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At least 1,711 records · Page 95Linked to original sources
PubMed2003

[Experimental study on constructing small-caliber artery by tissue engineering approach].

OBJECTIVE: To investigate the possibility of constructing small-caliber artery by means of tissue engineering. METHODS: Cell-PGA mixtures were made by separately seeding 1 x 10(7) smooth muscle cells and 5 x 10(6) endothelial cells isolated from neonate umbilicus onto PGA scaffold, the cell-PGA constructs were wrapped around a silicone tube before its implantation subcutaneously to nude mice and the mice were sacrificed in 2 and 6 weeks. The tissue engineered artery (TEA) were examined both grossly and immunohistochemically. RESULTS: The gross appearance of TEA was similar to that of the natural counterparts; histologic and immunohistochemical analyses of the neoformed tissues revealed a typical artery structure, including the presence of EC at the luminal surface and the presence of SMC and collagen in the wall. CONCLUSION: TEA with histology similar to natural vessel can be constructed by tissue engineering.

Animals↗
PubMed2003

[Biomechanical properties of tissue-engineered tendons after repairing digital flexor tendons in chickens].

Experiments have been performed to investigate why the biomechanical strength of repaired tendons is lower than that of the normal tendon when the engineered tendons are implanted in vivo to replace the tendon defects. We seeded the primary culture tendon cells derived from Roman chickens' digital flexor tendons on the degradable polyglycolic acid meshes to construct tissue-engineered tendons. The flexor tendon defects (0.5 cm-0.8 cm) excised in second digit bilaterally in 20 Roman chickens, had been repaired with the constructed tissue-engineered tendons. The samples of repaired tendons were collected at 2, 4, 6 and 8 weeks after operation. Tests for scaffold weight, hydroxyproline content, and mechanical strength of the samples were performed. We found that from 2 weeks to 8 weeks afteroperation, the weight of the scaffolds decreased significantly, almost disappearing at 8 weeks; the hydroxyproline content determining the total collagen content increased gradually without significance; mechanically, both energy at break and tensile strength showed a tendency of drastic decrease at first 4 weeks afteroperation and a gradual increase afterwards, but the tensile strength at 8 weeks afteroperation was only 23% of that of the normal tendon. We conclude that the lower biomechanical strength of repaired tendons is owing to the serious mismatch between scaffold degradation and collagen synthesis.

Achilles Tendon↗
PubMed2003

[Tissue engineering used in andrology].

Trauma, tumor, disease and congenital abnormalities may lead to genital organ damage or function failure, and consequently the requirement of its 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. These new techniques have been recently introduced into the field of andrology. Based on the latest advances, the present paper afferds a general prospect of the future direction of the development of tissue engineering in andrology.

Genitalia, Male↗
PubMed2003

Cartilage tissue engineering: controversy in the effect of oxygen.

Articular cartilage lacks the ability to repair itself and consequently defects in this tissue do not heal. Tissue engineering approaches, employing a scaffold material and cartilage producing cells (chondrocytes), hold promise for the treatment of such defects. In these strategies the limitation of nutrients, such as oxygen, during in vitro culture are of major concern and will have implications for proper bioreactor design. We recently demonstrated that oxygen gradients are indeed present within tissue engineered cartilaginous constructs. Interestingly, oxygen, besides being an essential nutrient, is also a controlling agent of developmental processes including cartilage formation. However, the specific role of oxygen in these processes is still obscure despite the recent advances in the field. In particular, the outcome of published investigations is inconsistent regarding the effect of oxygen tension on chondrocytes. Therefore, this article describes the possible roles of oxygen gradients during embryonic cartilage development and reviews the data reported on the effect of oxygen tension on in vitro chondrocyte proliferation and differentiation from a tissue engineering perspective. Furthermore, possible causes for the variance in the data are discussed. Finally, recommendations are included that may reduce the variation, resulting in more reliable and comparable data.

Animals↗
PubMed2004

[Stimulation of insulin-like growth factor-I to chondrogenesis of engineering cartilage tissue].

