The Phenotypic and Functional Features of Human M2 Macrophages Generated Under Low Serum Conditions

Intranasal Immunotherapy with M2 Macrophage Secretome Ameliorates Language Impairments and Autistic-like Behavior in Children

Background/Objectives: The intranasal delivery of various neurotropic substances is considered a new attractive therapeutic approach for treating neuropathologies associated with neuroinflammation and altered regeneration. Specific language impairment (SLI) that arises as a result of damage to the cortical speech zones during the developmental period is one of the most common problems in preschool children, and it is characterized by persistent difficulties in the acquisition, understanding, and use of language. This study's objective is to evaluate the efficacy and safety of intranasal immunotherapy using the M2 macrophage secretome as a rich source of immunoregulatory and neurotrophic factors for the treatment of severe language impairment in children. Methods: Seventy-one children (54 boys and 17 girls, aged 3 to 13 years) were recruited to participate in a clinical trial (NCT04689282) in two medical centers. The children were examined before, 1 month after, and 6 months after the start of therapy. In the vast majority of children (55/71), language impairment was associated with autistic-like symptoms and attention deficit hyperactivity disorder (ADHD). Results: Daily intranasal inhalations of M2 macrophage-conditioned medium (for 30 days) were well tolerated and led to a decrease in the severity of language impairments, autistic-like behavior, and ADHD symptoms. The clinical effect appeared within a month after the first procedure and persisted or intensified during a 6-month follow-up. Two-thirds of the children showed a clear clinical improvement, while the rest had less pronounced improvement. Conclusions: Thus, the use of the M2 macrophage secretome and its intranasal delivery is safe, well tolerated, and clinically effective in children with severe language impairments.

Intranasal immunotherapy with M2 macrophage soluble factors in post-COVID hyposmia: A pilot study

Olfactory dysfunction is an early marker of COVID-19 infection. However, individuals may develop chronic olfactory impairment for more than six months in 1-10 % of cases. The study's objective is to evaluate the efficacy and safety of intranasal immunotherapy using bioactive substances produced by M2 macrophages for the treatment of people with long-term post-COVID-19 hyposmia. Seven individuals with long-term persistent hyposmia (7 to 24 months), associated with PCR-confirmed coronavirus infection were evaluated for olfactory function at baseline, one, and six to twelve months after therapy. The intranasal inhalation of M2 macrophage conditioned medum (one time per day for 28-30 days) was well tolerated. Furthermore, olfactometry demonstrated that the patients restored their capacity to perceive (Kruskal-Wallis H test 14.123, p = 0.0009) and recognize odours (H = 11.674, p = 0.0029). In addition, the subjective evaluation of smell significantly improved (H = 11.935, p = 0.0026). At the 6- to 12-month follow-up, the majority of patients (5/7) reported extremely high levels of satisfaction with the outcomes, and the remaining two patients also felt generally positive about the therapy's success. Overall, our study showed that the use of intranasal inhalations as a method of delivering bioactive factors and the conditioned medium of M2 macrophages as a therapeutic agent are both safe, well tolerated and, according to preliminary data, clinically effective in the treatment of patients with long-term post-COVID-19 hyposmia.

Effect of Differently Polarized Human Macrophages on the SH-SY5Y Cells Damaged by Ischemia and Hypoxia In Vitro

Macrophages are the major cells of innate immunity with a wide range of biological effects due to their great plasticity and heterogeneity. Macrophages play a key role in neuroregeneration following nervous tissue injury. However, the neuroregenerative potential of various macrophage phenotypes, including those polarized by efferocytosis, remains unexplored. The aim of this study was to compare the neuroregenerative and neuroprotective activity of soluble factors secreted by variously activated human macrophages on the functions of neural progenitors in an in vitro model of ischemia or ischemia/hypoxia. Macrophages were polarized by interferon-γ (M1), IL-4 (M2a), or interaction with apoptotic cells (M2(LS)). The effect of macrophages conditioned media on the proliferation, differentiation, and survival of SH-SY5Y cells damaged by serum deprivation alone (ischemic conditions) or in combination with CoCl2 (ischemic/hypoxic conditions) was assessed. All studied macrophages stimulated the proliferation and differentiation of SH-SY5Y cells. On day 3, the pro-proliferating effect of M1 and M2 was similar and did not depend on the severity of the damaging effect (ischemia or ischemia/hypoxia), while on day 7 and under ischemic/hypoxic conditions, the effects of M2(LS) exceeded those of M1 and M2a cells. The prodifferentiation effects of macrophages were manifested in both short- and long-term cultures, mainly under ischemic/hypoxic conditions, and were most characteristic of M2(LS) cells. Importantly, the ischemia/hypoxia model was accompanied by the pronounced death of SH-SY5Y cells. Only macrophages with the M2 phenotype demonstrated antiapoptotic activity, and the effect of M2(LS) was higher than that of M2a. The results obtained indicate that human macrophages have neuroprotective and neuroregenerative activity, which is mediated by soluble factors, is most characteristic for macrophages activated by efferocytosis (M2(LS)), and is most prominent under in vitro conditions simulating the combined effect of ischemia/hypoxia.

