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| Hemangioblastic Derivatives from Human Induced Pluripotent Stem Cells Exhibit Limited Expansion and Early Senescence.
February 16, 2010 at 6:34 AM
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| | Hemangioblastic Derivatives from Human Induced Pluripotent Stem Cells Exhibit Limited Expansion and Early Senescence. Stem Cells. 2010 Feb 12; Authors: Feng Q, Lu SJ, Klimanskaya I, Gomes I, Kim D, Chung Y, Honig GR, Kim KS, Lanza R Human induced pluripotent stem cells (hiPSC) have been shown to differentiate into a variety of replacement cell types. Detailed evaluation and comparison to their human embryonic stem cell (hESC) counterparts is critical for assessment of their therapeutic potential. Using established methods, we demonstrate here that hiPSCs are capable of generating hemangioblasts/blast cells (BCs), endothelial cells and hematopoietic cells with phenotypic and morphological characteristics similar to those derived from hESCs, but with a dramatic decreased efficiency. Furthermore, in distinct contrast to the hESC derivatives, functional differences were observed in BCs derived from hiPSCs, including significantly increased apoptosis, severely limited growth and expansion capability, as well as a substantially decreased hematopoietic colony forming capability. After further differentiation into erythroid cells, >1000-fold difference in expansion capability was observed in hiPSC! -BCs versus hESC-BCs. Although endothelial cells derived from hiPSCs were capable of taking up acetylated low-density-lipoprotein and forming capillary-vascular like structures on Matrigel, these cells also demonstrated early cellular senescence (the majority of endothelial cells senesced after one passage). Similarly, retinal pigmented epithelium cells derived from hiPSCs began senescing in the first passage. Before clinical application, it will be necessary to determine the cause and extent of such abnormalities, and whether they also occur in hiPSCs generated using different reprogramming methods. PMID: 20155819 [PubMed - as supplied by publisher] | | |
| The preparation and cytocompatibility of injectable thermosensitive chitosan/poly(vinyl alcohol) hydrogel.
February 16, 2010 at 6:34 AM
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| | The preparation and cytocompatibility of injectable thermosensitive chitosan/poly(vinyl alcohol) hydrogel. J Huazhong Univ Sci Technolog Med Sci. 2010 Feb;30(1):89-93 Authors: Qi B, Yu A, Zhu S, Chen B, Li Y In order to investigate the strength, structure and cell cytocompatibility of injectable thermosensitive chitosan (CS)/poly(vinyl alcohol) (PVA) composite hydrogel, chitosan hydrochloride solution was transferred to a neutral pH and mixed with different proportions of PVA, then the gelation time and strength of these different hydrogels were tested and spatial structures were observed under a scanning electron microscopy (SEM) after freeze-drying. The cytocompatibility of the hydrogels was evaluated through cytotoxicity test and three-dimensional culture with bone marrow mesenchymal stem cells. The results showed that the CS/PVA solution kept in liquid state at low temperature (0-4 degrees C) and turned into transparent elastomer about 15-20 min at 37 degrees C. Gelation time was prolonged, the strength increased and porous structure became dense with the PVA content increased in the mixed hydrogel. The cytotoxicity grades of these gels were from 0 to 1. Rabbit bo! ne marrow mesenchymal stem cells could survive and proliferate in the gel within 3 weeks, and the gel had good cytocompatibility. It was concluded that thermosensitive CS/PVA composite hydrogel not only has interpenetrating network structure and better mechanical strength, but also has good cytocompatibility, and may be used as an injectable scaffold for tissue engineering. PMID: 20155462 [PubMed - as supplied by publisher] | | |
| Cell encapsulation using biopolymer gels for regenerative medicine.
February 16, 2010 at 6:34 AM
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| | Cell encapsulation using biopolymer gels for regenerative medicine. Biotechnol Lett. 2010 Feb 13; Authors: Hunt NC, Grover LM There has been a consistent increase in the mean life expectancy of the population of the developed world over the past century. Healthy life expectancy, however, has not increased concurrently. As a result we are living a larger proportion of our lives in poor health and there is a growing demand for the replacement of diseased and damaged tissues. While traditionally tissue grafts have functioned well for this purpose, the demand for tissue grafts now exceeds the supply. For this reason, research in regenerative medicine is rapidly expanding to cope with this new demand. There is now a trend towards supplying cells with a material in order to expedite the tissue healing process. Hydrogel encapsulation provides cells with a three dimensional environment similar to that experienced in vivo and therefore may allow the maintenance of normal cellular function in order to produce tissues similar to those found in the body. In this review we discuss biopolymeric gels t! hat have been used for the encapsulation of mammalian cells for tissue engineering applications as well as a brief overview of cell encapsulation for therapeutic protein production. This review focuses on agarose, alginate, collagen, fibrin, hyaluronic acid and gelatin since they are widely used for cell encapsulation. The literature on the regeneration of cartilage, bone, ligament, tendon, skin, blood vessels and neural tissues using these materials has been summarised. PMID: 20155383 [PubMed - as supplied by publisher] | | |
| Artificial organs: recent progress in metals and ceramics.
