Geum Hee Choi

Potential role of vascular smooth muscle cell-like progenitor cell therapy in the suppression of experimental abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) are a growing problem worldwide, yet there is no known medical therapy. The pathogenesis involves degradation of the elastic lamina by two combined mechanisms: increased degradation of elastin by matrix metalloproteinases (MMP) and decreased formation of elastin due to apoptosis of vascular smooth muscle cells (VSMC). In this study, we set out to examine the potential role of stem cells in the attenuation of AAA formation by inhibition of these pathogenetic mechanisms. Muscle-derived stem cells from murine skeletal muscles were isolated and stimulated with PDGF-BB in vitro for differentiation to VSMC-like progenitor cells (VSMC-PC). These cells were implanted in to elastase-induced AAAs in rats. The cell therapy group had decreased rate of aneurysm formation compared to control, and MMP expression at the genetic, protein and enzymatic level were also significantly decreased. Furthermore, direct implantation of VSMC-PCs in the intima of harvested aortas was visualized under immunofluorescent staining, suggesting that these cells were responsible for the inhibition of MMPs and consequent attenuation of AAA formation. These results show a promising role of stem cell therapy for the treatment of AAAs, and with further studies, may be able to reach clinical significance.

Muscle-Derived Stem Cells Promote Angiogenesis and Attenuate Intimal Hyperplasia in Different Murine Vascular Disease Models

Muscle-derived stem cells (MDSCs) are known to promote angiogenesis, but have never been studied in vascular diseases. We differentiated MDSCs into endothelial lineage cells in vitro by stimulation with shear stress and vascular endothelial growth factor. Such differentiated MDSCs (diff-MDSC) showed strong angiogenic potential in vitro. When tested in ischemic hindlimbs of mice, diff-MDSCs increased perfusion and decreased necrosis of the ischemic limbs, by promoting new vessel formation and by upregulating genes involved in endothelial expression. Such effects were not observed with native MDSCs (without endothelial stimulation in vitro). Diff-MDSCs were also injected into carotid arteries of rats after balloon denudation of the intima layer to induce intimal hyperplasia. The cell-treated group had significantly reduced intima-to-media thickness ratio compared to control, thus attenuating intimal hyperplasia by early re-endothelialization of the intima layer. Our findings suggest that MDSCs are a potential source of stem cell therapy for treatment of various vascular diseases, by inducing angiogenesis to improve perfusion in sites of ischemia, and by preventing intimal hyperplasia in sites of vessel injury.

Modification of a Rodent Hindlimb Model of Secondary Lymphedema: Surgical Radicality versus Radiotherapeutic Ablation

Secondary lymphedema is an intractable disease mainly caused by damage of the lymphatic system during surgery, yet studies are limited by the lack of suitable animal models. The purpose of this study was to create an improved model of secondary lymphedema in the hindlimbs of rodents with sustained effects and able to mimic human lymphedema. This was achieved by combining previously reported surgical methods and radiation to induce chronic lymphedema. Despite more radical surgical destruction of superficial and deep lymphatic vessels, surgery alone was not enough to sustain increased hindlimb volume. Radiotherapy was necessary to prolong these effects, with decreased lymphatic flow on lymphoscintigraphy, but hindlimb necrosis occurred after 4 weeks due to radiation toxicity. The applicability of this model for studies of therapeutic lymphangiogenesis was subsequently tested by injecting muscle-derived stem cells previously cocultured with the supernatant of human lymphatic endothelial cells in vitro. There was a tendency for increased lymphatic flow which significantly increased lymphatic vessel formation after cell injection, but attenuation of hindlimb volume was not observed. These results suggest that further refinement of the rodent hindlimb model is needed by titration of adequate radiation dosage, while stem cell lymphangiogenesis seems to be a promising approach.

Recent Advances in the Development of Experimental Animal Models Mimicking Human Aortic Aneurysms.

Aortic aneurysm is a common and life-threatening disease that can cause death from rupture. Current therapeutic options are limited to surgical or endovascular procedures because no pharmacological approaches have been proven to decrease the chance of expansion or rupture. The best approach to the management of aortic aneurysm would be the understanding and prevention of the processes involved in disease occurrence, progression, and rupture. There is a need for animal models that can reproduce the pathophysiological features of human aortic aneurysm, and several such models have been studied. This review will emphasize recent advances in animal models used in the determination of mechanisms and treatments of aortic aneurysms.

