PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Tissue Engineering”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed2006

Structural and nanoindentation studies of stem cell-based tissue-engineered bone.

Stem cell-based gene therapy and tissue engineering have been shown to be an efficient method for the regeneration of critical-sized bone defects. Despite being an area of active research over the last decade, no knowledge of the intrinsic ultrastructural and nanomechanical properties of such bone tissue exists. In this study, we report the nanomechanical properties of engineered bone tissue derived from genetically modified mesenchymal stem cells (MSCs) overexpressing the rhBMP2 gene, grown in vivo in the thigh muscle of immunocompetent mice for 4 weeks, compared to femoral bone adjacent to the transplantation site. The two types of bone had similar mineral contents (61 and 65 wt% for engineered and femoral bone, respectively), overall microstructures showing lacunae and canaliculi (both measured by back-scattered electron microscopy), chemical compositions (measured by energy dispersive X-ray analysis), and nanoscale topographical morphologies (measured by tapping-mode atomic force microscopy imaging or TMAFM). Nanoindentation experiments revealed that the small length scale mechanical properties were statistically different with the femoral bone (indented parallel to the bone long axis) being stiffer and harder (apparent elastic modulus, E approximately 27.3+/-10.5 GPa and hardness, H approximately 1.0+/-0.7G Pa) than the genetically engineered bone (E approximately 19.8+/-5.6 GPa, H approximately 0.9+/-0.4G Pa). TMAFM imaging showed clear residual indents characteristic of viscoelastic plastic deformation for both types of bone. However, fine differences in the residual indent area (smaller for the engineered bone), pile up (smaller for the engineered bone), and fracture mechanisms (microcracks for the engineered bone) were observed with the genetically engineered bone behaving more brittle than the femoral control.

Biomechanical Phenomena↗
PubMed2005

Tissue-engineered human vascular media with a functional endothelin system.

BACKGROUND: Cardiovascular diseases remain a major cause of death and disability in the Western world. Among the various approaches adopted to counteract the morbidity associated with these diseases, surgical procedures and cardiac and vascular xenotransplantations or allotransplantations are routinely performed. The suitable vascular graft would be as close as possible to the native and healthy vessel composed exclusively of human components provided by the patient and would adapt to the donor's hemodynamics. We have developed such a tissue-engineered human blood vessel reconstructed with human cells. Because endothelin is the most potent vasopressor known to date, we were interested in investigating the functionality of the endothelinergic system in our reconstructed human blood vessel. METHODS AND RESULTS: Vasoconstriction studies were performed with nonselective and selective agonists and antagonists to demonstrate that ET(A) receptors were present and functional in tissue-engineered human vascular media constructed with the self-assembly method. Reverse-transcriptase polymerase chain reaction studies demonstrated that mRNA of the ET(A) but not the ET(B) receptor was present in these human tissue-engineered blood vessels. Furthermore, we demonstrated that the endothelin-converting enzyme, the main enzyme responsible for the formation of the biologically active endothelin peptides, was present and functional in these same bioengineered vascular media. CONCLUSIONS: Our results suggest that the media component of our tissue-engineered blood vessel has the potential of controlling vascular resistance via the presence of functional endothelin ET(A) receptors and endothelin-converting enzyme.

Aspartic Acid Endopeptidases↗
PubMed2005

Tissue engineering of human heart valve leaflets: a novel bioreactor for a strain-based conditioning approach.

Current mechanical conditioning approaches for heart valve tissue engineering concentrate on mimicking the opening and closing behavior of the leaflets, either or not in combination with tissue straining. This study describes a novel approach by mimicking only the diastolic phase of the cardiac cycle, resulting in tissue straining. A novel, yet simplified, bioreactor system was developed for this purpose by applying a dynamic pressure difference over a closed tissue engineered valve, thereby inducing dynamic strains within the leaflets. Besides the use of dynamic strains, the developing leaflet tissues were exposed to pre-strain induced by the use of a stented geometry. To demonstrate the feasibility of this strain-based conditioning approach, human heart valve leaflets were engineered and their mechanical behavior evaluated. The actual dynamic strain magnitude in the leaflets over time was estimated using numerical analyses. Preliminary results showed superior tissue formation and non-linear tissue-like mechanical properties in the strained valves when compared to non-loaded tissue strips. In conclusion, the strain-based conditioning approach, using both pre-strain and dynamic strains, offers new possibilities for bioreactor design and optimization of tissue properties towards a tissue-engineered aortic human heart valve replacement.

