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Results for “Tissue Engineering”

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At least 451 records · Page 25Linked to original sources

PubMed2003

Inhibition of cartilage degradation: a combined tissue engineering and gene therapy approach.

OBJECTIVE: To determine if tissue-engineered cartilage can be protected from cytokine-induced degradation using a gene therapy approach. METHODS: Chemical and pantropic retroviral gene transfer methodologies were compared for their ability to introduce a luciferase reporter gene into adult bovine cartilage chondrocytes grown in monolayer. Pantropic retrovirus was then used to transduce these cells with human tissue inhibitor of metalloproteinases 1 (TIMP-1), and the stability of expression in monolayer or pellet culture was monitored for 6 weeks. Untransduced and TIMP-1-transduced cells were also used to tissue engineer 3-dimensional cartilage constructs that were then challenged with interleukin-1 (IL-1) for 4 weeks. Conditioned media and residual cartilage were collected for analysis of matrix components, including type II collagen and proteoglycans, and for TIMP-1 production and matrix metalloproteinase (MMP) activity. RESULTS: Chemical transfection of adult bovine chondrocytes gave rise to short-lived reporter expression that was virtually undetectable after 4 weeks of culture. In contrast, pantropic retroviral transduction gave rise to stable expression that persisted at a high level for at least 6 weeks. Pantropic transduction of the cells with TIMP-1 gave rise to similar long-term expression, both in monolayer and pellet cultures. TIMP-1-transduced tissue-engineered cartilage also retained TIMP-1 expression for an additional 4 weeks of culture in the presence of IL-1. Compared with control samples, TIMP-1-transgenic cartilage resisted the catabolic effects of IL-1, with MMP activity reduced to basal levels and a decreased loss of type II collagen. CONCLUSION: Pantropic retroviral transduction permits long-term expression of potentially therapeutic transgenes in adult tissue-engineered cartilage. While TIMP-1 transduction could be used to prevent collagen breakdown, alternative transgenes may be necessary to protect cartilage proteoglycans.

Animals↗

PubMed2002

Phenotypic and functional characterization of in vivo tissue engineered smooth muscle from normal and pathological bladders.

PURPOSE: The engineering of bladder tissue involves obtaining a biopsy from a host, expanding the cells, seeding them onto a matrix and implanting the cell-matrix composite back into the host. Clinically, cells used for these techniques may be harvested from abnormal bladders. It is not known whether abnormal bladder cells may be engineered into functionally normal tissue. We investigated the phenotypic and functional characteristics of tissue engineered bladder smooth muscle derived from patients with functionally normal bladders and functionally abnormal exstrophic and neuropathic bladders. MATERIALS AND METHODS: Human smooth muscle cells derived from functionally normal bladders, exstrophic bladders and neurogenic bladders were grown, expanded and seeded onto polymer scaffolds. Sixteen cell seeded scaffolds were analyzed in vitro and 40 cell seeded scaffolds were implanted in athymic mice. The tissue engineered constructs were retrieved and analyzed at 2 weeks and 2 months. The scaffolds were evaluated immunocytochemically, histologically, with organ bath studies and with Western blot analyses. RESULTS: Human bladder cells showed similar expression of smooth muscle marker proteins (alpha-actin and myosin) in vitro and after 2 months in vivo, regardless of their origin. All scaffolds showed similar muscle formation in vivo. The cell seeded scaffolds demonstrated the typical "contraction-relaxation" response to supramaximal electrical field and carbachol stimulation. There were no statistical differences among the experimental groups (normal, exstrophic, neurogenic). CONCLUSIONS: Tissue engineered muscle from normal and diseased bladders retain their phenotype in vitro and after implantation in vivo. The cells exhibited the same degree of contractility to electrical and chemical stimulation regardless of their origin. These results suggest that there are no phenotypic or functional differences between muscle cells obtained from urodynamically normal or pathological bladders, and that bladder muscle cells, regardless of their origin, may have the potential to be engineered into normal bladder tissues.

Actins↗

PubMed2005

Development and potential of a biomimetic chitosan/type II collagen scaffold for cartilage tissue engineering.

