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Results for “Tissue Engineering”

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At least 1,009 records · Page 56Linked to original sources

PubMed2005

[Transforming growth factor-beta1-loaded fibrin sealant promote bone marrow Mesenchymal stem cells to contract injectable tissue engineering cartilage in vivo].

OBJECTIVE: To investigate the feasibility that transforming growth factor-beta1 (TGF-beta1) -loaded fibrin sealant (FS) promotes bone marrow mesenchymal stem cells (BMSCs) to create tissue engineering cartilage in vivo. METHODS: The BMSCs were isolated from healthy human and amplified in vitro, and then induced by defined medium containing TGF-beta1 and dexamethasone. After 7 days the induced BMSCs were collected and mixed with TGF-beta1-loaded FS or FS as BMSCs+ FS-TGF-beta1 group and BMSCs+ FS experimental group. Then the mixture was injected by a needle into the dorsum of nude mice. In control group, only FS or BMSCs were injected. The tissue engineering specimens were harvested from nude mice 12 weeks later. Gross observation, average wet weight measurement, glycosaminoglycan (GAG) quantification, histology and immunohistochemistry were used to evaluate the results. RESULTS: The BMSCs have possessed the shape and functional characters of chondrocyte when transferred to a defined medium. After injection of the mixture, the cartilage-like tissue were formed in two experimental groups. Compared with BMSC+ FS group, the specimens of BMSCs +FS-TGF-beta1 group were larger and firmer. Alcian staining showed better metachromatic matrix formation. The GAG contents were significantly higher. Immunohistochemical staining of collagen type II was stronger. However, no cartilage-like tissue was formed in two control groups. CONCLUSION: TGF-beta1-loaded FS can promote BMSCs to contract injectable tissue engineering cartilage in vivo.

Animals↗

PubMed2006

Treatment of articular cartilage defects in horses with polymer-based cartilage tissue engineering grafts.

The objective of our study was to evaluate the integration of autologous cartilage tissue engineering transplants based on resorbable polyglactin/polydioxanone scaffolds into full-thickness cartilage defects of horses. Cartilage biopsies were taken from the non-load-bearing area of the lateral talus of the left tibiotarsal joint of eight healthy Haflinger horses. Tissue engineering cartilage transplants were generated by three-dimensional arrangement of autologous chondrocytes in biocompatible and resorbable polymer scaffolds. Full-thickness cartilage defects of 8 mm in diameter were created in the tubular bone condyle of the fetlock joint and cartilage grafts were fixed using an anchor system, while defects without grafting served as controls. After 6 and 12 months the repair tissue was evaluated histologically and showed formation of a cartilaginous tissue and good integration into the surrounding host tissue with firm bonding of the graft to the adjacent cartilage and the underlying subchondral bone. Biochemical analysis demonstrated that the content of glycosaminoglycans and hydroxyproline is comparable in repair tissue derived from treated and control defects. The use of three-dimensional autologous cartilage transplants based on resorbable polymer scaffolds ensures secure fixation, good integration of the graft into cartilage lesions, and is therefore suggested as a promising therapeutic option for the treatment of cartilage defects.

Animals↗

PubMed2006

Synthesis and characterization of macroporous poly(ethylene glycol)-based hydrogels for tissue engineering application.

Peptide activated poly(ethylene glycol) (PEG)-based hydrogels have received wide attention as material for tissue engineering application. However, the close structure of these materials may pose severe barriers to tissue invasion and nutrient transport. The aim of this work was to synthesize highly interconnected macroporous PEG hydrogels, suitable for use as tissue engineering scaffolds, by combining the photocrosslinking reaction with a foaming process. In particular, various porous samples, differing for both the polymer molecular weight and concentration in the starting precursor solution, have been prepared and characterized by means of scanning electron microscopy and mercury porosimetry. Moreover, water swelling properties have been evaluated and compared with those of the conventional nonporous ones, by performing both equilibrium and kinetic swelling measurements in distilled water. Results indicated that foamed hydrogels display a well-interconnected porous network, suitable for tissue invasion and free molecular trafficking within them. Pores dimension as well as swelling rate can be modulated by polymer concentrations and bubbling agent composition in the precursor solution.