Aortic Valve↗
PubMed2004

Tissue-engineered small intestine improves recovery after massive small bowel resection.

OBJECTIVE: Rescue with tissue-engineered small intestine (TESI) after massive small bowel resection (MSBR). SUMMARY BACKGROUND DATA: Short bowel syndrome is a morbid product of massive small bowel resection. We report the first replacement of a vital organ by tissue engineering with TESI after MSBR. METHODS: Ten male Lewis rats underwent TESI implantation with green fluorescent protein (GFP)-marked cells (TESI+, n = 5) or sham laparotomy (TESI-, n = 5) followed by MSBR. Side-to-side anastomosis of TESI to proximal small intestine was performed or omitted. TESIO animals underwent implantation of engineered intestine with no further surgery. Weights were measured QOD until day 40. Transit times were measured. DNA assay was performed with computer morphometry. Northern blots of RNA were probed for intestinal alkaline phosphatase (IAP) and villin. Hematoxylin and eosin, S100, and smooth muscle actin immunohistochemistry were performed. Blood was collected at sacrifice. RESULTS: All 10 rats initially lost then regained weight. The initial rate of weight loss was higher in TESI+ versus TESI-, but the nadir was reached a week earlier with more rapid weight gain subsequently to 98% preoperative weight on day 40 in animals with engineered intestine versus 76% (P < 0.03). Serum B12 was higher at 439 pg/mL versus 195.4 pg/mL. IAP mRNA appeared greater in TESI+ than TESIO, with constant villin levels. Histology revealed appropriate architecture including nerve. GFP labeling persisted. CONCLUSIONS: Anastomosis of TESI significantly improved postoperative weight and B12 absorption after MSBR. IAP, a marker of differentiation in intestinal epithelium, is present in TESI, and GFP labeling was accomplished.

Actins↗
PubMedDate not supplied

The use of advanced biological and tissue-engineered wound products.

This article aims to reintroduce readers to biologically based and tissue-engineered wound management products. Indications for their use in clinical practice are suggested. It also examines two well-established wound management interventions, topical negative pressure therapy and larval therapy, which could have a positive effect on the outcome of biologically based and tissue-engineered wound management products.

Adjuvants, Immunologic↗
PubMed2003

[Repair of alveolar bone defect with tissue engineered bone: an experimental study of dogs].

