Publications by authors named "Gun-Jae Jeong"

26 Publications

  • Page 1 of 1

Delivery of a spheroids-incorporated human dermal fibroblast sheet increases angiogenesis and M2 polarization for wound healing.

Biomaterials 2021 Jun 7;275:120954. Epub 2021 Jun 7.

School of Chemical Engineering, Sungkyunkwan University, Suwon, Gyeonggi, 16419, Republic of Korea. Electronic address:

Low cell engraftment is a major problem in tissue engineering. Although various methods related with cell sheets have been attempted to resolve the issue, low cell viability due to oxygen and nutrient depletion remains an obstacle toward advanced therapeutic applications. Cell therapy using fibroblasts is thought of as a good alternative due to the short doubling times of fibroblasts together with their immunomodulatory properties. Furthermore, three-dimensional (3D) fibroblasts exhibit unique angiogenic and inflammation-manipulating properties that are not present in two-dimensional (2D) forms. However, the therapeutic effect of 3D fibroblasts in tissue regeneration has not been fully elucidated. Macrophage polarization has been widely studied, as it stimulates the transition from the inflammation to the proliferation phase of wound healing. Although numerous strategies have been developed to achieve better polarization of macrophages, the low efficacy of these strategies and safety issues remain problematic. To this end, we introduced a biocompatible flat patch with specifically designed holes that form a spheroids-incorporated human dermal fibroblast sheet (SIS) to mediate the activity of inflammatory cytokines for M2 polarization and increase angiogenic efficacy. We further confirmed in vivo enhancement of wound healing with an SIS-laden skin patch (SISS) compared to conventional cell therapy.
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http://dx.doi.org/10.1016/j.biomaterials.2021.120954DOI Listing
June 2021

Development of pH-Responsive Polymer Coating as an Alternative to Enzyme-Based Stem Cell Dissociation for Cell Therapy.

Materials (Basel) 2021 Jan 20;14(3). Epub 2021 Jan 20.

School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Korea.

Cell therapy usually accompanies cell detachment as an essential process in cell culture and cell collection for transplantation. However, conventional methods based on enzymatic cell detachment can cause cellular damage including cell death and senescence during the routine cell detaching step due to an inappropriate handing. The aim of the current study is to apply the pH-responsive degradation property of poly (amino ester) to the surface of a cell culture dish to provide a simple and easy alternative method for cell detachment that can substitute the conventional enzyme treatment. In this study, poly (amino ester) was modified (cell detachable polymer, CDP) to show appropriate pH-responsive degradation under mild acidic conditions (0.05% (w/v) CDP, pH 6.0) to detach stem cells (human adipose tissue-derived stem cells (hADSCs)) perfectly within a short period (less than 10 min). Compared to conventional enzymatic cell detachment, hADSCs cultured on and detached from a CDP-coated cell culture dish showed similar cellular properties. We further performed in vivo experiments on a mouse hindlimb ischemia model (1.0 × 10 cells per limb). The in vivo results indicated that hADSCs retrieved from normal cell culture dishes and CDP-coated cell culture dishes showed analogous therapeutic angiogenesis. In conclusion, CDP could be applied to a pH-responsive cell detachment system as a simple and easy nonenzymatic method for stem cell culture and various cell therapies.
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http://dx.doi.org/10.3390/ma14030491DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7864336PMC
January 2021

Regulation of intracellular transition metal ion level with a pH-sensitive inorganic nanocluster to improve therapeutic angiogenesis by enriching conditioned medium retrieved from human adipose derived stem cells.

Nano Converg 2020 Oct 16;7(1):34. Epub 2020 Oct 16.

School of Chemical Engineering, Sungkyunkwan University, Suwon, 440-746, Republic of Korea.

Cell therapy based on human adipose derived stem cells (hADSCs) is a known potential therapeutic approach to induce angiogenesis in ischemic diseases. However, the therapeutic efficacy of direct hADSC injection is limited by a low cell viability and poor cell engraftment after administration. To improve the outcomes of this kind of approach, various types of nanoparticles have been utilized to improve the therapeutic efficacy of hADSC transplantation. Despite their advantages, the adverse effects of nanoparticles, such as genetic damage and potential oncogenesis based on non-degradable property of nanoparticles prohibit the application of nanoparticles toward the clinical applications. Herein, we designed a transition metal based inorganic nanocluster able of pH-selective degradation (ps-TNC), with the aim of enhancing an hADSC based treatment of mouse hindlimb ischemia. Our ps-TNC was designed to undergo degradation at low pH conditions, thus releasing metal ions only after endocytosis, in the endosome. To eliminate the limitations of both conventional hADSC injection and non-degradable property of nanoparticles, we have collected conditioned medium (CM) from the ps-TNC treated hADSCs and administrated it to the ischemic lesions. We found that intracellular increment of transition metal ion upregulated the hypoxia-inducible factor 1α, which can induce vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) expressions. Based on the molecular mechanism, the secretion of VEGF and bFGF by ps-TNC treated hADSCs showed a significant improvement compared to that of untreated cells. Injecting the CM collected from ps-TNC treated hADSCs into the mouse hindlimb ischemia model (ps-TNC-CM group) showed significantly improved angiogenesis in the lesions, with improved limb salvage and decreased muscle degeneration compared to the group injected with CM collected from normal hADSCs (CM group). This study suggests a novel strategy, combining a known angiogenesis molecular mechanism with both an improvement on conventional stem cell therapy and the circumvention of some limitations still present in modern approaches based on nanoparticles.
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http://dx.doi.org/10.1186/s40580-020-00244-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7567771PMC
October 2020

Endosome-triggered ion-releasing nanoparticles as therapeutics to enhance the angiogenic efficacy of human mesenchymal stem cells.

