|Articles about Biomaterials|
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| Enhanced vascular-related cellular affinity on surface modified copolyesters of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx)
Qu, X. H., Q. Wu, et al. (2005), Biomaterials 26(34): 6991-7001.
Abstract: Random copolyester of 3-hydroxybutyrate and 3-hydroxyhexanoate, short as PHBHHx, was surface modified by ammonia plasma treatment and/or fibronectin coating, respectively. The improved results were demonstrated by better growth of human umbilical vein endothelial cells (HUVECs) and rabbit aorta smooth muscle cells (SMCs) on the surface of ammonia plasma-treated PHBHHx coated with fibronectin (PFn-PHBHHx), compared with the fibronectin-coated (Fn-PHBHHx) or uncoated PHBHHx, respectively, although XPS analysis and ELISA demonstrated higher fibronectin adsorption on Fn-PHBHHx than on PFn-PHBHHx. Confocal microscopy observation showed that the specific co-localization of fibronectin with F-actin was impaired on PFn-PHBHHx, while it was almost lost on Fn-PHBHHx compared with pristine PHBHHx or plasma-treated PHBHHx (P-PHBHHx). These were attributed to the generation of new nitrogen- and oxygen-containing groups on the PHBHHx surface by the ammonia plasma treatment, which led to increased polar components that enhanced polymer surface energy and hydrophilic properties on P-PHBHHx. The most prominent effect of PFn-PHBHHx was its stimulation of HUVECs proliferation. HUVECs on PFn-PHBHHx formed a confluent monolayer after 3 days of incubation, while SMCs were unable to form a sub-confluent layer. The above evidences revealed that PFn-PHBHHx would benefit endotheliazation rather than SMCs proliferation. We therefore believed that PFn-PHBHHx would be a promising material as a luminal surface of vascular grafts.
| Enhancement of gap junctional intercellular communication of normal human dermal fibroblasts cultured on polystyrene dishes grafted with poly-N-isopropylacrylamide
Nagira, T., S. B. Matthew, et al. (2005), Tissue Eng 11(9-10): 1392-7.
Abstract: Technology developed to allow recovery of cells without enzyme treatment, involving a dish grafted with a thermoreactive polymer gel of poly-N-isopropylacrylamide (PIPAAm), was found to significantly enhance gap junctional intercellular communication (GJIC) in normal human dermal fibroblasts (NHDF cells). NHDF cells were cultured for 4 days on PIPAAm-grafted dishes irradiated with various doses of electron beams, and GJIC was assayed by the scrape-loading dye transfer method. The area of dye transfer was greater in the PIPAAm-grafted dishes than in the control culture dishes, indicating that the PIPAAm-grafted dishes enhanced the GJIC of NHDF cells. Connexin-43 (Cx43) expression was analyzed because Cx43 is considered to be a main component of the gap junctional channel. PIPAAm-grafted dishes irradiated with 100, 250, or 500 kGy of electron beams showed significantly enhanced expression of Cx43-NP, Cx43-P1, and especially Cx43-P2. Enhanced expression of Cx43-P2, a functional transmembrane protein, may be related to the promotion of GJIC. These results suggest that the PIPAAm-grafted dish not only enables the enzyme-free recovery of a cell monolayer for use in the construction of a three-dimensional artificial tissue, but also significantly contributes to the enhancement of GJIC, which may partly promote tissue strength on the surface of the PIPAAm-grafted dish.
| Enhancement of hydroxyapatite-mediated three-dimensional-like proliferation of mouse fibroblasts by heat treatment: effects of heat shock-induced p38 MAPK pathway
Hiragami, F., J. Akiyama, et al. (2005), J Biomed Mater Res A 74(4): 705-11.
