytes on the pattern of branching morphogenesis of mammary epithelial cells. We found that adipocyte-rich stroma induces branching through paracrine signals including hepatocyte growth factor, but does not affect the branching pattern per se. This tissue engineering approach can be expanded to other organs, and should enable piecemeal analysis of the cellular populations that control patterning during normal development. PMID: 20649458 [PubMed - as supplied by publisher] | | |
| Alignment of Astrocytes Increases Neuronal Growth in Three-Dimensional Collagen Gels and Is Maintained Following Plastic Compression to Form a Spinal Cord Repair Conduit.
July 24, 2010 at 7:10 AM
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| | Alignment of Astrocytes Increases Neuronal Growth in Three-Dimensional Collagen Gels and Is Maintained Following Plastic Compression to Form a Spinal Cord Repair Conduit. Tissue Eng Part A. 2010 Jul 22; Authors: East E, de Oliveira DB, Golding JP, Phillips JB After injury to the spinal cord, reactive astrocytes form a glial scar consisting of highly ramified cell processes that constitute a major impediment to repair, partly due to their lack of orientation and guidance for regenerating axons. In some nonmammalian vertebrates, successful central nervous system regeneration is attributed to the alignment of reactive glia, which guide axons across the lesion site. Here, a three-dimensional mammalian cell-seeded collagen gel culture system was used to explore the effect of astrocyte alignment on neuronal growth. Astrocyte alignment was mapped within tethered rectangular gels and was significantly greater at the edge and middle of the gels compared to the control unaligned regions. When neurons were seeded on and within astrocyte gels, neurite length was greatest in the areas of astrocyte alignment. There was no difference in expression of astrocyte reactivity markers between aligned and control areas. Having established the potential utility of astrocyte alignment, the aligned gels were plastic compressed, transforming them into mechanically robust implantable devices. After compression, astrocytes remained viable and aligned and supported neurite outgrowth, yielding a novel method for assembling aligned cellular constructs suitable for tissue engineering and highlighting the importance of astrocyte alignment as a possible future therapeutic intervention for spinal cord repair. PMID: 20649441 [PubMed - as supplied by publisher] | | |
| [Neural stem cells induced by neotype three-dimensional polypeptide-based self-assembled hydrogel]
July 24, 2010 at 7:10 AM
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| | [Neural stem cells induced by neotype three-dimensional polypeptide-based self-assembled hydrogel] Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2010 Jun;27(3):612-6 Authors: Song Y, Zheng Q, Guo X The amphiphilic polypeptide (PA) was self-assembled into three-dimensional (3-D) porous complex of hydrogel and cells with the addition of NSCs-containing DMEM/F12. Cell differentiation in the surface and that within hydrogel were described. Cells harvested from the cerebral cortex of neonatal mice were triturated and cultivated in serum-free media. 1wt% PA was added into same volume of DMEM/F12 with cell concentration of 1 x 10(5)/ml and self-supported into 3-D hydrogel-cell composition; cells suspended within hydrogel being maintained (Experiment group, EG). lwt% PA was self-assembled into two-dimensional (2-D) hydrogel films triggered by addition of DMEM/F12, and then 1 x 10(5)/ml NSCs was seeded in the surface of films (Control group, CG). Cells in EG and CG were incubated in serum-free media for two weeks and stained with immunocytochemistry methods. TEM showed that the hydrogel derived from PA was composed of network nanofibers with their diameter ranging from 3 to 5 nm and length ranging from 100 nm to 1. 5 microm. Above 50% of cells obtained were Nestin positive cells. LSCM observations demonstrated that above 90% of cells survived two days after incubation within hydrogel, and were differentiated into NF and GFAP positive cells one week after incubation, their differentiation rates were 50% +/- 4.2% and 20% +/- 2.8% respectively; however, cells in CG were also differentiated into NF and GFAP positive cells, their differentiation rates were only 40% +/- 3.4% and 31% +/- 2.3% separately. Peptide-based hydrogel was able to provide 3-D environments for cell survival and induce primarily the differentiation of NSCs into neurons. Our data indicated that peptide-directed self-assembly of hydrogels was useful and it served as the neotype nerve tissue engineering scaffolds. PMID: 20649030 [PubMed - in process] | | |
| Special segment: soft tissue matrices--Bilayered bioengineered skin substitute to augment wound healing.