J Control Release 2020 08 23;324:586-597. Epub 2020 May 23.

School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea. Electronic address:

Here, we report that Fe ions delivered into human mesenchymal stem cells (hMSCs) by bioreducible metal nanoparticles (NPs) enhance their angiogenic and cell-homing efficacy by controlling ion-triggered intracellular reactive oxygen species (ROS) and improve cell migration, while reducing cytotoxicity. Endosome-triggered iron-ion-releasing nanoparticles (ETIN) were designed to be low-pH responsive to take advantage of the low-pH conditions (4-5) of endosomes for in situ iron-ion release. Due to the different redox potentials of Fe and Au, only Fe could be ionized and released from our novel ETIN, while Au remained intact after ETIN endocytosis. Treatment with an optimal amount of ETIN led to a mild increase in intracellular ROS levels in hMSCs, which enhanced the expression of HIF-1α, a key trigger for angiogenic growth factor secretion from hMSCs. Treatmetn of hMSCs with ETIN significantly enhanced the expression of angiogenesis- and lesion-targeting-related genes and proteins. Transplantation of ETIN-treated hMSCs significantly enhanced angiogenesis and tissue regeneration in a wound-closing mouse model compared with those in untreated mice and mice that underwent conventional hMSC transplantation.
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http://dx.doi.org/10.1016/j.jconrel.2020.05.038DOI Listing
August 2020

Synthesis of Sub 3 nm-Sized Uniform Magnetite Nanoparticles Using Reverse Micelle Method for Biomedical Application.

Materials (Basel) 2019 Nov 22;12(23). Epub 2019 Nov 22.

Department of Chemical Engineering, Kyung Hee University, Yongin 17104, Korea.

We report a synthetic method for small and uniform FeO (magnetite) nanoparticles under mild conditions. Spherical sub-3 nm-sized magnetite nanoparticles were prepared via reverse micelles composed of oleylamine, F127, xylene, and water for the reaction of iron(III) stearate with hydrazine at a reaction temperature of 90 °C in air atmosphere. These synthesized magnetite nanoparticles exhibited good size uniformity. By controlling experimental conditions, we could easily control both size and size uniformity of these magnetite nanoparticles. We further investigated whether FeO could be used in biomedical applications. Cytotoxicity of FeO was evaluated with human adipose-derived stem cells (hADSCs). Our results showed that the number of hADSCs did not significantly decrease when these cells were treated with FeO nanoparticles at a concentration of up to 9 μg/mL. Apoptotic activity and cell proliferation of hADSCs treated with FeO nanoparticles were similar to those of hADSCs without any treatment. This novel method could be used for synthesizing uniform and biocompatible FeO nanoparticles with further biomedical applications.
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http://dx.doi.org/10.3390/ma12233850DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6926741PMC
November 2019

Cardiac-mimetic cell-culture system for direct cardiac reprogramming.

Theranostics 2019 19;9(23):6734-6744. Epub 2019 Sep 19.

School of Chemical and Biological Engineering, Seoul National University, Seoul, Republic of Korea.

Cardiovascular diseases often cause substantial heart damage and even heart failure due to the limited regenerative capacity of adult cardiomyocytes. The direct cardiac reprogramming of fibroblasts could be a promising therapeutic option for these patients. Although exogenous transcriptional factors can induce direct cardiac reprogramming, the reprogramming efficiency is too low to be used clinically. Herein, we introduce a cardiac-mimetic cell-culture system that resembles the microenvironment in the heart and provides interactions with cardiomyocytes and electrical cues to the cultured fibroblasts for direct cardiac reprogramming. Nano-thin and nano-porous membranes and heart like electric stimulus were used in the cardiac-mimetic cell-culture system. The human neonatal dermal fibroblasts containing cardiac transcription factors were plated on the membrane and cultured with the murine cardiomyocyte in the presence of the electric stimulus. The reprogramming efficiency was evaluated by qRT-PCR and immunocytochemistry. Nano-thin and nano-porous membranes in the culture system facilitated interactions between fibroblasts and cardiomyocytes in coculture. The cellular interactions and electric stimulation supplied by the culture system dramatically enhanced the cardiac reprogramming efficiency of cardiac-specific transcriptional factor-transfected fibroblasts. The cardiac-mimetic culture system may serve as an effective tool for producing a feasible number of reprogrammed cardiomyocytes from fibroblasts.
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http://dx.doi.org/10.7150/thno.35574DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815967PMC
July 2020

Enhancing the Wound Healing Effect of Conditioned Medium Collected from Mesenchymal Stem Cells with High Passage Number Using Bioreducible Nanoparticles.

Int J Mol Sci 2019 Sep 28;20(19). Epub 2019 Sep 28.

School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Korea.

