|  |  |  | | | | | TE-RegenMed-StemCell feed | | | | | | | | | | | | | | | | | | Two California newspapers today offered quite different views of the world – one bleak and the other filled with hope. They implicitly captured the framework that will determine the fate of the state's $3 billion stem cell research effort.
In the simplest terms, it could boil down to school kids vs. stem cell researchers. Or it could be framed as school kids vs. the health of millions or in | | | | | | | | | | | | | | | | | | | | | | | | | In vitro hydrolytic and enzymatic degradation of nestlike-patterned electrospun poly(D,L-lactide-co-glycolide) scaffolds. J Biomed Mater Res A. 2010 Aug 19; Authors: Zhou X, Cai Q, Yan N, Deng X, Yang X A common problem in applying electrospun biodegradable polyester matrixes as tissue-engineering scaffolds is their serious shrinkage with degradation to reduce the porosity drastically. To ameliorate this problem, a nestlike-patterned poly(D,L-lactide-co-glycolide) (PLGA) nanofibrous ( approximately 900 nm) matrix was proposed and fabricated by electropinning. Shrinkage studies demonstrated that the dimension change of nestlike-patterned fibrous membrane was much smaller than those of nonwoven and parallel-aligned fibrous membranes. And the robust framework of the patterned matrix helped to maintain its original nestlike topographical structure during degradation. Compared to hydrolytic-degraded specimens, the PLGA nanofibrous matrixes degraded in the presence of lysozyme showed larger weight loss but slower decrease in molecular weight. Besides, porous fibers with intact surface were detected by scanning electron microscopy after 20-week hydrolysis, and fibers with pores both inside and on surface were observed after enzymatic degradation for 12 weeks. Accordingly, the former presented a bimodal gel permeation chromatography (GPC) peak, while no bi or multimodal GPC peaks were found for the latter as degradation proceeded. These results indicated that an acid autocatalytic effect still existed in the hydrolysis of PLGA nanofibrous matrix. The presence of lysozyme could only accelerate the dissolution of degradation products with low molecular weight, but have no contribution to the chain scission. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 20725988 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | In vivo evaluation of MMP sensitive high-molecular weight HA-based hydrogels for bone tissue engineering. J Biomed Mater Res A. 2010 Aug 19; Authors: Kim J, Kim IS, Cho TH, Kim HC, Yoon SJ, Choi J, Park Y, Sun K, Hwang SJ Hyaluronic acid (170 kDa)-based hydrogel was synthesized using acrylated hyaluronic acid (HA) and matrix metalloproteinase (MMP) sensitive HA-based hydrogels were then prepared by conjugation with two different peptides: cell adhesion peptides containing integrin-binding domains (Arg-Gly-Asp: RGD) and a cross-linker with MMP degradable peptides to mimic the remodeling characteristics of natural extracellular matrices by cell-derived MMPs. Mechanical properties of these hydrogels were evaluated with different weight percentages (2.5 and 3.5 wt %) by measuring elastic modulus, viscous modulus, and swelling ratio. Human mesenchymal stem cells (hMSCs) were then cultured in MMP-sensitive or insensitive HA-based hydrogels and/or immobilized cell adhesive RGD peptides in vitro. Actin staining and image analysis proved that cells cultured in the MMP-sensitive hydrogel with RGD peptides showed extensive cell spreading and sprouting. Gene expression analysis showed that bone specific genes such as alkaline phosphatase, osteocalcin, and osteopontin increased in MMP-sensitive hydrogels as biomolecules such as BMPs and cells were added in the gels. For in vivo calvarial defect regeneration, five different samples (MMP insensitive hydrogel, MMP sensitive hydrogel, MMP sensitive hydrogel with BMP-2, MMP sensitive hydrogel with hMSC, and MMP sensitive hydrogel with BMP-2 and hMSC) were prepared. After 4 weeks of implantation, the Masson-Trichrome staining and micro computed tomography scan results demonstrated that the MMP sensitive hydrogels with BMP-2 and hMSCs have the highest mature bone formation. The MMP sensitive HA-based hydrogel could become useful scaffolds in bone tissue engineering with improvements on tissue remodeling rates and regeneration activity. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 20725983 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Mono-dispersed bioactive glass nanospheres: Preparation and effects on biomechanics of mammalian cells. J Biomed Mater Res A. 2010 Aug 19; Authors: Hong Z, Luz GM, Hampel PJ, Jin M, Liu A, Chen X, Mano JF Mono-dispersed SiO(2)-CaO bioactive glass nanospheres (BGNS) were prepared by a two step sol-gel method in the absence of surfactant. The size of BGNS ranged from 200 to 350 nm in diameter and exhibited a rough surface texture. In vitro biomineralization tests showed that BGNS could rapidly induce the deposition of an apatite layer in simulated body fluid (SBF). The effect of bioactive glass on the biomechanical properties of various mammalian cells was first reported in this paper. Atomic force microscopy (AFM) was used for measuring the biomechanical properties of mammalian cells. The result showed that BGNS-medium could significantly decrease the plasma membrane stiffness of bone marrow stem cells (BMSCs) by approximately 50% and stimulate BMSCs spreading. The effect of BGNS on biomechanical properties of bovine aortic endothelial cells (BAECs) was opposite to that on BMSCs. BGNS increased the BAECs' stiffness and stimulated the elongation of endothelial cells and the formation of endothelial networks, which might potentially facilitate the vascularization of implanted BGNS-based biomaterials in tissue engineering as a scaffold or as an injectable system. