Papers by Author: Jae Ho Jeong

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.

Abstract: As a part of the effort to develop a suitable scaffold for tissue-engineered bone regeneration, we modified calcium metaphosphate (CMP) ceramic with Na20 and evaluated its efficiency as a scaffold. We incorporate 5% Na20 into pure CMP and prepare for an average pore size of 250 or 450 µm average pore sizes. The incorporation of 5% Na2O caused reduced compressive strength and there was no change in biodegradability. The in vitro cellular attachment and proliferation rate, however, were slightly improved. The 5% Na2O-incorporated macroporous CMP ceramic-cell constructs treated with Emdogain induced ectopic bone formation more effectively than those without Emdogain treatment. These results suggest that the incorporation of 5% Na2O into pure CMP is not effective for improving the physical characteristics of pure CMP but it is positive for improving the cellular reaction and osteogenic effect with the addition of Emdogain.

Abstract: Five kinds of gypsums, (1) CaSO4•2H2O (caldium sulfate dihydrate; CSD), (2) CaSO4•1/2H2O (calcium sulfate hemihydrate; CSH), (3) CaSO4 (calcium sulfate anhydrite; CSA), (4) CSH200 (CSH heat-treated at 200°C after self-hardening), and (5) CSH600 (CSH heat-treated at 600°C after self-hardening) were used as candidates for coating materials on calcium metaphosphate (CMP) scaffod to control degradation rate of CMP and to extend degradation limit. The disks of CSD, CSH, CSA, CSH 200, and CSH600 were prepared by self-hardening after mixing with water, where CSH200 and CSH600 were heat-treated at 200°C and 600°C, respectively. In order to control fast resorption rate of gypsum, CMP-CSA composites were prepared with different CSA contents such as 0, 5, 10, 20, 30, 50, and 70 vol% and heat-treated at 900°C for 4 hours. The degradation rates of various gypsums were evaluated in revised simulated body fluid (r-SBF) for 1, 3, 7, and 21 days, respectively. Degradation rate of each specimen was measured in terms of weight loss change with time and degraded surface morphology was examined by SEM. All kinds of gypsums were transformd into CSD after self-hardening with water. Most of gypsums were degraded by 35~60 wt% at 7 days and by 70~99 wt% at 21 days of soaking in SBF. In the group of CMP-CSA composites, the degree of degradation of them was considerably retarded compared to that of five pure gypsums. The surface morphology showed elongated needle-like crystals during the degradation with time.

Abstract: As a part of the efforts to develop a suitable scaffold optimizing bone regeneration that has similar physical properties to bone, we modified calcium metaphosphate (CMP) ceramics with K2O and evaluated their efficiency as a scaffold for tissue engineered bone tissue regeneration. Macroporous CMP ceramics modified by incorporation of 5% K2O to improve biodegradability were prepared to have 250 and 450 µm average pore sizes, respectively. The modified CMP ceramics were cultured with mouse primary calvarial osteoblastic cells in osteogenic media for 2 weeks and these cell-CMP ceramic constructs with or without Emdogain treatment were implanted in the SCID mice subcutaneous pouches. After 1, 2, and 3 weeks, the degree of ectopic bone formation was evaluated. The modified macroporous CMP ceramic-cell constructs treated with Emdogain induced ectopic bone formation, whereas the modified CMP ceramic-cell constructs without Emdogain treatment induced no ectopic bone formation. This result suggests that the Emdogain treatment on cell-scaffold constructs for tissue engineered bone regeneration may be effective for osteogenic activation of attached cells.