Injecting human mesenchymal stem cells (hMSCs) at wound sites is known to have a therapeutic effect; however, hMSCs have several limitations, such as low viability and poor engraftment after injection, as well as a potential risk of oncogenesis. The use of a conditioned medium (CM) was suggested as an alternative method for treating various wounds instead of direct hMSC administration. In addition to not having the adverse effects associated with hMSCs, a CM can be easily mass produced and can be stored for long-term, thereby making it useful for clinical applications. In general, a CM is collected from hMSCs with low passage number; whereas, the hMSCs with high passage number are usually discarded because of their low therapeutic efficacy as a result of reduced angiogenic factor secretion. Herein, we used a CM collected from high passage number (passage 12, P12) hMSCs treated with gold-iron nanoparticles (AuFe NPs). Our AuFe NPs were designed to release the iron ion intracellularly via endocytosis. Endosomes with low pH can dissolve iron from AuFe NPs, and thus, the intracellularly released iron ions up-regulate the hypoxia-inducible factor 1α and vascular endothelial growth factor (VEGF) expression. Through this mechanism, AuFe NPs improve the amount of VEGF expression from P12 hMSCs so that it is comparable to the amount of VEGF expression from low passage number (passage 6, P6), without treatment. Furthermore, we injected the CM retrieved from P12 MSCs treated with AuFe NPs in the mouse skin wound model (AuFe P12 group). AuFe P12 group revealed significantly enhanced angiogenesis in the mouse skin wound model compared to the high passage hMSC CM-injected group. Moreover, the result from the AuFe P12 group was similar to that of the low passage hMSC CM-injected group. Both the AuFe P12 group and low passage hMSC CM-injected group presented significantly enhanced re-epithelization, angiogenesis, and tissue remodeling compared to the high passage hMSC CM-injected group. This study reveals a new strategy for tissue regeneration based on CM injection without considering the high cell passage count.
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http://dx.doi.org/10.3390/ijms20194835DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6801963PMC
September 2019

Enhanced Anti-Cancer Effects of Conditioned Medium from Hypoxic Human Umbilical Cord-Derived Mesenchymal Stem Cells.

Int J Stem Cells 2019 Jul;12(2):291-303

Division of Vascular Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

Background And Objectives: There have been contradictory reports on the pro-cancer or anti-cancer effects of mesenchymal stem cells. In this study, we investigated whether conditioned medium (CM) from hypoxic human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) (H-CM) showed enhanced anti-cancer effects compared with CM from normoxic hUC-MSCs (N-CM).

Methods And Results: Compared with N-CM, H-CM not only strongly reduced cell viability and increased apoptosis of human cervical cancer cells (HeLa cells), but also increased caspase-3/7 activity, decreased mitochondrial membrane potential (MMP), and induced cell cycle arrest. In contrast, cell viability, apoptosis, MMP, and cell cycle of human dermal fibroblast (hDFs) were not significantly changed by either CM whereas caspase-3/7 activity was decreased by H-CM. Protein antibody array showed that activin A, Beta IG-H3, TIMP-2, RET, and IGFBP-3 were upregulated in H-CM compared with N-CM. Intracellular proteins that were upregulated by H-CM in HeLa cells were represented by apoptosis and cell cycle arrest terms of biological processes of Gene Ontology (GO), and by cell cycle of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. In hDFs, negative regulation of apoptosis in biological process of GO and PI3K-Akt signaling pathway of KEGG pathways were represented.

Conclusions: H-CM showed enhanced anti-cancer effects on HeLa cells but did not influence cell viability or apoptosis of hDFs and these different effects were supported by profiling of secretory proteins in both kinds of CM and intracellular signaling of HeLa cells and hDFs.
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http://dx.doi.org/10.15283/ijsc19002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6657944PMC
July 2019

FGF-17 from Hypoxic Human Wharton's Jelly-Derived Mesenchymal Stem Cells Is Responsible for Maintenance of Cell Proliferation at Late Passages.

Int J Stem Cells 2019 Jul;12(2):279-290

Division of Vascular Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

Background And Objectives: Although it is well known that hypoxic culture conditions enhance proliferation of human mesenchymal stem cells, the exact mechanism is not fully understood. In this study, we investigated the effect of fibroblast growth factor (FGF)-17 from hypoxic human Wharton's Jelly-derived mesenchymal stem cells (hWJ-MSCs) on cell proliferation at late passages.

Methods And Results: hWJ-MSCs were cultured in -MEM medium supplemented with 10% fetal bovine serum (FBS) in normoxic (21% O) and hypoxic (1% O) conditions. Protein antibody array was performed to analyze secretory proteins in conditioned medium from normoxic and hypoxic hWJ-MSCs at passage 10. Cell proliferation of hypoxic hWJ-MSCs was increased compared with normoxic hWJ-MSCs from passage 7 to 10, and expression of secretory FGF-17 was highly increased in conditioned medium from hypoxic hWJ-MSCs at passage 10. Knockdown of FGF-17 in hypoxic and normoxic hWJ-MSCs decreased cell proliferation, whereas treatment of hypoxic and normoxic hWJ-MSCs with recombinant protein FGF-17 increased their proliferation. Signal transduction of FGF-17 in hypoxic and normoxic hWJ-MSCs involved the ERK1/2 pathway. Cell phenotypes were not changed under either condition. Differentiation-related genes , , and were downregulated in normoxic hWJ-MSCs treated with rFGF-17, and upregulated by siFGF-17. Expression of (), , and was upregulated in hypoxic hWJ-MSCs, and this effect was rescued by transfection with siFGF-17. Only was upregulated in hypoxic hWJ-MSCs with rFGF-17.

