Born again bone: tissue engineering for bone repair.
Destruction of bone tissue due to disease and inefficient bone healing after traumatic injury may be addressed by tissue engineering techniques. Growth factor, cytokine protein, and gene therapies will be developed, which, in conjunction with suitable carriers, will regenerate missing bone or help in cases of defective healing. (+info)
Engineering virtual cardiac tissue.
The kinetics of proteins involved in ion transfer, sequestration and binding in cardiac cells can be modelled to construct a model of the electrical activity of isolated cardiac cells as a system of ordinary differential equations. These cell models may be incorporated into tissue models, which, when combined with histology and anatomy, form virtual tissues. The effects of changes in specific protein expression, or changes in protein kinetics, produced by mutations or pharmacological agents, can be simulated using these tissue models and used to account for the whole organ effects of changes in specific ion-transport protein activity. (+info)
Cellular integration of thyrocytes and thyroid folliculogenesis: a perspective for thyroid tissue regeneration and engineering.
Thyroid gland is composed of many spheroid structures called thyroid follicles, in which thyrocytes are integrated in their specific structural and functional polarization. In conventional monolayer and floating cultures, the cells cannot reorganize follicle structures with normal polarity. By contrast, in a 3-D collagen gel culture thyrocytes easily and stably reconstruct follicles with physiological polarity. Integration of thyrocyte growth and differentiation appears to result in eventual thyroid folliculogenesis. 3-D collagen gel culture and subacute thyroiditis, a specific thyroid disorder, are the promising models for addressing the mechanism of thyroid folliculogenesis. Because formation of 3-D follicles actively occurs both in this culture system and at the regenerative stage of the disease. The understanding of the mechanistic basis of folliculogenesis is prerequisite for establishment of an artificial thyroid tissue, which would enable a more physiological approach to the treatment of hypothyroidism caused by various diseases and surgical processes than conventional hormone replacement therapy. In this review, we have discussed thyrocyte integration, and thyroid folliculogenesis and tissue regeneration, to further thyroid biology. Also, we briefly discussed a perspective on thyroid tissue regeneration and engineering. (+info)
Oxygen diffusion and consumption of aortic valve cusps.
To maintain tissue oxygenation, normal aortic valves contain a vascular bed where tissue thickness is greatest. Avascular "living" tissue-engineered heart valves have been proposed, yet little information exists regarding the magnitude of valve tissue metabolic activity or oxygen requirements. We therefore set out to measure the oxygen diffusivity (DO(2)) and oxygen consumption (VO(2)) of seven porcine aortic valve cusps in vitro at 37 degrees C using a chamber with a Clark oxygen sensor. Mean DO(2) and VO(2) were 1.06 x 10(-5) cm(2)/s and 3.05 x 10(-5) x ml O(2). ml tissue(-1) x s(-1), respectively. When modeled as a three-layered structure by using these values and a boundary condition of 100 mmHg at both surfaces, the average aortic cusp predicted a central mean PO(2) of 27 mmHg (range of 0-50 mmHg). The DO(2) value obtained was similar to that found for other vascular structures, but because our studies were carried out in vitro, the VO(2) measurements may be lower than that required by the functioning valves. These values provide an initial understanding of the oxygen supply possible from the cusp surfaces and the oxygen needs of the tissue. (+info)
Self-assembly and mineralization of peptide-amphiphile nanofibers.
We have used the pH-induced self-assembly of a peptide-amphiphile to make a nanostructured fibrous scaffold reminiscent of extracellular matrix. The design of this peptide-amphiphile allows the nanofibers to be reversibly cross-linked to enhance or decrease their structural integrity. After cross-linking, the fibers are able to direct mineralization of hydroxyapatite to form a composite material in which the crystallographic c axes of hydroxyapatite are aligned with the long axes of the fibers. This alignment is the same as that observed between collagen fibrils and hydroxyapatite crystals in bone. (+info)
Contaminants from the transplant contribute to intimal hyperplasia associated with microvascular endothelial cell seeding.
OBJECTIVES: seeding prosthetic grafts with fat-derived microvascular endothelial cells (MVEC) results not only in a non-thrombogenic EC layer, but also in intimal hyperplasia. Here we investigated incidence, composition, progression, and cause of this intimal hyperplasia. DESIGN: EPTFE grafts with MVEC were implanted as carotid interpositions in six dogs with 1 month, and in three dogs with 4, 8 and 12 months follow-up. Grafts seeded without cells, implanted in the contralateral carotid, served as a control. In another three dogs labelled cells were seeded to investigate the contribution of the seeded cells (2-3 weeks). MATERIALS AND METHODS: MVEC were isolated from the falciform ligament. Cells were pressure seeded on ePTFE grafts. Labelling was performed using retroviral gene transduction. The grafts were analysed with immunohistochemical techniques. RESULTS: after 1 month, all patent non-seeded grafts (5/6) showed fibrin and platelet deposition, and all patent seeded grafts (5/6) were covered with a confluent endothelial monolayer on top of a multilayer of myofibroblasts, elastin and collagen. After long term follow-up, all non-seeded grafts were occluded, all patent seeded grafts (4 and 12 months) were covered with an EC-layer with intimal hyperplasia underneath. The thickness of the intima did not progress after 1 month. Transduced cells were found in the endothelial monolayer, hyperplastic intima and luminal part of the prosthesis. CONCLUSIONS: MVEC seeding in dogs results in intimal hyperplasia in all patent grafts, which contains myofibroblasts. Contaminants from the transplant contribute to this intimal hyperplasia. (+info)
Replacing and renewing: synthetic materials, biomimetics, and tissue engineering in implant dentistry.
Hundreds of thousands of implantations are performed each year in dental clinical practice. Dental implants are a small fraction of the total number of synthetic materials implanted into the human body in all fields of medicine. Basically, these millions of implants going into humans function adequately. But longevity and complications still are significant issues and provide opportunities for the creation of improved devices. This manuscript briefly reviews the history of dental implant devices and the concepts surrounding the word "biocompatibility." It then contrasts the foreign body reaction with normal healing. Finally, the article describes how ideas gleaned from the study of normal wound healing can be applied to improved dental implants. In a concluding section, three scenarios for dental implants twenty years from now are envisioned. (+info)
Expression of renal cell protein markers is dependent on initial mechanical culture conditions.
The rotating wall vessel is optimized for suspension culture, with laminar flow and adequate nutrient delivery, but minimal shear. However, higher shears may occur in vivo. During rotating wall vessel cultivation of human renal cells, size and density of glass-coated microcarrier beads were changed to modulate initial shear. Renal-specific proteins were assayed after 2 days. Flow cytometry antibody binding analysis of vitamin D receptor demonstrated peak expression at intermediate shears, with 30% reduction outside this range. Activity of cathepsin C showed the inverse pattern, lowest at midshear, with twofold increases at either extreme. Dipeptidyl-peptidase IV had no shear dependence, suggesting that the other results are specific, not universal, changes in membrane trafficking or protein synthesis. On addition of dextran, which changes medium density and viscosity but not shear, vitamin D receptor assay showed no differences from controls. Neither cell cycle, apoptosis/necrosis indexes, nor lactate dehydrogenase release varied between experiments, confirming that the changes are primary, not secondary to cell cycling or membrane damage. This study provides direct evidence that mechanical culture conditions modulate protein expression in suspension culture. (+info)