February 16, 2010 at 6:34 AM
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| | Artificial organs: recent progress in metals and ceramics. J Artif Organs. 2010 Feb 13; Authors: Nomura N The superior properties and novel functions of biomaterials, including metals and ceramics commonly used as implants and medical devices, have been the focus of a number of recent papers. New functions have been explored in metastable beta-Ti alloys, Ni-free Co-Cr-Mo alloys, Mg alloys, and other materials. In addition, porous metals and ceramics with sophisticated structures have been studied as scaffolds for regenerative medicine. In this review, recent advances in bioceramics, metallic biomaterials, and their composites are discussed in terms of their material properties and morphology. PMID: 20155294 [PubMed - as supplied by publisher] | | |
| Haematopoietic stem cells derive directly from aortic endothelium during development.
February 16, 2010 at 6:34 AM
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| | Haematopoietic stem cells derive directly from aortic endothelium during development. Nature. 2010 Feb 14; Authors: Bertrand JY, Chi NC, Santoso B, Teng S, Stainier DY, Traver D A major goal of regenerative medicine is to instruct formation of multipotent, tissue-specific stem cells from induced pluripotent stem cells (iPSCs) for cell replacement therapies. Generation of haematopoietic stem cells (HSCs) from iPSCs or embryonic stem cells (ESCs) is not currently possible, however, necessitating a better understanding of how HSCs normally arise during embryonic development. We previously showed that haematopoiesis occurs through four distinct waves during zebrafish development, with HSCs arising in the final wave in close association with the dorsal aorta. Recent reports have suggested that murine HSCs derive from haemogenic endothelial cells (ECs) lining the aortic floor. Additional in vitro studies have similarly indicated that the haematopoietic progeny of ESCs arise through intermediates with endothelial potential. Here we have used the unique strengths of the zebrafish embryo to image directly the generation of HSCs from the ventral wa! ll of the dorsal aorta. Using combinations of fluorescent reporter transgenes, confocal time-lapse microscopy and flow cytometry, we have identified and isolated the stepwise intermediates as aortic haemogenic endothelium transitions to nascent HSCs. Finally, using a permanent lineage tracing strategy, we demonstrate that the HSCs generated from haemogenic endothelium are the lineal founders of the adult haematopoietic system. PMID: 20154733 [PubMed - as supplied by publisher] | | |
| Antibiotic-releasing porous polymethylmethacrylate constructs for osseous space maintenance and infection control.
February 16, 2010 at 6:34 AM
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| | Antibiotic-releasing porous polymethylmethacrylate constructs for osseous space maintenance and infection control. Biomaterials. 2010 Feb 12; Authors: Shi M, Kretlow JD, Nguyen A, Young S, Scott Baggett L, Wong ME, Kurtis Kasper F, Mikos AG The use of a strategy involving space maintenance as the initial step of a two-stage regenerative medicine approach toward reconstructing significant bony or composite tissue defects in the craniofacial area, preserves the void volume of bony defects and could promote soft tissue healing prior to the subsequent definitive repair. One of the complications with a biomaterial-based space maintenance approach is local infection, which requires early, effective eradication, ideally through local antibiotic delivery. The purpose of this study is to develop a dual function implant material for maintaining osseous space and releasing an antibiotic to eliminate local infection in bony defects. Colistin, a polymyxin antibiotic, was chosen specifically to address infections with Acinetobacter species, the most common pathogen associated with combat-related traumatic craniofacial injuries. Porous polymethylmethacrylate (PMMA) constructs incorporating poly(lactic-co-glycolic a! cid) (PLGA) microspheres were fabricated by mixing a clinically used bone cement formulation of PMMA powder and methylmethacrylate liquid with a carboxymethylcellulose (CMC) hydrogel (40 or 50 wt%) to impart porosity and PLGA microspheres (10 or 15wt%) loaded with colistin to control drug release. The PMMA/CMC/PLGA construct featured mild setting temperature, controllable surface/bulk porosity by incorporation of the CMC hydrogel, reasonably strong compressive properties, and continuous drug release over a period of 5 weeks with total drug release of 68.1-88.3%, depending on the weight percentage of CMC and PLGA incorporation. The concentration of released colistin was well above its reported minimum inhibitory concentration against susceptible species for 5 weeks. This study provides information on the composition parameters that enable viable porosity characteristics/drug release kinetics of the PMMA/CMC/PLGA construct for the initial space maintenance as part of a two-st! age regenerative medicine approach. PMID: 20153893 [PubMed - as supplied by publisher] | | |
| Cell-mediated BMP-2 liberation promotes bone formation in a mechanically unstable implant environment.
