No abstract available.
Biocompatible Materials*

Recently, thanks to the rapid progress of new technologies in cell modulation, extracellular matrix fabrication and synthetic polymers mimicking bodily structures, the self-regeneration of bodily defects by host tissue has been considered by many researchers. The conventional science of art in biomaterials has been concerned with restoring damaged tissue using non-biological materials such as metals, ceramics and synthetic polymers. To overcome the limitations of using such non-viable materials, several attempts to construct artificial organs mimicking natural tissue by combining modulated cells with extracellular matrix-hybridized synthetic polymers have produced many worthy results with biologically functioning artificial tissues. The process involved in manufacturing biomaterials mimicking living tissue is generally called tissue engineering. However recently, the extension of knowledge about cell biology and embryology has naturally moved the focus from tissue restoration to tissue regeneration. Especially, embryonic and mesenchymal stem cells are attractive resources due to their potential for the differentiation of various tissue cells in response to signal transduction mediated by cytokines. Although no one knows yet what is the exact factor responsible for a stem cell's ability to differentiate between specific cells to generate specific tissue, what has been agreed is that delivering stem cells into the body provides a strong potential for the regeneration of tissue. In this review, the historical issues and future possibilities involved in medical tissue restoration and tissue regeneration are discussed.
Animal ; Biocompatible Materials/therapeutic use ; Biodegradation ; Biomedical Engineering*y ; Cell Transplantation/methods ; Extracellular Matrix/physiology ; Growth Substances/therapeutic use ; Growth Substances/administration & dosage ; Human ; Polymers/therapeutic use ; Regeneration* ; Stem Cells/transplantation

A hyaluronic acid (HA) incorporated porous collagen matrix was fabricated at -70 degree C by lyophilization. The HA incorporated collagen matrix showed increased pore size in comparison with collagen matrix. Biodegradability and mechanical properties of matrices were controllable by varying the ultraviolet (UV) irradiation time for cross-linking collagen molecules. Addition of HA to collagen matrix did not effect ultimate tensile stress after UV irradiation. HA incorporated collagen matrices demonstrated a higher resistance against the collagenase degradation than collagen matrix. In an in vitro investigation of cellular behavior using dermal fibroblasts on the porous matrix, HA incorporated collagen matrix induced increased dermal fibroblast migration and proliferation in comparison with collagen matrix. These results suggest that the HA incorporated collagen porous matrix assumes to enhance dermal fibroblast adaptation and regenerative potential.
Collagen/*metabolism ; Extracellular Matrix/*metabolism ; Fibroblasts/*physiology ; Human ; Hyaluronic Acid/*metabolism ; Porosity

Preclinical evaluation of medical devices (prototype products) offers the opportunity to investigate and study the intended use of device materials. Preclinical evaluation programs are designed to determine the efficacy, safety, and biocompatibility of biomaterials, prostheses, and medical devices. The purpose of safety testing is to determine if a material presents potential harm to the human; it evaluates the interaction of the material with the in vivo environment and determines the effect of the host on the implant. Preclinical evaluation is the determination of the ability of the prototype product to perform with appropriate host response in a specific application, considered from the perspective of human clinical use. Therefore, preclinical data should include materials science and engineering, biology, biochemistry, medicine, host reactions and their evaluation, the testing of biomaterials, and the degradation of materials in a biological environment.
Animal ; Carcinogenicity Tests ; Equipment and Supplies*/adverse effects ; Hemolysis ; Human ; Pyrogens/toxicity ; Sterilization

This study investigated that whether a 2 mT, 60 Hz, sinusoidal electromagnetic field (EMF) alters the structure and function of cells. This research compared the effects of EMF on four kinds of cell lines: hFOB 1.19 (fetal osteoblast), T/G HA-VSMC (aortic vascular smooth muscle cell), RPMI 7666 (B lymphoblast), and HCN-2 (cortical neuronal cell). Over 14 days, cells were exposed to EMF for 1, 3, or 6 hours per day (hrs/d). The results pointed to a cell type-specific reaction to EMF exposure. In addition, the cellular responses were dependent on duration of EMF exposure. In the present study, cell proliferation was the trait most sensitive to EMF. EMF treatment promoted growth of hFOB 1.19 and HCN-2 compared with control cells at 7 and 14 days of incubation. When the exposure time was 3 hrs/d, EMF enhanced the proliferation of RPMI 7666 but inhibited that of T/G HA- VSMC. On the other hand, the effects of EMF on cell cycle distribution, cell differentiation, and actin distribution were unclear. Furthermore, we hardly found any correlation between EMF exposure and gap junctional intercellular communication in hFOB 1.19. This study revealed that EMF might serve as a potential tool for manipulating cell proliferation.
Signal Transduction ; Microfilaments/radiation effects ; Humans ; Gap Junctions/metabolism/radiation effects ; *Electromagnetic Fields ; Cell Proliferation/radiation effects ; Cell Physiology/*radiation effects ; Cell Line ; Cell Differentiation/radiation effects ; Cell Cycle/radiation effects

