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At least 793 records · Page 44Linked to original sources
PubMed2003

Tissue-engineered urinary bladder wall using PLGA mesh-collagen hybrid scaffolds: a comparison study of collagen sponge and gel as a scaffold.

PURPOSE: Tissue engineering of the urinary bladder using autologous cells and biodegradable scaffold is a promising method for augmentation. The authors developed 2 hybrid scaffolds by combining poly (DL-lactic-co-glycolic acid; PLGA) mesh for mechanical strength with collagen sponge or gel suitable for cell seeding. The aim of this study was to compare collagen as a scaffold between collagen sponge and gel and to construct a tissue-engineered urinary bladder wall utilizing these hybrid scaffolds. METHODS: The PLGA mesh-collagen hybrid scaffolds were prepared by introducing collagen sponge or gel into the PLGA knitted mesh. Urothelial and smooth muscle cells were obtained from porcine urinary bladder wall and were cultured in their respective media. The cells were seeded on these hybrid scaffolds. These constructs were analyzed morphologically and immunohistochemically. RESULTS: The urothelial layer was generated 3 dimensionally by culturing urothelial cells with PLGA mesh and collagen sponge. The smooth muscle layer was constructed by culturing smooth muscle cells with PLGA mesh and collagen gel. And a novel tissue-engineered urinary bladder wall was constructed laminating the urothelial and smooth muscle layers. CONCLUSIONS: Ex vivo construction of urinary bladder wall using hybrid scaffolds prepared by combining PLGA mesh with collagen sponge or gel was successful. This tissue-engineered urinary bladder wall allows easy handling and may become a promising tool for bladder augmentation.

Absorbable Implants↗
PubMed2006

Extracellular matrix dynamics associated with tissue-engineered intravascular sclerotherapy.

BACKGROUND: The extracellular dynamics after intravascular sclerotherapy with an injectable, fibroblast-based engineered construct is unknown. METHODS: Rabbits underwent ethanol sclerotherapy of a jugular vein segment. Control animals (n = 40) underwent no further treatment or an acellular collagen hydrogel was injected. Experimental animals (n = 20) received a tissue-engineered construct. After 1, 2, 4, and 20 to 24 weeks, segments were evaluated for collagen, glycosaminoglycan (GAG), matrix metalloproteinase (MMP) 2 and 9, and tissue inhibitors of MMP (TIMPs) 1 and 2 and scored on a scale of 0 to 3. Groups and time points were compared using nonparametric statistical analysis. RESULTS: Collagen content was higher in animals that received fibroblasts (P < .05). Glycosaminoglycan analysis showed a higher grade only at 1 week (P < .05). Collagen and GAG deposition were prominent at weeks 1 through 4, and decreased over time. Both MMP-2 and MMP-9 and TIMP-1 and TIMP-2 grade decreased with time (P < .01) in all groups, with no differences between groups. CONCLUSION: Enhancement of intravascular sclerotherapy by tissue engineering stems, at least in part, from increased local deposition of collagen and GAG. MMP and TIMPs may play a role in recanalization after experimental sclerotherapy. Tissue engineering may be a valuable adjunct for the treatment of vascular malformations.

Animals↗
PubMed2005

In vitro tissue engineering of a cardiac graft using a degradable scaffold with an extracellular matrix-like topography.

OBJECTIVE: Cardiac tissue engineering has been proposed as a treatment to repair impaired hearts. Bioengineered cardiac grafts are created by combining autologous cell transplantation with a degradable scaffold as a temporary extracellular matrix. Here we present a system for engineered myocardium combining cultured cardiomyocytes and a novel biodegradable scaffold with a unique extracellular matrix-like topography. METHODS: Cardiomyocytes were harvested from neonatal rats and cultured in vitro on biodegradable electrospun nanofibrous poly(epsilon-caprolactone) meshes. Between days 5 and 7, the meshes were overlaid to construct 3-dimensional cardiac grafts. On day 14 of in vitro culture, the engineered cardiac grafts were analyzed by means of histology, immunohistochemistry, and scanning electron microscopy. RESULTS: The cultured cardiomyocytes attached well to the meshes, and strong beating was observed throughout the experimental period. The average fiber diameter of the scaffold is about 250 nm, well below the size of an individual cardiomyocyte. Hence the number of cell-cell contacts is maximized. Constructs with up to 5 layers could be formed without any incidence of core ischemia. The individual layers adhered intimately. Morphologic and electrical communication between the layers was established, as verified by means of histology and immunohistochemistry. Synchronized beating was also observed. CONCLUSIONS: This report demonstrates the formation of thick cardiac grafts in vitro and the versatility of biodegradable electrospun meshes for cardiac tissue engineering. It is envisioned that cardiac grafts with clinically relevant dimensions can be created by using this approach and combining it with new technologies to induce vascularization.