February 16, 2010 at 6:34 AM
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| | Cell-mediated BMP-2 liberation promotes bone formation in a mechanically unstable implant environment. Bone. 2010 Feb 11; Authors: Hägi TT, Wu G, Liu Y, Hunziker EB The flexible alloplastic materials that are used in bone-reconstruction surgery lack the mechanical stability that is necessary for sustained bone formation, even if this process is promoted by the application of an osteogenic agent, such as BMP-2. We hypothesize that if BMP-2 is delivered gradually, in a cell-mediated manner, to the surgical site, then the scaffolding material's lack of mechanical stability becomes a matter of indifference. Flexible discs of Ethisorb were functionalized with BMP-2, which was either adsorbed directly onto the material (rapid release kinetics) or incorporated into a calcium-phosphate coating (slow release kinetics). Unstabilized and titanium-plate-stabilized samples were implanted subcutaneously in rats and retrieved up to 14days later for a histomorphometric analysis of bone and cartilage volumes. On day 14, the bone volume associated with titanium-plate-stabilized discs bearing an adsorbed depot of BMP-2 was 10-fold higher than t! hat associated with their mechanically unstabilized counterparts. The bone volume associated with discs bearing a coating-incorporated depot of BMP-2 was similar in the mechanically unstabilized and titanium-plate-stabilized groups, and comparable to that associated with the titanium-plate-stabilized discs bearing an adsorbed depot of BMP-2. Hence, if an osteogenic agent is delivered in a cell-mediated manner (via coating degradation), ossification can be promoted even within a mechanically unstable environment. PMID: 20153849 [PubMed - as supplied by publisher] | | |
| Potent in vitro chondrogenesis of CD105 enriched human adipose-derived stem cells.
February 16, 2010 at 6:34 AM
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| | Potent in vitro chondrogenesis of CD105 enriched human adipose-derived stem cells. Biomaterials. 2010 Feb 11; Authors: Jiang T, Liu W, Lv X, Sun H, Zhang L, Liu Y, Zhang WJ, Cao Y, Zhou G Adipose-derived stem cells (ASCs) are considered as a promising cell source for cartilage regeneration. However, the heterogeneity of this cell source may affect their ability in cartilage formation. It is therefore necessary to establish an efficient method for isolating the cells that have chondrogenic potential. To date, no specific markers have been reported to be able to isolate such a cell population from human adipose tissue. In recent studies, endoglin (CD105) has been known as a relatively specific marker for identifying mesenchymal stem cells, but no studies show it is related to chondrogenic potential of human ASCs. In this study, human cells from adipose tissue were isolated, cultured, and sorted according to CD105 expression. The sorted cells were then subjected to adipogenic, osteogenic, and chondrogenic induction to confirm their multi-potentiality. In adipogenic conditions, CD105- cells showed stronger Oil Red staining and higher expression of adip! ose-specific genes compared to CD105+ cells. By contrast, CD105+ cells exhibited better osteogenic potential with stronger Alizarin Red staining and higher expression of osteogenic specific genes than CD105- cells. Noticeably, CD105+ cells also exhibited a much stronger chondrogenic potential than CD105- cells, with stronger collagen II staining and higher gene expression of collagen II and aggrecan. Most importantly, CD105+ cells could form a homogeneous cartilage-like tissue when seeded into a biodegradable scaffold and cultured in chondrogenic media for 8 weeks. These results indicate that sorting of ASC subpopulation with CD105 as a marker may allow better in vitro chondrogenesis and thus provide an important implications for cartilage regeneration and reconstruction using autologous cells from adipose tissue. PMID: 20153525 [PubMed - as supplied by publisher] | | |
| The enhanced characteristics of osteoblast adhesion to photofunctionalized nanoscale TiO(2) layers on biomaterials surfaces.
