Showing papers on "Tissue engineering published in 2004"
TL;DR: Various architectural parameters of scaffolds important for bone tissue engineering (e.g. porosity, pore size, interconnectivity, and pore-wall microstructures) are discussed and surface modification of scaffolding is also discussed based on the significant effect of surface chemistry on cells adhesion and function.
Abstract: Bone tissue engineering is a rapidly developing area. Engineering bone typically uses an artificial extracellular matrix (scaffold), osteoblasts or cells that can become osteoblasts, and regulating factors that promote cell attachment, differentiation, and mineralized bone formation. Among them, highly porous scaffolds play a critical role in cell seeding, proliferation, and new 3D-tissue formation. A variety of biodegradable polymer materials and scaffolding fabrication techniques for bone tissue engineering have been investigated over the past decade. This article reviews the polymer materials, scaffold design, and fabrication methods for bone tissue engineering. Advantages and limitations of these materials and methods are analyzed. Various architectural parameters of scaffolds important for bone tissue engineering (e.g. porosity, pore size, interconnectivity, and pore-wall microstructures) are discussed. Surface modification of scaffolds is also discussed based on the significant effect of surface chemistry on cells adhesion and function.
1,221 citations
TL;DR: By enabling reproducible and controlled changes of specific environmental factors, bioreactor systems provide both the technological means to reveal fundamental mechanisms of cell function in a 3D environment, and the potential to improve the quality of engineered tissues.
1,164 citations
TL;DR: In this article, the most frequently used materials and fabrication technologies for scaffolds are reviewed and some exciting new developments in scaffold materials are also discussed, and important scaffold design principles are described.
997 citations
TL;DR: An approach for rapid, nanoliter-scale synthesis of biomaterials and characterization of their interactions with cells is described and a host of unexpected materials effects that offer new levels of control over human embryonic stem cell behavior are identified.
Abstract: Identification of biomaterials that support appropriate cellular attachment, proliferation and gene expression patterns is critical for tissue engineering and cell therapy. Here we describe an approach for rapid, nanoliter-scale synthesis of biomaterials and characterization of their interactions with cells. We simultaneously characterize over 1,700 human embryonic stem cell-material interactions and identify a host of unexpected materials effects that offer new levels of control over human embryonic stem cell behavior.
802 citations
TL;DR: This paper presents a comprehensive review of the fabrication methods, including conventional, mainly manual, techniques and advanced processing methods such as rapid prototyping (RP) techniques.
783 citations
TL;DR: This method for immobilizing biomolecules in 3D matrices can generally be applied to any optically clear hydrogel, offering a solution to construct scaffolds with programmed spatial features for tissue engineering applications.
Abstract: Tissue engineering aims to replace, repair or regenerate tissue/organ function, by delivering signalling molecules and cells on a three-dimensional (3D) biomaterials scaffold that supports cell infiltration and tissue organization. To control cell behaviour and ultimately induce structural and functional tissue formation on surfaces, planar substrates have been patterned with adhesion signals that mimic the spatial cues to guide cell attachment and function. The objective of this study is to create biochemical channels in 3D hydrogel matrices for guided axonal growth. An agarose hydrogel modified with a cysteine compound containing a sulphydryl protecting group provides a photolabile substrate that can be patterned with biochemical cues. In this transparent hydrogel we immobilized the adhesive fibronectin peptide fragment, glycine-arginine-glycine-aspartic acid-serine (GRGDS), in selected volumes of the matrix using a focused laser. We verified in vitro the guidance effects of GRGDS oligopeptide-modified channels on the 3D cell migration and neurite outgrowth. This method for immobilizing biomolecules in 3D matrices can generally be applied to any optically clear hydrogel, offering a solution to construct scaffolds with programmed spatial features for tissue engineering applications.
761 citations
TL;DR: The biologic response to these xenogeneic bioscaffolds, including the immune response, is discussed herein.
716 citations
TL;DR: It is shown that a network of long-lasting blood vessels can be formed in mice by co-implantation of vascular endothelial cells and mesenchymal precursor cells, by-passing the need for risky genetic manipulations.