Abstract: Regulation of the biocompatibility of compositional hydroxyapatite (HA) with cells is affected by various environmental factors. The aim of this study was to determine whether the p38 mitogen-activated protein kinase (MAPK) pathway has a key role in enhancement of HA-mediated three-dimensional (3D)-like proliferation of mouse fibroblasts after heat treatment. C3H10T1/2 mouse fibroblasts were cultured with HA granules for 10 weeks after heat treatment at 44 degrees C for 5, 10, 20, and 30 min. The mean rate of formation of 3D-like proliferation patterns by cells heat treated for 20 min was only 2.1-fold higher than that by untreated cells, but the mean rates of formation of 3D-like proliferation patterns by cells heat treated for 5 and 10 min were significantly higher (3.7- and 3.3-fold higher, respectively) than that by untreated cells (p < 0.01). Western blot analysis demonstrated that phosphorylation of p38 MAPK was markedly increased by heat treatment at 44 degrees C for 5 and 10 min. In addition, the activation of heat shock-induced p38 MAPK was markedly reduced by treatment at 44 degrees C for 30 min. We concluded that 3D-like proliferation of heat-treated cells was induced by activation of p38 MAPK. The results of this study should be useful for further studies aimed at elucidation of regulation of the biocompatibility of compositional HA with cells.
| Enhancement of ionic conductivity of PEO based polymer electrolyte by the addition of nanosize ceramic powders
Wang, G. X., L. Yang, et al. (2005), J Nanosci Nanotechnol 5(7): 1135-40.
Abstract: The ionic conductivity of polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) has been improved by the addition of nanosize ceramic powders (TiO2 and AL2O3). The PEO based solid polymer electrolytes were prepared by the solution-casting method. Electrochemical measurement shows that the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte has the best ionic conductivity (about 10(-4) S cm(-1) at 40-60 degrees C). The lithium transference number of the 10 wt% TiO2 PEO-LiClO4 polymer electrolyte was measured to be 0.47, which is much higher than that of bare PEO polymer electrolyte. Ac impedance testing shows that the interface resistance of ceramic-added PEO polymer electrolyte is stable. Linear sweep voltammetry measurement shows that the PEO polymer electrolytes are electrochemically stable in the voltage range of 2.0-5.0 V versus a Li/Li+ reference electrode.
| Enhancement of p,p'-DDT photodegradation on soil surfaces using TiO2 induced by UV-light
Quan, X., X. Zhao, et al. (2005), Chemosphere 60(2): 266-73.
Abstract: Enhancement of p,p'-DDT photodegradation on soil surfaces using TiO2 induced by UV-light was mainly investigated in this work. After being spiked with p,p'-DDT, soil samples loaded with different doses of TiO2 (0%, 0.5%, 1%, 2%, and 3% wt) were exposed to UV-light irradiation for 24 h. The results indicated that the photodegradation of p,p'-DDT followed the pseudo-first-order kinetics. TiO2 accelerated the photodegradation of p,p'-DDT significantly as indicated by the half-life reduction from 23.3 h to 10.4 h, corresponding to the TiO2 content from 0% to 3% respectively. In addition, the effects of soil pH, photon flux and humic substances on p,p'-DDT degradation were investigated. The photodegradation rate increased with the increase of the soil pH and photon flux. The humic substances (2% wt) inhibited the p,p'-DDT photodegradation by reducing the amount of light available to excite the p,p'-DDT and TiO2 or by quenching radicals capable of oxidizing p,p'-DDT. p,p'-DDE, p,p'-DDD and DDMU were main degradation intermediates and they were further degraded in the presence of TiO2.
| Entrapment of some compounds into biocompatible nano-sized particles and their releasing properties
Watanabe, J., S. Iwamoto, et al. (2005), Colloids Surf B Biointerfaces 42(2): 141-6.
Abstract: Two types of biocompatible nanoparticles with an average diameter of around 200 nm were formed only by mixing hydrolysates of chitosan and carboxymethyl cellulose (CMC). Nanoparticle A was produced from chitosanase hydrolysate of chitosan and cellulase hydrolysate of carboxymethyl cellulose, and nanoparticle B was produced from lysozyme hydrolysate of chitosan and the carboxymethyl cellulose hydrolysate. Negatively charged or amphoteric compounds were first mixed with chitosan hydrolysate and then added to carboxymethyl cellulose hydrolysate to effectively entrap them in the particles. Positively charged compounds could also be effectively entrapped by mixing the hydrolysates and the compound in the reverse order. Negatively charged compounds with high molecular weights were maintained in the particles even at the higher pH levels than the pK(a) of the amino groups of chitosan. Entrapped compounds were gradually released from nanoparticle A by lysozyme treatment. In contrast, there was no release from nanoparticle B. These results indicate that nanoparticle A can be applied to controlled-release drug delivery systems, and that nanoparticle B is stably retained in the body without releasing the entrapped compounds.
| Enucleation with primary implant insertion for treatment of recalcitrant endophthalmitis and panophthalmitis
Abel, A. D. and D. R. Meyer (2005), Ophthal Plast Reconstr Surg 21(3): 220-6.