July 24, 2010 at 7:10 AM
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| | Special segment: soft tissue matrices--Bilayered bioengineered skin substitute to augment wound healing. Foot Ankle Spec. 2009 Dec;2(6):303-5 Authors: DeCarbo WT Wounds that fail standard wound care for more than 4 weeks are often very difficult to heal. Several factors including senescent cells, an inflammatory wound environment, unavailable growth factors, and the presence of bacteria inhibit chronic wounds from healing. Bioengineered tissue, such as Apligraf (Organogenesis Inc, Canton, Massachusetts), has been shown to be both safe and effective in decreasing healing time and increasing the incidence of complete wound closure. The science and technology behind bioengineered tissue has altered the way chronic wounds are treated. PMID: 20400431 [PubMed - indexed for MEDLINE] | | |
| Special segment: soft tissue matrices--Apligraf bilayered skin substitute to augment healing of chronic wounds in diabetic patients.
July 24, 2010 at 7:10 AM
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| | Special segment: soft tissue matrices--Apligraf bilayered skin substitute to augment healing of chronic wounds in diabetic patients. Foot Ankle Spec. 2009 Dec;2(6):299-302 Authors: DeCarbo WT Chronic wounds are wounds that fail to heal or fail to progress to healing within an appropriate time frame. Standard wound care consists of debridement of all nonviable tissue, off-loading, and maintaining a moist environment, typically with saline-moistened gauze. Infection control, blood flow, and nutrition also play pivotal roles in wound healing. Bioengineered tissue, Apligraf, has been shown to be both efficacious and safe when used in chronic wounds. Apligraf delivers growth factors and cytokines to the wound environment to help complete closure and decrease healing time. PMID: 20400430 [PubMed - indexed for MEDLINE] | | |
| A tissue-engineered approach towards retinal repair: scaffolds for cell transplantation to the subretinal space.
July 24, 2010 at 7:10 AM
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| | A tissue-engineered approach towards retinal repair: scaffolds for cell transplantation to the subretinal space. Graefes Arch Clin Exp Ophthalmol. 2010 Jun;248(6):763-78 Authors: Hynes SR, Lavik EB BACKGROUND: Several mechanisms of retina degeneration result in the deterioration of the outer retina and can lead to blindness. Currently, with the exception of anti-angiogenic treatments for wet age-related macular degeneration, there are no treatments that can restore lost vision. There is evidence that photoreceptors and embryonic retinal tissue, transplanted to the subretinal space, can form new synapses with surviving host neurons. However, these transplants have yet to result in a clinical treatment for retinal degeneration. METHODS: This article reviews the current literature on the transplantation of scaffolds with retinal and retinal pigmented epithelial (RPE) cells to the subretinal space. We discuss the types of cells and materials that have been investigated for transplantation to the subretinal space, summarize the current findings, and present opportunities for future research and the next generation of scaffolds for retinal repair. RESULTS: Challenges to cell transplantation include limited survival upon implantation and the formation of abnormal cell architectures in vivo. Scaffolds have been shown to enhance cell survival and direct cell differentiation and organization in a number of models of retinal degeneration. CONCLUSIONS: The transplantation of cells within a scaffold represents a possible treatment to repair retinal degeneration and restore vision in effected patients. Materials have been developed for the delivery of retinal and RPE cells separately however, the development of a combined tissue-engineered scaffold targeting both cell populations represents a promising direction for retinal repair. PMID: 20169358 [PubMed - indexed for MEDLINE] | | |
| Novel ceramic bone replacement material CeraBall seeded with human mesenchymal stem cells.