Abstract: The construction of stable blood vessels is a fundamental challenge for tissue engineering in regenerative medicine. Although certain genes can be introduced into vascular cells to enhance their survival and proliferation, these manipulations may be oncogenic. We show here that a network of long-lasting blood vessels can be formed in mice by co-implantation of vascular endothelial cells and mesenchymal precursor cells, by-passing the need for risky genetic manipulations. These networks are stable and functional for one year in vivo.
669 citations
TL;DR: The potential utility of the HA-DTPH-PEGDA hydrogel as an in situ crosslinkable, injectable material for tissue engineering is confirmed and the majority of cells survived crosslinking and the cell density increased tenfold during the 4-week culture period in vitro.
661 citations
TL;DR: This review considers recent advances in knowledge about cell–ECM interactions and the general principles of biomaterial design for tissue engineering are considered, with same examples.
Abstract: The extracellular matrix (ECM) consists of a complex mixture of structural and functional macromolecules and serves an important role in tissue and organ morphogenesis and in the maintenance of cell and tissue structure and function The great diversity observed in the morphology and composition of the ECM contributes enormously to the properties and function of each organ and tissue The ECM is also important during growth, development, and wound repair: its own dynamic composition acts as a reservoir for soluble signaling molecules and mediates signals from other sources to migrating, proliferating, and differentiating cells Approaches to tissue engineering center on the need to provide signals to cell populations to promote cell proliferation and differentiation These "external signals" are generated from growth factors, cell-ECM, and cell-cell interactions, as well as from physical-chemical and mechanical stimuli This review considers recent advances in knowledge about cell-ECM interactions A description of the main ECM molecules and cellular receptors with particular care to integrins and their role in stimulation of specific types of signal transduction pathways is also explained The general principles of biomaterial design for tissue engineering are considered, with same examples
622 citations
TL;DR: Three different approaches toward the formation of nano-fibrous materials have emerged: self-assembly, electrospinning and phase separation; each has a unique set of characteristics, which lends to its development as a scaffolding system.
TL;DR: Results suggested that the nano-structured porous PLLA scaffold is a potential cell carrier in NTE, which mimics natural extracellular matrix.
TL;DR: The research presented herein provides preliminary data toward the development of electrospun collagen and elastin tissue engineering scaffolds for theDevelopment of a three layer vascular construct.
Abstract: Significant challenges must be overcome before the true benefit and economic impact of vascular tissue engineering can be fully realized. Toward that end, we have pioneered the electrospinning of micro- and nano-fibrous scaffoldings from the natural polymers collagen and elastin and applied these to development of biomimicking vascular tissue engineered constructs. The vascular wall composition and structure is highly intricate and imparts unique biomechanical properties that challenge the development of a living tissue engineered vascular replacement that can withstand the high pressure and pulsatile environment of the bloodstream. The potential of the novel scaffold presented here for the development of a viable vascular prosthetic meets these stringent requirements in that it can replicate the complex architecture of the blood vessel wall. This replication potential creates an "ideal" environment for subsequent in vitro development of a vascular replacement. The research presented herein provides preliminary data toward the development of electrospun collagen and elastin tissue engineering scaffolds for the development of a three layer vascular construct.
TL;DR: The present review not only outlines several approaches relevant to the isolation and therapeutic use of MSCs, but also presents several examples of phenotypic and functional characterization of isolated M SCs and their progeny.
Abstract: Mesenchymal stem cells (MSCs) are progenitors of all connective tissue cells. In adults of multiple vertebrate species, MSCs have been isolated from bone marrow (BM) and other tissues, expanded in culture, and differentiated into several tissue-forming cells such as bone, cartilage, fat, muscle, tendon, liver, kidney, heart, and even brain cells. Recent advances in the practical end of application of MSCs toward regeneration of a human-shaped articular condyle of the synovial joint is one example of their functionality and versatility. The present review not only outlines several approaches relevant to the isolation and therapeutic use of MSCs, but also presents several examples of phenotypic and functional characterization of isolated MSCs and their progeny.
