Ji Hye Jung

Decreased level and defective function of circulating endothelial progenitor cells in children with moyamoya disease

Circulating endothelial progenitor cells (EPCs) play an important role in physiological and pathological neovascularization and may be involved in attenuating ischemic diseases. This study aimed to characterize circulating EPCs in moyamoya disease (MMD), one of the most common pediatric cerebrovascular diseases. Twenty‐eight children with MMD prior to any surgical treatment and 12 healthy volunteers were recruited. Peripheral blood mononuclear cells (PBMNCs) were isolated and cultured in endothelial cell growth medium. Temporal change of phenotype of cells was analyzed on days 0 and 7. The formation of EPC clusters was evaluated on day 7. The CD34+, CD133+, and KDR+ cells, and the number of EPC clusters was significantly reduced in children with MMD. In controls, CD34+ cells were significantly decreased on day 7 compared with day 0, but in MMD they were only slightly decreased. The change in KDR+ cells on day 7 compared with day 0 was the reverse of that for CD34+ cells. Functional assay of EPC demonstrated less tube formation and increased senescent‐like phenotype in children with MMD. Analysis of the circulating EPCs of MMD children reveals decreased level and defective function. This study suggests that circulating EPCs may be associated with MMD pathogenesis.

Exosomes Generated From iPSC-Derivatives: New Direction for Stem Cell Therapy in Human Heart Diseases

Cardiovascular disease (CVD) is the leading cause of death in modern society. The adult heart innately lacks the capacity to repair and regenerate the damaged myocardium from ischemic injury. Limited understanding of cardiac tissue repair process hampers the development of effective therapeutic solutions to treat CVD such as ischemic cardiomyopathy. In recent years, rapid emergence of induced pluripotent stem cells (iPSC) and iPSC-derived cardiomyocytes presents a valuable opportunity to replenish the functional cells to the heart. The therapeutic effects of iPSC-derived cells have been investigated in many preclinical studies. However, the underlying mechanisms of iPSC-derived cell therapy are still unclear, and limited engraftment of iPSC-derived cardiomyocytes is well known. One facet of their mechanism is the paracrine effect of the transplanted cells. Microvesicles such as exosomes secreted from the iPSC-derived cardiomyocytes exert protective effects by transferring the endogenous molecules to salvage the injured neighboring cells by regulating apoptosis, inflammation, fibrosis, and angiogenesis. In this review, we will focus on the current advances in the exosomes from iPSC derivatives and discuss their therapeutic potential in the treatment of CVD.

Tissue Expression of Manganese Superoxide Dismutase Is a Candidate Prognostic Marker for Glioblastoma

Background: Characterization of a rare subgroup of glioblastoma patients who survive for more than 3 years (long-term survival glioblastoma, LTSGBL, patients) may be helpful to identify prognostic factors. Materials and Methods: A molecular-profiling proteomic approach using two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to identify prognostic factors associated with glioblastoma by comparing frozen tumor tissue from LTSGBL patients with matched samples from short-term survival glioblastoma (STSGBL) patients. Western blot (WB) analysis, reverse-transcriptase polymerase chain reaction (RT-PCR) and immmunohistochemical (IHC) staining were used for confirmation. Results: Among most candidate spots identified by 2-DE, lack of overexpression of manganese superoxide dismutase (MnSOD) in LTSGBL samples was consistently observed using WB and RT-PCR. Conclusion: These results suggest that MnSOD expression level in tumor tissue is a candidate marker for the prognosis of glioblastoma patients.