July 24, 2010 at 7:10 AM
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| | Novel ceramic bone replacement material CeraBall seeded with human mesenchymal stem cells. Clin Oral Implants Res. 2010 Mar;21(3):262-7 Authors: Douglas T, Liu Q, Humpe A, Wiltfang J, Sivananthan S, Warnke PH OBJECTIVES: Hydroxyapatite (HA) and tricalcium phosphate (TCP) are two very common ceramic materials for bone replacement. A recently developed material for bone replacement is CeraBall, which is a mixed HA-TCP scaffold available as porous spherical scaffolds of diameter 4 and 6 mm. Before their use as bone replacement materials in vivo, in vitro testing of these scaffolds is necessary. The goal of this study was to characterise 4 and 6 mm CeraBall scaffolds in vitro with a view to their future use as bone replacement materials. MATERIALS AND METHODS: The proliferation of human mesenchymal stromal cells (hMSCs) seeded on CeraBall scaffolds was evaluated quantitatively using the WST [Water soluble tetrazolium ((4-[3-(4- Iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1, 3-benzene disulfonate)] test and qualitatively by scanning electron microscopy (SEM). In addition, the standard MTT [(3-(4, 5-Dimenthylthiazol-2-Y1)-2, 5-Diphenyltetrazolium bromide)] biocompatibility test and cell vitality staining were performed using hMSCs. CeraBall scaffolds were also tested for their mechanical properties. RESULTS: SEM and WST test results showed that hMSCs proliferated on CeraBall scaffolds over the course of 9 days. Proliferation was similar to that seen on tissue culture polystyrene (control). Cells showed a well-spread morphology and formed 'sheets' on the surface of scaffolds. Invasion of pores was observed. Good biocompatibility was demonstrated by MTT test results and cell vitality staining. Scaffolds of both 4 and 6 mm were able to withstand compressive loads of 5 N. CONCLUSIONS: CeraBall scaffolds show good biocompatibility in vitro for hMSCs. This opens the way for in vivo applications. PMID: 19958377 [PubMed - indexed for MEDLINE] | | |
| Scaffold modeling application in the repair of skull defects.
July 24, 2010 at 7:10 AM
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| | Scaffold modeling application in the repair of skull defects. Artif Organs. 2010 Apr;34(4):339-42 Authors: Wan W, Shi P The repair of large segmental bone defects caused by trauma, inflammation, and surgery on tumors pose a major clinical challenge. Tissue-engineered bone is emerging as a good choice for prefabricating cellular scaffold, and computer-aided technologies and medical imaging have created new possibilities in biomedical engineering. An accurate and efficient construction of anatomic models is critical to the application of these computational methods. Such models must be validated prior to application. In this article, we explore the potential of combining these techniques to scaffold and repair a pediatric skull. Working under the hypothesis that the autogenously cultivated osteoblasts can be grown on individualized scaffolds to improve bone regeneration in skull defects, we focus our study on potential problems concerning the segmentation, reconstruction, and mesh simplification for a pediatric skull. We also propose a new framework to improve the accuracy of the model entity from image segmentation to mesh simplification. PMID: 19663864 [PubMed - indexed for MEDLINE] | | |
| Current-Controlled Electrical Point-Source Stimulation of Embryonic Stem Cells.
