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Biomedical subjects

In Kap Ko

Publications and source records attributed to In Kap Ko.

8 recordsLinked to original sources
PubMed2006

In vivo MR imaging of tissue-engineered human mesenchymal stem cells transplanted to mouse: a preliminary study.

Current progress integrating stem cell biology and tissue engineering techniques has been invaluable to clinical applications. Prior to the application of cellular transplantation technique to patients, we need to establish techniques that can monitor their tissue biodistribution non-invasively. In this study, we proposed an imaging modality using MRI to not only monitor implanted scaffold in vivo, but also to track transplanted cells and behavior around the implant. For this purpose, human bone marrow-derived mesenchymal stem cells (hMSCs) were labeled with superparamagnetic iron oxide (Feridex) and then labeled hMSCs were cultured in a gelatin sponge used as a scaffold to support cell growth and proliferation. Histological assessment and MTT assay showed that cell labeling with MR contrast agent did not harm cell viability. Also, Feridex-labeled hMSCs showed a significant decrease in T2 signal intensity, even within the gelatin sponge in vitro. After implanting the sponge/cell complex in vivo, we could visualize cellular behavior around the implant over time using a noninvasive MRI modality and this finding was correlated with histological study, which illustrates the potential of a new approach proposed here for in vivo monitoring of implanted cell-based tissue-engineered product.

Animals↗
PubMed2005

Parallel analysis of multiple surface markers expressed on rat neural stem cells using antibody microarrays.

Neural stem cells are the attractive cell source for functional regeneration of damaged central nervous tissues by means of cell transplantation or in situ induction of differentiated neural cells. Such stem cell therapies require the prospective identification and isolation of neural stem cells. However they are difficult due to limited information on surface markers. This study aimed at developing an antibody microarray that permits parallel analysis of multiple surface antigens expressed on neural stem cells present in a neurosphere-forming cell population. A microarray was prepared by micro-spotting antibodies directed to surface antigens and ligands for membrane-associated receptors onto the patterned monolayer of alkanethiols self-assembled on a gold-evaporated glass plate. Neurosphere-forming cells were subjected to a cell-binding assay on the microarray followed by immunofluorescent staining of nestin, an intracellular marker of neural stem cells. It was demonstrated that such a cell based assay facilitated to examine the specificity of surface antigens for nestin-positive neural stem cells. Furthermore, the microarray could also be used to assess proliferation capability of cells bound to individual spots. These results suggest that the microarray-based strategy will provide a useful tool for the parallel analysis of surface markers expressed on a specific cell type in a heterogeneous population.

Animals↗
PubMed2005

Preparation and properties of ProNectin F-coated biodegradable hollow fibers.

ProNectin F-coated biodegradable hollow fibers were newly prepared and their cytocompatibility was evaluated in vitro. Although the coating efficiency onto poly(L-lactic acid) (PLLA) and poly(lactide-co-caprolactone) [p(LA/CL)] matrices was similar, the cell adhesion properties were greatly affected by the nature of the polymer substrate. ProNectin F-coated PLLA showed about seven times higher cytocompatibility than ProNectin F-coated p(LA/CL). The single-extruded melt spinning method and the core-sheath bicomponent melt spinning method were employed to prepare PLLA hollow fibers. The effect of the spinning conditions, such as the melt draw ratio, spinneret temperature, and take-up speed, on the diameter and wall thickness of the spun fibers was studied in detail. For single-extruded melt spinning, a segmented type of spinneret was used, and the effect of the flow rate of nitrogen, which was confined in the hollow part of fibers, was studied. X-ray photographs of the drawn hollow fibers, clarified the significant molecular orientation, which was much higher than that in drawn solid PLLA fiber under identical drawing conditions. The morphology and mechanical properties of hollow fibers demonstrated an increase in the tensile strength and a decrease in the thickness of the PLLA wall with increased nitrogen flow rates and melt draw ratios for single-extruded melt spinning. These results indicate the unique characteristics of ProNectin F-coated PLLA hollow fibers, which can be successfully utilized as a biodegradable substrate.

Absorbable Implants↗
PubMed2005

Antibody microarray for correlating cell phenotype with surface marker.