BACKGROUND: Damaged articular cartilage has very limited capacity for spontaneous healing. Tissue engineering provides a new hope for functional cartilage repair. Creation of an appropriate cell carrier is one of the critical steps for successful tissue engineering. With the supposition that a biomimetic construct might promise to generate better effects, we developed a novel composite scaffold and investigated its potential for cartilage tissue engineering. METHODS: Chitosan of 88% deacetylation was prepared via a modified base reaction procedure. A freeze-drying process was employed to fabricate a three-dimensional composite scaffold consisting of chitosan and type II collagen. The scaffold was treated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. Ultrastructure and tensile strength of the matrix were carried out to assess its physico-chemical properties. After subcutaneous implantation in rabbits, its in vivo biocompatibility and degradability of the scaffold were determined. Its capacity to sustain chondrocyte growth and biosynthesis was evaluated through cell-scaffold co-culture in vitro. RESULTS: The fabricated composite matrix was porous and sponge-like with interconnected pores measuring from 100-250 microm in diameter. After cross-linking, the scaffold displayed enhanced tensile strength. Subcutaneous implantation results indicated the composite matrix was biocompatible and biodegradable. In intro cell-scaffold culture showed the scaffold sustained chondrocyte proliferation and differentiation, and maintained the spheric chondrocytic phenotype. As indicated by immunohistochemical staining, the chondrocytes synthesized type II collagen. CONCLUSIONS: Chitosan and type II collagen can be well blended and developed into a porous 3-D biomimetic matrix. Results of physico-chemical and biological tests suggest the composite matrix satisfies the constraints specified for a tissue-engineered construct and may be used as a chondrocyte carrier for cartilage tissue engineering.

Animals↗

PubMed2004

Orthopaedic tissue engineering: from laboratory to the clinic.

Tissue engineering involves the use of cells (either adult, mesenchymal or embryonic stem cells) coupled with biological or artificial matrices or scaffolds which guide the cells during repair or regeneration of the tissue. Recently discovered and isolated growth factors can promote either adult or stem-cell growth and differentiation along selected pathways to re-form and repair skeletal tissues in adults. Bone repair enhancement and replacement is now possible with the use of tissue-engineering technologies. It is now possible to repair articular cartilage using the patient's own articular chondrocytes retrieved during arthroscopy, and expanded in vitro. Clinical results of this technique are very satisfactory.

Bone Regeneration↗

PubMed2006

Tissue engineering solutions for traumatic bone loss.

Tissue engineering strategies for the repair, replacement, or augmentation of bone defects involves the use of cells, matrices, and bioregulatory factors. The source (endogenous, exogenous) and character of these factors, however, may vary greatly among the many approaches taken by current investigators. Although the results of current tissue engineering methods for regenerating bone have shown great promise, the extent of damage to extremities associated with war injuries may require the development of techniques that differ substantially from current practice.

Bone Regeneration↗

PubMed2004

Computer-aided tissue engineering: application to biomimetic modelling and design of tissue scaffolds.

Computer-aided tissue engineering (CATE) enables many novel approaches in modelling, design and fabrication of complex tissue substitutes with enhanced functionality and improved cell-matrix interactions. Central to CATE is its bio-tissue informatics model that represents tissue biological, biomechanical and biochemical information that serves as a central repository to interface design, simulation and tissue fabrication. The present paper discusses the application of a CATE approach to the biomimetic design of bone tissue scaffold. A general CATE-based process for biomimetic modelling, anatomic reconstruction, computer-assisted-design of tissue scaffold, quantitative-computed-tomography characterization, finite element analysis and freeform extruding deposition for fabrication of scaffold is presented.

Biocompatible Materials↗

PubMed2003

Bioreactors for tissue engineering--a new role for perfusionists?

Tissue engineering is an exciting new area of medicine with rapid growth and expansion over the last decade. It has the potential to have a profound impact on the practice of medicine and influence the economic development in the industry of biotechnology. In almost every specialty of medicine, the ability to generate replacement cells and develop tissues will change the focus from artificial organs and transplantation to growing replacement organs from the patient's own stem cells. Once these organs are at a size that requires perfusion to maintain oxygen and nutrient delivery, then automated perfusion systems termed "bioreactors" will be necessary to sustain the organ until harvesting. The design of these "bioreactors" will have a crucial role in the maintenance of cellular function throughout the growth period. The perfusion schemes necessary to determine the optimal conditions have not been well elucidated and will undergo extensive research over the next decade. The key to progress in this endeavor will development of long-term perfusion techniques and identifying the ideal pressures, flow rates, type of flow (pulsatile/nonpulsatile), and perfusate solution. Perfusionists are considered experts in the field of whole body perfusion, and it is possible that they can participate in the development and operation of these "bioreactors." Additional education of perfusionists in the area of tissue engineering is necessary in order for them to become integral parts of this exciting new area of medicine.

