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At least 397 records · Page 22Linked to original sources
PubMed1999

Joint cartilage regeneration by tissue engineering.

The research field of tissue engineering combines cells biology, biomaterial science, and surgery. Major long-term goals are tissue and organ replacement therapies using the patients' own cells. Our work is focused on the treatment of severe joint defects and on plastic surgery using in vitro engineered cartilage tissues. The practical approaches in cartilage engineering face problems with three-dimensional cell distribution or cell immobilization raising biocompatibility problems. The tissue engineering of cartilage is based on combining biocompatible cell embedding substances such as fibrin, agarose, alginate, hyaluronic acid and fiber fleece scaffolds of poly alpha-hydroxy acids (PLLA/PGLA). Different technical approaches were established: a) three-dimensional in vitro cultures of chondrocytes for the development of vital tissue transplants and b) interacting three-dimensional cultures consisting of different cell populations, such as BMP-transfected mesenchymal cells. The preshaped artificial tissue constructs were cultured in perfusion chambers to maintain a stable diffusion of nutrients during the in vitro pre-formation step. Subsequently, pre-formed tissues were implanted into nude mice and into 4 mm articular joint defects of rabbits. Transplants were found to produce cartilage typic morphological patterns and matrix. 80% of the transplants remained stable in vivo. However, 20% of the tissues are resorbed or replaced by a fibrous tissue. These results demonstrate that current artificial cartilage transplants are already feasible for plastic reconstruction. The treatment of severe joint defects, however, faces additional problems which are addressed in ongoing studies: (a) the fixation of engineered cartilage in joints, (b) the protection against chronic inflammatory degradation, and (c) the required enormous mechanical stability.

Animals↗
PubMed2002

The suitability of cells from different tissues for use in tissue-engineered skin substitutes.

Tissue-engineered skin substitutes may be a future remedy for burn wounds and chronic wounds, as wound contraction and scar formation cannot be prevented with the current standard treatment. The aim of this study therefore was to identify readily available sources of fibroblasts suitable for dermal substitution. Three different tissues were studied: dermal tissue from split-skin graft, subcutaneous fat tissue and eschar tissue obtained through debridement of burn wounds. We determined the cellular profile and the cell numbers immediately after isolation and after 2 and 14 days of fibroblast culture using flow cytometry and cell counting with a cytometer. In addition, parts of the isolated cell suspensions were seeded directly into a porous collagen dermal substitute to investigate contraction over time. Various cell types were isolated from the three different tissues, but after 14 days of culturing predominantly fibroblasts (>90%) were detected. Keratinocytes, granulocytes and macrophages, if present, disappeared within 14 days. In the cell populations derived from dermal tissue, the percentage of myofibroblasts had decreased significantly by day 14 (from 8% to 3%, P=0.028). In contrast, this percentage had increased in the cell populations derived from fat and eschar (from 23% to 40% and from 20% to 38%, respectively). The fibroblast yield from dermal tissue after 2 weeks of culturing (50 x 10(6) cells/g of tissue) was significantly higher than the yield from fat and eschar tissue (2 x 10(6) cells/g of each tissue, P=0.029). Immunohistochemistry of collagen matrices seeded and cultured with fat- and eschar-derived cells revealed a high prevalence of myofibroblasts, whereas hardly any myofibroblasts were detected in the matrices seeded with dermal cells. The contraction of the eschar matrices was highest (74+/-6% remaining area), whereas dermal matrices contracted significantly less (92+/-7% remaining area, P=0.029) with intermediate contraction for fat matrices. We conclude that fibroblast cultures can be established from dermal tissue, fat tissue and eschar tissue. Dermis is the best fibroblast source for use in skin substitutes as it yields the highest numbers of fibroblasts with minimal numbers of myofibroblasts.

Adipose Tissue↗
PubMed2006

Trends in tissue engineering research.

For more than a decade, Tissue Engineering has been devoted to the reporting and discussion of scientific advances in the interdisciplinary field of tissue engineering. In this study, 779 original articles published in the journal since its inception were analyzed and classified according to different attributes, such as focus of research and tissue of interest, to reveal trends in tissue engineering research. In addition, the use of different biomaterials, scaffold architectures, surface and bulk modification agents, cells, differentiation factors, gene delivery vectors, and animal models was examined. The results of this survey show interesting trends over time and by continental origin.

Forecasting↗
PubMed2006

The effect of anisotropic architecture on cell and tissue infiltration into tissue engineering scaffolds.

