EPC-derived EVs delivered into ischaemic myocardium via an injectable hydrogel enhanced peri-infarct angiogenesis and myocardial haemodynamics in a rat model of MI. The STG greatly increased therapeutic efficiency and efficacy of EV-mediated myocardial preservation.
OBJECTIVES
The clinical translation of cell based therapies for ischemic heart disease has been limited due to low cell retention (<1%) within and poor targeting to ischemic myocardium. To address these issues, we developed an injectable shear-thinning hyaluronic acid hydrogel (STG) and endothelial progenitor cell construct (STG-EPC). The STG assembles due to interactions of adamantine and β-cyclodextrin modified hyaluronic acid. It is shear-thinning to permit delivery via a syringe, and self-heals upon injection within the ischemic myocardium. This directed therapy to the ischemic myocardial borderzone enables direct cell delivery to address adverse remodeling after myocardial infarction. We hypothesize that this system will enhance vasculogenesis to improve myocardial stabilization in the context of a clinically translatable therapy.
METHODS
EPCs (DiLDL+ VEGFR2+ CD34+) were harvested from adult male Wistar Rats, cultured, and then suspended in the STG. In vitro viability was quantified using a live-dead stain of EPCs. STG-EPC constructs were injected at the borderzone of ischemic rat myocardium after acute myocardial infarction (left anterior descending coronary artery ligation). The migration of the eGFP+ EPCs from the construct to ischemic myocardium was analyzed using fluorescent microscopy. Vasculogenesis, myocardial remodeling, and hemodynamic function were analyzed in 4 groups: control (PBS injection), intramyocardial injection of EPCs alone (EPC), injection of the STG alone (STG), and treatment with the gel-EPC construct (STG-EPC). Hemodynamics and ventricular geometry were quantified using echocardiography and Doppler flow analysis.
RESULTS
EPCs demonstrated viability within the STG. A marked increase in EPC engraftment was observed one-week post-injection within the treated myocardium with gel delivery when compared to EPC injection alone (17.2 ± 0.8 cells/HPF vs. 3.5 cells ± 1.3 cells/HPF, p = 0.0002). A statistically significant increase in vasculogenesis was noted with the STG-EPC construct (15.3 ± 5.8 vessels/HPF) when compared to control (p < 0.0001), EPC (p < 0.0001), and STG (p < 0.0001) groups. Statistically significant improvements in ventricular function, scar fraction, and geometry were also noted after STG-EPC treatment compared to the control.
CONCLUSIONS
A novel injectable shear-thinning hyaluronic acid hydrogel seeded with EPCs enhanced cell retention and vasculogenesis after delivery to ischemic myocardium. This therapy limited adverse myocardial remodeling while preserving contractility.
Minimally invasive mitral valve surgery can be performed with overall equivalent cost and shorter hospital stay relative to traditional sternotomy. There is greater operative cost associated with minimally invasive mitral valve surgery that is offset by shorter intensive care unit and hospital stays.
Background
Neuregulin (NRG) is a member of the epidermal growth factor family possessing a critical role in cardiomyocyte development and proliferation. Systemic administration of NRG demonstrated efficacy in cardiomyopathy animal models, leading to clinical trials employing daily NRG infusions. This approach is hindered by requiring daily infusions and off-target exposure. Therefore, this study aimed to encapsulate NRG in a hydrogel (HG) to be directly delivered to the myocardium, accomplishing sustained localized NRG delivery.
Methods and Results
NRG was encapsulated in HG and release over 14 days confirmed by ELISA in vitro. Sprague-Dawly rats were utilized for cardiomyocyte isolation. Cells were stimulated by PBS, NRG, HG, or NRG-HG and evaluated for proliferation. Cardiomyocytes demonstrated EdU and phosphorylated histone-H3 (PH3) positivity in the NRG-HG group only. For in vivo studies, 2 month old mice (n=60) underwent LAD ligation and were randomized to the 4 treatment groups mentioned. Only NRG-HG treated mice demonstrated PH3 and Ki67 positivity along with decreased caspase-3 activity compared to all controls. NRG was detected in myocardium 6 days following injection without evidence of off-target exposure in NRG-HG animals. At 2 weeks, the NRG-HG group exhibited enhanced LVEF, decreased LV area, and augmented borderzone thickness.
Conclusions
Targeted and sustained delivery of NRG directly to the myocardial borderzone augments cardiomyocyte mitotic activity, decreases apoptosis, and greatly enhances LV function in a model of ICM. This novel approach to NRG administration avoids off-target exposure and represents a clinically translatable strategy in myocardial regenerative therapeutics.
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