title: Collective cell migration of smooth muscle and endothelial cells: impact of injury versus non-injury stimuli.
abstract: BACKGROUND
  Cell migration is a vital process for growth and repair. In vitro migration assays, utilized to study cell migration, often rely on physical scraping of a cell monolayer to induce cell migration. The physical act of scrape injury results in numerous factors stimulating cell migration - some injury-related, some solely due to gap creation and loss of contact inhibition. Eliminating the effects of cell injury would be useful to examine the relative contribution of injury versus other mechanisms to cell migration. Cell exclusion assays can tease out the effects of injury and have become a new avenue for migration studies. Here, we developed two simple non-injury techniques for cell exclusion: 1) a Pyrex® cylinder - for outward migration of cells and 2) a polydimethylsiloxane (PDMS) insert - for inward migration of cells. Utilizing these assays smooth muscle cells (SMCs) and human umbilical vein endothelial cells (HUVECs) migratory behavior was studied on both polystyrene and gelatin-coated surfaces.
  
  
  RESULTS
  Differences in migratory behavior could be detected for both smooth muscle cells (SMCs) and endothelial cells (ECs) when utilizing injury versus non-injury assays. SMCs migrated faster than HUVECs when stimulated by injury in the scrape wound assay, with rates of 1.26 % per hour and 1.59 % per hour on polystyrene and gelatin surfaces, respectively. The fastest overall migration took place with HUVECs on a gelatin-coated surface, with the in-growth assay, at a rate of 2.05 % per hour. The slowest migration occurred with the same conditions but on a polystyrene surface at a rate of 0.33 % per hour.
  
  
  CONCLUSIONS
  For SMCs, injury is a dominating factor in migration when compared to the two cell exclusion assays, regardless of the surface tested: polystyrene or gelatin. In contrast, the migrating surface, namely gelatin, was a dominating factor for HUVEC migration, providing an increase in cell migration over the polystyrene surface. Overall, the cell exclusion assays - the in-growth and out-growth assays, provide a means to determine pure migratory behavior of cells in comparison to migration confounded by cell wounding and injury.
authors.affiliation: Biomedical Engineering GIDP, University of Arizona, Tucson, AZ USA.
authors.forename: Kaitlyn R
authors.initials: KR
authors.lastname: Ammann
authors.affiliation: Biomedical Engineering GIDP, University of Arizona, Tucson, AZ USA.
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: DeCook
authors.affiliation: Sarver Heart Center, College of Medicine, University of Arizona, 1501 N Campbell Ave, Tucson, AZ 85724 USA.
authors.forename: Phat L
authors.initials: PL
authors.lastname: Tran
authors.affiliation: Biomedical Engineering GIDP, University of Arizona, Tucson, AZ USA.
authors.forename: Valerie M
authors.initials: VM
authors.lastname: Merkle
authors.affiliation: Biomedical Engineering GIDP, University of Arizona, Tucson, AZ USA ; Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ USA.
authors.forename: Pak K
authors.initials: PK
authors.lastname: Wong
authors.affiliation: Biomedical Engineering GIDP, University of Arizona, Tucson, AZ USA ; Sarver Heart Center, College of Medicine, University of Arizona, 1501 N Campbell Ave, Tucson, AZ 85724 USA ; Department of Biomedical Engineering, University of Arizona, Tucson, AZ USA.
authors.forename: Marvin J
authors.initials: MJ
authors.lastname: Slepian
keywords: Collective cell migration; Endothelial cell; Gelatin; Injury; Polystyrene; Scrape wound; Smooth muscle cell; Vascular