Specialized functions of resident macrophages in brain and heart

Abstract

The functions of macrophages in healthy tissues extend beyond their well-established roles as immune sentinels and effectors. Among tissues, cells of the brain and heart possess unique excitatory properties that likely demand special support. Accordingly, existing evidence demonstrates that microglia in the brain has an active role in synaptic organization, control of neuronal excitability, phagocytic removal of debris, and trophic support during brain development. In the heart, recent studies suggest that cardiac macrophages are involved in the regulation of heart homeostasis by phagocytosis, production of trophic, and immune-related factors, and by forming direct contacts with cardiomyocytes to regulate electrical conduction. In this review, we discuss mechanisms associated with the high degree of specialization of resident macrophages in both tissues, their origin and heterogeneity, and their contributions in regulating homeostasis under steady-state and pathological conditions.

Distinct fate, dynamics and niches of renal macrophages of bone marrow or embryonic origins

“…It is widely accepted that the role of TMs differs from those of monocytes and infiltrating/surveilling macrophages. TMs, such as microglia and gut macrophages differ significantly between two tissues and even within different regions of the same tissue 64,[73][74][75] . Various combinations of markers, including MHCII/CX3CR1/CD11b for macrophages in heart and F4/80 high/low for microglia, have been used to compare functional differences 64 , but these markers may indicate activation status, rather than the origin, of the cells.…”

CCL2/CCR2 signaling in cancer pathogenesis

“…They are activated by IFNγ or lipopolysaccharide, and characterized by high expression of IL-12 (Interleukin-12) and low expression of IL-10 (Interleukin-10). Under normal conditions, M1 macrophages are responsible for protecting the host against infection and injury and facilitating tissue remodeling [68], also suspected to be important in the formation of important organs like the heart and brain [77]. In contrast, M2 macrophages are activated by IL-4, IL-13, IL-10, and glucocorticoid hormones, produce high levels of IL-10 and low levels of IL-12, and promote tumor progression [26].…”

The Roles of Noncardiomyocytes in Cardiac Remodeling

“…Macrophages, which are equipped with various signaling receptors, are a crucial cell type that integrates signaling pathways and actively responds to disease-related stress. In healthy hearts, a group of macrophages of both YS and monocyte origin were present [66,73]. In cardiac tissue undergoing infarction, the cellular response differed in different regions.…”