CXCR2 and Its Related Ligands Play a Novel Role in Supporting the Pluripotency and Proliferation of Human Pluripotent Stem Cells

Basic fibroblast growth factor (bFGF) is a crucial factor sustaining human pluripotent stem cells (hPSCs). We designed this study to search the substitutive factors other than bFGF for the maintenance of hPSCs by using human placenta-derived conditioned medium without exogenous bFGF (hPCCM-), containing chemokine (C-X-C motif) receptor 2 (CXCR2) ligands, including interleukin (IL)-8 and growth-related oncogene α (GROα), which were developed on the basis of our previous studies. First, we confirmed that IL-8 and/or GROα play independent roles to preserve the phenotype of hPSCs. Then, we tried CXCR2 blockage of hPSCs in hPCCM- and verified the significant decrease of pluripotency-associated genes expression and the proliferation of hPSCs. Interestingly, CXCR2 suppression of hPSCs in mTeSR™1 containing exogenous bFGF decreased the proliferation of hPSCs while maintaining pluripotency characteristics. Lastly, we found that hPSCs proliferated robustly for more than 35 passages in hPCCM- on a gelatin substratum. Higher CXCR2 expression of hPSCs cultured in hPCCM- than those in mTeSR™1 was observable. Our findings suggest that CXCR2 and its related ligands might be novel factors comparable to bFGF supporting the characteristics of hPSCs and hPCCM- might be useful for the maintenance of hPSCs as well as for the accurate evaluation of CXCR2 role in hPSCs without the confounding influence of exogenous bFGF.

Mel-18, a mammalian Polycomb gene, regulates angiogenic gene expression of endothelial cells.

Mel-18 is a mammalian homolog of Polycomb group (PcG) genes. Microarray analysis revealed that Mel-18 expression was induced during endothelial progenitor cell (EPC) differentiation and correlates with the expression of EC-specific protein markers. Overexpression of Mel-18 promoted EPC differentiation and angiogenic activity of ECs. Accordingly, silencing Mel-18 inhibited EC migration and tube formation in vitro. Gene expression profiling showed that Mel-18 regulates angiogenic genes including kinase insert domain receptor (KDR), claudin 5, and angiopoietin-like 2. Our findings demonstrate, for the first time, that Mel-18 plays a significant role in the angiogenic function of ECs by regulating endothelial gene expression.

CXCR2 Inhibition in Human Pluripotent Stem Cells Induces Predominant Differentiation to Mesoderm and Endoderm Through Repression of mTOR, β-Catenin, and hTERT Activities

On the basis of our previous report verifying that chemokine (C-X-C motif) receptor 2 (CXCR2) ligands in human placenta-derived cell conditioned medium (hPCCM) support human pluripotent stem cell (hPSC) propagation without exogenous basic fibroblast growth factor (bFGF), this study was designed to identify the effect of CXCR2 manipulation on the fate of hPSCs and the underlying mechanism, which had not been previously determined. We observed that CXCR2 inhibition in hPSCs induces predominant differentiation to mesoderm and endoderm with concomitant loss of hPSC characteristics and accompanying decreased expression of mammalian target of rapamycin (mTOR), β-catenin, and human telomerase reverse transcriptase (hTERT). These phenomena are recapitulated in hPSCs propagated in conventional culture conditions, including bFGF as well as those in hPCCM without exogenous bFGF, suggesting that the action of CXCR2 on hPSCs might not be associated with a bFGF-related mechanism. In addition, the specific CXCR2 ligand growth-related oncogene α (GROα) markedly increased the expression of ectodermal markers in differentiation-committed embryoid bodies derived from hPSCs. This finding suggests that CXCR2 inhibition in hPSCs prohibits the propagation of hPSCs and leads to predominant differentiation to mesoderm and endoderm owing to the blockage of ectodermal differentiation. Taken together, our results indicate that CXCR2 preferentially supports the maintenance of hPSC characteristics as well as facilitates ectodermal differentiation after the commitment to differentiation, and the mechanism might be associated with mTOR, β-catenin, and hTERT activities.

A Novel Culture Model for Human Pluripotent Stem Cell Propagation on Gelatin in Placenta-conditioned Media.

