Papers by Author: Young Il Yang

Abstract: The effect of β-glucan-reinforced PLGA scaffold on cell proliferation was investigated. The PLGA scaffolds were prepared by salt-leaching method. The prepared scaffolds were grafted with (1→3) (1→6)-β-glucan in various ratios after plasma treatment on the surface. The surface of the scaffold was characterized by scanning electron microscope (SEM). The HDFs (Human dermal fibroblasts, 1
105 cells/scaffold) were used to evaluate the cell proliferation on PLGA scaffold before and after plasma/β-glucan treatment. In results, in the β-glucan treated scaffolds, the pores seemed to become narrower and even looked like closed form. The result of cell proliferation showed that the plasma/β-glucan treated scaffolds had narrower pores because the β-glucan was attached in the pores that would not be allowed the cells to penetrate into the inner areas. Consequently, cell proliferation was not effective in the plasma/β-glucan treated scaffolds in this study.

Abstract: New strategies to make cultured fibroblasts grafts more appealing are aimed at reducing the time spent in culture and improving the handling and biologic properties. In the present study, we developed a simple and effective method to fabricate dermal fibroblasts-populated membrane based on (1) the use of fibrin as a 3-dimensional matrix and (2) the use of cell- mediate contraction to make a self assembled, detachable cells-populated membrane. Human dermal fibroblasts were cultured by explants method. The fibroblasts encapsulated in fibrin were transferred into 6-well culture plates which pretreated with Sigmacoat® to prevent cell binding on surface of culture dish. Fibroblasts populated fibrin matrix (FPFM) was cultured in attached condition for 7 days and in free floating condition for 1 day. The FPFM were contracted, spontaneously released from culture plate, compacted, and formed tissue-like membrane. The fabricated FPFM revealed uniformly distributed cells and newly synthesized extracellular matrix was deposited in matrix. FPFM could successfully graft into full-thickness cutaneous defect of nude mice, and showed significantly increased wound closure rate. Our results demonstrate that the FPFM membrane delivery system allows for restoration of both the epidermal and dermal compartments.

Abstract: Fibrin is a natural substrate for growth, adhesion, and migration of mature endothelial cells (ECs) and a candidate coating material in approaches to graft endothelialization. Adipose tissue represents an abundant, practical source of donor tissue for stem cells which may be a useful source for engineering of vascular grafts. However, the optimal substrates that promote differentiation of adipose tissue-derived stem cells (ASCs) into ECs remain to be elucidated. In the present study, we investigated whether fibrin can be used as a substratum to support in vitro ECs differentiation of ASCs and whether fibrinogen concentration can be affect on ECs differentiation of ASCs. For determination of phenotypic characteristics of ASCs used in this experiment, we performed flow cytometry analysis. ASCs were plated on fibrin composed of varying concentrations of fibrinogen and induced into ECs differentiation in presence of VEGF. Before inducing into ECs, ASCs did not express any markers of hematopoietic cells (CD34, CD45), ECs (CD31, CD34), and endothelial progenitor cells (CD34, CD133, Flk-1). The degree of ECs differentiation was determined by capillary network formation, ECs-specific gene expression, and F-actin assembly. During the first 12 h after seeding, cells spread randomly, moved and formed small interconnected clusters. These clusters decreased in size and formed a capillary tube at 48 h. During the further incubation in presence of VEGF for 7 days, ASCs expressed mRNA and protein of von Willebrand factor (vWF). The degree of ECs differentiation of ASCs was consistently decreased as fibrinogen concentration increase. Fibrin may be used as biomatrix to promote differentiation of ASCs into ECs for tissue engineering.

Abstract: The goal of this study was to investigate effects of fibrin reinforcement of collagen sponges on fibroblasts-mediated contraction and in vivo tissue regeneration, especially angiogenesis. Human dermal fibroblasts (HDFs)-populated collagen sponges reinforced with or without fibrin were cultivated via the free-floating method in vitro. They were then evaluated using xenogeneic implantation into nude mice. The HDFs-populated collagen sponges reinforced with fibrin exhibited significantly decreased HDFs-mediated contraction in vitro (p<0.05). Microvascular and cellular densities of the collagen sponges were significantly higher with fibrin than without (p<0.01). Cell ingrowths, neovascularization, and deposition of ECM matrix were more evenly distributed in the fibrin-reinforced collagen matrices. The results demonstrated that fibrin reinforcement of porous collagen sponges can reduce cell-mediated contraction in vitro while enhancing functional integration with surrounding tissue in vivo.

Abstract: Fibrin is a natural polymer with excellent biocompatibility and widely used as a cell delivery vehicle in tissue engineering. However, fibrin of low concentration is not able to promote cell growth and differentiation within a desired time because of contraction and biodegradation of cell-seeded matrices. In this study we investigated effects of combining fibrin with collagen on growth and osteogenic differentiation of bone marrow stromal cells (BMSCs). Rabbit BMSCs-populated fibrin hydrogels with or without collagen were fabricated and cultured by the free floating method for 4 weeks. The DNA content of fibrin/collagen matrix significantly increased the growth of BMSCs compared to the fibrin-only matrix at 2week. Alkaline phosphatase activity was significantly higher in the fibrin/collagen matrix (71.0 nmol of p-nitrophenol /min/disc) than the fibrin-only matrix (45.1 nmol of p-nitrophenol /min/disc). Deposition of calcium was not significantly different between two groups. Histological examination also revealed more matured organization and deposition of collagen fibers and more concentric calcium deposition in the fibrin/collagen matrix compared to the fibrin-only matrix. These results indicated that fibrin/collagen matrix could be more effective than fibrin alone in supporting growth and osteogenic differentiation of BMSCs.

Abstract: A culture system that is capable of providing even and uniform distribution and deposition of cells and extracellular matrix (ECM) is desired to enhance biological functions of the tissue-engineered artificial dermis (TEADs). For this purpose, we have developed a perfusion culture system that offers uniform exchange of nutrients and gases along the scaffold. Viability and effectiveness of the system were investigated by comparing biological and mechanical properties of TEADs. Results showed that the TEADs constructed by the perfusion culture system revealed significantly increased cell growth, ECM synthesis, and elastic modulus compared to those by the conventional static culture system. In addition, histological findings indicated that cells were more evenly distributed and ECM deposition increased in TEADs with the perfusion culture system. Therefore, it can be suggested that the perfusion culture system can constitute a more promising approach for constructing the TEADs.