Rebecca D. Levit

Cellular Encapsulation Enhances Cardiac Repair

Background Stem cells for cardiac repair have shown promise in preclinical trials, but lower than expected retention, viability, and efficacy. Encapsulation is one potential strategy to increase viable cell retention while facilitating paracrine effects. Methods and Results Human mesenchymal stem cells (hMSC) were encapsulated in alginate and attached to the heart with a hydrogel patch in a rat myocardial infarction (MI) model. Cells were tracked using bioluminescence (BLI) and cardiac function measured by transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging (CMR). Microvasculature was quantified using von Willebrand factor staining and scar measured by Massons Trichrome. Post‐MI ejection fraction by CMR was greatly improved in encapsulated hMSC‐treated animals (MI: 34±3%, MI+Gel: 35±3%, MI+Gel+hMSC: 39±2%, MI+Gel+encapsulated hMSC: 56±1%; n=4 per group; P<0.01). Data represent mean±SEM. By TTE, encapsulated hMSC‐treated animals had improved fractional shortening. Longitudinal BLI showed greatest hMSC retention when the cells were encapsulated (P<0.05). Scar size at 28 days was significantly reduced in encapsulated hMSC‐treated animals (MI: 12±1%, n=8; MI+Gel: 14±2%, n=7; MI+Gel+hMSC: 14±1%, n=7; MI+Gel+encapsulated hMSC: 7±1%, n=6; P<0.05). There was a large increase in microvascular density in the peri‐infarct area (MI: 121±10, n=7; MI+Gel: 153±26, n=5; MI+Gel+hMSC: 198±18, n=7; MI+Gel+encapsulated hMSC: 828±56 vessels/mm2, n=6; P<0.01). Conclusions Alginate encapsulation improved retention of hMSCs and facilitated paracrine effects such as increased peri‐infarct microvasculature and decreased scar. Encapsulation of MSCs improved cardiac function post‐MI and represents a new, translatable strategy for optimization of regenerative therapies for cardiovascular diseases.

Alginate microencapsulation of human mesenchymal stem cells as a strategy to enhance paracrine-mediated vascular recovery after hindlimb ischaemia

Stem cell‐based therapies hold great promise as a clinically viable approach for vascular regeneration. Preclinical studies have been very encouraging and early clinical trials have suggested favourable outcomes. However, significant challenges remain in terms of optimizing cell retention and maintenance of the paracrine effects of implanted cells. To address these issues, we have proposed the use of a cellular encapsulation approach to enhance vascular regeneration. We contained human mesenchymal stem cells (hMSCs) in biocompatible alginate microcapsules for therapeutic treatment in the setting of murine hindlimb ischaemia. This approach supported the paracrine pro‐angiogenic activity of hMSCs, prevented incorporation of hMSCs into the host tissue and markedly enhanced their therapeutic effect. While injection of non‐encapsulated hMSCs resulted in a 22 ± 10% increase in vascular density and no increase in perfusion, treatment with encapsulated hMSCs resulted in a 70 ± 8% increase in vascular density and 21 ± 7% increase in perfusion. The described cellular encapsulation strategy may help to better define the mechanisms responsible for the beneficial effects of cell‐based therapies and provide a therapeutic strategy for inducing vascular growth in the adult. As hMSCs are relatively easy to isolate from patients, and alginate is biocompatible and already used in clinical applications, therapeutic cell encapsulation for vascular repair represents a highly translatable platform for cell‐based therapy in humans. Copyright

A Minimally Invasive, Translational Method to Deliver Hydrogels to the Heart Through the Pericardial Space

Visual Abstract

Adenosine Production by Biomaterial‐Supported Mesenchymal Stromal Cells Reduces the Innate Inflammatory Response in Myocardial Ischemia/Reperfusion Injury

Background During myocardial ischemia/reperfusion (MI/R) injury, there is extensive release of immunogenic metabolites that activate cells of the innate immune system. These include ATP and AMP, which upregulate chemotaxis, migration, and effector function of early infiltrating inflammatory cells. These cells subsequently drive further tissue devitalization. Mesenchymal stromal cells (MSCs) are a potential treatment modality for MI/R because of their powerful anti‐inflammatory capabilities; however, the manner in which they regulate the acute inflammatory milieu requires further elucidation. CD73, an ecto‐5′‐nucleotidase, may be critical in regulating inflammation by converting pro‐inflammatory AMP to anti‐inflammatory adenosine. We hypothesized that MSC‐mediated conversion of AMP into adenosine reduces inflammation in early MI/R, favoring a micro‐environment that attenuates excessive innate immune cell activation and facilitates earlier cardiac recovery. Methods and Results Adult rats were subjected to 30 minutes of MI/R injury. MSCs were encapsulated within a hydrogel vehicle and implanted onto the myocardium. A subset of MSCs were pretreated with the CD73 inhibitor, α,β‐methylene adenosine diphosphate, before implantation. Using liquid chromatography/mass spectrometry, we found that MSCs increase myocardial adenosine availability following injury via CD73 activity. MSCs also reduce innate immune cell infiltration as measured by flow cytometry, and hydrogen peroxide formation as measured by Amplex Red assay. These effects were dependent on MSC‐mediated CD73 activity. Finally, through echocardiography we found that CD73 activity on MSCs was critical to optimal protection of cardiac function following MI/R injury. Conclusions MSC‐mediated conversion of AMP to adenosine by CD73 exerts a powerful anti‐inflammatory effect critical for cardiac recovery following MI/R injury.

