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At least 757 records · Page 42Linked to original sources

PubMed2004

Tissue-engineered rabbit cranial suture from autologous fibroblasts and BMP2.

Craniosynostosis is a congenital disorder of premature ossification of cranial sutures, occurring in one of approximately every 2500 live human births. This work addressed a hypothesis that a cranial suture can be tissue-engineered from autologous cells. Dermal fibroblasts were isolated subcutaneously from growing rabbits, culture-expanded, and seeded in a gelatin scaffold. We fabricated a composite tissue construct by sandwiching the fibroblast-seeded gelatin scaffold between two collagen sponges loaded with recombinant human BMP2. Surgically created, full-thickness parietal defects were filled with the composite tissue construct in the same rabbits from which dermal fibroblasts had been obtained. After four-week in vivo implantation, there was de novo formation of tissue-engineered cranial suture, microscopically reminiscent of the adjacent natural cranial suture. The tissue-engineered cranial suture showed radiolucency on radiographic images, in contrast to radio-opacity of microscopically ossified calvarial defects filled with fibroblast-free, BMP2-loaded constructs. This approach may be refined for tissue engineering of cranial sutures for craniosynostosis patients.

Analysis of Variance↗

PubMedDate not supplied

Tissue engineering of recellularized small-diameter vascular grafts.

A tissue-engineered small-diameter arterial graft would be of benefit to patients requiring vascular reconstructive procedures. Our objective was to produce a tissue-engineered vascular graft with a high patency rate that could withstand arterial pressures. Rat arteries were acellularized with a series of detergent solutions, recellularized by incubation with a primary culture of endothelial cells, and implanted as interposition grafts in the common femoral artery. Acellular grafts that had not been recellularized were implanted in a separate group of control animals. No systemic anticoagulants were administered. Grafts were explanted at 4 weeks for definitive patency evaluation and histologic examination; 89% of the recellularized grafts and 29% of the control grafts remained patent. Elastin staining demonstrated the preservation of elastic fibers within the media of the acellular grafts before implantation. Immunohistochemical staining of explanted grafts demonstrated a complete layer of endothelial cells on the lumenal surface in grafts that remained patent. Smooth muscle cells were observed to have repopulated the vessel walls. The mechanical properties of the matrix were comparable to native vessels. Such a strategy may present an alternative to autologous harvest of small vessels for use in vascular bypass procedures.

Animals↗

PubMedDate not supplied

Perfusion bioreactor for small diameter tissue-engineered arteries.

A scaleable perfusion bioreactor has been developed for tissue engineering of small diameter arterial constructs. This modular bioreactor allows for dynamic sequential seeding of smooth muscle and endothelial cells, biomechanical stimulation of cells during culture, and monitoring of tissue growth and maturation. Bovine aortic smooth muscle and endothelial cells were seeded onto porous tubular poly(glycolic acid) nonwoven scaffolds and cultured in the bioreactor under pulsatile flow conditions for up to 25 days. Cell proliferation was more than 3-fold after 4 days, smooth muscle cells expressed differentiated phenotype after 16 days, and collagen and elastin were distributed throughout the construct after 25 days of culture. In bioreactor experiments in which the construct lumen was seeded with endothelial cells by perfusion after 13 days of smooth muscle cell culture, endothelial cell seeding efficiency was 100%, and a confluent monolayer was observed in the lumen within 48 h. These data demonstrate that this perfusion bioreactor supports sequential seeding of constructs with smooth muscle and endothelial cells. Dynamic culture under pulsatile flow leads to cellular expression of differentiated function and extracellular matrix deposition toward the development of tissue-engineered arterial constructs.

Animals↗

PubMed2003

Extracardiac total cavopulmonary connection using a tissue-engineered graft.