Biocompatible Materials↗

PubMed2005

Liver tissue engineering at extrahepatic sites in mice as a potential new therapy for genetic liver diseases.

Liver tissue engineering using hepatocyte transplantation has been proposed as an alternative to whole-organ transplantation or liver-directed gene therapy to correct various types of hepatic insufficiency. Hepatocytes are not sustained when transplanted under the kidney capsule of syngeneic mice. However, when we transplanted hepatocytes with the extracellular matrix components extracted from Engelbreth-Holm-Swarm cells, hepatocytes survived for at least 140 days and formed small liver tissues. Liver engineering in hemophilia A mice reconstituted 5% to 10% of normal clotting activity, enough to reduce the bleeding time and have a therapeutic benefit. Conversely, the subcutaneous space did not support the persistent survival of hepatocytes with Engelbreth-Holm-Swarm gel matrix. We hypothesized that establishing a local vascular network at the transplantation site would reduce graft loss. To test this idea, we provided a potent angiogenic agent before hepatocyte transplantation into the subcutaneous space. With this procedure, persistent survival was achieved for the length of the experiment (120 days). To establish that these engineered liver tissues also retained their native regeneration potential in vivo, we induced two different modes of proliferative stimulus to the naive liver and confirmed that hepatocytes within the extrahepatic tissues regenerated with activity similar to that of naive liver. In conclusion, our studies indicate that liver tissues can be engineered and maintained at extrahepatic sites, retain their capacity for regeneration in vivo, and used to successfully treat genetic disorders.

Angiogenic Proteins↗

PubMed2004

Mechanical characterization of native and tissue-engineered cartilage.

Cartilage functions as a low-friction, wear-resistant, load-bearing tissue. During a normal gait cycle, one cartilage surface rolls and slides against another, all the while being loaded and unloaded. The durability of the tissue also makes for an impressive material to study. However, when cartilage is damaged or diseased, the tissue has little capacity to repair itself. The goal of cell-based repair strategies to replace damaged or diseased tissue requires that the functional biomechanical properties of normal (developing or mature), diseased, and repair cartilage be restored. This chapter addresses some of the major methods used to assess the biomechanical properties of native and tissue-engineered cartilage. First, the traditional methods of testing by compression, tension, shear, and indentation are reviewed. Next, additional methods to evaluate interfacial mechanics and lubrication are described. Thus, a variety of mechanical tests may be used to assess functional properties for normal, diseased, and tissue-engineered cartilage.

Animals↗

PubMed2000

[A tissue engineering approach to site-specific reconstruction of skeletal structures of the maxillofacial region:part I]

This article will present an image-based approach to design and manufacture of scaffolds for the tissue engineering of bone and cartilage constructs. Our vision of tissue-engineered bone and/or cartilage constructs utilizes 3-D designed and manufactured biodegradable scaffolds that are site specific for the area of maxillofacial reconstruction. The fabricated site-specific scaffold can be constructed such that it will impart biologic cues to implanted cells placed within its interstices. These biologic cues should influence scaffold implanted mesenchymal stem cells (MSC) or bone marrow stromal cells (BMSC) to form the necessary tissue for site specific facial reconstruction. This new approach to tissue engineering of the maxillofacial region would be advantageous because of its site-specific anatomical configuration as well as its potential ability to adapt to the functional forces placed on it during function. The reconstruction of the condylar-ramus area of the temporomandibular joint (TMJ) will be used as an illustration of this approach.

Journal Article↗

PubMed1999

[A review on the application of myoblast on gene therapy and tissue engineering].

