Cortical bone stem cell-derived exosomes' therapeutic effect on myocardial ischemia-reperfusion and cardiac remodeling

Heart failure is the one of the leading causes of death in the United States. Heart failure is a complex syndrome caused by numerous diseases, including severe myocardial infarction (MI). MI occurs after an occlusion of a cardiac artery causing downstream ischemia. MI is followed by cardiac remodeling involving extensive remodeling and fibrosis, which, if the original insult is severe or prolonged, can ultimately progress into heart failure. There is no "cure" for heart failure because therapies to regenerate dead tissue are not yet available. Previous studies have shown that in both post-MI and post-ischemia-reperfusion (I/R) models of heart failure, administration of cortical bone stem cell (CBSC) treatment leads to a reduction in scar size and improved cardiac function. Our first study investigated the ability of mouse CBSC-derived exosomes (mCBSC-dEXO) to recapitulate mouse CBSCs (mCBSC) therapeutic effects in a 24-h post-I/R model. This study showed that injection of mCBSCs and mCBSC-dEXOs into the ischemic region of an infarct had a protective effect against I/R injury. mCBSC-dEXOs recapitulated the effects of CBSC treatment post-I/R, indicating exosomes are partly responsible for CBSC's beneficial effects. To examine if exosomes decrease fibrotic activation, adult rat ventricular fibroblasts (ARVFs) and adult human cardiac fibroblasts (NHCFs) were treated with transforming growth factor β (TGFβ) to activate fibrotic signaling before treatment with mCBSC- and human CBSC (hCBSC)-dEXOs. hCBSC-dEXOs caused a 100-fold decrease in human fibroblast activation. To further understand the signaling mechanisms regulating the protective decrease in fibrosis, we performed RNA sequencing on the NHCFs after hCBSC-dEXO treatment. The group treated with both TGFβ and exosomes showed a decrease in small nucleolar RNA (snoRNA), known to be involved with ribosome stability.NEW & NOTEWORTHY Our work is noteworthy due to the identification of factors within stem cell-derived exosomes (dEXOs) that alter fibroblast activation through the hereto-unknown mechanism of decreasing small nucleolar RNA (snoRNA) signaling within cardiac fibroblasts. The study also shows that the injection of stem cells or a stem-cell-derived exosome therapy at the onset of reperfusion elicits cardioprotection, emphasizing the importance of early treatment in the post-ischemia-reperfusion (I/R) wounded heart.

Postsurgery echocardiography can predict the amount of ischemia-reperfusion injury and the resultant scar size

Despite advances in the diagnosis and treatment of ischemic heart disease (IHD), it remains the leading cause of death globally. Thus, there is a need to investigate the underlying pathophysiology and develop new therapies for the prevention and treatment of IHD. Murine models are widely used in IHD research because they are readily available, relatively inexpensive, and can be genetically modified to explore mechanistic questions. Ischemia-reperfusion (I/R)-induced myocardial infarction in mice is produced by the blockage followed by reperfusion of the left anterior descending branch (LAD) to imitate human IHD disease and its treatment. This I/R model can be widely used to investigate the potential reparative effect of putative treatments in the setting of reperfusion. However, the surgical technique is demanding and can produce an inconsistent amount of damage, which can make identification of treatment effects challenging. Therefore, determining which hearts have been significantly damaged by I/R is an important consideration in studies designed to either explore the mechanisms of disrupted function or test possible therapies. Noninvasive echocardiography (ECHO) is often used to determine structural and functional changes in the mouse heart following injury. In the present study, we determined that ECHO performed 3 days post I/R surgery could predict the permanent injury produced by the ischemic insult.NEW & NOTEWORTHY We believe our work is noteworthy due to its creation of standards for early evaluation of the level of myocardial injury in mouse models of ischemia-reperfusion. This improvement to study design could reduce the sample sizes used in evaluating therapeutics and lead to increased confidence in conclusions drawn regarding the therapeutic efficacy of treatments tested in these translational mouse models.

Abstract 554: Mechanism of Action for the Beneficial Effects of Cortical Bone Stem Cells on the Heart After Myocardial Infarction

Rationale: Myocardial infarction (MI) causes the death of a portion of the heart and can lead to adverse remodeling that results in poor cardiac pump function and heart failure. We have previously shown that a novel stem cell type, cortical bone stem cells (CBSCs), causes improved repair of cardiac tissue after MI. When injected into the infarct border zone in both mouse and pig hearts, CBSCs reduced infarct size and induced neovascularization via a largely paracrine manner.

Objectives: This study investigates the mechanism involved in the angiogenesis alterations implemented by CBSCs, in particular the wound-healing of endothelial cells. Our goal was to comprehend how mCBSCs affected cardiac repair in an inflammatory environment.