Allied Health Personnel↗

PubMed2006

Dynamic contrast-enhanced MRI to quantify VEGF-enhanced tissue-engineered bladder graft neovascularization: pilot study.

Tissue engineered organs require an immediately perfused vascular tree. Currently, neovascularization assessment requires animal sacrifice and graft harvest. In this pilot study we assess whether neovascularization of an engineered urinary bladder construct is enhanced with vascular-derived endothelial growth factor (VEGF) and assessable non-invasively with dynamic contrast-enhanced MRI (DCE-MRI). Rabbit bladder acellular matrix was hybridized with hyaluronic acid (ACM-HA), fortified with one of three concentrations (0 ng, 10 ng, or 20 ng per gram of tissue) of vascular-derived endothelial growth factor (VEGF), and grafted onto bladders in nine rabbits (3 per VEGF concentration). At 1, 2 and 3 weeks, one rabbit from each VEGF group underwent DCE-MRI and graft harvest. Microvasculature was quantified with scrial optical transverse sectioning of CD31 stained whole mounts using PCl software. Masson trichrome and H&E staining were used to assess cellular proliferation and fibrosis. There was a significant difference in mean microvascular area (MVA) between the 10 and 20 ng VEGF groups (230187 vs 477894 microm2, P=0.014) but not between the 0 and 10 ng groups (210497 microm2, P=0.21). Gadolinium uptake increased with MVA and correlated with it on linear regression analysis (Pearson's correlation coefficient r=0.71). At three weeks, stromal cellularity was greatest, and fibrosis was least, in the high VEGF group. This preliminary work demonstrates improved neovascularization of bladder constructs with VEGF fortification of ACM-HA and the feasibility of MRI as a non-invasive method to assume angiogenesis in tissue engineered constructs.

Animals↗

PubMed2005

[Construction and clinical application of tissue engineered epidermal membrane].

OBJECTIVE: To Construct tissue engineered epidermal membrane for promoting healing of clinical skin graft donor site wound. METHODS: Epidermal cells /Chitosan-Gelatin (CG) membrane was constructed with cultured human epidermal cells(EC) and CG membrane, at the donor site of split skin graft, the wound was divided into three groups: the control group was covered with CG membrane without KC, KC/CG membrane was grafted on the treatment part of the wound area, and blank group was covered with traditional vaseline gauze. The engineered epidermal membrane and its effect on wound were evaluated with gross observation, HE, immunohistochemistry, collagen type I/III ratio by picrosirius polarization method and RT - PCR test at various time points before and after operation. RESULTS: The result showed that human tissue engineered epidermis could be constructed with cultured human EC and CG membrane, and this artificial epidermal membrane could be used for promoting the healing of skin graft donor site wound successfully (16 cases with 3 months' oberservation). The average healing time is (16.2 +/- 3.8) days for control group, (8.1 +/- 1.3) days for experimental group and (23.0 +/- 5.7) days for blank group. The artificial epidermis was well survived with normal structure. In addition, less hypertrophic scar development was observed in treated wound at 90 days (3 in 16 cases, 20.0%) than in the blank sites (11 in 16 cases, 74.4%). The difference is statistically significant (chi2 = 8.127, P < 0.01). CONCLUSIONS: The constructed EC-CG membrane can be constructed in vitro, survived in vivo and has good clinical application in promoting healing of skin graft donor site wound and inhibiting hypertrophic scar formation.

Adult↗

PubMed2002

Tissue engineering of small diameter vascular grafts.

Tissue engineering, using either polymer or biological based scaffolds, represents the newest approach to overcoming limitations of small diameter prosthetic vascular grafts. Their disadvantages include thromboembolism and thrombosis, anticoagulant related haemorrhage, compliance mismatch, neointimal hyperplasia, as well as aneurysm formation. This current review represents an overview about previous and contemporary studies in the field of artificial vascular conduits development regarding arterial and venous autografts, allografts, xenografts, alloplastic prostheses, and tissue engineering.

Animals↗

PubMed2000

Internal support of tissue-engineered cartilage.