OBJECTIVE: Because of its special biological characteristics, myoblast might play a role in gene delivery and cell-to-biomaterial interactions. In this paper, the biological features of myoblast and its application on gene therapy and tissue engineering was discussed. METHODS: Documents about proliferation and differentiation of myoblast were reviewed in details. The prospects of its application on gene therapy and tissue engineering were also presented. RESULTS: Myoblast was important in muscle regeneration. The activation of myoblast to proliferate and differentiate was the very beginning of regeneration after injury. The cultured myoblast had high potential to proliferate, it was ready to fuse with each other and to form myotube (the special behavior of myoblast differentiation). Myoblast transplantation had been studied as a possible treatment for inherited myopathies, such as Duchenne muscular dystrophy. The transplanted myoblast could fuse with host myofibers, so the delivered target gene integrated into host. Several myoblast-mediated gene delivery system had been established, including the gene delivery of human factor IX (hFIX), erythropoietin (EPO) and clony stimulating factor-1 (CSF-1). Results from animal experiments demonstrated that myoblast-mediated gene delivery could be used as gene therapy for some inherited diseases. And recently, some authors have shown great interest in the interaction between myoblast and type I collagen gels. It was found that myoblast could keep on proliferating and differentiating in collagen gels and could form discoid, tubular materials. CONCLUSION: Myoblast has great importance in gene therapy and tissue engineering. It is suggested that more efforts should be made in this field.

Cell Transplantation↗

PubMed2001

Biodegradable polymer scaffolds for cartilage tissue engineering.

Cartilage defects are common, painful conditions and none of the currently available treatment options are satisfactory. Tissue engineering techniques involving scaffolds made from biodegradable synthetic polymers hold great promise for the future. These materials can be manufactured in an injectable form for minimally invasive procedures or in a preformed state to treat large irreparable lesions including arthritis. The mechanical and biologic properties of synthetic polymers can be tailored to different clinical applications and engineering strategies. The scaffold serves as a mechanical substrate for cells and bioactive factors and can help direct and organize the process of regeneration. The ultimate goal of tissue engineering is to recapitulate normal organogenesis to create histologically and functionally normal tissue. A review of the characteristics and potential of synthetic polymers shows that these substances will play a major role in treating cartilage disorders.

Absorbable Implants↗

PubMed1998

Computer-assisted histometric analysis of tissue-engineered ovine bone.

OBJECTIVE: To develop a computer-assisted histometric technique that quantitatively determines the amount of regenerating bone, while excluding fibrovascular tissue and void spaces, in tissue-engineered bone constructs. To this end, a histometric technique was developed that couples digital tiling with adaptive, multiband color thresholding (AMBCT). STUDY DESIGN: To test the technique, a previously described model bone tissue-engineered construct filled with morcellized bone graft was employed. Histometric techniques were applied to quantify the amount of bone formed following eight weeks of implantation. RESULTS: The histometric technique was able to yield quantitative information regarding the amount of bone despite intrahistologic and interhistologic differences in staining. The technique is user friendly and highly automated. In addition to area fractions, the technique can provide bone ingrowth profiles as a function of geometry and implantation time. CONCLUSION: Digital tiling coupled with AMBCT offers an easy, fast and reproducible technique that aids in quantification of bone within histologic sections. In addition, the technique can be adapted to quantification of other tissues. Further studies are under way to investigate the potential of correlating the histometric technique with mechanical strength analyses of tissue-engineered bone specimens.

Animals↗

PubMed2004

Manufacture of elastic biodegradable PLCL scaffolds for mechano-active vascular tissue engineering.