A common phenomenon in tissue engineering is rapid tissue formation on the outer edge of the scaffold which restricts cell penetration and nutrient exchange to the scaffold centre, resulting in a necrotic core. To address this problem, we generated scaffolds with both random and anisotropic open porous architectures to enhance cell and subsequent tissue infiltration throughout the scaffold for applications in bone and cartilage engineering. Hydroxyapatite (HA) and poly(D,L-lactic acid) (P(DL)LA) scaffolds with random open porosity were manufactured, using modified slip-casting and by supercritical fluid processing respectively, and subsequently characterised. An array of porous aligned channels (400 microm) was incorporated into both scaffold types and cell (human osteoblast sarcoma, for HA scaffolds; ovine meniscal fibrochondrocytes, for P(DL)LA scaffolds) and tissue infiltration into these modified scaffolds was assessed in vitro (cell penetration) and in vivo (tissue infiltration; HA scaffolds only). Scaffolds were shown to have an extensive random, open porous structure with an average porosity of 85%. Enhanced cell and tissue penetration was observed both in vitro and in vivo demonstrating that scaffold design alone can influence cell and tissue infiltration into the centre of tissue engineering scaffolds.

Animals↗
PubMed2006

A registry for tissue engineering clinical trials.

Because tissue engineering products and processes are now being transferred from laboratory research into clinical applications, questions are being raised about what is the scope of an optimal clinical trial in this sector. A registry for these clinical trials is currently being established.

Clinical Trials as Topic↗
PubMed2007

Gene-modified tissue-engineered skin: the next generation of skin substitutes.

Tissue engineering combines the principles of cell biology, engineering and materials science to develop three-dimensional tissues to replace or restore tissue function. Tissue engineered skin is one of most advanced tissue constructs, yet it lacks several important functions including those provided by hair follicles, sebaceous glands, sweat glands and dendritic cells. Although the complexity of skin may be difficult to recapitulate entirely, new or improved functions can be provided by genetic modification of the cells that make up the tissues. Gene therapy can also be used in wound healing to promote tissue regeneration or prevent healing abnormalities such as formation of scars and keloids. Finally, gene-enhanced skin substitutes have great potential as cell-based devices to deliver therapeutics locally or systemically. Although significant progress has been made in the development of gene transfer technologies, several challenges have to be met before clinical application of genetically modified skin tissue. Engineering challenges include methods for improved efficiency and targeted gene delivery; efficient gene transfer to the stem cells that constantly regenerate the dynamic epidermal tissue; and development of novel biomaterials for controlled gene delivery. In addition, advances in regulatable vectors to achieve spatially and temporally controlled gene expression by physiological or exogenous signals may facilitate pharmacological administration of therapeutics through genetically engineered skin. Gene modified skin substitutes are also employed as biological models to understand tissue development or disease progression in a realistic three-dimensional context. In summary, gene therapy has the potential to generate the next generation of skin substitutes with enhanced capacity for treatment of burns, chronic wounds and even systemic diseases.

Animals↗
PubMed2002

Tissue engineering--current challenges and expanding opportunities.

Tissue engineering can be used to restore, maintain, or enhance tissues and organs. The potential impact of this field, however, is far broader-in the future, engineered tissues could reduce the need for organ replacement, and could greatly accelerate the development of new drugs that may cure patients, eliminating the need for organ transplants altogether.

Animals↗
PubMed2005

Development and characterization of a spheroidal coculture model of endothelial cells and fibroblasts for improving angiogenesis in tissue engineering.

Neovascularization is a critical step in tissue engineering applications since implantation of voluminous grafts without sufficient vascularity results in hypoxic cell death of central tissues. We have developed a three-dimensional spheroidal coculture system consisting of human umbilical vein endothelial cells (HUVECs) and human primary fibroblasts (hFBs) to improve angiogenesis in tissue engineering applications. Morphological analysis of cryosections from HUVEC/hFB cospheroids revealed a characteristic temporal and spatial organization with HUVECs located in the center of the cospheroid and a peripheral localization of fibroblasts. In coculture spheroids, the level of apoptosis of endothelial cells was strongly decreased upon cocultivation with fibroblasts. Collagen-embedded HUVEC spheroids develop numerous lumenized capillary-like sprouts. This was also apparent for HUVEC/hFB cospheroids, albeit to a lesser extent. Quantification of cumulative sprout length revealed an approximately 35% reduction in endothelial cell sprouting upon cocultivation with fibroblasts in cospheroids. The slight reduction in endothelial cell sprouting was not mediated by a paracrine mechanism but is most likely due to the formation of heterogenic cell contacts between HUVECs and hFBs within the cospheroid. The model system introduced in this study is suitable for the development of a preformed lumenized capillary-like network ex vivo and may therefore be useful for improving angiogenesis in in vivo tissue engineering applications.