Animals↗
PubMed2005

Genetically engineered cells with regulatable GABA production can affect afterdischarges and behavioral seizures after transplantation into the dentate gyrus.

Intractable seizures originating in the mesial temporal lobe can often be controlled by resection. An alternative to removing hippocampal tissue may be transplantation of GABA-producing cells. Neural cell transplantation has been performed in hundreds of patients, including some with temporal lobe epilepsy. This study evaluates the seizure-suppressing capabilities of engineered GABA-producing cells transplanted into the dentate gyrus. Immortalized neurons were engineered to produce GABA under the control of doxycycline. The cells were characterized for GABA production in vitro and for their ability to raise GABA concentrations in vivo. Cells were transplanted bilaterally into the dentate gyrus of rats and tested in two separate paradigms. Afterdischarge thresholds and durations were tested with granule cell stimulation, and the development of behavioral seizures, induced by daily electrical stimulation of the major excitatory input pathway into the dentate gyrus, was assessed in the presence, or the absence, of doxycycline. GABA production was under the tight control of doxycycline. Cells engineered to produce GABA raised tissue GABA concentrations in the hippocampus compared with non GABA-producing cells, and this was abolished when doxycycline was administered. GABA-producing cells raised the threshold, and shortened the duration of hippocampal afterdischarges elicited by granule cell stimulation. Lastly, the appearance of stage 5 seizures was slowed in the kindling paradigm, compared with a group that received non-GABA-producing cells, and compared with a group that received GABA-producing cells but was administered doxycycline. This study shows that targeted hippocampal implants of genetically engineered cells have the potential to raise GABA levels and to affect seizure development. The ability to suppress the production of GABA, and to modulate the physiological effects of the transplanted cells provides an important level of experimental control. These techniques, combined with stem cell technology, may advance cell-based therapies for epilepsy and other diseases of the CNS.

Amino Acids↗
PubMed2026

Next-generation macrophage engineering in cancer therapy: From TAM reprogramming to CAR-macrophages.

Macrophages are central regulators of the tumor microenvironment (TME), shaping immune suppression, angiogenesis, metabolism, and therapeutic resistance in solid cancers. While early strategies sought to deplete tumor-associated macrophages (TAMs) or block monocyte recruitment, limited efficacy and compensatory mechanisms revealed the need for functional reprogramming rather than elimination. Recent advances in viral vectors, CRISPR-Cas genome editing, and RNA-based delivery platforms have enabled precise genetic modification of macrophages, giving rise to chimeric antigen receptor macrophages (CAR-Ms) and related engineered products. Beyond antigen targeting, effective macrophage engineering requires stabilization of pro-inflammatory identity, resistance to tumor-induced repolarization, metabolic reinforcement, and integration of checkpoint modulation pathways. This review synthesizes current strategies across DNA, mRNA, and siRNA-based platforms, highlighting convergent design principles that connect TAM reprogramming with CAR-M development. We discuss reshaping phagocytosis checkpoints, metabolic and transcriptional stabilization, cytokine augmentation, and synthetic receptor architecture, emphasizing combinatorial and context-aware engineering, while proposing new candidate gene targets. Engineered macrophages are thus evolving from simple effector cells into programmable immune coordinators capable of converting immunologically "cold" tumors into inflamed, therapy-responsive niches.

CAR-M↗
PubMed2005

Cell-based therapies and tissue engineering.

Tissue engineering is a rapidly evolving discipline that may some-day afford surgeons a limitless supply of autologous tissue for transplantation or allow in situ tissue regeneration. A number of biologic, engineering, and clinical challenges continue to face tissue engineers and surgeons alike. One important example is the choice of an appropriate cell scaffold that promotes growth and is eventually resorbed by the body. Although the application of bioengineered tissue is specific to the anatomic areas of interest,continued advances bring tissue engineering closer to reality in all areas of otolaryngology.