A Clinical Commentary on the Article “N-acetylglucosamine Conjugated to Nanoparticles Enhances Myocyte Uptake and Improves Delivery of a Small Molecule p38 Inhibitor for Post-infarct Healing”

Targeting drugs and nanoparticles to cardiomyocytes has been an elusive challenge. Cardiomyocytes are inherently non-phagocytic and their environment is subjected to contractile forces which tend to expel injected and catheter-delivered drugs. In this issue, a novel-targeting strategy, N-acetyl-glucosamine (GlcNAc) coating, is shown to enhance cardiomyocyte nanoparticle uptake both in vitro and in vivo. Many effective and proven therapies for myocardial infarction are in clinical use thus raising the bar for the translation of new technologies. Nevertheless, GlcNAc targeting represents a promising approach for improved targeting of drug therapies to cardiomyocytes.

Pheochromocytoma Masquerading as “Diabetic Ketoacidosis”

Diabetic ketoacidosis is a routinely encountered diagnosis in medicine. Physicians are trained early on to look for precipitants. Most clinicians assess for medication compliance, infection, ischemia, and the like. We present a case of pheochromocytoma presenting as “diabetic ketoacidosis.” The case serves as an example for broadening the differential diagnosis for patients with similar presentations. Additionally, the case helps inform our understanding of the so-called “stress reactions” that are commonly invoked in clinical rationale.

Engineering Vessels as Good as New

Summary Blood vessels convey essential nutrients to end organs, and when diseased, they must be replaced or bypassed. Traditionally plastic and synthetic materials have been used but are susceptible to thrombosis, stenosis, and poor patency rates. A recent report in Science Translational Medicine describes a decellularized matrix grown in vitro from commercially sourced fibroblasts that can be used as a vascular graft. Fibroblasts are grown for several weeks on a fibrin scaffold, laying down a collagen layer. After decellularization and transplantation as an arteriovenous fistula, this group showed that grafts remained patent for several weeks. The lack of cellular material in this graft at the time of transplantation reduced the risk of immune rejection. The matrix laid down by the fibroblasts can serve as a scaffold for recipient cells to colonize after implantation, but also provides structural support for arterial blood flow. Other tissue-engineered grafts of decellularized matrices have recently been tested in clinical trial. For these strategies, the cell type, scaffold material, and culture conditions are key components that dictate not only the type and quality of the end product, but also allow standardization and quality control necessary for widespread translation into clinical use. These off-the-shelf decellularized products may be the first in a new generation of therapies for patients with cardiovascular disease.

Minimally Invasive Delivery of Hydrogel-Encapsulated Amiodarone to the Epicardium Reduces Atrial Fibrillation

Background: Atrial fibrillation (AF) is the most common cardiac arrhythmia. Although treatment options for AF exist, many patients cannot be maintained in normal sinus rhythm. Amiodarone is an effective medication for AF but has limited clinical utility because of off-target tissue toxicity. Methods: Here, we use a pig model of AF to test the efficacy of an amiodarone-containing polyethylene glycol–based hydrogel. The gel is placed directly on the atrial epicardium through the pericardial space in a minimally invasive procedure using a specially designed catheter. Results: Implantation of amiodarone-containing gel significantly reduced the duration of sustained AF at 21 and 28 days; inducibility of AF was reduced 14 and 21 days post-delivery. Off-target organ drug levels in the liver, lungs, thyroid, and fat were significantly reduced in animals treated with epicardial amiodarone gel compared with systemic controls in small-animal distribution studies. Conclusions: The pericardium is an underutilized therapeutic site and may be a new treatment strategy for AF and other cardiovascular diseases.

Cardiovascular Regeneration: Biology and Therapy

Department of Pediatrics, Emory University School of Medicine, 2015 Uppergate Dr, Atlanta, GA 30322, USA Department of Biomedical Sciences, City University of Hong Kong, 1B-205, 2/F, Block 1, To Yuen Building, Kowloon Tong 999077, Hong Kong Division of Cardiology, Department of Medicine, Emory University School of Medicine, 101 Woodruff Circle, Atlanta, GA 30322, USA University of Ottawa Heart Institute and Department of Cellular and Molecular Medicine, University of Ottawa, 40 Ruskin St., Ottawa, ON, Canada K1Y 4W7 College of Medicine, Cardiovascular Center, Seoul St. Mary’s Hospital, The Catholic University of Korea, 222 Banpodaero, Seocho-ku, Seoul 137-040, Republic of Korea

High Risk, High Stakes: Optimizing Cardiovascular Risk Assessment in Women

Women worldwide are at risk for cardiovascular disease (CVD), with CVD mortality accounting for > 50% of deaths in women in the United States. CVD risk stratification in women was traditionally similar to that in men, leading to under-detection of disease in women. Recently women-specific guidelines have raised awareness of female-specific risk factors. Pre-eclampsia has a striking correlation with increased CVD events in women decades after pregnancy. New serum markers of CVD such as C-reactive protein show promise of early detection but have uncertain clinical value since they may not help re-stratify women at intermediate risk. Imaging tests such as coronary artery calcium scoring and carotid intimal medial thickness have been investigated in women. They too may fail to recognize women at long-term increased risk and how to apply these tests clinically is uncertain. This article critically reviews new developments in risk stratification of CVD in women.