Abstract: PURPOSE: A prevalent conception exists that a two-stage operation (i.e., primary enucleation or evisceration with delayed secondary orbital implant insertion) is necessary when enucleation is required for recalcitrant endophthalmitis or panophthalmitis. The purpose of this study was to assess the utility of single-stage enucleation and primary reconstruction in this setting. METHODS: In a retrospective interventional case series, 22 consecutive patients with advanced endophthalmitis or panophthalmitis refractory to prior medical treatment underwent enucleation and primary implant placement by a single surgeon between 1991 and 2001. Eleven patients received hydroxyapatite implants; 11 patients received silicone implants. All patients were treated during surgery with intravenous antibiotics. All patients were evaluated for persistent local or systemic infection, implant exposure, extrusion, and successful fitting of their prostheses. RESULTS: No cases of persistent orbital cellulitis or meningitis occurred in any of the patients. Two patients with silicone orbital implants had extrusions; one was successfully managed with a secondary dermis-fat graft, and another patient who refused additional treatment was allowed to heal by secondary intention after the implant was removed. None of the patients with hydroxyapatite orbital implants had complications. All patients (20/20) who elected to undergo prosthetic fitting were successfully fit with prostheses. One patient elected not to pursue prosthetic fitting. One patient died of unrelated causes before a prosthesis could be fit. There were no objective findings to preclude successful fitting in either case. CONCLUSIONS: This study suggests that enucleation with primary orbital reconstruction and implant insertion for recalcitrant, fulminant ocular infection is an acceptable and advantageous treatment strategy. The risks and expenses associated with two separate surgeries are decreased, hospitalization time is potentially reduced, and subsequent rehabilitation can be initiated in a more timely fashion.
| Environmentally smart polymers
Williams, D. (2005), Med Device Technol 16(4): 9-10, 13.
Abstract: Much progress has been made in the synthesis of polymers that emulate certain naturally occurring polymers and demonstrate exquisite sensitivity to environmental factors such as temperature, pH and mechanical stress. This article explains how these are finding use in medical technologies such as drug delivery and cell-sheet tissue engineering.
| Enzymatic transformation of bacterial polyhydroxyalkanoates into repolymerizable oligomers directed towards chemical recycling
Kaihara, S., Y. Osanai, et al. (2005), Macromol Biosci 5(7): 644-52.
Abstract: The enzymatic transformation into an oligomer was carried out with the objective of developing the chemical recycling of bacterial polyesters. Poly(R-3-hydroxyalkanoate)s (PHAs), such as poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyhexanoate)] and poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyvalerate)], were degraded by granulated Candida antarctica lipase B immobilized on hydrophilic silica (lipase GCA) in a diluted organic solvent at 70 degrees C. The degradation products were cyclic oligomers having a molecular weight of a few hundreds. The obtained cyclic oligomer was readily repolymerized by the same lipase (lipase GCA) to produce the corresponding polyester in a concentrated solution. The cyclic oligomer was copolymerized with epsilon-caprolactone using lipase to produce the corresponding terpolymers having an Mw of 21,000. This is the first example of the enzymatic chemical recycling of bacterial PHAs using lipase. Poly(R-3-hydroxybutyrate) [P(3HB)] was also degraded into the linear-type R-3HB monomer to trimer by P(3HB)-depolymerase (PHBDP) in phosphate buffer at 37 degrees C. The degradation using PHBDP required a longer reaction time compared with the lipase-catalyzed degradation in organic solvent. The monomer composition of the oligomer depended on the origin of the PHBDP. The R-3HB monomer was predominately produced by PHBDP from Pseudomonas stutzeri, while the R-3HB dimer was produced by PHBDP from Alcaligenes faecalis T1. Repolymerization of these oligomers by lipase in concentrated organic solvent produced a relatively low-molecular-weight P(3HB) (e.g., Mw=2,000). Degradation of P(3HB) by lipase in organic solvent into repolymerizable cyclic oligomer and degradation of P(3HB) by PHBDP in buffer into hydroxy acid type R-3HB dimer.
| Enzymatically cross-linked hydrogels and their adhesive strength to biosurfaces
Hu, B. H. and P. B. Messersmith (2005), Orthod Craniofac Res 8(3): 145-9.
