Doctor of Philosophy, University Of Tokyo (2014)
Doctor of Medicine, University Of Tokyo (2005)
Background Induced pluripotent stem cells and their differentiated cardiomyocytes (iCMs) have tremendous potential as patient-specific therapy for ischemic cardiomyopathy following myocardial infarctions, but difficulties in viable transplantation limit clinical translation. Exosomes secreted from iCMs (iCM-Ex) can be robustly collected in vitro and injected in lieu of live iCMs as a cell-free therapy for myocardial infarction. Methods and Results iCM-Ex were precipitated from iCM supernatant and characterized by protein marker expression, nanoparticle tracking analysis, and functionalized nanogold transmission electron microscopy. iCM-Ex were then used in in vitro and in vivo models of ischemic injuries. Cardiac function in vivo was evaluated by left ventricular ejection fraction and myocardial viability measurements by magnetic resonance imaging. Cardioprotective mechanisms were studied by JC-1 (tetraethylbenzimidazolylcarbocyanine iodide) assay, immunohistochemistry, quantitative real-time polymerase chain reaction, transmission electron microscopy, and immunoblotting. iCM-Ex measured 140nm and expressed CD63 and CD9. iCM and iCM-Ex microRNA profiles had significant overlap, indicating that exosomal content was reflective of the parent cell. Mice treated with iCM-Ex demonstrated significant cardiac improvement post-myocardial infarction, with significantly reduced apoptosis and fibrosis. In vitro iCM apoptosis was significantly reduced by hypoxia and exosome biogenesis inhibition and restored by treatment with iCM-Ex or rapamycin. Autophagosome production and autophagy flux was upregulated in iCM-Ex groups in vivo and in vitro. Conclusions iCM-Ex improve post-myocardial infarction cardiac function by regulating autophagy in hypoxic cardiomyoytes, enabling a cell-free, patient-specific therapy for ischemic cardiomyopathy.
View details for DOI 10.1161/JAHA.119.014345
View details for PubMedID 32131688
Although ischemic heart disease is the leading cause of death worldwide, mainstay treatments ultimately fail because they do not adequately address disease pathophysiology. Restoring the microvascular perfusion deficit remains a significant unmet need and may be addressed via delivery of pro-angiogenic cytokines. The therapeutic effect of cytokines can be enhanced by encapsulation within hydrogels, but current hydrogels do not offer sufficient clinical translatability due to unfavorable viscoelastic mechanical behavior which directly impacts the ability for minimally-invasive catheter delivery. In this report, we examine the therapeutic implications of dual-stage cytokine release from a novel, highly shear-thinning biocompatible catheter-deliverable hydrogel. We chose to encapsulate two protein-engineered cytokines, namely dimeric fragment of hepatocyte growth factor (HGFdf) and engineered stromal cell-derived factor 1? (ESA), which target distinct disease pathways. The controlled release of HGFdf and ESA from separate phases of the hyaluronic acid-based hydrogel allows extended and pronounced beneficial effects due to the precise timing of release. We evaluated the therapeutic efficacy of this treatment strategy in a small animal model of myocardial ischemia and observed a significant benefit in biological and functional parameters. Given the encouraging results from the small animal experiment, we translated this treatment to a large animal preclinical model and observed a reduction in scar size, indicating this strategy could serve as a potential adjunct therapy for the millions of people suffering from ischemic heart disease.
View details for DOI 10.1016/j.cyto.2019.154974
View details for PubMedID 31978642
Background Exosomes are small extracellular vesicles that function as intercellular messengers and effectors. Exosomal cargo contains regulatory small molecules, including miRNAs, mRNAs, lncRNAs, and small peptides that can be modulated by different pathological stimuli to the cells. One of the main mechanisms of action of drug therapy may be the altered production and/or content of the exosomes. Methods and Results We studied the effects on exosome production and content by neprilysin inhibitor/angiotensin receptor blockers, sacubitril/valsartan and valsartan alone, using human-induced pluripotent stem cell-derived cardiomyocytes under normoxic and hypoxic injury model in vitro, and assessed for physiologic correlation using an ischemic myocardial injury rodent model in vivo. We demonstrated that the treatment with sacubitril/valsartan and valsartan alone resulted in the increased production of exosomes by induced pluripotent stem cell-derived cardiomyocytes in vitro in both conditions as well as in the rat plasma in vivo. Next-generation sequencing of these exosomes exhibited downregulation of the expression of rno-miR-181a in the sacubitril/valsartan treatment group. In vivo studies employing chronic rodent myocardial injury model demonstrated that miR-181a antagomir has a beneficial effect on cardiac function. Subsequently, immunohistochemical and molecular studies suggested that the downregulation of miR-181a resulted in the attenuation of myocardial fibrosis and hypertrophy, restoring the injured rodent heart after myocardial infarction. Conclusions We demonstrate that an additional mechanism of action of the pleiotropic effects of sacubitril/valsartan may be mediated by the modulation of the miRNA expression level in the exosome payload.
