title: Substrate Stiffness Affects Human Keratinocyte Colony Formation.
abstract: Restoration of epidermal organization and function in response to a variety of pathophysiological insults is critically dependent on coordinated keratinocyte migration, proliferation, and stratification during the process of wound healing. These processes are mediated by the reconfiguration of both cell-cell (desmosomes, adherens junctions) and cell-matrix (focal adhesions, hemidesmosomes) junctions and the cytoskeletal filament networks that they serve to interconnect. In this study, we investigated the role of substrate elasticity (stiffness) on keratinocyte colony formationin vitroduring the process of nascent epithelial sheet formation as triggered by thecalcium switchmodel of keratinocyte culture. Keratinocytes cultured on pepsin digested type I collagen coatedsoft(nominalE= 1.2 kPa) polyacrylamide gels embedded with fluorescent microspheres exhibited (i) smaller spread contact areas, (ii) increased migration velocities, and (iii) increased rates of colony formation with more cells per colony than did keratinocytes cultured onstiff(nominalE= 24 kPa) polyacrylamide gels. As assessed by tracking of embedded microsphere displacements, keratinocytes cultured onsoftsubstrates generated large local substrate deformations that appeared to recruit adjacent keratinocytes into joining an evolving colony. Together with the observed differences in keratinocyte kinematics and substrate deformations, we developed twoad hocanalyses, termed distance rank (DR) and radius of cooperativity (RC), that help to objectively ascribe what we perceive as increasinglycooperativebehavior of keratinocytes cultured onsoftversusstiff gelsduring the process of colony formation. We hypothesize that the differences in keratinocyte colony formation observed in our experiments could be due to cell-cell mechanical signaling generated via local substrate deformations that appear to be correlated with the increased expression of β4 integrin within keratinocytes positioned along the periphery of an evolving cell colony.
authors.affiliation: Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA.
authors.forename: Hoda
authors.initials: H
authors.lastname: Zarkoob
authors.affiliation: Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Bodduluri
authors.affiliation: Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA.
authors.forename: Sailahari V
authors.initials: SV
authors.lastname: Ponnaluri
authors.affiliation: Department of Dermatology, University of Iowa, Iowa City, IA, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Selby
authors.affiliation: Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Sander