Biocompatible Materials↗
PubMed2005

Controlling cell biomechanics in orthopaedic tissue engineering and repair.

Tissue engineering offers an alternative approach with great potential for the treatment or replacement of damaged tissues or organs. In contrast to current treatments, a small sample of cells can be collected from the patient and cultured in vitro, greatly increasing the number of cells available for engineering tissue implants. As a result, engineered tissue implants limit the problems associated with patient trauma and undesirable immune response currently observed in surgical treatments practised in tissue and organ replacement. Mechano-transduction is known to play an essential role in bone tissue remodelling and repair. At physiological magnitudes, the effects of secondary messenger pathways, their components and local mediators generated as a direct result of mechanical load are known to result in an elevation of specific matrix protein mRNAs. Up-regulation of matrix protein production is paramount to tissue formation. Thus, mechano-transduction offers a method of producing bone tissue in vitro. However, successful transduction of mechanical stimuli from a substrate to cells is reliant upon a number of factors including cell-substrate adhesion, scaffold material mechanics and the activation of membrane channels, for example voltage-operated calcium channels (VOCC). Our research focuses on the optimisation of mechano-transduction pathways for successful bone tissue engineering. In this paper, we focus on the effects of cell-substrate adhesion, attenuation of VOCC activation states and biological conditioning of cell-scaffold constructs utilising bioreactors in relation to mechano-transduction-induced bone tissue production. The effects of these factors on successful bone tissue formation observed in increased matrix protein synthesis due to the optimisation of mechano-transduction pathways is discussed.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2004

The role of bioreactors in tissue engineering.

Ex vivo engineering of living tissues is a rapidly developing area with the potential to impact significantly on a wide-range of biomedical applications. Major obstacles to the generation of functional tissues and their widespread clinical use are related to a limited understanding of the regulatory role of specific physicochemical culture parameters on tissue development, and the high manufacturing costs of the few commercially available engineered tissue products. By enabling reproducible and controlled changes of specific environmental factors, bioreactor systems provide both the technological means to reveal fundamental mechanisms of cell function in a 3D environment, and the potential to improve the quality of engineered tissues. In addition, by automating and standardizing tissue manufacture in controlled closed systems, bioreactors could reduce production costs, thus facilitating a wider use of engineered tissues.

Bioreactors↗
PubMed2004

Scaffold-based tissue engineering: rationale for computer-aided design and solid free-form fabrication systems.

One of the milestones in tissue engineering has been the development of 3D scaffolds that guide cells to form functional tissue. Recently, mouldless manufacturing techniques, known as solid free-form fabrication (SFF), or rapid prototyping, have been successfully used to fabricate complex scaffolds. Similarly, to achieve simultaneous addition of cells during the scaffold fabrication, novel robotic assembly and automated 3D cell encapsulation techniques are being developed. As a result of these technologies, tissue-engineered constructs can be prepared that contain a controlled spatial distribution of cells and growth factors, as well as engineered gradients of scaffold materials with a predicted microstructure. Here, we review the application, advancement and future directions of SFF techniques in the design and creation of scaffolds for use in clinically driven tissue engineering.

Biocompatible Materials↗
PubMed2006

Web-based education in bioprocess engineering.

The combination of web technology, knowledge of bioprocess engineering, and theories on learning and instruction might yield innovative learning material for bioprocess engineering. In this article, an overview of the characteristics of web-based learning material is given, as well as guidelines for the design of learning material from theories of learning and instruction and from the bioprocess engineering domain. A diverse body of learning material is presented, which illustrates the application of these guidelines; this material has been developed during the past six years for different courses, mostly at undergraduate level, and it illustrates how web-based learning material can enable various different approaches to learning objectives that might improve overall learning. Such learning material has been used for several years in education, it has been evaluated with positive results, and is now part of the regular learning material for bioprocess engineering at Wageningen University.

Biomedical Engineering↗
PubMed2004

Heart valve tissue engineering.

