title: Investigating the extremes of the continuum of paracrine functions in CD34-/CD31+ CACs across diverse populations.
abstract: Paracrine function of circulating angiogenic cells (CACs) is thought to contribute to vascular maintenance. We previously identified S100A8 and S100A9 secreted from physically inactive individuals' CD34-/CD31+CACs as negative regulators of capillary-like network formation. The purpose of this study was to investigate further the extremes of the continuum of CAC paracrine actions using two distinctly different groups representing "healthy" and "impaired" CAC function. We aimed to determine how capillary-like network formation in human umbilical vein endothelial cells (HUVECs) is affected by S100A8 and S100A9 in concentrations secreted by CACs from different ends of the health spectrum. CD34-/CD31+CACs were isolated and cultured from 10 impaired function individuals defined as older (50-89 yr), non-ST-elevation myocardial infarction patients and 10 healthy individuals defined as younger (18-35 yr), healthy individuals, and conditioned media (CM) was generated. CM from the impaired function group's CACs significantly diminished network formation compared with CM from the healthy group (P < 0.05). We identified elevations in S100A8, S100A9, and S100A8/A9 in the CM from the impaired function group (P < 0.05). Pretreatment of HUVECs with inhibitors to a known S100A8 and S100A9 receptor, Toll-like receptor 4 (TLR4), but not receptor for advanced glycation end products, improved HUVEC network formation (P < 0.05) compared with CM alone in the impaired function conditions. Exposure of HUVECs to the TLR4 signaling inhibitor also blocked recombinant S100A8- and S100A9-mediated reductions in network formation. Collectively, the results suggest that the mechanisms behind impaired CAC CD34-/CD31+CM-mediated reductions in capillary-like network formation involve secretion of S100A8 and S100A9 and binding of these proteins to TLR4 receptors on HUVECs.
  S100A8 and S100A9 proteins in concentrations secreted by CD34-/CD31+circulating angiogenic cells (CACs) with impaired function reduce endothelial cell capillary-like network formation. These effects appear to be mediated by Toll-like receptor 4 and are absent with S100A8 and S100A9 in concentrations secreted by healthy CD34-/CD31+CACs.
authors: Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland.
authors: Rian Q
authors: http://orcid.org/0000-0002-3092-2538
authors: RQ
authors: Landers-Ramos
authors: Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland.
authors: Ryan M
authors: RM
authors: Sapp
authors: Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland.
authors: Emily
authors: E
authors: VandeWater
authors: Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland.
authors: Jennifer
authors: J
authors: Macko
authors: Baltimore Veterans Affairs Medical Center, Baltimore, Maryland.
authors: Shawn
authors: S
authors: Robinson
authors: Proteomics Core Facility, College of Computer, Mathematics, and Natural Sciences, University of Maryland, College Park, Maryland; and.
authors: Yan
authors: Y
authors: Wang
authors: Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland.
authors: Eva R
authors: ER
authors: Chin
authors: Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland.
authors: Espen E
authors: EE
authors: Spangenburg
authors: University of Maryland School of Medicine and Baltimore Veterans Affairs Geriatric Research, Education and Clinical Center, Baltimore, Maryland.
authors: Steven J
authors: http://orcid.org/0000-0002-4627-6489
authors: SJ
authors: Prior
authors: Department of Kinesiology, School of Public Health, University of Maryland, College Park, Maryland; hagberg@umd.edu.
authors: James M
authors: JM
authors: Hagberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018952:Antigens, CD34 / Q000378:metabolism; D015153:Blotting, Western; D040501:Calgranulin A / Q000235:genetics / Q000378:metabolism*; D040502:Calgranulin B / Q000235:genetics / Q000378:metabolism*; D002196:Capillaries / Q000378:metabolism*; D016022:Case-Control Studies; D002478:Cells, Cultured; D066026:Endothelial Progenitor Cells / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D018189:Immunomagnetic Separation; D013058:Mass Spectrometry; D008875:Middle Aged; D018919:Neovascularization, Physiologic / Q000235:genetics*; D000072658:Non-ST Elevated Myocardial Infarction / Q000378:metabolism*; D019899:Paracrine Communication; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D055815:Young Adult
chemical_list: D018952:Antigens, CD34; D040501:Calgranulin A; D040502:Calgranulin B; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4
keywords: angiogenesis; circulating angiogenic cells; endothelial cells; myocardial infarction; paracrine function