OBJECTIVE: To study the feasibility of repairing experimental horizontal alveolar bone defects by tissue engineering based on bone marrow stromal cells (BMSC). METHODS: Dog bone marrow mononuclear cells were isolated from the bone marrow by gradient centrifugation and then cultured in conditional medium to be induced to become osteogenic. Immunohistochemistry was used to examine the expression of core-binding factor alpha subunit 1 (Cbfa1), osteocalcin (OCN), and type I collagen in the cultured BMSCs. Histochemical technique was used to examine the expression of alkaline phosphatase (AKP) in the BMSCs. Inversed phase-contrast microscopy and electron microscopy were used to observe the morphology and proliferation of the BMSCs. Induced BMSCs at passage 3 were harvested and mixed with calcium alginate to form a gelatin form cell-scaffold construct. A horizontal alveolar bone defect (5 mm high) was created surgically in each buccal side of the mandibular premolars 3 and 4 and molar 1 of 11 dogs. The defects was randomly repaired with a cell-scaffold construct (experimental group, 20 teeth), calcium alginate alone (control group A, 15 teeth), or left untreated (control group B, 12 teeth). At four, twelve, and twenty-four weeks after operation, 2, 7, 2 dogs were killed respectively and block sections of mandibular bones at the defects were collected and processed for gross and histological observation as well as X-ray examination. The status of bone repair 12 weeks after operation in the 3 groups was compared. RESULT: In vitro induced BMSCs exhibited an osteogenic phenotype. Since the passage 3 calcium salt sedimentation could be seen in the extracellular stroma of BMSCs. Cbfa1, type I collagen, and AKP were expressed in the BMSCs in every passage. OCN was expressed since the second passage. Histologically, bone nodule structure was observed in the experimental group 4 weeks after operation. The engineered bone became more mature, similar to the normal bone, 12 weeks after operation. Twelve weeks after operation, the alveolar ridge regeneration amounted to a repair height of 2.43 +/- 0.93 mm, 0.98 +/- 0.87 mm, and 0.78 +/- 0.75 mm and reached 48.59%, 19.74%, and 15.76% of the original height in the experimental group, control group A, and control group B respectively, with a significant difference between the experimental and control groups A and B (all P < 0.01). CONCLUSION: BMSCs can be induced to become osteogenic and be used as seed cells to engineer bone tissue and repair experimental alveolar bone defect.

Alkaline Phosphatase↗
PubMed1998

Videofetoscopically assisted fetal tissue engineering: skin replacement.

BACKGROUND/PURPOSE: Treatment of several congenital anomalies is frequently hindered by lack of enough tissue for surgical reconstruction in the neonatal period. The purposes of this study were (1) introduction of a novel concept in perinatal surgery, involving minimally invasive harvest of fetal tissue, which is then processed through tissue engineering techniques in vitro while pregnancy is allowed to continue, so that, at delivery, the newborn can benefit from having autologous, expanded tissue promptly available for surgical implantation at birth; (2) analysis of the progress of an engineered fetal skin graft with time, after implantation in the neonate; and (3) study of the effects of current tissue engineering techniques on fetal keratinocytes and fetal dermal fibroblasts. METHODS: Ten 90- to 95-day-gestation fetal lambs underwent surgical creation of two large paramedian excisional skin defects on the posterior body wall. Subsequently, fetal skin specimens no larger than 1.5 x 1.5 cm were videofetoscopically harvested. Fetal keratinocytes and dermal fibroblasts were then separately cultivated and expanded in vitro for 45 to 50 days, resulting in a total of approximately 250 to 300 million cells. Seven to 10 days before fetal delivery, all cells were seeded in two layers on a 16 to 20-cm2, 3-mm thick biodegradable polyglycolic acid polymer matrix. One to 4 days after delivery, the autologous engineered skin was implanted over one of two previously created skin defects. The second skin defect region received an absorbable polymer scaffold without cells as a control. If necessary, the original skin wounds were further amplified before implantation. Each animal provided at least one time-point for histological analysis of both types of repair through excisional biopsies performed at weekly intervals, up to 8 weeks postimplantation. Normal skin specimens were also used as controls. RESULTS: Fetal and neonatal survival rates were 100%. Based on previous postnatal skin engineering studies, fetal dermal fibroblasts multiplied significantly faster in vitro (approximately fivefold) than expected. Fetal keratinocytes multiplied at expected postnatal rates. The engineered grafts induced faster epithelization of the wound (partial at 1 week and complete between 2 and 3 weeks postoperatively) than did the acellular ones (partial at 3 weeks and complete between 3 and 4 weeks postoperatively). Analysis of skin architecture showed a higher level of epidermal organization and less dermal scarring in the wounds that received the engineered, cell-implanted polymer scaffold. CONCLUSIONS: (1) Videofetoscopically assisted fetal tissue engineering is a viable method for obtaining expanded autologous tissue for prompt surgical reconstruction at birth. (2) Fetal skin can be expanded and engineered in vitro at faster rates than expected postnatally, with current tissue engineering techniques. (3) Engineered autologous fetal skin induces a faster and more organized healing of neonatal skin defects than that observed with second intention. This concept may prove useful for the treatment of certain human neonatal conditions such as giant neoplasias, ectopia cordis, and other body wall defects.

