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At least 1,153 records · Page 64Linked to original sources
PubMed2005

Clinical case reports of injectable tissue-engineered bone for alveolar augmentation with simultaneous implant placement.

This clinical study was undertaken to evaluate the use of tissue-engineered bone, mesenchymal stem cells, platelet-rich plasma, and beta-tricalcium phosphate as grafting materials for maxillary sinus floor augmentation or onlay plasty with simultaneous implant placement in six patients with 3- to 5-mm alveolar crestal bone height. All 20 implants were clinically stable at second-stage surgery and 12 months postloading. A mean increase in mineralized tissue height of 7.3+/-4.6 mm was evident when comparing the pre- and postsurgical radiographs. Injectable tissue-engineered bone provided stable and predictable results in terms of implant success.

Absorbable Implants↗
PubMed2002

A tissue-engineering model for the manufacture of auricular-shaped cartilage implants.

The established surgical methods of external ear reconstruction using autogenous tissue represent the current state of the art. Because of the limited possibilities for shaping conventional harvested autogenous rib cartilage, the cosmetic results of auricular reconstruction are frequently unsatisfactory. Tissue engineering could represent an alternative technique for obtaining a precisely shaped cartilage implant that avoids donor site morbidity and unsatisfactory cosmetic results. In this study, the reliability and quality of a tissue-engineering model for the manufacture of auricular-shaped human cartilage implants was investigated, focusing on the feasibility of the manufacturing process and the in vivo and in vitro maturation of an extracellular cartilage-like matrix. Implants were molded within an auricular-shaped silicone cylinder, and human nasal septal chondrocytes crosslinked by human fibrin within bioresorbable PGLA-PLLA polymer scaffolds were used. After an in vitro incubation of up to 6 weeks, defined fragments of the prefabricated auricular-shaped construct were implanted subcutaneously on the backs of nude mice for at least 6 to 12 weeks ( n=7). Scaffolds without cell loading served as controls. Macroscopic and histochemical examination after 3 and 6 weeks in vitro showed a solid compound of homogenously distributed chondrocytes within the polymer scaffold, leading only to a limited pericellular matrix formation. Analysis after 6 and 12 weeks of in vivo maturation demonstrated a solid tissue compound and neocartilage formation with the presence of cartilage-specific matrix components. Implants obtained shape and size during the entire period of implantation. The model of cartilage implant manufacturing presented here meets all biocompatible requirements for in vitro prefabrication and in vivo maturation of autogenous, individually shaped cartilage transplants.

Animals↗
PubMed2004

Tissue engineering, stem cells, cloning, and parthenogenesis: new paradigms for therapy.

: BACKGROUND: Patients suffering from diseased and injured organs may be treated with transplanted organs. However, there is a severe shortage of donor organs which is worsening yearly due to the aging population. Scientists in the field of tissue engineering apply the principles of cell transplantation, materials science, and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Both therapeutic cloning (nucleus from a donor cell is transferred into an enucleated oocyte), and parthenogenesis (oocyte is activated and stimulated to divide), permit extraction of pluripotent embryonic stem cells, and offer a potentially limitless source of cells for tissue engineering applications. The stem cell field is also advancing rapidly, opening new options for therapy. The present article reviews recent progress in tissue engineering and describes applications of these new technologies that may offer novel therapies for patients with end-stage organ failure.

Journal Article↗
PubMed1999

Animal models of tendon and ligament injuries for tissue engineering applications.

Improved methods are needed for prevention and treatment of injuries to the musculoskeletal soft tissues. Tissue engineering techniques have led to more effective clinical protocols for treating these injuries. Improvement of tissue healing through the addition of biologic factors, and the development of biologically active tissue engineered replacements, are two promising areas of research. An essential component of progress in this field is the use of animal models of tendon and ligament injuries, which allows for rigorous testing of hypotheses related to disease pathogenesis and treatment. Because these animal models must be appropriate for the condition being studied, no single model exists that is appropriate for all investigations. It generally is necessary to differentiate between tendon and ligament tissues. Furthermore, ligaments should be divided into intraarticular and extraarticular models, whereas tendons should be divided into intrasynovial and extrasynovial models. Other important factors in the appropriate use of an animal model include size of the animal, anatomic features, and techniques available for tissue analysis. The tissues used should be large enough to allow for accurate and reproducible manipulations (injury creation, repair, reconstruction). In addition, it is preferable to use tissues that are amenable to quantitative analysis.

Animals↗
PubMed2005

Repairing of goat tibial bone defects with BMP-2 gene-modified tissue-engineered bone.

