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Despite decades of effort aimed at developing clinically effective cell therapies, including mixed population mononuclear cells, to revascularize the ischemic limb, there remains a paucity of patient-based studies that inform the function and fate of candidate cell types. In this study, we showed that circulating proangiogenic/arteriogenic monocytes (PAMs) expressing the FcγIIIA receptor CD16 were elevated in patients with chronic limb-threatening ischemia (CLTI), and these amounts decreased after revascularization. Unlike CD16-negative monocytes, PAMs showed large vessel remodeling properties in vitro when cultured with endothelial cells and smooth muscle cells and promoted salvage of the ischemic limb in vivo in a mouse model of hindlimb ischemia. PAMs showed a propensity to migrate toward and bind to ischemic muscle and to secrete angiogenic/arteriogenic factors, vascular endothelial growth factor A (VEGF-A) and heparin-binding epidermal growth factor. We instigated a first-in-human single-arm cohort study in which autologous PAMs were injected into the ischemic limbs of five patients with CLTI. Greater than 25% of injected cells were retained in the leg for at least 72 hours, of which greater than 80% were viable, with evidence of enhanced large vessel remodeling in the injected muscle area. In summary, we identified up-regulation of a circulatory PAM subpopulation as an endogenous response to limb ischemia in CLTI and tested a potentially clinically relevant therapeutic strategy.

Use of autologous cells isolated from elderly patients with multiple comorbidities may account for the modest efficacy of cell therapy in patients with chronic limb threatening ischemia (CLTI). We aimed to determine whether proarteriogenic monocyte/macrophages (Mo/MΦs) from patients with CLTI were functionally impaired and to demonstrate the mechanisms related to any impairment. Proarteriogenic Mo/MΦs isolated from patients with CLTI were found to have an impaired capacity to promote neovascularization in vitro and in vivo compared with those isolated from healthy controls. This was associated with increased expression of human HIV-1 TAT interactive protein-2 (HTATIP2), a transcription factor known to suppress angiogenesis/arteriogenesis. Silencing HTATIP2 restored the functional capacity of CLTI Mo/MΦs, which was associated with increased expression of arteriogenic regulators Neuropilin-1 and Angiopoietin-1, and their ability to enhance angiogenic (endothelial tubule formation) and arteriogenic (smooth muscle proliferation) processes in vitro. In support of the translational relevance of our findings, silencing HTATIP2 in proarteriogenic Mo/MΦs isolated from patients with CLTI rescued their capacity to enhance limb perfusion in the ischemic hindlimb by effecting greater angiogenesis and arteriogenesis. Ex vivo modulation of HTATIP2 may offer a strategy for rescuing the functional impairment of pro-angio/arteriogenic Mo/MΦs prior to autologous delivery and increase the likelihood of clinical efficacy.

A third of patients with critical limb ischemia (CLI) will eventually require limb amputation. Therapeutic neovascularization using unselected mononuclear cells to salvage ischemic limbs has produced modest results. The TIE2-expressing monocytes/macrophages (TEMs) are a myeloid cell subset known to be highly angiogenic in tumours. This study aimed to examine the kinetics of TEMs in patients with CLI and whether these cells promote neovascularization of the ischemic limb. Here we show that there are 10-fold more circulating TEMs in CLI patients, and removal of ischemia reduces their numbers to normal levels. TEM numbers in ischemic muscle are two-fold greater than normoxic muscle from the same patient. TEMs from patients with CLI display greater proangiogenic activity than TIE2-negative monocytes in vitro. Using a mouse model of hindlimb ischemia, lentiviral-based Tie2 knockdown in TEMs impaired recovery from ischemia, whereas delivery of mouse macrophages overexpressing TIE2, or human TEMs isolated from CLI patients, rescued limb ischemia. These data suggest that enhancing TEM recruitment to the ischemic muscle may have the potential to improve limb neovascularization in CLI patients., (Copyright © 2013 The Authors. Published by John Wiley and Sons, Ltd on behalf of EMBO.)

Therapeutic neovascularisation using angiogenic cells has been hampered by the loss of cells from the target tissue. Encapsulation of these cells within a semi-permeable membrane could improve their retention within the ischaemic tissue without affecting the excretion of the angiogenic growth factors produced. Bio-spraying is a novel cell-handling technique that does not adversely affect cell viability. We used this technique to encapsulate human peripheral blood monocytes and found that cell viability, cell phenotype and functional downstream angiogenic signalling were preserved. Encapsulation of monocytes with macrophage-colony stimulating factor resulted in increased vascular-endothelial growth factor production and enhanced angiogenic function. Bio-spraying/encapsulation has the potential to enhance the efficacy of current angiogenic cell therapy strategies and merits further investigation.

