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Biotinylated gene therapy vectors.

The avidin-biotin system is a fundamental technology in biomedicine for immunolocalisation, imaging, nucleic acid blotting and protein labelling. This technology has recently been adapted for use in gene therapy vector applications to add proteins or cell-targeting ligands to non-viral and viral vectors. Two biotinylation technologies are being used in these applications: chemical biotinylation and metabolic biotinylation. In chemical biotinylation, reactive alkylating agents couple biotin to proteins by random covalent attachment to amino acid side chains. In metabolic biotinylation, proteins are genetically engineered with a biotin acceptor peptide (BAP), such that they are covalently biotinylated by cellular biotin ligases during viral vector production. Both technologies show promise for cell-targeting in vitro and in vivo, and for ligand screening applications. Metabolic biotinylation has the added feature of allowing viruses, vectors and vaccines to be produced from cells already biotinylated, thereby allowing them to purified by affinity chromatography on monomeric avidin columns.

Animals↗

Formation of mineralizing osteoblast cultures on machined, titanium oxide grit-blasted, and plasma-sprayed titanium surfaces.

Altering osseous responses at implant surfaces to enhance bone is a current goal of clinical therapy. Cell culture may be used to investigate surface-dependent responses of bone-forming cells. In this report, the ability of primary fetal bovine mandibular osteoblast cultures to form a mineralizing matrix on machined, titanium plasma-sprayed, and titanium oxide grit-blasted surfaces has been compared. Immunohistochemical markers associated with bone formation were used to define the differentiated state of the formed matrix using qualitative light microscopy, and von Kossa staining was used to demonstrate the presence of mineralization within this matrix. Compared to either titanium oxide grit-blasted or machined surfaces, titanium plasma-sprayed surfaces displayed a unique pattern of mineralized matrix formation. Scanning electron microscopy further revealed that each surface accumulated unique organic and inorganic deposits during matrix formation, suggesting that surface-dependent physicochemical and biochemical conditioning of implant surfaces takes place. Surface topographic features of commercially pure titanium substrates can alter cultured osteoblast extracellular matrix formation and mineralization. Similar molecular and cellular assessment of in vivo responses to implant surface topography may contribute to improved engineering of endosseous implants.

Animals↗

The SynerGraft valve: a new acellular (nonglutaraldehyde-fixed) tissue heart valve for autologous recellularization first experimental studies before clinical implantation.

The durability of current bioprosthetic heart valves is diminished by glutaraldehyde-associated leaflet calcification or by the associated absence of a cellular component capable of repair of wear-related damage. As a novel tissue engineering approach to improving replacement heart valve durability, we have developed a decellularization process to replace the use of cross-linking to limit xenograft antigenicity. The effectiveness of this process was assessed in a weanling sheep right ventricular outflow tract reconstruction model where valve function, calcification, and recellularization were examined. Porcine aortic valves were decellularized by a process designed to remove all histologically demonstrable leaflet cells. Stentless, bioprosthetic valves were fabricated from acellular tissues, cryopreserved, sterilized, and then implanted as pulmonary valve replacements in 4- to 6-month old female Suffolk sheep. Sheep aortic valves were implanted as allograft control subjects. After 150 days, the grafts were explanted and assessed histologically and by atomic absorption spectrophotometry for calcium content. All valves were hemodynamically functional at explant. Histological examination showed intact leaflets with in-growth of host fibroblastoid cells in all explanted porcine valves and no evidence of calcification. Porcine leaflet calcium content was unchanged over the duration of the implant (1.0+/-1.2 vs 1.5+/-1.8 mg/g dry weight, P = ns). Decellularization can stabilize xenogenic heart valves. Lack of calcification of acellular aortic leaflets suggests that prolonged durability of such valves is attainable without the use of cross-linking agents. The repopulation of the leaflet matrix offers additional promise of durability based on revitalization of the graft in vivo.

Animals↗

Expression of adhesion molecules and collagen on rat chondrocyte seeded into alginate and hyaluronate based 3D biosystems. Influence of mechanical stresses.

