title: Fibro-vascular coupling in the control of cochlear blood flow.
abstract: BACKGROUND
  Transduction of sound in the cochlea is metabolically demanding. The lateral wall and hair cells are critically vulnerable to hypoxia, especially at high sound levels, and tight control over cochlear blood flow (CBF) is a physiological necessity. Yet despite the importance of CBF for hearing, consensus on what mechanisms are involved has not been obtained.
  
  
  RESULTS
  We report on a local control mechanism for regulating inner ear blood flow involving fibrocyte signaling. Fibrocytes in the super-strial region are spatially distributed near pre-capillaries of the spiral ligament of the albino guinea pig cochlear lateral wall, as demonstrably shown in transmission electron microscope and confocal images. Immunohistochemical techniques reveal the inter-connected fibrocytes to be positive for Na+/K+ ATPase β1 and S100. The connected fibrocytes display more Ca(2+) signaling than other cells in the cochlear lateral wall as indicated by fluorescence of a Ca(2+) sensor, fluo-4. Elevation of Ca(2+) in fibrocytes, induced by photolytic uncaging of the divalent ion chelator o-nitrophenyl EGTA, results in propagation of a Ca(2+) signal to neighboring vascular cells and vasodilation in capillaries. Of more physiological significance, fibrocyte to vascular cell coupled signaling was found to mediate the sound stimulated increase in cochlear blood flow (CBF). Cyclooxygenase-1 (COX-1) was required for capillary dilation.
  
  
  CONCLUSIONS
  The findings provide the first evidence that signaling between fibrocytes and vascular cells modulates CBF and is a key mechanism for meeting the cellular metabolic demand of increased sound activity.
authors.affiliation: Oregon Hearing Research Center, Department of Otolaryngology/Head and Neck Surgery, Oregon Health & Science University, Portland, Oregon, United States of America.
authors.forename: Min
authors.initials: M
authors.lastname: Dai
authors.forename: Xiaorui
authors.initials: X
authors.lastname: Shi
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000166:cytology* / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002196:Capillaries / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D003051:Cochlea / Q000098:blood supply* / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D051545:Cyclooxygenase 1 / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000378:metabolism; D006168:Guinea Pigs; D008297:Male; D010782:Photolysis; D012039:Regional Blood Flow; D013016:Sound; D014664:Vasodilation
chemical_list: D051545:Cyclooxygenase 1; D002118:Calcium