OBJECTIVE: To explore the ability of insulin-like growth factor-I (IGF-I) and hyaluracan acid in prompting chondrogenesis of engineering cartilage tissue. METHODS: Human articular chondrocytes were isolated and cultured in DMEM plus 10% fetal bovine serum. They were divided into three groups: hyaluracan acid + chondrocytes + IGF-I group (IGF-I group), hyaluracan acid + chondrocytes group (cell group), hyaluracan acid group (control group). The ability of chondrogenesis was investigated by HE and toluidine blue staining, human collagen II immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Both cell group and IGF-I group could develop into cartilage tissue in the sixth week while control group could not. The number of cartilage lacuna in IGF-I group were more than that in cell group. Human collagen II immunohistochemistry showed that there were stronger positive cell in IGF-I group than in cell group, collagen II mRNA expression was more higher and collagen I mRNA expression was lower in IGF-I group than in cell group. CONCLUSION: Insulin growth factor-I can prompt chondrogenesis of engineering cartilage tissue and ameliorate the quality of engineering cartilage tissue in vitro.

Cartilage, Articular↗
PubMed2004

[Reconstruction [correction to Reconstrction] of mandibular bone defects by using the techniques [correction to teachniques] of the reverse engineering and rapid prototyping].

OBJECTIVE: To evaluate the feasibility of designing and fabricating customized titanium bone substitutes to restore mandibular bone defects using reverse engineering (RE) and rapid prototyping (RP) techniques. METHODS: Titanium tray for mandibular defects were designed and fabricated through multi-step procedures of reverse engineering and rapid prototyping, then in operation it was filled with cancellous bone and fixed. RESULTS: The bone substitutes fabricated by this method had been successfully put into clinical use for maxillofacial surgery in 2 patients and got a satisfactory result. CONCLUSIONS: Reverse engineering combining with rapid prototyping could accomplish the design and manufacture of implant for the restoration of mandibular bone defects.

Adult↗
PubMed2004

[Experimental study on in vitro lamina propria engineering using oral fibroblast and polyglycolic acids].

PURPOSE: This study investigated the feasibility of lamina propria engineering in vitro using expanded oral fibroblast(OFC) and Polyglycolic Acids (PGA). METHODS: OFC were isolated by tissue explant method and expanded in vitro. OFC (20x10(6)) of 3rd passage were collected and then seeded onto PGA unwoven fibers to form a cell-scaffold. The constructs were cultured in DMEM +10% FBS. The cell-scaffold constructs were observed continuously by microscope. Small fragments were harvested at 1 week for electromicroscope, histological and RT-PCR analysis. RESULTS: At the sixth day, a neo-lamina propria was formed. HE and Masson stain revealed the formation of collagen fibers. RT-PCR revealed the new forming collagen was mainly type I collagen. CONCLUSION: lamina propria tissue is possible to engineer in vitro using oral fibroblast and polyglycolic acids. At this basis, we can construct bi-layer tissue engineering oral mucosa in the further research.

Fibroblasts↗
PubMed1992

Direct sequencing of baculovirus genomic DNA: sequence determination of the engineered respiratory syncytial virus chimeric FG gene.

Primer-directed enzymatic sequencing has proven to be an efficient and effective method for sequencing various size double-stranded DNA templates. We previously developed a primer-directed sequencing procedure for using double-stranded cosmid (50 kb) DNAs as template. We are interested in using this method to directly sequence larger DNA templates. Towards this goal we applied this method to directly sequence an engineered gene that had been transferred and integrated into the 130-kb baculovirus genome. Both crudely prepared and CsCl gradient-banded baculovirus DNAs were tested and reasonable sequencing ladders were obtained for both types of DNA templates. As little as 3 micrograms of gradient-banded baculovirus DNA were found to be sufficient to obtain film exposure times similar to those observed for cosmid size templates, 24 to 48 h. Effectiveness of the described method was demonstrated by obtaining the complete sequence of the engineered respiratory syncytial virus chimeric FG gene (2.5 kb in length) directly from the recombinant baculovirus "Baculo-FG" genome. Thus, our results demonstrate first, that double-stranded DNA templates as large as 130 kb can be sequenced directly and second, that the nucleotide sequence of engineered genes integrated within the baculovirus genome can be determined without the use of any intermediate steps of procedures.