Conclusions: In hypoxic culture conditions, FGF-17 from hypoxic hWJ-MSCs contributes to the maintenance of high proliferation at late passages through the ERK1/2 pathway.
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http://dx.doi.org/10.15283/ijsc18042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6657939PMC
July 2019

Metabolites can regulate stem cell behavior through the STAT3/AKT pathway in a similar trend to that under hypoxic conditions.

Sci Rep 2019 04 16;9(1):6112. Epub 2019 Apr 16.

Division of Vascular Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.

Stem cell therapy has long been considered a promising mode of treatment for many incurable diseases. Human mesenchymal stem cells (hMSCs) have provided the most promising results to date for regenerative medicine. Nevertheless, due to several obstacles such as difficulty in sourcing and characterizing hMSCs, they remain largely unavailable for clinical use. The signaling requirements for maintaining stem cell function have been studied widely, but little is known about how metabolism contributes to stem cell function. hMSCs have been shown to promote therapeutic efficacy in hypoxic conditions through metabolic conversion. According to published studies, certain metabolites are able to convert stem cell metabolism from oxidative phosphorylation to glycolysis. In this study, we selected several metabolites (fructose-1,6-bisphosphate (FBP), Phosphoenolpyruvic acid (PEP) and sodium oxalate (OXA)) to examine the relation between metabolites and stem cell functions. In addition, we investigated the ability of selected metabolites to induce rapid expansion of this cell population. Our results indicate that selected metabolites stimulate stem cell proliferation by induce glycolytic metabolism via AKT/STAT signaling.
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http://dx.doi.org/10.1038/s41598-019-42669-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6468014PMC
April 2019

A Disposable Photovoltaic Patch Controlling Cellular Microenvironment for Wound Healing.

Int J Mol Sci 2018 Oct 4;19(10). Epub 2018 Oct 4.

Department of BioNano Technology, Gachon University, Seongnam 13120, Korea.

Electrical stimulation (ES) is known to affect the wound healing process by modulating skin cell behaviors. However, the conventional clinical devices that can generate ES for promoting wound healing require patient hospitalization due to large-scale of the extracorporeal devices. Herein, we introduce a disposable photovoltaic patch that can be applied to skin wound sites to control cellular microenvironment for promoting wound healing by generating ES. In vitro experiment results show that exogenous ES could enhance cell migration, proliferation, expression of extracellular matrix proteins, and myoblast differentiation of fibroblasts which are critical for wound healing. Our disposable photovoltaic patches were attached to the back of skin wound induced mice. Our patch successfully provided ES, generated by photovoltaic energy harvested from the organic solar cell under visible light illumination. In vivo experiment results show that the patch promoted cutaneous wound healing via enhanced host-inductive cell proliferation, cytokine secretion, and protein synthesis which is critical for wound healing process. Unlike the current treatments for wound healing that engage passive healing processes and often are unsuccessful, our wearable photovoltaic patch can stimulate regenerative activities of endogenous cells and actively contribute to the wound healing processes.
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http://dx.doi.org/10.3390/ijms19103025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6213857PMC
October 2018

M1 Macrophage-Derived Nanovesicles Potentiate the Anticancer Efficacy of Immune Checkpoint Inhibitors.

ACS Nano 2018 09 29;12(9):8977-8993. Epub 2018 Aug 29.

School of Chemical and Biological Engineering , Seoul National University , Seoul 08826 , Republic of Korea.

Cancer immunotherapy modulates immune cells to induce antitumor immune responses. Tumors employ immune checkpoints to evade immune cell attacks. Immune checkpoint inhibitors such as anti-PD-L1 antibody (aPD-L1), which is being used clinically for cancer treatments, can block immune checkpoints so that the immune system can attack tumors. However, immune checkpoint inhibitor therapy may be hampered by polarization of macrophages within the tumor microenvironment (TME) into M2 tumor-associated macrophages (TAMs), which suppress antitumor immune responses and promote tumor growth by releasing anti-inflammatory cytokines and angiogenic factors. In this study, we used exosome-mimetic nanovesicles derived from M1 macrophages (M1NVs) to repolarize M2 TAMs to M1 macrophages that release pro-inflammatory cytokines and induce antitumor immune responses and investigated whether the macrophage repolarization can potentiate the anticancer efficacy of aPD-L1. M1NV treatment induced successful polarization of M2 macrophages to M1 macrophages in vitro and in vivo. Intravenous injection of M1NVs into tumor-bearing mice suppressed tumor growth. Importantly, injection of a combination of M1NVs and aPD-L1 further reduced the tumor size, compared to the injection of either M1NVs or aPD-L1 alone. Thus, our study indicates that M1NV injection can repolarize M2 TAMs to M1 macrophages and potentiate antitumor efficacy of the checkpoint inhibitor therapy.
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http://dx.doi.org/10.1021/acsnano.8b02446DOI Listing
September 2018

An Injectable Decellularized Matrix That Improves Mesenchymal Stem Cell Engraftment for Therapeutic Angiogenesis.

ACS Biomater Sci Eng 2018 Jul 20;4(7):2571-2581. Epub 2018 Jun 20.

