Vasculogenic properties of adventitial Sca-1+CD45+ progenitor cells in mice: a potential source of vasa vasorum in atherosclerosis.

The cellular origins of vasa vasorum are ill-defined and may involve circulating or local progenitor cells. We previously discovered that murine aortic adventitia contains Sca-1+CD45+ progenitors that produce macrophages. Here we investigated whether they are also vasculogenic. In aortas of C57BL/6 mice, Sca-1+CD45+ cells were localised to adventitia and lacked surface expression of endothelial markers (<1% for CD31, CD144, TIE-2). In contrast, they did show expression of CD31, CD144, TIE-2 and VEGFR2 in atherosclerotic ApoE-/- aortas. Although Sca-1+CD45+ cells from C57BL/6 aorta did not express CD31, they formed CD31+ colonies in endothelial differentiation media and produced interconnecting vascular-like cords in Matrigel that contained both endothelial cells and a small population of macrophages, which were located at branch points. Transfer of aortic Sca-1+CD45+ cells generated endothelial cells and neovessels de novo in a hindlimb model of ischaemia and resulted in a 50% increase in perfusion compared to cell-free control. Similarly, their injection into the carotid adventitia of ApoE-/- mice produced donor-derived adventitial and peri-adventitial microvessels after atherogenic diet, suggestive of newly formed vasa vasorum. These findings show that beyond its content of macrophage progenitors, adventitial Sca-1+CD45+ cells are also vasculogenic and may be a source of vasa vasorum during atherogenesis.

Characterization of a resident population of adventitial macrophage progenitor cells in postnatal vasculature.

RATIONALE: Macrophages regulate blood vessel structure and function in health and disease. The origins of tissue macrophages are diverse, with evidence for local production and circulatory renewal. OBJECTIVE: We identified a vascular adventitial population containing macrophage progenitor cells and investigated their origins and fate. METHODS AND RESULTS: Single-cell disaggregates from adult C57BL/6 mice were prepared from different tissues and tested for their capacity to form hematopoietic colony-forming units. Aorta showed a unique predilection for generating macrophage colony-forming units. Aortic macrophage colony-forming unit progenitors coexpressed stem cell antigen-1 and CD45 and were adventitially located, where they were the predominant source of proliferating cells in the aortic wall. Aortic Sca-1(+)CD45(+) cells were transcriptionally and phenotypically distinct from neighboring cells lacking stem cell antigen-1 or CD45 and contained a proliferative (Ki67(+)) Lin(-)c-Kit(+)CD135(-)CD115(+)CX3CR1(+)Ly6C(+)CD11b(-) subpopulation, consistent with the immunophenotypic profile of macrophage progenitors. Adoptive transfer studies revealed that Sca-1(+)CD45(+) adventitial macrophage progenitor cells were not replenished via the circulation from bone marrow or spleen, nor was their prevalence diminished by depletion of monocytes or macrophages by liposomal clodronate treatment or genetic deficiency of macrophage colony-stimulating factor. Rather adventitial macrophage progenitor cells were upregulated in hyperlipidemic ApoE(-/-) and LDL-R(-/-) mice, with adventitial transfer experiments demonstrating their durable contribution to macrophage progeny particularly in the adventitia, and to a lesser extent the atheroma, of atherosclerotic carotid arteries. CONCLUSIONS: The discovery and characterization of resident vascular adventitial macrophage progenitor cells provides new insight into adventitial biology and its participation in atherosclerosis and provokes consideration of the broader existence of local macrophage progenitors in other tissues.

Bleeding outcomes after routine transradial primary angioplasty for acute myocardial infarction using eptifibatide and unfractionated heparin: a single-center experience following the HORIZONS-AMI trial.