Amino Acid Sequence↗
PubMed2004

[Induction of transforming growth factor-beta 1 and dentin non-collagen proteins on tissue engineering pulp].

OBJECTIVE: To study the influence of transforming growth factor-beta 1 (TGF-beta 1), dentin non-collagen proteins (dNCPs) and their complex on tissue engineering pulp system. METHODS: Collagen I and dentin powder were used to construct the system of pulp cells in 3-dimensional culture, dentin powder was added in the gel. The tissue engineering pulp were divided TGF-beta 1 group, dNCPs group, TGF-beta 1/dNCPs group and control group. After 3, 6 and 14 days, the appearance and the differentiation of pulp cells were observed by HE staining and immunohistochemical staining respectively. RESULTS: Collagen I could form netted collagen gel construction. Growing condition of pulp cells in gel was similar to that of pulp cells in vivo. After the TGF-beta 1 and dNCPs were added, the pulp cells had some characteristics of odontoblasts and had unilateral cell process after culture 6 days. Pulp cells arranged with parallel columnar and form dentin-pulp-like complex after 14 days. Immunohistochemical staining showed dentin salivary protein (DSP) began to express in some cells. The number of positive cell was most in the TGF-beta 1 group. No positive cells were detected in the control group. CONCLUSION: The transforming growth factor-beta 1 and non-collagen proteins can stimulate the pulp cells to transform into odontoblasts to some extent, which promote the formation of tissue engineering pulp.

Animals↗
PubMed2004

[Preliminary study on research method of cell survival rate at procedure of cryopreservation of tissue engineered tendons].

OBJECTIVE: To study the research method of cell survival rate at the procedure of cryopreservation of tissue engineered tendons. METHODS: In the 4th generation of human fibroblasts, the dead cells were stained with propidium iodine (PI), while the living cells with Hoechst 33342 (Ho). The living cells and dead cells emitted fluorescence of red and blue respectively after they were stimulated by suitable ultra-violet, then flow cytometry was applied to distinguish them. The seeding cells were collected to make them to be the cell suspension of suitable concentration (6.0 x 10(5) cell/ml) before they were divided into two parts. We cryopreserved and defrosted one part three times to kill the cells and did not cryopreserve the other part, then we made cell suspension at different ratios of cryopreserved cell to non-cryopreserved cells. The fluorescence staining and flow cytometry were used to study the correlation between cell ratios of cryopreserved cell to non-cryopreserved cell and the cell survival rates. We compared the cell survival rates between immediate flow cytometry and that 2 hours after fluorescence staining. RESULTS: The results of flow cytometry showed that correlation between the ratio of cryopreservation and the cell survival rate was significant (r = 0.970, P < 0.05), image analysis study also showed the correlation was significant (r = 0.982, P < 0.05). The cell survival rate decreased by use of flow cytometry two hours after fluorescence staining, but there was no significant difference when compared with that of immediate flow cytometry (P > 0.05). We could also observe the cells on the tissue engineered tendons by fluorescence image directly. CONCLUSION: Flow cytometry and fluorescence image after PI and Ho staining is a good way in study cell survival rate at the procedure of cryopreservation of tissue engineered tendons.

Cell Count↗
PubMed2004

Synthesis and evaluation of scaffolds prepared from chitosan fibers for potential use in cartilage tissue engineering.