Stem cell therapy has great potential for the treatment of ischemic diseases, but poor engraftment of implanted stem cells limits the therapeutic efficacy. Here, we developed an approximately 80 μm injectable decellularized matrix (IDM) to increase the angiogenic efficacy of mesenchymal stem cells by improving the engraftment of the stem cells implanted in to an ischemic tissue. Adhesion of human adipose tissue-derived stem cells (hADSCs) to the IDM enhanced the cell viability and upregulated angiogenic factors in vitro under either cell adhesion-suppressive conditions or hypoxic conditions, which simulated the microenvironment of ischemic tissues. In a murine ischemic-hindlimb model, hADSCs that were attached to the IDM and subsequently injected into an ischemic region showed better grafting and angiogenic factor expression. The hADSC-IDM implantation subsequently promoted the formation of microvessels, attenuated fibrosis, and increased blood perfusion in the ischemic region, as compared to implantation of hADSCs only. The IDM may be an effective off-the-shelf material that can enhance therapeutic efficacy of stem cell therapy for ischemic diseases.
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http://dx.doi.org/10.1021/acsbiomaterials.8b00617DOI Listing
July 2018

Dual Roles of Graphene Oxide To Attenuate Inflammation and Elicit Timely Polarization of Macrophage Phenotypes for Cardiac Repair.

ACS Nano 2018 02 7;12(2):1959-1977. Epub 2018 Feb 7.

School of Chemical and Biological Engineering, Seoul National University , Seoul, 08826, Republic of Korea.

Development of localized inflammatory environments by M1 macrophages in the cardiac infarction region exacerbates heart failure after myocardial infarction (MI). Therefore, the regulation of inflammation by M1 macrophages and their timely polarization toward regenerative M2 macrophages suggest an immunotherapy. Particularly, controlling cellular generation of reactive oxygen species (ROS), which cause M1 differentiation, and developing M2 macrophage phenotypes in macrophages propose a therapeutic approach. Previously, stem or dendritic cells were used in MI for their anti-inflammatory and cardioprotective potentials and showed inflammation modulation and M2 macrophage progression for cardiac repair. However, cell-based therapeutics are limited due to invasive cell isolation, time-consuming cell expansion, labor-intensive and costly ex vivo cell manipulation, and low grafting efficiency. Here, we report that graphene oxide (GO) can serve as an antioxidant and attenuate inflammation and inflammatory polarization of macrophages via reduction in intracellular ROS. In addition, GO functions as a carrier for interleukin-4 plasmid DNA (IL-4 pDNA) that propagates M2 macrophages. We synthesized a macrophage-targeting/polarizing GO complex (MGC) and demonstrated that MGC decreased ROS in immune-stimulated macrophages. Furthermore, DNA-functionalized MGC (MGC/IL-4 pDNA) polarized M1 to M2 macrophages and enhanced the secretion of cardiac repair-favorable cytokines. Accordingly, injection of MGC/IL-4 pDNA into mouse MI models attenuated inflammation, elicited early polarization toward M2 macrophages, mitigated fibrosis, and improved heart function. Taken together, the present study highlights a biological application of GO in timely modulation of the immune environment in MI for cardiac repair. Current therapy using off-the-shelf material GO may overcome the shortcomings of cell therapies for MI.
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http://dx.doi.org/10.1021/acsnano.7b09107DOI Listing
February 2018

Efficient Direct Lineage Reprogramming of Fibroblasts into Induced Cardiomyocytes Using Nanotopographical Cues.

J Biomed Nanotechnol 2017 Mar;13(3):269-79

Induced cardiomyocytes (iCMs) generated via direct lineage reprogramming offer a novel therapeutic target for the study and treatment of cardiac diseases. However, the efficiency of iCM generation is significantly low for therapeutic applications. Here, we show an efficient direct conversion of somatic fibroblasts into iCMs using nanotopographic cues. Compared with flat substrates, the direct conversion of fibroblasts into iCMs on nanopatterned substrates resulted in a dramatic increase in the reprogramming efficiency and maturation of iCM phenotypes. Additionally, enhanced reprogramming by substrate nanotopography was due to changes in the activation of focal adhesion kinase and specific histone modifications. Taken together, these results suggest that nanotopographic cues can serve as an efficient stimulant for direct lineage reprogramming into iCMs.
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http://dx.doi.org/10.1166/jbn.2017.2347DOI Listing
March 2017

Therapeutic Angiogenesis via Solar Cell-Facilitated Electrical Stimulation.

ACS Appl Mater Interfaces 2017 Nov 27;9(44):38344-38355. Epub 2017 Oct 27.

Department of BioNano Technology, Gachon University , Seongnam 13120, Republic of Korea.

Cell therapy has been suggested as a treatment modality for ischemic diseases, but the poor survival and engraftment of implanted cells limit its therapeutic efficacy. To overcome such limitation, we used electrical stimulation (ES) derived from a wearable solar cell for inducing angiogenesis in ischemic tissue. ES enhanced the secretion of angiogenic growth factors and the migration of mesenchymal stem cells (MSCs), myoblasts, endothelial progenitor cells, and endothelial cells in vitro. In a mouse ischemic hindlimb model, ES generated by a solar cell and applied to the ischemic region promoted migration of MSCs toward the ischemic site and upregulated expression of angiogenic paracrine factors (vascular endothelial, basic fibroblast, and hepatocyte growth factors; and stromal cell-derived factor-1α). Importantly, solar cell-generated ES promoted the formation of capillaries and arterioles at the ischemic region, attenuated muscle necrosis and fibrosis, and eventually prevented loss of the ischemic limb. Solar cell ES therapy showed higher angiogenic efficacy than conventional MSC therapy. This study shows the feasibility of using solar cell ES as a novel treatment for therapeutic angiogenesis.
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http://dx.doi.org/10.1021/acsami.7b13322DOI Listing
November 2017

Lineage Specific Differentiation of Magnetic Nanoparticle-Based Size Controlled Human Embryoid Body.