Abstract: OBJECTIVES: To design an in-situ gelling hydrogel capable of solidifying rapidly under physiologic conditions into a hydrogel capable of adhering tissue surfaces together. DESIGN: Multifunctional polymers containing covalently bound peptide substrates of transglutaminase were designed. EXPERIMENTAL VARIABLE: Enzyme cross-linked hydrogels were compared with commercial fibrin tissue adhesive. OUTCOME MEASURE: The shear strength between tissue surfaces or type 1 collagen membranes bonded with hydrogel was measured. RESULTS: The shear adhesive strength of transglutaminase cross-linked hydrogels was found to be equal to or better than fibrin sealant for tissue and collagen surfaces, respectively. CONCLUSION: Transglutaminase cross-linked hydrogels are injectable, in-situ formed, biodegradable, and expected to be useful in a variety of applications including sustained drug delivery, medical and dental adhesives, tissue repair and engineering as polymeric scaffolds, and gene therapy.
| Enzyme-biomaterial interactions: effect of biosystems on degradation of polyurethanes
Santerre, J. P., R. S. Labow, et al. (1993), J Biomed Mater Res 27(1): 97-109.
Abstract: Enzyme-induced liberation of hard-segment-containing components from polyurethanes was evaluated using two 14C-labeled polyurethanes. A polyester urea-urethane and polyether urea-urethane were synthesized from toluene-2,4-diisocyanate (TDI)/polycaprolactone diol (PCL) or TDI/polyethylene glycol (PEO) with 14C-labeled ethylene diamine. Both materials were characterized using electron spectroscopy for chemical analysis (ESCA), differential scanning calorimetry (DSC), size exclusion chromatography, and material chemistry by Fourier transform infrared (FTIR) spectroscopy. Biodegradation assays were carried out using cholesterol esterase (CE), collagenase (CO), cathepsin B (CB), and xanthine oxidase (XO) at the pH optimum conditions for each enzyme at 37 degrees C. Biodegradation was analyzed by monitoring the release of radiolabel, by weight change, and by surface analysis using scanning electron microscopy. The polyester urea-urethane was shown to be susceptible to enzymatic degradation above the effect of the buffer control solution by the CE but not by the other enzyme systems as monitored by radiolabel released. In the initial period of incubation, the rate of degradation was increased for all systems, including buffer controls; however, the rates dropped off rapidly by day 28. The change in weight data for the polyester urea-urethane and polyether urea-urethane showed no enzyme-dependent biodegradation above the buffer controls. However, in sodium acetate buffer at pH = 5, the polymers showed a significant weight loss relative to other buffers. In conclusion, this study showed that the biological component responsible for the onset of the biodegradation process is more likely the result of a multitude of biologically mediated compounds acting synergistically, with the process being enhanced by physical parameters such as material dissolution. In addition characterization of surface and bulk chemistry as well as material structure evaluation have been shown to be essential to interpret degradation data.
| Epidermal growth factor modulates prostate cancer cell invasiveness regulating urokinase-type plasminogen activator activity. EGF-receptor inhibition may prevent tumor cell dissemination
Festuccia, C., A. Angelucci, et al. (2005), Thromb Haemost 93(5): 964-75.