Bone defects larger than a critical size are major challenges in orthopedic medicine. We combined tissue-engineered bone and gene therapy to provide osteoprogenitor cells, osteoinductive factors, and osteo-conductive carrier for ideal bone regeneration in critical-sized bone defects. Goat diaphyseal bone defects were repaired with tissue and genetically engineered bone implants, composed of biphasic calcined bone (BCB) and autologous bone marrow derived mesenchymal stem cells (BMSC) transduced with human bone morphogenetic protein-2 (hBMP-2). Twenty six goats with tibial bone defects were divided into groups receiving implants by using a combination of BCB and BMSCs with or without the hBMP-2 gene. In eight goats that were treated with BCB that contained hBMP-2 transduced BMSC, five had complete healing and three showed partial healing. Goats in other experimental groups had only slight or no healing. Furthermore, the area and biochemical strength of the callus in the bone defects were significantly better in animals treated with genetically engineered implants. We concluded that the combination of genetic and tissue engineering provides an innovative way for treating critical-sized bone defects.

Animals↗
PubMed2006

Tissue engineered heart valves based on human cells.

Valvular heart disease is still a significant cause of morbidity and mortality worldwide. Clinically used valve replacements including mechanical valves as well as fixed biological xeno- or homografts are associated with several major disadvantages. Alternatively, tissue engineering aims at the fabrication of autologous living cardiovascular replacements with the potential to grow and to repair, particularly for paediatric applications. Therefore, autologous cells are harvested and seeded onto three-dimensional matrices followed by biomimetic in vitro conditioning enabling the development of the neo-heart valve tissue. Here, we review different human cell sources such as vessels, bone marrow, umbilical cord tissue and blood, and chorionic villi with particular regard to cell phenotypes and their suitability for extracellular matrix production for tissue engineering purposes.

Absorbable Implants↗
PubMed2003

Experimental approaches to study vascularization in tissue engineering and biomaterial applications.

The success of tissue engineering and biomaterial applications is not only dependent on the growth and functioning of the organ- or tissue-specific cells on the biomaterial but is entirely dependent in most cases on a successful vascularization after implantation. The process of vascularization involves angiogenesis; the formation of new blood vessels which spread into the implant material and supply the existing cells with the nutrients to survive. We have established in vitro methods using human microvascular endothelial cells to evaluate novel biomaterials for endothelial cell attachment, cytotoxicity, growth, angiogenesis and the effects on gene regulation. These in vitro studies can be used to rapidly evaluate the potential success of a new biomaterial and for the development of matrix scaffolds which will promote a physiological vascularization response.

Journal Article↗
PubMed2005

Development of a tissue-engineered human oral mucosa equivalent based on an acellular allogeneic dermal matrix: a preliminary report of clinical application to burn wounds.

Tissue-engineered skin equivalents composed of epidermal and dermal components have been widely investigated for coverage of full-thickness skin defects. We developed a tissue-engineered oral mucosa equivalent based on an acellular allogeneic dermal matrix and investigated its characteristics. We also tried and assessed its preliminary clinical application. Human oral mucosal keratinocytes were separated from a piece of oral mucosa and cultured in a chemically-defined medium. The keratinocytes were seeded on to the acellular allogeneic dermal matrix and cultured. Histologically, the mucosa equivalent had a well-stratified epithelial layer. Immunohistochemical study showed that it was similar to normal oral mucosa. We applied this equivalent in one case with an extensive burn wound. The equivalent was transplanted three weeks after the harvest of the patient's oral mucosa and about 30% of the graft finally survived. We conclude that this new oral mucosa equivalent could become a therapeutic option for the treatment of extensive burns.

Burns↗
PubMed2005

Tissue engineering skin: a paradigm shift in wound care.

Tissue-engineered skin for the treatment of burns and ulcers is a clinical success, but making it commercially viable is more problematic. This article examines the industry, its techniques and suggests the way forward.

Animals↗
PubMedDate not supplied

Tissue-engineered hybrid tooth and bone.