OBJECTIVES: We sought to (1) determine the bleeding rates after primary percutaneous coronary intervention (PPCI) in our institution, where the default strategy has been transradial (TR) access in combination with unfractionated heparin (UFH) plus eptifibatide, and (2) compare these with the outcomes of patients treated with bivalirudin in HORIZONS-AMI. BACKGROUND: HORIZONS-AMI demonstrated that in PPCI undertaken via the transfemoral route, routine use of bivalirudin was associated with lower bleeding rates and improved mortality compared to routine use of UFH plus glycoprotein IIb/IIIa inhibitor (GPI). METHODS: This was a single-center prospective registry of consecutive patients undergoing PPCI from January 2009 to August 2011 at the Queen Elizabeth Hospital Birmingham, UK. Thirty-day major bleeding was defined as per the HORIZONS-AMI criteria and also according to TIMI and GUSTO scales. RESULTS: Of the 432 consecutive patients, 350 fulfilled entry criteria for HORIZONS-AMI. In contrast with HORIZONS-AMI, these subjects were older (62.5 ± 13.7 yr vs. 59.8 ± 11.1 yr, P < 0.05) with a higher rate of cardiogenic shock (6.3% vs. 0.8%, P < 0.0001). Despite this higher risk population, the rate of major bleeding was favorable (3.7% [95% CI: 2.0-6.3%] vs. 4.9% [4.0-6.1%], P = 0.32). Similarly, TIMI major bleeding (2.0% [0.8-4.1%] vs. 3.1% [2.3-3.4%], P = 0.10) and GUSTO severe or life-threatening bleeding (0.6% [0.1-2.5%] vs. 0.4% [0.2-0.9%], P = 0.75) were comparable. CONCLUSIONS: Routine TR access for PPCI using UFH plus GPI is associated with a low 30-day rate of major bleeding equivalent to the bivalirudin arm of HORIZONS-AMI. Default transradial access for PPCI permits routine use of a GPI without the penalty of high bleeding rates.

An in vivo method to quantify lymphangiogenesis in zebrafish.

BACKGROUND: Lymphangiogenesis is a highly regulated process involved in the pathogenesis of disease. Current in vivo models to assess lymphangiogenesis are largely unphysiologic. The zebrafish is a powerful model system for studying development, due to its rapid growth and transparency during early stages of life. Identification of a network of trunk lymphatic capillaries in zebrafish provides an opportunity to quantify lymphatic growth in vivo. METHODS AND RESULTS: Late-phase microangiography was used to detect trunk lymphatic capillaries in zebrafish 2- and 3-days post-fertilization. Using this approach, real-time changes in lymphatic capillary development were measured in response to modulators of lymphangiogenesis. Recombinant human vascular endothelial growth factor (VEGF)-C added directly to the zebrafish aqueous environment as well as human endothelial and mouse melanoma cell transplantation resulted in increased lymphatic capillary growth, while morpholino-based knockdown of vegfc and chemical inhibitors of lymphangiogenesis added to the aqueous environment resulted in decreased lymphatic capillary growth. CONCLUSION: Lymphatic capillaries in embryonic and larval zebrafish can be quantified using late-phase microangiography. Human activators and small molecule inhibitors of lymphangiogenesis, as well as transplanted human endothelial and mouse melanoma cells, alter lymphatic capillary development in zebrafish. The ability to rapidly quantify changes in lymphatic growth under physiologic conditions will allow for broad screening of lymphangiogenesis modulators, as well as help define cellular roles and elucidate pathways of lymphatic development.

Aortic calcification and femoral bone density are independently associated with left ventricular mass in patients with chronic kidney disease.

BACKGROUND: Vascular calcification and reduced bone density are prevalent in chronic kidney disease and linked to increased cardiovascular risk. The mechanism is unknown. We assessed the relationship between vascular calcification, femoral bone density and left ventricular mass in patients with stage 3 non-diabetic chronic kidney disease in a cross-sectional observational study. METHODOLOGY AND PRINCIPAL FINDINGS: A total of 120 patients were recruited (54% male, mean age 55 ± 14 years, mean glomerular filtration rate 50 ± 13 ml/min/1.73 m(2)). Abdominal aortic calcification was assessed using lateral lumbar spine radiography and was present in 48%. Mean femoral Z-score measured using dual energy x-ray absorptiometry was 0.60 ± 1.06. Cardiovascular magnetic resonance imaging was used to determine left ventricular mass. One patient had left ventricular hypertrophy. Subjects with aortic calcification had higher left ventricular mass compared to those without (56 ± 16 vs. 48 ± 12 g/m(2), P = 0.002), as did patients with femoral Z-scores below zero (56 ± 15 vs. 49 ± 13 g/m(2), P = 0.01). In univariate analysis presence of aortic calcification correlated with left ventricular mass (r = 0.32, P = 0.001); mean femoral Z-score inversely correlated with left ventricular mass (r = -0.28, P = 0.004). In a multivariate regression model that included presence of aortic calcification, mean femoral Z-score, gender and 24-hour systolic blood pressure, 46% of the variability in left ventricular mass was explained (P<0.001). CONCLUSIONS: In patients with stage 3 non-diabetic chronic kidney disease, lower mean femoral Z-score and presence of aortic calcification are independently associated with increased left ventricular mass. Further research exploring the pathophysiology that underlies these relationships is warranted.