Human Macrophages Polarized by Interaction with Apoptotic Cells Produce Fibrosis-Associated Mediators and Enhance Pro-Fibrotic Activity of Dermal Fibroblasts In Vitro

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.

Exosomes from chondrocytes overexpressing miR-214-3p facilitate M2 macrophage polarization and angiogenesis to relieve Legg Calvé-Perthes disease

OBJECTIVE

Legg-Calvé-Perthes disease (LCPD) is a partial or total necrosis of femoral head bone caused by blood supply disorder and its etiology is not clear. Studies have revealed that microRNA-214-3p (miR-214-3p) plays a vital role in LCPD, however, its exact mechanism is still unclear. In this study, we investigated the potential role of chondrocytes-derived exosomes carrying miR-214-3p (exos-miR-214-3p) in the pathogenesis of LCPD.

METHODS

RT-qPCR was performed to evaluate miR-214-3p expression level in femoral head cartilage, serum and chondrocytes of patients with LCPD, as well as dexamethasone (DEX)-exposed TC28 cells. Effects of exos-miR-214-3p on the proliferation and apoptosis were verified via MTT assay, TUNEL staining and caspase3 activity assay. The M2 macrophage markers were assessed by flow cytometry, RT-qPCR and Western blot. Moreover, angiogenic effects of human umbilical vein endothelial cells (HUVECs) were tested using CCK-8 and tube formation assays. Bioinformatics prediction, luciferase assay and ChIP were applied to verify the association between ATF7, RUNX1 and miR-214-3p.

RESULTS

miR-214-3p was found to be decreased in patients with LCPD and DEX-treated TC28 cells, of which overexpression promoted cell proliferation and suppressed apoptosis. Mechanistically, exos-miR-214-3p facilitated M2 polarization by ATF7/TLR4 axis and HUVECs angiogenesis via RUNX1/VEGFA axis.

CONCLUSION

miR-214-3p alleviates LCPD by promoting M2 polarization of macrophages and angiogenesis.

Effect of M2 Macrophage-Derived Soluble Factors on Behavioral Patterns and Cytokine Production in Various Brain Structures in Depression-Like Mice

We studied the effect of soluble factors derived from human macrophages polarized to M2 phenotype under conditions of serum deprivation (M2-SF) on behavioral pattern and cytokine production in various brain structures in mice with modeled stress-induced depression. Intranasal administration of M2-SF for 7 days led to stimulation of locomotor and exploratory activities and a decrease in emotional reactivity in the open-field test as well as reduction in depression-like behavior in Porsolt forced swimming test and a decrease in anxiety and anhedonia. Correction of depression-like behavior was accompanied by down-regulation of proinflammatory cytokines (IL-1β, IL-6, TNFα, and IFNγ) in pathogenetically important brain structures (striatum, hippocampus, and frontal cortex). These data indicate that the antidepressant potential of M2 type macrophages can be mediated by the anti-inflammatory effects of M2-SF.

Influence of Secretome of Different Functional Phenotypes of Macrophages on Proliferation, Differentiation, and Collagen-Producing Activity of Dermal Fibroblasts In Vitro

We studied the effect of conditioned media of GM-CSF-differentiated human macrophages polarized in M1(LPS), M2a(IL-4), M2c(dexamethasone), and M2(low serum) phenotypes on proliferation, differentiation, and collagen-producing activity of dermal fibroblasts. It was found that M1(LPS) and M2a(IL-4) were characterized by moderate influence on functional activity of fibroblasts. At the same time, soluble factors of M2c(dexamethasone) significantly enhanced the proliferative response of fibroblasts, but not their differentiation and type I collagen production. On the contrary, M2(low serum) generated under conditions of growth factors deficiency had a pronounced stimulating effect on the differentiation of fibroblasts and production of type I collagen by these cells, but moderately stimulated the fibroblast proliferation. Thus, the secretory activity of various functional phenotypes of macrophages is an important mechanism of fibrogenesis regulation.

