SEARCH · PubMed Health

Results for “Tissue Engineering”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources

PubMed2003

Successful application of tissue engineered vascular autografts: clinical experience.

Foreign materials often used in cardiovascular surgery may cause unwanted side effects and reduced growth potential. To resolve these problems, we have designed a tissue-engineering technique that utilizes bone marrow cells (BMCs) in clinical treatments. To obtain tissue-engineered material, we harvested saphenous vein samples from patients, which were then minced, cultured and seeded onto a biodegradable scaffold. The first operation was performed in May 1999 as previously described (N. Engl. J. Med. 344 (7) (2001) 532) and this method was repeated on two other patients. From November 2001, we used aspirated BMCs as the cell source, which were seeded onto the scaffold on the day of surgery. This method was applied in 22 patients. There was no morbidity such as thrombogenic complications, stenosis or obstruction of tissue-engineered autografts, and no mortality due to these techniques. These results indicate that BMCs seeded onto a biodegradable scaffold to establish tissue-engineered vascular autografts (TEVAs) is an ideal strategy, and present strong evidence for the justification and validity of our protocol in clinical trials of tissue engineering.

Adolescent↗

PubMedDate not supplied

Neural tissue engineering: a self-organizing collagen guidance conduit.

We report a novel implantable device that will deliver a tethered aligned collagen guidance conduit containing Schwann cells into a peripheral nerve injury site. Cells (Schwann cells and fibroblasts) incorporated into tethered rectangular collagen gels contracted and resulted in uniaxial alignment. This tissue-engineered construct was tested in three-dimensional culture and demonstrated the ability to guide neurite extension from dissociated dorsal root ganglia. A silicone tube was adapted to provide tethering sites for an implantable construct such that uniaxial cell-generated tension resulted in the formation of a bridge of aligned collagen fibrils, with a resident Schwann cell population. The potential of this device for surgical nerve regeneration was assessed in a 5-mm defect in a rat sciatic nerve model. Neural regeneration through this device was significantly greater than in controls, demonstrating that this system has potential both as a simple robust clinical implant and as a three-dimensional engineered tissue model.

Animals↗

PubMed2006

A self-assembling process in articular cartilage tissue engineering.

Current therapies for articular cartilage defects often result in fibrocartilaginous tissue. To achieve regeneration with hyaline articular cartilage, tissue-engineering approaches employing cell-seeded scaffolds have been investigated. However, limitations of scaffolds include phenotypic alteration of cells, stress-shielding, hindrance of neotissue organization, and degradation product toxicity. This study employs a self-assembling process to produce tissue-engineered constructs over agarose in vitro without using a scaffold. Compared to past studies using various meshes and gels as scaffolding materials, the self-assembly method yielded constructs with comparable GAG and collagen content. By 12 weeks, the self-assembling process resulted in tissue-engineered constructs that were hyaline- like in appearance with histological, biochemical, and biomechanical properties approaching those of native articular cartilage. Overall, constructs contained two thirds more GAG per dry weight than calf articular cartilage. Collagen per dry weight reached more than one third the level of native tissue. IHC and gel electrophoresis showed collagen type II production and absence of collagen type I. More importantly, self-assembled constructs reached well over one third the stiffness of native tissue.

Animals↗

PubMed2006

Characterisation of a collagen membrane for its potential use in cardiovascular tissue engineering applications.

In this study, Biomend, a collagen membrane conventionally used in the regeneration of periodontal tissue, is investigated for its possible use in the field of cardiovascular tissue engineering. A key requirement of most potential tissue engineering scaffolds is that degradation occurs in tandem with tissue regeneration and extra cellular matrix remodelling. To this end, it is crucial to understand the degradation mechanics and mechanisms of the material and to investigate the practicability of using Biomend as a possible scaffold material. With this in mind, methodologies for the initial characterisation of the scaffold material were determined. The mechanical properties of Biomend samples, subjected to various degrees of hydration and enzymatic degradation, were examined primarily through tensile testing experiments. The effects of enzymatic degradation were monitored quantitatively, by observing weight loss, and visually, by studying micrographs. Cell adhesion and viability were of primary concern. Confocal laser scanning microscopy was employed to illustrate endothelialisation on the surface of this collagen membrane. Fluorescence microscopy was used to visualise cell viability on the membrane surface. These images, coupled with assays to measure cell activity, suggest that Biomend is not a suitable substrate to allow endothelialisation. In summary, this collagen membrane has suitable mechanical properties with the potential to control its degradation rate. However, since poor endothelial cell viability was observed on the membrane, it may not be suitable for use in cardiovascular tissue engineering applications.

