[Tissue engineering in urology. Status in Germany in 2004].
Explore the source record for details and available documents.
Bioartificial Organs↗
SEARCH · Search PubMed
Results for “Bioartificial Organs”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
[Tissue engineering of the urethra and ureter].
Congenital or acquired disorders of the urethra or ureter often require adequate tissue transfer for reconstruction. A variety of biomaterials have proved to be useful in the reconstruction of the urethra or ureter in animal models and meanwhile even clinically. Innovative tissues such as acellular matrices can be placed in the host and function as a scaffold to allow the natural process of tissue regeneration. Biodegradable scaffolds can also be used as cell transplantation vehicles for the reconstruction of urethral or ureteral tissue. One of the limitations of cell-based tissue engineering techniques however is the difficulty of growing genitourinary-associated cells in large quantities in primary cultures. It can be speculated that stem cell research might help to overcome this specific problem in the future.
Absorbable Implants↗
[Tissue engineering of the urinary bladder].
In tissue engineering of the urinary bladder with autologous cell transplantation, high differentiation of the cells cultivated in vitro on biocompatible membranes is essential for the functionality of the tissue constructs after implantation. The terminal differentiation of superficial urothelial cells has a key role because of the barrier function of these cells against urine. The aim of this study was to determine optimized conditions for the creation of terminally differentiated urothelium to cover large membrane surfaces. This can bring us closer to the goal of using functioning tissue constructs in clinical trials.
Absorbable Implants↗
[Biological vascularized matrix (BioVaM): a new method for solving the perfusion problems in tissue engineering].
A new technique is presented to harvest an acellular matrix from a porcine small bowel segment preserving the mesenteric arterial and venous pedicles. Reseeding of this biological vascularized matrix (BioVaM) with functional cells, i.e. smooth muscle and urothelial cells isolated from the urinary tract, and resurfacing of its vascular structures with endothelial precursor cells results in a vascularized tissue engineered graft for reconstruction and augmentation of the urinary bladder. First promising short term implantation experiments using a porcine model for the evaluation of early graft perfusion after vascular anastomosis are presented.
Animals↗
Tissue-engineered artificial urothelium.
Bladder wall replacement is one of the most challenging problems of urologic surgery. Various materials have been tried in experimental models, but most were not free of complications, such as leakage, infection, and stone formation. In addition, much time was needed for tissue regeneration after grafting. Bladder replacement with tissue-engineered materials, which basically consist of autologous cells seeded on a supporting structure, represents an area of rapidly expanding interest. Recently, several investigators have reported important, successful results from in vitro systems and animal models. Here we review those experimental approaches to tissue-engineered artificial urothelium.
Animals↗
Effects of 3-isobutyl-1-methylxanthine and kojic acid on cocultures and skin equivalents composed of HaCaT cells and human melanocytes.
Explore the source record for details and available documents.
1-Methyl-3-isobutylxanthine↗
Experimental study of an artificial esophagus using a collagen sponge, a latissimus dorsi muscle flap, and split-thickness skin.
The time and effort spent trying to devise an artificial esophagus have not yet resulted in success, and leakage and strictures at the anastomotic sites remain the most frequent complications. We developed an artificial esophagus with a bilayered structure made of porous collagen sponge (artificial dermis; AD), a latissimus dorsi muscle flap (LD), and split-thickness skin (STS). We investigated whether the use of AD prevented the contraction of grafted skin and its effects on the extensibility of the neoesophagus in rabbits. We experimented with two groups. In the AD group, AD was applied to the surface of the LD. Three weeks later, the STS was grafted. In the control group, the STS was grafted directly onto the LD. The sizes of the STS in both groups 3 weeks after the graft were, respectively, 56.6% +/- 4.1% and 39.0% +/- 10.2% of the initial surface area of the STS (P < 0.01). The roll made in the AD group had better extensibility than that in the control group. We replaced the cervical esophagus in 12 rabbits with the neoesophagus made from AD, STS, and LD. The longest survival period was 16 days. Esophagography did not reveal either anastomotic leakage or stenosis in any of the five rabbits in the experiments. These findings suggested that AD can thus be used to create a more suitable hybrid artificial esophagus.
Animals↗
Biomechanics and repair of articular cartilage.