View details for DOI 10.1161/JAHA.119.015640
View details for PubMedID 32538237
Mitral valve chordae tendineae forces are elevated in the setting of mitral regurgitation (MR). Ring annuloplasty is an essential component of surgical repair for MR, but whether chordal forces are reduced after mitral annuloplasty has never been validated in vivo. Here, we present an extremely rare ovine case of natural, severe chronic functional MR, in which we used force-sensing fiber Bragg grating neochordae to directly measure chordal forces in the baseline setting of severe MR, as well as after successful mitral ring annuloplasty repair. Overall, our report is the first to confirm in vivo that mitral ring annuloplasty reduces elevated chordae tendineae forces associated with chronic functional MR.
View details for DOI 10.3390/jcdd7020017
View details for PubMedID 32429298
Genetic variation in the FAM13A (Family with Sequence Similarity 13 Member A) locus has been associated with several glycemic and metabolic traits in genome-wide association studies (GWAS). Here, we demonstrate that in humans, FAM13A alleles are associated with increased FAM13A expression in subcutaneous adipose tissue (SAT) and an insulin resistance-related phenotype (e.g. higher waist-to-hip ratio and fasting insulin levels, but lower body fat). In human adipocyte models, knockdown of FAM13A in preadipocytes accelerates adipocyte differentiation. In mice, Fam13a knockout (KO) have a lower visceral to subcutaneous fat (VAT/SAT) ratio after high-fat diet challenge, in comparison to their wild-type counterparts. Subcutaneous adipocytes in KO mice show a size distribution shift toward an increased number of smaller adipocytes, along with an improved adipogenic potential. Our results indicate that GWAS-associated variants within the FAM13A locus alter adipose FAM13A expression, which in turn, regulates adipocyte differentiation and contribute to changes in body fat distribution.
View details for DOI 10.1038/s41467-020-15291-z
View details for PubMedID 32193374
BACKGROUND: The diagnostic utility of cardiovascular magnetic resonance (CMR) is limited during the early stages of myocarditis. This study examined whether ferumoxytol-enhanced CMR (FE-CMR) could detect an earlier stage of acute myocarditis compared to gadolinium-enhanced CMR.METHODS: Lewis rats were induced to develop autoimmune myocarditis. CMR (3T, GE Signa) was performed at the early- (day 14, n=7) and the peak-phase (day 21, n=8) of myocardial inflammation. FE-CMR was evaluated as % myocardial dephasing signal loss on gradient echo images at 6 and 24h (6h- & 24h-FE-CMR) following the administration of ferumoxytol (300mumolFe/kg). Pre- and post-contrast T2* mapping was also performed. Early (EGE) and late (LGE) gadolinium enhancement was obtained after the administration of gadolinium-DTPA (0.5mmol/kg) on day 14 and 21. Healthy rats were used as control (n=6).RESULTS: Left ventricular ejection fraction (LVEF) was preserved at day 14 with inflammatory cells but no fibrosis seen on histology. EGE and LGE at day 14 both showed limited myocardial enhancement (EGE: 11.7±15.5%; LGE: 8.7±8.7%; both p=ns vs. controls). In contrast, 6h-FE-CMR detected extensive myocardial signal loss (33.2±15.0%, p=0.02 vs. EGE and p<0.01 vs. LGE). At day 21, LVEF became significantly decreased (47.4±16.4% vs control: 66.2±6.1%, p<0.01) with now extensive myocardial involvement detected on EGE, LGE, and 6h-FE-CMR (41.6±18.2% of LV). T2* mapping also detected myocardial uptake of ferumoxytol both at day 14 (6h R2*=299±112s-1vs control: 125±26s-1, p<0.01) and day 21 (564±562s-1, p<0.01 vs control). Notably, the myocardium at peak-phase myocarditis also showed significantly higher pre-contrast T2* (27±5ms vs control: 16±1ms, p<0.001), and the extent of myocardial necrosis had a strong positive correlation with T2* (r=0.86, p<0.001).CONCLUSIONS: FE-CMR acquired at 6h enhance detection of early stages of myocarditis before development of necrosis or fibrosis, which could potentially enable appropriate therapeutic intervention.
View details for DOI 10.1186/s12968-019-0587-7
View details for PubMedID 31842900
BACKGROUND: Manganese-enhanced MRI (MEMRI) detects viable cardiomyocytes based on the intracellular manganese uptake via L-type calcium-channels. This study aimed to quantify myocardial viability based on manganese uptake by viable myocardium in the infarct core (IC), peri-infarct region (PIR) and remote myocardium (RM) using T1 mapping before and after MEMRI and assess their association with cardiac function and arrhythmogenesis.METHODS: Fifteen female swine had a 60-minute balloon ischemia-reperfusion injury in the LAD. MRI (Signa 3T, GE Healthcare) and electrophysiological study (EPS) were performed 4?weeks later. MEMRI and delayed gadolinium-enhanced MRI (DEMRI) were acquired on LV short axis. The DEMRI positive total infarct area was subdivided into the regions of MEMRI-negative non-viable IC and MEMRI-positive viable PIR. T1 mapping was performed to evaluate native T1, post-MEMRI T1, and delta R1 (R1post-R1pre, where R1 equals 1/T1) of each territory. Their correlation with LV function and EPS data was assessed.RESULTS: PIR was characterized by intermediate native T1 (1530.5?±?75.2?ms) compared to IC (1634.7?±?88.4?ms, p?=?0.001) and RM (1406.4?±?37.9?ms, p?0.0001). Lower post-MEMRI T1 of PIR (1136.3?±?99.6?ms) than IC (1262.6?±?126.8?ms, p?=?0.005) and higher delta R1 (0.23?±?0.08?s-1) of PIR than IC (0.18?±?0.09?s-1, p?=?0.04) indicated higher myocardial manganese uptake of PIR compared to IC. Post-MEMRI T1 (r?=?-0.57, p?=?0.02) and delta R1 (r?=?0.51, p?=?0.04) of PIR correlated significantly with LVEF.CONCLUSIONS: PIR is characterized by higher manganese uptake compared to the infarct core. In the subacute phase post-IR, PIR viability measured by post-MEMRI T1 correlates with cardiac function.
View details for PubMedID 30739802
Post-operative adhesions form as a result of normal wound healing processes following any type of surgery. In cardiac surgery, pericardial adhesions are particularly problematic during reoperations, as surgeons must release the adhesions from the surface of the heart before the intended procedure can begin, thereby substantially lengthening operation times and introducing risks of haemorrhage and injury to the heart and lungs during sternal re-entry and cardiac dissection. Here we show that a dynamically crosslinked supramolecular polymer-nanoparticle hydrogel, with viscoelastic and flow properties that enable spraying onto tissue as well as robust tissue adherence and local retention in vivo for two weeks, reduces the formation of pericardial adhesions. In a rat model of severe pericardial adhesions, the hydrogel markedly reduced the severity of the adhesions, whereas commercial adhesion barriers (including Seprafilm and Interceed) did not. The hydrogels also reduced the severity of cardiac adhesions (relative to untreated animals) in a clinically relevant cardiopulmonary-bypass model in sheep. This viscoelastic supramolecular polymeric hydrogel represents a promising clinical solution for the prevention of post-operative pericardial adhesions.
