Macrophages mediate cardioprotective cellular postconditioning in acute myocardial infarction
Geoffrey de Couto, Weixin Liu, Eleni Tseliou, Baiming Sun, Nupur Makkar, Hideaki Kanazawa, Moshe Arditi, Eduardo Marbán
Geoffrey de Couto, Weixin Liu, Eleni Tseliou, Baiming Sun, Nupur Makkar, Hideaki Kanazawa, Moshe Arditi, Eduardo Marbán
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Research Article Cardiology

Macrophages mediate cardioprotective cellular postconditioning in acute myocardial infarction

Abstract

Ischemic injury in the heart induces an inflammatory cascade that both repairs damage and exacerbates scar tissue formation. Cardiosphere-derived cells (CDCs) are a stem-like population that is derived ex vivo from cardiac biopsies; they confer both cardioprotection and regeneration in acute myocardial infarction (MI). While the regenerative effects of CDCs in chronic settings have been studied extensively, little is known about how CDCs confer the cardioprotective process known as cellular postconditioning. Here, we used an in vivo rat model of ischemia/reperfusion (IR) injury–induced MI and in vitro coculture assays to investigate how CDCs protect stressed cardiomyocytes. Compared with control animals, animals that received CDCs 20 minutes after IR had reduced infarct size when measured at 48 hours. CDCs modified the myocardial leukocyte population after ischemic injury. Specifically, introduction of CDCs reduced the number of CD68+ macrophages, and these CDCs secreted factors that polarized macrophages toward a distinctive cardioprotective phenotype that was not M1 or M2. Systemic depletion of macrophages with clodronate abolished CDC-mediated cardioprotection. Using both in vitro coculture assays and a rat model of adoptive transfer after IR, we determined that CDC-conditioned macrophages attenuated cardiomyocyte apoptosis and reduced infarct size, thereby recapitulating the beneficial effects of CDC therapy. Together, our data indicate that CDCs limit acute injury by polarizing an effector macrophage population within the heart.

Authors

Geoffrey de Couto, Weixin Liu, Eleni Tseliou, Baiming Sun, Nupur Makkar, Hideaki Kanazawa, Moshe Arditi, Eduardo Marbán

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Figure 1

CDCs confer cardioprotection to the ischemic myocardium within 20 minutes of reperfusion.

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CDCs confer cardioprotection to the ischemic myocardium within 20 minute...
(A) Schematic of infusion protocol. Rats underwent 45 minutes of ischemia, followed by either 20 minutes or 120 minutes (delayed injection) of reperfusion prior to infusion of CDCs (5 × 105 cells per 100 μl) or PBS control (100 μl) into the LV cavity during aortic cross-clamp. Animals were assessed 48 hours later. (B) Ejection fraction, as measured by echocardiography, was significantly preserved in CDC-treated animals at 48 hours with a 20-minute, but not a 120-minute, delay of infusion (n = 4–5 rats per group). FAC, fractional area of change. (C) Representative TTC-stained hearts from animals at 48 hours following IR injury. (D) Quantitative measurements of TTC-stained hearts, depicted as percentage of infarct mass, infarct mass, LV mass, and LV viable mass (n = 5–6 rats per group). (E) Representative images of gentian violet– and TTC-stained hearts isolated from rats 48 hours following treatment with PBS or CDCs (5 × 105) and (F) quantitative analysis of the AAR (black line), infarct area (gray line), and LV area of TTC-stained hearts (n = 6–7 rats per group). (G) Linear regression of percentage of infarct mass vs. AAR shows no significant interaction when analyzed for homogeneity of regressions (F = 0.23, P = 0.64) but a difference between adjusted means of infarct mass (F = 84.5, P < 0.001) by analysis of covariance. Graphs depict mean ± SEM. Statistical significance was determined using 1-way ANOVA followed by Bonferroni’s multiple comparisons test. *P < 0.05.