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 20725980 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Evaluation of dense polylactic acid/beta-tricalcium phosphate scaffolds for bone tissue engineering. J Biomed Mater Res A. 2010 Aug 19; Authors: Yanoso-Scholl L, Jacobson JA, Bradica G, Lerner AL, O'Keefe RJ, Schwarz EM, Zuscik MJ, Awad HA Advances in biomaterial fabrication have introduced numerous innovations in designing scaffolds for bone tissue engineering. Often, the focus has been on fabricating scaffolds with high and interconnected porosity that would allow for cellular seeding and tissue ingrowth. However, such scaffolds typically lack the mechanical strength to sustain in vivo ambulatory stresses in models of load bearing cortical bone reconstruction. In this study, we investigated the microstructural and mechanical properties of dense PLA and PLA/beta-TCP (85:15) scaffolds fabricated using a rapid volume expansion phase separation technique, which embeds uncoated beta-TCP particles within the porous polymer. PLA scaffolds had a volumetric porosity in the range of 30 to 40%. With the embedding of beta-TCP mineral particles, the porosity of the scaffolds was reduced in half, whereas the ultimate compressive and torsional strength were significantly increased. We also investigated the properties of the scaffolds as delivery vehicles for growth factors in vitro and in vivo. The low-surface porosity resulted in sub optimal retention efficiency of the growth factors, and burst release kinetics reflecting surface coating rather than volumetric entrapment, regardless of the scaffold used. When loaded with BMP2 and VEGF and implanted in the quadriceps muscle, PLA/beta-TCP scaffolds did not induce ectopic mineralization but induced a significant 1.8-fold increase in neo vessel formation. In conclusion, dense PLA/beta-TCP scaffolds can be engineered with enhanced mechanical properties and potentially be exploited for localized therapeutic factor delivery. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 20725979 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Novel three-dimensional scaffolds of poly(L-lactic acid) microfibers using electrospinning and mechanical expansion: Fabrication and bone regeneration. J Biomed Mater Res B Appl Biomater. 2010 Aug 19; Authors: Shim IK, Jung MR, Kim KH, Seol YJ, Park YJ, Park WH, Lee SJ Poly(L-lactic acid) (PLLA) microfibrous scaffolds with three-dimensional (3D) structures were fabricated using an electrospinning technique with a subsequent mechanical expansion process. To achieve a 3D fibrous structure, the fusion at the contact points of the as-spun PLLA microfibers was avoided using an appropriate binary solvent system of methylene chloride and acetone. The solvent composition was optimized based on the solvent power, volatility, and viscosity (methylene chloride:acetone = 9:1 volume ratio). The final 3D structure of the electrospun scaffolds was obtained after mechanical expansion of the electrospun microfibrous mats. The pore sizes of the scaffolds were controlled by varying the degree of expansion of the nonbonded microfibrous mats, and they were in the range of several microns up to 400 mum. The 3D scaffolds were examined for their morphological properties and their potential use for the proliferation of osteoblasts. Generally recognized electrospun 2D nanofibrous membranes were also tested in order to compare the cell behaviors using different scaffold geometries. The 3D scaffolds demonstrated a high level of osteoblast proliferation (1.8-fold higher than nanofibrous membranes in a week). The osteoblasts actively penetrated the inside of the 3D scaffold and showed a spatial cell distribution, as confirmed by SEM and H&E staining, while a monolayer formed in the case of the 2D nanofibrous membranes with limited cell infiltration. In vivo results further showed that 3D electrospun microfibrous matrices were a favorable substrate for cell infiltration and bone formation after 2 and 4 weeks, using a rabbit calvarial defect model. In this study, the 3D microfibrous PLLA scaffolds fabricated using electrospinning techniques might be an innovative addition to tissue engineering applications. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. PMID: 20725960 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Silk hydrogel for cartilage tissue engineering. J Biomed Mater Res B Appl Biomater. 