Apoptosis↗
PubMed2004

[Construction of a tissue engineering skin containing capillary-like network].

OBJECTIVE: To construct a tissue engineering skin containing capillary-like network by employing tissue engineering method. METHODS: The numan umbilical vein endothelial cells(HUVECs) were isolated from a new-born umbilical cord. The keratinocytes and dermal fibroblasts were isolated from a new-born foreskin biopsy. After the collagen gel was prepared, the fibroblasts and the vascular endothelial cells were added in a ratio of 1 to 1 to construct a skin substitute containing capillary-like network. The skin substitute was observed by HE staining and immuno histochemical staining (VIII factor). The reconstructed skin containing capillary-like network was used to repair the nude mice skin defects in the experimental group. The tissue engineering skin containing no vascular endothelial cells was used in control group. RESULTS: Capillary-like network could be observed in the dermal layer of the tissue engineering skin, and the nude mice skin defects were repaired by the skin substitutes in the experimental group. In control group, no capillary-like network was found. CONCLUSION: The tissue engineering skin containing capillary-like network is successfully constructed in vitro and can be used to repair the full-thickness skin defects.

Animals↗
PubMed2005

Bioscaffolds in tissue engineering: a rationale for use in the reconstruction of musculoskeletal soft tissues.

Bioscaffolds derived from animal tissues can be an appealing substrate to induce the formation of functional tissue (histogenesis) within the context of tissue engineering. Bioscaffolds obtained from the extracellular matrix not only contain collagen, which can provide mechanical support, but also include the required biologically active molecules that provide a stimulus for active tissue remodeling. Manufacturing, processing, and the tissue source of the biological scaffold affect the biologic outcome and are important in predicting the clinical results. This article discusses the merits and limitations of using bioscaffolds in soft tissue engineering.

Animals↗
PubMed2000

[Cell transplantation in surgery--reality and prospects for tissue engineering].

Traditionally surgical repair of tissue defects and loss or failure of function has relied on mechanical means, medical (drug) treatment, autologous and allogenic transplantation, and alloplastic/synthetic devices. Tissue engineering represents a new interdisciplinary field of applied research combining engineering and biosciences together with clinical application (mainly in surgical specialities) to develop living substitutes for tissues and organs. The understanding of cell-cell interactions and chemical signalling (growth factors) and the selection of appropriate matrices (cell-matrix interaction) is the key for success. Gene therapy represents the logical combination with tissue engineering on the molecular biology level. Application of cultivated skin and cartilage has already become reality, engineering of vascularized, more complex organs remains a challenge for this century.

Cells, Cultured↗
PubMed2006

[Cell culture, tissue engineering and regenerative medicine. Part I].

Tissue engineering is an interdisciplinary field that applies the principles and methods of engineering and the cell culture toward the development of biomaterials that restore, maintain or improve tissue function. The amalgamation of engineering and medicine has interested many scientists for at last two hundred years. What was the goal of cell culture? First, for progress in life sciences achievement and subsequent for virology and toxicology development. In vitro studies are done because of many problems with carrying out animal experiments. In this work the authors present the attempts of physicians, anatomopathologists, embryologists and biologists which contributed to fast development of new area in medicine--tissue engineering.

Animals↗
PubMed2006

Craniofacial tissue engineering by stem cells.

Craniofacial tissue engineering promises the regeneration or de novo formation of dental, oral, and craniofacial structures lost to congenital anomalies, trauma, and diseases. Virtually all craniofacial structures are derivatives of mesenchymal cells. Mesenchymal stem cells are the offspring of mesenchymal cells following asymmetrical division, and reside in various craniofacial structures in the adult. Cells with characteristics of adult stem cells have been isolated from the dental pulp, the deciduous tooth, and the periodontium. Several craniofacial structures--such as the mandibular condyle, calvarial bone, cranial suture, and subcutaneous adipose tissue--have been engineered from mesenchymal stem cells, growth factor, and/or gene therapy approaches. As a departure from the reliance of current clinical practice on durable materials such as amalgam, composites, and metallic alloys, biological therapies utilize mesenchymal stem cells, delivered or internally recruited, to generate craniofacial structures in temporary scaffolding biomaterials. Craniofacial tissue engineering is likely to be realized in the foreseeable future, and represents an opportunity that dentistry cannot afford to miss.

Absorbable Implants↗
PubMed2006

Survival and function of transplanted islet cells on an in vivo, vascularized tissue engineering platform in the rat: A pilot study.