A soft and very elastic poly(lactide-co-epsilon-caprolactone) (PLCL)(50:50, Mn 185 x 10(3)) was synthesized. Tubular scaffolds were prepared by an extrusion-particulate leaching method for mechano-active vascular tissue engineering. The copolymer was very flexible but completely rubber-like elastic. Even the high porous PLCL scaffolds (90% salt wt) exhibited 200% elongation, but recovery over 85% in a tensile test. Moreover, the PLCL scaffolds maintained their high elasticity also in culture media under cyclic mechanical strain conditions. The highly porous scaffold (90% salt wt) withstood for an initial 1 week without any deformation and sustained for 2 weeks in culture media under cyclic stress of 10% amplitude and at 1 Hz frequency which are similar to the natural vascular conditions. Vascular smooth muscle cells (VSMCs) were seeded on to the PLCL scaffolds. The cell adhesion and proliferation on the scaffolds of various pore-size were increased with increasing pore size. For the pore sizes of 50-100 microm, 100-150 microm, 150-200 microm and 200-250 microm, the ratios of cell numbers were about 1:1.2:1.9:2.2, respectively, at both 12 h and 5 days. Similarly, the higher porous scaffolds exhibited more cell adhesion and proliferation compared to lower porous one, where the effect was more pronounced in the longer proliferation period. SMC-seeded scaffolds were implanted subcutaneously in athymic nude mice to confirm the biocompatibility. Such a high elastic property and proper biocompatibility to SMCs of PLCL scaffolds prepared in this study will be very useful to engineer SM-containing tissues such as blood vessels under mechanically dynamic environments (mechano-active tissue engineering).

Animals↗

PubMed2000

Tissue engineering in cardiovascular surgery: new approach to develop completely human autologous tissue.

OBJECTIVE: In cardiovascular tissue engineering, three-dimensional scaffolds serve as physical supports and templates for cell attachment and tissue development. Currently used scaffolds are still far from ideal, they are potentially immunogenic and they show toxic degradation and inflammatory reactions. The aim of this study is to develop a new method for a three-dimensional completely autologous human tissue without using any scaffold materials. METHODS: Human aortic tissue is harvested from the ascending aorta in the operation room and worked up to pure human myofibroblasts cultures. These human aortic myofibroblasts cultures (1.5x10(6) cells, passage 3) were seeded into 15-cm culture dishes. Cells were cultured with Dulbecco' s modified Eagle's medium supplemented with 1 mM L-ascorbic acid 2-phosphate for 4 weeks to form myofibroblast sheets. The harvested cell sheets were folded to form four-layer sheets. The folded sheets were then framed up and cultured for another 4 weeks. Tissue development was evaluated by biochemical assay and light and electron microscopy. RESULTS: After 4 weeks of culture in ascorbic acid supplemented medium, myofibroblasts formed thin cell sheets in culture dishes. The cell sheets presented in a multi-layered pattern surrounded by extracellular matrices. Cultured for additional 4 weeks on the frames, the folded sheets further developed into more solid and flexible tissues. Light microscopy documented a structure resembling to a native tissue with confluent extracellular matrix. Under transmission electron microscope, viable cells and confluent bundles of striated mature collagen fibers were observed. Hydroxyproline assays showed significant increase of collagen content after culturing on the frames and were 80.5% of that of natural human pericardium. CONCLUSIONS: Improved cell culture technique may render human aortic myofibroblasts to a native tissue-like structure. A three-dimensional completely autologous human tissue may be further developed on the base of this structure with no show toxic degradation or inflammatory reactions.

Analysis of Variance↗

PubMed2006

Production of extracellular matrix components in tissue-engineered blood vessels.