OBJECTIVE: Extracardiac and lateral tunnel total cavopulmonary connection are currently 2 major options for patients with a single ventricle physiology. However, each procedure has some disadvantages over the other. We developed a new technique of extracardiac total cavopulmonary connection using a tissue-engineered graft to overcome some of the disadvantages previously associated with both the extracardiac and lateral tunnel procedures. METHODS: Between February 2001 and October 2002, 8 patients underwent an extracardiac total cavopulmonary connection using a tissue-engineered graft in our institution. Collected bone marrow cells (1 x 10(8) mononucleocytes) from a patient (approximately 1-4 mL/kg body weight) were seeded onto a biodegradable scaffold composed of polycaprolactone-polylactic acid copolymer reinforced with woven polylactic acid. After a 2- to 4-hour cultivation, the seeded scaffold was implanted as an extracardiac conduit during the total cavopulmonary connection operation. RESULTS: There were no hospital or late deaths. At a mean follow-up of 13.4 months (range 4-25 months), all patients are alive and asymptomatic with no need for repeat surgery. A postoperative catheter examination or computed tomography showed all tissue-engineered grafts to be patent and revealed no stenosis, obstruction, or aneurysmal change in the 8 patients. CONCLUSION: We believe that extracardiac total cavopulmonary connection using a tissue-engineered graft has the potential to overcome some of the disadvantages previously associated with extracardiac or lateral tunnel total cavopulmonary connection. However, an extended follow-up period is required to clarify the long-term clinical outcome for the tissue-engineered graft.

Adolescent↗

PubMed2003

Design, synthesis and properties of polyurethane hydrogels for tissue engineering.

Due to their similarity to natural soft tissues, water-swellable polymeric materials (hydrogels) are, in principle, ideal candidates for scaffolds/matrices in tissue engineering. Polyurethanes (PU), hydrophilic but water-insoluble, can be obtained by the incorporation of hydrophilic soft segments, e.g. poly(ethylene oxide) (PEO). These materials possess the favorable characteristics of the family of PUs as well as the ability to mimic soft tissues. In this work, new crosslinked PU-hydrogels were prepared in a one-step bulk polymerization process using an aliphatic diisocyanate, PEO, a low molecular weight diol, and a tri-functional crosslinking agent. A porous structure was also obtained by air-incorporation under mechanical stirring at a controlled high speed during the polymerization. Structural characteristics of the compact (PU-HyC) and the porous (PU-HyP) material were investigated. Molecular weight between cross-links, M(c), and crosslinking density, rho(x), were typical of a low crosslinking degree. A homogeneous distribution of non-interconnecting pores (phi100 microm) was observed in PU-HyP. Both materials showed a high water adsorption. The swelling behavior and weight loss in water was affected by porosity. For their mechanical behavior in the swollen state, the novel PU hydrogels can be considered for biomedical applications where good mechanical properties are required (i.e. 3D scaffold for tissue engineering).

Journal Article↗

PubMed2004

Regulatory and microbiological safety issues surrounding cell and tissue-engineering products.

Cell therapies and tissue-engineered products that contain living cells are potentially some of the most exciting of the novel therapeutic products currently under development. These products, however, present a number of important safety issues, particularly with respect to the transmission of human viruses. In addition, the short shelf life of these products precludes the normally extensive characterization performed on other biotherapeutic products. Careful examination of the risks and extensive testing of the raw materials have been used in place of product testing to ensure safety.

Cell- and Tissue-Based Therapy↗

PubMed2003

Acellularized porcine heart valve scaffolds for heart valve tissue engineering and the risk of cross-species transmission of porcine endogenous retrovirus.

OBJECTIVE: Acellularized porcine heart valve scaffolds have been successfully used for heart valve tissue engineering, creating living functioning heart valve tissue. However, there is concern about the possibility of porcine endogenous retrovirus transmission. In this study we investigated whether acellularized porcine heart valve scaffold causes cross-species transmission of porcine endogenous retrovirus in a sheep model. METHODS: Acellularized porcine pulmonary valve conduits (n = 3) and in vitro autologous repopulated porcine pulmonary valve conduits (n = 5) were implanted into sheep in the pulmonary valve position. Surgery was carried out with cardiopulmonary bypass support. The animals were killed 6 months after the operation. Blood samples were collected regularly up to 6 months after the operation and tested for porcine endogenous retrovirus by means of polymerase chain reaction and reverse transcriptase-polymerase chain reaction. In addition, explanted tissue-engineered heart valves were tested for porcine endogenous retrovirus after 6 month in vivo. RESULTS: Porcine endogenous retrovirus DNA was detectable in acellularized porcine heart valve tissue. However, 6 months after implantation of in vitro and in vivo repopulated acellularized porcine heart valve scaffolds, no porcine endogenous retrovirus sequences were detectable in heart valve tissue and peripheral blood. CONCLUSION: Acellularized porcine matrix scaffolds used for creation of tissue-engineered heart valves do not transmit porcine endogenous retrovirus.

Animals↗

PubMed2005

[Surgery on articular cartilage: from debridement to tissue engineering].