TL;DR: An overview of 3-D tissue fabrication techniques based on methods for: scaffold fabrication, cellular assembly, and hybrid hydrogel/cell methods are presented and their potential utility for tissue engineering is reviewed.
TL;DR: The synthesis and characterization of a novel biodegradable elastomer, poly(1,8-octanediol-co-citric acid) (POC), that has potential for use in tissue engineering, in particular the engineering of small-diameter blood vessels is described.
Abstract: Tissue engineering often requires the use of a three dimensional scaffold for cells to grow on and differentiate properly. Generally, the ideal scaffold should be biocompatible, biodegradable, allow for proper cell loading, be cell-responsive and regulate the cell multiplication and differentiation, and possess mechanical and physical properties that are suitable for the target application. As many tissues in the body have elastomeric properties, successful tissue engineering of these requires the development of compliant biodegradable scaffolds. Despite the recognized importance of mechanical stimuli on tissue development, there has been a dearth of research into the design and evaluation of elastomeric biodegradable scaffolds. The few materials that have been reported in the literature require complex and costly synthesis procedures, which translate into higher manufacturing costs and hinder the commercial and clinical implementation of tissue engineering. Herein we describe the synthesis and characterization of a novel biodegradable elastomer, poly(1,8-octanediol-co-citric acid) (POC), that has potential for use in tissue engineering, in particular the engineering of small-diameter blood vessels. Development of materials for this application is important as cardiovascular disease affecting blood vessels is the principal cause of death in the U.S.A. POC has the following advantages: non-toxic monomers, relatively simple synthesis that can be carried out under mild conditions without addition of toxic catalysts or crosslinking reagents (making it a good candidate for drug delivery and cost-effective scale-up), controllable mechanical and biodegradation properties, easy processing, and inherent surface affinity for various cell types.
TL;DR: In this article, a nanofibrous matrix was fabricated from a biodegradable poly(p-dioxanone-co-L-lactide)-block-poly(ethylene glycol) copolymer, and the morphology of cell-matrix interaction with the electrospun matrix was examined.
TL;DR: Animal models have been used to test the capacity of potentially bioactive molecules to promote pulp repair following their implantation into the pulp and found some molecules found in dentin extracellular matrix may have potential in dental therapy as bioactive agents for pulp repair or tissue engineering.
Abstract: Odontoblasts produce most of the extracellular matrix (ECM) components found in dentin and implicated in dentin mineralization. Major differences in the pulp ECM explain why pulp is normally a non-mineralized tissue. In vitro or in vivo, some dentin ECM molecules act as crystal nucleators and contribute to crystal growth, whereas others are mineralization inhibitors. After treatment of caries lesions of moderate progression, odontoblasts and cells from the sub-odontoblastic Hohl's layer are implicated in the formation of reactionary dentin. Healing of deeper lesions in contact with the pulp results in the formation of reparative dentin by pulp cells. The response to direct pulp-capping with materials such as calcium hydroxide is the formation of a dentinal bridge, resulting from the recruitment and proliferation of undifferentiated cells, which may be either stem cells or dedifferentiated and transdifferentiated mature cells. Once differentiated, the cells synthesize a matrix that undergoes mineralization. Animal models have been used to test the capacity of potentially bioactive molecules to promote pulp repair following their implantation into the pulp. ECM molecules induce either the formation of dentinal bridges or large areas of mineralization in the coronal pulp. They may also stimulate the total closure of the pulp in the root canal. In conclusion, some molecules found in dentin extracellular matrix may have potential in dental therapy as bioactive agents for pulp repair or tissue engineering.
TL;DR: This scaffold composite has promise for the clinical repair of large bony defects according to the principles of bone tissue engineering and cell culture and animal model tests showed that the composite material is bioactive.
