Publications by authors named "Yohan Kim"

103 Publications

Fast super-resolution ultrasound microvessel imaging using spatiotemporal data with deep fully convolutional neural network.

Phys Med Biol 2021 Mar 2. Epub 2021 Mar 2.

Department of Radiology, Mayo Clinic, Rochester, UNITED STATES.

Ultrasound localization microscopy (ULM) has been proposed to image microvasculature beyond the ultrasound diffraction limit. Although ULM can attain microvascular images with a sub-diffraction resolution, long data acquisition time and processing time are the critical limitations. Deep learning-based ULM (deep-ULM) has been proposed to mitigate these limitations. However, microbubble (MB) localization used in deep-ULMs is currently based on spatial information without the use of temporal information. The highly spatiotemporally coherent MB signals provide a strong feature that can be used to differentiate MB signals from background artifacts. In this study, a deep neural network was employed and trained with spatiotemporal ultrasound datasets to better identify the MB signals by leveraging both the spatial and temporal information of the MB signals. Training, validation and testing datasets were acquired from MB suspension to mimic the realistic intensity-varying and moving MB signals. The performance of the proposed network was first demonstrated in the chicken embryo chorioallantoic membrane dataset with an optical microscopic image as the reference standard. Substantial improvement in spatial resolution was shown for the reconstructed super-resolved images compared with power Doppler images. The full-width-half-maximum (FWHM) of a microvessel was improved from 133 µm to 35 µm, which is smaller than the ultrasound wavelength (73 µm). The proposed method was further tested in an in vivo human liver data. Results showed the reconstructed super-resolved images could resolve a microvessel of nearly 170 µm (FWHM). Adjacent microvessels with a distance of 670 µm, which cannot be resolved with power Doppler imaging, can be well-separated with the proposed method. Improved contrast ratios using the proposed method were shown compared with that of the conventional deep-ULM method. Additionally, the processing time to reconstruct a high-resolution ultrasound frame with an image size of 1024 × 512 pixels was around 16 ms, comparable to state-of-the-art deep-ULMs.
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http://dx.doi.org/10.1088/1361-6560/abeb31DOI Listing
March 2021

Generation of Hepatic Progenitor Cells from the Primary Hepatocytes of Nonhuman Primates Using Small Molecules.

Tissue Eng Regen Med 2021 Apr 16;18(2):305-313. Epub 2021 Feb 16.

Department of Obstetrics and Gynecology, Hanyang University College of Medicine, Seoul, 04763, Republic of Korea.

Background: Since primates have more biological similarities to humans than do other animals, they are a valuable resource in various field of research, including biomedicine, regenerative medicine, and drug discovery. However, there remain limitations to maintenance and expansion of primary hepatocytes derived from nonhuman primates. To overcome these limitations, we developed a novel culture system for primate cells.

Methods: Primary hepatocytes from Macaca fascicularis (mf-PHs) were isolated from hepatectomized liver. To generate chemically derived hepatic progenitor cells (mf-CdHs), mf-PHs were cultured with reprogramming medium containing A83-01, CHIR99021, and hepatocyte growth factor (HGF). The bi-potent differentiation capacity of mf-CdHs into hepatocytes and biliary epithelial cells was confirmed by treatment with hepatic differentiation medium (HDM) and cholangiocytic differentiation medium (CDM), respectively.

Results: mf-PHs cultured with reprogramming medium showed rapid proliferation capacity in vitro and expressed progenitor-specific markers. Moreover, when cultured in HDM, these progenitor cells stably differentiated into hepatocyte-like cells expressing the mature hepatic markers. On the other hand, when cultured in CDM, the differentiated biliary epithelial cells expressed mature cholangiocyte characteristics.

Conclusion: The results of the present study demonstrate that we successfully induced the formation of hepatic progenitor cells from mf-PHs by culturing them with a combination of small molecules, including growth factors. These results offer a means of expanding nonhuman primate hepatocytes without genetic manipulation for cellular resource, preclinical applications and regenerative medicine for the liver.
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http://dx.doi.org/10.1007/s13770-020-00327-8DOI Listing
April 2021

Mitovesicles are a novel population of extracellular vesicles of mitochondrial origin altered in Down syndrome.

Sci Adv 2021 Feb 12;7(7). Epub 2021 Feb 12.

Center for Dementia Research, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA.

Mitochondrial dysfunction is an established hallmark of aging and neurodegenerative disorders such as Down syndrome (DS) and Alzheimer's disease (AD). Using a high-resolution density gradient separation of extracellular vesicles (EVs) isolated from murine and human DS and diploid control brains, we identify and characterize a previously unknown population of double-membraned EVs containing multiple mitochondrial proteins distinct from previously described EV subtypes, including microvesicles and exosomes. We term these newly identified mitochondria-derived EVs "mitovesicles." We demonstrate that brain-derived mitovesicles contain a specific subset of mitochondrial constituents and that their levels and cargo are altered during pathophysiological processes where mitochondrial dysfunction occurs, including in DS. The development of a method for the selective isolation of mitovesicles paves the way for the characterization in vivo of biological processes connecting EV biology and mitochondria dynamics and for innovative therapeutic and diagnostic strategies.
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http://dx.doi.org/10.1126/sciadv.abe5085DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7880603PMC
February 2021

Improved Ultrasound Microvessel Imaging Using Deconvolution with Total Variation Regularization.

Ultrasound Med Biol 2021 Apr 16;47(4):1089-1098. Epub 2021 Jan 16.