The most important function of the joints relies on excellent lubrication and the uniform distribution of impact loads onto the underlying bones, together with damping effects. In most joint disorders, as the lesion is limited to the joint surface, it becomes necessary to repair the joint surface. In this article, repair with an artificial composite osteochondral device (COD) is reported, as is biological resurfacing with cultured chondrocytes. The COD consists of polyvinyl alcohol (PVA) hydrogel as artificial cartilage and titanium fiber mesh (TFM) as porous artificial bone. PVA solution was impregnated into the pores of TFM by injection molding, and these two materials were bound together by a gelling process to create the COD. The key problem, i.e., to attain quick and firm attachment to the underlying bone, was addressed by creating this COD, in which the TFM interface allows not only firm attachment of the PVA gel but also strong attachment to the joint surface through bony ingrowth. For the purpose of simulating partial hemiarthroplasty for the femoral head, 30 COD prostheses were implanted into canine femoral heads. Histological findings of the acetabular cartilage and synovial membrane, as well as findings of attachment of the prosthesis to bone, were examined for an 18-month period after the operation. No particular pathological changes in acetabular cartilage were found, and firm attachment of the devices to bone was confirmed. These results indicate that the COD could be a very promising joint repair material.
Animals↗
Modeling cell and matrix anisotropy in fibroblast populated collagen vessels.
Microstructurally based models for bio-artificial tissues are needed to predict in vivo mechanical behavior and to validate assumptions for models of biologic tissues. We develop a microstructural model, based on on Zahalak et al. (2000) [Biophys 79(5):2369-2381], to describe matrix and tissue anisotropy observed in recent biaxial tests of fibroblast populated collagen vessels (FPCVs) with different cell orientations (Wagenseil et al. in Ann Biomed Eng 32(5):720-731 2004). The model includes pseudo-elastic cell behavior and pseudo-elastic, non-linear matrix behavior with recruitment of initially buckled collagen fibers. We obtained estimates of collagen matrix parameters from measurements of FPCVs treated with 2x 10(-6) M Cytochalasin D and used these estimates to determine cell parameters in FPCVs activated with 5% fetal calf serum. The estimated stiffness of individual fibroblasts was 41-1,165 kPa. Parameter estimates for both cell and matrix were influenced by the non-linearity of the biaxial test data, making it difficult to obtain unique parameter values for some experiments. Additional microstructural measurements of the collagen matrix may help to more precisely determine the relative contributions of cells and matrix.
Animals↗
Mechanical interlocking of engineered cartilage to an underlying polymeric substrate: towards a biohybrid tissue equivalent.
This study investigates the feasibility of engineering a biohybrid cartilage equivalent (BCE) with the long-term goal of restoring the mechanical integrity and interfacial characteristics of severely damaged cartilage. The BCE depends on the successful adhesion, via mechanical interlocking, of a cartilage layer to a nondegradable composite scaffold or prosthesis. The model scaffold, consisting of a nonwoven mesh bonded to a solid core, was seeded with bovine articular chondrocytes. High molecular weight poly(L-lactic acid), which has a slow degradation time, was used to model the nondegradable polymer. Biochemical and histological analysis demonstrate that the BCE can support the growth of a cartilaginous matrix for at least 6 weeks in culture. Mechanical testing of the BCE showed cartilage adhesion strength increased from 19.27+/-1.62 to 43.79+/-3.88 kPa between 35 and 50 days in culture. Nonmechanically interlocked cartilage achieved less than 5% of this adhesion strength. For the first time, atomic force microscopy (AFM) was used to characterize surface topography of tissue-engineered cartilage. Surface roughness of constructs after 8 and 10 weeks ranged from 153 to 171 nm, falling within the range of native cartilage (100-600 nm). This study demonstrates the feasibility of creating a biohybrid cartilage equivalent by mechanically interlocking a cartilaginous layer to an underlying polymeric matrix.
Animals↗
Cellular and matrix mechanics of bioartificial tissues during continuous cyclic stretch.
Bioartificial tissues are useful model systems for studying cell and extra-cellular matrix mechanics. These tissues provide a 3D environment for cells and allow tissue components to be easily modified and quantified. In this study, we fabricated bioartificial tissue rings from a 1 ml solution containing one million cardiac fibroblasts and 1 mg collagen. After 8 days, rings compacted to <1% of original volume and cell number increased 2.4 fold. We initiated continuous cyclic stretching of the rings after 2, 4, or 8 days of incubation, while monitoring the tissue forces. Peak tissue force during each cycle decreased rapidly after initiating stretch, followed by further slow decline. We added 2 microM Cytochalasin-D to some rings prior to initiation of stretch to determine the force contributed by the matrix. Cell force was estimated by subtracting matrix force from tissue force. After 12 h, matrix force-strain curves were highly nonlinear. Cell force-strain curves were linear during loading and showed hysteresis indicating viscoelastic behavior. Cell stiffness increased with stretching frequency from 0.001-0.25 Hz. Cell stiffness decreased with stretch amplitude (5-25%) at 0.1 Hz. The trends in cell stiffness do not fit simple viscoelastic models previously proposed, and suggest possible strain-amplitude related changes during cyclic stretch.
