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At least 253 records · Page 14Linked to original sources

PubMed2005

In vivo conditioning of tissue-engineered heart muscle improves contractile performance.

The ability to engineer cardiac tissue in vitro is limited by the absence of a vasculature. In this study we describe an in vivo model which allows neovascularization of engineered cardiac tissue. Three-dimensional cardiac tissue, termed "cardioids," was engineered in vitro from the spontaneous delamination of a confluent monolayer of cardiac cells. Cardioids were sutured onto a support framework and then implanted in a subcutaneous pocket in syngeneic recipient rats. Three weeks after implantation, cardioids were recovered for in vitro force testing and histological evaluation. Staining for hematoxylin and eosin demonstrated the presence of viable cells within explanted cardioids. Immunostaining with von Willebrand factor showed the presence of vascularization. Electron micrographs revealed the presence of large amounts of aligned contractile proteins and a high degree of intercellular connectivity. The peak active force increased from an average value of 57 microN for control cardioids to 447 microN for explanted cardioids. There was also a significant increase in the specific force. There was a significant decrease in the time to peak tension and half relaxation time. Explanted cardioids could be electrically paced at frequencies of 1-5 Hz. Explanted cardioids exhibited a sigmoidal response to calcium and positive chronotropy in response to epinephrine. As the field of cardiac tissue engineering progresses, it becomes desirable to engineer larger diameter tissue equivalents and to induce angiogenesis within tissue constructs. This study describes a relatively simple in vivo model, which promotes the neovascularization of tissue-engineered heart muscle and subsequent improvement in contractile performance.

Animals↗

PubMed2004

Global gene expression of cells attached to a tissue engineering scaffold.

A goal of tissue engineering is to produce a scaffold material that will guide cells to differentiate and regenerate functional replacement tissue at the site of injury. Little is known about how cells respond on a molecular level to tissue engineering scaffold materials. In this work we used oligonucleotide microarrays to interrogate gene expression profiles associated with cell-biomaterial interactions. We seeded collagen-glycosaminoglycan meshes, a widely used tissue engineering scaffold material, with human IMR-90 fibroblasts and compared transcript levels with control cells grown on tissue culture polystyrene. Genes involved in cell signaling, extracellular matrix remodeling, inflammation, angiogenesis and hypoxia were all activated in cells on the collagen-GAG mesh. Understanding the impact of a scaffold on attached cells will facilitate the design of improved tissue engineering materials.

CD55 Antigens↗

PubMed2002

Gene transfer of a human insulin-like growth factor I cDNA enhances tissue engineering of cartilage.

The repair of articular cartilage lesions remains a clinical problem. Two novel approaches to cartilage formation, gene transfer and tissue engineering, have been limited by short-term transgene expression in transplanted chondrocytes and inability to deliver regulatory signals to engineered tissues according to specific temporal and spatial patterns. We tested the hypothesis that the transfer of a cDNA encoding the human insulin-like growth factor I (IGF-I) can provide sustained gene expression in cell-polymer constructs in vitro and in vivo and enhance the structural and functional properties of tissue-engineered cartilage. Bovine articular chondrocytes genetically modified to overexpress human IGF-I were seeded into polymer scaffolds, cultured in bioreactors in serum-free medium, and implanted subcutaneously in nude mice; constructs based on nontransfected or lacZ-transfected chondrocytes served as controls. Transgene expression was maintained throughout the duration of the study, more than 4 weeks in vitro followed by an additional 10 days either in vitro or in vivo. Chondrogenesis progressed toward the formation of cartilaginous tissue that was characterized by the presence of glycosaminoglycans, aggrecan, and type II collagen, and the absence of type I collagen. IGF-I constructs contained increased amounts of glycosaminoglycans and collagen and confined-compression equilibrium moduli as compared with controls; all groups had subnormal cellularity. The amounts of glycosaminoglycans and collagen per unit DNA in IGF-I constructs were markedly higher than in constructs cultured in serum-supplemented medium or native cartilage. This enhancement of chondrogenesis by spatially defined overexpression of human IGF-I suggests that cartilage tissue engineering based on genetically modified chondrocytes may be advantageous as compared with either gene transfer or tissue engineering alone.

Animals↗

PubMed2000

Tissue engineering of urinary organs.