Valvular heart disease is a significant cause of morbidity and mortality world-wide. Classical replacement surgery involves the implantation of mechanical valves or biological valves (xeno- or homografts). Tissue engineering of heart valves represents a new experimental concept to improve current modes of therapy in valvular heart surgery. Various approaches have been developed differing either in the choice of scaffold (synthetic biodegradable polymers, decellularised xeno- or homografts) or cell source for the production of living tissue (vascular derived cells, bone marrow cells or progenitor cells from the peripheral blood). The use of autologous bone marrow cells in combination with synthetic biodegradable scaffolds bears advantages over other tissue engineering approaches: it is safe, it leads to complete autologous prostheses and the cells are more easily obtained in the clinical routine. Even though we demonstrated the feasibility to construct living functional tissue engineered heart valves from human bone marrow cells, so far their general potential to differentiate into non-hematopoietic cell lineages is not fully exploited for tissue engineering applications.

Absorbable Implants↗
PubMed2006

Application of stem cells for cardiovascular grafts tissue engineering.

Congenital and acquired heart diseases are leading causes of morbidity and mortality world-wide. Currently, the synthetic materials or bioprosthetic replacement devices for cardiovascular surgery are imperfect and subject patients to one or more ongoing risks including thrombosis, limited durability and need for reoperations due to lack of growth in children and young adults. Suitable replacement grafts should have appropriate characteristics, including resistance to infection, low immunogenicity, good biocompatability and thromboresistance, with appropriate mechanical and physiological properties. Tissue engineering is a new scientific field aiming at fabrication of living, autologous grafts having structure or function properties that can be used to restore, maintain or improve tissue function. The use of autologous stem cells in cardiovascular tissue engineering is quite promising due to their capacity of self-renewal, high proliferation, and differentiation into specialized progeny. Progress has been made in engineering the various components of the cardiovascular system, including myocardial constructs, heart valves, and vascular patches or conduits with autologous stem cells. This paper will review the current achievements in stem cell-based cardiovascular grafts tissue engineering, with an emphasis on its clinical or possible clinical use in cardiovascular surgery.

Animals↗
PubMed2003

Rational design and engineering of delivery systems for therapeutics: biomedical exercises in colloid and surface science.

Engineering delivery systems of therapeutic agents has grown into an independent field, transcending the scope of traditional disciplines and capturing the interest of both academic and industrial research. At the same time, the acceleration in the discovery of new therapeutic moieties (chemical, biological, genetic and radiological) has led to an increasing demand for delivery systems capable of protecting, transporting, and selectively depositing those therapeutic agents to desired sites. The vast majority of delivery systems physically reside in the colloidal domain, while their surface properties and interfacial interactions with the biological milieu critically determine the pharmacological profiles of the delivered therapeutic agents. Interestingly though, the colloidal and surface properties of delivery systems are commonly overlooked in view of the predominant attention placed on the therapeutic effectiveness achieved. Moreover, the development and evaluation of novel delivery systems towards clinical use is often progressed by serendipity rather than a systematic design process, often leading to failure. The present article will attempt to illustrate the colloid and interfacial perspective of a delivery event, as well as exemplify the vast opportunities offered by treating, analysing and manipulating delivery systems as colloidal systems. Exploring and defining the colloid and surface nature of the interactions taking place between the biological moieties in the body and an administered delivery vehicle will allow for the rational engineering of effective delivery systems. A design scheme is also proposed on the way in which the engineering of advanced delivery systems should be practiced towards their transformation from laboratory inventions to clinically viable therapeutics. Lastly, three case studies are presented, demonstrating how rational manipulation of the colloidal and surface properties of delivery systems can lead to newly engineered systems relevant to chemotherapy, gene therapy and radiotherapy.

Biomedical Engineering↗
PubMed2000

Tissue engineering of heart valves: in vitro experiences.