Animals↗
Supplementation with a complex of active nutrients improved dermal and epidermal characteristics in skin equivalents generated from fibroblasts from young or aged donors.
Cultured skin equivalent (SE, Mimeskin) was generated by co-culturing skin fibroblasts and keratinocytes on a collagen-glycosaminoglycan-chitosan dermal substrate. In order to examine donor age effect, fibroblasts from 19- (young) or 49- (aged) year-old females were used. Culture medium was supplemented with nutrients complex containing soy extract, tomato extract, grape seed extract, white tea extract, sodium ascorbate, tocopherol acetate, zinc gluconate and BioMarine complex. Epidermal and dermal structure and composition were examined after 42 and 60 days of culture. In untreated samples, SE generated from young fibroblasts was superior to SE from aged fibroblasts in all characteristics. Those include number and regularity of keratinocyte layers, number of keratinocytes expressing proliferation marker Ki67, content of collagen type I, fibrillin-1, elastin, and SE lifespan. Effects of nutritional supplementation were observed in SE from both young and aged fibroblasts, however, those effects were more pronounced in SE from aged fibroblasts. In epidermis, the treatment increased number of keratinocyte layers and delayed epidermal senescence. The number of cells expressing Ki67 was nine folds higher than those of controls, and was similar to that of young cell SE. In dermis, the treatment increased mRNA synthesis of collagen I, fibrillin-1 and elastin. In conclusion, skin cell donor age had major important effect on formation of reconstructed SE. Imperfections in epidermal and dermal structure and composition as well as life span in SE from aged cells can be improved by supplementation with active nutrients.
Adult↗
Enhancing cell viability with pulsating flow in a hollow fiber bioartificial liver.
A pulsating flow of medium was used to alleviate diffusion and transport limitations in a hollow fiber bioreactor containing a human hepatoblastoma cell line. The strategy is easy to implement but effective. The pulsating flow is introduced by a solenoid pinch valve at the outlet of the bioreactor and regulated by a timing circuit. In a permeability test, the system with pulsating flow had much less membrane fouling as compared to the control, a conventional hollow fiber unit. In hepatocyte culture test runs, the pulsating-flow bioreactor demonstrated the ability to maintain a higher cell viability. Histological sections indicated significantly smaller necrotic regions in the pulsating-flow bioreactor as compared to the conventional unit.
Bioartificial Organs↗
The effect of alginate, hyaluronate and hyaluronate derivatives biomaterials on synthesis of non-articular chondrocyte extracellular matrix.
Cartilage engineering consists of re-constructing functional cartilage by seeding chondrocytes in suitable biomaterials in vitro. The characteristics of neocartilage differ upon the type of biomaterial chosen. This study aims at determining the appropriate scaffold material for articular cartilage reconstruction using non articular chondrocytes harvested from rat sternum. For this purpose, the use of polysaccharide hydrogels such as alginate (AA) and hyaluronic acid (HA) was investigated. Several ratios of AA/HA were used as well as three derivatives obtained by chemical modification of HA (HA-C18, HA-C12(2.3), HA-C12(2.5)-TEG0.5). Sternal chondrocytes were successfully cultured in 3D alginate and alginate/HA scaffolds. HA retention in alginate beads was found to be higher in beads seeded with cells than in beads without cells. HA-C18 improved HA retention in beads but inhibited the chondrocyte synthesis process. Cell proliferation and metabolism were enhanced in all biomaterials when beads were mechanically agitated. Preliminary results have shown that the chondrocyte neo-synthesised matrix had acquired articular characteristics after 21 days culture.
Alginates↗
Fibrillar collagen assembled in the presence of glycosaminoglycans to constitute bioartificial stem cell niches in vitro.