Tissue engineering concepts and methodologies that employ biocompatible matrices or scaffolds have the potential to meet needs encountered in the repair of defects in articular cartilage. A desirable design parameter in the tissue engineering of cartilage in vitro is the development of seeded scaffolds with appropriate structure, composition, mechanical properties and durability that are similar to normal articular cartilage. Previous methods that have used freeze drying and lyophilization techniques to make foams and hydrogels have not met the scaffold characteristics (porosity, compressive elastic modulus, permeability and viscoelastic properties), which are required of scaffolds slated for use in cartilage tissue engineering applications. Thus there is an impetus to design and develop biomimetic scaffolds that mimic the native ECM of articular cartilage, and distribute strain in a bioresponsive manner to signal seeded chondrocytes to synthesize and organize ECM to result in material properties that are in range of natural cartilage. We have employed the method of electrospinning to prepare scaffolds with oriented and random fiber alignment.

Animals↗
PubMed2004

[Basic researches on cell adhesion and its application in tendon tissue engineering].

Cell adhesion is a basic and very important tissue in the field of tissue engineering. Fibronectin and integrins are the most important elements to cell adhesion. Some surface receptors of fibroblast can also conjugate with type I collagen in extracellular matrix (ECM) directly. Laminin receptors on the surface of fibroblast bound to laminin also play a role in cell adhesion. In this paper are reviewed a number of related articles. The structures and function of fibronectin and integrins are discussed in detail; the tendon cell's adhesion structures are also discussed. Yet, there was scarcely any paper on the effects which the preservation of tissue engineered products may have on cells' adhesion fo ECM. Therefore, researching on cell adhesion and finding a way of preservation that has no or very little adverse effect on cell adhesion is an important topic. Results from expected advanced researches on cell adhesion may probably find promising applications in the field of tissue engineering.

Cell Adhesion↗
PubMed2004

Environmental engineering education for developing countries: framework for the future.

This paper presents the existing philosophy, approach, criteria and delivery of environmental engineering education (E3) for developing countries. In general, environmental engineering is being taught in almost all major universities in developing countries, mostly under civil engineering degree programmes. There is an urgent need to address specific inputs that are particularly important for developing countries with respect to the reality of urbanisation and industrialisation. The main component of E3 in the near future will remain on basic sanitation in most developing countries, with special emphasis on the consumer-demand approach. In order to substantially overcome environmental problems in developing countries, E3 should include integrated urban water management, sustainable sanitation, appropriate technology, cleaner production, wastewater minimisation and financial framework.

Cities↗
PubMed2004

Ever deeper and wider: incorporating sustainability into a practitioner oriented engineering curriculum.

Whilst valuable debates about how best to plan, promote, and evaluate sustainable futures for our communities are conducted by governments and NGOs at global gatherings, there is an equal, and possibly more pressing, need to inspire and equip engineering graduates with the means to design and implement the required solutions. However, incorporation of sustainability as a subject into existing syllabi is problematic, primarily because of the need for students to acquire both holistic and context specific skills. This contribution first considers the reasons why we should be concerned with the integration of sustainability concepts into graduate and post-graduate curricula. We then go on to discuss the significance of cross-disciplinary thinking and skills as a key element of sustainability relevant knowledge. Finally, we report the design and deployment, within a water engineering degree course, of a post-graduate module in "Process design for sustainability". The implications of our experiences for the theory and practice of engineering education are examined and suggestions made concerning best practice.

Conservation of Natural Resources↗
PubMed2004

Adipose-derived adult stem cells for cartilage tissue engineering.

Tissue engineering is a promising therapeutic approach that uses combinations of implanted cells, biomaterial scaffolds, and biologically active molecules to repair or regenerate damaged or diseased tissues. Many diverse and increasingly complex approaches are being developed to repair articular cartilage, with the underlying premise that cells introduced exogenously play a necessary role in the success of engineered tissue replacements. A major consideration that remains in this field is the identification and characterization of appropriate sources of cells for tissue-engineered repair of cartilage. In particular, there has been significant emphasis on the use of undifferentiated progenitor cells, or "stem" cells that can be expanded in culture and differentiated into a variety of different cell types. Recent studies have identified the presence of an abundant source of stem cells in subcutaneous adipose tissue. These cells, termed adipose-derived adult stem (ADAS) cells, show characteristics of multipotent adult stem cells, similar to those of bone marrow derived mesenchymal stem cells (MSCs), and under appropriate culture conditions, synthesize cartilage-specific matrix proteins that are assembled in a cartilaginous extracellular matrix. The growth and chondrogenic differentiation of ADAS cells is strongly influenced by factors in the biochemical as well as biophysical environment of the cells. Furthermore, there is strong evidence that the interaction between the cells, the extracellular biomaterial substrate, and growth factors regulate ADAS cell differentiation and tissue growth. Overall, ADAS cells show significant promise for the development of functional tissue replacements for various tissues of the musculoskeletal system.