February 16, 2010 at 6:34 AM
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| | The enhanced characteristics of osteoblast adhesion to photofunctionalized nanoscale TiO(2) layers on biomaterials surfaces. Biomaterials. 2010 Feb 11; Authors: Miyauchi T, Yamada M, Yamamoto A, Iwasa F, Suzawa T, Kamijo R, Baba K, Ogawa T Recently, UV photofunctionalization of titanium has been shown to be effective in enhancing osteogenic environment around this functional surface, in particular for the use of endosseous implants. However, the underlying mechanism remains unknown and its potential application to other tissue engineering materials has never been explored. We determined whether adhesion of a single osteoblast is enhanced on UV-treated nano-thin TiO(2) layer with virtually no surface roughness or topographical features. Rat bone marrow-derived osteoblasts were cultured on UV-treated or untreated 200-nm thick TiO(2) sputter-coated glass plates. After an incubation of 3 h, the mean critical shear force required to initiate detachment of a single osteoblast was determined to be 1280 +/- 430 nN on UV-treated TiO(2) surfaces, which was 2.5-fold greater than the force required on untreated TiO(2) surfaces. The total energy required to complete the detachment was 37.0 +/- 23.2 pJ on UV-trea! ted surfaces, 3.5-fold greater than that required on untreated surfaces. Such substantial increases in single cell adhesion were also observed for osteoblasts cultured for 24 h. Osteoblasts on UV-treated TiO(2) surfaces were larger and characterized with increased levels of vinculin expression and focal contact formation. However, the density of vinculin or focal contact was not influenced by UV treatment. In contrast, both total expression and density of actin fibers increased on UV-treated surfaces. Thin layer TiO(2) coating and UV treatment of Co-Cr alloy and PTFE membrane synergistically resulted in a significant increase in the ability of cell attachment and osteoblastic production of alkaline phosphatase. These results indicated that the adhesive nature of a single osteoblast is substantially enhanced on UV-treated TiO(2) surfaces, providing the first evidence showing that each individual cell attached to these surfaces is substantially more resistant to exogenous loa! d potentially from blood and fluid flow and mechanical force i! n the in itial stage of in vivo biological environment. This enhanced osteoblast adhesion was supported synergistically but disproportionately by enhancement in focal adhesion and cytoskeletal developments. Also, this study demonstrated that UV treatment is effective on nano-thin TiO(2) depositioned onto non-Ti materials to enhance their bioactivity, providing a basis for TiO(2)-mediated photofunctionalization of biomaterials, a new method of developing functional biomaterials. PMID: 20153521 [PubMed - as supplied by publisher] | | |
| An cell-assembly derived physiological 3D model of the metabolic syndrome, based on adipose-derived stromal cells and a gelatin/alginate/fibrinogen matrix.
February 16, 2010 at 6:34 AM
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| | An cell-assembly derived physiological 3D model of the metabolic syndrome, based on adipose-derived stromal cells and a gelatin/alginate/fibrinogen matrix. Biomaterials. 2010 Feb 11; Authors: Xu M, Wang X, Yan Y, Yao R, Ge Y One of the major obstacles in drug discovery is the lack of in vitro three-dimensional (3D) models that can capture more complex features of a disease.Here we established a in vitro physiological model of the metabolic syndrome (MS) using cell-assembly technique (CAT), which can assemble cells into designated places to form complex 3D structures. Adipose-derived stromal (ADS) cells were assembled with gelatin/alginate/fibrinogen. Fibrin was employed as an effective material to regulate ADS cell differentiation and self-organization along with other methods. ADS cells differentiated into adipocytes and endothelial cells, meanwhile, the cells were induced to self-organize into an analogous tissue structure. Pancreatic islets were then deposited at designated locations and constituted the adipoinsular axis with adipocytes. Analysis of the factors involved in energy metabolism showed that this system could capture more pathological features of MS. Drugs known to have ! effects on MS showed accordant effects in this system, indicating that the model has potential in MS drug discovery. Overall, this study demonstrated that cell differentiation and self-organization can be regulated by techniques combined with CAT. The model presented could result in a better understanding of the pathogenesis of MS and the development of new technologies for drug discovery. PMID: 20153520 [PubMed - as supplied by publisher] | | |
| Scaffold-free cell delivery for use in regenerative medicine.