Chondrocytes use mechanical signals, via interactions with their environment, to synthesize an extracellular matrix capable to withstanding high loads. Most chondrocyte-matrix interactions are mediated via transmembrane receptors such as integrins or non-integrins receptors (i.e. annexin V and CD44). The aim of this study was to analyze, by flow cytometry, the adhesion molecules (alpha5/beta1 integrins and CD44) on rat chondrocytes seeded into 3D biosystem made of alginate and hyaluronate. These biosystems were submitted to mechanical stress by knocking the biosystems between them for 48 hours. The expression of type I and type II collagen was also evaluated. The results of the current study showed that mechanical stress induced an increase of type II collagen production and weak variations of alpha5/beta1 receptors expression no matter what biosystems. Moreover, our results indicated that hyaluronan receptor CD44 expression depends on extracellular matrix modifications. Thus, these receptors were activated by signals resulted from cell environment variations (HA addition and modifications owing to mechanical stress). It suggested that this kind of receptor play a crucial role in extracellular matrix homeostasis. Finally, on day 24, no dedifferentiation of chondrocytes was noted either in biosystems or under mechanical stress. For all biosystems, the neosynthesized matrix contained an important level of collagen, which was type II, whatever biosystems. In conclusion, it appeared that the cells, under mechanical stress, maintained their phenotype. In addition, it seems that, on rat chondrocytes, alpha5/beta1 integrins did not act as the main mechanoreceptor (as described for human chondrocytes). In return, hyaluronan receptor CD44 seems to be in relation with matrix composition.

Alginates↗

Ex vivo adipose tissue engineering by human marrow stromal cell seeded gelatin sponge.

The limitation of current clinical treatment for restoration extended defects of soft tissue associated with trauma, tumor resections, and congenital deformities are well known. This study demonstrates that human bone marrow stromal cells (MSCs) can be utilized to tissue engineer adipose tissue for therapeutic purposes. Adipogenic potentials of monolayer-cultured human MSCs were evaluated by biochemical measurement of an adipogenic differentiation marker (glycerol-3-phosphate dehydrogenase, G-3-PDH) and cellular morphology. After preparation by seeding human MSCs on a 3-dimensional gelatin sponge and exposure to adipogenic differentiation medium, the ex vivo tissue-engineered adipose constructs were assessed histomorphologically and biochemically. Lipid droplets accumulated and expanded within the constructs accompanied by a significant increase of G-3-PDH activity. The present study indicates that bone MSCs could be a cell resource in tissue engineering adipose tissue, while gelatin sponge could be a good scaffold in this approach to improve the outcome of clinical treatment.

Adipose Tissue↗

Harnessing the ubiquitination machinery to target the degradation of specific cellular proteins.

The functional characterization of a specific gene, or its protein product, often relies on assessing the consequences of its elimination, usually accomplished by gene knockout, ribozyme, antisense, or RNA-mediated interference (RNAi) technologies. The selective degradation of cellular proteins is mediated primarily by the ubiquitin-proteasome pathway. Manipulation of the ubiquitin-dependent proteolytic machinery to eliminate specific gene products at the protein level has been previously attempted with some success in vitro; however, the in vivo efficacy of this approach has not yet been achieved. Here we report successful engineering of the substrate receptor of a major ubiquitin-proteolytic machinery to direct the degradation of otherwise stable cellular proteins both in yeast and in mammalian cells.

Animals↗

Comparison of selective attachment and growth of smooth muscle cells on gelatin- and fibronectin-coated micropatterns.