BACKGROUND: Auricles previously created by tissue engineering in nude mice used a biodegradable internal scaffold to maintain the desired shape of an ear. However, the biodegradable scaffold incited a compromising inflammatory response in subsequent experiments in immunocompetent animals. OBJECTIVE: To test the hypothesis that tissue-engineered autologous cartilage can be bioincorporated with a nonreactive, permanent endoskeletal scaffold. MATERIALS AND METHODS: Auricular elastic cartilage was harvested from Yorkshire swine. The chondrocytes were isolated and suspended into a hydrogel (Pluronic F-127) at a cell concentration of 5 x 10(7) cells/mL. Nonbiodegradable endoskeletal scaffolds were formed with 1 of 5 polymers: (1) high-density polyethylene, (2) soft acrylic, (3) polymethylmethacrylate, (4) extrapurified Silastic, and (5) conventional Silastic. Three groups were studied: (1) a control group using only the 5 polymers, (2) the 5 polymers enveloped by Pluronic F-127 only, and (3) the implants coated with Pluronic F-127 seeded with chondrocytes. All constructs were implanted subdermally; implants containing cells were implanted into the same animal from which the cells had been islolated. The implants were harvested after 8 weeks of in vivo culture and histologically analyzed. RESULTS: Only implants coated by hydrogel plus cells generated healthy new cartilage. With 3 polymers (high-density polyethylene, acrylic, and extrapurified Silastic), the coverage was nearly complete by elastic cartilage, with minimal fibrocartilage and minimal to no inflammatory reaction. The Food and Drug Administration-approved conventional Silastic implants resulted in fragments of fibrous tissue mixed with elastic cartilage plus evidence of chronic inflammation. The polymethylmethacrylate implant was intermediate in the amount of cartilage formed and degree of inflammation. CONCLUSIONS: This pilot technique combining tissue-engineered autologous elastic cartilage with a permanent biocompatible endoskeleton demonstrated success in limiting the inflammatory response to the scaffold, especially to high-density polyethylene, acrylic, and extrapurified Silastic. This model facilitates the potential to generate tissue of intricate shape, such as the human ear, by internal support. Arch Otolaryngol Head Neck Surg. 2000;126:1448-1452

Animals↗

PubMed2002

Tissue engineering of heart valves -- current aspects.

Tissue engineering of heart valves is an evolving research field. Driven by the shortcomings of the heart valve substitutes currently available, such as need for anticoagulation, susceptibility to infections, inability to grow and autorepair, the multidisciplinary approach for designing and growing viable heart valves identical to the native heart valves has begun. The following will give an update of the recent developments, current limitations and potential future applications of tissue-engineered heart valves.

Animals↗

PubMed2001

Toward tissue engineering of the knee meniscus.

This review details current efforts to tissue engineer the knee meniscus successfully. The meniscus is a fibrocartilaginous tissue found within the knee joint that is responsible for shock absorption, load transmission, and stability within the knee joint. If this tissue is damaged, either through tears or degenerative processes, then deterioration of the articular cartilage can occur. Unfortunately, there is a dearth in the amount of work done to tissue engineer the meniscus when compared to other musculoskeletal tissues, such as bone. This review gives a brief overview of meniscal anatomy, biochemical properties, biomechanical properties, and wound repair techniques. The discussion centers primarily on the different components of attempting to tissue engineer the meniscus, such as scaffold materials, growth factors, animal models, and culturing conditions. Our approach for tissue engineering the meniscus is also discussed.

Animals↗

PubMed2001

The growth of tissue engineering.

This report draws upon data from a variety of sources to estimate the size, scope, and growth rate of the contemporary tissue engineering enterprise. At the beginning of 2001, tissue engineering research and development was being pursued by 3,300 scientists and support staff in more than 70 startup companies or business units with a combined annual expenditure of over $600 million. Spending by tissue engineering firms has been growing at a compound annual rate of 16%, and the aggregate investment since 1990 now exceeds $3.5 billion. At the beginning of 2001, the net capital value of the 16 publicly traded tissue engineering startups had reached $2.6 billion. Firms focusing on structural applications (skin, cartilage, bone, cardiac prosthesis, and the like) comprise the fastest growing segment. In contrast, efforts in biohybrid organs and other metabolic applications have contracted over the past few years. The number of companies involved in stem cells and regenerative medicine is rapidly increasing, and this area represents the most likely nidus of future growth for tissue engineering. A notable recent trend has been the emergence of a strong commercial activity in tissue engineering outside the United States, with at least 16 European or Australian companies (22% of total) now active.