Abstract: Urokinase-type plasminogen activator receptor (uPAR) and Epidermal Growth Factor Receptor (EGFR) are ubiquitous receptors involved in the control of a variety of cellular processes frequently found altered in cancer cells. The EGFR has been recently described to play a transduction role of uPAR stimuli, mediating uPA-induced proliferation in highly malignant cells that overexpress uPAR. We compared the uPA production, the presence of uPAR, AR, EGFR and Her2 with the chemotaxis and the Matrigel invasion in ten human PCa cell lines and observed that: (1) the levels of Her2, but not of EGFR, as well as the uPA secretion, cell motility and Matrigel invasion were statistically higher in AR negative than in AR positive PCa cells; (2) the uPA secretion and uPA Rexpression were positively related to Matrigel invasion; (3) the EGF was able to stimulate chemotaxis and Matrigel invasion in a dose-dependent manner; (4) the EGF-induced cell migration was statistically higher inAR negative than in AR positive cells with a similar increase with respect to basal value (about 2.6 fold); (5) the Matrigel invasion was statistically higher in AR negative than in AR positive PCa cells also if the increment of Matrigel invasion after EGF treatment was statistically higher in AR positive respect to AR negative cells; (6) the EGF induced uPA secretion and its membrane uptake through the increment of uPAR; and (7) these effects were blocked by EGFR/Her2 tyrosine kinase inhibitors with IC(50) lower than those needed to inhibit cell proliferation and required PI3K/Akt, MAPK and PI-PLC activities as verified by inhibition experiments. These enzymatic activities were regulated in different manners in PTEN positive and negative cells. In fact, the inhibition of PI3K blocked the EGF-induced invasiveness in PTEN positive cells but not in PTEN negative cells, in which PI3K activity was not influenced by EGFR/Her2 activation, whereas the inhibition of MAPK was able to block the invasive phenomena in both cell types. Taken together, our data suggest that the blockade of EGFR could attenuate the invasive potential of PCa cells. In addition, considering that the EGFR expression is related to higher Gleason grade of PCa and that EGFR levels are increased after anti androgenic therapy, this therapeutic approach could slow down the metastasis formation which represents the most dramatic event of PCa progression.
| Epidermal growth factor-mediated growth control of confluent mammary epithelial cells cultured on artificial basement membrane
Guo, Q., W. Tang, et al. (2005), Int J Mol Med 16(3): 395-9.
Abstract: Local epithelial cell growth is involved in physiological and pathological processes such as development, morphogenesis and carcinogenesis. Cell growth is triggered by the binding of growth factors, such as epidermal growth factor (EGF) to their own receptors (i.e. EGFR). In confluent states, EGFRs are distributed on the basal-lateral side of polarized cells. Therefore, the delivery of EGF to EGFR is thought to be regulated by both tight junctions between the cells, as well as by the basement membrane to which the cells are attached. This research constructed a new culture device with which EGF can be delivered to either the basal-lateral or apical side of confluent epithelial cells that are cultured on an artificial Matrigel basement membrane. Cells in a confluent state started to regrow as a result of incubation with basal medium containing EGF, but not as a result of incubation with apical medium containing EGF. The rate of confluent epithelial cell regrowth depended on EGF concentrations supplied via the basement membrane. In contrast, cells in which tight junctions were disrupted by pre-treatment with EGTA displayed regrowth as a result of incubation with apical medium containing EGF. These results suggest that EGF signaling from the basal-lateral side is regulated by the basement membrane, while that from the apical side is blocked by the tight junctions. Thus, this culture model can be readily used to study the control of local growth of epithelial cells in physiological and pathological processes.
| Epifluorescent video microscopy (EVM) for platelet-biomaterial interactions: elimination of photoactivation and dye effects
McClung, W. G. and I. A. Feuerstein (1992), Biomaterials 13(12): 871-7.
Abstract: The use of two intracellular dyes for epifluorescent video microscopy (EVM) in observations of cell-surface interactions is evaluated and discussed. This methodology permits determinations of cell adhesion, detachment and movement at the surfaces of biomaterials in the presence of flow and physiological haematocrit. Two tests, one which examines for the effect of incident light on platelet adhesion and one which checks for sufficient light for accurate observation of cells, have been designed. Evaluations were made of the adhesion of platelets labelled with the fluorescent dyes mepacrine and acridine orange, used singly and in combination. The use of a number of light level-dye level combinations with glass and several polymers and the addition of a plasma level of fibrinogen did not show any photoactivation effects. This methodology paves the way for longer than previous exposures to light with our system, from 1 min up to 30 min now. Washed platelet suspensions are preferred; these allow for the selective labelling of specific cells and the removal of dye from the surface of the cell.
| Epimerase active domain of Pseudomonas aeruginosa AlgG, a protein that contains a right-handed beta-helix
Douthit, S. A., M. Dlakic, et al. (2005), J Bacteriol 187(13): 4573-83.
