Papers by Author: Jong Won Rhie

Abstract: In cartilage tissue engineering, as a cell source, adult stem cells are very attractive for clinical applications. Recent studies suggest that human adipose tissue-derived stromal cells (ASCs) have multilineage potential similar to bone marrow-derived stromal cells (BMSCs). ASCs are obtained from adipose tissue easily isolated by suction-assisted lipectomy in various body parts. Also, as one of major factors of cartilage tissue engineering, scaffolds have an important role in cartilage formation. Poly(L-lactide-co-ε-carprolactone) scaffolds have physiological activity, biodegradability, high cell affinity, and mechano-activity. The object of this study is cartilaginous tissue formation using highly elastic PLCL scaffolds and ASCs in vitro and in vivo. Poly(L-lactide-co-ε-carprolactone) copolymers were synthesized from lactide and ε-carprolactone in the presence of stannous octoate as catalyst. The scaffolds with 85% porosity and 300-500μm pore size were fabricated by gel-pressing method. ASCs were seeded on scaffolds and cultured for 21days in vitro. Cell/polymer constructs were characterized by reverse transcriptase-polymerase chain reaction for confirming differentiation to chondrocytes onto PLCL scaffolds. Also, for examining cartilaginous tissue formation in vivo, ASCs seeded scaffolds which were induced chondrogenesis for 2 weeks were implanted in nude mice subcutaneously for up to 8weeks. Histological studies showed that implants partially developed cartilaginous tissue within lacunae. And there was an accumulation of sulfated glycoaminoglycans. Immunohistochemical analysis revealed that implants were positively stained for specific extracellular matrix. These results indicate that ASCs and PLCL scaffols could be used to cartilage tissue engineering.

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.

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: Pluronic F127 has received increasing attention over many years as drug delivery systems, biomaterials, and hydrogels for tissue engineering. In this study, we synthesized temperature-sensitive and cell-adhesive triblock F127 copolymers, in which Arg-Gly-Asp (RGD) peptide ligand was grafted to Pluronic F127-4-methacryloxyethyl trimellitic anhydride (4-META) to obtain F127-META-RGD. The chemical structures of the F127-META-RGD block copolymers were confirmed by FTIR, 1H and 13C NMR, and GPC. The resultant F127-META-RGD showed very similar thermosensitive behaviors to F127 and F127-META. The critical micelle temperature (CMT) of the F127 copolymers decreased in the order of F127 < F127-META < F127-META-RGD, whereas the particle size followed an opposite trend. Interactions between the F127 copolymers and adipose-derived stem cells (ASC) were evaluated in terms of cell adhesion and proliferation on the hydrogel. These thermosensitive RGD-grafted Pluronic hydrogels that display the enhanced cell adhesiveness, are expected to be useful as a functional injectable scaffold for tissue engineering.

Abstract: This paper compares the characteristics of chondrocyte adhesion on two types of threedimensional (3-D) scaffold: types A and B. These 3-D scaffolds can be repeatedly constructed with the same dimensions using microstereolithography, a system that allows the fabrication of predesigned internal structures, such as pore size and porosity, by stacking the photopolymerized material. In tissue engineering, chondrocyte adhesion to a scaffold should have a major effect on the regeneration of cartilage. In this regard, we evaluated chondrocyte adhesion to two types of scaffold and found that chondrocyte adhesion was better on the type B scaffold than on the type A, demonstrating the importance of scaffold geometry in chondrocyte adhesion.

Abstract: We fabricated micro-patterned 2.5-D scaffolds using micro-end-milling with controlled pore and island sizes and interconnectivity to determine the effects of the micro-patterns on the cell culturing process. Micro-end-milling can easily realize a high aspect ratio and accuracy, and can be applied to various materials, including those that are biocompatible and biodegradable. Sixteen types of micro-patterned scaffolds were designed and fabricated using the micro-end-milling process. Fibroblasts were seeded and cultured to examine the viability of the developed micropatterned scaffolds and their absorbed cell adhesion. The results confirmed that the fabricated micro-patterns functioned successfully as scaffolds.