| Functional and transcriptional characterization of human embryonic stem cell-derived endothelial cells for treatment of myocardial infarction.
January 5, 2010 at 11:15 am
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| | Functional and transcriptional characterization of human embryonic stem cell-derived endothelial cells for treatment of myocardial infarction. PLoS One. 2009;4(12):e8443 Authors: Li Z, Wilson KD, Smith B, Kraft DL, Jia F, Huang M, Xie X, Robbins RC, Gambhir SS, Weissman IL, Wu JC BACKGROUND: Differentiation of human embryonic stem cells into endothelial cells (hESC-ECs) has the potential to provide an unlimited source of cells for novel transplantation therapies of ischemic diseases by supporting angiogenesis and vasculogenesis. However, the endothelial differentiation efficiency of the conventional embryoid body (EB) method is low while the 2-dimensional method of co-culturing with mouse embryonic fibroblasts (MEFs) require animal product, both of which can limit the future clinical application of hESC-ECs. Moreover, to fully understand the beneficial effects of stem cell therapy, investigators must be able to track the functional biology and physiology of transplanted cells in living subjects over time. METHODOLOGY: In this study, we developed an extracellular matrix (ECM) culture system for increasing endothelial differentiation and free from contaminating animal cells. We investigated the transcriptional changes that occur during endothelial differentiation of hESCs using whole genome microarray, and compared to human umbilical vein endothelial cells (HUVECs). We also showed functional vascular formation by hESC-ECs in a mouse dorsal window model. Moreover, our study is the first so far to transplant hESC-ECs in a myocardial infarction model and monitor cell fate using molecular imaging methods. CONCLUSION: Taken together, we report a more efficient method for derivation of hESC-ECs that express appropriate patterns of endothelial genes, form functional vessels in vivo, and improve cardiac function. These studies suggest that hESC-ECs may provide a novel therapy for ischemic heart disease in the future. PMID: 20046878 [PubMed - in process] |
| Guided Cell Migration on Microtextured Substrates with Variable Local Density and Anisotropy.
January 5, 2010 at 11:15 am
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| | Guided Cell Migration on Microtextured Substrates with Variable Local Density and Anisotropy. Adv Funct Mater. 2009 Feb 6;19(10):1579-1586 Authors: Kim DH, Seo CH, Han K, Kwon KW, Levchenko A, Suh KY This work reports the design of and experimentation with a topographically patterned cell culture substrate of variable local density and anisotropy as a facile and efficient platform to guide the organization and migration of cells in spatially desirable patterns. Using UV-assisted capillary force lithography, an optically transparent microstructured layer of a UV curable poly(urethane acrylate) resin is fabricated and employed as a cell-culture substrate after coating with fibronectin. With variable local pattern density and anisotropy present in a single cell-culture substrate, the differential polarization of cell morphology and movement in a single experiment is quantitatively characterized. It is found that cell shape and velocity are exquisitely sensitive to variation in the local anisotropy of the two-dimensional rectangular lattice arrays, with cell elongation and speed decreasing on symmetric lattice patterns. It is also found that cells could integrate orthogonal spatial cues when determining the direction of cell orientation and movement. Furthermore, cells preferentially migrate toward the topographically denser areas from sparser ones. Consistent with these results, it is demonstrated that systematic variation of local densities of rectangular lattice arrays enable a planar assembly of cells into a specified location. It is envisioned that lithographically defined substrates of variable local density and anisotropy not only provide a new route to tailoring the cell-material interface but could serve as a template for advanced tissue engineering. PMID: 20046799 [PubMed - as supplied by publisher] |
| Poly(3-hydroxybutyrate) multifunctional composite scaffolds for tissue engineering applications.
January 5, 2010 at 11:15 am
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| | Poly(3-hydroxybutyrate) multifunctional composite scaffolds for tissue engineering applications. Biomaterials. 2009 Dec 31; Authors: Misra SK, Ansari TI, Valappil SP, Mohn D, Philip SE, Stark WJ, Roy I, Knowles JC, Salih V, Boccaccini AR Poly(3-hydroxybutyrate) (P(3HB)) foams exhibiting highly interconnected porosity (85% porosity) were prepared using a unique combination of solvent casting and particulate leaching techniques by employing commercially available sugar cubes as porogen. Bioactive glass (BG) particles of 45S5 Bioglass((R)) grade were introduced in the scaffold microstructure, both in micrometer ((m-BG), <5 mum) and nanometer ((n-BG), 30 nm) sizes. The in vitro bioactivity of the P(3HB)/BG foams was confirmed within 10 days of immersion in simulated body fluid and the foams showed high level of protein adsorption. The foams interconnected porous microstructure proved to be suitable for MG-63 osteoblast cell attachment and proliferation. The foams implanted in rats as subcutaneous implants resulted in a non-toxic and foreign body response after one week of implantation. In addition to showing bioactivity and biocompatibility, the P(3HB)/BG composite foams also exhibited bactericidal properties, which was tested on the growth of Staphylococcus aureus. An attempt was made at developing multifunctional scaffolds by incorporating, in addition to BG, selected concentrations of Vitamin E or/and carbon nanotubes. P(3HB) scaffolds with multifunctionalities (viz. bactericidal, bioactive, electrically conductive, antioxidative behaviour) were thus produced, which paves the way for next generation of advanced scaffolds for bone tissue engineering. PMID: 20045554 [PubMed - as supplied by publisher] |
| Generation and manipulation of magnetic multicellular spheroids.