Tissue engineering research has been on going for many years, people are making all the effort to explore the cell functions in cellular level and even in molecular level. Making the cells functional in an in vitro environment is a preliminary goal for the implantation and repair of complicated tissues/organs. Fabricating artificial ECM to mimic the in vivo environment is an essential approach in tissue engineering. The work in this paper is to study how rat aorta smooth muscle cells (RASMCs) behave in two engineered cell culture scaffolds: gelatin- and fibronectin (FN)-coated micropatterns. The investigation on the initial attachment and further growth of SMCs cultured on gelatin- and FN-coated micropatterns was addressed. This study focused on both the characterization of gelatin and fibronectin assembly properties and cell responses to these two protein-coated micropatterns. Thin film patterns with gelatin and fibronectin coatings were fabricated on microscope glass slides using photolithography, electrostatic layer-by-layer self-assembly and lift-off (LbL-LO) technologies. In this work, the scaffolds were built up by commonly used polyelectrolyte materials and proteins through LbL process, containing cationic poly(diallyldimethylammonium chloride) (PDDA), poly(allylamine hydrochloride) (PAH), anionic poly(sodium 4-styrenesulfonate) (PSS), gelatin and fibronectin. The resulting polyelectrolyte thin films were characterized by contact angle (CA), quartz crystal microbalance (QCM), atomic force microscopy (AFM), and fluorescence microscopy. CA measurement shows the consistent hydrophylicity of gelatin surfaces in different number of layers with LbL deposition method. Different from our previous QCM measurement of gelatin, fibronectin does not show high electrostatic attraction to either positively or negatively charged polyelectrolytes, although it can be weakly assembled to both polyelectrolyte surfaces. AFM images show Gelatin- and FN-coated micropatterns are around 50-60 nm thick. RASMCs were cultured on these gelatin- and FN-coated micropatterns. It was observed that, for the cells cultured on gelatin-coated micropatterns, they initially landed on the gelatin-coated surface, not on the PDDA-coated surface in between. But further growth of the cells was affected by the shape of the patterns: strip pattern limited cell growth beyond the patterns, but square patterns could not. While, it was found interestingly, for the cells cultured on FN-coated micropatterns, SMCs initially landed on PDDA-coated surface, and then migrated to FN-coated both square and strip patterns. These findings indicate that both gelatin and fibronectin are adhesive proteins, but they have different effects on the initial attachment and later growth for SMCs.

Animals↗

Fabrication and characterization of six electrospun poly(alpha-hydroxy ester)-based fibrous scaffolds for tissue engineering applications.

The most common synthetic biodegradable polymers being investigated for tissue engineering applications are FDA approved, clinically used poly(alpha-hydroxy esters). To better assess the applicability of the electrospinning technology for scaffold fabrication, six commonly used poly(alpha-hydroxy esters) were used to prepare electrospun fibrous scaffolds, and their physical and biological properties were also characterized. Our results suggest that specific, optimized fabrication parameters are required for each polymer to produce scaffolds that consist of uniform structures morphologically similar to native extracellular matrix. Scanning electron microscopy (SEM) revealed a highly porous, three-dimensional structure for all scaffolds, with average fiber diameter ranging from 300nm to 1.5microm, depending on the polymer type used. The poly(glycolic acid) (PGA) and poly(d,l-lactic-co-glycolic acid 50:50) (PLGA5050) fibrous structures were mechanically stiffest, whereas the poly(l-lactic acid) (PLLA) and poly(epsilon-caprolactone) (PCL) scaffolds were most compliant. Upon incubation in physiological solution, severe structural destruction due to polymer degradation was found in the PGA, poly(d,l-lactic acid) (PDLLA), PLGA5050, and poly(d,l-lactic-co-glycolic acid 85:15) (PLGA8515) fibrous scaffolds, whereas PLLA and PCL fibrous scaffolds maintained a robust scaffold structure during the same time period, based on macroscopic and SEM observations. In addition, PLLA scaffolds supported the highest rate of proliferation of seeded cells (chondrocytes and mesenchymal stem cells) than other polymeric scaffolds. Our findings showed that PLLA and PCL based fibrous scaffolds exhibited the most optimal structural integrity and supported desirable cellular response in culture, suggesting that such scaffolds may be promising candidate biomaterials for tissue engineering applications.

Animals↗

Expression and function of the integrin alpha9beta1 in bovine aortic valve interstitial cells.

