Apoptosis and subsequent removal of dead cells are an essential part of wound healing. Macrophages phagocytize apoptotic cells (efferocytosis) and contribute to the resolution of inflammation. However, their participation in fibrogenesis and the mechanisms of influence on this process remain unclear. In the present study, we focused on the fibrogenic properties of human monocyte-derived macrophages polarized in the M2 direction by interaction with apoptotic cells. We studied their influence on the proliferation ([3H]-thymidine incorporation), differentiation (by the expression of α-SMA, a myofibroblast marker) and collagen-producing activity (ELISA) of dermal fibroblasts compared to classically (LPS) and alternatively (IL-4) activated macrophages. Macrophages polarized by the interaction with apoptotic cells had a unique phenotype and profile of produced factors and differed from the compared macrophage subtypes. Their conditioned media promoted the proliferation of dermal fibroblasts and the expression of α-SMA in them at the level of macrophages stimulated by IL-4, while the stimulating effect on the collagen-producing activity was more pronounced compared to that of the other macrophage subtypes. Moreover, they are characterized by the high level of production of pro-fibrotic factors such as TIMP-1, TGF-β1 and angiogenin. Taken together, M2-like macrophages polarized by efferocytosis demonstrate in vitro pro-fibrotic activity by promoting the functional activity of dermal fibroblasts and producing pro-fibrotic and pro-angiogenic factors.

T-cell immunoglobulin and mucin domain 3 (TIM-3), a well-known immune checkpoint molecule, is increasingly recognized for its regulatory functions beyond T cell exhaustion, particularly in macrophages. Recent advances have revealed the important role of this molecule in various pathological and physiological conditions. The demand for a comprehensive study of TIM-3 is increasing, particularly as a result of ongoing clinical trials targeting TIM-3 in oncology. This review is devoted to the role of TIM-3 in macrophage biology, focusing on associations between TIM-3 expression and macrophage polarization states and functional activity, as well as its involvement in the pathogenesis of different diseases and reproductive immunology. The review examines known effects and molecular mechanisms by which TIM-3 regulates macrophage functional phenotype and the contribution of TIM-3-expressing macrophages to cancer, pregnancy, inflammation, infectious and autoimmune diseases, and fibrosis. Findings highlight the controversial role of TIM-3 in the regulatory function of macrophages and suggest that TIM-3 functions differently depending on the context. The review also touches on gaps and unexplored parts of the topic. A summary of current data allows us to conclude that TIM-3 is an important modulator of macrophage functions and can be considered a potential therapeutic target in various pathological conditions.

Продукция факторов, участвующих в регуляции фиброза, различными типами макрофагов человека

GM-CSF and M-CSF, the hematopoietic colony-stimulating factors, induce various phenotypic changes in macrophage lineage populations and promote cell differentiation, respectively, into M1- and M2-like macrophages. The pro- and anti-inflammatory properties of macrophages generated by these colony-stimulating factors are well described, but the contribution of differentiation and polarization signals to the fibromodulatory activity of macrophages remains unexplored. To clarify the differences in the fibrogenesis regulation mechanisms inherent in differently activated macrophages, we studied the effects of macrophage-conditioned media on proliferation and differentiation of dermal fibroblasts. In this study, the human macrophages generated from peripheral blood monocytes were investigated. They were induced for differentiation by M-CSF or GM-CSF, being further polarized in the M1 direction with lipopolysaccharide and, in the M2 direction, with IL-4 or dexamethasone. Proliferative response of the fibroblasts was determined radiometrically by [3H]-thymidine incorporation. Differentiation into myofibroblasts was determined with flow cytometry technique, as expression of a specific marker α-smooth muscle actin (α-SMA). The level of macrophage TGF-β1 production was assessed using an appropriate ELISA kit. The data obtained indicate that the macrophages differentiated under the influence of “homeostatic” M-CSF are characterized by a moderate stimulating effect upon fibroblast proliferation, and the effects of M2 (IL-4) and M2 (Dex) macrophages exceed that of M1 (LPS), but do not differ significantly from each other. The M-CSF-induced M1 (LPS) and M2 (IL-4) macrophages, but not M2 (Dex), enhance the fibroblast differentiation and show similar level of stimulation. In contrast to M-CSF, the macrophages induced by “pro-inflammatory” GM-CSF exhibit a pronounced stimulatory effect on fibroblast proliferation, and the effects of M2 macrophages exceed those of M1 cells, being most pronounced for M2 (Dex). At the same time, only GM-CSF-induced M2 (IL-4) macrophages enhance fibroblast differentiation. Dexamethasone-polarized macrophages do not significantly affect fibroblast differentiation regardless of the CSF used (M-CSF or GM-CSF). The content of TGF-β1 in the supernatants of differently activated macrophages does not correlate with the level of stimulating effect of macrophage-conditioned media upon fibroblast differentiation. In general, the data obtained suggest the involvement of differentiation and polarization signals into modulation of pro- and anti-fibrogenic properties of macrophages.