Effect of M2 Macrophage-Derived Soluble Factors on Proliferation and Apoptosis of SH-SY5Y Cells

Macrophages play the key role in the regulation of neuroregeneration. For evaluation of the neuroregenerative potential of M2 macrophages, we studied the effect of macrophages polarized with IL-4 (M2a (IL-4)) and by efferocytosis under conditions of serum deprivation (LS, Low Serum; M2(LS)) on proliferative activity and apoptosis of SH-SY5Y cells under conditions of deficiency of growth/serum factors. Conditioned media of both M2(LS) and M2a(IL-4) stimulated proliferation of SH-SY5Y cells. Moreover, soluble factors of M2(LS) and M2a(IL-4) reduced the degree of early apoptosis of SH-SY5Y cells and the protective effect of M2(LS) was observed at earlier terms of culturing. Our findings suggest that M2 macrophages have high neuroregenerative potential that is mediated through soluble factors and manifests itself both in stimulation of proliferation and inhibition of apoptosis of SH-SY5Y cells.

Efferocytosis Modulates Arginase-1 and Tyrosine Kinase Mer Expression in GM-CSF-Differentiated Human Macrophages

We studied the expression of arginase-1 (Arg1) and tyrosine kinase Mer (MerTK) in GMCSF-differentiated human macrophage populations М0, М1(IFNγ), М2а(IL-4), and М2(low serum) generated under conditions of growth/serum factor deficiency. The maximum relative content of Arg1+ and MerTK+ cells was found in М2 macrophage populations: М2а(IL-4) and М2(low serum). As the uptake of apoptotic cells is the key mechanism of M2 polarization during M2(low serum) generation, we performed a special series of experiments and showed that incubation with allogeneic apoptotic neutrophils significantly increased the percentages of CD206+ macrophages co-expressing Arg1 and MerTK.

Allostimulatory activity as a criterion of the functional phenotype of human macrophages

The functional phenotype of macrophages (Mφ) is determined by both differentiation factors and polarization stimuli. In mouse Mφ could be easily divided into the distinct Mφ subtypes. However, the identification of human M1 and M2 cells is much more difficult due to the lack of M1- or M2-specific markers. We assumed that the Mφ capacity to induce T cell proliferation in mixed leukocyte culture, or allostimulatory activity, may be a marker of Mφ functional phenotype. We compared the allostimulatory activity of Mφ differentiated with GM-CSF or M-CSF and polarized into M1, M2a, M2c subtypes using appropriate stimuli. GM-CSF-differentiated M1 Mφ showed pronounced allostimulatory activity whereas the polarization into M2a and M2c of GM-CSF-differentiated Mφ was associated with decreased allostimulatory activity. M-CSF-differentiated M1 Mφ demonstrated the moderate increasing of allostimulatory activity but its level has never reached that of GM-CSF-activated M1. The level of allostimulatory activity of M2a and M2c M-CSF-induced Mφ was comparable to that of GM-CSF-induced M2a and M2c Mφ. Thus, low allostimulatory activity is a common property of human M2a and M2c macrophages regardless of the differentiating factor and a polarizing stimulus and can be used to distinguish between M1 and M2 phenotypes.

Recent progress on developing exogenous monocyte/macrophage-based therapies for inflammatory and degenerative diseases

Cell-based therapies are a rapidly developing area of regenerative medicine as dynamic treatments that execute therapeutic functions multimodally. Monocytes and macrophages, as innate immune cells that control inflammation and tissue repair, are increasing popular clinical candidates due to their spectrum of functionality. In this article, we review the role of monocytes and macrophages specifically in inflammatory and degenerative disease pathology and the evidence supporting the use of these cells as an effective therapeutic strategy. We compare current strategies of exogenously polarized monocyte/macrophage therapies regarding dosage, delivery and processing to identify outcomes, advances and challenges to their clinical use. Monocytes/macrophages hold the potential to be a promising therapeutic avenue but understanding and optimization of disease-specific efficacy is needed to accelerate their clinical use.

Intranasal delivery of M2 macrophage-derived soluble products reduces neuropsychological deficit in patients with cerebrovascular disease: a pilot study

Objective:

We assessed the safety and clinical effectiveness of intranasal therapy with M2 macrophage-derived soluble products (M2-SPs) for treating patients with cerebrovascular disease (CVD).

Materials and methods:

The protocol of the study was registered at www.ClinicalTrails.gov (NCT02957123). The study group comprised 30 patients with chronic CVD. Neurological status was examined before therapy and at 1- and 6-month follow–up. Concentrations of 32 cytokines in the blood serum were evaluated before and 1 month after therapy onset. Neurological assessment was conducted with the following scales: Subjective Assessment of Clinical (neurological) Symptoms (SACS), Hospital Anxiety and Depression Scale (HADS), Functional Mobility Assessment in Eldery Patients (FMA), and Montreal Cognitive Assessment (MoCa).