The propagation of human pluripotent stem cells (hPSCs) in conditioned medium derived from human cells in feeder-free culture conditions has been of interest. Nevertheless, an ideal humanized ex vivo feeder-free propagation method for hPSCs has not been developed; currently, additional exogenous substrates including basic fibroblast growth factor (bFGF), a master hPSC-sustaining factor, is added to all of culture media and synthetic substrata such as Matrigel or laminin are used in all feeder-free cultures. Recently, our group developed a simple and efficient protocol for the propagation of hPSCs using only conditioned media derived from the human placenta on a gelatin-coated dish without additional exogenous supplementation or synthetic substrata specific to hPSCs. This protocol has not been reported previously and might enable researchers to propagate hPSCs efficiently in humanized culture conditions. Additionally, this model obviates hPSC contamination risks by animal products such as viruses or unknown proteins. Furthermore, this system facilitates easy mass production of hPSCs using the gelatin coating, which is simple to handle, dramatically decreases the overall costs of ex vivo hPSC maintenance.

Novel MRI Contrast from Magnetotactic Bacteria to Evaluate In Vivo Stem Cell Engraftment

Although human induced pluripotent stem cells (iPSCs) and their derivatives have great potential for the treatment of heart failure. The therapeutic benefit is limited by translational challenges of stem cells such as cell engraftment. Thus, a robust in vivo imaging technology is indispensable to advance the clinical implementation of stem cell therapy. While no available imaging technology meets the requirement for in vivo stem cell tracking, MRI is a highly promising tool due to its high spatial resolution, temporal resolution, and tissue contrast; yet, this modality lacks sensitivity. Superparamagnetic iron oxide particles (SPIONs) addresses this critical imaging issue and have been used as an MRI contrast agent for stem cell tracking. However, their critical limitation is the inability to evaluate cell viability as SPIONs remain in the tissue long after the death of transplanted cells. To address this shortcoming of SPIONs, the novel magneto-endosymbiont-based (MEs) contrast agent was developed (Magnelle®, Bell Biosystems, Inc., South SF, CA). The MEs utilize the magnetosome biosynthesized by magnetotactic bacteria (MTB), a specific intracellular structure containing inorganic magnetic iron crystals (magnetite or greigite). Having superparamagnetic property like SPIONs, MEs can be detected on T2* weighted imaging. MEs have high safety profile and do not interfere with the functions of transfected cells. Unlike SPIONs, the antiginecity of the MEs are readily recognized and removed from macrophages quickly after the death of labeled cells, eliminating signals from dead cells. In the previous study from our group, iPSC derived cardiomyocytes were labeled with MEs and detected successfully on MRI after transplantation into the heart. In vivo ME signals corresponded with luciferase-based bioluminescence imaging (BLI) of the transplanted cell viability. In conclusion, ME is a novel MRI contrast agent for in vivo cellular tracking that allows accurate longitudinal visualization of the engrafted cells.

EXOSOMES PRODUCED BY HUMAN AMNIOTIC MESENCHYMAL STEM CELL-DERIVED INDUCED PLURIPOTENT STEM CELLS MODULATE IMMUNE RESPONSE IN MURINE MYOCARDIAL INJURY MODEL

Induced pluripotent stem cells (iPSCs) produce exosomes, which underlie the restorative effects in the injured myocardium. These nanoscale vesicles attenuate the innate immune response in the post-injury myocardium. The secretome of the human amniotic mesenchymal stem cells (hAMSCs) are known to

EXOSOMAL MIR-106A-363 CLUSTER FROM THE HYPOXIC HUMAN IPSC-DERIVED CARDIOMYOCYTES RESTORE THE ISCHEMIC MYOCARDIUM

Induced pluripotent stem cells (iPSCs) and iPSC-derived cardiomyocytes (iCMs) are promising therapeutic approach to salvage the injured myocardium; however, suboptimal in vivo stem cell engraftment and tumorigenicity impede clinical translation. Recent evidence indicates that the stem cells exert