Tissue-engineered, hydrogel-based endothelial progenitor cell therapy robustly revascularizes ischemic myocardium and preserves ventricular function

Abstract

Objective Cell based angiogenic therapy for ischemic heart failure has had limited clinical impact, likely related to very low cell retention (<1%) and dispersion. We developed a novel, tissue engineered, hydrogel based cell delivery strategy to overcome these limitations and provide prolonged regional retention of myocardial endothelial progenitor cells (EPC) at high cell dosage. Methods EPCs were isolated from Wistar Rats and encapsulated in fibrin gels. In vitro viability was quantified using a fluorescent live-dead stain of transgenic eGFP+ EPCs. EPC-laden constructs were implanted onto ischemic rat myocardium in a model of acute myocardial infarction (LAD ligation) for 4 weeks. Intramyocardial cell injection (IC, 2×106 EPCs), empty fibrin, and isolated LAD ligation groups served as controls. Hemodynamics were quantified using echocardiography, Doppler flow analysis, and intraventricular pressure-volume analysis. Vasculogenesis and ventricular geometry were quantified. EPC migration was analyzed by utilizing EPCs from transgenic eGFP+ rodents. Results EPCs demonstrated an overall 88.7% viability for all matrix and cell conditions investigated after 48 hours. Histologic assessment of 1-wk implants demonstrated significant migration of transgenic eGFP+ EPCs from the fibrin matrix to the infarcted myocardium as compared to IC (28±12.3 vs. 2.4±2.1cells/hpf, p=0.0001). We also observed a marked increase in vasculogenesis at the implant site. Significant improvements in ventricular hemodynamics and geometry were present following EPC-hydrogel therapy as compared to control. Conclusion We present a tissue engineered hydrogel-based EPC mediated therapy to enhance cell delivery, cell retention, vasculogenesis, and preservation of myocardial structure and function.

Towards the standardization of stem cell therapy studies for ischemic heart diseases: Bridging the gap between animal models and the clinical setting

“…Sustained release of stem cells using scaffolds, matrices or microcarriers The realization of the poor survival and retention of stem cells in the hostile myocardium has stimulated researchers to design strategies to protect them from the adversities found in an infarcted myocardium or in an already failing heart. Several hypotheses have been tested to shield cells from the hypoxic, serum-deprived, inflammatory, immuneactivated and pro-apoptotic infarcted/ischemic myocardium, namely the use of scaffolds, biomatrices, biomaterials, hydrogels (broadly accepted as synonyms) [17,18,20 [36]. Numerous biomaterials have been used to overcome this hurdle, such as hyaluronan, collagen I, agarose, fibrin, fibrinogen and alginate/chitosan combinations.…”

“…Also, they promote migration of endothelial cells and smooth muscle cells and, simultaneously, confer CMs protection from apoptosis. In addition, these materials have low immunogenicity and have anti-inflammatory and pro-angiogenic properties [17,18,20,37,50,53,67,107,108,112,115]. This explains why delivery of stem cells in scaffolds has higher benefits to those delivered in aqueous or in culture media, with regard to cell retention and proliferation as well as structural and functional myocardial recovery.…”

“…Similarly, EPC delivered in a fibrin patch was found to be better than simple EPC injection in ameliorating LVEF, cardiac output, maximal developed pressure and contractility in a rat model of AMI. The use of EPC-fibrin patches brings the additional advantage of being already FDA-approved, which prompts their application into clinical trials [17]. However, fibrin is more viscous than fibrinogen and may, in fact, challenge cell injection and cell nutrition.…”

“…[15,30,34,76,102]), intravenous (IVI, [44,54]) and intramuscular injections [46] and epicardial delivery (e.g. [17,53,[64][65][66]) are routes of choice, too. Stem cells can be administered directly by IMI or by epicardial delivery, although one should realize that these are very invasive procedures that can compromise the condition of the patients even further.…”

Looking Beyond Reperfusion

“…The transposition of a fat flap over the ischemic myocardium has recently been proposed, with promising results in the swine preclinical model of MI [82]. Tissue-engineered, hydrogel-based Mesenchymal stem cells (MSCs) [83] and endothelial progenitor cell [84] therapy have been shown some promising results in re-vascularizing the ischemic myocardium and preserving ventricular function through paracrine effects [85]. Table 3 presents recent cell based clinical trials for cell based therapies of regeneration of myocardium.…”