Tooth loss accompanied by alveolar bone resorption presents a significant clinical problem. We have investigated the utility of a tissue-engineering approach to provide corrective therapies for tooth-bone loss. Hybrid tooth-bone tissues were bioengineered as follows. Tooth implants were generated from pig third molar tooth bud cells seeded onto polyglycolide (PGA) and polyglycolide-colactide (PLGA) scaffolds, and grown for 4 weeks in the omenta of adult rat hosts. Bone implants were generated from osteoblasts induced from bone marrow progenitor cells obtained from the same pig, seeded onto PLGA fused wafer scaffolds, and grown for 10 days in a rotational oxygen-permeable bioreactor system. The tooth and bone implants were harvested, sutured together, reimplanted, and grown in the omenta for an additional 8 weeks. Histological and immunohistochemical analyses of the excised hybrid tooth-bone constructs revealed the presence of tooth tissues, including primary and reparative dentin and enamel in the tooth portion of hybrid tooth-bone implants, and osteocalcin and bone sialoprotein-positive bone in the bone portion of hybrid tooth-bone constructs. Collagen type III-positive connective tissue resembling periodontal ligament and tooth root structures were present at the interface of bioengineered tooth and bone tissues. These results demonstrate the utility of a hybrid tooth-bone tissue-engineering approach for the eventual clinical treatment of tooth loss accompanied by alveolar bone resorption.

Animals↗
PubMed1996

Tissue-engineered skeletal muscle organoids for reversible gene therapy.

Genetically modified murine skeletal myoblasts were tissue engineered in vitro into organ-like structures (organoids) containing only postmitotic myofibers secreting pharmacological levels of recombinant human growth hormone (rhGH). Subcutaneous organoid implantation under tension led to the rapid and stable appearance of physiological sera levels of rhGH for up to 12 weeks, whereas surgical removal led to its rapid disappearance. Reversible delivery of bioactive compounds from postmitotic cells in tissue engineered organs has several advantages over other forms of muscle gene therapy.

Animals↗
PubMed2000

A study of injectable tissue-engineered autologous cartilage.

OBJECTIVE: To test the effectiveness of the new techniques of tissue-engineered cartilage. METHODS: Chondrocytes were harvested through type II collagenase digestion from the auricle of New Zealand rabbits. The cells were mixed with alginate to generate chondrocytes/alginate composites with final cellular density of 50 x 10(6) per mL. Calcium chloride was used as the cross-linking agent to gel the aqueous alginate solution. The chondrocytes/alginate composites were injected into the dorsal subcutaneous tissue of New Zealand rabbits through autologous cells grafts. The specimens were observed during cartilage formation at 4, 8, and 12 weeks after injection. RESULTS: Prior to harvesting, chondrocytes/alginate composites were easily visualized under the dorsal skin of animals. The appearance of experimental specimens was similar to that of native cartilage in gross morphology. Using a standard hematoxylin and eosin stain, the histologic features of all experimental specimens demonstrated new cartilage formation. With a Masson's trichrome and safranin O stain, the presence of collagen and glycosaminoglycan (GAG) was observed at 8 and 12 weeks. CONCLUSION: This study demonstrated that polymerization of alginate hydrogel can be controlled to allow injection of chondrocytes that produce new autologous cartilage at subcutaneous dorsal site of rabbits. Injectable tissue-engineered autologous cartilage is promising for potential use in oral and maxillofacial surgery.

Alginates↗
PubMed2001

Oxygen tension influences proliferation and differentiation in a tissue-engineered model of placental trophoblast-like cells.

A considerable oxygen gradient exists in vivo, which exerts regulatory effects on tissue development and function. The objective of this study was to evaluate the feasibility of controlling cell proliferation and differentiation by regulating oxygen tension in a tissue-engineered bioreactor model. The effects of oxygen tension on proliferation and differentiation of first-trimester human trophoblast cells (known as ED(27) cells) were studied in a fiber-bed perfusion bioreactor system in which cells were grown in polyethylene terephthalate (PET) nonwoven fibrous matrix. By varying the oxygen tension between 2% and 20%, differential responses of trophoblasts in their proliferation and differentiation activities were observed. There was no significant difference in the rates of glucose consumption and lactate production, and lactate dehydrogenase (LDH) level in the culture media for both 2% and 20% oxygen tension cultures, indicating that cell metabolic activities were not limited by low oxygen tension. However, 2% oxygen stimulated cell proliferation but impeded the secretion of a functional hormone, 17beta-estradiol. In contrast, 20% oxygen tension reduced cell proliferation, but yielded higher hormone secretion. A step change in oxygen tension from 2% to 20% caused cells in the bioreactor to increase 17beta-estradiol secretion and shifted cell cycle from proliferation to differentiation, which were verified with the expression levels of cyclin B1 and p27(kip1). However, no significant response to a change from 6% to 20% oxygen tension was observed. It is concluded that changes in oxygen tension can be an effective strategy to control cell cycle and long-term tissue development. This work also demonstrated the important role of oxygen tension in regulating placental trophoblast tissue development and the feasibility of using the bioreactor under well-controlled physiological environment for tissue engineering applications.