Articular cartilage is a complex tissue with a limited endogenous repair capacity. Surgical strategies to stimulate repair of damaged cartilage are presently evolving extensively. New techniques based on tissue-engineering principles with cultured cells and scaffolds are challenging established techniques based on generating a repair response from the bone marrow. This paper reviews treatments such as debridement, marrow-stimulating techniques, osteochondral transplantation and autologous chondrocyte transplantation. Debridement and marrow stimulation can provide significant relief of symptoms. Recently, randomized studies have uncovered some of the clinical effects of the new biotechnology-based surgical methods. However, no significant advances over the established surgical techniques have been developed.

Cartilage, Articular↗

PubMed2003

Is tissue-engineered heart valve replacement clinically applicable?

Tissue engineering of a heart valve has progressed dramatically in three different arenas: a biodegradable stented valve seeded with autogenous cells, decellularized allograft and xenograft valves that are seeded with autogenous cells, and decellularized allograft and xenograft valves that repopulate by adaptive remodeling in vivo. Preclinical evaluation and implants in sheep have been accomplished in each of these arenas, and clinical use of this emerging technology is occurring in the latter two. The clinical use of decellularized allografts that repopulate in vivo is expanding; however, its impact on allograft durability remains unknown.

Aortic Valve↗

PubMed2003

[The related research of tissue-engineered tendon in vivo].

Using tissue-engineered tendons to repair tendons and ligaments as well as functional reconstruction is the focus of nowadays researches. The scaffolds must be not only unharmful to health, but also easy for cells attachment, and be able to induce collagen deposition to form a neotendon with mechanic properties similar to those of normal tendon. In recent researches, it has been found that the mechanic properties of the implants change with the degrading and femdonizing of scaffolds. The relationships between collagen deposition, scaffolds degradation and mechanic properties of neotendon need to be defined more clearly.

Animals↗

PubMed2004

Effect of sustained gene delivery of platelet-derived growth factor or its antagonist (PDGF-1308) on tissue-engineered cementum.

BACKGROUND: Cementum, a mineralized tissue lining the tooth root surface, is destroyed during the inflammatory process of periodontitis. Restoration of functional cementum is considered a criterion for successful regeneration of periodontal tissues, including formation of periodontal ligament, cementum, and alveolar bone. Short-term administration of platelet-derived growth factor (PDGF) has been shown to partially regenerate periodontal structures. Nonetheless, the role of PDGF in cementogenesis is not well understood. The aim of the present study was to determine the effect of sustained PDGF gene transfer on cementum formation in an ex vivo ectopic biomineralization model. METHODS: Osteocalcin (OC) promoter-driven SV40 transgenic mice were used to obtain immortalized cementoblasts (OCCM). The OCCM cells were transduced with adenoviruses (Ad) encoding either PDGF-A, an antagonist of PDGF signaling (PDGF-1308), a control virus (green fluorescent protein, GFP), or no treatment (NT). The transduced cells were incorporated into polymer scaffolds and implanted subcutaneously into severe combined immunodeficient (SCID) mice. The implants were harvested at 3 and 6 weeks for histomorphometric analysis of the newly formed mineralized tissues. Northern blot analysis was performed to determine the expression levels of mineral-associated genes including bone sialoprotein (BSP), OC, and osteopontin (OPN) in the cell-implant specimens at 3 and 6 weeks. RESULTS: The results indicated mineralization was significantly reduced in both the Ad/PDGF-A and Ad/PDGF-1308 treated specimens when compared to the NT or Ad/GFP groups at 3 and 6 weeks (P<0.01). In addition, the size of the implants treated with Ad/PDGF-A and Ad/PDGF-1308 was significantly reduced compared to implants from Ad/GFP and NT groups at 3 weeks (P<0.05). At 6 weeks, the size of implants and mineral formation increased in NT, Ad/GFP, and Ad/PDGF-A groups, while the Ad/PDGF-1308 treated implants continued to decrease in size and mineral formation (P<0.01). Northern blot analysis revealed that in the Ad/PDGF-A treated implants OPN was increased, whereas OC gene expression was downregulated at 3 weeks. In the Ad/PDGF-1308 treated implants, BSP, OC, and OPN were all downregulated at 3 weeks. At 3 weeks, the Ad/PDGF-A treated implants contained significantly higher multinucleated giant cell (MNGC) density compared to NT, Ad/GFP, and Ad/PDGF-1308 specimens. The MNGC density in NT, Ad/GFP, and Ad/PDGF-A treated groups reduced over time, while the Ad/PDGF-1308 transduced implants continued to exhibit significantly higher MNGC density compared with the other treatment groups at 6 weeks. CONCLUSIONS: The results showed that continuous exposure to PDGF-A had an inhibitory effect on cementogenesis, possibly via the upregulation of OPN and subsequent enhancement of MNGCs at 3 weeks. On the other hand, Ad/PDGF-1308 inhibited mineralization of tissue-engineered cementum possibly due to the observed downregulation of BSP and OC and a persistence of stimulation of MNGCs. These findings suggest that continuous exogenous delivery of PDGF-A may delay mineral formation induced by cementoblasts, while PDGF is clearly required for mineral neogenesis.