Tracking the Fate of Muscle-derived Stem Cells: an Insight into the Distribution and Mode of Action

Purpose: To examine the fate of muscle-derived stem cells (MDSC) after injection into different host conditions and provide an insight for their mechanism of action. Materials and Methods: MDSCs differentiated in vitro towards the endothelial lineage and transfected with lentivirus tagged with green fluorescent protein (GFP) were injected into two animal models mimicking vascular diseases: hindlimb ischemia and carotid injury models. Injected cells were tracked at the site of injection and in remote organs by harvesting the respective tissues at different time intervals and performing immunofluorescent histological analyses. Stem cell survival was quantified at the site of injection for up to 4 weeks. Results: MDSCs were successfully tagged with fluorescent material GFP and showed successful implantation into the respective injection sites. These cells showed a higher affinity to implant in blood vessel walls as shown by double fluorescent co-stain with CD31. Quantification of stem cell survival showed a timede pendent decrease from day 3 to 4 weeks (survival rate normalized against day 3 was 72.0% at 1 week, 26.8% at 2 weeks and 2.4% at 4 weeks). Stem cells were also found in distant organs, especially the kidneys and liver, which survived up to 4 weeks. Conclusion: MDSCs were successfully tracked in different vascular disease models, and their fate was assessed in terms of cell survival and distribution. Better understanding of the donor cell properties, including their interaction with the host conditions and their mechanism of action, are needed to enhance cell survival and achieve improved outcomes.

BAIBA Attenuates the Expression of Inflammatory Cytokines and Attachment Molecules and ER Stress in HUVECs and THP-1 Cells

Objective: β-Aminoisobutyric acid (BAIBA), a myokine, is a thymine catabolite that is induced during exercise, leading to browning of white fat, hepatic fatty acid oxidation, and suppression of hepatic lipogenesis. However, the effects of BAIBA on the progression of atherosclerosis remain unclear. Methods: We performed a Western blot analyses to determine various protein expression. ELISAs (enzyme-linked immunosorbent assays), cell adhesion assays, and cell viability assays were also performed on human umbilical vascular endothelial cells (HUVECs) and human monocytes (THP-1 cells). Results: In the current study, we demonstrate that BAIBA suppresses atherosclerotic reactions caused by lipopolysaccharide (LPS) treatment via an AMPK-dependent pathway. Treatment of HUVECs and THP-1 cells with BAIBA inhibited the LPS-induced phosphorylation of nuclear factor-κB (NFκB) and the secretion of proinflammatory cytokines. In HUVECs, expression of adhesion molecules and LPS-stimulated adhesion of THP-1 cells to the endothelium were significantly decreased after BAIBA treatment. Furthermore, LPS-induced endoplasmic reticulum (ER) stress and cell toxicity were significantly decreased after BAIBA treatment of HUVECs. Notably, all of these proatherosclerotic effects were fully abrogated by treatment with small interfering RNA targeting AMPK. Conclusion: BAIBA ameliorates LPS-induced atherosclerotic reactions via AMPK-mediated suppression of inflammation and ER stress.

Maresin 1 attenuates pro-inflammatory reactions and ER stress in HUVECs via PPARα-mediated pathway

The current study was designed to investigate the therapeutic effects of Maresin 1 (MAR1) on atherosclerotic response. Human monocytes THP-1 and human umbilical vein endothelial cells (HUVECs) were used to investigate the effects of MAR1 on lipopolysaccharide (LPS)-induced inflammation and apoptosis. In this study, we found that MAR1 induces peroxisome proliferator-activated receptor alpha (PPARα) expression. We also demonstrated that MAR1 suppresses atherosclerotic reactions caused by LPS treatment via a PPARα-dependent pathway. MAR1 treatment inhibited LPS-induced phosphorylation of nuclear factor kappa B (NF-κB) and secretion of pro-inflammatory cytokines in HUVECs and THP-1 cells. In HUVEC cells, expression of adhesion molecules and LPS-stimulated adhesion of THP-1 cells to the endothelium were significantly decreased after MAR1 treatment. Furthermore, LPS-induced endoplasmic reticulum (ER) stress and cell apoptosis was significantly decreased after MAR1 treatment of HUVECs. MAR1 also led to a dose-dependent increase in oxygen-regulated protein 150 (ORP150) expression which is responsible for the inhibition of ER stress. Notably, all of the pro-atherosclerotic effects were completely abrogated by treatment with small interfering (si) RNA targeting PPARα. In conclusion, MAR1 ameliorates LPS-induced atherosclerotic reactions via PPARα-mediated suppression of inflammation and ER stress.Graphical abstract