To correlate cell surface markers with the cell phenotype, an antibody microarray prepared by covalently immobilizing antibodies onto a cellulose membrane and subsequent immunocytochemical staining were employed. The direct binding assay of a lymphoblastic leukemia cell line on the microarray showed that the immobilized antibody served to capture cells expressing the specific antigen. The density of bound cells increased linearly with an increasing content of antigen-expressing cells in suspension. The method was further applied to the analysis of surface antigens expressed on neural stem cells. A binding assay was performed with neural cells obtained from the neurosphere culture of the rat fetal striatum on a microarray spotted with eight kinds of antibodies and four different proteins, followed by immunocytochemical staining of cells bound to the microarray using antibodies to the intracellular markers of immature (nestin and vimentin) and mature (beta-tubulin III and glial fibrillary acidic protein) neural cells. As a result, the phenotype of bound cells could be correlated to surface antigen expression, which illustrated the potential of the solid-phase cytometry developed here for the identification of surface markers.

Animals↗
PubMed2005

A thin carboxymethyl cellulose culture substrate for the cellulase-induced harvesting of an endothelial cell sheet.

Engineered tissues constructed with two-dimensionally organized cells provide promising parts for reconstructing damaged tissues. Here we propose a new method for fabricating a 2D sheet made of an endothelial cell monolayer. First a culture substrate was prepared by treating the glass surface with an amine-terminated organosilicon derivative, followed by the covalent attachment of a thin carboxymethyl cellulose (CMC) layer. Fibronectin was immobilized onto the CMC-coated surface to promote cell adhesion. These surfaces were characterized step by step by means of contact angle measurement and X-ray photoelectron spectroscopy. Porcine aortic endothelial cells adhered to the culture substrate and consequently formed a confluent monolayer. When the substrate-cell composite was immersed in a cellulase solution, a cell sheet was spontaneously detached from the substrate due to enzymatic digestion of the CMC layer. The cell-cell connections were well preserved in the cell sheet, even after detachment from the substrate, most likely due to the fact that cellulase is harmless to mammalian cells. The cell sheet could be transferred to other culture dish with the aid of a hydrophilic membrane support, retaining the proliferation activity of the cells. The results obtained in this study demonstrate that cellulase treatment of the CMC layer is a rational and efficient method for obtaining a 2D cell sheet.

Animals↗
PubMed2005

Functional evaluation of bioartificial liver using RT-PCR.

In order to evaluate functions of a bioartificial liver (BAL), containing porcine hepatocytes in a hollow fiber cartridge, some chemical loading tests have been employed. However the kinds of functions that can be evaluated by chemical loading tests are limited. We desire versatile methods to estimate various BAL functions. The purpose of this report is to propose a method using the reverse transcription polymerase chain reaction (RT-PCR) for functional evaluation of a BAL. In vitro perfusion culture of a BAL cartridge was carried out using 20% of human whole blood. At pre-determined periods of perfusion culture, hepatocytes were taken from the cartridge and mRNA was extracted from the hepatocytes. The mRNA expression levels of albumin and cytochrome P450 (CYP3A29) were determined by RT-PCR method. In order to quasi-quantitatively determine the time courses of mRNA expression levels during the perfusion culture, PCR of target DNA was carried out by co-amplification with its competitor DNA that was constructed by means of the partial deletion of target DNA. The results showed that the amounts of both albumin and cytochrome P450 mRNA rapidly decreased during the initial few days' perfusion culture and remained at a constant level for the following week. This fact corresponded with the analysis of lidocaine metabolic functions via pharmacokinetics in our previous study. Additionally, the RT-PCR is so sensitive that we can measure much more minute quantity of various proteins. Consequently, this method is useful for comprehensive evaluation of BAL functions.

Albumins↗
PubMedDate not supplied

Bioartificial liver with whole blood perfusion.

In our series of studies, we have made an effort to develop a bioartificial liver (BAL) system through which whole blood can be perfused as in hemodialysis therapy. In this study, BAL cartridges containing porcine hepatocytes were prepared and perfused in an extracapillary space with human whole blood in vitro. Lidocaine loading tests were performed to evaluate the detoxification ability of the BAL. The clearance value of lidocaine decreased during the initial 6 hours to about 50% of the initial value. After that, it was almost stable until 48 hours. After 48 hours perfusion, thin sections of the hollow fibers containing hepatocytes were prepared and stained with hematoxylin-eosin and immunohistochemically stained for membrane attack complex (MAC). The porcine hepatocytes formed aggregates in the hollow fibers, nuclei in the cells were observed clearly, and MAC was not seen on the porcine hepatocyte aggregation. A hollow fiber that can reject 90% of molecules with molecular weight of 50 kDa effectively protects porcine hepatocytes from humoral immunity. The in vivo assessment of the BAL cartridge was performed using a canine model for 24 hours. No significant hemolysis or thrombus that affected the BAL system and the canine were observed. These results suggest that our BAL system is a promising liver assist device through which patients' whole blood can be perfused.

Animals↗