February 16, 2010 at 6:34 AM
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| | Scaffold-free cell delivery for use in regenerative medicine. Adv Drug Deliv Rev. 2010 Feb 10; Authors: Kelm JM, Fussenegger M The development of cell-based therapies for diseased tissues is one of the most promising research directions in regenerative medicine. Cell-delivery methods are an essential part of cell therapy concepts. Therapies with the potential to become clinical routine will only be possible if these methods ensure efficient engraftment and therapeutically-relevant numbers of cells survive. Here we provide an overview of three different scaffold-free cell delivery concepts: (i) single cell delivery, (ii) cell sheet engineering and (iii) microtissue technology. PMID: 20153387 [PubMed - as supplied by publisher] | | |
| Fibrin-mediated lentivirus gene transfer: Implications for lentivirus microarrays.
February 16, 2010 at 6:34 AM
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| | Fibrin-mediated lentivirus gene transfer: Implications for lentivirus microarrays. J Control Release. 2010 Feb 10; Authors: Raut S, Lei P, Padmashali R, Andreadis ST We employed fibrin hydrogel as bioactive matrix for lentivirus mediated gene transfer. Fibrin-mediated gene transfer was highly efficient and exhibited strong dependence on fibrinogen concentration. Efficient gene transfer was achieved with fibrinogen concentration between 3.75 - 7.5mg/mL. Lower fibrinogen concentrations resulted in diffusion of virus out of the gel while higher concentrations led to ineffective fibrin degradation by target cells. Addition of fibrinolytic inhibitors decreased gene transfer in a dose-dependent manner suggesting that fibrin degradation by target cells may be necessary for successful gene delivery. Under these conditions transduction may be limited only to cells interacting with the matrix thereby providing a method for spatially localized gene delivery. Indeed, when lentivirus-containing fibrin microgels were spotted in an array format gene transfer was confined to virus-containing fibrin spots with minimal cross-contamination betwe! en neighboring sites. Collectively, our data suggest that fibrin may provide an effective matrix for spatially-localized gene delivery with potential applications in high-throughput lentiviral microarrays and in regenerative medicine. PMID: 20153386 [PubMed - as supplied by publisher] | | |
| Stem Cell Therapy in PAD.
February 16, 2010 at 6:34 AM
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| | Stem Cell Therapy in PAD. Eur J Vasc Endovasc Surg. 2010 Feb 10; Authors: Sprengers RW, Moll FL, Verhaar MC Critical limb ischemia (CLI) continues to form a substantial burden on Western health care. Despite recent advances in surgical and radiological vascular techniques, a large number of patients is not eligible for these revascularisation procedures and faces amputation as their ultimate treatment option. Growth factor therapy and stem cell therapy - both therapies focussing on augmenting postnatal neovascularisation - have raised much interest in the past decade. Based on initial pre-clinical and clinical results, both therapies appear to be promising strategies to augment neovascularisation and to reduce symptoms and possibly prevent amputation in CLI patients. However, the underlying mechanisms of postnatal neovascularisation are still incompletely understood. Both fundamental research as well as large randomised trials are needed for further optimisation of these treatment options, and will hopefully lead to needed advances in the treatment of no-option CLI pati! ents in the near future. PMID: 20153223 [PubMed - as supplied by publisher] | | |
| Long-term survival and characterisation of human umbilical cord-derived mesenchymal stem cells on dermal equivalents.
February 16, 2010 at 6:34 AM
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| | Long-term survival and characterisation of human umbilical cord-derived mesenchymal stem cells on dermal equivalents. Differentiation. 2010 Feb 10; Authors: Schneider RK, Püllen A, Kramann R, Bornemann J, Knüchel R, Neuss S, Perez-Bouza A During early embryogenesis, mesenchymal cells arise from the primitive epithelium and can revert to an epithelial phenotype by passing through mesenchymal-to-epithelial transition (MET). Mesenchymal stem cells (MSC) of the Wharton's Jelly of the umbilical cord (UC-MSC) express pluripotency markers underlining their primitive developmental state. As mesenchymal stem cells from bone marrow (BM-MSC) possess a strong propensity to ameliorate mesenchymal tissue damage, UC-MSC might also be able to differentiate into cells apart from the mesoderm, allowing replacement of ectodermal and mesodermal tissues. In this study, we analysed the possible epidermal differentiation of UC-MSC on dermal equivalents (DEs) consisting of collagen I/III with dermal fibroblasts and subjected to the culture conditions for tissue engineering of skin with keratinocytes. The culture conditions were further modified by pre-treating the cells with 5-azacytidine or by supplementing the medium wi! th all trans retinoic acid. Interestingly, a subpopulation of UC-MSC (29%) co-expressed pan-cytokeratin (epithelial marker; pan-CK) and vimentin (mesenchymal marker) after isolation. Under the three-dimensional conditions of skin, the number of pan-CK(+)-cells increased to >30% after 21 days of cultivation, while under osteogenic culture conditions the cells were pan-CK-negative, thus showing the influence of the artificial niche. Nevertheless, the pan-CK-expression was neither accompanied by typical epithelial morphology nor expression of other epidermal markers. The pan-CK-detection can be explained by the expression of cytokeratins in myofibroblasts. UC-MSC expressed alpha-smooth muscle actin after isolation and displayed all features of functional myofibroblasts like morphology, cell-mediated contraction of a collagen gel and production of components of the extracellular matrix (ECM). The treatment with all trans retinoic acid or 5-azacytidine could neither induce an! epidermal differentiation nor enhance the myofibroblastic dif! ferentia tion. Concluding, UC-MSC might be an interesting cell source to support the regeneration of wounds by their differentiation into myofibroblasts and their extensive synthesis of ECM components. PMID: 20153102 [PubMed - as supplied by publisher] | | |
| Heparin-based hydrogel as a matrix for encapsulation and cultivation of primary hepatocytes.
