• Biomedical Science Letters
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• v.30 no.3
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• pp.123-130
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• 2024

Mesenchymal stem cells (MSCs) hold great promise as a source of stem cells for therapy, but several limitations remain. We previously proposed that human embryonic stem cell-derived MSCs (hE-MSCs) expressing higher hepatocyte growth factor (HGF) levels were better alternatives, exhibiting greater expandability in vitro and greater therapeutic capacity in vivo. In this study, we aimed to examine the regulation of OCT4 expression in stem cells and to elucidate its underlying mechanism of transcriptional regulation of OCT4. We detected higher expression of OCT4, a stemness-associated gene in hE-MSCs than in human bone marrow-derived MSCs (hBM-MSCs). To determine the underlying regulatory mechanism of OCT4 expression in human MSCs (hMSCs), ELISA was performed using cell culture supernatants of hMSCs. Unlike fibroblast growth factor 2 or vascular endothelial growth factor, HGF was strongly expressed in hE-MSCs, also HGF treatment significantly increased OCT4 expression in hBM-MSC. Moreover, senescence-associated heterochromatin foci were decreased in HGF-treated hBM-MSCs compared with those in the HGF non-treated group. HGF increased Rb phosphorylation, and we confirmed the increased binding of E2F1 to the OCT4 promoter region at -233 from the transcription start point in the presence of HGF. Taken together, these results suggest that HGF-mediated regulation of OCT4 via E2F1 can help enhance the lifespan of hBM-MSCs during in vitro expansion.

• BMB Reports
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• v.51 no.5
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• pp.242-248
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• 2018

Induced pluripotent stem cells (iPSCs) show great promise for replacing current stem cell therapies in the field of regenerative medicine. However, the original method for cellular reprogramming, involving four exogenous transcription factors, is characterized by low efficiency. Here, we focused on using epigenetic modifications to enhance the reprogramming efficiency. We hypothesized that there would be a new reprogramming factor involved in DNA demethylation, acting on the promoters of pluripotency-related genes. We screened proteins that bind to the methylated promoter of Oct4 and identified Zinc finger protein 127 (Zfp127), the functions of which have not yet been identified. We found that Zfp127 binds to the Oct4 promoter. Overexpression of Zfp127 in fibroblasts induced demethylation of the Oct4 promoter, thus enhancing Oct4 promoter activity and gene expression. These results demonstrate that Zfp127 is a novel regulator of Oct4, and may become a potent target to improve cellular reprogramming.

• Current Optics and Photonics
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• v.4 no.4
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• pp.330-335
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• 2020

We have investigated optimization of the working distance (WD) for a highly miniaturized imaging probe for endoscopic optical coherence tomography (OCT). The WD is the axial distance from the distal end of the imaging probe to its beam focus, which is demanded for dimensional margins of protective structures, operational safety, or full utilization of the axial imaging range of OCT. With an objective lens smaller than a few hundred micrometers in diameter, a micro-optic imaging probe naturally exhibits a very short WD due to the down-scaled optical structure. For a maximized WD careful design is required with the optical aperture of the objective lens optimally filled by the incident beam. The diffraction-involved effect was taken into account in our analysis of the apertured beam. In this study, we developed a simple design formula on the maximum achievable WD based on our diffraction simulation. It was found that the maximum WD is proportional to the aperture size squared. In experiment, we designed and fabricated very compact OCT probes with long WDs. Our 165-㎛-thick fiber-optic probes provided WDs of 3 mm or longer w ith reasonable OCT imaging performance.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.4
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• pp.364-370
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• 2006

Optical coherence tomography (OCT) is high resolution medical imaging system which is obtaining image inside biological objects with non-destructive method. OCT system is based on Michelson interferometer with a reciprocating mirror in the reference arm and a biological object in the sample arm. The obtained OCT image suffers from a granular or mottled image, called speckle. Speckle is caused by random interferences between reflected coherence waves. In this paper, we propose effective speckle reduction method that uses wavelet transform. With wavelet domain image, sub-windowing and thresholding are performed. Finally, speckle reduction experiments for Misgurnus mizolepis skin and rat eye images are shown.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.4
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• pp.639-642
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• 2012

Optical coherence tomography(OCT) can provide real-time and non-invasive subsurface imaging with ultra-high resolution of micrometer scale. However, conventional OCT systems generally have a limited imaging depth range within a depth of only 1-2 mm. To overcome the limitation, we have proposed an active surface tracking algorithm used in common-path Fourier-domain OCT system in order to extend the imaging depth range. The surface tracking algorithm based on the threshold and Savitzky-Golay filter of A-scan data was applied to real-time tracking. The algorithm has controlled a moving stage according to the sample's surface variance in real time. An OCT image obtained by the algorithm clearly show an extended imaging depth range. Consequently, the proposed algorithm demonstrated the potential for improving the conventional OCT systems with limitary depth range.

