Papers by Author: S.O. Kim

Abstract: The purpose of this study is to confirm the possibility of regenerating actual fat tissue using human adipose tissue-derived stem cells (ASCs) and hyaluronic acid-collagen sponge in animal model. Human ASCs of young female adults were isolated and culture expanded in basal media. At the second passage, cultured ASCs suspension containing 106 cells was applied on prewetted scaffolds the hyaluronic acid-collagen sponge and the sponges was exposed to adipogenic media for the 1week. Then the tissue engineered constructs were implanted into the subcutaneous pocket on the back of immunodeficient athymic nude mice for 3 weeks. Hyaluronic acid-collagen sponges without human ASCs were used as the control. After 3 weeks, specimens were harvested and adipogenic potentials were assessed with histological examination, RT-PCR for PPAR-γ2 expression and G-3-PDH activity. Tissue engineered fat tissue from ASCs and hyaluronic acid-collagen sponges demonstrated PPAR-γ2 positive expression and positive Oil red O staining. The histologic study showed definitive adipose tissue and rich vascular tissue within the engineered fat. Two-fold higher activities of G-3-PDH were identified in experimental group after 3 weeks as compared to control. By contrast, the specimen from control group did not show active vessel ingrowth and contained only few cellular elements within the scaffold. The control specimens failed to demonstrate adipogenic gene markers and were negative in oil red O staining. In conclusion, human ASCs can be differentiated into adipocytes and actual fat tissue engineering was possible with combination of adequate scaffold materials, such as hyaluronic acid-collagen sponges. These data demonstrate that fat tissue engineered from human ASCs can retain predefined shape and dimension for soft tissue augmentation and reconstruction of defects.

Abstract: Despite many outstanding research works on cartilage tissue engineering, actual clinical application is not quite successful because of the absorption and progressive distortion of tissue engineered cartilage. We have developed a new method of cartilage tissue engineering comprising chondrocyte mixed Pluronic F-127 and cultured chondrocyte cell sheet which entirely cover the cell-Pluronic complex. We believe the addition of cultured chondrocyte cell sheet enhances the efficacy of chondrogenesis in vivo. Human ear cartilage piece was enzymatically dissociated and chondrocyte suspension was acquired. Chondrocytes were cultured and expanded as the routine manner. Cultured chondrocytes were plated in high-density monolayer and cultured with Chondrogenic media in 5% CO2 incubator. After 3 weeks of culture, chondrocyte cell sheet was formed and complete single sheet of chondrocyte could be harvested by gentle manipulation of culture plate with a cell scraper. Chondrocyte-Pluronic complex was established by mixing 1x 106 cells with 0.5 of Pluronic F- 127. Chondrocyte-Pluronic complex was completely covered with a sheet of cultured chondrocyte. The completed tissue engineered constructs were implanted into the subcutaneous tissue pocket of nude mice on the back. Tissue engineered constructs without cultured cell sheet were used as control. Samples were harvested at 8 weeks postoperatively and they were subjected to histological analysis and assayed for glycosaminoglycan (GAG), and type II collagen. Grossly, the size of cartilage specimen of cultured chondrocyte cell sheet covered group was larger than that of the control. On histologic examination, the specimen of cultured chondrocyte cell sheet covered group showed lacunae-containing cells embedded in a basophilic matrix. The chondrocyte cell sheet covered group specimen resembled mature or immature cartilage. The result of measurement of GAG and type II collagen of cartilage specimen of cultured chondrocyte sheet covered group was higher than that of the control. In conclusion, the new method of cartilage tissue engineering using chondrocyte cell sheet seems to be an effective method providing higher cartilage tissue gain and reliable success rate for cartilage tissue engineering.