Tissue engineering can serve as an alternative treatment for a malfunctioning or lost organ. Isolated and expanded cells adhere to a temporary scaffold, proliferate, and secrete their own extracellular matrices (ECM) replacing the biodegrading scaffold. The genitourinary system, composed of the kidney, ureter, bladder, urethra, and genital organs, is exposed to a variety of possible injury sites from the time of fetal development. All the urinary organs are mainly composed of smooth muscle and uroepithelial cells and which may be approached by tissue engineering techniques. A large number of materials, including naturally-derived and synthetic polymers have been utilized to fabricate prostheses for the genitourinary system. Usually, whenever there is a lack of native urologic tissue, reconstruction is considered with native non-urologic tissue, such as, gastrointestinal segments, or skin or mucosa from multiple body sites. Engineering tissues using selective cell transplantation may provide a means to create functional new genitourinary tissues. This review concerns urinary tissues reconstructed with bladder uroepithelial cells and smooth muscle cells (SMCs) implanted on biodegradable polymer matrices.

Animals↗

PubMed2006

Dielectrophoresis based-cell patterning for tissue engineering.

Engineering functional tissues and organs in vitro is considered integral to regenerative medicine. Many recent cell patterning technique developments position cells at a pre-designated pattern to improve tissue engineering efficiency and quality and to facilitate 3-D cell-cell interaction exploration. Among these techniques, dielectrophoresis (DEP)-based cell patterning advantageously offers speed, ease of operation, low degree of cell damage, and precision. This article reviews recent advances in DEP-based patterning techniques, including electrode design, suitable buffer and hydrogel, effects of the electric current to cells, combination potential with other techniques, as well as efforts to generate 3-D tissues.

Animals↗

PubMed2000

Advances in biotechnology for tissue engineering of bone.

Tissue engineering is a rapidly developing field applying the disciplines of cell biology, developmental biology, molecular biology and biomimetic engineering to regenerate new tissues for replacement therapies in clinical contexts. To aid in the elicitation and reiteration of the processes of morphogenesis of tissues, the cascade of chemotaxis of progenitor cells, their differentiation and pattern formation is redeployed in postnatal tissues, effected by a variety of ever-increasing morphogens and biomaterials. The extensive recent progress in elucidating the molecular biology of BMPs and their receptors shall aid in promoting and extending the great operational future of this field. Although the BMP family of proteins and osteogenesis have been the subject of several recent reviews, we focus here on their activity in primates and on the novel localization of BMPs in the cerebellum and other areas of the nervous system, and the "mosaicism" of their localisation in the periodontal tissues followed by a discussion on the use of BMPs in periodontal regeneration. Lastly, we report on the unique osteoinductive activity of TGF-beta proteins in heterotopic sites of primates and their synergistic interaction with a recombinant human BMP, and finally we present unique data on novel biomaterials endowed with intrinsic osteoinductive activity, capable of initiating de novo bone formation in heterotopic sites even in the absence of exogenously applied BMPs, and the results of a clinical trial in humans using naturally-derived BMPs.

Animals↗

PubMed2005

Polyesterurethane foam scaffold for smooth muscle cell tissue engineering.

Reconstruction of the genitourinary tract, using engineered urological tissues, requires a mechanically stable biodegradable and biocompatible scaffold and cultured cells. Such engineered autologous tissue would have many clinical implications. In this study a highly porous biodegradable polyesterurethane-foam, DegraPol was evaluated with tissue engineered human primary bladder smooth muscle cells. The cell-polymer constructs were characterized by histology, scanning electron microscopy, immunohistochemistry and proliferation assays. Smooth muscle cells grown on DegraPol showed the same morphology as when grown on control polystyrene surface. Positive immunostaining with alpha smooth muscle actin indicated the preservation of the specific cell phenotype. Micrographs from scanning electron microscopy showed that the cells grew on the foam surface as well as inside the pores. In addition they grew as cell aggregates within the foam. The smooth muscle cells proliferated on the Degrapol; however, proliferation rate decreased due to apoptosis with time in culture. This study showed that Degrapol has the potential to be used as a scaffold.

Apoptosis↗

PubMed2002

Principals of neovascularization for tissue engineering.

The goals in tissue engineering include the replacement of damaged, injured or missing body tissues with biological compatible substitutes such as bioengineered tissues. However, due to an initial mass loss after implantation, improved vascularization of the regenerated tissue is essential. Recent advances in understanding the process of blood vessel growth has offered significant tools for therapeutic neovascularization. Several angiogenic growth factors including vascular endothelial cell growth factor (VEGF) and basic fibroblast growth factor (bFGF) were used for vascularization of ischemic tissues. Three approaches have been used for vascularization of bioengineered tissue: incorporation of angiogenic factors in the bioengineered tissue, seeding endothelial cells with other cell types and prevascularization of matrices prior to cell seeding. This paper reviews the process of blood vessel growth and tissue vascularization, and discuss strategies for efficient vascularization of engineered tissues.