BACKGROUND AND AIM OF THE STUDY: Aortic valve interstitial cells (VIC), the most prevalent valve leaflet cells, have not been well studied. However, recent interest in constructing tissue-engineered living heart valves has provided motivation to further an understanding of the molecular and cellular biology of VIC. Since cell-extracellular matrix interactions are critical for tissue morphogenesis, adhesive interactions and integrin function in VIC were investigated. METHODS: Bovine and baboon VIC were isolated and characterized by morphology, cytoskeletal protein expression and integrin expression. The interaction of VIC integrin alpha9beta1 with osteopontin, a ligand known to be up-regulated in the wounded valve, was examined. The ability of bovine VIC alpha9beta1 to mediate adhesion, focal contact formation, migration and proliferation when plated on the immobilized osteopontin substrates, was investigated. RESULTS: Cultured bovine VIC possessed characteristics of both fibroblasts and smooth muscle cells. Like fibroblasts, bovine VIC had an elongated morphology with long cytoplasmic processes. Like smooth muscle cells, bovine VIC expressed alpha-smooth muscle actin and SM22alpha. Using fluorescent flow cytometry, the surface expression of integrins alpha9beta1 and alpha(v)beta3 in bovine VIC and integrins alpha1beta1, alpha2beta1, and alpha5beta1 in baboon VIC was identified. Expression of alpha9beta1 in cultured VIC and in native valve leaflets was further confirmed by Western blot and RT-PCR analysis. Bovine VIC were found to adhere to the 30N fragment of osteopontin in an alpha9beta1-dependent manner, and this interaction was mediated through the SVVYGLR motif. Bovine VIC also formed focal contacts through the alpha9beta1 integrin, but osteopontin (30N) did not stimulate migration or proliferation of bovine VIC through the integrin alpha9beta1. CONCLUSION: Integrin alpha9beta1 appears to be predominantly involved in controlling anchorage rather than movement or proliferation, in bovine VIC. For tissue engineering, knowledge of the VIC integrin profile can be applied to the rational design of scaffolds with the appropriate ligands for tissue formation. The VIC a9beta1-SVVYGLR interaction could be exploited to promote cell anchorage within a tissue engineering scaffold.

Actins↗

Reflectance confocal microscopy for characterization of mammary ductal structures and development of neoplasia in genetically engineered mouse models of breast cancer.

The earliest steps of breast cancer begin with aberrations in mammary ductal structure. Techniques that enable an investigator to image in situ and then analyze the same tissue using biochemical tools facilitates identification of genetic networks and signaling pathways active in the imaged structure. Cellular confocal microscopy (VivaCell-TiBa, Rochester, New York) is used to image mammary ductal structures and surrounding vasculature in situ in intact wild-type and genetically engineered mice that develop ER alpha-initiated ductal carcinoma in situ (DCIS) and ER alpha-driven invasive mammary cancer. In wild-type mice, normal mammary ductal structures that appear from puberty through lactation are visualized and serially sectioned optically, and a developmental atlas is created. Altering tissue preparation enabled visualization of the vasculature surrounding the ductal structures. In the genetically engineered mice, aberrant mammary ductal structures and cancers are imaged and compared to corresponding normal structures. Different preparation techniques are able to preserve tissue for routine histological analyses and RNA isolation. Comparative studies demonstrate that reflectance confocal imaging provides more cellular detail than carmine-alum-stained mammary gland whole mounts and equivalent detail with hematoxylin and eosin stained tissue sections. In summary, reflectance confocal microscopy is a tool that can be used to rapidly and accurately analyze mammary gland structure.

Adenocarcinoma↗

[Experimental study of periosteal osteoblasts adhesion to artificial bone scaffolds based on rapid prototype].

OBJECTIVE: To study the biocompatibility of bone engineering scaffolds designed and fabricated by CAD and Rapid Prototyping techniques. METHODS: Infant rat calvarias osteoblasts were isolated and expanded in vitro and the cells (2nd passage) were seeded onto scaffolds with porosity 80%, 90%, 95% at a density of 2.06 x 10(9)/L. Cell adhesion number and morphology were measured with SEM after 4 days, 10 days co-culture. RESULTS: (1) The osteoblasts' adhesion amounts increased with culture time in three porosity group (P < 0.05), but the increase were different among three groups, 80% group was 0.35 x 10(5), 90% group was 2.84 x 10(5); (2) Through SEM observations, it showed that osteoblasts adhered to all scaffolds well. CONCLUSION: The scaffolds designed and fabricated by CAD and rapid prototyping own a good cellular biocompatibility. The results suggest the feasibility of using such scaffold fabricating method for bone tissue engineering research and clinical therapy.

Animals↗

Use of rhBMP-2 activated chitosan films to improve osseointegration.

