Biomedical subjects

Jeong Koo Kim

Publications and source records attributed to Jeong Koo Kim.

9 recordsLinked to original sources

PubMed2006

Beneficial effects of freezing rate determined by indirect thermophysical calculation on cell viability in cryopreserved tissues.

Many types of mammalian cells, such as sperm, blood, embryos, etc., have been successfully cryopreserved for the last few decades, while no optimal method for the cryopreservation of mammalian tissues or organs has been established, showing a poor survival after thawing with a low recovery of function. In this study, the freezing rate was determined by indirect thermodynamic calculation, and its potential effect on the cryoprotection of human saphenous veins and tissue-engineered bones was investigated. The vein segments were frozen according to the calculated freezing rate, using rate-controlled freezing devices, with a freezing solution composed of 10% dimethylsulphoxide and 20% fetal bovine serum in RPMI 1640 media. The efficacy of indirect calculation was assessed by the cell viability measured using fluorescence double-staining methods. The results indicated that the freezing rate determined by indirect calculation significantly (P < 0.05) maintained the post-thaw cellular viability of the blood vessel, particularly in terms of the endothelial cells. However, it exerted relatively less protective effect on the osteoblastic cell-cultured scaffolds. These results suggest that freezing-induced injuries may occur in tissues, and the freezing rate determined by indirect thermophysical calculation can be used for the optimization of tissue cryopreservation by minimizing the injuries.

Animals↗

PubMed2006

Chemotactic migration of human mesenchymal stem cells and MC3T3-E1 osteoblast-like cells induced by COS-7 cell line expressing rhBMP-7.

During bone development, remodeling, and repair, bone morphogenetic proteins (BMPs) induce the differentiation of mesenchymal progenitor cells (MPCs) that enter into the osteoblastic lineage, and enhance the recruitment of MPCs and osteogenic cells. The process of migration is believed to be regulated, in part, by growth factors stored within the bone matrix, which are released by bone resorption. In this study, primary human mesenchymal stem cells (hMSCs) and MC3T3-E1 osteoblasts were examined for chemotaxis in response to recombinant human BMP-7 (rhBMP-7) produced in COS-7 cells (co-culture system). In order to produce BMP-7 transfected cells (BTCs), which serve as suppliers of rhBMP-7 under in vitro culture conditions, the encoding DNA was transferred into the pTARGET expression vector and introduced into COS-7 cells by conventional genetic engineering techniques. In cell culture studies, the rhBMP-7 produced in BTCs stimulated the specific activity of ALP, the production of cAMP in response to PTH, and the synthesis of osteocalcin. Migration assays were conducted with a computer-aided time-lapse video-microscopy system, to allow the rapid and precise analysis of cell migration and for the dynamic measurement of cell position and morphology. The migration distance and speed of the MC3T3-E1 cells, or hMSCs, co-cultured with BTCs, using a band-type seeding method, were significantly increased (p < 0.001), compared to those of the MC3T3-E1 cells (or hMSCs) only. In conclusion, these studies revealed that rhBMP-7 plays a role in the migration of bone-forming cells, and that the co-culture model (co-culture of bone-forming cells with BMP-7-producing cells) using a computer-aided, time-lapse video-microscopy system, is useful for the chemotactic migration assay of other chemotactic growth factors.

3T3 Cells↗

PubMed2006

Construction of functional soft tissues from premodulated smooth muscle cells using a bioreactor system.

Artificial smooth muscle tissues should be constructed with well-differentiated and aligned smooth muscle cells (SMCs) for proper functioning. In a previous study, we produced cell/scaffold hybrids composed of consistently aligned SMCs in a contractile state using cyclic mechanical strain. In this study, the preconditioned hybrids were organized as functional smooth muscle constructs, which had a high cellular density, using a bioreactor system. We determined that the alignment and contractile phenotype of the initially generated SMCs would be retained after a 7-day culture period in a bioreactor. Mechanical properties of the smooth muscle constructs were measured and compared with those of native smooth muscle tissues and acellular scaffolds. The constructs had a denser cell concentration than the preconditioned hybrids, although they were not fully filled with cells. The premodulated cell alignment and contractile phenotype were retained after culture in a bioreactor. The 7-day-cultured constructs had similar allowed stress levels to native tissues while their stiffness was much lower, suggesting that they had malleable and durable characteristics. These results suggest that functional smooth muscle tissues with mechanical stability can be produced using premodulated SMCs and a bioreactor system.

Actins↗

PubMed2006

Biological responses of ligament fibroblasts and gene expression profiling on micropatterned silicone substrates subjected to mechanical stimuli.

In this study, ligament fibroblasts were cultivated on micropatterned silicone substrates and subjected to cyclic stretching to simulate the in vivo biomechanical environment during ligament healing. Without stretching, ligament fibroblasts were aligned parallel to the microgrooves on the silicone substrate surface. However, we previously reported that uniaxial cyclic stretching induces alignment perpendicular to the stretching axis. With stretching on a microgrooved surface, cell proliferation and collagen production were greatly enhanced. The exact functions of the micropatterned surface and mechanical stimuli are unknown. Therefore, in gene expression microarray experiments, genes whose expression is inhibited by subculture from passage 0 (P0) to passage 8 (P8) and enhanced by micropatterning and stretching were sought out. The following six genes were selected: MGP, GADD45A, UNC5B, TGFB1, COL4A1, and COL4A2. The selected genes play fundamental roles in cell proliferation, differentiation, apoptosis, and structural maintenance. On the basis of the obtained gene expression profiles, we identified candidate genes that might be involved in responses to a micropatterned surface and mechanical stretching.