July 24, 2010 at 6:36 AM
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| | Current-Controlled Electrical Point-Source Stimulation of Embryonic Stem Cells. Cell Mol Bioeng. 2009 Dec;2(4):625-635 Authors: Chen MQ, Xie X, Wilson KD, Sun N, Wu JC, Giovangrandi L, Kovacs GT Stem cell therapy is emerging as a promising clinical approach for myocardial repair. However, the interactions between the graft and host, resulting in inconsistent levels of integration, remain largely unknown. In particular, the influence of electrical activity of the surrounding host tissue on graft differentiation and integration is poorly understood. In order to study this influence under controlled conditions, an in vitro system was developed. Electrical pacing of differentiating murine embryonic stem (ES) cells was performed at physiologically relevant levels through direct contact with microelectrodes, simulating the local activation resulting from contact with surrounding electroactive tissue. Cells stimulated with a charged balanced voltage-controlled current source for up to 4 days were analyzed for cardiac and ES cell gene expression using real-time PCR, immunofluorescent imaging, and genome microarray analysis. Results varied between ES cells from three progressive differentiation stages and stimulation amplitudes (nine conditions), indicating a high sensitivity to electrical pacing. Conditions that maximally encouraged cardiomyocyte differentiation were found with Day 7 EBs stimulated at 30 microA. The resulting gene expression included a sixfold increase in troponin-T and a twofold increase in beta-MHCwithout increasing ES cell proliferation marker Nanog. Subsequent genome microarray analysis revealed broad transcriptome changes after pacing. Concurrent to upregulation of mature gene programs including cardiovascular, neurological, and musculoskeletal systems is the apparent downregulation of important self-renewal and pluripotency genes. Overall, a robust system capable of long-term stimulation of ES cells is demonstrated, and specific conditions are outlined that most encourage cardiomyocyte differentiation. PMID: 20652088 [PubMed - as supplied by publisher] | | |
| Renal imino acid and glycine transport system ontogeny and involvement in developmental iminoglycinuria.
July 24, 2010 at 6:36 AM
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| | Renal imino acid and glycine transport system ontogeny and involvement in developmental iminoglycinuria. Biochem J. 2010;428(3):397-407 Authors: Vanslambrouck JM, Bröer A, Thavyogarajah T, Holst J, Bailey CG, Bröer S, Rasko JE Renal maturation occurs post-natally in many species and reabsorption capacity at birth can vary substantially from the mature kidney. However, little is known regarding the maturation of amino acid transport mechanisms, despite the well-known physiological state of developmental iminoglycinuria. Commonly seen during early infancy, developmental iminoglycinuria is a transient version of the persistent inherited form of the disorder, referred to as iminoglycinuria, and manifests as a urinary hyperexcretion of proline, hydroxyproline and glycine. The transporters involved in developmental iminoglycinuria and their involvement in the improvement of renal reabsorption capacity remain unknown. qPCR (quantitative real-time PCR) and Western blot analysis in developing mouse kidney revealed that the expression of Slc6a18, Slc6a19, Slc6a20a and Slc36a2 was lower at birth (approx. 3.4-, 5.0-, 2.4- and 3.0-fold less than adult kidney by qPCR respectively) and increased during development. Furthermore, immunofluorescence confocal microscopy demonstrated the absence of apical expression of Slc6a18, Slc6a19, Slc6a20a and the auxiliary protein collectrin in kidneys of mice at birth. This correlated with the detection of iminoglycinuria during the first week of life. Iminoglycinuria subsided (proline reduction preceded glycine) in the second week of life, which correlated with an increase in the expression of Slc6a19 and Slc6a20a. Mice achieved an adult imino acid and glycine excretion profile by the fourth week, at which time the expression level of all transporters was comparable with adult mice. In conclusion, these results demonstrate the delayed expression and maturation of Slc6a18, Slc6a19, Slc6a20a and Slc36a2 in neonatal mice and thus the molecular mechanism of developmental iminoglycinuria. PMID: 20377526 [PubMed - indexed for MEDLINE] | | |
| In situ functionalization of wet-spun fibre meshes for bone tissue engineering.