This study investigated that whether a 2 mT, 60 Hz, sinusoidal electromagnetic field (EMF) alters the structure and function of cells. This research compared the effects of EMF on four kinds of cell lines: hFOB 1.19 (fetal osteoblast), T/G HA-VSMC (aortic vascular smooth muscle cell), RPMI 7666 (B lymphoblast), and HCN-2 (cortical neuronal cell). Over 14 days, cells were exposed to EMF for 1, 3, or 6 hours per day (hrs/d). The results pointed to a cell type-specific reaction to EMF exposure. In addition, the cellular responses were dependent on duration of EMF exposure. In the present study, cell proliferation was the trait most sensitive to EMF. EMF treatment promoted growth of hFOB 1.19 and HCN-2 compared with control cells at 7 and 14 days of incubation. When the exposure time was 3 hrs/d, EMF enhanced the proliferation of RPMI 7666 but inhibited that of T/G HA- VSMC. On the other hand, the effects of EMF on cell cycle distribution, cell differentiation, and actin distribution were unclear. Furthermore, we hardly found any correlation between EMF exposure and gap junctional intercellular communication in hFOB 1.19. This study revealed that EMF might serve as a potential tool for manipulating cell proliferation.
Signal Transduction ; Microfilaments/radiation effects ; Humans ; Gap Junctions/metabolism/radiation effects ; *Electromagnetic Fields ; Cell Proliferation/radiation effects ; Cell Physiology/*radiation effects ; Cell Line ; Cell Differentiation/radiation effects ; Cell Cycle/radiation effects

A composite material consisting of carbonate apatite (CAp) and type I atelocollagen (AtCol) (88/12 in wt/wt%) was designed for use as an artificial bone substitute. CAp was synthesized at 58 degrees C by a solution-precipitation method and then heated at either 980 degrees C or 1,200 degrees C. In this study, type I AtCol was purified from bovine tail skins. A CAp-AtCol mixture was prepared by centirfugation and condensed into composite rods or disks. The scanning electron-microscopic (SEM) characterization indicated that the CAp synthesized at 58 degrees C displayed a crystallinity similar to that of natural bone and had a high porosity (mean pore size: about 3-10 microns in diameter). SEM also revealed that the CAp heated at 980 degrees C was more porous than that sintered at 1,200 degrees C, and the 1,200 degrees C-heated particles were more uniformly encapsulated by the AtCol fibers than the 980 degrees C-heated ones. A Fourier transformed-infrared spectroscopic analysis showed that the bands characteristic of carbonate ions were clearly observed in the 58 degrees C-synthesized CAp. To enhance the intramolecular cross-linking between the collagen molecules, CAp-AtCol composites were irradiated by ultraviolet (UV) ray (wave length 254 nm) for 4 hours or vacuum-dried at 150 degrees C for 2 hours. Compared to the non cross-linked composites, the UV-irradiated or dehydrothermally cross-linked composites showed significantly (p < 0.05) low collagen degradation and swelling ratio. Preliminary mechanical data demonstrated that the compressive strengths of the CAp-AtCol composites were higher than the values reported for bone.
Animal ; Apatites*/chemistry ; Bone Substitutes*/chemistry ; Bone Transplantation ; Cattle ; Collagen*/chemistry

The effects of centrifugal force on growth and differentiation of osteoblastic cells cultured in alpha-MEM containing 1% Fetal bovine serum were investigated by assays of DNA synthesis, alkaline phosphatase activity and osteocalcin- production in osteoblastic MC3T3-E1 cells. Centrifugation of the cells in low concentrations (1%) of fetal bovine serum caused a 1.9-fold increase of [3H] thymidine incorporation on day 3 from the start of centrifugation, and gradually decreased with culture up to day 9. Alkaline phosphatase activity was not affected by centrifugal force until day 5, and increased rapidly after day 7. Stimulation of DNA synthesis by centrifugation was abolished in the presence of H-7, an inhibitor of protein kinase C. These results suggest that centrifugal force stimulates the proliferation of osteoblastic cells through an autocrine secretion of some diffusable growth- promoting activity. Additional centrifugation of the cells also slightly stimulated alkaline phosphatase activity, although this did not directly influence the cell's osteocalcin-production activity.
Alkaline Phosphatase/metabolism ; Animal ; Cell Division ; Cells, Cultured ; Centrifugation ; DNA/biosynthesis ; Mice ; Osteoblasts/*physiology ; Stress, Mechanical

Biomaterials for medical use have been developed in accordance with progress of the fields of medicine, biochemistry, material science, and pharmaceutics. Advances in the medicine have changed the concept of surgery from the deletion of damage tissue for the preservation of the remaining healthy tissue to the reconstruction or replacement of damaged tissue by promoting regeneration of the natural tissue. All the materials used in medicine should be biocompatible. Conventional materials such as metals, ceramics, and synthetic polymers are usually bioinert and support the structural defects. But recently introduced biomaterials are designed to provide biological functions as much a possible by mimicking natural tissue structures.
Biocompatible Materials* ; Biomedical Engineering ; Ceramics ; Human ; Metals ; Polymers ; Prostheses and Implants/trends*

The authors have experienced a case of Takayasu's arteritis associated with Takayasu's retinopathy which is confirmed by aortography and fluorescent angiography in a 14 year old female.
Adolescent ; Angiography ; Aortography ; Arteritis* ; Female ; Humans ; Takayasu Arteritis