Online

Liebman, Benjamin

Pharmacology

2021

M.S.

Coronary artery disease leading to myocardial infarction (a.k.a. MI, heart attack) is one of the leading causes of death globally. Each year an estimated 605,000 Americans suffer a heart attack, which equates to one MI every 40 seconds. As such, MI represents one of the largest health burdens to society. The current standard of care is revascularization therapy achieved by fibrinolytics and Percutaneous Coronary Intervention (PCI); both of which re-open occluded proximal arteries to restore blood flow to the affected areas. Despite revascularization therapy, 30-50% of patients exhibit a form of reperfusion injury termed "no/low-reflow" in which the blood supply to distal vessels remains compromised. Currently, there is no FDA-approved therapy to treat reperfusion injury or no/low reflow after MI. The cell-based therapy field has sought to treat reperfusion injury with transplantation of stem/progenitor cells that promote angiogenesis and replace lost microvessels, or contribute directly to the vasculature or cardiac myocyte pool through direct differentiation. Notably, however, poor cell engraftment and survival and a lack of sustained angiogenesis has limited the utility of cell-based approaches. A different strategy to treat reperfusion injury involves administration of paracrine factors, as opposed to cells with paracrine activity. Our lab has previously reported vasoprotective complexes formed between Hepatocyte Growth Factor (HGF) and mixed, non-specific polyclonal Immunoglobulin G (IgG). Treatment with HGF/IgG complexes was demonstrated to be vaso- and cardioprotective in a rodent model of MI with reperfusion. In work presented here, we hypothesized that other heparin-binding growth factors interact with IgG in a manner similar to HGF and that the resulting complexes would effectively protect the myocardium after MI. To identify additional factors capable of binding the glycosylated IgG Fc domain, we utilized a native agarose electrophoresis system at physiological pH (7.4) and pull-down assays using Protein-A conjugated to agarose beads. We determined that basic Fibroblast Growth Factor (a.k.a bFGF or FGF2) formed complexes with IgG (FGF2:IgG). Furthermore, addition of FGF2 was found to seed and participate in complex formation with HGF and IgG (FGF2:HGF:IgG). Intriguingly, molecular modeling studies suggest a single Fc domain is capable of accommodating both heparin-binding growth factors simultaneously (on opposing sides). To assess the cardioprotective capacity of the biologic complexes ex vivo, primary human cardiac microvascular endothelial cells were exposed to simulated ischemia (nutrient deprivation and 1% oxygen) for 48-72 hours. FGF2:HGF:IgG complexes significantly promoted cell survival. Furthermore, in pre-clinical studies using a porcine model of MI with reperfusion, intracoronary delivery of FGF2:HGF:IgG from the PCI guide catheter after stenting rescued myocardial tissue and electrical conduction within the infarcted area 24 hours after treatment. Our data indicate FGF2:HGF:IgG complexes preserve tissue at risk after ischemic insult and may reduce reperfusion injury and no/low-reflow after MI.