Adipocytes↗
PubMed2004

Considerations on the use of ear chondrocytes as donor chondrocytes for cartilage tissue engineering.

Articular cartilage is often used for research on cartilage tissue engineering. However, ear cartilage is easier to harvest, with less donor-site morbidity. The aim of this study was to evaluate whether adult human ear chondrocytes were capable of producing cartilage after expansion in monolayer culture. Cell yield per gram of cartilage was twice as high for ear than for articular cartilage. Moreover, ear chondrocytes proliferated faster. Cell proliferation could be further stimulated by the use of serum-free medium with Fibroblast Growth Factor 2 (FGF2) in stead of medium with 10% serum. To evaluate chondrogenic capacity, multiplied chondrocytes were suspended in alginate and implanted subcutaneously in athymic mice. After 8 weeks the constructs demonstrated a proteoglycan-rich matrix that contained collagen type II. Constructs of ear chondrocytes showed a faint staining for elastin. Quantitative RT-PCR revealed that expression of collagen type II was 2-fold upregulated whereas expression of collagen type I was 2-fold down regulated in ear chondrocytes expanded in serum-free medium with FGF2 compared to serum-containing medium. Expression of alkaline phosphatase and collagen type X were low indicating the absence of terminal differentiation. We conclude that ear chondrocytes can be used as donor chondrocytes for cartilage tissue engineering. Furthermore, it may proof to be a promising alternative cell source to engineer cartilage for articular repair.

Adult↗
PubMed2004

Long-term culture of tissue engineered cartilage in a perfused chamber with mechanical stimulation.

One approach to functional tissue engineering of cartilage is to utilize bioreactors to provide environmental conditions that stimulate chondrogenesis in cells cultured on biomaterial scaffolds. We report the combined use of a three-dimensional in vitro model and a novel bioreactor with perfusion of culture medium and mechanical stimulation in long-term studies of cartilage development and function. To engineer cartilage, scaffolds made of a non-woven mesh of polyglycolic acid (PGA) were seeded with bovine calf articular chondrocytes, cultured for an initial 30-day period under free swelling conditions, and cultured for an additional 37 day period in one of the three groups: (1) free-swelling, (2) static compression (on 24 h/day, strain control, static offset 10%), and (3) dynamic compression (on 1 h/day; off 23 h/day; strain control, static offset 2%, dynamic strain amplitude 5%; frequency 0.3 Hz). Constructs were sampled at timed intervals and assessed with respect to structure, biochemical composition, and mechanical function. Mechanical simulation had little effect on the compositions, morphologies and on mechanical properties of construct interiors discs, but it resulted in distincly different properties of the peripheral rings and face sides. Contructs cultured with mechanical loading maintained their cylindrical shape with flat and parallel top and bottom surfaces, and retained larger amounts of GAG. The modular bioreactor system with medium perfusion and mechanical loading can be utilized to define the conditions of cultivation for functional tissue engineering of cartilage.

Animals↗
PubMedDate not supplied

Tissue engineering: prospect for regenerating periodontal tissues.

New advancements in technological fields, continually has had a major impact on dental practice. The emergence of tissue engineering and biomimetic concepts has enhanced the predictability of existing therapy and also has radically recast approaches towards the dentoalveolar reconstruction. Tissue engineering in the simplest sense is a combination of material sciences and biology to repair tissues and organs which will unquestionably offer an exciting therapeutic alternative that have never been available before. This article is a brief introduction to the ever expanding field of tissue engineering and its possible implication in periodontal regeneration.

Cell Transplantation↗