Biocompatible Materials↗

PubMed2006

Human mesenchymal stem cells induce T cell anergy and downregulate T cell allo-responses via the TH2 pathway: relevance to tissue engineering human heart valves.

To generate an ''off the shelf'' tissue-engineered heart valve, the cells would need to be of allogeneic origin. Here, we report the possibility of using human bone marrow-derived mesenchymal stem cells (MSCs) as a suitable allogeneic cell source for tissue-engineered heart valves. Proliferative responses of primary and primed CD4+ T cells to allogeneic MSCs were examined. A protein microarray system was used to detect soluble factors from supernatants collected from the T cell assays. MSCs are poor stimulators of primary and primed CD4+ T cell proliferation, despite provision of B7-1 trans-co-stimulation. MSCs not only directly inhibited primary and primed T cell responses to allogeneic peripheral blood mononuclear cells (PBMCs), but 24-h pre-culture of T cells with MSCs suppressed subsequent T cell proliferative responses to allogeneic PBMCs in a contact-dependent manner. Analysis of supernatants revealed a distinctly different cytokine profile after co-culture of T cells with MSCs than with PBMCs or endothelial cells. Pro-inflammatory Th1 cytokines interleukin (IL)-1alpha and beta, interferon (IFN)gamma, and tumor necrosis factor (TNF)alpha were downregulated, whereas, anti-inflammatory Th2 cytokines IL-3, IL-5, IL-10, and IL-13 and the Th2 chemokine I-309, a chemoattractant for regulatory T cells, were upregulated. Further analysis revealed that after co-culture with MSCs, the T cells exhibited a regulatory phenotype (CD4+ CD25(lo) CD69(lo) FoxP3+). MSCs downregulate T cell responses through direct contact and secretion of anti-inflammatory and tolerogenic cytokines, which may involve the recruitment of regulatory T cells. This implies that allogeneic MSCs could be a suitable cell source for tissue engineering a heart valve.

Cells, Cultured↗

PubMed2004

Evaluation of mineralized collagen and alpha-tricalcium phosphate as scaffolds for tissue engineering of bone using human mesenchymal stem cells.

Owing to their plasticity and high proliferation capacity in vitro, mesenchymal stem cells (MSC) isolated from human bone marrow are promising candidates for use in tissue engineering approaches for the repair or replacement of mesenchymal tissues such as bone, cartilage or tendon. In keeping with the tissue engineering concept, these cells are cultivated on three-dimensional (3D) scaffolds to replace 3D tissue defects. Among the scaffolds tested for tissue engineering of bone, those containing phosphorus and calcium, as natural bone does, are the most promising candidates for this purpose. In this study, MSC from five patients were isolated from bone marrow. After in vitro expansion, cells were cultivated and differentiated towards the osteogenic lineage on mineralized collagen sponges and alpha-tricalcium phosphate (alpha-TCP). To analyze how appropriate these scaffolds would be for tissue engineering purposes, we established an in vitro characterization system to describe seeding efficiency, cell distribution and proliferation behavior on each scaffold. Real-time reverse transcriptase polymerase chain reaction quantification of important genes involved in osteogenic differentiation [e.g. bone sialoprotein (BSP), bone morphogenic protein 2, alkaline phosphatase and osteocalcin] was used to monitor the differentiation process of cells seeded on mineralized collagen and alpha-TCP. Using this in vitro characterization, we were able to demonstrate effective 3D growth of MSC on both scaffolds investigated. Improved osteogenic differentiation was observed on the scaffolds as compared to control monolayers. Of the two matrices, mineralized collagen was superior to alpha-TCP with regard to seeding efficacy (98 vs. 67%, p = 0.0003), increase in osteogenic marker genes (BSP expression on day 24, Pcollagen vs. TCP = 0.046) and 3D cell alignment (cell infiltration up to 500 vs. 200 microm). In conclusion, our data suggest that mineralized collagen is a promising candidate for use as a scaffold in tissue engineering of bone.