Morphology and compliance of tissue-engineered blood vessels (TEBV) are dependent on the culture period and production of extracellular matrix (ECM) components in order to increase the strength of the developing tissue. The aim of the present study was to evaluate the potential of TEBVs to produce an ECM similar to native arteries and veins. Human smooth muscle cells (SMC) were seeded onto the poly(glycolic acid) (PGA) scaffold and placed in bioreactors filled with DMEM supplemented with growth factors. After 6 weeks, the vessels were harvested from the bioreactors and seeded with human endothelial cells at the lumen for another 3 days. Then, the TEBVs were harvested for RNA and protein isolation for further RT-PCR and Western blot. TEBVs had a similar macroscopic appearance to that of native vessels with no visible evidence of the original PGA. Histological and immunohistochemical analyses indicated the presence of high cell density and development of a highly organized structure of ECM. After 6 weeks of culture, there were significantly lower gene expression of SMC-specific markers, such as alpha-actin, caldesmon, and vimentin, and proteoglycans, such as biglycan, decorin, and versican, and other ECM components, such as collagen I and elastin, in TEBVs, with and without pulsatile conditions, compared to that of native arteries. Gene expression of fibronectin was significantly lower in TEBVs grown during pulsatile conditions compared to that of native arteries. No difference was observed in TEBVs grown during non-pulsatile conditions. The presence of alpha-actin, collagen I, decorin, and fibronectin at protein level was demonstrated in TEBVs with and without pulsatile conditions after 6 weeks and in native veins and arteries as well. How this deviation translates into mechanical properties remains to be explored.

Bioreactors↗

PubMed2004

[Construct tissue-engineered bone by co-seeding marrow stromal cells and endothelial cells].

To identify the role of co-seeding marrow stromal cells (MSCs) and endothelial cells (ECs) onto biocomposite in constructing tissue-engineered bone for promoting osteogenesis and angiogenesis, we seeded rat marrow stromal cells (rMSCs) and human umbilical vein endothelial cells (hUVECs) onto poly (L-lactic acid)/beta-tricalcium phosphate (PLLA/beta-TCP) macroporous composite (the test group), and seeded rMSCs onto the same kind of composite (the control group). We implanted these biocomposites into the thighs of nude mice intramuscularly and sacrificed these mice at 1, 4, 8, 12, 16 weeks after implantation, respectively. Biocomposites were taken out and histomorphometry was performed. Image manipulation technology was used to calculate the percentages of new bone area and material area in the test group and control group. We found that the percentage of new bone area of test group increased faster than that of control group, the percentage of material of test group decreased faster than that of control group, and the growth of capillary network of test group was much better than that of control group. These results suggest that co-seeding MSCs and ECs onto scaffold for constructing tissue-engineered bone is beneficial to osteogenesis, to angiogenesis in the prosthesis, and to the degradation of scaffold, and it is of significance in the research of bone tissue engineering.

Absorbable Implants↗

PubMed2006

Decellularization does not eliminate thrombogenicity and inflammatory stimulation in tissue-engineered porcine heart valves.

BACKGROUND AND AIM OF THE STUDY: In tissue engineering of heart valves using decellularized xenogenic valves, it has been suggested that cell elimination would result in a biologically inert matrix. The aim of this in-vitro investigation was to evaluate different decellularization methods in regard to the completeness of cell removal, inflammatory response, and thrombocyte activation. METHODS: Decellularized porcine Synergraft valves were compared with porcine pulmonary conduits decellularized with Triton X-100, sodium deoxycholate, Igepal CA-630 and ribonuclease. Completeness of decellularization was evaluated with staining for nuclei and alpha-Gal epitope. Decellularized heart valves with and without seeding with endothelial cells (ECs) were incubated with human platelet-rich plasma and stained for CD41 and PAC-1 to evaluate thrombocyte activation. Samples were processed for laser scanning microscopy (LSM) and scanning electron microscopy (SEM). Migration of human monocytic cells towards extracted valve proteins was tested. RESULTS: In contrast to the Synergraft, complete cell removal and elimination of the alpha-gal epitope was achieved with the new decellularization method. Numerous adherent and activated platelets were found on the decellularized matrix. This was inhibited by seeding with ECs. Even in completely cell-free valve tissue extracellular matrix proteins attracted human monocytic cells as in early inflammation, depending on whether porcine or human tissue was used. CONCLUSION: Important differences were found in the decellularization efficacy of treatment methods. However, even complete elimination of cells and their remnants did not result in a biologically inert matrix. The decellularized porcine heart valve matrix has the potential to attract inflammatory cells and to induce platelet activation. These findings suggest that it will be important to control the different inflammation-stimulating factors if porcine tissues are to be used successfully in tissue engineering.

