Biophysical mechanisms underlying outer hair cell loss associated with a shortened tectorial membrane

Christopher C. Liu, Simon S. Gao, Tao Yuan, Charles Steele, Sunil Puria, John S. Oghalai

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The tectorial membrane (TM) connects to the stereociliary bundles of outer hair cells (OHCs). Humans with an autosomal dominant C1509G mutation in alpha-tectorin, a protein constituent of the TM, are born with a partial hearing loss that worsens over time. The Tecta C1509/+ transgenic mouse with the same point mutation has partial hearing loss secondary to a shortened TM that only contacts the first row of OHCs. As well, Tecta C1509G/+ mice have increased expression of the OHC electromotility protein, prestin. We sought to determine whether these changes impact OHC survival. Distortion product otoacoustic emission thresholds in a quiet environment did not change to 6 months of age. However, noise exposure produced acute threshold shifts that fully recovered in Tecta +/+ mice but only partially recovered in Tecta C1509G/+ mice. While Tecta +/+ mice lost OHCs primarily at the base and within all three rows, Tecta C1509G/+ mice lost most of their OHCs in a more apical region of the cochlea and nearly completely within the first row. In order to estimate the impact of a shorter TM on the forces faced by the stereocilia within the first OHC row, both the wild type and the heterozygous conditions were simulated in a computational model. These analyses predicted that the shear force on the stereocilia is ∼50% higher in the heterozygous condition. We then measured electrically induced movements of the reticular lamina in situ and found that while they decreased to the noise floor in prestin null mice, they were increased by 4.58 dB in Tecta C1509G/+ mice compared to Tecta +/+ mice. The increased movements were associated with a fourfold increase in OHC death as measured by vital dye staining. Together, these findings indicate that uncoupling the TM from some OHCs leads to partial hearing loss and places the remaining coupled OHCs at higher risk. Both the mechanics of the malformed TM and the increased prestin-related movements of the organ of Corti contribute to this higher risk profile.

Original languageEnglish (US)
Pages (from-to)577-594
Number of pages18
JournalJARO - Journal of the Association for Research in Otolaryngology
Volume12
Issue number5
DOIs
StatePublished - Oct 1 2011

Fingerprint

Outer Auditory Hair Cells
Tectorial Membrane
Alopecia
Hearing Loss
Stereocilia
Organ of Corti
Cochlea
Mechanics

Keywords

  • cochlea
  • deafness
  • electromotility
  • hair cell
  • hearing
  • hearing loss
  • transduction

ASJC Scopus subject areas

  • Otorhinolaryngology
  • Sensory Systems

Cite this

Biophysical mechanisms underlying outer hair cell loss associated with a shortened tectorial membrane. / Liu, Christopher C.; Gao, Simon S.; Yuan, Tao; Steele, Charles; Puria, Sunil; Oghalai, John S.

In: JARO - Journal of the Association for Research in Otolaryngology, Vol. 12, No. 5, 01.10.2011, p. 577-594.

Research output: Contribution to journalArticle

Liu, Christopher C. ; Gao, Simon S. ; Yuan, Tao ; Steele, Charles ; Puria, Sunil ; Oghalai, John S. / Biophysical mechanisms underlying outer hair cell loss associated with a shortened tectorial membrane. In: JARO - Journal of the Association for Research in Otolaryngology. 2011 ; Vol. 12, No. 5. pp. 577-594.
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abstract = "The tectorial membrane (TM) connects to the stereociliary bundles of outer hair cells (OHCs). Humans with an autosomal dominant C1509G mutation in alpha-tectorin, a protein constituent of the TM, are born with a partial hearing loss that worsens over time. The Tecta C1509/+ transgenic mouse with the same point mutation has partial hearing loss secondary to a shortened TM that only contacts the first row of OHCs. As well, Tecta C1509G/+ mice have increased expression of the OHC electromotility protein, prestin. We sought to determine whether these changes impact OHC survival. Distortion product otoacoustic emission thresholds in a quiet environment did not change to 6 months of age. However, noise exposure produced acute threshold shifts that fully recovered in Tecta +/+ mice but only partially recovered in Tecta C1509G/+ mice. While Tecta +/+ mice lost OHCs primarily at the base and within all three rows, Tecta C1509G/+ mice lost most of their OHCs in a more apical region of the cochlea and nearly completely within the first row. In order to estimate the impact of a shorter TM on the forces faced by the stereocilia within the first OHC row, both the wild type and the heterozygous conditions were simulated in a computational model. These analyses predicted that the shear force on the stereocilia is ∼50{\%} higher in the heterozygous condition. We then measured electrically induced movements of the reticular lamina in situ and found that while they decreased to the noise floor in prestin null mice, they were increased by 4.58 dB in Tecta C1509G/+ mice compared to Tecta +/+ mice. The increased movements were associated with a fourfold increase in OHC death as measured by vital dye staining. Together, these findings indicate that uncoupling the TM from some OHCs leads to partial hearing loss and places the remaining coupled OHCs at higher risk. Both the mechanics of the malformed TM and the increased prestin-related movements of the organ of Corti contribute to this higher risk profile.",
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