Department of Radiology, Mayo Clinic College of Medicine and Science, Rochester, Minnesota, USA. Electronic address:

Singular value decomposition-based clutter filters can robustly reject tissue clutter, allowing for detection of slow blood flow in imaging microvasculature. However, to identify microvessels, high ultrasound frequency must be used to increase the spatial resolution at the expense of shorter depth of penetration. Deconvolution using Tikhonov regularization is an imaging processing method widely used to improve spatial resolution. The ringing artifact of Tikhonov regularization, though, can produce image artifacts such as non-existent microvessels, which degrade image quality. Therefore, a deconvolution method using total variation is proposed in this study to improve spatial resolution and mitigate the ringing artifact. Performance of the proposed method was evaluated using chicken embryo brain, ex ovo chicken embryo chorioallantoic membrane and tumor data. Results revealed that the reconstructed power Doppler (PD) images are substantially improved in spatial resolution compared with original PD images: the full width half-maximum (FWHM) of the cross-sectional profile of a microvessel was improved from 132 to 83 µm. Two neighboring microvessels that were 154 µm apart were better separated using the proposed method than conventional PD imaging. Additionally, 223 FWHMs measured from the cross-sectional profiles of 223 vessels were used to determine the improvement in FWHM with the proposed method statistically. The mean ± standard deviation of the FWHM without and with the proposed method was 233.19 ± 85.08 and 172.31 ± 75.11 μm, respectively; the maximum FWHM without and with the proposed method was 693.01 and 668.69 μm; and the minimum FWHM without and with the proposed method was 73.92 and 45.74 μm. There were statistically significant differences between FWHMs with and without the proposed method according to the rank-sum test, p < 0.0001. The contrast-to-noise ratio improved from 1.06 to 4.03 dB with use of the proposed method. We also compared the proposed method with Tikhonov regularization using ex ovo chicken embryo chorioallantoic membrane data. We found that the proposed method outperformed Tikhonov regularization as false microvessels appeared using the Tikhonov regularization but not with the proposed method. These results indicate that the proposed method is capable of providing more robust PD images with higher spatial resolution and higher contrast-to-noise ratio.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2020.12.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7908678PMC
April 2021

Leukemic extracellular vesicles induce chimeric antigen receptor T cell dysfunction in chronic lymphocytic leukemia.

Mol Ther 2021 04 1;29(4):1529-1540. Epub 2021 Jan 1.

T Cell Engineering, Mayo Clinic, Rochester, MN, USA; Division of Hematology, Mayo Clinic, Rochester, MN 55905, USA; Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, USA; Department of Molecular Medicine, Mayo Clinic, Rochester, MN, USA; Department of Immunology, Mayo Clinic, Rochester, MN, USA. Electronic address:

Chimeric antigen receptor (CAR) T cell therapy has yielded unprecedented outcomes in some patients with hematological malignancies; however, inhibition by the tumor microenvironment has prevented the broader success of CART cell therapy. We used chronic lymphocytic leukemia (CLL) as a model to investigate the interactions between the tumor microenvironment and CART cells. CLL is characterized by an immunosuppressive microenvironment, an abundance of systemic extracellular vesicles (EVs), and a relatively lower durable response rate to CART cell therapy. In this study, we characterized plasma EVs from untreated CLL patients and identified their leukemic cell origin. CLL-derived EVs were able to induce a state of CART cell dysfunction characterized by phenotypical, functional, and transcriptional changes of exhaustion. We demonstrate that, specifically, PD-L1 CLL-derived EVs induce CART cell exhaustion. In conclusion, we identify an important mechanism of CART cell exhaustion induced by EVs from CLL patients.
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http://dx.doi.org/10.1016/j.ymthe.2020.12.033DOI Listing
April 2021

Structural Characterization of Glycerophosphorylated and Succinylated Cyclic β-(1→2)-d-Glucan Produced by 1021.

Polymers (Basel) 2020 Sep 12;12(9). Epub 2020 Sep 12.

Department of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul 05029, Korea.

produces different types of surface polysaccharides. Among them, cyclic β-(1→2)-d-glucan is located in the periplasmic space of rhizobia and plays an important role in the adaptation of bacteria to osmotic adaptation. Cyclic β-(1→2)-d-glucan (CG), synthesized from 1021, has a neutral and anionic form. In the present study, we characterized the exact chemical structures of anionic CG after purification using size exclusion s (Bio-Gel P-6 and P-2) chromatography, and DEAE-Sephadex anion exchange chromatography. The exact structure of each isolated anionic CG was characterized using various analytical methods such as nuclear magnetic resonance (NMR), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and matrix associated laser desorption ionization-time of Flight (MALDI-TOF) mass spectrometry. The precise chemical structures of novel anionic CG molecules were elucidated by various NMR spectroscopic analyses, including H, C, P, and 2D HSQC NMR spectroscopy. As a result, we discovered that anionic CG molecules have either glycerophosphoryl or succinyl residues at C6 positions of a neutral CG. In addition, the results of MALDI-TOF mass spectrometric analysis confirmed that there are two types of patterns for anionic CG peaks, where one type of peak was the succinylated CG (SCG) and the other was glycerophospholated CG (GCG). In addition, it was revealed that each anionic CG has one to four substituents of the succinyl group of SCG and glycerophosphoryl group of GCG, respectively. Anionic CG could have potential as a cyclic polysaccharide for drug delivery systems and a chiral separator based on the complexation with basic target molecules.
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http://dx.doi.org/10.3390/polym12092073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7569799PMC
September 2020

Extracellular vesicles: where the amyloid precursor protein carboxyl-terminal fragments accumulate and amyloid-β oligomerizes.