Abstract: A bone scaffold material (nano-HA/ collagen/PLA composite) was developed by biomimetic synthesis. It shows some features of natural bone both in main composition and hierarchical microstructure. Nano-hydroxyapatite and collagen assembled into mineralized fibril. The three-dimensional porous scaffold materials mimic the microstructure of cancellous bone. Cell culture and animal model tests showed that the composite material is bioactive. The osteoblasts were separated from the neonatal rat calvaria. Osteoblasts adhered, spread, and proliferated throughout the pores of the scaffold material within a week. A 15-mm segmental defect model in the radius of the rabbit was used to evaluate the bone-remodeling ability of the composite. Combined with 0.5 mg rhBMP-2, the material block was implanted into the defect. The segmental defect was integrated 12 weeks after surgery, and the implanted composite was partially substituted by new bone tissue. This scaffold composite has promise for the clinical repair of large bony defects according to the principles of bone tissue engineering.
TL;DR: Test data demonstrate that appropriate combinations of soluble and biomaterial-mediated regulatory signals in cell-based tissue engineering systems can result in both more efficient and more effective tissue regeneration.
TL;DR: This study has demonstrated that cartilage tissue can be created from bone marrow mesenchymal stem cells and shown particular patterns of in vitro chondrogenesis induction on human bone marrow MSCs (hBMSCs) by cycling the growth factors.
TL;DR: Results indicate a favorable interaction between this synthetic nanofibrous scaffold with the two types of cells and suggest its potential application in tissue engineering a blood vessel substitute.
Abstract: Substantial effort is being invested by the bioengineering community to develop biodegradable polymer scaffolds suitable for tissue-engineering applications. An ideal scaffold should mimic the structural and purposeful profile of materials found in the natural extracellular matrix (ECM) architecture. To accomplish this goal, poly (L-lactide-co-epsilon-caprolactone) [P(LLA-CL)] (75:25) copolymer with a novel architecture produced by an electrospinning process has been developed for tissue-engineering applications. The diameter of this electrospun P(LLA-CL) fiber ranges from 400 to 800 nm, which mimicks the nanoscale dimension of native ECM. The mechanical properties of this structure are comparable to those of human coronary artery. To evaluate the feasibility of using this nanofibrous scaffold as a synthetic extracellular matrix for culturing human smooth muscle cells and endothelial cells, these two types of cells were seeded on the scaffold for 7 days. The data from scanning electron microscopy, immunohistochemical examination, laser scanning confocal microscopy, and a cell proliferation assay suggested that this electrospun nanofibrous scaffold is capable of supporting cell attachment and proliferation. Smooth muscle cells and endothelial cells seeded on this scaffold tend to maintain their phenotypic shape. They were also found to integrate with the nanofibers to form a three-dimensional cellular network. These results indicate a favorable interaction between this synthetic nanofibrous scaffold with the two types of cells and suggest its potential application in tissue engineering a blood vessel substitute.
TL;DR: The results indicate the potential for utilizing a direct-write, three-dimensional bioassembly tool to create viable, patterned tissue-engineered constructs.
Abstract: The primary emphasis of tissue engineering is the design and fabrication of constructs for the replacement of nonfunctional tissue. Because tissue represents a highly organized interplay of cells and extracellular matrix, the fabrication of replacement tissue should mimic this spatial organization. This report details studies evaluating the use of a three-dimensional, direct-write cell deposition system to construct spatially organized viable structures. A direct-write bioassembly system was designed and fabricated to permit layer-by-layer placement of cells and extracellular matrix on a variety of material substrates. Human fibroblasts suspended in polyoxyethylene/polyoxypropylene were coextruded through a positive displacement pen delivery onto a polystyrene slide. After deposition, approximately 60% of the fibroblasts remained viable. Bovine aortic endothelial cells (BAECs) suspended in soluble collagen type I were coextruded via microdispense pen delivery onto the hydrophilic side of flat sheets of polyethylene terephthalate. After deposition with a 25-gauge tip, approximately 86% of the BAECs were viable. When maintained in culture for up to 35 days, the constructs remained viable and maintained their original spatial organization. These results indicate the potential for utilizing a direct-write, three-dimensional bioassembly tool to create viable, patterned tissue-engineered constructs.
TL;DR: The results suggest that RGD-silk scaffolds are particularly suitable for autologous bone tissue engineering, presumably because of their stable macroporous structure, tailorable mechanical properties matching those of native bone, and slow degradation.
