title: TNF-α increases endothelial progenitor cell adhesion to the endothelium by increasing bond expression and affinity.
abstract: Endothelial progenitor cells (EPCs) are a rare population of cells that participate in angiogenesis. To effectively use EPCs for regenerative therapy, the mechanisms by which they participate in tissue repair must be elucidated. This study focused on the process by which activated EPCs bind to a target tissue. It has been demonstrated that EPCs can bind to endothelial cells (ECs) through the tumore necrosis factor-α (TNF-α)-regulated vascular cell adhesion molecule 1/very-late antigen 4 (VLA4) interaction. VLA4 can bind in a high or low affinity state, a process that is difficult to experimentally isolate from bond expression upregulation. To separate these processes, a new parallel plate flow chamber was built, a detachment assay was developed, and a mathematical model was created that was designed to analyze the detachment assay results. The mathematical model was developed to predict the relative expression of EPC/EC bonds made for a given bond affinity distribution. EPCs treated with TNF-α/vehicle were allowed to bind to TNF-α/vehicle-treated ECs in vitro. Bound cells were subjected to laminar flow, and the cellular adherence was quantified as a function of shear stress. Experimental data were fit to the mathematical model using changes in bond expression or affinity as the only free parameter. It was found that TNF-α treatment of ECs increased adhesion through bond upregulation, whereas TNF-α treatment of EPCs increased adhesion by increasing bond affinity. These data suggest that injured tissue could potentially increase recruitment of EPCs for tissue regeneration via the secretion of TNF-α.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin;
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Prisco
authors.affiliation: Exponent Engineering and Scientific Consulting, Biomedical Engineering Practice, Warrenville, Illinois; and.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Prisco
authors.affiliation: Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Carlson
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin; agreene@mcw.edu.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Greene
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002478:Cells, Cultured; D066026:Endothelial Progenitor Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D044085:Microfluidics / Q000295:instrumentation / Q000379:methods; D008955:Models, Cardiovascular; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1
keywords: affinity modeling; cellular detachment; mathematical model of cellular adhesion; microfluidics; monte carlo model; parallel plate flow chamber