It is now clear that the monocyte/macrophage has a crucial role in the development of atherosclerosis. This cell appears to be involved in all stages of atherosclerotic plaque development and is increasingly seen as a candidate for therapeutic intervention and as a potential biomarker of disease progression and response to therapy. The main mechanisms related to the activity of the monocyte/macrophage that have been targeted for therapy are those that facilitate recruitment, cholesterol metabolism, inflammatory activity and oxidative stress. There is also increasing evidence that there is heterogeneity within the monocyte/macrophage population, which may have important implications for plaque development and regression. A better insight into how specific phenotypes may influence plaque progression should facilitate the development of novel methods of imaging and more refined treatments.

Objective: Galectin-3 (Gal-3) is a 26-kDa lectin known to regulate many aspects of inflammatory cell behavior. We assessed the hypothesis that increased levels of Gal-3 contribute to atherosclerotic plaque progression by enhancing monocyte chemoattraction through macrophage activation., Methods and Results: Gal-3 was found to be upregulated in unstable plaque regions of carotid endarterectomy (CEA) specimens compared with stable regions from the same patient (3.2-fold, P<0.05) at the mRNA (n=12) and (2.3-fold, P<0.01) at the protein level (n=9). Analysis of aortic tissue from ApoE-/- mice on a high fat diet (n=14) and wild-type controls (n=9) showed that Gal-3 mRNA and protein levels are elevated by 16.3-fold (P<0.001) and 12.2-fold (P<0.01) and that Gal-3 staining colocalizes with macrophages. In vitro, conditioned media from Gal-3-treated human macrophages induced an up to 6-fold increase in human monocyte chemotaxis (P<0.01, ANOVA), an effect that was reduced by 66 and 60% by Pertussis Toxin (PTX) and the Vaccinia virus protein 35K, respectively. Microarray analysis of human macrophages and subsequent qPCR validation confirmed the upregulation of CC chemokines in response to Gal-3 treatment., Conclusions: Our data suggest that Gal-3 is both a marker of atherosclerotic plaque progression and a central contributor to the pathology by amplification of key proinflammatory molecules.

Objective: To investigate the importance of monocyte recruitment in thrombus resolution and the role of cysteine-cysteine (CC) chemokines and the CC chemokine receptor, CCR2, in this process., Methods: Peritoneal macrophages, monocyte chemotactic protein 1 (MCP1), or carrier solutions were injected into thrombi induced in the vena cava of rats. Caval thrombi were also formed in CCR2-/- and MCP1-/- mice and in wild-type mice transfected with an adenoviral construct expressing a broad-spectrum CC receptor antagonist., Results: Direct administration of peritoneal macrophages decreased thrombus size by more than fivefold and increased recanalization by more than fourfold compared with controls (P < .001). A 100-ng MCP1dose reduced thrombus size by more than sixfold (P < .01) and increased recanalization by more than sevenfold (P < .01), without affecting macrophage recruitment. Deletion of CCR2 or blockade of all CC chemokines inhibited both monocyte recruitment (P < .05) and thrombus resolution (P < .01), but knocking out MCP-1 had no effect., Conclusion: Increasing macrophage numbers in the thrombus enhances its resolution. MCP1 treatment enhances resolution by stimulating recanalization, independent of an effect on monocyte recruitment. CCR2 deficiency has the same effect as blockade of all CC chemokines. CCR2 receptor activation may therefore be an important mechanism in monocyte recruitment into venous thrombi and could be targeted to promote their resolution.