Adult↗

PubMed2002

[Comparative study on graft of autogeneic iliac bone and tissue engineered bone].

OBJECTIVE: To compare the clinical results of repairing bone defect of limbs with tissue engineering technique and with autogeneic iliac bone graft. METHODS: From July 1999 to September 2001, 52 cases of bone fracture were randomly divided into two groups (group A and B). Open reduction and internal fixation were performed in all cases as routine operation technique. Autogeneic iliac bone was implanted in group A, while tissue engineered bone was implanted in group B. Routine postoperative treatment in orthopedic surgery was taken. The operation time, bleeding volume, wound healing and drainage volume were compared. The bone union was observed by the X-ray 1, 2, 3, and 5 months after operation. RESULTS: The sex, age and disease type had no obvious difference between groups A and B. all the wounds healed with first intention. The swelling degree of wound and drainage volume had no obvious difference. The operation time in group A was longer than that in group B (25 minutes on average) and bleeding volume in group A was larger than that in group B (150 ml on average). Bone union completed within 3 to 7 months in both groups. But there were 2 cases of delayed union in group A and 1 case in group B. CONCLUSION: Repair of bone defect with tissue engineered bone has as good clinical results as that with autogeneic iliac bone graft. In aspect of operation time and bleeding volume, tissue engineered bone graft is superior to autogeneic iliac bone.

Adolescent↗

PubMed2002

Photopolymerizable hydrogels for tissue engineering applications.

Photopolymerized hydrogels are being investigated for a number of tissue engineering applications because of the ability to form these materials in situ in a minimally invasive manner such as by injection. In addition, hydrogels, three-dimensional networks of hydrophilic polymers that are able to swell large amounts of water, can be made to resemble the physical characteristics of soft tissues. Hydrogel materials also generally exhibit high permeability and good biocompatibility making, these materials attractive for use in cell encapsulation and tissue engineering applications. A number of hydrogel materials can be formed via photopolymerization processes mild enough to be carried out in the presence of living cells. This allows one to homogeneously seed cells throughout the scaffold material and to form hydrogels in situ. This review presents advantages of photopolymerization of hydrogels and describes the photoinitiators and materials in current use. Applications of photopolymerized hydrogels in tissue engineering that have been investigated are summarized.

Animals↗

PubMed2004

Tissue engineering for the replacement of organ function in the genitourinary system.

Acquired and congenital abnormalities may lead to genitourinary organ damage or loss, requiring eventual reconstruction. Tissue engineering follows the principles of cell transplantation, materials science, and engineering toward the development of biological substitutes that would restore and maintain normal function. Tissue engineering may involve matrices alone, wherein the body's natural ability to regenerate is used to orient or direct new tissue growth, or the use of matrices with cells. Both synthetic and natural biodegradable materials have been used, either alone or as cell delivery vehicles. Tissue engineering has been applied experimentally for the reconstitution of several urologic tissues and organs, including bladder, ureter, urethra, kidney, testis, and genitalia. Fetal applications have also been explored. Recently, several tissue engineering technologies have been used clinically including the use of cells as bulking agents for the treatment of vesicoureteral reflux and incontinence and urethral replacement. Recent progress suggests that engineered genitourinary tissues may have clinical applicability in the future.

Humans↗

PubMed2003

[The study of hBMP-4 gene modified tissue-engineered bone].