Animals↗
PubMed2004

Mesenchymal stem cell-based cartilage tissue engineering: cells, scaffold and biology.

Cartilage repair and regeneration by stem cell-based tissue engineering could be of enormous therapeutic and economic potential benefit for an aging population. However, to use stem cells effectively, their natural environment must be understood in order to expand them in vitro without compromising their multilineage potential and their specific differentiation program. Collaboration between diverse academic disciplines and between research and regulatory government agencies and industry is crucial before cell-based cartilage tissue engineering can achieve its full therapeutic potential.

Adult↗
PubMed2005

Matrix testing for urothelial tissue engineering.

INTRODUCTION: Surgical reconstruction of the bladder is associated with many well-known complications. Tissue engineering is under discussion as a potential therapeutic strategy and many of the proposed benefits are of special interest for children. Biomaterials play a key role in tissue engineering. Many materials have been proposed for the experimental reconstruction of the bladder and urethra. They determine the biological and mechanical characteristics of the reconstructed tissues. Most publications focus on a single material. In order to identify the most suitable biomaterial it was the aim of this study to compare biological and mechanical features of different biomaterials seeded with urothelial cells in vitro. MATERIALS AND METHODS: Commercially available biomaterials (Biogide, Ethisorb, Lyoplant, SIS, Vicryl, Xenoderm) of biologic or synthetic origin were seeded with urothelial cells. Cell-matrix constructs were cultured and investigated by scanning electron microscopy for surface structure and cell morphology. They were also subjected to extension until failure and the force required was reported as f (max). Values obtained and curve shape were compared to specimens of bladder mucosa and submucosa. RESULTS: Cell adhesion and morphology showed marked differences between materials. Cell shape varied from single spherical cells to confluent layers of flat urothelium. f (max) ranged from 0.02 N to 48.86 N for tested materials and 1.19 N for native bladder mucosa/submucosa. DISCUSSION: The materials showed marked differences in biological and mechanical features in vitro. Cells cultured on biogenic matrices were more similar to native urothelium. Most of the tested materials showed different curve shapes and higher f (max) values than native bladder mucosa.

Animals↗
PubMed2003

Liver tissue engineering within alginate scaffolds: effects of cell-seeding density on hepatocyte viability, morphology, and function.

Tissue engineering with three-dimensional biomaterials represents a promising approach for developing hepatic tissue to replace the function of a failing liver. Herein, we address cell seeding and distribution within porous alginate scaffolds, which represent a new type of porous biomaterial for tissue engineering. The hydrophilic nature of the alginate scaffold as well as its pore structure and interconnectivity enabled the efficient seeding of hepatocytes into the scaffolds, that is, 70-90% of the initial cells depending on the seeding method. Utilization of centrifugal force during seeding enhanced cell distribution in the porous scaffolds, consequently enabling the seeding of concentrated cell suspensions (>1 x 10(7) cells/mL). Cell density in scaffolds affected hepatocyte viability as judged by MTT assay. At a cell density of 0.28 x 10(6) cells/cm3 scaffold, the number of viable hepatocytes decreased to 33% of its initial value within 7 days, whereas at the denser cultures, 5.7 x 10(6) cells/cm3 scaffold and higher, the cells maintained higher viability while forming a network of connecting spheroids. In the high-density cellular constructs, hepatocellular functions such as albumin and urea secretion, and detoxification (cytochrome P-450 and phase II conjugating enzyme activities), remained high during the 7-day culture. Collectively, the results of the present study highlight the importance of cell density on the hepatocellular functions of three-dimensional hepatocyte constructs as well as the advantages of alginate matrices as scaffoldings.

7-Alkoxycoumarin O-Dealkylase↗
PubMed2006

Tissue engineering in musculoskeletal problems related to haemophilia.