BACKGROUND: Tissue engineering is a new approach, whereby techniques are being developed to transplant autologous cells onto biodegradable scaffolds to ultimately form new functional tissue in vitro and in vivo. Our laboratory has focused on the tissue engineering of heart valves, and we have fabricated a trileaflet heart valve scaffold from a biodegradable polymer, a polyhydroxyalkanoate. In this experiment we evaluated the suitability of this scaffold material as well as in vitro conditioning to create viable tissue for tissue engineering of a trileaflet heart valve. METHODS: We constructed a biodegradable and biocompatible trileaflet heart valve scaffold from a porous polyhydroxyalkanoate (Meatabolix Inc, Cambridge, MA). The scaffold consisted of a cylindrical stent (1 x 15 x 20 mm inner diameter) and leaflets (0.3 mm thick), which were attached to the stent by thermal processing techniques. The porous heart valve scaffold (pore size 100 to 240 microm) was seeded with vascular cells grown and expanded from an ovine carotid artery and placed into a pulsatile flow bioreactor for 1, 4, and 8 days. Analysis of the engineered tissue included biochemical examination, enviromental scanning electron microscopy, and histology. RESULTS: It was possible to create a trileaflet heart valve scaffold from polyhydroxyalkanoate, which opened and closed synchronously in a pulsatile flow bioreactor. The cells grew into the pores and formed a confluent layer after incubation and pulsatile flow exposure. The cells were mostly viable and formed connective tissue between the inside and the outside of the porous heart valve scaffold. Additionally, we demonstrated cell proliferation (DNA assay) and the capacity to generate collagen as measured by hydroxyproline assay and movat-stained glycosaminoglycans under in vitro pulsatile flow conditions. CONCLUSIONS: Polyhydroxyalkanoates can be used to fabricate a porous, biodegradable heart valve scaffold. The cells appear to be viable and extracellular matrix formation was induced after pulsatile flow exposure.

Animals↗
PubMed2003

Comparison of tracheal and nasal chondrocytes for tissue engineering of the trachea.

BACKGROUND: This study was undertaken to evaluate the feasibility of creating engineered tracheal equivalents grown in the shape of cylindrical cartilaginous structures using sheep nasal cartilage-derived chondrocytes. We also tested sheep tracheal and nasal septum for cell yield and quality of the engineered cartilage each produced. METHODS: Nasal septum and tracheal tissue were harvested from sheep. Chondrocytes from each were separately isolated from the tissues and suspended in culture media. Tracheal and nasal chondrocytes were seeded onto separate polyglycolic acid matrices. Cell-polymer constructs were cultured for 1 week and then wrapped around a 7-mm diameter x 30-mm length silicon tube and implanted subcutaneously on the back of nude mice for 8 weeks (each, n = 6). Both of the tissue-engineered tracheas (TET) were harvested and analyzed for histological, biochemical, and biomechanical properties. These values were compared with native sheep trachea. RESULTS: The morphology and histology of both tracheal-chondrocyte TET and nasal-chondrocyte TET closely resembled that of native sheep trachea. Safranin-O staining showed that tissue-engineered cartilage was organized into lobules with round, angular lacunae, each containing a single chondrocyte. Chondrocytes from the trachea or nasal septum produced tissue with similar mechanical properties and had similar glycosaminoglycan and hydroxyproline content. CONCLUSIONS: This study demonstrates that the property of TET using nasal chondrocytes is similar to that obtained using tracheal chondrocytes. This has the potential benefit of facilitating an autologous approach for repair of segmental tracheal defects using an easily obtained chondrocyte population.

Animals↗
PubMed2003

Preproinsulin mRNA engineering and its application to the regulation of insulin secretion from human hepatomas.

Cell-based therapies for treating insulin-dependent diabetes (IDD) can provide a more physiologic regulation of blood glucose levels in a less invasive fashion than daily insulin injections. Promising cells include non-beta cells genetically engineered to secrete insulin in response to physiologic cues; responsiveness can be introduced at the transcriptional level to regulate preproinsulin (PPI) mRNA biosynthesis. However, these cells exhibit sluggish secretion dynamics, which is not appropriate for achieving euglycemia in higher animals and, eventually, humans. In this work, we have engineered the PPI mRNA so as to destabilize it through nonsense-mediated mRNA decay (NMD). When expressed under transcriptional regulation in HepG2 hepatomas, the engineered PPI mRNA level and of the insulin secretion rate declined faster upon switching off transcription, compared to the one-copy non-engineered control. Our work provides a simple and straightforward method to improve the dynamics of transcriptionally regulated insulin secretion, which can be a useful tool in developing cell-based therapies for IDD.