Abstract: The polysaccharide alginate forms a protective capsule for Pseudomonas aeruginosa during chronic pulmonary infections. The structure of alginate, a linear polymer of beta1-4-linked O-acetylated d-mannuronate (M) and l-guluronate (G), is important for its activity as a virulence factor. Alginate structure is mediated by AlgG, a periplasmic C-5 mannuronan epimerase. AlgG also plays a role in protecting alginate from degradation by the periplasmic alginate lyase AlgL. Here, we show that the C-terminal region of AlgG contains a right-handed beta-helix (RHbetaH) fold, characteristic of proteins with the carbohydrate-binding and sugar hydrolase (CASH) domain. When modeled based on pectate lyase C of Erwinia chrysanthemi, the RHbetaH of AlgG has a long shallow groove that may accommodate alginate, similar to protein/polysaccharide interactions of other CASH domain proteins. The shallow groove contains a 324-DPHD motif that is conserved among AlgG and the extracellular mannuronan epimerases of Azotobacter vinelandii. Point mutations in this motif disrupt mannuronan epimerase activity but have no effect on alginate secretion. The D324A mutation has a dominant negative phenotype, suggesting that the shallow groove in AlgG contains the catalytic face for epimerization. Other conserved motifs of the epimerases, 361-NNRSYEN and 381-NLVAYN, are predicted to lie on the opposite side of the RHbetaH from the catalytic center. Point mutations N362A, N367A, and V383A result in proteins that do not protect alginate from AlgL, suggesting that these mutant proteins are not properly folded or not inserted into the alginate biosynthetic scaffold. These motifs are likely involved in asparagine and hydrophobic stacking, required for structural integrity of RHbetaH proteins, rather than for mannuronan catalysis. The results suggest that the AlgG RHbetaH protects alginate from degradation by AlgL by channeling the alginate polymer through the proposed alginate biosynthetic scaffold while epimerizing approximately every second d-mannuronate residue to l-guluronate along the epimerase catalytic face.
| Epitope tagging for tracking elastin-like polypeptides
Ong, S. R., K. A. Trabbic-Carlson, et al. (2006), Biomaterials 27(9): 1930-5.
Abstract: Elastin-like polypeptides (ELPs) are a class of biocompatible, non-immunogenic and crosslinkable biomaterials that offer promise for use as an injectable scaffold for cartilage repair. In this study, an oligohistidine (His(6)) epitope tag was incorporated at the N-terminus of an ELP using recombinant DNA techniques to permit tracking without compromising on material biocompatibility. His(6)-tagged ELPs were successfully detected by Western blot analysis and quantified by ELISAs following digestion with trypsin. The mass of His(6) tagged ELP fragments freed from a crosslinked ELP hydrogel after digestion with trypsin correlated highly with hydrogel weight loss, providing evidence of the tag's capability to enable tracking of enzymatic degradation of the ELP hydrogel. The His(6) tag also facilitated recognition of crosslinked ELPs from background staining of articular cartilage. These results suggest that the His(6) epitope tag has the potential to track ELP scaffold loss independently of newly formed tissue mass for evaluating matrix remodeling in vivo.
| Era of new biomaterials in esthetic dentistry
Phillips, R. W. (1987), J Am Dent Assoc Spec No: 7E-12E.
Abstract: Many exciting developments are occurring in esthetic, restorative materials. Today, materials are considered in terms of their biologic effects and tests to predict in vivo behavior are needed. Recently, more nondental manufacturers have begun to introduce products and the number of foreign products has also increased. Dentists and materials scientists are currently interested in: microleakage, bonding mechanisms, dentin-bonding agents, polyacrylic acid systems, and composite resins.
| Erythropoietin signaling promotes invasiveness of human head and neck squamous cell carcinoma
Mohyeldin, A., H. Lu, et al. (2005), Neoplasia 7(5): 537-43.