FASEB J 2020 09 9;34(9):12922-12931. Epub 2020 Aug 9.

Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, NY, USA.

Pleiotropic roles are proposed for brain extracellular vesicles (EVs) in the development of Alzheimer's disease (AD). Our previous studies have suggested a beneficial role for EVs in AD, where the endosomal system in vulnerable neurons is compromised, contributing to the removal of accumulated material from neurons. However, the involvement of EVs in propagating AD amyloidosis throughout the brain has been considered because the amyloid-β precursor protein (APP), APP metabolites, and key APP cleaving enzymes were identified in association with EVs. Here, we undertook to determine whether the secretase machinery is actively processing APP in EVs isolated from the brains of wild-type and APP overexpressing Tg2576 mice. We found that full-length APP is cleaved in EVs incubated in the absence of cells. The resulting metabolites, both α- and β-APP carboxyl-terminal fragments and APP intracellular domain accumulate in EVs over time and amyloid-β dimerizes. Thus, EVs contribute to the removal from neurons and transport of APP-derived neurotoxic peptides. While this is potentially a venue for propagation of the pathology throughout the brain, it may contribute to efficient removal of neurotoxic peptides from the brain.
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http://dx.doi.org/10.1096/fj.202000823RDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496786PMC
September 2020

Azobenzene-grafted carboxymethyl cellulose hydrogels with photo-switchable, reduction-responsive and self-healing properties for a controlled drug release system.

Int J Biol Macromol 2020 Nov 10;163:824-832. Epub 2020 Jul 10.

Department of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, South Korea; Department of Systems Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, South Korea. Electronic address:

In this study, multifunctional hydrogels containing host-guest complex formation between azobenzene-grafted carboxymethyl cellulose (CMC-Azo) and β-cyclodextrin (CD) dimers connected by disulfide bonds with agarose for structural support were prepared. The obtained hydrogels exhibited self-healing properties by host-guest complexation as well as gel-sol phase transition in response to ultraviolet (UV) light and reducing agents. Photo-switchable properties of the hydrogels depend on changes in the complex formation of CD-dimers through the trans(450 nm) to cis(365 nm) photo-isomerization of azobenzene. The tensile and strain sweep tests confirmed that the hydrogel's self-healing ability was 79.44% and 81.59%, respectively. In addition, drug release from the hydrogels was controlled to accelerate to 80% in 3 h using UV light or reducing agent. Since the suggested photo-switchable, reduction-responsive, and self-healable hydrogels are non-cytotoxic, they can be potentially applied as biomedical materials in the development of hydrogel-based drug release systems.
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http://dx.doi.org/10.1016/j.ijbiomac.2020.07.071DOI Listing
November 2020

Unveiling 79-Year-Old Ixene and Its BN-Doped Derivative.

Angew Chem Int Ed Engl 2020 Aug 9;59(35):14891-14895. Epub 2020 Jun 9.

Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan, 44919, Republic of Korea.

Polycyclic aromatic hydrocarbons (PAHs) are key components of organic electronics. The electronic properties of these carbon-rich materials can be controlled through doping with heteroatoms such as B and N, however, few convenient syntheses of BN-doped PAHs have been reported. Described herein is the rationally designed, two-step syntheses of previously unknown ixene and BN-doped ixene (B N -ixene), and their characterizations. Compared to ixene, B N -ixene absorbs longer-wavelength light and has a smaller electrochemical energy gap. In addition to its single-crystal structure, scanning tunneling microscopy revealed that B N -ixene adopts a nonplanar geometry on a Au(111) surface. The experimentally obtained electronic structure of B N -ixene and the effect of BN-doping were confirmed by DFT calculations. This synthesis enables the efficient and convenient construction of BN-doped systems with extended π-conjugation that can be used in versatile organic electronics applications.
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http://dx.doi.org/10.1002/anie.202004049DOI Listing
August 2020

Preparation of Succinoglycan Hydrogel Coordinated With Fe Ions for Controlled Drug Delivery.

Polymers (Basel) 2020 Apr 22;12(4). Epub 2020 Apr 22.

Department of Systems Biotechnology & Dept. of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul 05029, Korea.

Hydrogel materials with a gel-sol conversion due to external environmental changes have potential applications in a wide range of fields, including controlled drug delivery. Succinoglycans are anionic extracellular polysaccharides produced by various bacteria, including species, which have diverse applications. In this study, the rheological analysis confirmed that succinoglycan produced by Rm 1021 binds weakly to various metal ions, including Fe cations, to maintain a sol form, and binds strongly to Fe cations to maintain a gel form. The Fe-coordinated succinoglycan (Fe-SG) hydrogel was analyzed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, circular dichroism (CD), and field-emission scanning electron microscopy (FE-SEM). Our results revealed that the Fe cations that coordinated with succinoglycan were converted to Fe by a reducing agent and visible light, promoting a gel-sol conversion. The Fe-SG hydrogel was then successfully used for controlled drug delivery based on gel-sol conversion in the presence of reducing agents and visible light. As succinoglycan is nontoxic, it is a potential material for controlled drug delivery.
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http://dx.doi.org/10.3390/polym12040977DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240483PMC
April 2020

In Vivo Confocal Imaging of Fluorescently Labeled Microbubbles: Implications for Ultrasound Localization Microscopy.

IEEE Trans Ultrason Ferroelectr Freq Control 2020 09 15;67(9):1811-1819. Epub 2020 Apr 15.