ACS Biomater Sci Eng 2017 Aug 18;3(8):1719-1729. Epub 2017 Jul 18.

School of Chemical and Biological Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.

Human embryonic stem cells (hESCs) possess unique properties in terms of self-renewal and differentiation, which make them particularly well-suited for use in tissue engineering and regenerative medicine. The differentiation of hESCs in the form of human embryoid bodies (hEBs) recapitulates early embryonic development, and hEBs may provide useful insight into the embryological development of humans. Herein, cell-penetrating magnetic nanoparticles (MNPs) were utilized to form hEBs with defined sizes and the differentiation patterns were analyzed. Through intracellular delivery of MNPs into the hESCs, suspended and magnetized hESCs efficiently clustered in to hEBs driven by magnetic pin-based external magnetic forces. The hEB size was controlled by varying the suspended cell numbers that were applied in the magnetic pin system. After 3 days of differentiation in a suspended condition, ectodermal differentiation was observed to have been enhanced in the small hEBs (150 μm in diameter) while endodermal and mesodermal differentiation were enhanced in large hEBs (600 μm in diameter). This indicates that the size of the hEBs plays an important role in the early lineage commitment of hESCs, and MNP-based control of the hEB size would be a novel, useful methodology for lineage-specific hESC differentiation.
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http://dx.doi.org/10.1021/acsbiomaterials.7b00141DOI Listing
August 2017

Efficient mRNA delivery with graphene oxide-polyethylenimine for generation of footprint-free human induced pluripotent stem cells.

J Control Release 2016 08 4;235:222-235. Epub 2016 Jun 4.

Department of Animal Biotechnology (Stem Cell & Regenerative Biotechnology), Animal Resources Research Center, Incurable Disease Animal Model and Stem Cell Institute (IDASI), Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea. Electronic address:

Clinical applications of induced pluripotent stem cells (iPSCs) require development of technologies for the production of "footprint-free" (gene integration-free) iPSCs, which avoid the potential risk of insertional mutagenesis in humans. Previously, several studies have shown that mRNA transfer can generate "footprint-free" iPSCs, but these studies did not use a delivery vehicle and thus repetitive daily transfection was required because of mRNA degradation. Here, we report an mRNA delivery system employing graphene oxide (GO)-polyethylenimine (PEI) complexes for the efficient generation of "footprint-free" iPSCs. GO-PEI complexes were found to be very effective for loading mRNA of reprogramming transcription factors and protection from mRNA degradation by RNase. Dynamic suspension cultures of GO-PEI/RNA complexes-treated cells dramatically increased the reprogramming efficiency and successfully generated rat and human iPSCs from adult adipose tissue-derived fibroblasts without repetitive daily transfection. The iPSCs showed all the hallmarks of pluripotent stem cells including expression of pluripotency genes, epigenetic reprogramming, and differentiation into the three germ layers. These results demonstrate that mRNA delivery using GO-PEI-RNA complexes can efficiently generate "footprint-free" iPSCs, which may advance the translation of iPSC technology into the clinical settings.
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http://dx.doi.org/10.1016/j.jconrel.2016.06.007DOI Listing
August 2016

Enhanced Bone Repair by Guided Osteoblast Recruitment Using Topographically Defined Implant.

Tissue Eng Part A 2016 Apr 31;22(7-8):654-64. Epub 2016 Mar 31.

1 School of Chemical and Biological Engineering, Seoul National University , Seoul, Republic of Korea.

The rapid recruitment of osteoblasts in bone defects is an essential prerequisite for efficient bone repair. Conventionally, osteoblast recruitment to bone defects and subsequent bone repair has been achieved using growth factors. Here, we present a methodology that can guide the recruitment of osteoblasts to bone defects with topographically defined implants (TIs) for efficient in vivo bone repair. We compared circular TIs that had microgrooves in parallel or radial arrangements with nonpatterned implants for osteoblast migration and in vivo bone formation. In vitro, the microgrooves in the TIs enhanced both the migration and proliferation of osteoblasts. Especially, the microgrooves with radial arrangement demonstrated a much higher efficiency of osteoblast recruitment to the implants than did the other types of implants, which may be due to the efficient guidance of cell migration toward the cell-free area of the implants. The expression of the intracellular signaling molecules responsible for the cell migration was also upregulated in osteoblasts on the microgrooved TIs. In vivo, the TI with radially defined topography demonstrated much greater bone repair in mouse calvarial defect models than in the other types of implants. Taken together, these results indicate that implants with physical guidance can enhance tissue repair by rapid cell recruitment.
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http://dx.doi.org/10.1089/ten.TEA.2015.0417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4840921PMC
April 2016

Therapeutic angiogenesis using tumor cell-conditioned medium.

Biotechnol Prog 2016 03 23;32(2):456-64. Epub 2016 Jan 23.

School of Chemical and Biological Engineering, Seoul National University, Seoul, 151-744, Republic of Korea.

