Ischemic cardiomyopathies, such as myocardial infarction (MI), are a leading cause of heart failure in both men and women throughout the world. Despite timely intervention post-MI, the loss of viable myocardium can lead to global remodeling and loss of function in many patients due to the limited regenerative potential of heart tissue. Thus, there is a critical need to better understand the repair mechanisms involved and to develop new preventative and reparative therapies for treating MI and preventing progression to heart failure. Methylglyoxal (MG) is a highly reactive dicarbonyl metabolite of glycolysis and the main precursor of advanced glycation end-products (AGEs), which can cause oxidative stress and wound healing delay. MG was shown to play an important causative role in the cellular changes, adverse remodeling and functional loss of the infarcted heart. This suggests MG as a target for therapy to restore cell-ECM signaling, inhibit oxidative stress and improve cardiac function post-MI. The aim of this PhD project was to develop new biomaterial therapies that can reduce the effects of MG, decrease oxidative stress, enhance electrical conductivity and improve cardiac contractility and function post-MI. There were three primary objectives: 1) To develop an injectable antioxidant and hydrogel system for minimizing the effects of MG and promoting cardiac repair post-MI; 2) To synthesize a nanoparticle system for targeted delivery of Glyoxalase-1 (Glo1) enzyme to cardiac tissue for reducing the accumulation of MG, limiting adverse remodeling and preserving cardiac function following MI; and 3) To design a sprayable nano-therapeutic that uses surface engineered custom designed multi-armed peptide grafted nanogold for on-the-spot coating of infarcted myocardial surface for increasing contractility of the myocardium post-MI. In the first study, a fisetin-loaded collagen type I hydrogel (fisetin-HG) was injected intramyocardially in mice at 3h post-MI, and compared to fisetin-alone, hydrogel-alone, or saline treatment. The fisetin-HG treatment increased the level of glyoxalase-1 (the main MG-metabolizing enzyme), reduced MG-AGE accumulation, and decreased oxidative stress in the MI heart, which was associated with smaller scar size and improved cardiac function. Treatment with fisetin-HG also promoted neovascularization and increased the number of pro-healing macrophages in the infarct area, while reducing the number of pro-inflammatory macrophages. The second study revealed that when delivered intravenously at 3h post-MI, our Glo1-loaded nanoparticles specifically targeted the damaged cardiac tissue, led to improved cardiac function, protected cell viability and limited infarct expansion by reducing oxidative stress post-MI. Lastly, the third study showed that, when applied at 1-week post-MI, the sprayed nanogold treatment remained at the treatment site for at least 28 days with no significant off-target organ infiltration. Our results demonstrated a remarkable increase in cardiac function, muscle contractility, and myocardial electrical conductivity post-MI. Overall, these findings show that reducing MG levels through both increased activity of Glo1 and direct MG scavenging as well as increasing cardiac contractility may be a promising approach to limit adverse cardiac remodeling, prevent damage, and preserve the function of the infarcted heart

Methylglyoxal (MG), a highly reactive dicarbonyl accumulates after myocardial infarction (MI), causing adverse remodelling and cardiac dysfunction. We hypothesized that therapy using bone marrow cells (BMCs) overexpressing glyoxalase1 (Glo1), the main enzyme that metabolizes MG, injected into mouse MI model would translate into better survival of transplanted cells and improve their therapeutic effect. We found that Glo1 expression is significantly reduced at 7 days post-MI. Glo1 BMCs exposed to MG in vitro displayed greater angiogenic potential and reduced reactive oxygen species production compared to wild type (WT) BMCs. However, in the mouse MI model, Glo1 BMCs did not improve cardiac function or vascularity or reduce scar formation compared to WT BMCs and saline treatments. In conclusion, Glo1 overexpression in BMCs does not confer superior therapeutic efficacy for treating MI under the conditions tested.

Myocardial infarction (MI) persists as one of the leading causes of death worldwide. Often patients whom survive the initial injury will develop heart failure characterized by a dilated and functionally incompetent heart. Heart failure (HF) carries a worse prognosis than most cancers, and the only curative therapy to date is heart transplantation. A better understanding of the repair and remodeling processes post-MI, and the development of novel therapies are required to combat this burgeoning medical challenge. This thesis research sought to identify a novel mediator of the impaired cardiac remodeling that often occurs post-MI, and to characterize a biomaterial hydrogel therapy as a novel treatment. We investigated the role of methylglyoxal (MG), an important precursor to advanced glycation end-products (AGE), using a transgenic mouse model to over-express glyoxalase 1 (GLO1). GLO1 is the primary enzyme involved in metabolizing MG and preventing its accumulation. The role for MG and AGEs in MI and HF had been alluded to in the literature, yet no study to date has causally linked them with the loss of function and impaired remodeling of the post-MI heart. We also assessed an injectable hydrogel for the treatment of MI using a mouse model and evaluated the impact of delivery timing on its therapeutic efficacy. In this thesis, we confirmed that MG derived AGEs accumulate post-MI (Chapter 3.1). We show that preventing their accumulation, through GLO1 over-expression, mitigates the loss of function post-MI and positively influences remodeling through reducing final infarct sizes and end-systolic volumes. We demonstrate that this may possibly occur through improving the bone marrow response post-MI by restoring ECM-cell signaling. In Chapter 3.2, we present results of a study assessing the efficacy of a collagen based injectable hydrogel for the treatment of MI, and assessing the role that timing plays into the benefits associated with this therapy by studying 3 separate timepoints including 3 hours, 7 days and 14 days post-MI. We found that the injectable hydrogel preserved cardiac function and reduced infarct sizes. It also positively interacted with the host repair response by reducing chronic inflammation and cell death. The benefits of the therapy depended on when the material was delivered, and we found that the earliest timepoint (3 hours post-MI) proved most beneficial. In Chapter 3.3, we combined the knowledge gained from Chapters 3.1 and 3.2 and functionalized our hydrogel with a flavonoid, Fisetin, that has been shown to scavenge MG and increase the activity of GLO1. We show that this novel functionalized material may be able to restore some function in MI, particularly in settings of low baseline cardiac function. Taken together, the results of this thesis demonstrate that MG accumulates as a result of the ischemia and contributes to the impaired repair resolution and remodeling processes post-MI. This identifies MG as a possible novel target for the treatment of MI. Indeed, we also confirm the role that delivery timing plays into injectable hydrogels post-MI, and present promising results for a functionalized material design to intervene on MG production.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22733号 / 医博第4651号 / 新制||医||1046(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 萩原 正敏, 教授 岩田 想, 教授 渡邊 直樹 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM