Characterization of Human Monocyte Subsets by Whole Blood Flow Cytometry Analysis

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can ...

Westmead hospital

The University of Sydney

The emerging understanding of macrophage subsets and their functions in the atherosclerotic plaque has led to the consensus that M1 macrophages are pro-atherogenic while M2 macrophages may promote plaque stability, primarily though their tissue repair and anti-inflammatory properties. As such, modulating macrophage function to promote plaque stability is an exciting therapeutic prospect. This review will outline the involvement of the different macrophage subsets throughout atherosclerosis progression and in models of regression. It is evident that much of our understanding of macrophage function comes from in vitro or small animal models and, while such knowledge is valuable, we have much to learn about the roles of the macrophage subsets in the clinical setting in order to identify the key pathways to target to possibly promote plaque stability. 

Clinical significance of macrophage phenotypes in cardiovascular disease.

Specific monocyte and macrophage subsets have been implicated in atherosclerosis, with intermediate monocytes proportionally elevated in cardiovascular disease and M1 macrophages abundant in unstable atherosclerotic plaques. While several studies have shown altered proportions of these subsets in atherosclerosis, studies examining functional and phenotypic subset alterations remain scarce.

Human classical monocytes display unbalanced M1/M2 phenotype with increased atherosclerotic risk and presence of disease.

Pediatric burns remain a common injury after which many patients develop a severe form of scarring known as hypertrophic scarring. The formation of the hypertrophic scar arises from excessive production of collagen during wound healing. Wound repair and regeneration represents a complex process that is accomplished through many biological processes involving various cell types, extracellular matrix proteins, cytokines, and other mediators. One important cell type is the monocyte, which displays an altered profile in many wound models. These profile changes may function as biomarkers, reflecting and/or influencing the clinical outcome of the healing response seen after burn injury. Monocytes circulate in the blood and then enter into the tissue, where they further differentiate into macrophages, which serve various functions, including immune defense and tissue remodeling. More recently, these cells have been characterized in detail based on cell surface markers expressed and genes up-regulated, enabling subpopulations to be identified. Fibrocytes, which are also monocyte-derived cells, have been shown to contribute to collagen production in the burn wound and are associated with hypertrophic scarring. They may represent a unique subpopulation of macrophages that, due to their production of collagen, promote tissue fibrosis rather than wound repair. A better understanding of the relationship among monocytes, fibrocytes, and macrophages may improve our appreciation of the factors influencing scar formation and tissue remodeling.

A Review of Monocytes and Monocyte-Derived Cells in Hypertrophic Scarring Post Burn.

Increasing evidence shows that CC-chemokines promote inflammatory-driven angiogenesis, with little to no effect on hypoxia-mediated angiogenesis. Inhibition of the CC-chemokine class may therefore affect angiogenesis differently depending on the pathophysiological context. We compared the effect of CC-chemokine inhibition in inflammatory and physiological conditions. , the broad-spectrum CC-chemokine inhibitor "35K" inhibited inflammatory-induced endothelial cell proliferation, migration, and tubulogenesis, with more modest effects in hypoxia. , adenoviruses were used to overexpress 35K (Ad35K) and GFP (AdGFP, control virus). Plasma chemokine activity was suppressed by Ad35K in both models. In the periarterial femoral cuff model of inflammatory-driven angiogenesis, overexpression of 35K inhibited adventitial neovessel formation compared with control AdGFP-infused mice. In contrast, 35K preserved neovascularization in the hindlimb ischemia model and had no effect on physiological neovascularization in the chick chorioallantoic membrane assay. Mechanistically, 2 key angiogenic proteins (VEGF and hypoxia-inducible factor-1α) were conditionally regulated by 35K, such that expression was inhibited in inflammation but was unchanged in hypoxia. In conclusion, CC-chemokine inhibition by 35K suppresses inflammatory-driven angiogenesis while preserving physiological ischemia-mediated angiogenesis  conditional regulation of VEGF and hypoxia-inducible factor-1α. CC-chemokine inhibition may be an alternative therapeutic strategy for suppressing diseases associated with inflammatory angiogenesis without inducing the side effects caused by global inhibition.- Ridiandries, A., Tan, J. T. M., Ravindran, D., Williams, H., Medbury, H. J., Lindsay, L., Hawkins, C., Prosser, H. C. G., Bursill, C. A. CC-chemokine class inhibition attenuates pathological angiogenesis while preserving physiological angiogenesis.

CC-chemokine class inhibition attenuates pathological angiogenesis while preserving physiological angiogenesis.

Atherogenesis is dependent upon monocyte influx into the vessel wall. In humans, three monocyte subsets exist, the number and function of which are significantly altered in cardiovascular disease (CVD). Whether such alterations arise in individuals with a perturbed lipid profile remains largely unanswered, but is important to delineate, as adoption of a pro-inflammatory state may promote plaque formation. Here, we compared the inflammatory status of monocyte subsets and determined whether monocyte inflammatory changes are evident in individuals with a perturbed lipid profile.

Monocyte inflammatory profile is specific for individuals and associated with altered blood lipid levels.

Studies disrupting the chemokine pathway CX3CL1 (fractalkine)/ CX3CR1 have shown decreased atherosclerosis in animal models but the techniques used to interrupt the pathway have not been easily translatable into human trials. DNA vaccination potentially overcomes the translational difficulties. We evaluated the effect of a DNA vaccine, targeted to CX3CR1, on atherosclerosis in a murine model and examined possible mechanisms of action. DNA vaccination against CX3CR1, enhanced by dendritic cell targeting using DEC-205 single chain variable region fragment (scFv), was performed in 8 week old ApoE-/- mice, fed a normal chow diet. High levels of anti-CX3CR1 antibodies were induced in vaccinated mice. There were no apparent adverse reactions to the vaccine. Arterial vessels of 34 week old mice were examined histologically for atherosclerotic plaque size, macrophage infiltration, smooth muscle cell infiltration and lipid deposition. Vaccinated mice had significantly reduced atherosclerotic plaque in the brachiocephalic artery. There was less macrophage infiltration but no significant change to the macrophage phenotype in the plaques. There was less lipid deposition in the lesions, but there was no effect on smooth muscle cell migration. Targeted DNA vaccination to CX3CR1 was well tolerated, induced a strong immune response and resulted in attenuated atherosclerotic lesions with reduced macrophage infiltration. DNA vaccination against chemokine pathways potentially offers a potential therapeutic option for the treatment of atherosclerosis.

DEC205-DC targeted DNA vaccine against CX3CR1 protects against atherogenesis in mice.

Monocytes are likely to play a significant role in the pathogenesis of preeclampsia (PE) and intrauterine fetal growth restriction (IUGR), given their role in homeostasis and tissue repair. Our aim was to study the gestational changes in monocytes in normal pregnancy and to determine whether monocyte subsets and phenotype are altered in pregnancy complications, such as PE and IUGR.

Helen Williams

Department of Surgery,
Vascular Biology Research Centre,
Department of Surgery, Vascular Biology Research Centre

Westmead hospital

Characterization of Human Monocyte Subsets by Whole Blood Flow Cytometry Analysis

Helen Williams

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Surgery,Vascular Biology Research Centre,Department of Surgery, Vascular Biology Research Centre

Westmead hospital

Characterization of Human Monocyte Subsets by Whole Blood Flow Cytometry Analysis

Department of Surgery,
Vascular Biology Research Centre,
Department of Surgery, Vascular Biology Research Centre