Autologous mesenchymal stem cells produce reverse remodelling in chronic ischaemic cardiomyopathy

Abstract

Aims: The ability of mesenchymal stem cells (MSCs) to heal the chronically injured heart remains controversial. Here we tested the hypothesis that autologous MSCs can be safely injected into a chronic myocardial infarct scar, reduce its size, and improve ventricular function.

Methods and results: Female adult Göttingen swine (n = 15) underwent left anterior descending coronary artery balloon occlusion to create reproducible ischaemia-reperfusion infarctions. Bone-marrow-derived MSCs were isolated and expanded from each animal. Twelve weeks post-myocardial infarction (MI), animals were randomized to receive surgical injection of either phosphate buffered saline (placebo, n = 6), 20 million (low dose, n = 3), or 200 million (high dose, n = 6) autologous MSCs in the infarct and border zone. Injections were administered to the beating heart via left anterior thoracotomy. Serial cardiac magnetic resonance imaging was performed to evaluate infarct size, myocardial blood flow (MBF), and left ventricular (LV) function. There was no difference in mortality, post-injection arrhythmias, cardiac enzyme release, or systemic inflammatory markers between groups. Whereas MI size remained constant in placebo and exhibited a trend towards reduction in low dose, high-dose MSC therapy reduced infarct size from 18.2 +/- 0.9 to 14.4 +/- 1.0% (P = 0.02) of LV mass. In addition, both low and high-dose treatments increased regional contractility and MBF in both infarct and border zones. Ectopic tissue formation was not observed with MSCs.

Conclusion: Together these data demonstrate that autologous MSCs can be safely delivered in an adult heart failure model, producing substantial structural and functional reverse remodelling. These findings demonstrate the safety and efficacy of autologous MSC therapy and support clinical trials of MSC therapy in patients with chronic ischaemic cardiomyopathy.

Figure 1

Blood and serum markers of inflammation and myocardial tissue damage. There is no significant difference between placebo, low-dose, and high-dose-treated animals immediately post-myocardial infarction and 12 weeks after injection.

Figure 2

TGF-β serum levels after surgery. Within 24 h of stem-cell transplant, there is a dramatic drop (Day 1B) in the circulating levels of TGF-β in the high-dose mesenchymal stem cell group (*P < 0.05 vs. placebo, ^†P < 0.05 Day 1A vs. Day 1B), which recovers by Day 3. The low-dose mesenchymal stem cell animals follow the same pattern, but to a smaller extent. Ninety days after surgery the serum levels of TGF-β are not significantly different. (^§P < 0.001 high-dose mesenchymal stem cell group repeated measures ANOVA).

Figure 3

Isolated dystrophic cardiac calcinosis in a chronic infarct scar. (A and B) An isolated focus of calcification in dense scar tissue from a porcine heart injected with 200 × 10⁶ autologous mesenchymal stem cells surrounded by dense collagen fibres and mainly fibroblasts. (C–F) Example of localized inflammation 12 weeks after injection of 200 × 10⁶ MSCs. (C and D) Inflammatory cells not particularly organized and located near a large vessel in the viable myocardium. The only example of a large focus of inflammation is shown in (E) and (F). Two focal islands of inflammatory cell infiltrates in the centre scar region and at the border region of the infarct. The higher magnification of the dense collection of lymphocytes and macrophages demonstrates interspersed angiogenesis in (F). All samples were stained with haematoxylin and eosin.

Figure 4

Impact of autologous mesenchymal stem cells therapy on chronic infarct scar remodelling in heart failure. (A) Contiguous short-axis delayed enhanced magnetic resonance imaging images show an example of an untreated animal 12 weeks after injection. The thinned infarct scar and the dilated ventricle can be appreciated. (B) Corresponding images from a high-dose-treated animal. The scar region is thicker and viable myocardium can be appreciated surrounding the scar tissue. (C and D) The effect of mesenchymal stem cell treatment on scar percentage of left ventricular and absolute volume of scar tissue (*P < 0.05 vs. placebo, ^†P < 0.05 week 12 vs. week 24).

Figure 5

Plots of peak circumferential shortening (peak Ecc) in the infarct, border, and remote zones. Peak negative Ecc values represent myocardial shortening and increased contractility, whereas increasingly positive values indicate myocardial dysfunction. Ecc improves after cell therapy in both low- and high-dose cell groups in infarct border zones. In contrast, Ecc improves in infarct zones only in the high and not the low-dose MSC group. (*P < 0.05 vs. placebo, ^†P < 0.05 week 12 vs. week 24).

Figure 6

Plot of the average upslope to peak myocardial blood flow, normalized by left-ventricular blood pool intensity, in the resting state and the coronary flow reserve (stressed myocardial blood flow divided by resting myocardial blood flow), in the infarct, border, and remote zones. A higher value is indicative of greater flow. (*P < 0.05 vs. placebo, ^†P < 0.05 week 12 vs. week 24).

Figure 7

Impact of autologous mesenchymal stem cells therapy on global ventricular function in animals with ischaemic cardiomyopathy assessed by magnetic resonance imaging. Ejection fraction is reduced in all groups 12 weeks post-MI and remains depressed in placebo-treated animals. Progressive improvement after 12 weeks is observed in high-dose-treated animals. (*P = 0.02 vs. placebo; ^†P = 0.01 week 12 vs. week 24).