This article is a review of how advances in tissue engineering can be applied to the musculoskeletal pathology of patients with haemophilia. This article will also explain the theory that the deterioration of joints in patients with haemophilia is due to biological and mechanical causes. Current concepts of tissue engineering would be to replace the degenerated and damaged tissue by live cells, using them as a biological implant. However, before these new technologies are applied, an appropriate control of their indication and results is required.

Cartilage Diseases↗
PubMedDate not supplied

Tissue-engineered skin in the healing of wound stumps from limb amputations secondary to purpura fulminans.

Currently wound treatment options of amputation stumps due to purpura fulminans include healing by secondary intention from wound debridement, split-thickness skin grafting, tissue and muscle flaps, plantar skin free transfer, skin expansion, artificial skin, and hyperbaric oxygen therapy. We saw a 6-month-old girl with purpura fulminans as a complication of meningococcemia. She developed necrosis of the distal extremities resulting in bilateral amputation of the lower limbs. Shortly thereafter the leg stumps also became necrosed and she underwent unsuccessful split-thickness grafts of lower limb ulcers. The patient's difficult-to-heal wounds made her an excellent candidate for treatment with tissue-engineered skin. At 10 months of age, this was applied to her previously nonhealing wounds. The tissue-engineered skin induced rapid healing of the patient's chronic amputation stump ulcers and provided her with substantial pain relief. In conclusion, tissue-engineered skin appears to be a potential beneficial treatment for chronic wounds in children with nonhealing amputation stumps.

Amputation, Surgical↗
PubMed2002

[Progress in studies of tissue-engineered heart valves].

Valve replacement represents the most common surgical therapy for valvular heart diseases. However, the long-term results of the valve protheses in clinical use are not satisfying. Recently, with the development of tissue engineering, more and more studies are focusing on creating ideal valve substitutes through seeding autologous cells on biodegradable scaffold. This article describes the definition of valvular tissue engineering, the choice of scaffold biomaterials, the methods of cell culture and seeding, and the evaluation of tissue-engineered heart valves. Furthermore, the problems which should be resolved in the future are also presented in the article.

Animals↗
PubMed2006

Enhancing the drug metabolism activities of C3A--a human hepatocyte cell line--by tissue engineering within alginate scaffolds.

In this study, we investigated the applicability of C3A--a human hepatocyte cell line--as a predicting tool for drug metabolism by applying tissue-engineering methods. Cultivation of C3A cells within alginate scaffolds induced the formation of spheroids with enhanced drug metabolism activities compared to that of two-dimensional (2-D) monolayer cultures. The spheroid formation process was demonstrated via histology, immunohistochemistry, and transmission electron microscope (TEM) analyses. The C3A spheroids displayed multilayer cell morphology, characterized by a large number of tight junctions, polar cells, and bile canaliculi, similar to spheroids of primary hepatocytes. Spheroid formation was accompanied by a reduction in P-glycoprotein (Pgp) gene expression and C3A cell proliferation was limited mainly to cells on the spheroid outskirt. The 3-D constructs maintained a nearly constant cell number according to MTT assay. Drug metabolism by the two most important cytochrome p-450 (CYP) enzymes in human liver, CYP1A2 and CYP3A4, was tested using preferred drugs. With CYP1A2, 3-fold enhancement in activity per cell was seen for converting ethoxyresorufin to resorufin compared to C3A cell monolayers. The spheroids responded to the inducer beta-naphthoflavone and to the inhibitor furafylline of CYP1A2. Enhanced metabolizing activity of CYP3A4, measured by the amount 6beta-testosterone formed from testosterone, and that of the phase II enzyme glucuronosyltransferases (UGT) further indicated that the tissue-engineered C3A spheroids may provide an efficient experimental tool for predicting drug activities by these CYPs. Moreover, the maintenance of constant cell number, as well as the elevated hepatocellular functions and drug metabolism activities, suggest that the tissue-engineered C3A may be applicable in replacement therapies.

Androgens↗