Animals↗

PubMed2004

Differential distribution of elastic tissue in human natural skin and tissue-engineered skin.

Tissue-engineered skins (TES), manufactured by epidermal and dermal equivalents, are now being used in biological, pharmacotoxicological and clinical applications. It is thus interesting to know to what extent artificial organs are similar to natural counterparts. Elastic fibres are important constituents of the extracellular matrix of natural skin (NS). The aim of our study was to investigate the possible occurrence and distribution of elastic tissue in a model of human TES using different histochemical techniques, including classical Orcein and Fuchsin-Resorcin methods and immunohistochemistry, at both light and electron microscopical levels. Immunoperoxidase and high resolution immunogold methods were used. In NS, classical staining techniques and elastin-immunohistochemistry revealed a well-organized network of elastic fibres. High resolution immunocytochemistry revealed an intense labelling in the amorphous component of elastic fibres. Fibres of different diameters were immunostained. In TES, no stained elastic fibres were observed using classical staining techniques, and the interpretation of immunoperoxidase observations was not clear-cut. In contrast, immunogold staining at the electron microscopical level provided specific labelling of elastin-like immunoreactive material in the dermal equivalent. However, ultrastructural immunocytochemistry revealed that elastic tissue organization in TES was poor compared to that in NS. This study demonstrates that elastic fibres are a component of the extracellular matrix in this model of TES and suggests that fibroblasts of the dermal equivalent are engaged in matrix secretion. Nevertheless, the level of extracellular matrix organization in TES is low compared to NS. Moreover, this study also suggests that different models of bilayered TES may differ with respect to extracellular matrix organization. These aspects should be considered when TES is used in biological and pharmacotoxicological studies. A better understanding of the factors influencing extracellular matrix formation in TES is necessary to achieve further development of skin generation in vitro.

Cells, Cultured↗

PubMed1996

Femoral shaft reconstruction using tissue-engineered growth of bone.

Tissue engineering is an interdisciplinary field that applies the principles and methods of engineering and the life sciences to the development of biologic substitutes. Bovine periosteum-derived cells were cultivated in vitro, put onto bioresorbable polymer fiber constructs, and allowed to grow until most of the fibers were coated with multiple layers of osteoblasts. Standardized 9-mm nonhealing defects were created in 24 male athymic rats femurs and bridged with titanium miniplates. In 12 animals, the defects were filled with polymer constructs containing periosteum-derived cells (experimental group); in another 12 animals, the defects were either left unfilled (control group I) or filled with polymer templates alone (control group II). After 12-week in vivo implantation, the new bone produced bridged the surgically created defects completely in seven of 10 cases. The animals of the control groups did not show significant bone formation in the gap. Histologic evaluation revealed bone formation in all experimental specimens with rests of cartilage islands showing hypertrophying chondrocytes indicative of enchondral bone formation. Tissue-engineered growth of bone resulted in healing of large segmental bone defects in an orthotopic site in an animal model. The findings of this study support potential applications of the technique of tissue-engineered growth of bone to clinical situations where local bone formation is needed.

Animals↗

PubMedDate not supplied

Adult mesenchymal stem cells in dental research: a new approach for tissue engineering.

Many adult tissues contain a population of stem cells that have the ability to regenerate after trauma, disease or aging. Recently, there has been great interest in mesenchymal stem cells and their roles in maintaining the physiological structure of tissues. The studies on stem cells are thought to be very important and, in fact, it has been shown that this cell population can be expanded ex vivo to regenerate tissues not only of the mesenchymal lineage, such as intervertebral disc cartilage, bone and tooth-associated tissues, but also other types of tissues. Several studies have focused on the identification of odontogenic progenitors from oral tissues, and it has been shown that the mesenchymal stem cells obtained from periodontal ligament and dental pulp could have similar morphological and phenotypical features of the bone marrow mesenchymal cells. In fact a population of homogeneous human mesenchymal stem cells derived from periodontal ligament and dental pulp, and proliferating in culture with a well-spread morphology, can be recovered and characterized. Since these cells are considered as candidates for regenerative medicine, the knowledge of the cell differentiation mechanisms is imperative for the development of predictable techniques in implant dentistry, oral surgery and maxillo-facial reconstruction. Thus, future research efforts might be focused on the potential use of this cell population in tissue engineering. Further studies will be carried out to elucidate the molecular mechanisms involved in their maintenance and differentiation in vitro and in vivo.

Adult Stem Cells↗

PubMed2005

Bacterial cellulose as a potential scaffold for tissue engineering of cartilage.