2010 Aug 19; Authors: Chao PH, Yodmuang S, Wang X, Sun L, Kaplan DL, Vunjak-Novakovic G Cartilage tissue engineering based on cultivation of immature chondrocytes in agarose hydrogel can yield tissue constructs with biomechanical properties comparable to native cartilage. However, agarose is immunogenic and nondegradable, and our capability to modify the structure, composition, and mechanical properties of this material is rather limited. In contrast, silk hydrogel is biocompatible and biodegradable, and it can be produced using a water-based method without organic solvents that enables precise control of structural and mechanical properties in a range of interest for cartilage tissue engineering. We observed that one particular preparation of silk hydrogel yielded cartilaginous constructs with biochemical content and mechanical properties matching constructs based on agarose. This finding and the possibility to vary the properties of silk hydrogel motivated this study of the factors underlying the suitability of hydrogels for cartilage tissue engineering. We present data resulting from a systematic variation of silk hydrogel properties, silk extraction method, gel concentration, and gel structure. Data suggest that silk hydrogel can be used as a tool for studies of the hydrogel-related factors and mechanisms involved in cartilage formation, as well as a tailorable and fully degradable scaffold for cartilage tissue engineering. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. PMID: 20725950 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Prediction of osteoconductive activity of modified potassium fluorrichterite glass-ceramics by immersion in simulated body fluid. J Mater Sci Mater Med. 2010 Aug 20; Authors: Bhakta S, Pattanayak DK, Takadama H, Kokubo T, Miller CA, Mirsaneh M, Reaney IM, Brook I, van Noort R, Hatton PV Potassium fluorrichterite (KNaCaMg(5)Si(8)O(22)F(2)) glass-ceramics were modified by either increasing the concentration of calcium (GC5) or by the addition of P(2)O(5) (GP2). The stoichiometric composition (GST), GC5 and GP2 were soaked in simulated body fluid (SBF) along with 45S5-type bioglass as a control. After immersion, surface analyses were performed using thin-film X-ray diffraction (TF-XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared (reflection) spectroscopy (FT-IR). All compositions showed the formation of a calcium phosphate rich surface layer in SBF; GST, GP2 and the bioglass control within 7 days of immersion and GC5 after 14 days. It was concluded that all compositions were likely to be osteoconductive in vivo, with GP2 providing the best performance in terms of the combination of rapid formation of the surface layer and superior mechanical properties. This glass-ceramic system has potential as a load bearing bioceramic for fabrication of medical devices intended for skeletal tissue repair. PMID: 20725768 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | The influence of bioreactor geometry and the mechanical environment on engineered tissues. J Biomech Eng. 2010 May;132(5):051006 Authors: Osborne JM, O'Dea RD, Whiteley JP, Byrne HM, Waters SL A three phase model for the growth of a tissue construct within a perfusion bioreactor is examined. The cell population (and attendant extracellular matrix), culture medium, and porous scaffold are treated as distinct phases. The bioreactor system is represented by a two-dimensional channel containing a cell-seeded rigid porous scaffold (tissue construct), which is perfused with a culture medium. Through the prescription of appropriate functional forms for cell proliferation and extracellular matrix deposition rates, the model is used to compare the influence of cell density-, pressure-, and culture medium shear stress-regulated growth on the composition of the engineered tissue. The governing equations are derived in O'Dea et al. "A Three Phase Model for Tissue Construct Growth in a Perfusion Bioreactor," Math. Med. Biol., in which the long-wavelength limit was exploited to aid analysis; here, finite element methods are used to construct two-dimensional solutions to the governing equations and to investigate thoroughly their behavior. Comparison of the total tissue yield and averaged pressures, velocities, and shear stress demonstrates that quantitative agreement between the two-dimensional and long-wavelength approximation solutions is obtained for channel aspect ratios of order 10(-2) and that much of the qualitative behavior of the model is captured in the long-wavelength limit, even for relatively large channel aspect ratios. However, we demonstrate that in order to capture accurately the effect of mechanotransduction mechanisms on tissue construct growth, spatial effects in at least two dimensions must be included due to the inherent spatial variation of mechanical stimuli relevant to perfusion bioreactors, most notably, fluid shear stress, a feature not captured in the long-wavelength limit. PMID: 20459207 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Immunohistochemical study of oral epithelial sheets cultured on amniotic membrane for oral mucosal reconstruction. Biomed Mater Eng. 2010 Jan;20(1):37-45 Authors: Amemiya T, Nakamura T, Yamamoto T, Kinoshita S, Kanamura N We immunohistochemically evaluated whether oral epithelial cells grown on amniotic membrane (AM) would be an effective biomaterial for reconstructing oral mucosal defects. Oral mucosal epithelial cells from albino rabbits were grown for 2-3 weeks on an AM carrier in a co-culture with 3T3 fibroblasts. The rabbits' oral mucosal defects were reconstructed by autologous transplantation of the oral epithelial sheets. The oral epithelial sheets and reconstructed tissues were then examined histologically and immunohistochemically. After 2-3 weeks of