Polarizing Macrophage Functional Phenotype to Foster Cardiac Regeneration

Abstract

There is an increasing interest in understanding the connection between the immune and cardiovascular systems, which are highly integrated and communicate through finely regulated cross-talking mechanisms. Recent evidence has demonstrated that the immune system does indeed have a key role in the response to cardiac injury and in cardiac regeneration. Among the immune cells, macrophages appear to have a prominent role in this context, with different subtypes described so far that each have a specific influence on cardiac remodeling and repair. Similarly, there are significant differences in how the innate and adaptive immune systems affect the response to cardiac damage. Understanding all these mechanisms may have relevant clinical implications. Several studies have already demonstrated that stem cell-based therapies support myocardial repair. However, the exact role that cardiac macrophages and their modulation may have in this setting is still unclear. The current need to decipher the dual role of immunity in boosting both heart injury and repair is due, at least for a significant part, to unresolved questions related to the complexity of cardiac macrophage phenotypes. The aim of this review is to provide an overview on the role of the immune system, and of macrophages in particular, in the response to cardiac injury and to outline, through the modulation of the immune response, potential novel therapeutic strategies for cardiac regeneration.

Keywords: cardiac regeneration; inflammation; innate immunity; macrophages.

Figure 1

Schematic representation of the main cardiac cellular component of the adult heart. Among the immune cells, macrophages can be distinguished in CCR2⁺ and CCR2^– cardiac macrophages.

Figure 2

From inflammation to resolution signaling after cardiac damage.

Figure 3

Immune response in the neonatal and adult heart after myocardial infarction.