January 5, 2010 at 11:15 am
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| | Generation and manipulation of magnetic multicellular spheroids. Biomaterials. 2009 Dec 31; Authors: Ho VH, Müller KH, Barcza A, Chen R, Slater NK Multicellular spheroids have important applications in tumour studies, drug screening and tissue engineering. To enable simple manipulation of spheroids, magnetically labelled HeLa cells were cultured in hanging drops to generate magnetic spheroids. HeLa cells were labelled by biotinylating their cell membrane proteins and then binding streptavidin paramagnetic particles onto the biotinylated cell surface. Spheroids of different sizes were obtained by varying the seeding cell concentrations within the hanging drops and the spheroids had good cell viability. Characterisation of the F-actin distribution within the spheroids indicated a three dimensional reorganisation of the cellular cytoskeleton compared to monolayer cultures. The magnetic moment of the spheroids was measured and showed a superparamagnetic response in an applied field. Transmission electron microscopy analysis indicated that the paramagnetic particles were still present in the spheroids even after 21 days of culture. These spheroids could be easily and quickly separated magnetically without the need for centrifugation. The magnetic spheroids were also successfully manipulated and patterned using magnetic fields within a few seconds. The patterned spheroids then fused together to form a larger tissue construct. PMID: 20045553 [PubMed - as supplied by publisher] |
| Bone regeneration in defects compromised by radiotherapy.
January 5, 2010 at 11:15 am
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| | Bone regeneration in defects compromised by radiotherapy. J Dent Res. 2010 Jan;89(1):77-81 Authors: Hu WW, Ward BB, Wang Z, Krebsbach PH Because bone reconstruction in irradiated sites is less than ideal, we applied a regenerative gene therapy method in which a cell-signaling virus was localized to biomaterial scaffolds to regenerate wounds compromised by radiation therapy. Critical-sized defects were created in rat calvariae previously treated with radiation. Gelatin scaffolds containing lyophilized adenovirus encoding BMP-2 (AdBMP-2) or freely suspended AdBMP-2 were transplanted. Lyophilized AdBMP-2 significantly improved bone quality and quantity over free AdBMP-2. Bone mineral density was reduced after radiotherapy. Histological analyses demonstrated that radiation damage led to less bone regeneration. The woven bone and immature marrow formed in the radiated defects indicated that irradiation retarded normal bone development. Finally, we stored the scaffolds with lyophilized AdBMP-2 at -80 degrees C to determine adenovirus stability. Micro-CT quantification demonstrated no significant differences between bone regeneration treated with lyophilized AdBMP-2 before and after storage, suggesting that virus-loaded scaffolds may be convenient for application as pre-made constructs. PMID: 19966040 [PubMed - indexed for MEDLINE] |
| Optimization of scaled-up chitosan microparticles for bone regeneration.
January 5, 2010 at 11:15 am
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| | Optimization of scaled-up chitosan microparticles for bone regeneration. Biomed Mater. 2009 Oct;4(5):55006 Authors: Jayasuriya AC, Bhat A The aim of this study was to scale-up and optimize the chitosan (CS) microparticles (MPs) from 1x batch (41-85 mg) to 4x batch (270-567 mg) to be used in bone regeneration. The MPs used in the present study were prepared by double emulsification technique using CS as a base material under physiologically friendly conditions throughout the process. Structural integrity of MPs was improved creating cross-links between amine groups in CS and phosphate groups in tripolyphosphate (TPP) which has been used as an ionic cross-linking agent. The cross-linking density was varied using different amounts of TPP to CS such as 0%, 8%, 32%, 64% and 110% (w/w). The CS MPs were approximately spherical in shape with a size of 30-50 microm according to scanning electron microscopy results. X-ray diffraction data revealed having TPP in the CS MPs. The evidence of ionic cross-links in the CS MPs was analyzed using Fourier Transform Infra Red. When we scaled-up the yield of MPs, we investigated that 64% TPP cross-linking density provided the best quality MPs. In addition, those MPs provided the yield from 75 mg to 310 mg when scaled up from 1x to 4x batch, respectively. The MPs developed have a great potential to be used as an injectable scaffold for bone regeneration including orthopedic and craniofacial applications using minimally invasive conditions compared with conventional three-dimensional scaffolds. PMID: 19779252 [PubMed - indexed for MEDLINE] |
| The effects of dynamic and three-dimensional environments on chondrogenic differentiation of bone marrow stromal cells.