July 24, 2010 at 6:31 AM
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| | In situ functionalization of wet-spun fibre meshes for bone tissue engineering. J Tissue Eng Regen Med. 2010 Jul 23; Authors: Leonor IB, Rodrigues MT, Gomes ME, Reis RL Bone tissue engineering success strongly depends on our ability to develop new materials combining osteoconductive, osteoinductive and osteogenic properties. Recent studies suggest that biomaterials incorporating silanol (Si--OH) groups promote and maintain osteogenesis. The purpose of the present research work was to provide evidence that using wet-spinning technologies and a calcium silicate solution as a coagulation bath, it was possible to develop an in situ functionalization methodology to obtain 3D wet-spun fibre meshes with Si--OH groups, through a simple, economic and reliable process. SPCL (blend of starch with polycaprolactone) fibre meshes were produced by wet-spinning, using a calcium silicate solution as a non-solvent and functionalized in situ with Si--OH groups. In vitro tests, using goat bone marrow stromal cells (GBMSCs), showed that SPCL-Si scaffolds sustained cell viability and proliferation. Furthermore, high ALP activity and matrix production indicated that Si--OH groups improve cellular functionality towards the osteoblastic phenotype. Using this methodology, and assembling several wet-spun fibre meshes, 3D meshes can be developed, aiming at designing osteoconductive/osteoinductive 3D structures capable of stimulating bone ingrowth in vivo. Copyright (c) 2010 John Wiley & Sons, Ltd. PMID: 20653041 [PubMed - as supplied by publisher] | | |
| c-myc and N-myc promote active stem cell metabolism and cycling as architects of the developing brain.
July 24, 2010 at 6:31 AM
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| | c-myc and N-myc promote active stem cell metabolism and cycling as architects of the developing brain. Oncotarget. 2010 Jun;1(2):120-130 Authors: Wey A, Knoepfler PS myc genes are associated with a wide variety of human cancers including most types of nervous system tumors. While the mechanisms by which myc overexpression causes tumorigenesis are multifaceted and have yet to be clearly elucidated, they are at least in part related to endogenous myc function in normal cells. Knockout (KO) of either c-myc or N-myc genes in neural stem and precursor cells (NSC) driven by nestin-cre impairs mouse brain growth and mutation of N-myc also causes microcephaly in humans in Feingold Syndrome. To further define myc function in NSC and nervous system development, we created a double KO (DKO) for c- and N-myc using nestin-cre. The DKO mice display profoundly impaired overall brain growth associated with decreased cell cycling and migration of NSC, which are strikingly decreased in number. The DKO brain also exhibits specific changes in gene expression including downregulation of genes involved in protein and nucleotide metabolism, mitosis, and chromatin structure as well as upregulation of genes associated with differentiation. Together these data support a model of nervous system tumorigenesis in which excess myc aberrantly locks in a developmentally active chromatin state characterized by overactive cell cycling, and metabolism as well as blocked differentiation. PMID: 20651942 [PubMed - as supplied by publisher] | | |
| A gain-of-function mutation in Ptpn11 (Shp-2) phosphatase induces myeloproliferative disease by aberrant activation of hematopoietic stem cells.
July 24, 2010 at 6:31 AM
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| | A gain-of-function mutation in Ptpn11 (Shp-2) phosphatase induces myeloproliferative disease by aberrant activation of hematopoietic stem cells. Blood. 2010 Jul 22; Authors: Xu D, Wang S, Yu WM, Chan G, Araki T, Bunting KD, Neel BG, Qu CK Germline and somatic gain-of-function mutations in tyrosine phosphatase Ptpn11 (Shp-2) are associated with juvenile myelomonocytic leukemia (JMML), a myeloproliferative disease (MPD) of early childhood. The mechanism by which Ptpn11 mutations induce this disease is not fully understood. Signaling partners that mediate the pathogenic effects of Ptpn11 mutations have not been explored. Here we report that germline mutation Ptpn11(D61G) in mice aberrantly accelerates hematopoietic stem cell (HSC) cycling, increases the stem cell pool, and elevates short-term and long-term repopulating capabilities, leading to the development of MPD. MPD is reproduced in primary and secondary recipient mice transplanted with Ptpn11(D61G/+) whole bone marrow cells or purified Lineage(-)Sca-1(+)c-Kit(+) cells, but not lineage committed progenitors. The deleterious effects of Ptpn11(D61G) mutation on HSCs are attributable to enhancing cytokine/growth factor signaling. The aberrant HSC activities caused by Ptpn11(D61G) mutation are largely corrected by deletion of Gab2, a prominent interacting protein and target of Shp-2 in cell signaling. As a result, MPD phenotypes are markedly ameliorated in Ptpn11(D61G/+)/Gab2(-/-) double mutant mice. Collectively, our data suggest that oncogenic Ptpn11 induces MPD by aberrant activation of HSCs. This study also identifies Gab2 as an important mediator for the pathogenic effects of Ptpn11 mutations. PMID: 20651068 [PubMed - as supplied by publisher] | | |
| Centromere Protein A dynamics in human pluripotent stem cell self renewal, differentiation and DNA damage.