Abstract: Erythropoietin (Epo) is used for managing anemia in cancer patients. However, recent studies have raised concerns for this practice. We investigated the expression and function of Epo and the erythropoietin receptor (EpoR) in tumor biopsies and cell lines from human head and neck cancer. Epo responsiveness of the cell lines was assessed by Epoetin-alpha-induced tyrosine phosphorylation of the Janus kinase 2 (JAK2) protein kinase. Transmigration assays across Matrigel-coated filters were used to examine the effects of Epoetin-alpha on cell invasiveness. In 32 biopsies, we observed a significant association between disease progression and expression of Epo and its receptor, EpoR. Expression was highest in malignant cells, particularly within hypoxic and infiltrating tumor regions. Although both Epo and EpoR were expressed in human head and neck carcinoma cell lines, only EpoR was upregulated by hypoxia. Epoetin-alpha treatment induced prominent JAK2 phosphorylation and enhanced cell invasion. Inhibition of JAK2 phosphorylation reduced both basal and Epo-induced invasiveness. Our findings support a role for autocrine or paracrine Epo signaling in the malignant progression and local invasiveness of head and neck cancer. This mechanism may also be activated by recombinant Epo therapy and could potentially produce detrimental effects in rhEpo-treated cancer patients.
| Esophageal epithelial cell interaction with synthetic and natural scaffolds for tissue engineering
Beckstead, B. L., S. Pan, et al. (2005), Biomaterials 26(31): 6217-28.
Abstract: As an initial step towards a tissue-engineered esophagus, rat esophageal epithelial cells (REEC) were isolated and characterized for epithelial identity, adhesion protein preference, and in vitro interaction with natural and synthetic scaffolds. The scaffolds consisted of AlloDerm (LifeCell Corporation, Branchburg, NJ), poly(L-lactic acid) (PLLA), poly(lactic-co-glycolic) acid (75:25) (PLGA75), poly(lactic-co-glycolic) acid (50:50) (PLGA50), and polycaprolactone/poly(L-lactic acid) (50:50) (PCL/PLLA). Various factors-including calcium concentration, scaffold composition, and pore size--were evaluated for their influence on epithelial growth and differentiation. By day 18, keratinocytes seeded on AlloDerm cultured under high Ca(++) (1.5mm) conditions showed a proliferating basal cell layer, epithelial stratification (5--6 layers) and a thick keratin layer. The synthetic scaffolds (PLGA, PLLA, PCL/PLLA) also showed complete surface coverage, regions of proliferating basal cells, and evidence of stratification (2--3 layers) and keratinization. The highly porous nature of the synthetic scaffolds, however, limited the formation of a continuous epithelial layer and resulted in a lack of overall spatially-defined differentiation. In conclusion, rat esophageal epithelial cells were successfully isolated and characterized, with cells seeded on AlloDerm showing superior epithelial organization and stratification compared to synthetic scaffolds. Modification of the synthetic scaffold's surface properties and pore size may be necessary to mimic epithelial behavior on natural scaffolds.
| Essential role for Galpha13 in endothelial cells during embryonic development
Ruppel, K. M., D. Willison, et al. (2005), Proc Natl Acad Sci U S A 102(23): 8281-6.
Abstract: Toward identifying the roles of protease-activated receptor-1 (PAR1) and other G protein-coupled receptors important for vascular development, we investigated the role of Galpha13 in endothelial cells in the mouse embryo. LacZ inserted into Galpha13 exon 1 was highly expressed in endothelial cells at midgestation. Endothelial-specific Galpha13 knockout embryos died at embryonic days 9.5-11.5 and resembled the PAR1 knockout. Restoration of Galpha13 expression in endothelial cells by use of a Tie2 promoter-driven Galpha13 transgene rescued development of endothelial-specific Galpha13 knockout embryos as well the embryonic day 9.5 vascular phenotype in Galpha13 conventional knockouts; transgene-positive Galpha13-/- embryos developed for several days beyond their transgene-negative Galpha13-/- littermates and then manifested a previously uncharacterized phenotype that included intracranial bleeding and exencephaly. Taken together, our results suggest a critical role for Galpha13 in endothelial cells during vascular development, place Galpha13 as a candidate mediator of PAR1 signaling in this process, and reveal roles for Galpha13 in other cell types in the mammalian embryo.
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