OBJECTIVE: Bone marrow stromal cells (bMSCs) of rabbits transferred with mammalian hBMP-4 expression plasmid were used to construct tissue-engineered bone. Gene therapy combined with tissue-engineering technique was explored to further improve osteogenesis. METHODS: pEGFP-hBMP-4 plasmid was constructed by subcloning technique. bMSCs were then transferred with either pEGFP-hBMP-4, pEGFP plasmid by lipofectamine or left uninfected in vitro. The cells from the 3 groups were combined with natural non-organic bone (NNB) to construct tissue-engineered bones, which were subcutaneously implanted into nude mice (6 implants per group) for 4 weeks. Specimens were evaluated through histological and computerized new bone formation analysis. RESULTS: pEGFP-hBMP-4 plasmid was successfully constructed. bMSCs could attach and proliferate on the surface on NNB. In vivo experiment showed that new bone formation in pEGFP-hBMP-4 group was higher than those of the control groups. CONCLUSIONS: Tissue-engineered bone using hBMP-4 gene modified bMSCs might be an ideal alternative for the repair of bone.

Animals↗

PubMed2002

Vascularisation of tissue-engineered grafts: the regulation of angiogenesis in reconstructive surgery and in disease states.

Angiogenesis (the formation of new blood vessels) is essential for the growth of new tissue, tissue repair and wound healing. Tissue engineering, the construction of new tissue and organs for reparative purposes, relies on angiogenesis for the vascularisation of these new grafts. In tissue engineering, the emphasis to date has been on vascularisation of newly constructed tissue grafts by an extrinsic blood supply, and relatively little attention has been given to the possibility of building these grafts around an intrinsic blood supply. However, there are many disease processes, notably tumour growth, where excess angiogenesis can be a major problem. The purposes of this review are, first, to examine various methods of vascularising tissue-engineered grafts, and, second, to compare the role of angiogenesis in tissue engineering, where stimulation of angiogenesis is paramount, with pathological states, such as tumour growth, where angiogenesis needs to be inhibited.

Artificial Organs↗

PubMed2004

Tissue engineering of the meniscus.

Meniscus lesions are among the most frequent injuries in orthopaedic practice and they will inevitably lead to degeneration of the knee articular cartilage. The fibro-cartilage-like tissue of the meniscus is notorious for its limited regenerative capacity. Tissue engineering could offer new treatment modalities for repair of meniscus tears and eventually will enable the replacement of a whole meniscus by a tissue-engineered construct. Many questions remain to be answered before the final goal, a tissue-engineered meniscus is available for clinical implementation. These questions are related to the selection of an optimal cell type, the source of the cells, the need to use growth factor(s) and the type of scaffold that can be used for stimulation of differentiation of cells into tissues with optimal phenotypes. Particularly in a loaded, highly complex environment of the knee, optimal mechanical properties of such a scaffold seem to be of utmost importance. With respect to cells, autologous meniscus cells seems the optimal cell source for tissue engineering of meniscus tissue, but their availability is limited. Therefore research should be stimulated to investigate the suitability of other cell sources for the creation of meniscus tissue. Bone marrow stroma cells could be useful since it is well known that they can differentiate into bone and cartilage cells. With respect to growth factors, TGF-beta could be a suitable growth factor to stimulate cells into a fibroblastic phenotype but the problems of TGF-beta introduced into a joint environment should then be solved. Polyurethane scaffolds with optimal mechanical properties and with optimal interconnective macro-porosity have been shown to facilitate ingrowth and differentiation of tissue into fibro-cartilage. However, even these materials cannot prevent cartilage degeneration in animal models. Surface modification and/or seeding of cells into the scaffolds before implantation may offer a solution for this problem in the future.This review focuses on a number of specific questions; what is the status of the development of procedures for lesion healing and how far are we from replacing the entire meniscus by a (tissue-engineered) prosthesis. Subquestions related to the type of scaffold used are: is the degree of tissue ingrowth and differentiation related to the initial mechanical properties and if so, what is the influence of those properties on the subsequent remodelling of the tissue into fibro-cartilage; what is the ideal pore geometry and what is the optimal degradation period to allow biological remodelling of the tissue in the scaffold. Finally, we will finish with our latest results of the effect of tear reconstruction and the insertion of prostheses on articular cartilage degradation.