Methods and Results: We performed scratch assays and tubule formation (TF) assays on human umbilical vein endothelial cells (HUVECs) and cardiac endothelial cells (CECs) in mCBSC CM and media controls, and in the presence of pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α. Both HUVECs and CECs show reduced cell migration and reduced TF. TF was rescued when the cells were plated on Matrigel. We investigated the angiogenesis-related cytokines present within both the mCBSC CM and CM-treated HUVECs and CECs via angiogenesis dot blots. We discovered a significant increase of CXCL-10 and Endostatin/Collagen XVIII relative to murine embryonic fibroblast CM.

Conclusions: Our findings show that part of the mechanism underlying the wound-healing and neovascularization induced by CBSCs post-MI involves secretion of angiogenesis-related cytokines which alter the behavior of cardiac endothelial cells.

Cortical Bone Stem Cell Therapy Preserves Cardiac Structure and Function After Myocardial Infarction

RATIONALE

Cortical bone stem cells (CBSCs) have been shown to reduce ventricular remodeling and improve cardiac function in a murine myocardial infarction (MI) model. These effects were superior to other stem cell types that have been used in recent early-stage clinical trials. However, CBSC efficacy has not been tested in a preclinical large animal model using approaches that could be applied to patients.

OBJECTIVE

To determine whether post-MI transendocardial injection of allogeneic CBSCs reduces pathological structural and functional remodeling and prevents the development of heart failure in a swine MI model.

METHODS AND RESULTS

Female Göttingen swine underwent left anterior descending coronary artery occlusion, followed by reperfusion (ischemia-reperfusion MI). Animals received, in a randomized, blinded manner, 1:1 ratio, CBSCs (n=9; 2×10⁷ cells total) or placebo (vehicle; n=9) through NOGA-guided transendocardial injections. 5-ethynyl-2'deoxyuridine (EdU)-a thymidine analog-containing minipumps were inserted at the time of MI induction. At 72 hours (n=8), initial injury and cell retention were assessed. At 3 months post-MI, cardiac structure and function were evaluated by serial echocardiography and terminal invasive hemodynamics. CBSCs were present in the MI border zone and proliferating at 72 hours post-MI but had no effect on initial cardiac injury or structure. At 3 months, CBSC-treated hearts had significantly reduced scar size, smaller myocytes, and increased myocyte nuclear density. Noninvasive echocardiographic measurements showed that left ventricular volumes and ejection fraction were significantly more preserved in CBSC-treated hearts, and invasive hemodynamic measurements documented improved cardiac structure and functional reserve. The number of EdU⁺ cardiac myocytes was increased in CBSC- versus vehicle- treated animals.

CONCLUSIONS

CBSC administration into the MI border zone reduces pathological cardiac structural and functional remodeling and improves left ventricular functional reserve. These effects reduce those processes that can lead to heart failure with reduced ejection fraction.

Glutamate carboxypeptidase II (GCPII) inhibitor 2-PMPA reduces rewarding effects of the synthetic cathinone MDPV in rats: a role for N-acetylaspartylglutamate (NAAG)

RATIONALE

Metabotropic glutamate 2 and 3 (mGluR2/3) receptors are implicated in drug addiction as they limit excessive glutamate release during relapse. N-acetylaspartylglutamate (NAAG) is an endogenous mGluR2/3 agonist that is inactivated by the glutamate carboxypeptidase II (GCPII) enzyme. GCPII inhibitors, and NAAG itself, attenuate cocaine-seeking behaviors. However, their effects on the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV) have not been examined.

OBJECTIVES

We determined whether withdrawal following repeated MDPV administration alters GCPII expression in corticolimbic regions. We also examined whether a GCPII inhibitor (2-(phosphonomethyl)-pentanedioic acid (2-PMPA)), and NAAG, reduce the rewarding and locomotor-stimulant effects of MDPV in rats.

METHODS

GCPII was assessed following repeated MDPV exposure (7 days). The effects of 2-PMPA and NAAG on acute MDPV-induced hyperactivity were determined using a locomotor test. We also examined the inhibitory effects of 2-PMPA and NAAG on MDPV-induced place preference, and whether the mGluR2/3 antagonist LY341495 could prevent these effects.

RESULTS

MDPV withdrawal reduced GCPII expression in the prefrontal cortex. Systemic injection of 2-PMPA (100 mg/kg) did not affect the hyperactivity produced by MDPV (0.5-3 mg/kg). However, nasal administration of NAAG did reduce MDPV-induced ambulation, but only at the highest dose (500 μg/10 μl). We also showed that 2-PMPA (10-30 mg/kg) and NAAG (10-500 μg/10 μl) dose-dependently attenuated MDPV place preference, and that the effect of NAAG was blocked by LY341495 (3 mg/kg).

CONCLUSIONS

These findings demonstrate that MDPV withdrawal produces dysregulation in the endogenous NAAG-GCPII signaling pathway in corticolimbic circuitry. Systemic administration of the GCPII inhibitor 2-PMPA, or NAAG, attenuates MDPV reward.