Kang-Sik Lee

Asan Medical Center, Sŏul, Seoul, South Korea

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Publications (7)17.43 Total impact

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    ABSTRACT: Feasibility studies were performed to determine the suitability of a novel synthesis technique for fabricating multifunctional composite materials for orthopedic implants. By blending paramagnetic Ti powder with diamagnetic graphite and consolidating the resulting mixtures, Ti-C composites that cannot be feasibly obtained via conventional alloying techniques or ingot metallurgy were synthesized. The synthesized composite material exhibited extremely low magnetic susceptibility (χ=67.6×10(-6)), and, as a result, exhibited fewer artifacts during magnetic resonance imaging. The strength of the composite material (σ=770MPa) was such that it could support external loads to which the human body is subjected, but its Young's modulus was low (E=81.9 GPa) such that it could mitigate the stress-shielding effect. The material was also free from toxic elements such as Al and V and, thus, can be considered less harmful. Copyright © 2014. Published by Elsevier Ltd.
    Acta Biomaterialia. 10/2014;
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    ABSTRACT: The aims of the present study were to determine the exact role of osteoclasts in the biodegradation of calcium phosphate ceramics of different solubilities, and to investigate the relationship between osteoclastic activity and extracellular Ca2+ concentration. Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) disks were incubated in culture medium, without cells, to evaluate chemical dissolution. On other disks, osteoclasts were cultured to analyze cell-mediated resorption. After 5 days, the area fraction resorbed by chemical dissolution of β-TCP disks (54.3%) was significantly greater than that of HA disks (4.0%, p 0.0001). The number of tartrateresistant acid phosphatase (TRAP)-positive cells (osteoclasts) and the TRAP-positive area were found to be much greater on HA disks than on β-TCP disks. The area fraction of resorption lacunae on HA was 16.0%, thus significantly greater than that on β-TCP (3.6%, p = 0.0009). Ca2+ concentration in the culture medium was significantly higher in β-TCP group than in HA group. In conclusion, β-TCP is biodegraded principally by chemical dissolution, whereas HA is degraded by osteoclastic resorption. The more conspicuous osteoclastic degradation evident on HA was attributable to the superior cellular adherence and migration properties as well as to differentiation of precursor cells. Higher Ca2+ concentrations on β-TCP implants inhibited osteoclastic activity by those mechanisms.
    Journal of Applied Statistics 10/2014; 6(10). · 0.45 Impact Factor
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    ABSTRACT: Magnesium metal and its alloys have been proposed as a novel class of bone implant biomaterials because of their biodegradability and mechanical properties. The purpose of this study was to determine whether magnesium ions, which are released abundantly from alloys, affect proliferation and differentiation of human bone marrow-derived stromal cells (hBMSCs). High levels of magnesium ions did not induce cytotoxicity in hBMSCs, but treatment with 2.5-10 mm magnesium ions for 48-72 h significantly increased hBMSC proliferation. The expression of integrins α2 and α3, but not β1, was upregulated compared with the control and shifted from α3 to α2 in hBMSCs treated with magnesium ions. Knockdown of integrins α2 and/or α3 significantly reduced magnesium-induced proliferation of hBMSCs. Magnesium exposure profoundly enhanced alkaline phosphatase (ALP) gene expression and activity even at a relatively low magnesium concentration (2.5 mm). Exposure to magnesium ions facilitated hBMSC proliferation via integrin α2 and α3 expression and partly promoted differentiation into osteoblasts via the alteration of ALP expression and activity. Accordingly, magnesium could be a useful biomaterial for orthopaedic applications such as bone implant biomaterials for repair and regeneration of bone defects in orthopaedic and dental fields. Copyright © 2014 John Wiley & Sons, Ltd.
    Journal of Tissue Engineering and Regenerative Medicine 02/2014; · 4.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Feasibility studies were performed to determine the suitability of a novel synthesis technique for fabricating multifunctional composite materials for orthopedic implants. By blending paramagnetic Ti powder with diamagnetic graphite and consolidating the resulting mixtures, Ti-C composites that cannot be feasibly obtained via conventional alloying techniques or ingot metallurgy were synthesized. The synthesized composite material exhibited extremely low magnetic susceptibility (χ=67.6×10(-6)), and, as a result, exhibited fewer artifacts during magnetic resonance imaging. The strength of the composite material (σ=770MPa) was such that it could support external loads to which the human body is subjected, but its Young's modulus was low (E=81.9 GPa) such that it could mitigate the stress-shielding effect. The material was also free from toxic elements such as Al and V and, thus, can be considered less harmful. Copyright © 2014. Published by Elsevier Ltd.
    Acta Biomaterialia. 10/2014;
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    ABSTRACT: Crystalline Mg-based alloys with a distinct reduction in hydrogen evolution were prepared through both electrochemical and microstructural engineering of the constituent phases. The addition of Zn to Mg-Ca alloy modified the corrosion potentials of two constituent phases (Mg + Mg2Ca), which prevented the formation of a galvanic circuit and achieved a comparable corrosion rate to high purity Mg. Furthermore, effective grain refinement induced by the extrusion allowed the achievement of much lower corrosion rate than high purity Mg. Animal studies confirmed the large reduction in hydrogen evolution and revealed good tissue compatibility with increased bone deposition around the newly developed Mg alloy implants. Thus, high strength Mg-Ca-Zn alloys with medically acceptable corrosion rate were developed and showed great potential for use in a new generation of biodegradable implants.
    Scientific Reports 08/2013; 3:2367. · 5.08 Impact Factor
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    ABSTRACT: This study was undertaken to generate and characterize human induced pluripotent stem cells (PSCs) from patients with osteoarthritis (OA) and to examine whether these cells can be developed into disease-relevant cell types for use in disease modeling and drug discovery. Human synovial cells isolated from two 71-year-old women with advanced OA were characterized and reprogrammed into induced PSCs by ectopic expression of 4 transcription factors (Oct-4, SOX2, Klf4, and c-Myc). The pluripotency status of each induced PSC line was validated by comparison with human embryonic stem cells (ESCs). We found that OA patient-derived human synovial cells had human mesenchymal stem cell (MSC)-like characteristics, as indicated by the expression of specific markers, including CD14-, CD19-, CD34-, CD45-, CD44+, CD51+, CD90+, CD105+, and CD147+. Microarray analysis of human MSCs and human synovial cells further determined their unique and overlapping gene expression patterns. The pluripotency of established human induced PSCs was confirmed by their human ESC-like morphology, expression of pluripotency markers, gene expression profiles, epigenetic status, normal karyotype, and in vitro and in vivo differentiation potential. The potential of human induced PSCs to differentiate into distinct mesenchymal cell lineages, such as osteoblasts, adipocytes, and chondrocytes, was further confirmed by positive expression of markers for respective cell types and positive staining with alizarin red S (osteoblasts), oil red O (adipocytes), or Alcian blue (chondrocytes). Functional chondrocyte differentiation of induced PSCs in pellet culture and 3-dimensional polycaprolactone scaffold culture was assessed by chondrocyte self-assembly and histology. Our findings indicate that patient-derived synovial cells are an attractive source of MSCs as well as induced PSCs and have the potential to advance cartilage tissue engineering and cell-based models of cartilage defects.
    Arthritis & Rheumatology 10/2011; 63(10):3010-21. · 7.48 Impact Factor
  • The Journal of the Korean Orthopaedic Association 01/2011; 46(4):273.
  • Source
    The Journal of the Korean Orthopaedic Association 01/2008; 43(4).