Animals↗

PubMed2000

Tissue-engineered skin (Apligraf) in the healing of patients with epidermolysis bullosa wounds.

BACKGROUND: At present, wound treatment of inherited epidermolysis bullosa (EB) is only supportive. OBJECTIVE: To determine the safety and clinical effects of tissue-engineered skin (Apligraf; Organogenesis Inc, Canton, Mass) in the healing of wounds of patients with different types of EB. DESIGN: An open-label uncontrolled study of 15 patients with EB treated with tissue-engineered skin. Each patient received tissue-engineered skin on up to 2 wounds on each of 3 clinic visits: day 1, week 6, and week 12. They were evaluated 7 (+/- 3) days and 6 weeks after each round of treatment. A quality-of-life survey was administered during week 6. SETTING: University of Miami, Miami, Fla. PATIENTS: Volunteers with EB. MAIN OUTCOME MEASURE: Safety and wound healing. RESULTS: A total of 69 different acute wounds received tissue-engineered skin at the day-1 (24 wounds), week-6 (23 wounds), and week-12 (22 wounds) visits. Overall, 63 wounds (79%) were found healed at the day-7 visit. Of the acute wounds, 82% (51/62) were healed 6 weeks after being treated, 75% (27/36) after 12 weeks, and 79% (11/14) after 18 weeks. Nine chronic wounds were also treated. Four were healed at 6 weeks; however, 7 were still open at the last clinic visit (week 18). There were no signs of rejection or clinical infection and no adverse events related to the tissue-engineered skin. The quality of life for most patients improved after treatment. Compared with patients' recollection of wounds treated with standard dressings, healing was faster and less painful. CONCLUSION: In this series of patients, tissue-engineered skin induced very rapid healing, was not clinically rejected, and was devoid of adverse effects. It was felt by the patients and families to be more effective than conventional dressings for EB wounds.

Biomedical Engineering↗

PubMed2006

Modulation of cell differentiation in bone tissue engineering constructs cultured in a bioreactor.

In summary, many factors can influence the osteoblastic differentiation of marrow stromal cells when cultivated on three-dimensional tissue engineering scaffolds. In creating ideal bone tissue engineering constructs consisting of a combination of a scaffold, cells, and bioactive factors; a flow perfusion bioreactor is a much more suitable culture environment than static culture in well plates. The bioreactor eliminates mass transport limitations to the scaffold interior and provides mechanical stimulation to the seeded cells through fluid shear. Scaffold properties such as pore size impact cell differentiation, especially in flow perfusion culture. In addition, the bone-like extracellular matrix created by the in vitro culture of marrow stromal cells on porous scaffolds creates an osteoinductive environment for the differentiation of other marrow stromal cell populations. Therefore, bone tissue engineering constructs created by in vitro culture have excellent potential for bone regeneration applications in the clinic. However, more work is required to optimize this tissue engineering strategy. A biodegradable material with mechanical integrity similar to native bone and degradation properties similar to the rate of bone formation would be a more ideal scaffold material. It is also yet unclear what the optimum scaffold pore size and amount of in vitro generated extracellular matrix are to maximize bone formation. Finally, better characterization of the flow patterns within the flow perfusion bioreactor is needed to better understand the relationship between fluid shear and cell differentiation for creation of the ideal scaffold/culture combination.

Biocompatible Materials↗

PubMed2003

[Preparing trestle of tissue engineering for skin with collagen].