Results:

M2-SPs treatment (once daily for 28~30 days) was found to be safe and well tolerated. Neuropsychological improvements showed the amelioration of neurological symptoms, reduction in anxiety and depression levels, improvement in balance and gait ability as well as cognitive functions. Clinical effects could be detected at the end of treatment course and was stable during 6-month follow-up. Blood serum cytokine evaluation demonstrated diminished baseline levels of many cytokines including those with neurotrophic activity (brain-derived neurotrophic factor, BDNF; hepatocyte growth factor, HGF; migration inhibitory factor, MIF). Upon treatment, most pronounced clinical responses were observed in patients with most severe cytokine deficiency and post-therapy normalization of MIF and HGF levels.

Conclusion:

Intranasal therapy with M2-SPs is safe and according to preliminary data reduces neuropsychological deficit in patients with chronic CVD. The positive effect of M2-SPs treatment seems to be HGF- and MIF-dependent.

Autocrine VEGF signalling on M2 macrophages regulates PD-L1 expression for immunomodulation of T cells

M2‐polarized macrophages, on one hand, can promote tumour vascularization by producing proangiogenic factors, such as vascular endothelial growth factor (VEGF). On the other hand, the expression of VEGF receptors (VEGFR) in this cell lineage was also reported. Although the function of VEGF/VEGFR axis plays a pivotal role in macrophages infiltration and angiogenesis, however, there is still lack of the direct evidence to show the role of VEGF as an autocrine operating in M2 macrophages, particularly for immunomodulation. In our study, we surprisingly discovered that M2 macrophages polarized by baicalin can simultaneously express VEGF and its receptors. Taking advantage of this unique culture system, we were able to investigate the biological activity of M2 macrophages in response to the autocrine VEGF milieu. Our results showed that the expression of programmed death‐ligand 1 (PD‐L1) on M2 macrophages was significantly up‐regulated in autocrine VEGF milieu. Through the blockade of autocrine VEGF signalling, PD‐L1 expression on M2 macrophages was dramatically down‐regulated. Furthermore, transplantation of PD‐L1⁺ M2 macrophage stimulated by autocrine VEGF into allogeneic mice significantly suppressed host CD4⁺/CD8⁺ T cells in the peripheral blood and increased CD4⁺CD25⁺ regulatory T cells in the bone marrow. In conclusion, our findings provide a novel biological basis to support the current successful strategy using combined VEGF/PD‐1 signalling blockade in cancer therapy.

Lower inflammatory markers in women with antenatal depression brings the M1/M2 balance into focus from a new direction

BACKGROUND

Antenatal depression and use of serotonin reuptake inhibitors (SSRI) in pregnancy have both been associated with an increased risk of poor pregnancy outcomes, such as preterm birth and impaired fetal growth. While the underlying biological pathways for these complications are poorly understood, it has been hypothesized that inflammation may be a common physiological pathway. The aim of the present study was to assess peripheral inflammatory markers in healthy women, women with antenatal depression, and in women using SSRI during pregnancy.

METHODS

160 healthy pregnant controls, 59 women with antenatal depression and 39 women on treatment with SSRIs were included. The relative levels of 92 inflammatory proteins were analyzed by proximity extension assay technology.

RESULTS

Overall, 23 of the inflammatory markers were significantly lower in women with antenatal depression and in women on treatment with SSRIs in comparison with the healthy controls. No difference in any of the inflammatory markers was observed between women with antenatal depression and those who were using SSRI. Top three inflammatory markers that were down-regulated in women with antenatal depression were TNF-related apoptosis-inducing ligand (TRAIL), p=0.000001, macrophage colony-stimulating factor 1 (CSF-1), p=0.000004, and fractalkine (CX3CL1), p=0.000005. Corresponding inflammatory markers in SSRI users were CSF-1, p=0.000011, vascular endothelial growth factor A (VEGF-A), p=0.000016, and IL-15 receptor subunit alpha (IL-15RA), p=0.000027. The inflammatory markers were negatively correlated with cortisone serum concentrations in controls, but not in the cases. Differential DNA methylation of was found for seven of these inflammatory markers in an independent epigenetics cohort.

CONCLUSION

Women with antenatal depression or on SSRI treatment have lower levels of a number of peripheral inflammatory markers than healthy pregnant controls. Hypothetically, this could be due to dysregulated switch to the pro-M2 milieu that characterizes normal third trimester pregnancy. However, longitudinal blood sampling is needed to elucidate whether the presumably dysregulated M2 shift is driving the development of antenatal depression or is a result of the depression.