Stem cell-conditioned medium (CM), which contains angiogenic factors that are secreted by stem cells, represents a potential therapy for ischemic diseases. Along with stem cells, tumor cells also secrete various angiogenic factors. Here, tumor cells as a cell source of CM for therapeutic angiogenesis was evaluated and the therapeutic efficacy of tumor cell CM in mouse hindlimb ischemia models was demonstrated. CM obtained from a human fibrosarcoma HT1080 cell line culture was compared with CM obtained from a human bone marrow-derived mesenchymal stem cell (MSC) culture. HT1080 CM contained higher concentrations of angiogenic factors compared with MSC CM, which was attributable to the higher cell density that resulted from a much faster growth rate of HT1080 cells compared with MSCs. For use in in vitro and in vivo angiogenesis studies, HT1080 CM was diluted such that HT1080 CM and MSC CM would have the same cell number basis. The two types of CMs induced the same extent of human umbilical vein endothelial cell (HUVEC) proliferation in vitro. The injection of HT1080 CM into mouse ischemic limbs significantly improved capillary density and blood perfusion compared with the injection of fresh medium. Although the therapeutic outcome of HT1080 CM was similar to that of MSC CM, the preparation of CM by tumor cell line culture would be much more efficient due to the faster growth and unlimited life-time of the tumor cell line. These data suggest the potential application of tumor cell CM as a therapeutic modality for angiogenesis and ischemic diseases. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:456-464, 2016.
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http://dx.doi.org/10.1002/btpr.2226DOI Listing
March 2016

Transplantation of heterospheroids of islet cells and mesenchymal stem cells for effective angiogenesis and antiapoptosis.

Tissue Eng Part A 2015 Mar 5;21(5-6):1024-35. Epub 2015 Feb 5.

1 School of Chemical and Biological Engineering, Seoul National University , Seoul, Republic of Korea.

Although islet transplantation has been suggested as an alternative therapy for type 1 diabetes, there are efficiency concerns that are attributed to poor engraftment of transplanted islets. Hypoxic condition and delayed vasculogenesis induce necrosis and apoptosis of the transplanted islets. To overcome these limitations in islet transplantation, heterospheroids (HSs), which consist of rat islet cells (ICs) and human bone marrow-derived mesenchymal stem cells (hMSCs), were transplanted to the kidney and liver. The HSs cultured under the hypoxic condition system exhibited a significant increase in antiapoptotic gene expression in ICs. hMSCs in the HSs secreted angiogenic and antiapoptotic proteins. With the HS system, ICs and hMSCs were successfully located in the same area of the liver after transplantation of HSs through the portal vein, whereas the transplantation of islets and the dissociated hMSCs did not result in localization of transplanted ICs and hMSCs in the same area. HS transplantation resulted in an increase in angiogenesis at the transplantation area and a decrease in the apoptosis of transplanted ICs after transplantation into the kidney subcapsule compared with transplantation of islet cell clusters (ICCs). Insulin production levels of ICs were higher in the HS transplantation group compared with the ICC transplantation group. The HS system may be a more efficient transplantation method than the conventional methods for the treatment of type 1 diabetes.
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http://dx.doi.org/10.1089/ten.TEA.2014.0022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356221PMC
March 2015

Graphene enhances the cardiomyogenic differentiation of human embryonic stem cells.

Biochem Biophys Res Commun 2014 Sep 22;452(1):174-80. Epub 2014 Aug 22.

Engineering Research Institute, Seoul National University, Seoul, Republic of Korea; School of Chemical and Biological Engineering, Seoul National University, Seoul, Republic of Korea; Institute of Bioengineering, Institute of Chemical Processes, Seoul National University, Seoul, Republic of Korea. Electronic address:

Graphene has drawn attention as a substrate for stem cell culture and has been reported to stimulate the differentiation of multipotent adult stem cells. Here, we report that graphene enhances the cardiomyogenic differentiation of human embryonic stem cells (hESCs) at least in part, due to nanoroughness of graphene. Large-area graphene on glass coverslips was prepared via the chemical vapor deposition method. The coating of the graphene with vitronectin (VN) was required to ensure high viability of the hESCs cultured on the graphene. hESCs were cultured on either VN-coated glass (glass group) or VN-coated graphene (graphene group) for 21 days. The cells were also cultured on glass coated with Matrigel (Matrigel group), which is a substrate used in conventional, directed cardiomyogenic differentiation systems. The culture of hESCs on graphene promoted the expression of genes involved in the stepwise differentiation into mesodermal and endodermal lineage cells and subsequently cardiomyogenic differentiation compared with the culture on glass or Matrigel. In addition, the culture on graphene enhanced the gene expression of cardiac-specific extracellular matrices. Culture on graphene may provide a new platform for the development of stem cell therapies for ischemic heart diseases by enhancing the cardiomyogenic differentiation of hESCs.
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http://dx.doi.org/10.1016/j.bbrc.2014.08.062DOI Listing
September 2014

Incorporation of gold-coated microspheres into embryoid body of human embryonic stem cells for cardiomyogenic differentiation.

Tissue Eng Part A 2015 Jan 8;21(1-2):374-81. Epub 2014 Sep 8.

