Key Engineering Materials Vols. 342-343

Abstract: In-stent restenosis is the result of a healing process that induces neointimal hyperplasia though mechanisms that are still not understood. The purpose of this study was to analyze the early histologic consequences and the kinetics of the healing process for a 72-hours period after stent implantation in an organ culture model. MTT-tests show that the vessel could maintain activity in the organ culture system. The vessel with stent had a different morphology and inflammatory molecule release compared with the normal vessel. So there could have direct relationships between inflammatory release and neointimal hyperplasia. The organ culture system can provide valuable information for studies of in-stent restenosis after stent implantation, especially for evaluation of new stents, such as drug-coated or other surface-modified stents.

Abstract: Rapamycin/curcumin co-loaded and rapamycin-loaded poly(lactide-co-glycolide)(PLGA) films were prepared by a casting method. The components of different drug-loaded films were analyzed by Fourier transform infrared spectroscopy (FTIR), and the major peaks of rapacymin and curcumin were both observed in these films. Compared to the rapamycin-loaded film, the results of in vitro platelet adhesion tests show that the number of adhered platelets reduce, and few aggregated and activated platelets are observed. The APTTs (activated partial thromboplastin time) of rapamycin/curcumin co-loaded films is nearly 6 seconds longer than for the rapamycin-loaded PLGA films. All results indicate that curcumin may suppress thrombosis activated by rapamycinloaded film, and improve the anticoagulative property. The results of alamar blue indicate that the rapamycin/curcumin co-loaded film has better antiproliferation effect than 316 stainless steel (SS).

Abstract: A tubular and fibrous scaffold was fabricated from an elastic polymer, poly (L-lactideco- ε-caprolactone) (PLCL; Mn 193,813, Mw 538,623) 50:50 by using a novel gel spinning apparatus. To characterize the gel-spun scaffold, we investigated morphology, tensile property, tissue in-growth rate and degradation rate. From SEM images, fibrous structure in the scaffold wasn’t fabricated well in the condition of 4% gel concentration. In general, the thickness level of microfibers increased as the gel concentration increased. In addition, the gel-spun scaffolds showed stronger tensile properties in the circumferential direction than the longitudinal direction. 5%, 7.5%, 10% and 12.5% scaffolds were analyzed in both directions: circumferential direction and longitudinal direction. On the other hand, the gel-spun scaffolds have been implanted in mouse to examine the degradation rate in vivo and tissue in-growth aspects, compared to extruded scaffolds. Both shows very similar degradation rates, but the aspect in tissue in-growth was different. In conclusion, gel-spun PLCL scaffolds have good characteristics as a plausible scaffold for cardiovascular tissue engineering.

Abstract: In this study, we find out the possibilities to make conduit for nerve regeneration using biodegradable polymers, which have enough mechanical strength in surgery. Cell adhesion (PC12) behaviors about various nerve conduits have not great difference compared to control. This is regarded due to specific structure of nerve conduits formed nano-fibers. In the case of PPD, we observed better phenotype of adhered cell than PLGA samples. Also, PPD-PLGA bi-layered nerve conduits were more effective than PLGA nerve conduit for in vitro evaluation.

Abstract: Acknowledging the supportive influence of matrix molecules on the chondrocytic phenotype, we combined heparin and chitosan to develop a novel biomaterial, supporting chondrogenesis. Chitosan had been shown as a promising structural material for a number of tissue engineering applications. Similar to heparin, one of the glycosamino-glycans (GAGs) had been known to exert various influences on the biological activities. In this study we evaluated the potential of heparin/chitosan polyelectrolyte complex materials for controlling the proliferation and differentiation of chondrocytes. The heparin/chitosan polyelectrolyte complex was coated over the polyethyleneimine (PEI) layer precoated on the commercial polystyrene dish. When examined by using human chondrocyte cell line (C28/I2), the heparin/chitosan surfaces supported well not only the cell proliferation but also the chondrocytic functions, such as expression of collagen type II. These results indicated that the heparin/chitosan complex could be used to modulate the activity of chondrocytes in vitro.

Abstract: Porosity and pore size are needed for successful cell seeding and proliferation into porous scaffolds. This study was focused on a hydrogel-seeding method to improve cell adhesion and proliferation in tubular porous scaffolds for vascular grafts application. Tubular scaffolds were fabricated from a biodegradable elastic polymer, poly(L-lactide-co-ε-caprolactone) (PLCL) (50:50, Mn 1.58×105), by an extrusion-particulate leaching method. Vascular smooth muscle cells (VSMCs) were dispersed in collagen hydrogel and then seeded into the tubular PLCL scaffolds having various pore sizes, 50-100 μm, 100-200 μm, and 300-500 μm, respectively. As a result, the efficiency of cell adhesion and proliferation was dependent on the pore size of the scaffolds. Especially, the cell proliferation efficiency was improved by using the hydrogel-seeding method as compared with by using a previously established method. In summary, this study demonstrates that the efficiency of cell adhesion and proliferation was dependent on the pore size of the scaffolds in the hydrogel-seeding method.