Considering the design and development of biomaterials used in tissue engineering, not only is it important that they are biocompatible but also that they induce the desired cellular response for tissue regeneration. Chitosan, a biocompatible and bioresorbable polymer of N-acetylglucosamine and glucosamine is used in our work combined with recombinant human BMP-2 (rhBMP-2), a potentially useful activation factor for bone repair. In this way, we try to combine the biological and filmogenic properties of this biopolymer with the osseoinductive ability of the rhBMP-2. Results showed that the chitosan films employed, without and with rhBMP-2 activation, are able to support cellular growth and proliferation on them and that only the rhBMP-2 activated ones are able to differentiate from a myoblastic mouse cell line (C2C12) toward osteoblastic phenotype. Osseoinduction properties of rhBMP-2 activated films persist for a long storage time. The in vivo experiments performed confirm the expectative created by the in vitro results obtained and are an indication that rhBMP-2 activated chitosan films could be a very attractive biomaterial for the enhancement of osseointegration of surgical prostheses and implants and for the purpose of tissue engineering bone regeneration.

Animals↗

Roles of hemodynamic forces in vascular cell differentiation.

The pulsatile nature of blood flow is a key stimulus for the modulation of vascular cell differentiation. Within the vascular media, physiologic stress is manifested as cyclic strain, while in the lumen, cells are subjected to shear stress. These two respective biomechanical forces influence the phenotype and degree of differentiation or proliferation of smooth muscle cells and endothelial cells within the human vasculature. Elucidation of the effect of these mechanical forces on cellular differentiation has led to a surge of research into this area because of the implications for both the treatment of atherosclerotic disease and the future of vascular tissue engineering. The use of mechanical force to directly control vascular cell differentiation may be utilized as an invaluable engineering tool in the future. However, an understanding of the role of hemodynamics in vascular cell differentiation and proliferation is critical before application can be realized. Thus, this review will provide a current perspective on the latest research and controversy behind the role of hemodynamic forces for vascular cell differentiation and phenotype modulation. Furthermore, this review will illustrate the application of hemodynamic force for vascular tissue engineering and explicate future directions for research.

Animals↗

Engineering skeletal myoblasts: roles of three-dimensional culture and electrical stimulation.

Immature skeletal muscle cells, or myoblasts, have been used in cellular cardiomyoplasty in attempts to regenerate cardiac muscle tissue by injection of cells into damaged myocardium. In some studies, muscle tissue within myoblast implant sites may be morphologically similar to cardiac muscle. We hypothesized that identifiable aspects of the cardiac milieu may contribute to growth and development of implanted myoblasts in vivo. To test this hypothesis, we designed a novel in vitro system to mimic some aspects of the electrical and biochemical environment of native myocardium. This system enabled us to separate the three-dimensional (3-D) electrical and biochemical signals that may be involved in myoblast proliferation and plasticity. Myoblasts were grown on 3-D polyglycolic acid mesh scaffolds under control conditions, in the presence of cardiac-like electrical current fluxes, or in the presence of culture medium that had been conditioned by mature cardiomyocytes. Cardiac-like electrical current fluxes caused increased myoblast number in 3-D culture, as determined by DNA assay. The increase in cell number was due to increased cellular proliferation and not differences in apoptosis, as determined by proliferating cell nuclear antigen and TdT-mediated dUTP nick-end labeling. Cardiomyocyte-conditioned medium also significantly increased myoblast proliferation. Expression of transcription factors governing differentiation along skeletal or cardiac lineages was evaluated by immunoblotting. Although these assays are qualitative, no changes in differentiation state along skeletal or cardiac lineages were observed in response to electrical current fluxes. Furthermore, from these experiments, conditioned medium did not appear to alter the differentiation state of skeletal myoblasts. Hence, cardiac milieu appears to stimulate proliferation but does not affect differentiation of skeletal myoblasts.

Animals↗

Merging fields: stem cells in neurogenesis, transplantation, and disease modeling.

Traditionally, applied stem cell research has been segregating into strategies aiming at endogenous repair and cell transplantation. Recent advances in both fields have unraveled unexpected potential for synergy between these disparate fields. The increasing dissection of the step-wise integration of adult-born neurons into an established brain circuitry provides a highly informative blueprint for the functional incorporation of grafted neurons into a host brain. On the other hand, in vitro recapitulation of developmental differentiation cascades permits the de novo generation of various neural cell types from pluripotent embryonic stem (ES) cells. Advanced tools in stem cell engineering enable not only genetic selection and instruction of disease-specific donor cells for neural replacement but also the exploitation of stem cells as transgenic cellular model systems for human diseases. In a comparative approach we here illuminate the functional integration of neurons derived from endogenous and transplanted stem cells, the evolving technologies for advanced stem cell engineering and the impact of cloned and mutated stem cells on disease modeling.