We report the time kinetics of fluorescently labeled microbubbles (MBs) in capillary-level microvasculature as measured via confocal microscopy and compare these results to ultrasound localization microscopy (ULM). The observed 19.4 ± 4.2 MBs per confocal field-of-view ( [Formula: see text]) are in excellent agreement with the expected count of 19.1 MBs per frame. The estimated time to fully perfuse this capillary network was 193 s, which corroborates the values reported in the literature. We then modeled the capillary network as an empirically determined discrete-time Markov chain with adjustable MB transition probabilities though individual capillaries. The Monte Carlo random walk simulations found perfusion times ranging from 24.5 s for unbiased Markov chains up to 182 s for heterogeneous flow distributions. This pilot study confirms a probability-derived explanation for the long acquisition times required for super-resolution ULM.
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http://dx.doi.org/10.1109/TUFFC.2020.2988159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7483886PMC
September 2020

Small-molecule-mediated reprogramming: a silver lining for regenerative medicine.

Exp Mol Med 2020 02 20;52(2):213-226. Epub 2020 Feb 20.

Department of Surgery, Hanyang University College of Medicine, Seoul, 04763, Korea.

Techniques for reprogramming somatic cells create new opportunities for drug screening, disease modeling, artificial organ development, and cell therapy. The development of reprogramming techniques has grown exponentially since the discovery of induced pluripotent stem cells (iPSCs) by the transduction of four factors (OCT3/4, SOX2, c-MYC, and KLF4) in mouse embryonic fibroblasts. Initial studies on iPSCs led to direct-conversion techniques using transcription factors expressed mainly in target cells. However, reprogramming transcription factors with a virus risks integrating viral DNA and can be complicated by oncogenes. To address these problems, many researchers are developing reprogramming methods that use clinically applicable small molecules and growth factors. This review summarizes research trends in reprogramming cells using small molecules and growth factors, including their modes of action.
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http://dx.doi.org/10.1038/s12276-020-0383-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7062739PMC
February 2020

Utilization of Water-Soluble Aminoethylamino-β-Cyclodextrin in the Pfitzinger Reaction-Catalyzed to the Synthesis of Diversely Functionalized Quinaldine.

Polymers (Basel) 2020 Feb 9;12(2). Epub 2020 Feb 9.

Department of Systems Biotechnology & Department of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul 05029, Korea.

In this study we describe the use of an aminoethylamino-β-cyclodextrin (AEA-β-CD) as a supramolecular homogeneous catalyst for the synthesis of a series of diversely substituted quinaldine derivatives which are medicinally important, via Pfitzinger reaction. This supramolecular catalyst exhibited remarkable catalytic activity with high substrate scope to achieve the synthetic targets in good to excellent yield, 69-92%. The structural and morphological properties of the synthesized AEA-β-CD were determined through MALDI-TOF mass spectrometry, NMR, FT-IR, and SEM analysis. Possible reaction mechanisms were determined through molecular host-guest complexation and proposed based on 2D NMR (ROESY) spectroscopy, FT-IR, FE-SEM, and DSC.
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http://dx.doi.org/10.3390/polym12020393DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7077625PMC
February 2020

Identification of Plasmodium falciparum circumsporozoite protein-specific CD8+ T cell epitopes in a malaria exposed population.

PLoS One 2020 10;15(2):e0228177. Epub 2020 Feb 10.

Malaria Department, Naval Medical Research Center, Silver Springs, MD, United States of America.

Background: Sterile protection against malaria, most likely mediated by parasite-specific CD8+ T cells, has been achieved by attenuated sporozoite vaccination of animals as well as malaria-naïve and malaria-exposed subjects. The circumsporozoite protein (CSP)-based vaccine, RTS,S, shows low efficacy partly due to limited CD8+ T cell induction, and inclusion of such epitopes could improve RTS,S. This study assessed 8-10mer CSP peptide epitopes, present in predicted or previously positive P. falciparum 3D7 CSP 15mer overlapping peptide pools, for their ability to induce CD8+ T cell IFN-γ responses in natural malaria-exposed subjects.

Methods: Cryopreserved PBMCs from nine HLA-typed subjects were stimulated with 23 8-10mer CSP peptides from the 3D7 parasite in IFN-ɣ ELISpot assays. The CD8+ T cell specificity of IFN-γ responses was confirmed in ELISpot assays using CD8+ T cell-enriched PBMC fractions after CD4+ cell depletion.

Results: Ten of 23 peptide epitopes elicited responses in whole PBMCs from five of the nine subjects. Four peptides tested positive in CD8+ T cell-enriched PBMCs from two previously positive responders and one new subject. All four immunodominant peptides are restricted by globally common HLA supertypes (A02, A03, B07) and mapped to regions of the CSP antigen with limited or no reported polymorphism. Association of these peptide-specific responses with anti-malarial protection remains to be confirmed.

Conclusions: The relatively conserved nature of the four identified epitopes and their binding to globally common HLA supertypes makes them good candidates for inclusion in potential multi-epitope malaria vaccines.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0228177PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7010280PMC
April 2020

Caveolin-1 Y14 phosphorylation suppresses tumor growth while promoting invasion.

Oncotarget 2019 Nov 19;10(62):6668-6677. Epub 2019 Nov 19.

Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada.

