Acute myocardial rescue with endogenous endothelial progenitor cell therapy

Abstract

Purpose: Post-myocardial infarction heart failure is a major health concern with limited therapy. Molecular revascularisation utilising granulocyte-macrophage colony stimulating factor (GMCSF) mediated endothelial progenitor cell (EPC) upregulation and stromal cell derived factor-1α (SDF) mediated myocardial EPC chemokinesis, may prevent myocardial loss and adverse remodelling. Vasculogenesis, viability, and haemodynamic improvements following therapy were investigated.

Procedures: Lewis rats (n=91) underwent LAD ligation and received either intramyocardial SDF and subcutaneous GMCSF or saline injections at the time of infarction. Molecular and haemodynamic assessments were performed at pre-determined time points following ligation.

Findings: SDF/GMCSF therapy upregulated EPC density as shown by flow cytometry (0.12±0.02% vs. 0.06±0.01% circulating lymphocytes, p=0.005), 48hours following infarction. A marked increase in perfusion was evident eight weeks after therapy, utilising confocal angiography (5.02±1.7×10(-2)μm(3)blood/μm(3)myocardial tissue vs. 2.03±0.710(-2)μm(3)blood/μm(3)myocardial tissue, p=0.00004). Planimetric analysis demonstrated preservation of wall thickness (0.98±0.09mm vs. 0.67±0.06mm, p=0.003) and ventricular diameter (7.81±0.99mm vs. 9.41±1.1mm, p=0.03). Improved haemodynamic function was evidenced by echocardiography and PV analysis (ejection fraction: 56.4±18.1% vs. 25.3±15.6%, p=0.001; pre-load adjusted maximal power: 6.6±2.6mW/μl(2) vs. 2.7±1.4mW/μl(2), p=0.01).

Conclusion: Neovasculogenic therapy with GMCSF-mediated EPC upregulation and SDF-mediated EPC chemokinesis maybe an effective therapy for infarct modulation and preservation of myocardial function following acute myocardial infarction.

Figure 1

Representative flow cytometric plots of circulating blood 48 hours following acute LAD ligation. (A + B) Pseudo-color plots delineating the desired viable (7AAD⁻) lymphocyte population selected utilising side and forward scatter. (C + D) Lineage negative, CD45^dim lymphocytes. (E) EPC density in a representative saline control animal, as determined by co-labeling for VEGFR2 and cKit (CD45^dim). (F) EPC density in a representative SDF/GMCSF control animal, as determined by co-labeling for VEGFR2 and cKit (CD45^dim).

Figure 2

Three dimensional microvascular lectin angiogram demonstrating enhanced myocardial perfusion following neovasculogenic therapy. Representative microvascular angiograms from remote, non-ischaemic and peri-infarct borderzone myocardium of saline control and SDF/GMCSF treated groups. (25× magnification)

Figure 3

1) Representative haematoxylin and eosin stained images of myofilament density within the remote (A=Saline Control, B=SDF/GMCSF) and borderzone myocardium (C=Saline Control, D=SDF/GMCSF). 2) Myofilament density within the remote and borderzone myocardium. (40× magnification).

Figure 4

Representative cross-sectional Masson’s Trichrome stained sections of (A) saline control and (B) SDF/GMCSF treated myocardial specimens. Small arrows indicate regions of myocardial peri-infarct borderzone measurements. Large arrows indicate ventricular diameter. Collagen of scar is stained blue and viable myocardium is stained red.

Figure 5

Representative end-diastolic, parasternal, short axis echocardiographic views at the level of the papillary muscle of the left ventricle, 8 weeks following LAD ligation, demonstrating significant dilatation and lateral wall thinning of the control hearts when compared to the SDF/GMCSF group (A= Saline Control, B= SDF/GMCSF). M-mode echocardiographic images delineating left ventricular dilatation and lateral wall thinning (C= Saline Control, D=SDF/GMCSF).

Figure 6

Pressure-volume loops from (A) saline control and (B) SDF/GMCSF treated hearts 8 weeks following LAD ligation. Pressure-volume loops were obtained with an intra-venticular left ventricular pressure-volume catheter during occlusion of the inferior vena cava. Slope of contractility is represented in red.