View details for DOI 10.1038/s41551-019-0442-z
View details for PubMedID 31391596
Late gadolinium enhancement (LGE) with cardiac magnetic resonance (CMR) imaging has demonstrated the capability of stratifying hypertrophic cardiomyopathy (HCM). Stress perfusion test of CMR can quantify myocardial perfusion reserve (MPR), but its clinical role is not determined. The purpose of this study was to investigate the relationship between MPR and LGE in patients with HCM. A total of 61 consecutive cases underwent complete evaluation with electrocardiography and CMR [cine imaging, coronary MR angiography (MRA), and stress perfusion testing with LGE]. HCM cases were diagnosed by the Japanese conventional guideline prior to this CMR study. Mild LVH was defined as more than 13 mm in maximum LV wall thickness at end diastole on the cine imaging of the CMR. MPR was calculated as the ratio of stress/rest myocardial blood flow using an intensity curve on the stress perfusion test. Cases with ischemic heart disease were excluded from the study based on clinical history and coronary MRA. There were 37 HCM and 24 mild LVH cases (average age: 60.5 ± 10.9 vs. 64.8 ± 10.8; male: 62.2 vs. 75.0%, respectively, non-significant). MPR in HCM was lower than in LVH (1.5 ± 0.5 vs. 2.2 ± 0.9, p < 0.001) and normal subjects (2.4 ± 0.9, p < 0.001). MPR in HCM with LGE (N = 34) was lower than in HCM without LGE (N = 3) (1.4 ± 0.5 vs. 2.1 ± 0.2, p = 0.014). Multiple regression analysis verified that LGE was the strongest predictor of MPR among multiple clinical parameters, including LVH, LV dysfunction (ejection fraction < 50%), and the presence of negative T wave (p < 0.001). MPR was impaired in HCM with LGE compared with HCM without LGE. The clinical role of MPR on CMR needs to be clarified by further research.
View details for PubMedID 29168014
View details for PubMedID 28775009
Inflammation plays a significant role in a wide range of cardiovascular diseases (CVDs). The numerous implications of inflammation in all steps of CVDs, including initiation, progression and complications, have prompted the emergence of noninvasive imaging modalities as diagnostic, prognostic and monitoring tools. In this review, we first synthesize the existing evidence on the role of inflammation in vascular and cardiac diseases, in order to identify the main targets used in noninvasive imaging. We chose to focus on positron emission tomographic (PET) and magnetic resonance imaging (MRI) studies, which offer the greatest potential of translation and clinical application. We detail the main preclinical and clinical studies in the following CVDs: coronary and vascular atherosclerosis, abdominal aortic aneurysms, myocardial infarction, myocarditis, and acute heart transplant rejection. We highlight the potential complementary roles of these imaging modalities, which are currently being studied in the emerging technology of PET/MRI. Finally, we provide a perspective on innovations and future applications of noninvasive imaging of cardiovascular inflammation. (Circ J 2016; 80: 1269-1277).
View details for DOI 10.1253/circj.CJ-16-0224
View details for PubMedID 27151335
The renin angiotensin system (RAS) plays an important role in the pathogenesis of cardiovascular diseases and inflammation. Myocarditis is an inflammatory disease of the heart, and the role of the RAS in its pathophysiology is unknown. Because the direct renin inhibitor, aliskiren, is thought to block RAS completely, we investigated the cardioprotective effect of aliskiren in mice with experimental autoimmune myocarditis (EAM).A cardiac ?-myosin heavy chain peptide was injected in mice on days 0 and 7. Aliskiren 25mg/kg per day (n=10) or vehicle (n=10) was administered to EAM mice starting on day 0 and the animals were killed on day 21.Aliskiren significantly prevented the progression of left ventricular wall thickening in EAM hearts compared to the vehicle-treated group. Histologically, the inflammatory cell infiltration and fibrosis area ratios in the aliskiren-treated group were lower than that in the vehicle-treated group. Immunohistochemistry revealed that aliskiren suppressed CD4 positive cell infiltration in EAM hearts compared to vehicle. Moreover, aliskiren decreased mRNA levels of interleukin (IL)-2, interferon-?, tumor necrosis factor-?, and collagen 1. In vitro study showed that aliskiren inhibited T cell proliferation and IL-2 production induced by myosin stimulation.Our results suggest that aliskiren ameliorates EAM by suppressing T-cell activation and inflammatory cytokines, and has potential as a treatment for myocarditis.
View details for DOI 10.1016/j.jjcc.2015.09.008
View details for PubMedID 26475067
Reactive oxygen species (ROS) such as superoxide anion and hydrogen peroxide are produced highly in myocarditis. ROS, which not only act as effectors for pathogen killing but also mediate signal transduction in the stress responsive pathways, are closely related with both innate and adaptive immunity. On the other hand, oxidative stress overwhelming the capacity of anti-oxidative system generated in severe inflammation has been suggested to damage tissues and exacerbate inflammation. Oxidative stress worsens the autoimmunological process of myocarditis, and suppression of the anti-oxidative system and long-lasting oxidative stress could be one of the pathological mechanisms of cardiac remodeling leading to inflammatory cardiomyopathy. Oxidative stress is considered to be one of the promising treatment targets of myocarditis. Evidences of anti-oxidative treatments in myocarditis have not been fully established. Basic strategies of anti-oxidative treatments include inhibition of ROS production, activation of anti-oxidative enzymes and elimination of generated free radicals. ROS are produced by mitochondrial respiratory chain reactions and enzymes including NADPH oxidases, cyclooxygenase, and xanthine oxidase. Other systems involved in inflammation and stress response, such as NF-?B, Nrf2/Keap1, and neurohumoral factors also influence oxidative stress in myocarditis. The efficacy of anti-oxidative treatments could also depend on the etiology and the phases of myocarditis. We review in this article the pathological significance of ROS and oxidative stress, and the potential anti-oxidative treatments in myocarditis.