1 Engineering Research Institute, Seoul National University , Seoul, Republic of Korea.

Human embryonic stem cells (hESCs) are a useful cell source for cardiac regeneration by stem cell therapy. In this study, we show that incorporation of gold-coated microspheres into hESC-derived embryoid bodies (EBs) enhances the cardiomyogenic differentiation process of pluripotent embryonic stem cells. A polycaprolactone (PCL) microsphere surface was coated with gold. Either gold-coated PCL microspheres (AuMS) or PCL microspheres (MS) were incorporated into hESC-derived EBs. AuMS and MS were not cytotoxic. AuMS promoted the expression of genes for mesodermal and cardiac mesodermal lineage cells, both of which are intermediates in the process of cardiac differentiation of hESCs on day 4 and the expression of cardiomyogenic differentiation markers on day 14 compared to MS. AuMS also enhanced gene expression of cardiac-specific extracellular matrices. Incorporation of gold-coated MS into hESC-derived EBs may provide a new platform for inducing cardiomyogenic differentiation of pluripotent embryonic stem cells.
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http://dx.doi.org/10.1089/ten.TEA.2014.0015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4293129PMC
January 2015

Delivery of bone morphogenetic protein-2 and substance P using graphene oxide for bone regeneration.

Int J Nanomedicine 2014 7;9 Suppl 1:107-16. Epub 2014 May 7.

School of Chemical and Biological Engineering, Seoul National University, Seoul, Republic of Korea ; Institute of Bioengineering, Institute of Chemical Processes, Engineering Research Institute, Seoul National University, Seoul, Republic of Korea.

In this study, we demonstrate that graphene oxide (GO) can be used for the delivery of bone morphogenetic protein-2 (BMP-2) and substance P (SP), and that this delivery promotes bone formation on titanium (Ti) implants that are coated with GO. GO coating on Ti substrate enabled a sustained release of BMP-2. BMP-2 delivery using GO-coated Ti exhibited a higher alkaline phosphatase activity in bone-forming cells in vitro compared with bare Ti. SP, which is known to recruit mesenchymal stem cells (MSCs), was co-delivered using Ti or GO-coated Ti to further promote bone formation. SP induced the migration of MSCs in vitro. The dual delivery of BMP-2 and SP using GO-coated Ti showed the greatest new bone formation on Ti implanted in the mouse calvaria compared with other groups. This approach may be useful to improve osteointegration of Ti in dental or orthopedic implants.
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http://dx.doi.org/10.2147/IJN.S50742DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4024979PMC
January 2015

Mesenchymal stem cell-conditioned medium enhances osteogenic and chondrogenic differentiation of human embryonic stem cells and human induced pluripotent stem cells by mesodermal lineage induction.

Tissue Eng Part A 2014 Apr 18;20(7-8):1306-13. Epub 2013 Dec 18.

1 Department of Bioengineering, Hanyang University , Seoul, Republic of Korea.

Human mesenchymal stem cells (hMSCs) have the ability to differentiate into mesenchymal lineages. In this study, we hypothesized that treatment of embryoid bodies (EBs) composed of either human embryonic stem cells (hESCs) or human induced pluripotent stem cells (hiPSCs) with a hMSC-conditioned medium (CM) can stimulate the induction of the mesodermal lineage and subsequent differentiation toward the osteogenic and chondrogenic lineage. Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) analysis indicated that the hMSC-CM treatment increased gene expression related to the mesodermal lineage and decreased gene expression related to the endodermal and ectodermal lineage in EBs. Fourteen days after culturing the mesodermal lineage-induced EBs in the osteogenic or chondrogenic differentiation medium, we observed enhanced osteogenic and chondrogenic differentiation compared with untreated EBs, as evaluated using qRT-PCR, cytochemistry, immunocytochemistry, and flow cytometry. This method may be useful for enhancing the osteogenic or chondrogenic differentiation of hESCs or hiPSCs.
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http://dx.doi.org/10.1089/ten.TEA.2013.0265DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3993069PMC
April 2014

Delivery of a therapeutic protein for bone regeneration from a substrate coated with graphene oxide.

Small 2013 Dec 10;9(23):4051-60. Epub 2013 Jul 10.

School of Chemical & Biological Engineering, Seoul National University, Seoul 151-744, Republic of Korea.

The therapeutic efficacy of drugs often depends on the drug delivery carrier. For efficient delivery of therapeutic proteins, delivery carriers should enable the loading of large doses, sustained release, and retention of the bioactivity of the therapeutic proteins. Here, it is demonstrated that graphene oxide (GO) is an efficient carrier for delivery of therapeutic proteins. Titanium (Ti) substrates are coated with GO through layer-by-layer assembly of positively (GO-NH₃⁺) and negatively (GO-COO⁻) charged GO sheets. Subsequently, a therapeutic protein (bone morphogenetic protein-2, BMP-2) is loaded on the GO-coated Ti substrate with the outermost coating layer of GO-COO⁻ (Ti/GO⁻). The GO coating on Ti substrate enables loading of large doses and the sustained release of BMP-2 with preservation of the structure and bioactivity of the drug. The extent of in vitro osteogenic differentiation of human bone marrow-derived mesenchymal stem cells is higher when they are cultured on Ti/GO- carrying BMP-2 than when they are cultured on Ti with BMP-2. Eight weeks after implantation in mouse models of calvarial defects, the Ti/GO-/BMP-2 implants show more robust new bone formation compared with Ti, Ti/GO-, or Ti/BMP-2 implants. Therefore, GO is an effective carrier for the controlled delivery of therapeutic proteins, such as BMP-2, which promotes osteointegration of orthopedic or dental Ti implants.
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http://dx.doi.org/10.1002/smll.201300571DOI Listing
December 2013