Caveolin-1 is a transmembrane protein with both tumor promoter and suppressor functions that remain poorly understood. Cav1 phosphorylation by Src kinase on tyrosine 14 is closely associated with focal adhesion dynamics and tumor cell migration, however the role of pCav1 in tumor progression remains poorly characterized. Herein, we expressed phosphomimetic Y14D, wild type, and non-phosphorylatable Y14F forms of Cav1 in MDA-MB-435 cancer cells. Expression of Cav1Y14D reduced cell proliferation and induced the TP53 tumor suppressor. Ectopic expression in MDA-MB-435 cells of Y14 phosphorylatable Cav1 was required for induction of TP53 in response to oxidative stress. Cav1Y14D promotes an apparent reversal of the Warburg effect and markedly inhibited tumor growth . However, Cav1 induced pseudopodial recruitment of glycolytic enzymes, and time-lapse intravital imaging showed increased invadopodia protrusion and extravasation into blood vessels for Cav1WT and Y14D but not for Y14F. Our results suggest that Cav1 Y14 phosphorylation levels play a role in the conflicting demands on metabolic resources associated with cancer cell proliferation versus motility.
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http://dx.doi.org/10.18632/oncotarget.27313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6877104PMC
November 2019

A pleiotropic role for exosomes loaded with the amyloid β precursor protein carboxyl-terminal fragments in the brain of Down syndrome patients.

Neurobiol Aging 2019 12 1;84:26-32. Epub 2019 Aug 1.

Center for Dementia Research, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA; Department of Psychiatry, NYU Langone Health, New York, NY, USA; Department of Biochemistry & Molecular Pharmacology, NYU Langone Health, New York, NY, USA; Neuroscience Institute, NYU Langone Health, New York, NY, USA.

Down syndrome (DS) is characterized by cognitive deficits throughout the life span and with the development of aging-dependent Alzheimer's type neuropathology, which is related to the triplication of the amyloid β precursor protein (APP) gene. A dysfunctional endosomal system in neurons is an early characteristic of DS and APP metabolites accumulate in endosomes in DS neurons. We have previously shown enhanced release of exosomes in the brain of DS patients and the mouse model of DS Ts[Rb(12.17)]2Cje (Ts2), and by DS fibroblasts, as compared with diploid controls. Here, we demonstrate that exosome-enriched extracellular vesicles (hereafter called EVs) isolated from DS and Ts2 brains, and from the culture media of human DS fibroblasts are enriched in APP carboxyl-terminal fragments (APP-CTFs) as compared with diploid controls. Moreover, APP-CTFs levels increase in an age-dependent manner in EVs isolated from the brain of Ts2 mice. The release of APP-CTFs-enriched exosomes may have a pathogenic role by transporting APP-CTFs into naïve neurons and propagating these neurotoxic metabolites, which are also a source of amyloid β, throughout the brain, but also provides a benefit to DS neurons by shedding APP-CTFs accumulated intracellularly.
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http://dx.doi.org/10.1016/j.neurobiolaging.2019.07.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6960325PMC
December 2019

Loss of tau and Fyn reduces compensatory effects of MAP2 for tau and reveals a Fyn-independent effect of tau on calcium.

J Neurosci Res 2019 11 26;97(11):1393-1413. Epub 2019 Aug 26.

Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa.

Microtubule-associated protein tau associates with Src family tyrosine kinase Fyn and is tyrosine phosphorylated by Fyn. The presence of tyrosine phosphorylated tau in AD and the involvement of Fyn in AD has drawn attention to the tau-Fyn complex. In this study, a tau-Fyn double knockout (DKO) mouse was generated to investigate the role of the complex. DKO mice resembled Fyn KO in novel object recognition and contextual fear conditioning tasks and resembled tau KO mice in the pole test and protection from pentylenetetrazole-induced seizures. In glutamate-induced Ca response, Fyn KO was decreased relative to WT and DKO had a greater reduction relative to Fyn KO, suggesting that tau may have a Fyn-independent role. Since tau KO resembled WT in its Ca response, we investigated whether microtubule-associated protein 2 (MAP2) served to compensate for tau, since the MAP2 level was increased in tau KO but decreased in DKO mice. We found that like tau, MAP2 increased Fyn activity. Moreover, tau KO neurons had increased density of dendritic MAP2-Fyn complexes relative to WT neurons. Therefore, we hypothesize that in the tau KO, the absence of tau would be compensated by MAP2, especially in the dendrites, where tau-Fyn complexes are of critical importance. In the DKO, decreased levels of MAP2 made compensation more difficult, thus revealing the effect of tau in the Ca response.
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http://dx.doi.org/10.1002/jnr.24517DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6850396PMC
November 2019

Neuroprotection mediated by cystatin C-loaded extracellular vesicles.

Sci Rep 2019 07 31;9(1):11104. Epub 2019 Jul 31.

Nathan S. Kline Institute, Orangeburg, NY, USA.

Cystatin C (CysC) is implicated in neuroprotection and repair in the nervous system in response to diverse neurotoxic conditions. In addition to being secreted from cells in a soluble form, CysC is released by cells in association with extracellular vesicles (EVs), including exosomes. We demonstrate that EVs containing CysC protect cultured cells from starvation-induced death. Moreover, while EVs secreted by CysC-deficient cells were not protective, EVs secreted by CysC-deficient cells treated with exogenous human CysC significantly enhanced the survival of the cells. CysC also plays a role in modulating the secretion of EVs, enhancing secretion of EVs by primary cortical neurons and primary cortical smooth muscle cells. Confirming these in vitro findings, higher EV levels were observed in the brain extracellular space of transgenic mice expressing human CysC as compared to littermate controls. Regulation of cell-secreted EV levels and content in the brain is likely to be essential to maintaining normal brain function. We propose that enhanced EV release could rescue the deleterious effects of dysfunction of the endosomal-lysosomal system in neurodegenerative disorders. Moreover, a higher level of CysC-loaded EVs released from cells in the central nervous system has important protective functions, representing a potential therapeutic tool for disorders of the central nervous system.
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http://dx.doi.org/10.1038/s41598-019-47524-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6668451PMC
July 2019

Cyclodextrin functionalized agarose gel with low gelling temperature for controlled drug delivery systems.