Adult↗

The biotechnology and applications of antibody engineering.

The exquisite specificity of monoclonal antibodies (MAb) has long provided the potential for creating new reagents for the in vivo delivery of therapeutic drugs or toxins to defined cellular target sites or improved methods of diagnosis. However, many difficulties associated with their production, affinity, specificity, and use in vivo have largely confined their application to research or in vitro diagnostics. This situation is beginning to change with the recent developments in the applied molecular techniques that allow the engineering of the genes that encode antibodies rather than the manipulation of the intact antibodies themselves. Techniques, such as the polymerase chain reaction, have provided essential methods with which to generate and modify the genetic constituents of antibodies, allow their conjugation to toxins or drugs, provide ways of humanizing murine antibodies, and allow discrete modular antigen binding components to be produced. More recent developments of in vitro expression systems and powerful phage surface display technologies will without doubt play a major role in future antibody engineering and in the successful development of new diagnostic and therapeutic antibody-based reagents.

Animals↗

Control of attachment, morphology, and proliferation of skeletal myoblasts on silanized glass.

Generating skeletal muscle in vitro is an attractive approach to overcome problems associated with autologous transfer of muscle and donor site morbidity during plastic surgery. Such tissue engineering requires application of biomaterials that selectively control the attachment, morphology, and proliferation of muscle progenitor ("satellite") cells. This study examined the initial attachment, morphological characteristics, and proliferative behavior of murine C2C12 myoblasts on glass substrata derivatized with self-assembled monolayers (SAMs) of the organosiloxanes N-(2-aminoethyl)(3-aminopropyl)trimethoxysilane (EDA) and tridecafluoro-1,1,2,2-tetrahydrooctyl-1-dimethylchlorosil ane (13F). The fraction of myoblasts resisting detachment upon rinsing was greater on EDA than on 13F. Application of a quantitative moments-based analysis of cell morphology demonstrated that projected area and two size-invariant metrics of shape (extension and dispersion) for these cells were greater for EDA than for 13F. Myoblasts also proliferated faster on EDA than on 13F. These data indicate that EDA-derivatized glass provides a superior substratum for myoblast culture compared to 13F-derivatized glass. Understanding myoblast behavior on these biomaterials that promotes contrasting cellular responses is the first step toward using patterned SAMs to control myotube alignment for tissue engineering skeletal muscle.

Alkanes↗

[Study on the osteogenesis ability of co-culturing bone marrow stromal cells (BMSCs) and small intestinal submucosa].

PURPOSE: Using co-culturing of bone marrow stromal cells (BMSCs) and small intestinal submucosa (SIS), to evaluate the cellular compatibility and the osteogenesis ability as well as the feasibility of SIS to serve as a scaffold in tissue engineering. METHODS: Bone marrow was aspirated from the healthy adult goat and culture-expanded in vitro by the method of total marrow. The third passage cells were transplanted into SIS after being induced to differentiate into osteoblasts for 4 days and then seeded into SIS for 3 to 10 days. BMSCs alone were cultured at the same condition to act as controls. The cellular morphology and function (attachment, proliferation and differentiation) and the ectopia osteogenesis in vivo were assessed separately by means of phase contrast microscope, SEM and MTT, ALP activity, histology detection. The difference between the two groups were analyzed by Student's t test statistically. RESULTS: The BMSCs could adhere to SIS and proliferate and grow on the surface of SIS normally. The cellular activity and function were not affected by SIS, no statistical difference was found between the two groups (P>0.05). The BMSCs/SIS compounds had good abilities of ectopia osteogenesis in vivo, and with time going on new bone formation increased. There was no bone formation in the control group. The endochondral bone formatin was the main pattern of osteogenesis. CONCLUSIONS: As a natural, absorbable, acellular scaffold, SIS is biocompatible and can be used as a tissue engineering scaffold. And for a membrane feature, there is the possibility to construct tissue engineered bone membrane with SIS.

Adult↗