Animals↗

PubMed2000

Reflections on tissue engineering and trauma therapy.

Although all of Trauma Care has remarkably improved during the latter half of the last century the treatment of burn injury has substantially out paced other areas and serves as an excellent example illustrating the improvements taking place in the treatment of injured patients. Although Trauma treatment lagged behind the rest of medicine in mid-century today it rests solidly on the cutting edge of advancing therapeutic knowledge and practice in areas of metabolism, immunology, infection control, critical care, tissue engineering and the delivery of clinical care. It is important to understand what has happened to allow the treatment of injury to be so effective. The bench mark therapeutic moves that have had major effects allowing the present highly effective treatment are: immediate tailored fluid resuscitation, preventive (prophylactic) and topical antibiotics, metabolically designed nutritional therapy and most important early definitive repair of the injury. All must be delivered early after trauma if they are to be optimally effective in preventing the complications of injury that are devastating if encountered. Unfortunately, all problems are not solved by todays treatment of injury, improved as it is. These problems are largely related to an inexact understanding: of the physiologic changes of aging, of the exact pathophysiologic events in inhalation injury and multisystem organ failure and of the technology required to replace those body parts damaged by the injury itself that lead to death or to healing with loss of function. There will be major improvements in the understanding and ability to effectively deal with the problems of aging and inhalation injury through basic and clinical research but perhaps the major improvement in injury treatment will come through the ability to replace worn out, defective or damaged body parts through technologies that resemble regeneration. Here the concepts of Tissue Engineering have much to contribute and it is worth exploring the donation of Tissue Engineering to dermal replacement following burn injury to serve as an example of what types of additions to treatment Tissue Engineering can make.

Burns↗

PubMed2001

Degradable and injectable poly(aldehyde guluronate) hydrogels for bone tissue engineering.

Degradable and injectable hydrogels may be ideal for bone-tissue engineering, especially in the craniofacial region because of the ease of access for injection. Alginate hydrogels potentially could be used as injectable cell delivery vehicles, but they exhibit a limited range of mechanical properties and uncontrollable disintegration time. Therefore we synthesized new hydrogels, composed of poly(aldehyde guluronate) (PAG) and adipic acid dihydrazide, that have a wide range of mechanical stiffness and controllable degradation rate. MC3T3-E1 cells adhered and multiplied on PAG hydrogels in vitro. When primary rat calvarial osteoblasts were mixed with PAG hydrogels and subcutaneously injected into the backs of mice, mineralized bone tissues were formed 9 weeks following implantation. These hydrogels may find wide utility as an injectable delivery system for bone precursor cells as well as for other applications in tissue engineering.

3T3 Cells↗

PubMed1999

Tissue-engineered skin substitutes.

The development of tissue engineered skin substitutes has reached a mature stage; major remaining questions relate to areas of greatest potential utility. Research is mainly concerned with extending indications of existing products, including treatment of the full range of acute, chronic, surgical and cosmetic wounds, and in other applications such as soft tissue augmentation and gene delivery. Among the few advances in the composition of skin substitutes is the inclusion of endothelial cells to provide a pathway for vascularisation by the host system.

Journal Article↗

PubMed2005

The potential of tissue engineering in orthopedics.

This article presents models of human phalanges and small joints developed by tissue engineering. Biodegradable polymer scaffolds support growth of osteoblasts, chondrocytes, and tenocytes after implantation of the models in athymic mice. The cell-polymer constructs are vascularized by the host mice, form new bone, cartilage, and tendon with characteristic gene expression and protein synthesis and secretion, and maintain the shape of human phalanges with joints. The study demonstrates critical progress in the design and fabrication of bone, cartilage, and tendon by tissue engineering and the potential of this field for human clinical orthopedic applications.

Animals↗