Carbohydr Polym 2019 Oct 20;222:115011. Epub 2019 Jun 20.

Department of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 05029, South Korea; Institute for Ubiquitous Information Technology and Applications (UBITA), Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul, 05029, South Korea. Electronic address:

Conventional agaroses with high gelling temperature are limited to apply to the field of drug delivery. In this study, β-cyclodextrin (βCD) functionalized agarose (CFA) with low gelling temperature was successfully prepared from ethylenediamine-functionalized agarose using mono-succinyl βCD. The gelling temperature of CFA dramatically decreased to 26.7 °C from 65 °C and the melting temperature declined from 95 °C to 66.1 °C. Upon drug loading, CFA can be used at 30 °C because of its low gelling temperature compared to agarose. CFA gel could be used both for bovine serum albumin as a full release, and for the doxorubicin (DOX) for sustained release, via inclusion complexation of βCD. Furthermore, cytotoxicity tests revealed that CFA was noncytotoxic. DOX in the CFA gel could retain the anti-cancer activity. Newly synthesized CFA with low gelling temperature offer a new means for the development of hydrogel-based delivery systems for a variety of therapeutic drugs.
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http://dx.doi.org/10.1016/j.carbpol.2019.115011DOI Listing
October 2019

Improved infrared spectroscopic discrimination between gall bladder (GB) polyps and GB cancer using component-descriptive spectral features of separated phases from bile.

Analyst 2019 Aug;144(16):4826-4834

Department of Chemistry and Research Institute for Convergence of Basic Science, Hanyang University, Seoul 04763, Republic of Korea.

This study demonstrates a unique strategy for enhancing infrared (IR) spectroscopic discrimination between gall bladder (GB) polyps and cancer. This strategy includes the separation of raw bile juice into three sections of organic, aqueous, and amphiphilic phases and a cooperative combination of all IR spectral features of each separated phase for the discrimination. Raw bile juice is viscous and complex in composition because it contains fatty acids, cholesterol, proteins, phospholipids, bilirubin, and other components; therefore, the acquisition of IR spectra providing more component-discernible information is fundamental for improving discrimination. For this purpose, raw bile juice was separated into an aqueous phase, mostly containing bile salts, an organic phase with isolated lipids, and an amphiphilic phase, mainly containing proteins. The subsequent IR spectra of each separated phase were mutually characteristic and complementary to each other. When all the IR spectral features were combined, the discrimination was improved compared to that using the spectra of raw bile juice with no separation. The cooperative integration of more component-specific spectra obtained from each separated phase enhanced the discrimination. In addition, the IR spectra of the major constituents in bile juice, such as bile acids, conjugated bile salts, lecithin, and cholesterol, were recorded to explain the IR features of each separated phase.
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http://dx.doi.org/10.1039/c9an00878kDOI Listing
August 2019

Adlayer-Free Large-Area Single Crystal Graphene Grown on a Cu(111) Foil.

Adv Mater 2019 Aug 2;31(35):e1903615. Epub 2019 Jul 2.

Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea.

To date, thousands of publications have reported chemical vapor deposition growth of "single layer" graphene, but none of them has described truly single layer graphene over large area because a fraction of the area has adlayers. It is found that the amount of subsurface carbon (leading to additional nuclei) in Cu foils directly correlates with the extent of adlayer growth. Annealing in hydrogen gas atmosphere depletes the subsurface carbon in the Cu foil. Adlayer-free single crystal and polycrystalline single layer graphene films are grown on Cu(111) and polycrystalline Cu foils containing no subsurface carbon, respectively. This single crystal graphene contains parallel, centimeter-long ≈100 nm wide "folds," separated by 20 to 50 µm, while folds (and wrinkles) are distributed quasi-randomly in the polycrystalline graphene film. High-performance field-effect transistors are readily fabricated in the large regions between adjacent parallel folds in the adlayer-free single crystal graphene film.
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http://dx.doi.org/10.1002/adma.201903615DOI Listing
August 2019

Tau interacts with SHP2 in neuronal systems and in Alzheimer's disease brains.

J Cell Sci 2019 07 15;132(14). Epub 2019 Jul 15.

Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA

Microtubule-associated protein tau, an integral component of neurofibrillary tangles, interacts with a variety of signaling molecules. Previously, our laboratory reported that nerve growth factor (NGF)-induced MAPK activation in a PC12-derived cell line was potentiated by tau, with phosphorylation at T231 being required. Therefore, we sought to identify a signaling molecule involved in the NGF-induced Ras-MAPK pathway that interacted with phospho-T231-tau. Here, we report that the protein tyrosine phosphatase SHP2 (also known as PTPN11) interacted with tau, with phospho-T231 significantly enhancing the interaction. By using proximity ligation assays, we found that endogenous tau-SHP2 complexes were present in neuronal cells, where the number of tau-SHP2 complexes significantly increased when the cells were treated with NGF, with phosphorylation at T231 being required for the increase. The interaction did not require microtubule association, and an association between tau and activated SHP2 was also found. Tau-SHP2 complexes were also found in both primary mouse hippocampal cultures and adult mouse brain. Finally, SHP2 levels were upregulated in samples from patients with mild and severe Alzheimer's disease (AD), and the level of tau-SHP2 complexes were increased in AD patient samples. These findings strongly suggest a role for the tau-SHP2 interaction in NGF-stimulated neuronal development and in AD.This article has an associated First Person interview with the first author of the paper.
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http://dx.doi.org/10.1242/jcs.229054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6679582PMC
July 2019

Reply to: "Role of HGF for reprogramming human liver progenitor cells: Non-essential but stimulative supplement".

