Direct injection of autologous mesenchymal stromal cells improves myocardial function

Abstract

Cell-based therapies have been employed with conflicting results. Whether direct injection of ex-vivo expanded autologous marrow stromal cells (MSCs) would improve the function of ischemic myocardium and enhance angiogenesis is not well defined. In a porcine model of chronic ischemia, MSCs were isolated and cultured for 4 weeks. Sixteen animals were random divided into two groups to receive either direct intramyocardial injection of autologous MSCs, or equal volumes and injections sites of saline. Cine MRI and epicardial echocardiography were performed just prior to the injections and again 6 weeks later at the time of sacrifice at which point tissue was also analyzed. Myocardial function as assessed by regional wall thickening (as measured by dobutamine stress echocardiograms) demonstrated a 40.9% improvement after cell treatment of the ischemic zone (p=0.016) whereas the saline treated animals only had a 3.7% change (p=0.82) compared to baseline. The left ventricular ejection fractions of MSC group showed 19.5% improvement from baseline 35.9+/-3.8% to 42.9+/-5.8% (p=0.049). Increased vascularity was found in the MSC group compared to controls (0.80+/-0.30 vs 0.50+/-0.19 capillary/myocyte ratio, p=0.018). Direct injection of autologous MSCs promotes angiogenesis and enhances the functional improvements following chronic myocardial ischemia. This suggests that the angiogenesis engendered by cell treatment may be physiologically meaningful by improving the contractility of ischemic myocardium.

Figure 1

Figure 1A. By echocardiography, the change in wall thickening in saline group showed no significant difference (p = 0.82), while the cell treated groups demonstrating significant improvement in regional wall motion as assessed by stress echocardiography from baseline to 6 weeks after treatment (p = 0.018). Figure 1B. By cine MRI, the average left ventricle ejection fraction in cells group was significantly higher after 6 wks of cell treatment compared with baseline (p<0.049) while the control group showed no statistical difference between baseline and follow up.

Figure 1

Figure 1A. By echocardiography, the change in wall thickening in saline group showed no significant difference (p = 0.82), while the cell treated groups demonstrating significant improvement in regional wall motion as assessed by stress echocardiography from baseline to 6 weeks after treatment (p = 0.018). Figure 1B. By cine MRI, the average left ventricle ejection fraction in cells group was significantly higher after 6 wks of cell treatment compared with baseline (p<0.049) while the control group showed no statistical difference between baseline and follow up.

Figure 2

Bar graph shows the average capillary density of saline and cell injected groups expressed by ratio to myocytes at 6 weeks (top); immunofluorecent staining with vWF (red), collagen IV (green) and dapi (blue) represent the difference following treatment with saline or cell injection (bottom left and right, ×380).

Figure 3

Left panel: Animal sacrificed at 1 wk after MSCs injection. A. Arrow shows injected cells (×100); B. high magnification (×400); C and D shows desmin or smooth muscle actin staining alone with vW factor (×380). Right panel: Animal sacrificed at 2 wks after MSCs injection: a) Arrow shows injected cells ×100); b) high magnification (×400); c) Arrow shows positive CD90 staining of injected cells (×400); d) positive control for CD90 staining of MSCs pellets in frozen section (×600); e) and f) double staining of desmin or smooth muscle actin along with vW factor (×380). Figure labels: A=artery, Myo=myocardial area, Epi=epicardial area.

Figure 4

a) At 6 wks, injected cells form groups of small vessels (H&E, x200); b) Smooth muscle actin (green) and vWF staining (red) (×200); c) Higher magnification of b (×400); d) Injected cells showing no sign of cardiomyocytes morphologically and negatively stained for desmin, a marker for myocytes (×400).