title: High-Magnitude and/or High-Frequency Mechanical Strain Promotes Peripapillary Scleral Myofibroblast Differentiation.
abstract: OBJECTIVE
  To determine the effects of altered mechanical strain on human peripapillary scleral (ppSc) fibroblast-to-myofibroblast differentiation.
  
  
  METHODS
  Eight human ppSc fibroblast cultures were isolated from three paired eyes and two unilateral eyes of five donors using an explant approach. Human ppSc fibroblast isolates were subjected to 1% and 4% cyclic strain at 0.05 to 5 Hz for 24 hours. Levels of α smooth muscle actin (αSMA) mRNA and protein were determined by real-time PCR and immunoblot. Incorporation of αSMA into actin stress fibers was evaluated by confocal immunofluorescent microscopy. Myofibroblast contractility was measured by fibroblast-populated three-dimensional collagen gel contraction assay and phosphorylation of myosin light chain (MLC20).
  
  
  RESULTS
  Human ppSc fibroblasts contained 6% to 47% fully differentiated myofibroblasts before strain application; 4% cyclic strain increased αSMA mRNA and protein expression in ppSc fibroblasts compared with 1% strain applied at 5 Hz, but not at lower frequencies. Seven of eight ppSc fibroblast isolates responded to high-magnitude and high-frequency strain with increased cellular contractility and increased MLC20 phosphorylation. In addition, increasing strain frequency promoted αSMA expression in ppSc fibroblasts under both 1% and 4% strain conditions.
  
  
  CONCLUSIONS
  High-magnitude and/or high-frequency mechanical strain promotes differentiation of human ppSc fibroblasts into contractile myofibroblasts, a fibroblast phenotypic change known to be key to tissue injury-repair responses. These findings suggest that the cellular constituent of ppSc may play an important role in the regulation of optic nerve head biomechanics in response to injurious IOP fluctuations.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Jing
authors.initials: J
authors.lastname: Qu
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Huaping
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States 2The Second Xiangya Hospital, Central-South University, Changsha, Hunan, China.
authors.forename: Lanyan
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Namasivayam
authors.initials: N
authors.lastname: Ambalavanan
authors.affiliation: Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Girkin
authors.affiliation: Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States 5Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Joanne E
authors.initials: JE
authors.lastname: Murphy-Ullrich
authors.affiliation: Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States 6Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: J Crawford
authors.initials: JC
authors.lastname: Downs
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States 4Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States 6Department of Biomedical Engineering, University of Alab.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D015153:Blotting, Western; D002454:Cell Differentiation; D002478:Cells, Cultured; D006801:Humans; D018613:Microscopy, Confocal; D058628:Myofibroblasts / Q000166:cytology* / Q000378:metabolism; D009898:Optic Disk / Q000473:pathology*; D010641:Phenotype; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D060888:Real-Time Polymerase Chain Reaction; D012590:Sclera / Q000473:pathology*
chemical_list: D012333:RNA, Messenger