Animals↗

PubMed2005

Electrospinning of nano/micro scale poly(L-lactic acid) aligned fibers and their potential in neural tissue engineering.

Efficacy of aligned poly(l-lactic acid) (PLLA) nano/micro fibrous scaffolds for neural tissue engineering is described and their performance with random PLLA scaffolds is compared as well in this study. Perfectly aligned PLLA fibrous scaffolds were fabricated by an electrospinning technique under optimum condition and the diameter of the electrospun fibers can easily be tailored by adjusting the concentration of polymer solution. As the structure of PLLA scaffold was intended for neural tissue engineering, its suitability was evaluated in vitro using neural stem cells (NSCs) as a model cell line. Cell morphology, differentiation and neurite outgrowth were studied by various microscopic techniques. The results show that the direction of NSC elongation and its neurite outgrowth is parallel to the direction of PLLA fibers for aligned scaffolds. No significant changes were observed on the cell orientation with respect to the fiber diameters. However, the rate of NSC differentiation was higher for PLLA nanofibers than that of micro fibers and it was independent of the fiber alignment. Based on the experimental results, the aligned nanofibrous PLLA scaffold could be used as a potential cell carrier in neural tissue engineering.

Animals↗

PubMed2003

Tissue engineering therapy for cardiovascular disease.

The present treatments for the loss or failure of cardiovascular function include organ transplantation, surgical reconstruction, mechanical or synthetic devices, or the administration of metabolic products. Although routinely used, these treatments are not without constraints and complications. The emerging and interdisciplinary field of tissue engineering has evolved to provide solutions to tissue creation and repair. Tissue engineering applies the principles of engineering, material science, and biology toward the development of biological substitutes that restore, maintain, or improve tissue function. Progress has been made in engineering the various components of the cardiovascular system, including blood vessels, heart valves, and cardiac muscle. Many pivotal studies have been performed in recent years that may support the move toward the widespread application of tissue-engineered therapy for cardiovascular diseases. The studies discussed include endothelial cell seeding of vascular grafts, tissue-engineered vascular conduits, generation of heart valve leaflets, cardiomyoplasty, genetic manipulation, and in vitro conditions for optimizing tissue-engineered cardiovascular constructs.

Animals↗

PubMed2006

In vitro evaluation of chitosan/poly(lactic acid-glycolic acid) sintered microsphere scaffolds for bone tissue engineering.

A three-dimensional (3-D) scaffold is one of the major components in many tissue engineering approaches. We developed novel 3-D chitosan/poly(lactic acid-glycolic acid) (PLAGA) composite porous scaffolds by sintering together composite chitosan/PLAGA microspheres for bone tissue engineering applications. Pore sizes, pore volume, and mechanical properties of the scaffolds can be manipulated by controlling fabrication parameters, including sintering temperature and sintering time. The sintered microsphere scaffolds had a total pore volume between 28% and 37% with median pore size in the range 170-200microm. The compressive modulus and compressive strength of the scaffolds are in the range of trabecular bone making them suitable as scaffolds for load-bearing bone tissue engineering. In addition, MC3T3-E1 osteoblast-like cells proliferated well on the composite scaffolds as compared to PLAGA scaffolds. It was also shown that the presence of chitosan on microsphere surfaces increased the alkaline phosphatase activity of the cells cultured on the composite scaffolds and up-regulated gene expression of alkaline phosphatase, osteopontin, and bone sialoprotein.

3T3 Cells↗

PubMedDate not supplied

Current issues in the regulation of human tissue-engineering products in the European Union.