Bioreactors↗
PubMed2001

Stem cells in tissue engineering.

The concept of producing 'spare parts' of the body for replacement of damaged or lost organs lies at the core of the varied biotechnological practices referred to generally as tissue engineering. Use of postnatal stem cells has the potential to significantly alter the perspective of tissue engineering. Successful long-term restoration of continuously self-renewing tissues such as skin, for example, depends on the use of extensively self-renewing stem cells. The identification and isolation of stem cells from a number of tissues provides appropriate targets for prospective gene therapies.

Animals↗
PubMed2003

Gene therapy and tissue engineering in repair of the musculoskeletal system.

Historically, surgeons have sought and used different procedures in order to augment the repair of various skeletal tissues. Now, with the completion of the Human Genome Project, many researchers have turned to gene therapy as a means to aid various ailments. In the orthopedic field, many strides have been made toward using gene therapy and tissue engineering in a clinical setting. In this review, several studies are outlined in different areas that gene therapy has or will influence orthopedic surgery. Gene therapy and tissue engineering can aid in fracture healing and spinal fusions by inducing bone formation, ligamentous repairs by increasing the production of connective tissue fibers, intervertebral disc disease by creating potential replacements, and articular cartilage repairs by providing means to improve cartilage. As we continue to see great contributions, such as the few mentioned here, this field will continue to mature and develop.

Animals↗
PubMedDate not supplied

Characterization of the cellular origin of a tissue-engineered human phalanx model by in situ hybridization.

Tissue-engineered models of human phalanges have previously been fabricated from a combination of bovine periosteum, cartilage, tendon, and biodegradable polyglycolic acid and poly-L-lactic acid scaffolds. Resulting constructs implanted in athymic mice for more than 40 weeks developed new bone, cartilage, and tendon and became vascularized, but cell types comprising the constructs were unidentified. The origin of cells in middle phalanx models implanted for 20 weeks in nude mice has been studied by in situ hybridization analyzing species-specific gene expression. Oligonucleotide probes homologous to species-specific gene sequences of bovine type II and X collagen, aggrecan, bone sialoprotein, biglycan, and osteopontin, and mouse decorin were labeled with (35)S and hybridized to respective serial sections of bovine tissue, mouse tissue, and phalanx constructs. In situ hybridization showed positive message and tissue-specific localization for all bovine-specific probes examined within cartilaginous and midshaft portions of constructs and negative message for the mouse-specific decorin probe. These data show that osteoblasts and chondrocytes comprising constructs are derived exclusively from their original bovine sources over 20 weeks of implantation. Defining the cellular origin of the models lends insight into their biological, chemical, and physical nature and their growth and development. Maintenance of their initial genotype is crucial for future application of the models in augmenting impaired human phalanges and related tissues.

Animals↗
PubMed2001

Tissue-engineered fabrication of an osteochondral composite graft using rat bone marrow-derived mesenchymal stem cells.

This study tested the tissue engineering hypothesis that construction of an osteochondral composite graft could be accomplished using multipotent progenitor cells and phenotype-specific biomaterials. Rat bone marrow-derived mesenchymal stem cells (MSCs) were culture-expanded and separately stimulated with transforming growth factor-beta1 (TGF-beta1) for chondrogenic differentiation or with an osteogenic supplement (OS). MSCs exposed to TGF-beta1 were loaded into a sponge composed of a hyaluronan derivative (HYAF-11) for the construction of the cartilage component of the composite graft, and MSCs exposed to OS were loaded into a porous calcium phosphate ceramic component for bone formation. Cell-loaded HYAFF-11 sponge and ceramic were joined together with fibrin sealant, Tisseel, to form a composite osteochondral graft, which was then implanted into a subcutaneous pocket in syngeneic rats. Specimens were harvested at 3 and 6 weeks after implantation, examined with histology for morphologic features, and stained immunohistochemically for type I, II, and X collagen. The two-component composite graft remained as an integrated unit after in vivo implantation and histologic processing. Fibrocartilage was observed in the sponge, and bone was detected in the ceramic component. Observations with polarized light indicated continuity of collagen fibers between the ceramic and HYAFF-11 components in the 6-week specimens. Type I collagen was identified in the neo-tissue in both sponge and ceramic, and type II collagen in the fibrocartilage, especially the pericellular matrix of cells in the sponge. These data suggest that the construction of a tissue-engineered composite osteochondral graft is possible with MSCs and different biomaterials and bioactive factors that support either chondrogenic or osteogenic differentiation.

Animals↗