Objective: Monocyte fibrinolytic activity may influence thrombus resolution. The balance between uPA and PAI-2 could determine the fibrinolytic activity of the monocyte. Inhibiting PAI-2 production using specific antisense sequences might alter this balance. Selecting effective sequences is a problem as prediction of the secondary structure of target mRNA is difficult. This study reports the modification of a cell free system for rapid antisense screening., Methods: Five 18-19 mer oligodeoxynucleotides (ODN), sequences A, B, K, T and Q, and their matched scrambled controls were designed and screened using a modified rabbit reticulocyte lysate transcription and translation system (RRL). Intracellular uptake of ODNs was confirmed by fluorescence microscopy, scanning laser confocal microscopy and fluorimetry. Monocytes were transfected with a liposome/ODN complex using sequences A, B, A + B combined, or T and PAI-2 levels measured by ELISA. Inhibition of PAI-2 production was calculated as a percentage of control levels (baseline and scrambled)., Results: (i) RRL System--Sequence A was the most effective inhibitor of PAI-2 production in this system (median 63%) compared with sequences, B median 9%, K median 14%, T median 11% and Q median -8% respectively (n = 3). Sequence A was the only sequence, which always inhibited PAI-2. This was confirmed using fluorescently labelled protein (n = 2). (ii) Monocyte transfection--Fluorescence microscopy and fluorimetry showed that intracellular delivery of labelled antisense was only achieved when a liposome was used. Transfection of monocytes extracted from 5 subjects showed that sequence A significantly reduced PAI-2 production (mean % 41.4, sem 9.1) compared with sequences B (mean% 3.4, sem 8.9, p = 0.04), A + B (mean % 0.4, sem 7.8, p = 0.04), and T (mean % 5.4, sem 4.9, p = 0.01). Further studies using sequence A on cells from 10 subjects showed a significant reduction in monocyte PAI-2 production (27.6 ng/ml, sem 3.9) compared with matched scrambled controls (mean 38.3 ng/ml, sem 4.5, p = 0.0112) and baseline (mean 51.4 ng/ml, sem 6.7, p = 0.0009)., Conclusion: Use of the RRL screening system allowed the selection of a novel antisense sequence, which significantly reduced PAI-2 production in monocytes.

Background: Our previous studies showed that the direct injection of an adenovirus construct expressing urokinase-type plasminogen activator (uPA) into experimental venous thrombi significantly reduces thrombus weight. The systemic use of adenovirus vectors is limited by inherent hepatic tropism and inflammatory response. As macrophages are recruited into venous thrombi, it is reasonable to speculate that these cells could be used to target the adenovirus uPA (ad-uPA) gene construct to the thrombus. The aims of this study were to determine whether macrophages transduced with ad-uPA have increased fibrinolytic activity and whether systemic injection of transduced cells could be used to target uPA expression to the thrombus and reduce its size. Methods: The effect of up-regulating uPA was examined in an immortalized macrophage cell line (MM6) and macrophages differentiated from human blood monocyte-derived macrophages (HBMMs). Cells were infected with ad-uPA or blank control virus (ad-blank). Fibrinolytic mediator expression, cell viability, and cytokine expression were measured by activity assays and enzyme-linked immunosorbent assays. Monocyte migration was measured using a modified Boyden chamber assay. A model of venous thrombosis was developed and characterized in mice with severe combined immunodeficiency (SCID). This model was used to study whether systemically administered macrophages over-expressing uPA reduced thrombus size. Uptake of HBMMs into the thrombus induced in these mice was confirmed by a combination of PKH2-labeled cell tracking and colocalization with human leukocyte antigen (HLA) by immunohistology. Results: Compared with ad-blank, treated HBMMs transduction with ad-uPA increased uPA production by >1000-fold (P = .003), uPA activity by 150-fold (P = .0001), and soluble uPA receptor (uPAR) by almost twofold (P = .043). Expression of plasminogen activator inhibitor (PAI-1) and PAI-2 was decreased by about twofold (P = .011) and threefold (P = .005), respectively. Up-regulation of uPA had no effect on cell viability or inflammatory cytokine production compared with ad-blank or untreated cells. Ad-uPA transduction increased the migration rate of HBMMs (about 20%, P = .03) and MM6 cells (>twofold, P = .005) compared with ad-blank treated controls. Human macrophage recruitment into the mouse thrombus was confirmed by the colocalization of HLA with the PKH2-marked cells. Systemic injection of uPA-up-regulated HBMMs reduced thrombus weight by approximately 20% compared with ad-blank (P = .038) or sham-treated controls (P = .0028). Conclusion: Transduction of HBBM with ad-uPA increases their fibrinolytic activity. Systemic administration of uPA up-regulated HBBMs reduced thrombus size in an experimental model of venous thrombosis. Alternative methods of delivering fibrinolytic agents are worth exploring. [Copyright &y& Elsevier]

Assessments of venous thrombi and atherosclerosis were performed in vivo using magnetic resonance imaging of the inferior vena cava and of the brachiocephalic artery (BCA).[2],[3] Next, we assessed whether removal of DVT would affect the plaque. Keywords: atherosclerosis; inflammation; magnetic resonance imaging; molecular imaging; monocytes; thromboinflammation; venous thrombosis EN atherosclerosis inflammation magnetic resonance imaging molecular imaging monocytes thromboinflammation venous thrombosis 1945 1947 3 06/16/23 20230620 NES 230620 Deep vein thrombosis (DVT) and atherosclerosis cause significant morbidity and can lead to death. Here, we hypothesized that an increase in arterial events after venous thrombosis occurs because DVT directly accelerates atherosclerosis through a process involving DVT-induced inflammation. [Extracted from the article]