J Hepatol 2019 08 13;71(2):439-440. Epub 2019 May 13.

Department of Surgery, Hanyang University College of Medicine, Seoul 04763, Republic of Korea; HY Indang Center of Regenerative Medicine and Stem Cell Research, Hanyang University, Seoul 04763, Republic of Korea. Electronic address:

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http://dx.doi.org/10.1016/j.jhep.2019.04.004DOI Listing
August 2019

Efficient Adsorption on Benzoyl and Stearoyl Cellulose to Remove Phenanthrene and Pyrene from Aqueous Solution.

Polymers (Basel) 2018 Sep 19;10(9). Epub 2018 Sep 19.

Department of Systems Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul 05029, Korea.

Benzoyl and stearoyl acid grafted cellulose were synthesized by a simple chemical grafting method. Using these as chemical adsorbents, polycyclic aromatic hydrocarbons (PAHs), like pyrene and phenanthrene, were effectively removed from aqueous solution. The structural and morphological properties of the synthesized adsorbents were determined through X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared (FT-IR), FE-SEM, and NMR analyses. Through this method, it was confirmed that benzoyl and stearoyl acid were successfully grafted onto the surface of cellulose. The 5 mg of stearoyl grafted cellulose (St⁻Cell) remove 96.94% pyrene and 97.61% phenanthrene as compared to unmodified cellulose, which adsorbed 1.46% pyrene and 2.99% phenanthrene from 0.08 ppm pyrene and 0.8 ppm phenanthrene aqueous solution, suggesting that those results show a very efficient adsorption performance as compared to the unmodified cellulose.
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http://dx.doi.org/10.3390/polym10091042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6403814PMC
September 2018

Solubility Enhancement of Atrazine by Complexation with Cyclosophoraose Isolated from biovar TA-1.

Polymers (Basel) 2019 Mar 12;11(3). Epub 2019 Mar 12.

Department of Systems Biotechnology & Dept. of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul 05029, Korea.

biovar TA-1, a kind of soil bacteria, produces cyclosophoraoses (Cys). Cyclosophoraoses contain various ring sizes with degrees of polymerization ranging from 17 to 23. Atrazine is a hardly-soluble herbicide that contaminates soil and drinking water, and remains in soil for a long time. To remove this insoluble contaminant from aqueous solutions, we have enhanced the solubility of atrazine by complexation with Cys. The complex formation of Cys and atrazine was confirmed using ¹H nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), field emission scanning electron microscopy (FE-SEM), rotating frame nuclear overhauser spectroscopy (ROESY), and molecular modeling studies. The aqueous solubility of atrazine was enhanced 3.69-fold according to the added concentrations (20 mM) of Cys, compared to the 1.78-fold enhancements by β-cyclodextrin (β-CD). Cyclosophoraoses as an excellent solubility enhancer with long glucose chains that can effectively capture insoluble materials showed a potential application of microbial polysaccharides in the removal of hazardous hardly-soluble materials from aqueous solutions in the fields of biological and environmental industry.
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http://dx.doi.org/10.3390/polym11030474DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6473739PMC
March 2019

Noninvasive ultrasound stimulation of the spleen to treat inflammatory arthritis.

Nat Commun 2019 03 12;10(1):951. Epub 2019 Mar 12.

Department of Biomedical Engineering, University of Minnesota, Minneapolis, 55455, MN, USA.

Targeted noninvasive control of the nervous system and end-organs may enable safer and more effective treatment of multiple diseases compared to invasive devices or systemic medications. One target is the cholinergic anti-inflammatory pathway that consists of the vagus nerve to spleen circuit, which has been stimulated with implantable devices to improve autoimmune conditions such as rheumatoid arthritis. Here we report that daily noninvasive ultrasound (US) stimulation targeting the spleen significantly reduces disease severity in a mouse model of inflammatory arthritis. Improvements are observed only with specific parameters, in which US can provide both protective and therapeutic effects. Single cell RNA sequencing of splenocytes and experiments in genetically-immunodeficient mice reveal the importance of both T and B cell populations in the anti-inflammatory pathway. These findings demonstrate the potential for US stimulation of the spleen to treat inflammatory diseases.
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http://dx.doi.org/10.1038/s41467-019-08721-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6414603PMC
March 2019

Invadopodia are chemosensing protrusions that guide cancer cell extravasation to promote brain tropism in metastasis.

Oncogene 2019 05 16;38(19):3598-3615. Epub 2019 Jan 16.

Department of Surgery, Division of Urology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.

Invadopodia are cell protrusions that mediate cancer cell extravasation but the microenvironmental cues and signaling factors that induce invadopodia formation during extravasation remain unclear. Using intravital imaging and loss of function experiments, we determined invadopodia contain receptors involved in chemotaxis, namely GABA receptor and EGFR. These chemotaxis capabilities are mediated in part by PAK1 which controls invadopodia responsiveness to ligands such as GABA and EGF via assembly, stability, and turnover of invadopodia in vivo. PAK1 knockdown rendered cells unresponsive to chemotactic stimuli present in the stroma, resulting in dramatically lower rates of cancer cell extravasation and metastatic colony formation compared to stimulated cancer cells. In an experimental mouse model of brain metastasis, inhibition of PAK1 significantly reduced overall tumor burden and reduced the average size of brain metastases. In summary, invadopodia contain chemotaxis receptors that can respond to microenvironmental cues to guide cancer cell extravasation, and when PAK1 is depleted, brain tropism of metastatic breast cancer cells is significantly reduced, blocking secondary colony growth at sites otherwise permissive for metastatic outgrowth.
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http://dx.doi.org/10.1038/s41388-018-0667-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6756237PMC
May 2019

Nonintegrating Direct Conversion Using mRNA into Hepatocyte-Like Cells.