Anterior Cruciate Ligament↗

PubMed2005

Enhanced neurite outgrowth of rat neural cortical cells on surface-modified films of poly(lactic-co-glycolic acid).

Neural cortical cells, isolated from prenatal rat cerebra, were grown on surface-modified poly(lactic-co-glycolic acid, 65:35) (PLGA) films coated with poly-D: -lysine (PDL) with either laminin (LN), fibronectin (FN) or collagen (CN). Immunocytochemistry showed that the isolated cells were highly immunopositive for both neurofilament and MAP-2 with well-organized neurites and somatodendritic localization. The presence of PDL with LN or FN on the PLGA films was essential for increased neural cell growth. Also, PLGA films coated with either PDL/LN or PDL/FN mixtures had higher neurite outgrowth and regular differentiation.

Animals↗

PubMed2005

Tissue-engineered semi-microporous segmented polyetherurethane vascular prostheses.

We investigated the biocompatibility of semi-microporous segmented polyetherurethane (SPEU) that was coated with human microvascular endothelial cells. Three types of prosthesis were examined: (1) non-porous (control), (2) SPEU without a collagen coating (PNC) and (3) collagen-coated SPEU (PC). The attachment and proliferation of endothelial cells on SPEU (PNC and PC prostheses) was twice as great as in the control prostheses and endothelial cell adhesion in the PC prostheses was 1.4-times greater than in the PNC prostheses. The degree of endothelial cell coverage in the control prostheses was significantly lower than in the PNC and PC prostheses (P < 0.05), and there was no significant difference between the PNC and PC prostheses in the degree of endothelial cell coverage. As regards the retention of endothelial cells under simulated blood-flow conditions, the PNC prostheses exhibited a greater decrease in endothelial cell coverage, as compared to the PC prostheses (P < 0.05). Similarly, the PNC prostheses exhibited less platelet adhesion than the PC prostheses (P < 0.05). In summary, the semi-microporous SPEU offered better surfaces to anchor and culture for endothelial cells, and had superior anti-coagulant properties, as compared to nonporous SPEU. The coating of SPEU with collagen influenced both the attachment of endothelial cells and blood coagulation on the SPEU.

Blood Coagulation↗

PubMed2004

Effects of green tea polyphenol on preservation of human saphenous vein.

The potential role of green tea polyphenol (GtPP) in preserving the human saphenous vein was investigated under physiological conditions. The vein segments were incubated for 1, 3, 5, 7 and 14 days, either after 4h of treatment with 1.0mg/ml GtPP or in the presence of GtPP at the same concentration. After incubation, the endothelial cell viability, endothelial nitric oxide synthase (eNOS) expression and the vein histology were evaluated. When the veins were not treated with GtPP, the viability of the endothelial cells was significantly reduced with the progress in the culture time, and none of the cells expressed eNOS after 5 days. Furthermore, severe histological changes and structural damage were observed in the non-treated veins. In contrast, incubating the veins after 4h of GtPP treatment significantly prevented these phenomena. The cellular viability of the GtPP-treated vein was approximately 64% after 7 days, and eNOS expression was maintained up to 40%, compared to that of the fresh vein. The histological observations showed that the vasculature was quite similar to that of the fresh vein. When incubated with GtPP, the vein could also be preserved for 1 week under physiological conditions retaining both its cellular viability (61%) and eNOS expression level (45%) and maintaining its venous structure without any morphological changes. These results demonstrate that GtPP treatment may be a useful method for preserving the HSV.

Blotting, Western↗

PubMed2003

A study of compatibility between cells and biopolymeric surfaces through quantitative measurements of adhesive forces.

The mechanism of cell adhesion to biomaterials or components of the extracellular matrix is an important topic in the field of tissue engineering and related biotechnological processes. Many factors affect cell adhesion, and many biochemical and biological studies have attempted to identify their roles in the adhesion mechanism. Systematic studies of this nature require quantification of the adhesive force of a cell to identify the effect of a specific factor. However, most studies of cell adhesive force have used qualitative approaches. We propose a new technique for quantifying the force by which cells adhere to various biomaterial surfaces, which utilizes the relationship between the deflection of a cantilever beam and the required force. A micropipette was used as the cantilever beam. This technique was used to measure the attachment forces of chondrocytes seeded on three different biodegradable polymers commonly used in tissue engineering and medicine: poly epsilon-carprolactone (PCL), poly(L-lactide) (PLLA) and poly(lactic-co-glycolic acid) (PGLA, L/G = 75:25). The bond between the cells and the three polymers was evaluated using the quantified adhesive forces. The adhesive forces were also measured 8, 12, 24 h and 5 days after seeding the chondrocytes on the polymer surfaces. Results of statistical analysis showed that the cells attached to the PLLA had the strongest average attachment force for up to 24 h after seeding (P < 0.05).

Animals↗

PubMed1977

Survival rates of patients with malignant melanoma of the skin.

This paper reports on cases of malignant melanoma of the skin diagnosed in Finland between 1963 and 1968. Sufficient data for estimating the survival was obtained in 691 cases. The ten-year relative survival rate for the entire series was 41% for males and 53% for females. This sex difference remained constant throughout the various divisions of the material. The ten-year relative survival rate of males with tumour in stage I was 52% and that of females 59%. The highest survival rate of stage I tumour in males was for the tumours of the lower extremities (77%) and in females for those in the head and neck (79%). The relative survival of patients with tumour of the trunk in stage I was lowest in both sexes (males 49%, females 45%). The ten-year relative survival rate of patients with a local recurrence was 33% in males and 27% in females. The relative ten-year survival rates of patients with superficial melanoma were 130% in males and 92% in females.

Female↗