July 24, 2010 at 6:31 AM
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| | Centromere Protein A dynamics in human pluripotent stem cell self renewal, differentiation and DNA damage. Hum Mol Genet. 2010 Jul 22; Authors: Ambartsumyan G, Gill RK, Perez SD, Conway D, Vincent J, Dalal Y, Clark AT Human pluripotent stem cells (hPSCs) hold significant promise for use in regenerative medicine, or as a model to understand human embryo development. However the basic mechanisms required for proliferation and self-renewal of hPSCs have not been fully uncovered. Proliferation in all eukaryotes is dependent upon highly regulated expression of the histone H3 variant Centromere Protein A (CENP-A). In the current study we demonstrate that hPSCs have a unique mRNA reserve of CENP-A not found in somatic fibroblasts. Using shRNA technology to reduce but not ablate CENP-A, we show that CENP-A depleted hPSCs are still capable of maintaining a functional centromeric mark whereas fibroblasts are not. However, upon induction of differentiation or DNA damage, hPSCs with depleted CENP-A arrest in G2/M and undergo apoptosis. Analysis of CENP-A dynamics following DNA damage in hPSCs reveals that 60 minutes after irradiation CENP-A is found in multiple small nuclear foci that are mutually exclusive to gammaH2AX as well as CENP-C. Furthermore, following irradiation, hPSCs with depleted CENP-A mount a normal apoptotic response at 6 hours, however at 24 hours, apoptosis is significantly increased in CENP-A depleted hPSCs relative to control. Taken together, our results indicate that hPSCs exhibit a unique mechanism for maintaining genomic integrity by possessing the flexibility to reduce the amount of CENP-A required to maintain a functional centromere under self-renewing conditions, and maintaining a reserve of CENP-A mRNA to re-build the centromere following differentiation or DNA damage. PMID: 20650959 [PubMed - as supplied by publisher] | | |
| Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes.
July 24, 2010 at 6:31 AM
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| | Oxygen tension differentially regulates the functional properties of cartilaginous tissues engineered from infrapatellar fat pad derived MSCs and articular chondrocytes. Osteoarthritis Cartilage. 2010 Jul 19; Authors: Buckley CT, Vinardell T, Kelly DJ BACKGROUND: For current tissue engineering or regenerative medicine strategies, chondrocyte- or mesenchymal stem cell (MSC)-seeded constructs are typically cultured in normoxic conditions (20% oxygen). However, within the knee joint capsule a lower oxygen tension exists. OBJECTIVE: The objective of this study was to investigate how chondrocytes and infrapatellar fad pad derived MSCs will respond to a low oxygen (5%) environment in 3D agarose culture. Our hypothesis was that culture in a low oxygen environment (5%) will enhance the functional properties of cartilaginous tissues engineered using both cell sources. EXPERIMENTAL DESIGN: Cell-encapsulated agarose hydrogel constructs (seeded with chondrocytes or infrapatellar fat pad derived MSCs) were prepared and cultured in a chemically defined serum-free medium in the presence (chondrocytes and MSCs) or absence (chondrocytes only) of transforming growth factor-beta3 (TGF-beta3) in normoxic (20%) or low oxygen (5%) conditions for 42 days. Constructs were assessed at days 0, 21 and 42 in terms of mechanical properties, biochemical content and histologically. RESULTS: Low oxygen tension (5%) was observed to promote extracellular matrix production by chondrocytes cultured in the absence of TGF-beta3, but was inhibitory in the presence of TGF-beta3. In contrast, a low oxygen tension enhanced chondrogenesis of infrapatellar fat pad constructs in the presence of TGF-beta3, leading to superior mechanical functionality compared to chondrocytes cultured in identical conditions. CONCLUSIONS: Extrapolating the results of this study to the in vivo setting, it would appear that joint fat pad derived MSCs may possess a superior potential to generate a functional repair tissue in low oxygen tensions. However, in the context of in vitro cartilage tissue engineering, chondrocytes maintained in normoxic conditions in the presence of TGF-beta3 generate the most mechanically functional tissue. PMID: 20650328 [PubMed - as supplied by publisher] | | |
| Mesenchymal Stem Cells and Osteoarthritis: Remedy or Accomplice?