Tissue constructs for cartilage with native mechanical properties have not been described to date. To address this need the bacterial cellulose (BC) secreted by Gluconacetobacter xylinus (= Acetobacter xylinum) was explored as a novel scaffold material due to its unusual material properties and degradability. Native and chemically modified BC materials were evaluated using bovine chondrocytes. The results indicate that unmodified BC supports chondrocyte proliferation at levels of approximately 50% of the collagen type II substrate while providing significant advantages in terms of mechanical properties. Compared to tissue culture plastic and calcium alginate, unmodified BC showed significantly higher levels of chondrocyte growth. Chemical sulfation and phosphorylation of the BC, performed to mimic the glucosaminoglycans of native cartilage, did not enhance chondrocyte growth while the porosity of the material did affect chondrocyte viability. The BC did not induce significant activation of proinflammatory cytokine production during in vitro macrophage screening. Hence, unmodified BC was further explored using human chondrocytes. TEM analysis and RNA expression of the collagen II from human chondrocytes indicated that unmodified BC supports proliferation of chondrocytes. In addition, ingrowth of chondrocytes into the scaffold was verified by TEM. The results suggest the potential for this biomaterial as a scaffold for tissue engineering of cartilage.

Animals↗

PubMed2003

Angiogenesis in tissue-engineered small intestine.

Tissue-engineered intestine offers promise as a potential novel therapy for short bowel syndrome. In this study we characterized the microvasculature and angiogenic growth factor profile of the engineered intestine. Twenty-three tissue-engineered small intestinal grafts were harvested from Lewis rat recipients 1 to 8 weeks after implantation. Architectural similarity to native bowel obtained from juvenile rats was assessed with hematoxylin and eosin-stained sections. Capillary density, measured after immunohistochemical staining for CD34, was expressed as number of capillaries per 1000 nuclei. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) tissue levels were measured by ELISA and normalized to total protein. Over the 8-week period cysts increased in volume (0.5 cm(3) at week 1 versus 12.6 cm(3) at week 8) and mass (1.30 +/- 0.29 versus 9.74 +/- 0.3 g; mean +/- SEM). Muscular and mucosal layers increased in thickness, but capillary density remained constant (82.95 +/- 4.81 capillaries per 1000 nuclei). The VEGF level was significantly higher in juvenile rat bowel than in engineered cyst (147.6 +/- 23.9 versus 42.3 +/- 3.4 pg/mg; p < 0.001). Tissue bFGF levels were also higher (315 +/- 65.48 versus 162.3 +/- 15.09 pg/mg; p < 0.05). The mechanism driving angiogenesis differs in engineered intestine and in normal bowel. VEGF and bFGF delivery may prove useful for bioengineering of intestine.

Aging↗

PubMed2005

Rapid and complete cellularization of hydroxyapatite for bone tissue engineering.

Using a tissue construct generated by cells in a scaffold in reconstructive surgery, as a substitute for autografts, is still challenging. Routine methods of incorporating cells into scaffolds are either passive, i.e. by gravity, or forced, as in a bioreactor. Extensive use of these methods is obstructed by tissue formation around the scaffold, hindrance in cell penetration and time required for cell coverage within the scaffold. In this study, human osteoblast cells as cell sheet structures were seeded to porous and dense hydroxyapatite with the hypothesis that preservation of native extracellular structures and cell-cell contacts would facilitate the cellularization process. Cellularization was assessed by fluorescence, confocal and scanning electron microscopy at intervals of 1 h, 2 days and 7 days. Cell patches with intact cell-cell and cell-extra cellular matrix contact attached and adhered on a scaffold within 1 h. The patches formed a monolayer within 2 days and complete cellularization of the scaffold was attained in 7 days. Cell viability, proliferation and function were assessed to understand the application of cell patch transfer to bone substitute. This novel approach for application in bone tissue engineering was successful in uniform distribution of intact osteoblast cell sheet structures on to bone substitute materials for rapid and complete cellularization without altering material characteristics.

Bone Substitutes↗

PubMedDate not supplied

[Human blood vessels created with tissue engineering].

Progress in tissue engineering now allows the recreation of functional blood vessels from cultured human vascular cells. When reconstructed under specific conditions, their structure, mechanical properties and function (especially vasomotricity) allow them to be used as human models for studying the biology and pharmacology of blood vessels. These models may help to circumvent the limitations in the obtention and use of native human blood vessels for experimental purpose.

Biomedical Research↗

PubMed2006

Synthetic biodegradable microparticles for articular cartilage tissue engineering.