Abstract: Porous biodegradable silk scaffolds and human bone marrow derived mesenchymal stem cells (hMSCs) were used to engineer bone-like tissue in vitro. Two different scaffolds with the same microstructure were studied: collagen (to assess the effects of fast degradation) and silk with covalently bound RGD sequences (to assess the effects of enhanced cell attachment and slow degradation). The hMSCs were isolated, expanded in culture, characterized with respect to the expression of surface markers and ability for chondrogenic and osteogenic differentiation, seeded on scaffolds, and cultured for up to 4 weeks. Histological analysis and microcomputer tomography showed the development of up to 1.2-mm-long interconnected and organized bonelike trabeculae with cuboid cells on the silk-RGD scaffolds, features still present but to a lesser extent on silk scaffolds and absent on the collagen scaffolds. The X-ray diffraction pattern of the deposited bone corresponded to hydroxyapatite present in the native bone. Biochemical analysis showed increased mineralization on silk-RGD scaffolds compared with either silk or collagen scaffolds after 4 weeks. Expression of bone sialoprotein, osteopontin, and bone morphogenetic protein 2 was significantly higher for hMSCs cultured in osteogenic than control medium both after 2 and 4 weeks in culture. The results suggest that RGD-silk scaffolds are particularly suitable for autologous bone tissue engineering, presumably because of their stable macroporous structure, tailorable mechanical properties matching those of native bone, and slow degradation.
TL;DR: One representative tissue engineering system involving the integrated use of adult human stem cells, custom-designed scaffolds, and advanced bioreactors with dynamic loading is described and focuses on the tissue engineering of ligaments.
Abstract: Tissue engineering is emerging as a significant clinical option to address tissue and organ failure by implanting biological substitutes for the compromised tissues. As compared to the transplantation of cells alone, engineered tissues offer the potential advantage of immediate functionality. Engineered tissues can also serve as physiologically relevant models for controlled studies of cells and tissues designed to distinguish the effects of specific signals from the complex milieu of factors present in vivo. A high number of ligament failures and the lack of adequate options to fully restore joint functions have prompted the need to develop new tissue engineering strategies. We discuss the requirements for ligament reconstruction, the available treatment options and their limitations, and then focus on the tissue engineering of ligaments. One representative tissue engineering system involving the integrated use of adult human stem cells, custom-designed scaffolds, and advanced bioreactors with dynamic loading is described.
TL;DR: This review emphasizes how different cell types and scaffold designs can be used to modulate tissue properties and engineer more complex tissue structures, with emphasis on cartilage and bone tissues.
Abstract: The field of tissue engineering promises to deliver biological substitutes to repair or replace tissues in the body that have been injured or diseased. The clinical demand for musculoskeletal tissues is particularly high, especially for cartilage and bone defects. Although they are generally considered biologically simple structures, musculoskeletal tissues consist of highly organized three-dimensional networks of cells and matrix, giving rise to tissue structures with remarkable mechanical properties. Although the field of cartilage and bone tissue engineering has progressed significantly in recent years, the development of structurally ordered tissues has not been accomplished. More strategies are needed to ensure that the appropriate cell and matrix organization is being achieved in the engineered tissues. This review emphasizes how different cell types and scaffold designs can be used to modulate tissue properties and engineer more complex tissue structures, with emphasis on cartilage and bone tissues.
TL;DR: It is concluded that until today, microfluidic devices have not been used extensively in tissue engineering, and major contributions are expected in two areas: growth of complex tissue, and the development of in vitro physiological systems for studying fundamental biological phenomena.
Abstract: An introductory overview of the use of microfluidic devices for tissue engineering is presented. After a brief description of the background of tissue engineering, different application areas of microfluidic devices are examined. Among these are methods for patterning cells, topographical control over cells and tissues, and bioreactors. Examples where microfluidic devices have been employed are presented such as basal lamina, vascular tissue, liver, bone, cartilage and neurons. It is concluded that until today, microfluidic devices have not been used extensively in tissue engineering. Major contributions are expected in two areas. The first is growth of complex tissue, where microfluidic structures ensure a steady blood supply, thereby circumventing the well-known problem of providing larger tissue structures with a continuous flow of oxygen and nutrition, and withdrawal of waste products. The second, and probably more important function of microfluidics, combined with micro/nanotechnology, lies in the development of in vitro physiological systems for studying fundamental biological phenomena.