Artificial Organs↗

PubMed2003

Adhesive protein interactions with chitosan: consequences for valve endothelial cell growth on tissue-engineering materials.

Stable endothelialization of a tissue-engineered heart valve is essential for proper valve function, although adhesive characteristics of the native valve endothelial cell (VEC) have rarely been explored. This research evaluated VEC adhesive qualities and attempted to enhance VEC growth on the biopolymer chitosan, a novel tissue-engineering scaffold material with promising biological and chemical properties. Aortic VEC cultures were isolated and found to preferentially adhere to fibronectin, collagen types IV and I over laminin and osteopontin in a dose-dependent manner. Seeding of VEC onto comparison substrates revealed VEC growth and morphology to be preferential in the order: tissue culture polystyrene > gelatin, poly(DL-lactide-co-glycolide), chitosan > poly(hydroxy alkanoate). Adhesive protein precoating of chitosan did not significantly enhance VEC growth, despite equivalent protein adsorption as to polystyrene. Initial cell adhesion to protein-precoated chitosan, however, was higher than for polystyrene. Composite chitosan/collagen type IV films were investigated as an alternative to simple protein precoatings, and were shown to improve VEC growth and morphology over chitosan alone. These findings suggest potential manipulation of chitosan properties to improve amenability to valve tissue-engineering applications.

Animals↗

PubMed2003

[Prospect of tissue engineering study in andrology].

The concept of cell transplantation by tissue engineering has provided numerous possibilities for tissue reconstruction in andrology. Application studies of tissue engineering have been made in such aspects as Leydig cells, testicular prosthesis, penile corporal and penile prosthesis in order to improve, restore or replace the existing tissue function. Although most reconstructive efforts still remain at the experimental stage, several techniques have been applied to clinical practice with satisfactory results. This article briefly reviewed the applications of tissue engineering to andrology.

Andrology↗

PubMed2005

Tissue engineering osteochondral implants for temporomandibular joint repair.

Tissue engineering has provided an alternative to traditional strategies to repair and regenerate temporomandibular joints (TMJ). A successful strategy to engineer osteochondral tissue, such as that found in the TMJ, will produce tissue that is both biologically and mechanically functional. Image-based design (IBD) and solid free-form (SFF) fabrication can be used to generate scaffolds that are load bearing and match patient and defect site geometry. The objective of this study was to demonstrate how scaffold design, materials, and biological factors can be used in an integrated approach to regenerate a multi-tissue interface. IBD and SFF were first used to create biomimetic scaffolds with appropriate bulk geometry and microarchitecture. Biphasic composite scaffolds were then manufactured with the same techniques and used to simultaneously generate bone and cartilage in discrete regions and provide for the development of a stable interface between cartilage and subchondral bone. Poly-l-lactic acid/hydroxyapatite composite scaffolds were differentially seeded with fibroblasts transduced with an adenovirus expressing bone morphogenetic protein-7 in the ceramic phase and fully differentiated chondrocytes in the polymeric phase, and were subcutaneously implanted into mice. Following implantation in the ectopic site, the biphasic scaffolds promoted the simultaneous growth of bone, cartilage, and a mineralized interface tissue. Within the ceramic phase, the pockets of tissue generated included blood vessels, marrow stroma, and adipose tissue. This combination of IBD and SFF-fabricated biphasic scaffolds with gene and cell therapy is a promising approach to regenerate osteochondral defects and, ultimately, the TMJ.

Animals↗

PubMedDate not supplied

Computational study of culture conditions and nutrient supply in cartilage tissue engineering.

Different culture conditions for cartilage tissue engineering were evaluated with respect to the supply of oxygen and glucose and the accumulation of lactate. A computational approach was adopted in which the culture configurations were modeled as a batch process and transport was considered within constructs seeded at high cell concentrations and of clinically relevant dimensions. To assess the extent to which mass transfer can be influenced theoretically, extreme cases were distinguished in which the culture medium surrounding the construct was assumed either completely static or well mixed and fully oxygenated. It can be concluded that severe oxygen depletion and lactate accumulation can occur within constructs for cartilage tissue engineering. However, the results also indicate that transport restrictions are not insurmountable, providing that the medium is well homogenized and oxygenated and the construct's surfaces are sufficiently exposed to the medium. The large variation in uptake rates of chondrocytes indicates that for any specific application the quantification of cellular utilization rates, depending on the cell source and culture conditions, is an essential starting point for optimizing culture protocols.

Cartilage↗