Articular cartilage tissue engineering procedures require the transplantation of chondrocytes that have been expanded in vitro. The expansion is carried out for a considerable time and can lead to a modulation of cell phenotype. However, microcarrier cultures have been shown to allow cell expansion while maintaining the phenotype. Here, we have used the biodegradable polyester poly(lactide-co-glycolide) (PLGA) in the form of microspheres and irregular shaped microparticles with a diameter between 47 and 210 microm. Surface modification of particles was carried out by ammonia plasma treatment and subsequent adsorption of collagen. Alternatively, particles were modified by partial hydrolysis and subsequent immobilization of an amine-terminated dendrimer. Each surface modification step was characterized by X-ray photoelectron spectroscopy. The effectiveness of the surface modification procedures was demonstrated by in vitro cell culture experiments using sheep articular cartilage chondrocytes. A significant influence of both the particle shape and the surface chemistry on the proliferation rate was observed while the phenotype was maintained independent of the surface chemistry or particle shape. Chondrocytes cultured on PLGA microspheres were further assessed for cartilage tissue formation in collagen type I gels in nude mice. The tissue that were formed showed the appearance of a hyaline-like cartilage and the presence of the microspheres substantially reduced the degree of collagen gel contraction over 1-2 months.

Animals↗

PubMed2005

Tissue engineering of functional salivary gland tissue.

OBJECTIVES: Treatment of conditions that lead to salivary hypofunction, such as radiation induced xerostomia, is currently limited to the administration of saliva substitutes and sialogogues. The transient effect of these medications necessitates frequent administration, and systemic side effects may be intolerable. The creation of implantable, functional salivary gland tissue from autologous glandular cells would provide a physiologic solution to this problem. We investigated the feasibility of engineering such tissue in vivo. METHODS: Primary human salivary gland cells were grown, expanded, and seeded on biodegradable polymer scaffolds. A total of 48 scaffolds with cells and 16 control polymers without cells were implanted subcutaneously in athymic mice. The implants were retrieved 2, 4, and 8 weeks after the implantation for phenotypic and functional analyses. RESULTS: Human salivary gland epithelial cells retained their phenotypic and functional characteristics at all culture stages. Histologically, formation of acinar gland-like structures was observed within the engineered tissue by 4 weeks after implantation. Immunocytochemical and Western blot analyses of the implanted tissues demonstrated the expression of human a-amylase, cytokeratins AE1/AE3, and aquaporin-5 using cell-specific antibodies. Reverse-transcription polymerase chain reaction analyses confirmed the expression of human salivary type of alpha-amylase (sigma-amylase) mRNA. The retrieved tissues demonstrated the production of human alpha-amylase over time using a biochemical amylase detection system.

Animals↗

PubMed2006

A material decoy of biological media based on chitosan physical hydrogels: application to cartilage tissue engineering.

The cartilage tissue has a limited self-regenerative capacity. Tissue-engineering represents a promising trend for cartilage repair. The present study was aimed to develop a biomaterial formulation by combining fragments of chitosan hydrogel with isolated rabbit or human chondrocytes. We first reported the properties of the constructs elaborated with rabbit chondrocytes and pure chitosan physical hydrogels with defined molecular weight, acetylation degree and polymer concentration. Morphological data showed that chondrocytes were not penetrating the hydrogels but tightly bound to the surface of the fragments and spontaneously formed aggregates of combined cell/chitosan. A significant amount of neo-formed cartilage-like extracellular matrix (ECM) was first accumulated in-between cells and hydrogel fragments and furthermore was widely distributed within the neo-construct. The optimal biological response was obtained with hydrogel fragments concentrated at 1.5% (w/w) of polymer made from a chitosan with a degree of acetylation between 30 and 40%. Such hydrogels were then mixed with human chondrocytes. The phenotype of the cells was analyzed by using chondrocytic (mRNA expression of mature type II collagen and aggrecan as well as secretion of proteoglycans of high molecular weight) and non chondrocytic (mRNA expression of immature type II collagen and type I collagen) molecular markers. As compared with human chondrocytes cultured without chitosan hydrogel which rapidly dedifferentiated in primary culture, cells mixed with chitosan rapidly loose the expression of type I and immature type II collagen while they expressed mature type II collagen and aggrecan. In these conditions, chondrocytes maintained their phenotype for as long as 45 days, thus forming cartilage-like nodules. Taken together, these data suggest that a chitosan hydrogel does not work as a scaffold, but could be considered as a decoy of cartilage ECM components, thus favoring the binding of chondrocytes to chitosan. Such a biological response could be described by the concept of reverse encapsulation.

Acetylation↗