Abstract: In theory, Ultraviolet (UV)-generated free radicals can expedite Acellular dermal matrix (ADM) crosslinking with glucose via the formation of reactive, linear glucose molecules. The aim of this study is to maintain strength and stability of UV-irradiated ADM without the introduction of cytotoxic chemical crosslinkers. The strength and stability changes of ADM by UV-irradiated with glucose (GLUC) were investigated under various conditions. ADM strength and stability were determined by tensile testing, differential scanning calorimetry (DSC), and swelling ratio. After exposure to UV-irradiation, ADM containing glucose revealed different mechanical properties compare to ADM without glucose, greater resistance to enzymatic degradation, and higher heatdenatured breaking loads. DSC explained that glucose-incorporated ADM sterilized by UVirradiation decreased peak width (Tpeak-Ts) compared to one another. On the other hand, Area (J/g) and Ts increased glucose-incorporated ADM. The exposure of ADM to UV caused significant increase in hydration, but a significant decrease in the swelling ratio compared with the nonirradiated ADM. These data strongly suggests that free radical-dependent, glucose-derived crosslinks provide enhanced strength and enzyme resistance in glucose-incorporated, UV-exposed ADM.

Abstract: The effects of various processing parameters of electro spinning such as concentration, applied voltage, distance from needle to collector on the morphology(especially fiber diameter) of nanofiber matrix was investigated in this study. We found out the concentration of polymer solution was the key parameter to control the fiber diameter. Such a difference on surface morphology of electro spun nanofiber matrix under various processing parameters will show the different behaviors on protein adsorption on the surface contacting with body fluid. Consequently, this results different cell motions on the matrix used on tissue engineering. To evaluate the adsorption of proteins on the surface of sheet type nanofiber matrix, matrix obtained by electro spinning were immersed in FITC labeled proteins solutions. And then, we confirmed adsorption of proteins using laser scanning confocal microscopy (LSCM). The quantitative analysis of adsorbed proteins was also investigated by UV spectroscopy.

Abstract: Human adipose tissue contain a population of pluripotent stem cells capable of differentiating along multiple mesenchymal cell lineages. The goal of this study was to examine the chondrogenic potential of adipose-derived stem (ADS) cells. ADS cells were isolated from human subcutaneous adipose tissue obtained by lipectomy and liposuction, and were expanded and grown in vitro with or without chondrogenic medium in micromass culture condition and 3D culture condition in PLGA(poly(lactic-co-glycolic acid)) scaffold. Human ADS cells of micromass culture condition and 3D culture condition in PLGA scaffolds, were differentiated with chondrogenic medium consisted of transforming growth factor-β1, insulin-transferrin-selenium, dexamethasone and ascorbate-2-phosphate. ADS cells abundantly synthesized cartilage matrix molecules including collagen type II, VI and link protein. ADS cells under high-density micromass culture condition with chondrogenic medium formed well defined nodules within 48 hours of induction. On the 3rd week after chondrogenic differentiation of ADS cells under the micromass culture condition and 3D culture condition of PLGA scaffold, mRNA of type II collagen, type VI collagen and link protein were expressed by reverse transcription polymerase chain reaction (RT-PCR). On the 3weeks, content of glycosaminoglycan in cells treated with chondrogenic medium was greater than that with non chondrogenic medium(control).On the 3rd week culture under the chondrogenic medium, hematoxylin & eosin (H & E) staining, alcian blue staining and type II collagen immunohistochemistry analysis confirmed the chondrogenic differentiation in micromass and 3D cultured specimen. These findings document the ability of ADS cells to produce characteristic cartilage matrix molecules, and provide the possibility of cartilage regeneration for cartilage substitution.

Abstract: Alginate was a proven biocompatible biomatrice for cells but it was known not to provide a proper microenvironment needed for the proliferation of cells because of its anionic property, which caused its low affinity for cells. Water-soluble chitosan was well known as wound healing material and it also had cationic property which helped cell-to-matrix adhesion. The purpose of this study is to assess the ability of a chitosan/alginate mixed sponge as a scaffold for preadipocytes to serve as a biological implant for soft tissue augmentation. Chitosan/alginate and calcium alginate sponges were made by lyophilizing of alginate with water-soluble chitosan mixture and with calcium chloride mixture, respectively, and those were observed by SEM. Preadipocytes seeded in those sponges were cultured for 2 weeks. In vivo study was designed that chitosan/alginate sponges with and without preadipocytes were implanted subcutaneously into nude mouse. Chitosan/alginate and calcium alginate sponges which had highly porosity and 50-200㎛ pore size. In the chitosan/alginate sponge, the levels of DNA amount were significantly higher than those in calcium alginate sponge (P<0.05). In both groups, they increased progressively with time. On the in vivo study, it was observed that adipose tissue layer in the margin of chitosan/alginate sponge on the 2 weeks after implantation of nude mouse. On the 8 weeks after implantation, thick layer of adipose tissue and neovascularization were observed in the chitosan/alginate sponge. Consequently, chitosan/alginate sponge provided proper microenvironment to human preadipocyte, increased the cell proliferation and maintained the pore that offered neovascularization, so turned out to be effective form of fat transplantation for soft tissue augmentation and reconstruction.