OBJECTIVE: To build the trestle of tissue engineering for skin with the collagen. METHODS: The collagen was obtained from the baby cattle hide pretreated by Na2S and elastinase and Protease M, then the collagen was dissolved in 0.5 mol/L acetic acid solution. The collagen was treated with Protease N to minimize its immunogenicity. The resulting collagen could be used to build the trestle of tissue engineering for skin because of good biocompatibility. The collagen molecular weight and structure were analyzed by SDS-PAGE. The bioactivity of trestle was tested in the experiment of the mice wound healing and the cell implantation. RESULTS: The SDS-PAGE result of the collagen treated by Protease M showed the typical spectrum of type I collagen. The built trestle was a collagen sponge matrix in which micropore size was 50-200 microns. It could accelerate wound healing and the implanted fibroblasts could proliferate well. CONCLUSION: The collagen treated by Protease N can get good biocompatibilily and is suitable for building the trestles of tissue engineering for skin with good bioactivity.

Animals↗

PubMed2002

In vivo evaluation of a bioactive scaffold for bone tissue engineering.

Revision cases of total hip implants are complicated by the significant amount of bone loss. New materials and/or approaches are needed to provide stability to the site, stimulate bone formation, and ultimately lead to fully functional bone tissue. Porous bioactive glasses (prepared from 45S5 granules, 45% SiO2, 24.5% Na2O, 24.5% CaO, and 6% P2O5) have been developed as scaffolds for bone tissue engineering and have been studied in vitro. In this study, we investigated the incorporation of tissue-engineered constructs utilizing these scaffolds in large, cortical bone defects in the rat simulating revision conditions. With implantation times of 2, 4, and 12 weeks the results were compared to those using the bioactive ceramic scaffold alone. Two tissue-engineered constructs were studied: osteoprogenitor cells that were either seeded onto the scaffold prior to implantation ("primary") or those that were culture expanded to form bonelike tissue on the scaffold prior to implantation ("hybrid"). Defects treated with the hybrid had the greatest amount of bone in the available pore space of the defect over all other groups at 2 weeks (p < 0.05). For both the primary and hybrid groups, woven and lamellar bone was present along the interface of the scaffold and the host cortex and within the porous space of the scaffold at 2 weeks. By 4 weeks, very uniform, lamellar bone was present throughout the scaffold for both tissue-engineered groups. The amount of bone significantly increased over time for all groups while the bioactive ceramic gradually resorbed by 40% at 12 weeks (p < 0.05). Structural properties of the treated long bones improved over time. Long bones treated with the hybrid had an early return in torsional stiffness by 2 weeks. Both tissue-engineered constructs achieved normal torsional strength and stiffness by 4 weeks as compared to the scaffold alone, which achieved this by 12 weeks. Porous, surface modified bioactive ceramic is a promising scaffold material for tissue-engineered bone repair.

Animals↗

PubMed2002

The design of scaffolds for use in tissue engineering. Part II. Rapid prototyping techniques.

Tissue engineering (TE) is an important emerging area in biomedical engineering for creating biological alternatives for harvested tissues, implants, and prostheses. In TE, a highly porous artificial extracellular matrix or scaffold is required to accommodate mammalian cells and guide their growth and tissue regeneration in three-dimension (3D). However, existing 3D scaffolds for TE proved less than ideal for actual applications because they lack mechanical strength, interconnected channels, and controlled porosity or pores distribution. In this paper, the authors review the application and advancement of rapid prototyping (RP) techniques in the design and creation of synthetic scaffolds for use in TE. We also review the advantages and benefits, and limitations and shortcomings of current RP techniques as well as the future direction of RP development in TE scaffold fabrication.

Animals↗

PubMed1998

Tissue engineering: the first decade and beyond.

This article reviews the important developments in the field of tissue engineering over the last 10 years. Research in the area of biomaterials is examined from the perspective of providing the foundation for the development of tissue engineering. Early efforts combining cells with biocompatible materials are described and applications of this technology presented, with particular focus on uses in orthopaedics and maxillofacial surgery. The basic principles of tissue engineering and state-of-the-art technology in cell biology and materials science as used currently in the field are presented. Finally, futures challenges are outlined from the perspective of integrating technologies from medicine, biology, and engineering, in hopes of translating tissue engineering to clinical applications.

Animals↗