Base Sequence↗
PubMed1998

Prevention of focal intimal hyperplasia in rat vein grafts by using a tissue engineering approach.

The present study focused on the role of blood flow in the formation of focal intimal hyperplasia in vein grafts, as well as the development of an engineering approach that can be used to eliminate disturbed blood flow and prevent blood flow-related focal intimal hyperplasia. A rat vein graft model was constructed by interposing a jugular vein into the abdominal aorta with end-to-end anastomoses. Locally disturbed flow was identified by analyzing particle streak-lines in methyl salicylate-cleared and perfused vein grafts in vitro with a physiological Reynolds number. At day 10, 20, and 30 after surgery, focal intimal hyperplasia of the vein grafts was examined using a histological approach and the density of alpha-actin positive cells was determined using immunohistological and fluorescent approaches. Results showed that apparent eddy blood flow formed at the proximal, but not at the distal, end of the vein grafts due to graft-host diameter mismatch and local geometric distortions, and was associated with apparent focal intimal hyperplasia. The thickness of the alpha-actin positive layers of the proximal vein grafts was significantly higher than that of the distal grafts (192 +/- 27 vs. 94 +/- 18 microm, 278 +/- 55 vs. 124 +/- 20 microm, and 288 +/- 24 vs. 131 +/- 23 microm for day 10, 20. and 30, respectively). The density of the alpha-actin positive cells, however, was similar between the proximal and the distal regions (3569 +/- 361 vs. 3285 +/- 343 cells/mm2, 5540 +/- 650 vs. 5376 + 887 cells/mm2, and 5465 +/- 791 vs. 5278 +/- 524 cells/mm2 for day 10, 20, and 30, respectively). When eddy blood flow was eliminated by matching the graft-host diameters using a tissue engineering approach, the average thickness of the alpha-actin positive layers of the proximal (71 +/- 15, 86 +/- 16, and 85 +/- 14 microm for day 10, 20, and 30, respectively) and the distal vein grafts (68 +/- 13, 80 +/- 14, and 79 +/- 13 microm for day 10, 20, and 30, respectively) was reduced significantly. The density of the alpha-actin positive cells was also reduced significantly in the proximal (2946 +/- 359, 3261 +/- 295, 3472 +/- 599 cells/mm2 for day 10, 20, and 30, respectively) and in the distal regions (3151 +/- 511, 3466 +/- 687, 3593 +/- 688 cells/mm2 for day 10, 20, and 30, respectively). The thickness of the alpha-actin positive layers and the density of the alpha-actin positive cells were not significantly different between the proximal and distal regions of the engineered vein grafts at each observation time. These results suggest that eddy flow may develop in vein grafts and may facilitate the formation of focal intimal hyperplasia, and the vascular tissue engineering approach developed in this study may be used to prevent blood flow-related focal intimal hyperplasia in vein grafts.

Actins↗
PubMed2003

Fetal tracheal augmentation with cartilage engineered from bone marrow-derived mesenchymal progenitor cells.

BACKGROUND/PURPOSE: The authors have described previously the use of engineered fetal cartilage in a large animal model of fetal tracheal repair. This study was aimed at comparing cartilage engineered from bone marrow-derived stromal cells (BMSC) to native and engineered cartilage, in this model. METHODS: Ovine BMSC were expanded in vitro, seeded onto biodegradable scaffolds, and maintained in transforming growth factor beta 1 (TGF-beta1)-supplemented medium for 3 months (group I). Identical scaffolds were seeded with fetal chondrocytes (group II). All constructs were analyzed in vitro, implanted into fetal tracheas, and harvested after birth for further analysis. RESULTS: There were no differences in survival between the groups. All BMSC-based constructs exhibited chondrogenic differentiation. Matrix analyses in vitro showed that both groups had similar levels of glycosaminoglycans (GAG) and type II collagen (C-II), but lower levels of elastin when compared with native fetal cartilage. Yet, compared with group II, group I had higher levels of GAG, equal levels of C-II, and lower levels of elastin. However, remodeling resulted in no differences between the 2 groups in any of these variables in vivo. CONCLUSIONS: The bone marrow may be a useful cell source for cartilage engineering aimed at the surgical repair of severe congenital tracheal anomalies, such as tracheal atresia and agenesis, in utero.

Animals↗