TL;DR: Recombinant human collagens are an efficient scaffold for bone repair when combined with a recombinant bone morphogenetic protein in a porous, sponge-like format, and when presented as a membrane, sponge or gel can serve as a basis for the engineering of skin, cartilage and periodontal ligament, depending on the specific requirements of the chosen application.
Abstract: Collagen is the main structural protein in vertebrates. It plays an essential role in providing a scaffold for cellular support and thereby affecting cell attachment, migration, proliferation, differentiation, and survival. As such, it also plays an important role in numerous approaches to the engineering of human tissues for medical applications related to tissue, bone, and skin repair and reconstruction. Currently, the collagen used in tissue engineering applications is derived from animal tissues, creating concerns related to the quality, purity, and predictability of its performance. It also carries the risk of transmission of infectious agents and precipitating immunological reactions. The recent development of recombinant sources of human collagen provides a reliable, predictable and chemically defined source of purified human collagens that is free of animal components. The triple-helical collagens made by recombinant technology have the same amino acid sequence as human tissue-derived collagen. Furthermore, by achieving the equivalent extent of proline hydroxylation via coexpression of genes encoding prolyl hydroxylase with the collagen genes, one can produce collagens with a similar degree of stability as naturally occurring material. The recombinant production process of collagen involves the generation of single triple-helical molecules that are then used to construct more complex three-dimensional structures. If one loosely defines tissue engineering as the use of a biocompatible scaffold combined with a biologically active agent (be it a gene or gene construct, growth factor or other biologically active agent) to induce tissue regeneration, then the production of recombinant human collagen enables the engineering of human tissue based on a human matrix or scaffold. Recombinant human collagens are an efficient scaffold for bone repair when combined with a recombinant bone morphogenetic protein in a porous, sponge-like format, and when presented as a membrane, sponge or gel can serve as a basis for the engineering of skin, cartilage and periodontal ligament, depending on the specific requirements of the chosen application.
TL;DR: Attachment, spreading, and proliferation of cells is dramatically enhanced on RGD-modified surfaces but only modestly accelerated in vivo tissue formation.
Abstract: Hyaluronan (HA) hydrogels resist attachment and spreading of fibroblasts and most other mammalian cell types. A thiol-modified HA (3,3'-dithiobis(propanoic dihydrazide) [HA-DTPH]) was modified with peptides containing the Arg-Gly-Asp (RGD) sequence and then crosslinked with polyethylene glycol (PEG) diacrylate (PEGDA) to create a biomaterial that supported cell attachment, spreading, and proliferation. The hydrogels were evaluated in vitro and in vivo in three assay systems. First, the behavior of human and murine fibroblasts on the surface of the hydrogels was evaluated. The concentration and structure of the RGD peptides and the length of the PEG spacer influenced cell attachment and spreading. Second, murine fibroblasts were seeded into HA-DTPH solutions and encapsulated via in situ crosslinking with or without bound RGD peptides. Cells remained viable and proliferated within the hydrogel for 15 days in vitro. Although the RGD peptides significantly enhanced cell proliferation on the hydrogel surface, the cell proliferation inside the hydrogel in vitro was increased only modestly. Third, HA-DTPH/PEGDA/peptide hydrogels were evaluated as injectable tissue engineering materials in vivo. A suspension of murine fibroblasts in HA-DTPH was crosslinked using PEGDA plus PEGDA peptide, and the viscous, gelling mixture was injected subcutaneously into the flanks of nude mice; gels formed in vivo following injection. After 4 weeks, growth of new fibrous tissue had been accelerated by the sense RGD peptides. Thus, attachment, spreading, and proliferation of cells is dramatically enhanced on RGD-modified surfaces but only modestly accelerated in vivo tissue formation.
TL;DR: The results demonstrate that the properties of engineered vascular tissues can be modulated by the combination of selected extracellular matrix components, and the application of mechanical stimulation.