View details for DOI 10.2174/1381612822666151222160559
View details for PubMedID 26696256
Mechanisms of cardiac dysfunction in myocarditis have not been fully elucidated. Though it remains controversial whether angiogenesis is beneficial or harmful in inflammatory disease, significant vascular destruction might possibly impair cardiac function in myocarditis. The prolyl hydroxylase domain-containing protein (PHD) inhibitor is a potential drug for promoting angiogenesis as it stabilizes hypoxia inducible transcription factor (HIF). The authors examine whether the PHD inhibitor TM6008 could affect cardiac function by promoting angiogenesis in experimental autoimmune myocarditis (EAM).EAM was induced on BALB/c mice by immunizing them with a synthesized ? myosin heavy-chain peptide. Every day, 200 mg/kg of TM6008 or vehicle was administered orally.TM6008 improved left ventricular ejection fraction significantly on the 21st day of EAM. Though TM6008 did not affect the severity of myocardial cell infiltration, it tended to reduce cardiac fibrosis. Immunohistochemistry showed that CD31-positive blood vessels were preserved in the TM6008 group compared to the control group. Immunoblotting revealed that TM6008 increased the expression of HIF-1?, HIF-2? and vascular endothelial growth factor in myocarditis.Inhibition of PHD could ameliorate cardiac dysfunction in EAM, partially through promoting neovascularization. Relief of tissue hypoxia via neovascularization could improve cardiac function in myocarditis.
View details for DOI 10.1517/13543784.2014.855196
View details for PubMedID 24205804
We report a rare case of fulminant myocarditis that was considered to have smoldered for a few months before it finally exteriorized. An 80-year-old man had had two episodes of mild congestive heart failure with preserved ejection function (HFPEF) within 3 months before he was finally admitted for the treatment of rapidly progressive heart failure. Cardiac function deteriorated remarkably on the final admission. Extracorporeal cardiopulmonary support was used because of pump failure and conduction disability, however, the patient died on the 16th day. Endomyocardial biopsy revealed numerous inflammatory infiltrates in myocardium compatible with fulminant myocarditis. However, advanced fibrosis and increased number of B lymphocytes and plasma cells found in the present case were not typical for fulminant myocarditis. Considering several distinctive findings in clinical and laboratory findings together, two preceding HFPEF episodes were highly likely to be associated with myocarditis.
View details for DOI 10.4021/cr261w
View details for PubMedID 28352425
View details for PubMedCentralID PMC5358218
Clinical importance of hyponatremia in ST-elevation acute myocardial infarction (STEMI) in the era of primary intervention has not been fully understood. The aim of this study was to investigate the impact of hyponatremia on outcomes in patients with STEMI and secondarily to investigate the contribution of arginine vasopressin (AVP) to hyponatremia in STEMI.Hyponatremia was defined as a sodium concentration <136 mmol/L at 72h after hospitalization. First, the short-term (in-hospital mortality or congestive heart failure (CHF)) and long-term prognosis (cardiac death, re-admission for CHF) in STEMI patients was conducted. Second, the relationship between serum sodium level and plasma AVP was investigated. In hyponatremic patients the incidence of in-hospital heart failure was significantly greater (P=0.0018), long-term cardiac death was a higher trend (17.2% vs. 6.3%, P=0.19) and re-admission due to CHF was significantly more frequent (20.7% vs. 4.5%, P=0.0024). Plasma AVP level was higher in the hyponatremia group (4.5 vs. 2.7 pg/ml, P=0.003), and it had a negative correlation with serum sodium level (r=-0.28, P=0.02).Hyponatremia was frequently found in the early phase of STEMI, and associated with heart failure in both short- and long-term outcomes. Non-osmotic secretion of AVP could be involved in hyponatremia in STEMI patients.
View details for DOI 10.1253/circj.cj-10-0945
View details for PubMedID 21617327