Closure of supporting cell scar formations requires dynamic actin mechanisms

Hear Res. 2007 Oct;232(1-2):1-19. doi: 10.1016/j.heares.2007.06.011. Epub 2007 Jun 27.

Abstract

In many vertebrate inner ear sensory epithelia, dying sensory hair cells are extruded, and the apices of surrounding supporting cells converge to re-seal the epithelial barrier between the electrochemically-distinct endolymph and perilymph. These cellular mechanisms remain poorly understood. Dynamic microtubular mechanisms have been proposed for hair cell extrusion; while contractile actomyosin-based mechanisms are required for cellular extrusion and closure in epithelial monolayers. The hypothesis that cytoskeletal mechanisms are required for hair cell extrusion and supporting cell scar formation was tested using bullfrog saccules incubated with gentamicin (6h), and allowed to recover (18h). Explants were then fixed, labeled for actin and cytokeratins, and viewed with confocal microscopy. To block dynamic cytoskeletal processes, disruption agents for microtubules (colchicine, paclitaxel) myosin (Y-27632, ML-9) or actin (cytochalasin D, latrunculin A) were added during treatment and recovery. Microtubule disruption agents had no effect on hair cell extrusion or supporting cell scar formation. Myosin disruption agents appeared to slow down scar formation but not hair cell extrusion. Actin disruption agents blocked scar formation, and largely prevented hair cell extrusion. These data suggest that actin-based cytoskeletal processes are required for hair cell extrusion and supporting cell scar formation in bullfrog saccules.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Amides / pharmacology
  • Animals
  • Anti-Bacterial Agents / toxicity
  • Azepines / pharmacology
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology
  • Cell Death
  • Cicatrix / metabolism*
  • Cicatrix / pathology
  • Cicatrix / physiopathology
  • Colchicine / pharmacology
  • Cytochalasin D / pharmacology
  • Gentamicins / toxicity
  • Hair Cells, Auditory / drug effects*
  • Hair Cells, Auditory / metabolism
  • Hair Cells, Auditory / ultrastructure
  • Immunohistochemistry
  • Keratins / metabolism
  • Microscopy, Confocal
  • Microscopy, Electron, Transmission
  • Microtubules / drug effects
  • Microtubules / metabolism
  • Myosins / metabolism
  • Paclitaxel / pharmacology
  • Pyridines / pharmacology
  • Rana catesbeiana
  • Saccule and Utricle / drug effects*
  • Saccule and Utricle / metabolism
  • Saccule and Utricle / physiopathology
  • Saccule and Utricle / ultrastructure
  • Thiazolidines / pharmacology
  • Time Factors
  • Tissue Culture Techniques
  • Tubulin Modulators / pharmacology*
  • Wound Healing / drug effects*

Substances

  • Actins
  • Amides
  • Anti-Bacterial Agents
  • Azepines
  • Bridged Bicyclo Compounds, Heterocyclic
  • Gentamicins
  • Pyridines
  • Thiazolidines
  • Tubulin Modulators
  • ML 9
  • Y 27632
  • Cytochalasin D
  • Keratins
  • Myosins
  • Paclitaxel
  • Colchicine
  • latrunculin A