Fibrillar collagen was reconstituted from mixtures of monomeric tropocollagen and heparin or hyaluronic acid, respectively. Turbidity measurements were utilized to follow the fibrillar assembly and demonstrated the influence of the concentration of the glycosaminoglycan on the maximum optical densities. Thin film coatings of maleic anhydride copolymers were utilized for the covalent immobilization of the fibrillar assemblies to solid supports. Quantification of surface-bound collagen was accomplished by ellipsometry and HPLC-based amino acid analysis indicating that less collagen was immobilized in the presence of the glycosaminoglycans. SEM and AFM revealed various sizes and shapes of the immobilized fibrillar assemblies if collagen fibrils were prepared in the presence of heparin or hyaluronic acid. Human hematopoietic stem cells (HSCs) were cultivated on the surface-bound collagen fibrils and the migration of adherent cells was studied by time-lapse microscopy. Migration rates on fibrillar structures were significantly lower then on tropocollagen indicating a more intimate contact of HSCs to the fibrillar substrates.
Bioartificial Organs↗
Search for ideal biomaterials to cultivate human osteoblast-like cells for reconstructive surgery.
In this study we cultured human osteoblast-like cells on 16 different biomaterials to find an optimal biomaterial for subsequent use in reconstructive surgery. The tested biomaterials can be divided into five groups: collagen-based membranes of bovine, equine or calf origin, tricalcium phosphate based membranes (alpha and beta), hyaluronic acid based, anorganic bovine bone and anorganic silicone-based membranes. Cell proliferation and cell colonization (Environmental Scanning Electron Microscope, ESEM) analysis were performed. The results of the study demonstrated that four of the examined biomaterial/cell constructs showed a very good proliferation rate and cell density: No. 3 (Tissue Vlies), No. 7 (Sepra film), No. 16 (Biobrane) and No. 17 (Biomend). No favourable group of biomaterials was noticeable. Moreover, the results indicate that these four biomaterials as a part of bone constructs are the best tools for engineering new bone tissue. In contrast, biomaterials No. 19a (Bio-Oss) and 19b (Bio-Oss Collagen) showed the lowest proliferation rates. The result of No. 19b was improved by treatment in the perfusion chamber for 48 h as well as by additional use of vacuum. The present study is an important base for further analysis of biomaterials and consequently for the development of tissue engineering.
Bioartificial Organs↗
Growth of miniature pig parotid cells on biomaterials in vitro.
Both Sjögren's syndrome and therapeutic irradiation for head and neck cancer lead to irreversible damage of the parenchyma of the salivary glands. This report describes an attempt to grow miniature pig (minipig) parotid gland cells on artificial films and tubular scaffolds with the ultimate intention of developing bio-engineered replacement tissue. Minipig parotid cells were isolated and cultured. The growth and structural and physiological features of the cells which were cultured on films and porous tubular scaffolds made from poly(ethylene glycol)-terephthalate (PEGT)/poly(butylene terephthalate) (PBT) were examined. By 9 days, the parotid cells on the films and the tubular scaffolds formed continuous monolayers. The secretory granules and nuclei of the cultured acinar cells remained polarised. Desmosomes, gap junctions and tight-like junctions were still present between the apical regions of adjacent cells. Amylase activity decreased during the culture period but was still evident in the medium after 10 days of culture. In conclusion, minipig parotid cells are well-maintained in vitro on both a flat surface and a three-dimensional (3D) scaffold. The addition of a Matrigel coating to the surface of synthetic materials aids cell growth and maintenance of a morphology that more closely resembles normal epithelium.
Animals↗
Guided tissue regeneration: porcine matrix does not transmit PERV.
OBJECTIVE: For cardiovascular tissue engineering, acellularized scaffolds of porcine matrices have been successfully used. However, the possibility of porcine endogenous retrovirus (PERV) transmission remains debatable. In this study, we investigated whether acellularized porcine vascular scaffolds cause cross-species transmission of PERV in a xenogenic model. METHODS: Porcine pulmonary arteries were acellularized and implanted into sheep in orthotopic position (n=6). Cardiopulmonary bypass support was used for all operations. Blood samples were collected regularly up to 6 months after the operation, and cellular components were tested for PERV infection by PCR and RT-PCR. Grafts were explanted 6 and 12 months after implantation. Tissue samples were characterized by histology and electron microscopy and tested for PERV sequences. RESULTS: All animals survived the procedure and follow up until explantation of the grafts. PERV DNA was detectable in acellularized scaffolds of porcine matrices. Acellular porcine pulmonary arteries scaffolds were repopulated in vivo by autologous cells of the host, leading to a vessel consisting of all cellular components of the vessel wall. No PERV sequences were detectable neither in all tested peripheral blood samples nor in tissue samples of in vivo recellularized grafts up to 6 months after implantation. Electron microscopy revealed no signs of graft infection by retrovirus. CONCLUSIONS: Guided tissue regeneration of acellularized vascular porcine matrix scaffolds leads to structured vessels up to one year without risk of PERV transmisson.
Animals↗