As in vivo tissue engineering of complex tissues and organs progresses, there is a need for an independently vascularized, alterable, and recoverable model. Current models of islet cell transplantation (release into the portal venous system, placement under the renal capsule, and microencapsulation) lack these qualities. We have developed a model of angiogenesis and spontaneous tissue generation in the rat that lends itself as a potential platform for tissue engineering. In this experiment, we examined the effectiveness of such a model in addressing some of the shortcomings of endocrine pancreatic transplantation. An arteriovenous loop was created in the groins of five adult inbred Sprague-Dawley rats, and placed within polycarbonate chambers. Isolated pancreatic islet cell clusters were placed within the chambers, suspended in a matrix of Matrigel. The chambers were recovered at 3 weeks, and the newly generated tissue was processed for histologic and immunohistochemical analysis. By 3 weeks, spontaneous generation of angiogenesis and collagen matrix and deposition of a collagen matrix was observed. Surviving islet cells were identified by histology and their viability was confirmed via immunohistochemistry for insulin and glucagon. This study demonstrates the ability to maintain viability and functionality of transplanted islet cells on a tissue-engineered platform with an independent vascular supply. The model provides the ability to alter the graft environment via matrix substitution, cellular coculture, and administration of growth factors. The transplanted tissues are recoverable without animal sacrifice and are microsurgically transferable. This model may provide an in vivo culture platform for the study of islet transplantation.

Animals↗
PubMed2003

Mechanical strain-stimulated remodeling of tissue-engineered blood vessel constructs.

Progress in tissue-engineering research has renewed optimism about the possibility of constructing a physiologically functional blood vessel substitute in the laboratory. To this end, we have explored the use of defined mechanical stimulation to further the development of vascular tissue analogs. We now report our findings on smooth muscle cell and fibroblast-seeded collagen constructs exposed to 10% cyclic strain for 4 or 8 days. Our results demonstrate that 4-day strained constructs exhibit an enhancement of mechanical properties, likely through the remodeling actions of matrix metalloproteinase 2 (MMP-2). Strain-stimulated expression of MMP-2 is accompanied by alterations in elastin and collagen gene expression. In the context of tissue engineering a blood vessel construct, we report that strain-stimulated regulation of MMP-2 activity could have a favorable impact on the structural development of the constructs whereas overexpression of MMP-2 during prolonged exposure to strain (8 days) could have adverse consequences on the structural integrity of the tissue analogs. Taken together, these results illustrate the importance of mechanical stimulus as a major regulatory component of tissue-engineered blood vessel remodeling.

Animals↗
PubMed2001

[Fabrication of allogeneic cartilage with tissue engineering technique and repair of laryngeal cartilage defects in rabbits].

OBJECTIVE: To investigate the fabrication of allogeneic tissue engineered cartilage in predetermined shapes and its ability to repair laryngeal cartilage defects. METHODS: Tissue engineering technique was used to make allogeneic tissue engineered cartilage in predetermined shapes, and then some of them were utilized to repair cartilage defects in the rabbit larynges(n = 12). Finally, the chondrogenesis and reparative effect were studied grossly and histologically at various periods. RESULTS: 1. The gross specimens of 4 weeks after implantation revealed the presence of new hyaline cartilage of approximately the same shapes as original predetermined shapes, which had fair elasticity and support ability. Histological evaluation showed the characteristics of cartilage tissue. 2. Laryngeal cartilage defects were well repaired using allogeneic tissue engineered cartilage in different periods after operation. A few chondrocytes were observed between the reparative areas with tissue engineered cartilage and normal cartilage. Abundant matrices were also detected in the reparative and interfacial areas. No inflammatory cells were found. CONCLUSION: It is possible to regenerate new cartilage in predetermined shapes using tissue engineering technique in allograft animals with immunity. Allogeneic tissue engineered cartilage can be used as reparative material to repair cartilage defect of rabbit larynx.

Animals↗
PubMed2003

[Tissue engineering: a tool to understand the physiological mechanisms].

Tissue engineering is a new domain, which allows some very unique studies of many human physiological mechanisms. This technology, based on cell capacity to reproduce a three-dimensional tissue with or without the help of biomaterials, is an interesting approach to study cells in an environment quite similar to the in vivo context. This article summarizes the LOEX's (laboratory of experimental organogenesis) scientific endeavor in tissue engineering in order to better understand some physiological or pathological mechanisms. Thus wound healing, stem cells, graft vascularization and cell interactions are domains where tissue engineering has already made a significant impact.

Cell Communication↗