Tissue engineering (TE) is an emerging technology that combines expertise in life sciences, clinical medicine, and engineering. Current challenges in TE include anticipating and streamlining appropriate regulation with product development. Consequently this study has focused on views of developers, companies, and regulators on biological risks of TE products, aspects of commercial applications, and patentability. Most concerns about TE products focus on risk of cancer formation, infection risk, and rejection risk. Thus, at the present time, product developers should follow guidelines for medicinal products, in order to address product safety at an adequate level. According to the data of the present study, cell and biomaterial products, manipulated cells, and scaffolds appear to be the primary interest for commercial product development. In contrast, producing services were not considered as interesting. Constraints are also imposed by patentability, which stipulates demands for technical performance and highlights ethical issues, which are difficult to address.

Biocompatible Materials↗

PubMed2006

Cell-based tissue engineering for lung regeneration.

Emphysema is a chronic lung disease characterized by alveolar enlargement and tissue loss. Tissue engineering represents an attractive potential for regeneration of several organ systems. The complex three-dimensional architectural structure of lung parenchyma requiring connections of alveolar units to airways and the pulmonary circulation makes this strategy less optimistic. In the present study, we used Gelfoam sponge as a scaffold material, supplemented with fetal rat lung cells as progenitors, to explore the potential application of cell-based tissue engineering for lung regeneration in adult rats. After injection into lung parenchyma, the sponge showed porous structures similar to alveolar units. It did not induce severe local inflammatory response. Fetal lung cells in the sponge were able to survive in the adult lung for at least 35 days, determined by CMTMR [5-(and-6)-{[(4-chloromethyl)benzoyl]amino}tetramethylrhodamine] labeling. Proliferation of cells within the sponge was demonstrated in vivo by bromodeoxyuridine (BrdU) labeling. Cells formed "alveolar-like structures" at the border between the sponge and the surrounding lung tissue with positive immunohistochemical staining for epithelial and endothelial cells. Neovascularization of the sponge was demonstrated with India ink perfusion. The sponge degraded after several months. This study suggests that cell-based tissue engineering possesses the potential to regenerate alveolar-like structures, an important step towards our ultimate goal of lung regeneration.

Absorbable Implants↗

PubMed2005

[Fabrication and properties of a composite chitosan/type II collagen scaffold for tissue engineering cartilage].

OBJECTIVE: To develop a novel porous three-dimensional scaffold and to investigate its physico-chemical properties for tissue engineering cartilage. METHODS: Refined 88% deacetylation degree chitosan was prepared and dissolved in 0.2 mol/L acetate acid and fully mixed with highly purified porcine type II collagen in 0.5 mol/L acetate acid solution in a ratio of 4 to 1 (wt/wt). Freeze-drying process was employed to fabricate the composite scaffold. The construct was cross-linked by use of 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). A mechanical tester was utilized to determine the tensile strength change before and after cross-linking. The microstructure was observed via scanning electron microscopy (SEM). The lysozyme degradation was performed to evaluate the degradability of the scaffold in vitro. RESULTS: A bulk scaffold with desired configuration was obtained. The mechanical test showed that the cross-linking treatment could enhance the mechanical strength of the scaffold. The SEM results revealed that the two constituents evenly distributed in the scaffold and that the matrix was porous, sponge-like with interconnected pore sizing 100-250 microm. In vitro lysozyme degradation indicated that cross-linked or uncross-linked composite scaffolds had faster degradation rate than the chitosan matrix. CONCLUSION: Chitosan and type II collagen can be developed into a porous three-dimensional scaffold. The related physico-chemical tests suggest that the composite scaffold meets requirements for tissue engineered scaffold and may serve as an alternative cell-carrier for tissue engineering cartilage.

Cartilage↗

PubMed2006

The role of gene therapy for craniofacial and dental tissue engineering.

Basic science advances in bone tissue engineering using osteoinductive protein therapy have already been translated to the use in patients with selected orthopedic problems. The story of the development of bone morphogenetic protein (BMP) osteoinductive therapy, from the discovery of this class of molecules in 1965 to the publication of randomized clinical trials in 2001 for tibial non-unions and 2002 for spinal fusion, is truly fascinating. Both clinical studies showed healing equivalence of the BMP-bioimplant compared to a free non-vascularized bone graft but without the associated donor site morbidity. These advances unfortunately have not lead to rapid application of using BMP osteoinductive protein therapy for reconstructing most craniofacial bone defects, with clinical case series beginning to be reported only for limited small-sized defects. This is a reflection of the complexity and unique characteristics of most craniofacial defects, which will likely require a more robust osteoinductive signal than delivering recombinant protein on a scaffold for clinically meaningful bone regeneration. Gene therapy approaches are promising for overcoming the unique challenges that are characteristic of craniofacial and dental defects.

Animals↗