February 16, 2010 at 6:34 AM
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| | Heparin-based hydrogel as a matrix for encapsulation and cultivation of primary hepatocytes. Biomaterials. 2010 Feb 10; Authors: Kim M, Lee JY, Jones CN, Revzin A, Tae G Primary hepatocytes are commonly used as liver surrogates in toxicology and tissue engineering fields, therefore, maintenance of functional hepatocytes in vitro is an important topic of investigation. This paper sought to characterize heparin-based hydrogel as a three-dimensional scaffold for hepatocyte culture. The primary rat hepatocytes were mixed with a prepolymer solution comprised of thiolated heparin and acrylated poly(ethylene glycol) (PEG). Raising the temperature from 25 degrees to 37 degrees C initiated Michael addition reaction between the thiol and acrylated moieties and resulted in formation of hydrogel with entrapped cells. Analysis of liver-specific products, albumin and urea, revealed that the heparin hydrogel was non-cytotoxic to cells and, in fact, promoted hepatic function. Hepatocytes entrapped in the heparin-based hydrogel maintained high levels of albumin and urea synthesis after three weeks in culture. Because heparin is known to bind growt! h factors, we incorporated hepatocyte growth factor (HGF)-an important liver signaling molecule - into the hydrogel. HGF release from heparin hydrogel matrix was analyzed using enzyme linked immunoassay (ELISA) and was shown to occur in a controlled manner with only 40% of GF molecules released after 30 days in culture. Importantly, hepatocytes cultured within HGF-containing hydrogels exhibited significantly higher levels of albumin and urea synthesis compared to cells cultured in the hydrogel alone. Overall, heparin-based hydrogel showed to be a promising matrix for encapsulation and maintenance of difficult-to-culture primary hepatocytes. In the future, we envision employing heparin-based hyrogels as matrices for in vitro differentiation of hepatocytes or stem cells and as vehicles for transplantation of these cells. PMID: 20153045 [PubMed - as supplied by publisher] | | |
| An elastomeric patch derived from poly(glycerol sebacate) for delivery of embryonic stem cells to the heart.
February 16, 2010 at 6:34 AM
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| | An elastomeric patch derived from poly(glycerol sebacate) for delivery of embryonic stem cells to the heart. Biomaterials. 2010 Feb 10; Authors: Chen QZ, Ishii H, Thouas GA, Lyon AR, Wright JS, Blaker JJ, Chrzanowski W, Boccaccini AR, Ali NN, Knowles JC, Harding SE We hypothesize that a combinatorial approach of ventricle constraint and stem cell therapy would offer a greater benefit for the treatment of heart failure than either strategy alone. A heart patch would serve two therapeutic purposes: biomechanical support and cell delivery. In this study, we describe a hybrid heart patch engineered from a synthetic elastomer, poly(glycerol sebacate) (PGS), supplemented with cardiomyocytes differentiated from human embryonic stem cells (hESCs). In line with two therapeutically relevant considerations, i.e. biocompatibility and cell delivery efficiency, the PGS was (a) pre-conditioned in culture medium for 6 days, and (b) prepared without gelatin coatings to facilitate detachment and delivery of cardiomyocytes following patch implantation. Following pre-conditioning under physiological conditions, the PGS patch material without gelatin coating was found to satisfactorily support cardiomyocyte viability and attachment, with active ! cell beating for periods of longer than 3 months until interrupted. Dynamic culture studies revealed that cells detached more efficiently from the uncoated surface of PGS than from gelatin-coated PGS. No significant differences were detected between the beating rates of human embryonic stem cell-derived cardiomyocytes on tissue culture plate and the pre-conditioned and gelatin-uncoated PGS. PGS patches sutured over the left ventricle of rats in vivo remained intact over a 2 week period without any deleterious effects on ventricular function. We conclude that PGS is a suitable biomaterial for stem cell-based regeneration strategies to restore cardiomyocyte function, and the hybrid heart patch engineered under optimal conditions would be a promising support device for the cardiac repair. PMID: 20153041 [PubMed - as supplied by publisher] | | |
| Ex vivo culturing of stromal cells with dexamethasone-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles promotes ectopic bone formation.
