Search

Utilization of biodegradable metals in biomedical fields is emerging because it avoids high-risk and uneconomic secondary surgeries for removing implantable devices. Mg and its alloys are considered optimum materials for biodegradable implantable devices because of their high biocompatibility; however, their excessive and uncontrollable biodegradation is a difficult challenge to overcome. Here, we present a novel method of inhibiting Mg biodegradation by utilizing reduced nicotinamide adenine dinucleotide (NADH), an endogenous cofactor present in all living cells. Incorporating NADH significantly increases Mg corrosion resistance by promoting the formation of thick and dense protective layers. The unique mechanism by which NADH enables corrosion inhibition was discovered by combined microscopic and spectroscopic analyses. NADH is initially self-adsorbed onto the surface of Mg oxide layers, preventing Cl− ions from dissolving Mg oxides, and later recruits Ca2+ ions to form stable Ca-P protective layers. Furthermore, stability of NADH as a corrosion inhibitor of Mg under physiological conditions were confirmed using cell tests. Moreover, excellent cell adhesion and viability to Mg treated with NADH shows the feasibility of introduction of NADH to Mg-based implantable system. Our strategy using NADH suggests an interesting new way of delaying the degradation of Mg and demonstrates potential roles for biomolecules in the engineering the biodegradability of metals.

There has been a tremendous amount of research in the past decade to optimize the mechanical properties and degradation behavior of the biodegradable Mg alloy for orthopedic implant. Despite the feasibility of degrading implant, the lack of fundamental understanding about biocompatibility and underlying bone formation mechanism is currently limiting the use in clinical applications. Herein, we report the result of long-term clinical study and systematic investigation of bone formation mechanism of the biodegradable Mg-5wt%Ca-1wt%Zn alloy implant through simultaneous observation of changes in element composition and crystallinity within degrading interface at hierarchical levels. Controlled degradation of Mg-5wt%Ca-1wt%Zn alloy results in the formation of biomimicking calcification matrix at the degrading interface to initiate the bone formation process. This process facilitates early bone healing and allows the complete replacement of biodegradable Mg implant by the new bone within 1 y of implantation, as demonstrated in 53 cases of successful long-term clinical study.

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.

Objective 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. Methods 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). Results 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. Conclusion 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.

Ni-YSZ (Yttria Stabilized Zirconia) composite powders were fabricated by glycine nitrate process. The prepared powders were sintered at for 4 h in air and reduced at for 2 h in a nitrogen and hydrogen atmosphere. The microstructure, electrical conductivity, thermal expansion and mechanical properties of the Ni-YSZ cermets have been investigated with respect to the volume contents of Ni. A porous microstructure consisting of homogeneously distributed Ni and YSZ phases together with well-connected grains was observed. It was found that the open porosity, electrical conductivity, thermal expansion and bending strength of the cermets are sensitive to the volume content of Ni. The Ni-YSZ cermet containing 40 vol% Ni was ascertained to be the optimum composition. This composition offers sufficient open porosity of more than 30 %, superior electrical conductivities of 917.4 S/cm at and a moderate average thermal expansion coefficient of between room temperature and .

When viewed using a magnetic resonance imaging (MRI) system, invasive materials inside the human body, in many cases, severely distort the MR image of human tissues. The degree of the MR image distortion increases in proportion not only to the difference in the susceptibility between the invasive material and the human tissue, but also to the intensity of the magnetic field induced by the MRI system. In this study, by blending paramagnetic Ti particles with diamagnetic graphite, we synthesized Ti100-xCx composites that can reduce the artifact in the MR image under the high-strength magnetic field. Of the developed composites, Ti70C30 showed the magnetic susceptibility of χ = 67.6 × 10, which corresponds to 30% of those of commercially available Ti alloys, the lowest reported in the literature. The level of the MR image distortion in the vicinity of the Ti70C30 composite insert was nearly negligible even under the high magnetic field of 4.7 T. In this paper, we reported on a methodology of designing new structural materials for bio-applications, their synthesis, experimental confirmation and measurement of MR images. (Received December 1, 2011)

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.

Objectives: The purpose of this study is to identify whether the change of pH affects the proliferation and the differentiation of human bone marrow stem cells (hBMSCs) and what mechanism is underlied. Methods: To achieve objective of this study, hBMSCs were cultivated in the conditioned media adjusted to potential of hydrogen (pH) ranging from 6.4 to 8.0 using addition of hydrochloric acid (HCl) and sodium hydroxide (NaOH). The ratio of proliferation of hBMSCs according to the change of pH was measured for 24 h, 48 h, and 72 h using water-soluble tetrazolium salt (WST)-8 method. To elucidate the mechanism involved, hBMSCs was subjected to blocking extracellular signal-regulated kinases (ERK) and calcium sensing receptor (CaSR) activation. The Osteogenicrelated genes and alkaline phosphatase (ALP) activity were tested under the conditioned media. Results: The proliferation of hBMSCs was promoted under extracellular alkali conditions (pH 7.6~8.0) via CaSR/ ERK pathway. On the other hand, the differentiation was inhibited/delayed via decreased ALP activity besides gene expression at pH 8.0. Conclusion: Extracellular alkali or acidic surrounding according to pH alteration can play a crucial role in hBMSC behavior including the proliferation and the differentiation. [Korean Journal of Bone Metabolism, 19(1): 35-46, 2012]

Purpose: To elucidate the relation between fracture healing and angiogenesis, we checked expression of Hypoxia-inducible factor (HIF) and Vascular endothelial growth factor (VEGF) in hypoxic cell cultures and the callus from a rat femur fracture model. Materials and Methods: Human osteoblasts, chondrocytes, and rat ST2 cells were cultured in DME/F12 media with 10% FBS. Hypoxic DME/F12 media (PO2

Objective: To investigate the influence of associated medical diseases and complications on functional improvement after in-patient through stroke rehabilitation. Method: We performed a retrospective analysis on medical records of 183 stroke patients who had admitted to the department of rehabilitation medicine. Functional Independence Measure (FIM), Modified Barthel Index (MBI) at admission and discharge were used to assess the functional status. We investigated medical diseases, such as hypertension, diabetes, myocardial infarct, atrial fibrillation osteoarthritis, rheumatoid arthritis, previous history of stroke and complications such as dementia, post-stroke depression, central post-stroke pain, complex regional pain syndrome, neglect and aphasia. Results: Post-stroke patients with myocardial infarct, atrial fibrillation, osteoarthritis, dementia, aphasia and neglect significantly showed lower gain of FIM and MBI, lower FIM and MBI efficacy during inpatient rehabilitation compared to without those (p 0.05). Total numbers of associated medical diseases and complications negatively affect on FIM and MBI efficacy (p

Ganglioneuroblastoma is a rare tumor originating from the sympathetic chain. It is intermediate between the highly malignant neuroblastoma and the benign ganglioneuroma. The predilection sites of ganglioneur- oblastoma are the retroperitoneum and mediastinum but involvement of the structures around the spinal cord is infrequent. A 4 year-old girl who had progressive weakness in both lower extremities had a tiptoe gait for 2 months. A magnetic resonance imaging (MRI) study revealed a heterogeneous enhancing mass in the right mediastinum and paraspinal areas. A biopsy of the mass confirmed a ganglioneuroblastoma with many neuroblasts and nodules of ganglion cells. This is an unusual case of a child with spastic paraplegia caused by ganglioneuroblastoma of the thoracic cavity. (Korean J Hematol 2007;42:414-418.)