• Journal of dental hygiene science
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• v.16 no.4
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• pp.257-262
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• 2016

The purpose of this study was to assess the correlation between integrated mineral loss (volume % mineral${\times}{\mu}m$, ${\Delta}Z_{TMR}$) determined using transverse microradiography (TMR) and integrated reflectivity ($dB{\times}{\mu}m$, ${\Delta}R_{OCT}$) determined using optical coherence tomography (OCT) for detecting early dental caries with lesion depth more than $200{\mu}m$. Sixty tooth specimens were made from sound bovine teeth. They were immersed in a demineralized solution for 20, 30, and 40 days. The ${\Delta}R_{OCT}$ was obtained from the cross-sectional OCT image. The ${\Delta}Z_{TMR}$ was obtained from the TMR image. The correlation between ${\Delta}R_{OCT}$ and ${\Delta}Z_{TMR}$ was examined using Pearson correlation. The Bland-Altman plot was constructed using the ${\Delta}R_{OCT}$ and ${\Delta}Z_{TMR}$ values. A significant correlation between ${\Delta}R_{OCT}$ and ${\Delta}Z_{TMR}$ was confirmed (r=0.491, p=0.003). Moreover, most of the difference between ${\Delta}R_{OCT}$ and ${\Delta}Z_{TMR}$ was included in the error section of the Bland-Altman plot. Therefore, OCT could be used as a substitute for TMR when analyzing mineral loss in early dental caries.

• Korean Journal of Animal Reproduction
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• v.26 no.4
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• pp.329-338
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• 2002

This study was carried out to investigate the developmental rates of embryo reconstructed with different cell type and to estimate correlation of transcriptional level of octamer-binding transcription factor 4 (Oct4) and fibroblast growth factor 4 (FCF4) gene on peri-implantation stage embryos. Donor cells were transferred into perivitelline space of enucleated oocytes. The karyoplast-cytoplast couplets were accom- plished by cell to cell fusion and activated with ionomycin and 6-dimethylaminopurine. Reconstructed embryos were co-cultured with bovine oviduct epithelial cells in CR 1 aa medium. There is no difference in blastocyst formation rate following nuclear transfer UT) with fetal fibroblast cell (16/50; 32.0%), cumulus cell (16/49; 32.6%) and ear cell (17/52; 32.6%). The expression level of Oct4 and FCF4 in peri-implantation bovine embryo derived from in vitro fertilization (IVF) and NT were determined by reverse-transcription polymerase chain reaction (RT-PCR) technique. In peri-implantation of IVF result in a transient increased of FCF4 paralleled by an increased expression of Oct4. However, Oct4 gene was highly expressed in hatching blastocysts derived from NT compared to IVF. Also, FGF4 expression level in hatching blastocysts and outgrowth stage derived from NT was lower than that of IVF. In conclusion, it is suggested that the different transcription patterns observed in nuclear transfer embryos may lead to a lower rate of embryo development, implantation and pregnancy.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2640-2644
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• 2013

The all-hydrocarbon i,i+4 stapling system using an oct-4-enyl crosslink is one of the most widely employed chemical tools to stabilize an ${\alpha}$-helical conformation of a short peptide. This crosslinking system has greatly extended our ability to modulate intracellular protein-macromolecule interactions. The helix-inducing property of the i,i+4 staple has shown to be highly dependent on the length and the stereochemistry of the oct-4-enyl crosslink. Here we show that changing the double bond position within the i,i+4 staple has a considerable impact not only on the formation of the crosslink but also on ${\alpha}$-helix induction. The data further increases the understanding of the structure-activity relationships of this valuable chemical tool.

• Journal of Animal Reproduction and Biotechnology
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• v.36 no.4
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• pp.175-182
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• 2021

Pluripotent stem cells could self-renew and differentiate into various cells. In particular, porcine pluripotent stem cells are useful for preclinical therapy, transgenic animals, and agricultural usage. These stem cells have naïve and primed pluripotent states. Naïve pluripotent stem cells represented by mouse embryonic stem cells form chimeras after blastocyst injection. Primed pluripotent stem cells represented by mouse epiblast stem cells and human embryonic stem cells. They could not produce chimeras after blastocyst injection. Populations of embryonic stem cells are not homogenous; therefore, reporter systems are used to clarify the status of stem cells and to isolate the cells. For this reason, studies of the OCT4 reporter system have been conducted for decades. This review will discuss the naïve and primed pluripotent states and recent progress in the development of porcine OCT4 reporter systems.

• YAKHAK HOEJI
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• v.37 no.2
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• pp.136-142
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• 1993

To a suspension of 1-cyclopropyl-6,8-difluoro-1,4-dihydro-7-{3,7-diazabicyclo[3.3.0]oct-1(5)-en-3-yl}-4-oxo-3-quinoline carboxylic acid(C1) in sodium hydroxide solution and water is added dropwise with stirring carbon disulfide. [6R-[6$\alpha$, 7$\beta$(Z)]]-7-[[[2-Amino-4-thiazoly)methoxyimino]-acetyl]amino]-3-[[[[7-( 3-carboxy-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxo-7-guinolonyl)-3,7-diazabicyclo[3.3.0]oct-1(5)-en-3-yl]thioxomethyl]thio]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-2-carboxylic acid (DACD) was synthesized from 1-cyclopropyl-6,8-difluoro-1,4-dihydro-7-[7-(mercapto) thioxomethyl-[3,7-dia zabicyclo[3.3.0]oct-1(5)-en-3-yl}]-4-oxo-3-quinoline carboxylic acid disodium salt(C2) and cefotaxime. The invitro activity of novel dual-action cephalosporin, DACD, was compared with the in vitro activities of CENO(cefotaxime 3'-norfloxacin dithiocarbamate), cefotaxime, and norfloxacin against a variety of bacterial species. In vitro activity of DACD was superior to that of norfloxacin against Streptococcus pyogenes. Against Gram-positive and Gram-negative bacteria, its activity was almost equal to that of CENO.