January 5, 2010 at 11:15 am
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| | The effects of dynamic and three-dimensional environments on chondrogenic differentiation of bone marrow stromal cells. Biomed Mater. 2009 Oct;4(5):55009 Authors: Jung Y, Kim SH, Kim YH, Kim SH Articular cartilage is subjected to complex loading, which plays a major role in its growth, development and maintenance. Previously, we found that mechanical stimuli enhanced the development and function of engineered cartilage tissues in elastic mechano-active poly(lactide-co-caprolactone) (PLCL) scaffolds. In addition, it is well known that the three-dimensional spatial organization of cells and extracellular matrices in hydrogels is crucial to chondrogenesis. This study was conducted to enhance the chondrogenic differentiation of bone marrow stromal cells (BMSCs) in the hybrid scaffolds of fibrin gels and PLCL scaffolds in dynamic environments by compression. A highly elastic scaffold was fabricated from very elastic PLCL with 85% porosity and a 300-500 microm pore size using a gel-pressing method. A mixture of rabbit BMSCs and fibrin gels was then seeded onto the PLCL scaffolds and subjected to continuous compressive deformation of 5% strain at 0.1 Hz for 10 days in a chondrogenic medium containing 10 ng ml(-1) TGF-beta(1). The BMSCs-seeded scaffold constructs were then implanted subcutaneously into nude mice. As a control, the cell-PLCL scaffold constructs were cultured under dynamic conditions or the cell-PLCL/fibrin hybrid scaffold constructs and the cell-PLCL scaffold constructs were cultured under static conditions for 10 days in vitro. The results revealed that cells adhered onto the hybrid scaffolds of fibrin gels and PLCL scaffolds cultured under dynamic conditions. In addition, the accumulation of the extracellular matrix of cell-scaffold constructs, which was increased through mechanical stimulation, showed that chondrogenic differentiation was sustained and enhanced significantly in the stimulated hybrid scaffold constructs. Overall, the results of this study indicate that the proper periodic application of dynamic compression and the three-dimensional environments of the hybrid scaffolds composed of fibrin gels and elastic PLCL can encourage BMSCs to differentiate into chondrocytes, maintain their phenotypes and enhance GAGs production, thereby improving the quality of cartilaginous tissue formed in vitro and in vivo. PMID: 19779251 [PubMed - indexed for MEDLINE] |
| Gel-derived bioglass as a compound of hydroxyapatite composites.
January 5, 2010 at 11:15 am
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| | Gel-derived bioglass as a compound of hydroxyapatite composites. Biomed Mater. 2009 Oct;4(5):55007 Authors: Cholewa-Kowalska K, Kokoszka J, Laczka M, Niedźwiedzki L, Madej W, Osyczka AM Despite the excellent biocompatibility of hydroxyapatite and bioglass, their clinical applications are limited to non-load-bearing implants and implant coatings due to their low mechanical properties. We have developed two different composites made of hydroxyapatite (HA) and gel-derived bioglasses designated S2 (80 mol% SiO(2)-16 mol% CaO-4 mol% P(2)O(5)) or A2 (40 mol% SiO(2)-54 mol% CaO-6 mol% P(2)O(5)). We show that the combination of hydroxyapatite with either bioglass results in better composite bioactivity and biocompatibility compared to HA alone. We used a commercially available hydroxyapatite that was sintered with varying additions (10%, 50%) of A2 or S2 bioglass. Scanning electron microscopy and x-ray diffraction were used to characterize the microstructure and phases of the composites. The elastic properties of bioglass/HA composites were analyzed with the use of the pulse ultrasonic technique. The bioactivity (surface activity) of the composites was assessed by determining the changes of surface morphology and composition after soaking in simulated body fluid (SBF) for 7 and 14 days. The biocompatibility of the obtained composites was then assessed in vitro using adult human bone marrow stromal cells. Cells were seeded on the material surfaces at a density of 10(4) cells cm(-2) and cultured for 7 days in non-differentiating and osteogenic conditions. The number of live cells was estimated in both standard and osteogenic cultures, followed by alkaline phosphatase (ALP) activity assay in osteogenic cultures. We determined that 10 wt% addition of A2 (E = 12.24 GPa) and 50 wt% addition of S2 (E = 16.96 GPa) to the HA base results in higher Young's modulus of the composites compared to pure hydroxyapatite (E = 9.03 GPa). The rate of Ca-P rich layer formation is higher for bioglass/HA composites containing A2 bioglass compared to the composites containing S2 bioglass. Evaluation of cell growth on the bioglass/HA composites showed that the incorporation of either 50 wt% S2 or 50 wt% A2 into the hydroxyapatite base significantly improves cell viability when compared to cells grown on pure HA. Also the cellular activity of ALP, an early marker of osteoblasts, increases with the amount of bioglass addition to the composites. PMID: 19779249 [PubMed - indexed for MEDLINE] | | | 
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