July 24, 2010 at 6:31 AM
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| | Mesenchymal Stem Cells and Osteoarthritis: Remedy or Accomplice? Hum Gene Ther. 2010 Jul 22; Authors: Coleman C, Curtin C, Barry F, Murphy M Multipotent mesenchymal stromal or stem cells (MSCs) are likely to be agents of connective tissue homeostasis and repair. Since the hallmark of osteoarthritis (OA) is degeneration and failure to repair connective tissues it is compelling to think that these cells have a role to play in OA. Indeed, MSCs have been implicated in the pathogenesis of OA and, in turn, progression of the disease has been shown to be therapeutically modulated by MSCs. This review discusses current knowledge on the potential of both marrow and local joint-derived MSCs in OA, the mode of action of the cells and possible effects of the osteoarthritic niche on the function of MSCs. The use of stem cells for repair of isolated cartilage lesions and strategies for modulation of OA using local cell delivery are discussed as well as therapeutic options for the future to recruit and appropriately activate endogenous progenitors and/or locally systemically administered MSCs in the early stages of the disease. The use of gene therapy protocols, particularly as they pertain to modulation of inflammation associated with the osteoarthritic niche, offer an additional option in treatment of this chronic disease. In summary, elucidation of the etiology of OA and development of technologies to detect early disease, allied to an increased understanding of the role MSCs in ageing and OA, should lead to more targeted and efficacious treatments for this debilitating chronic disease in the future. PMID: 20649459 [PubMed - as supplied by publisher] | | |
| Geometric control of human stem cell morphology and differentiation.
July 24, 2010 at 6:13 AM
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| | Geometric control of human stem cell morphology and differentiation. Integr Biol (Camb). 2010 Jul 22; Authors: Wan LQ, Kang SM, Eng G, Grayson WL, Lu XL, Huo B, Gimble J, Guo XE, Mow VC, Vunjak-Novakovic G During tissue morphogenesis, stem cells and progenitor cells migrate, proliferate, and differentiate, with striking changes in cell shape, size, and acting mechanical stresses. The local cellular function depends on the spatial distribution of cytokines as well as local mechanical microenvironments in which the cells reside. In this study, we controlled the organization of human adipose derived stem cells using micro-patterning technologies, to investigate the influence of multi-cellular form on spatial distribution of cellular function at an early stage of cell differentiation. The underlying role of cytoskeletal tension was probed through drug treatment. Our results show that the cultivation of stem cells on geometric patterns resulted in pattern- and position-specific cell morphology, proliferation and differentiation. The highest cell proliferation occurred in the regions with large, spreading cells (such as the outer edge of a ring and the short edges of rectangles). In contrast, stem cell differentiation co-localized with the regions containing small, elongated cells (such as the inner edge of a ring and the regions next to the short edges of rectangles). The application of drugs that inhibit the formation of actomyosin resulted in the lack of geometrically specific differentiation patterns. This study confirms the role of substrate geometry on stem cell differentiation, through associated physical forces, and provides a simple and controllable system for studying biophysical regulation of cell function. PMID: 20652175 [PubMed - as supplied by publisher] | | | | 
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