culture, the rabbit oral mucosal epithelial cells developed 5-7 layers of stratification on the AM. Immunohistochemistry revealed that they expressed keratins 4/13, integrin alpha 6, alpha 5 chain and collagen type III, but not keratins 1/10. The transplanted sheets attached to the mucosal defects, and AM fragments disappeared from the transplant area. Immunohistochemical patterns revealed properties of the mucous membrane and basement membrane components in the reconstructed epithelia. The results of this experiment showed that the AM-cultured oral epithelial sheets resulted in mucosa-like differentiation, and adhered to the mucosal defects. Therefore, AM-cultured oral epithelial sheets might be a useful biomaterial for oral mucosal reconstruction. PMID: 20448302 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Preparation and evaluation of microporous organogel scaffolds for cell viability and proliferation. Colloids Surf B Biointerfaces. 2010 Aug 1;79(1):105-12 Authors: Lukyanova L, Franceschi-Messant S, Vicendo P, Perez E, Rico-Lattes I, Weinkamer R Various porous scaffolds utilizing an organogel were prepared by particulate-leaching method. The porous organogels were made of biodegradable, non-toxic ingredients like soybean oil or caprylic/capric triglyceride as the organic liquids and 12-hydroxystearic acid as the gelator. The scaffolds possessed an effective porosity of 56-65%, and good pore interconnectivity with an average pore size from 220 to 290mum. The biodegradability of such materials was evaluated and lipases were able to totally degrade the scaffolds. The porosity of the material associated with high draining led to suitable scaffolds which were evaluated for CHO cell viability and proliferation using the MTT test. This evaluation was performed over a period of 3 weeks and showed a greater ability to promote cell proliferation for the soybean oil based scaffold than for the caprylic/capric triglyceride one. The histological investigations revealed that this scaffold was able to promote cell colonization and attachment and could induce the production of collagen. PMID: 20427161 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Molecular assembly and biological activity of a recombinant fragment of fibronectin (FNIII(7-10)) on poly(ethyl acrylate). Colloids Surf B Biointerfaces. 2010 Jul 1;78(2):310-6 Authors: Rico P, González-GarcÃa C, Petrie TA, GarcÃa AJ, Salmerón-Sánchez M Fibronectin (FN) fibrillogenesis is a cell-mediated process involving integrin activation that results in conformational changes of FN molecules and the organization of actin cytoskeleton. A similar process can be induced by some particular chemistries in the absence of cells, e.g., poly(ethyl acrylate) (PEA), which enhance FN-FN interactions leading to the formation of a biologically active network on the material surface. We have investigated the organization of a recombinant fragment of fibronectin (FNIII(7-10)) upon adsorption on this particular chemistry, PEA. Atomic force microscopy (AFM) was used to identify individual molecules of the fragment after adsorption, as well as the evolution of the distribution of adsorbed molecules on the surface of the material as the concentration of the adsorbing solution increased. Globular molecules that turn into small aggregates were found as a function of solution concentration. Above a threshold concentration of the adsorbing solution (50 microg/mL) an interconnected network of the FNIII(7-10) fragment is obtained on the material surface. The bioavailability of specific cell adhesion domains, including RGD, within the molecules was higher on PEA than on the control glass. The biological activity of the fragment was further investigated by evaluating focal adhesion formation and actin cytoskeleton for MC3T3-E1 osteoblast-like cells. Well-developed focal adhesion complexes and insertions of actin stress fibers were found on PEA in a similar way as it happens in the control SAM-OH. Moreover, increasing the hydrophilicity of the surface by incorporating -OH groups led to globular molecules of the fragment homogeneously distributed throughout the surface; and the cell-material interaction is reduced as depicted by the lack of well-developed focal plaques and actin cytoskeleton. PMID: 20409696 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Cell therapy for diabetes: stem cells, progenitors or beta-cell replication? Mol Cell Endocrinol. 2010 Jul 8;323(1):55-61 Authors: Gonez LJ, Knight KR The cure for type 1 diabetes (T1D) will require either the replacement or regeneration of insulin-producing cells, together with measures that prevent their immune-mediated destruction. Experiments in rodent models have found that pancreatic stem cells, committed progenitors and replicating beta-cells can all contribute to insulin-producing cell regeneration. The cellular and molecular mechanisms of these cells, both in vitro and in vivo, have been investigated by us and by others. Furthermore, our surgical research laboratory has developed a unique in vivo chamber model of T1D, allowing the assessment of the behaviour of different sources of insulin-producing cells with a view to their potential use in cell-based therapies. PMID: 20026173 [PubMed - indexed for MEDLINE] | | | | | | | | | |  | |  | |  |
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