title: Elucidating the mechanism of wound contraction: rapid versus sustained myosin ATPase activity in attached-delayed-released compared with free-floating fibroblast-populated collagen lattices.
abstract: Wound contraction closes open wounds by the generation of contractile forces within granulation tissue. We investigated the mechanism of wound contraction using the in vitro fibroblast-populated collagen lattice (FPCL) contraction model. The contraction of the free-floating (FF)-FPCL is through rapid myosin ATPase activity, while the contraction of the attached-delayed-released (ADR)-FPCL is through sustained myosin ATPase activity. All FPCLs were cast identically and the contraction of FF-FPCLs was recorded daily for 4 days and the contraction of ADR-FPCLs was recorded 1 hour after release on day 4. At day, 4 cell numbers were determined and cells undergoing apoptosis were identified and counted. Differences in sustained and rapid myosin ATPase activity were shown by added inosine triphosphate-induced cell contraction in permeabilized fibroblast monolayer preparations. At 2 days, the FF-FPCLs were mostly contracted, while an ADR-FPCL completed contraction 1 hour after release at day 4. Contracted myofibroblasts, identified by alpha-smooth muscle actin-stained stress fibers, were identified in contracted ADR-FPCL, whereas elongated fibroblasts were identified in contracted FF-FPCLs. Vanadate inhibited both inosine triphosphate-induced cell contraction and ADR-FPCL contraction, but neither inhibited ATP-induced cell contraction or FF-FPCL contraction. Genistein inhibited FF-FPCL contraction, but not ADR-FPCL contraction. Advancing tyrosine phosphorylation in fibroblasts promotes rapid myosin ATPase activity, while advancing tyrosine dephosphorylation in myofibroblasts promotes sustained myosin ATPase. The ADR-FPCL had a reduced cell count and a greater proportion of cells had entered apoptosis compared with FF-FPCL. These experiments show that FF-FPCL contraction is through elongated fibroblasts and rapid myosin ATPase, requiring tyrosine phosphorylation. In contrast, the mechanism for ADR-FPCL contraction is through cell contraction by sustained myosin ATPase, involving tyrosine dephosphorylation.
authors.affiliation: Division of Plastic Surgery, Hershey Medical Center, Hershey, Pennsylvania 17033, USA. pehrlich@psu.edu
authors.forename: H
authors.initials: H
authors.lastname: Paul Ehrlich
authors.forename: Bonnie
authors.initials: B
authors.lastname: Sun
authors.forename: Koijan S
authors.initials: KS
authors.lastname: Kainth
authors.forename: Fatuma
authors.initials: F
authors.lastname: Kromah
mesh_terms: D017209:Apoptosis; D002448:Cell Adhesion; D002465:Cell Movement; D002478:Cells, Cultured; D003094:Collagen / Q000502:physiology*; D005109:Extracellular Matrix / Q000502:physiology*; D005347:Fibroblasts / Q000201:enzymology*; D006801:Humans; D007150:Immunohistochemistry; D009219:Myosin-Light-Chain Kinase / Q000502:physiology*; D014945:Wound Healing / Q000502:physiology*
chemical_list: D003094:Collagen; D009219:Myosin-Light-Chain Kinase