Biomed Res Int 2018 20;2018:8240567. Epub 2018 Sep 20.

HY Indang Center of Regenerative Medicine and Stem Cell Research, Hanyang University, Seoul 04763, Republic of Korea.

Recently, several researchers have reported that direct reprogramming techniques can be used to differentiate fibroblasts into hepatocyte-like cells without a pluripotent intermediate step. However, the use of viral vectors for conversion continues to pose important challenges in terms of genome integration. Herein, we propose a new method of direct conversion without genome integration with potential clinical applications. To generate hepatocyte-like cells, mRNA coding for the hepatic transcription factors Foxa3 and HNF4 was transfected into mouse embryonic fibroblasts. After 10-12 days, the fibroblasts converted to an epithelial morphology and generated colonies of hepatocyte-like cells (R-iHeps). The generated R-iHeps expressed hepatocyte-specific marker genes and proteins, including albumin, alpha-fetoprotein, HNF4, CK18, and CYP1A2. To evaluate hepatic function, indocyanine green uptake, periodic acid-Schiff staining, and albumin secretion were assessed. Furthermore, mCherry-positive R-iHeps were engrafted in the liver of Alb-TRECK/SCID mice, and we confirmed FAH enzyme expression in FahTyr/RJ models. In conclusion, our data suggest that the nonintegrating method using mRNA has potential for cell therapy.
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http://dx.doi.org/10.1155/2018/8240567DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6171260PMC
January 2019

CuS nanoplates from ionic liquid precursors-Application in organic photovoltaic cells.

J Chem Phys 2018 May;148(19):193818

Functional Polymer Systems, Fraunhofer Institute for Applied Polymer Research, D-14476 Potsdam, Germany.

Hexagonal p-type semiconductor CuS nanoplates were synthesized via a hot injection method from bis(trimethylsilyl)sulfide and the ionic liquid precursor bis(-dodecylpyridinium) tetrachloridocuprate(ii). The particles have a broad size distribution with diameters between 30 and 680 nm and well-developed crystal habits. The nanoplates were successfully incorporated into organic photovoltaic (OPV) cells as hole conduction materials. The power conversion efficiency of OPV cells fabricated with the nanoplates is 16% higher than that of a control device fabricated without the nanoplates.
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http://dx.doi.org/10.1063/1.4991622DOI Listing
May 2018

Small molecule-mediated reprogramming of human hepatocytes into bipotent progenitor cells.

J Hepatol 2019 01 19;70(1):97-107. Epub 2018 Sep 19.

Department of Surgery, Hanyang University College of Medicine, Seoul 04763, Republic of Korea; HY Indang Center of Regenerative Medicine and Stem Cell Research, Hanyang University, Seoul 04763, Republic of Korea. Electronic address:

Background & Aims: Currently, much effort is directed towards the development of new cell sources for clinical therapy using cell fate conversion by small molecules. Direct lineage reprogramming to a progenitor state has been reported in terminally differentiated rodent hepatocytes, yet remains a challenge in human hepatocytes.

Methods: Human hepatocytes were isolated from healthy and diseased donor livers and reprogrammed into progenitor cells by 2 small molecules, A83-01 and CHIR99021 (AC), in the presence of EGF and HGF. The stemness properties of human chemically derived hepatic progenitors (hCdHs) were tested by standard in vitro and in vivo assays and transcriptome profiling.

Results: We developed a robust culture system for generating hCdHs with therapeutic potential. The use of HGF proved to be an essential determinant of the fate conversion process. Based on functional evidence, activation of the HGF/MET signal transduction system collaborated with A83-01 and CHIR99021 to allow a rapid expansion of progenitor cells through the activation of the ERK pathway. hCdHs expressed hepatic progenitor markers and could self-renew for at least 10 passages while retaining a normal karyotype and potential to differentiate into functional hepatocytes and biliary epithelial cells in vitro. Gene expression profiling using RNAseq confirmed the transcriptional reprogramming of hCdHs towards a progenitor state and the suppression of mature hepatocyte transcripts. Upon intrasplenic transplantation in several models of therapeutic liver repopulation, hCdHs effectively repopulated the damaged parenchyma.

Conclusion: Our study is the first report of successful reprogramming of human hepatocytes to a population of proliferating bipotent cells with regenerative potential. hCdHs may provide a novel tool that permits expansion and genetic manipulation of patient-specific progenitors to study regeneration and the repair of diseased livers.

Lay Summary: Human primary hepatocytes were reprogrammed towards hepatic progenitor cells by a combined treatment with 2 small molecules, A83-01 and CHIR99021, and HGF. Chemically derived hepatic progenitors exhibited a high proliferation potential and the ability to differentiate into hepatocytes and biliary epithelial cells both in vitro and in vivo. This approach enables the generation of patient-specific hepatic progenitors and provides a platform for personal and stem cell-based regenerative medicine.
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http://dx.doi.org/10.1016/j.jhep.2018.09.007DOI Listing
January 2019