February 16, 2010 at 6:34 AM
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| | Ex vivo culturing of stromal cells with dexamethasone-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles promotes ectopic bone formation. Bone. 2010 Feb 9; Authors: Oliveira JM, Kotobuki N, Tadokoro M, Hirose M, Mano JF, Reis RL, Ohgushi H Recently, our group has proposed a combinatorial strategy in tissue engineering principles employing carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles (CMCht/PAMAM) towards the intracellular release and regimented supply of dexamethasone (Dex) aimed at control stem cells osteogenic differentiation in the absence of typical osteogenic inducers, in vivo. In this work, we have investigated if the Dex-loaded CMCht/PAMAM dendrimer nanoparticles could play a crucial role in the regulation of osteogenesis, in vivo. Macroporous hydroxyapatite (HA) scaffolds were seeded with rat bone marrow stromal cells (RBMSCs), whose cells were expanded in MEM medium supplemented with 0.01mg.ml(-1) Dex-loaded CMCht/PAMAM dendrimer nanoparticles and implanted subcutaneously on the back of rats for 2 and 4weeks. HA porous ceramics without RBMSCs and RBMSCs/HA scaffold constructs seeded with cells expanded in the presence and absence of 10(-8)M Dex were used as controls. The e! ffect of initial cell number seeded in the HA scaffolds on the bone-forming ability of the constructs was also investigated. Qualitative and quantitative new bone formation was evaluated in a non-destructive manner using micro-computed tomography analyses of the explants. Haematoxylin & Eosin stained implant sections were also used for the histomorphometrical analysis. Toluidine blue staining was carried out to investigate the synthesis of proteoglycan extracellular matrix. In addition, alkaline phosphatase and osteocalcin levels in the explants were also quantified, since these markers denote osteogenic differentiation. At four-weeks post-implantation results have shown that the novel Dex-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles may be beneficial as intracellular nanocarrier, supplying Dex in a regimented manner and promoting superior ectopic de novo bone formation. PMID: 20152952 [PubMed - as supplied by publisher] | | |
| Hydrogel/calcium phosphate composites for three-dimensional culture of human bone mesenchymal cells require specific properties.
February 16, 2010 at 6:34 AM
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| | Hydrogel/calcium phosphate composites for three-dimensional culture of human bone mesenchymal cells require specific properties. Acta Biomater. 2010 Feb 9; Authors: Sohier J, Corre P, Weiss P, Layrolle P To provide multipotent cells with a three-dimensional environment closer to bone matrix, an engineered construct mimicking bone components have been designed and evaluated. A biocompatible hydrogel (silated hydroxypropylmethyl cellulose) was used as extra cellular matrix while biphasic calcium phosphate ceramic particles were used to replace mineralized matrix. Finally, human bone mesenchymal cells were cultured in three-dimension in the resulting constructs to study their cell viability, proliferation, interactions within the composites, and maintenance of their osteogenic potential. This approach resulted in homogeneous structures in which cells were viable and retained their osteoblastic differentiation potential. However, the cells did not proliferate nor colonize the constructs, possibly because of a lack of suitable interactions with their microenvironment. PMID: 20152947 [PubMed - as supplied by publisher] | | |
| Sol-gel silica based biomaterials and bone tissue regeneration.