Chitinase-3-like protein 1 ameliorates atherosclerotic responses via PPARδ-mediated suppression of inflammation and ER stress

Chitinase 3‐like protein 1 (CHI3L1) is a novel biomarker of systemic inflammation. However, the effects of CHI3L1 on the progression of atherosclerosis remain to be explored. In the current study, we found that CHI3L1 induces peroxisome proliferator‐activated receptor delta (PPARδ) expression, leading to a dose‐dependent increase in oxygen‐regulated protein 150 (ORP150) expression. We demonstrated that CHI3L1 suppresses atherosclerotic reactions caused by LPS treatment via a PPARδ‐dependent pathway. Treatment of HUVECs and THP‐1 cells with CHI3L1 suppressed LPS‐induced phosphorylation of nuclear factor kappa B (NFκB) and secretion of proinflammatory cytokines such as TNFα and MCP‐1. In HUVECs, expression of adhesion molecules and LPS‐stimulated adhesion of THP‐1 cells to the endothelium were significantly reduced after CHI3L1 treatment. Furthermore, LPS‐induced endoplasmic reticulum (ER) stress and cell apoptosis were significantly ameliorated after treatment of HUVECs with CHI3L1. Particularly, all of the pro‐atherosclerotic effects were significantly mitigated by treatment with small interfering (si) RNA for PPARδ. In conclusion, CHI3L1 ameliorates LPS‐induced atherosclerotic reactions via PPARδ‐mediated suppression of inflammation and ER stress.

Fibronectin Type III Domain Containing 4 attenuates hyperlipidemia-induced insulin resistance via suppression of inflammation and ER stress through HO-1 expression in adipocytes

Although Fibronectin Type III Domain Containing 4 (FNDC4) has been reported to be involved in the modulation of inflammation in macrophages, its effects on inflammation and insulin resistance in adipose tissue are unknown. In the current study, we investigated the effects of FNDC4 on hyperlipidemia-mediated endoplasmic reticulum (ER) stress, inflammation, and insulin resistance in adipocytes via the AMP-activated protein kinase (AMPK)/heme oxygenase-1 (HO-1)-mediated pathway. Hyperlipidemia-induced nuclear factor κB (NFκB), inhibitory κBα (IκBα) phosphorylation, and pro-inflammatory cytokines such as TNFα and MCP-1 were markedly mitigated by FNDC4. Furthermore, FNDC4 treatment attenuated impaired insulin signaling in palmitate-treated differentiated 3T3-L1 cells and in subcutaneous adipose tissue of HFD-fed mice. FNDC4 administration ameliorated glucose intolerance and reduced HFD-induced body weight gain in mice. However, FNDC4 treatment did not affect calorie intake. Additionally, treatment with FNDC4 attenuated hyperlipidemia-induced phosphorylation or expression of ER stress markers such as IRE-1, eIF2α, and CHOP in 3T3-L1 adipocytes and in subcutaneous adipose tissue of mice. FNDC4 treatment stimulated AMPK phosphorylation and HO-1 expression in 3T3-L1 adipocytes and in subcutaneous adipose tissue of mice. siRNA-mediated suppression of AMPK and HO-1 abrogated the suppressive effects of FNDC4 on palmitate-induced ER stress, inflammation, and insulin resistance. In conclusion, our results show that FNDC4 ameliorates insulin resistance via AMPK/HO-1-mediated suppression of inflammation and ER stress, indicating that FNDC4 may be a novel therapeutic agent for treating insulin resistance and type 2 diabetes.