February 16, 2010 at 6:34 AM
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| | Sol-gel silica based biomaterials and bone tissue regeneration. Acta Biomater. 2010 Feb 9; Authors: Arcos D, Vallet-Regí M The impact of bone diseases and trauma in developed and developing countries have importantly increased in the last decades. Bioactive glasses, especially those silica based materials, are called to play a fundamental role in this field due to their osteoconductive, osteoproductive and osteoinductive properties. In the last years, sol-gel processes and supramolecular chemistry of surfactants have been incorporated to the bioceramics field, allowing controlling the porosity of bioglasses at the nanometric scale. This advance has promoted a new generation of sol-gel bioactive glasses with applications as drug delivery systems, as well as regenerative grafts with improved bioactive behavior. Besides, the combination of silica based glasses with organic components led to new organic-inorganic hybrid materials with improved mechanical properties. Finally, an effort has been made to organize at the macroscopic level the sol-gel glass preparation. This effort has resulte! d in new 3D macroporous scaffolds, suitable to be used in tissue engineering techniques or as porous pieces to be implanted in situ. This review collects the most important advances in the field of silica glasses occurred in the last decade, which are called to play a lead role in the future of bone regenerative therapies. PMID: 20152946 [PubMed - as supplied by publisher] | | |
| The essential requirement for Runx1 in development of the sternum.
February 16, 2010 at 6:34 AM
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| | The essential requirement for Runx1 in development of the sternum. Dev Biol. 2010 Feb 9; Authors: Liakhovitskaia A, Lana-Elola E, Stamateris E, Rice DP, van 't Hof RJ, Medvinsky A Runx1 is highly expressed in chondro- and osteo-progenitor cells and in vitro experiments suggest that Runx1 is important in early stages of osteoblast and chondrocyte differentiation. However, as Runx1 knockout mice are early embryonic lethal due to failure of haematopoiesis, the role of Runx1 in skeletogenesis remains unclear. We studied the role of Runx1 in skeletal development using a Runx1 reversible knockout mouse model. By crossing with Tie2-Cre deletor mice, Runx1 expression was selectively rescued in the endothelial and haematopoietic systems but not in the skeleton. Although Runx1(Re/Re) embryos survived until birth and had a generally normal skeleton, the development of mineralisation in the sternum and some skull elements was significantly disrupted. In contrast to wild type embryos, the sternum of E17.5 Runx1(Re/Re) embryos showed high levels of Sox-9 and collagen type II expression and lack of development hypertrophic chondrocytes. In situ hybridizat! ion analysis demonstrated that in contrast to the vertebrae and long bones, the sternum of wild-type embryos expresses high levels of Runx1, but not Runx2, the master regulator of skeletogenesis. Thus, although Runx1 is not essential for major skeletal development, it does play an essential role in the development of the sternum and some skull elements. PMID: 20152828 [PubMed - as supplied by publisher] | | |
| Purification of adenoviral vectors by combined anion exchange and gel filtration chromatography.
February 16, 2010 at 6:34 AM
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| | Purification of adenoviral vectors by combined anion exchange and gel filtration chromatography. J Gene Med. 2009 Nov;11(11):978-89 Authors: Eglon MN, Duffy AM, O'Brien T, Strappe PM BACKGROUND: Adenoviral vectors are used extensively in human gene therapy trials and in vaccine development. Large-scale GMP production requires a downstream purification process, and liquid chromatography is emerging as the most powerful mode of purification, enabling the production of vectors at a clinically relevant scale and quality. The present study describes the development of a two-step high-performance liquid chromatography (HPLC) process combining anion exchange (AIEX) and gel filtration (GF) in comparison with the caesium chloride density gradient method. METHODS: HEK-293 cells were cultured in ten-layer CellStacks() and infected with 10 pfu/cell of adenoviral vector expressing green fluorescent protein (Ad5-GFP). Cell-bound virus was harvested and benzonase added to digest DNA, crude lysate was clarified by centrifugation and filtration prior to HPLC. Chromatography fractions were added to HEK-293 cells and GFP expression measured using a fluorescent p! late reader. RESULTS: Using AIEX then GF resulted in an adenoviral vector with purity comparable to Ad5-GFP purified by CsCl, whereas the reverse process (GF-AIEX) showed a reduced purity by electrophoresis and required further buffer exchange of the product. The optimal process (AIEX-GF) resulted in a vector yield of 2.3 x 10(7) pfu/cm(2) of cell culture harvested compared to 3.3 x 10(7) pfu/cm(2) for CsCl. The process recovery for the HPLC process was 36% compared to 27.5% for CsCl and total virion to infectious particle ratios of 18 and 11, respectively, were measured. CONCLUSIONS: We present a simple two-step chromatography process that is capable of producing high-quality adenovirus at a titre suitable for scale-up and clinical translation. PMID: 19670285 [PubMed - indexed for MEDLINE] | | | | 
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