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Absence of strial melanin coincides with age-associated marginal cell loss and endocochlear potential decline.
Hear Res. 2009 Mar; 249(1-2):1-14.HR

Abstract

Cochlear stria vascularis contains melanin-producing intermediate cells that play a critical role in the production of the endocochlear potential (EP) and in maintaining the high levels of K(+) that normally exist in scala media. The melanin produced by intermediate cells can be exported to the intrastrial space, where it may be taken up by strial marginal cells and basal cells. Because melanin can act as an antioxidant and metal chelator, evidence for its role in protecting the stria and organ of Corti against noise, ototoxins, and aging has long been sought. While some evidence supports a protective role of melanin against noise and ototoxins, no evidence yet presented has demonstrated a clear role for melanin in maintaining the EP during aging. We tested this by comparing basal turn EPs and a host of cochlear cellular metrics in aging C57BL/6 (B6) mice and C57BL/6-Tyr(c-2J) mice. The latter mice carry a naturally occurring inactivating mutation of the tyrosinase locus, and produce no strial melanin. Because these two strains are coisogenic, and because pigmented B6 mice show essentially no age-related EP decline, they provide an ideal test of importance of melanin in the aging stria. Pigmented and albino B6 mice showed identical rates of hearing loss and sensory cell loss. However, after two years of age, basal turn EPs significantly diverged, with 42% of albinos showing EPs below 100 mV versus only 18% of pigmented mice. The clearest anatomical correlate of this EP difference was significantly reduced strial thickness in the albinos that was highly correlated with loss of marginal cells. Combined with findings in human temporal bones, plus recent work in BALB/c mice and gerbils, the present findings point to a common etiology in strial presbycusis whereby EP reduction is principally linked to marginal cell loss or dysfunction. For any individual, genetic background, environmental influences, and stochastic events may work together to determine whether marginal cell density or function falls below some critical level, and thus whether EP decline occurs.

Authors+Show Affiliations

Fay and Carl Simons Center for the Biology of Hearing and Deafness/Central Institute for the Deaf at Washington University, St. Louis, MO, USA. kohlemiller@wustl.eduNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

19141317

Citation

Ohlemiller, Kevin K., et al. "Absence of Strial Melanin Coincides With Age-associated Marginal Cell Loss and Endocochlear Potential Decline." Hearing Research, vol. 249, no. 1-2, 2009, pp. 1-14.
Ohlemiller KK, Rice ME, Lett JM, et al. Absence of strial melanin coincides with age-associated marginal cell loss and endocochlear potential decline. Hear Res. 2009;249(1-2):1-14.
Ohlemiller, K. K., Rice, M. E., Lett, J. M., & Gagnon, P. M. (2009). Absence of strial melanin coincides with age-associated marginal cell loss and endocochlear potential decline. Hearing Research, 249(1-2), 1-14. https://doi.org/10.1016/j.heares.2008.12.005
Ohlemiller KK, et al. Absence of Strial Melanin Coincides With Age-associated Marginal Cell Loss and Endocochlear Potential Decline. Hear Res. 2009;249(1-2):1-14. PubMed PMID: 19141317.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Absence of strial melanin coincides with age-associated marginal cell loss and endocochlear potential decline. AU - Ohlemiller,Kevin K, AU - Rice,Mary E Rybak, AU - Lett,Jaclynn M, AU - Gagnon,Patricia M, Y1 - 2008/12/25/ PY - 2008/10/29/received PY - 2008/12/15/revised PY - 2008/12/16/accepted PY - 2009/1/15/entrez PY - 2009/1/15/pubmed PY - 2009/6/16/medline SP - 1 EP - 14 JF - Hearing research JO - Hear Res VL - 249 IS - 1-2 N2 - Cochlear stria vascularis contains melanin-producing intermediate cells that play a critical role in the production of the endocochlear potential (EP) and in maintaining the high levels of K(+) that normally exist in scala media. The melanin produced by intermediate cells can be exported to the intrastrial space, where it may be taken up by strial marginal cells and basal cells. Because melanin can act as an antioxidant and metal chelator, evidence for its role in protecting the stria and organ of Corti against noise, ototoxins, and aging has long been sought. While some evidence supports a protective role of melanin against noise and ototoxins, no evidence yet presented has demonstrated a clear role for melanin in maintaining the EP during aging. We tested this by comparing basal turn EPs and a host of cochlear cellular metrics in aging C57BL/6 (B6) mice and C57BL/6-Tyr(c-2J) mice. The latter mice carry a naturally occurring inactivating mutation of the tyrosinase locus, and produce no strial melanin. Because these two strains are coisogenic, and because pigmented B6 mice show essentially no age-related EP decline, they provide an ideal test of importance of melanin in the aging stria. Pigmented and albino B6 mice showed identical rates of hearing loss and sensory cell loss. However, after two years of age, basal turn EPs significantly diverged, with 42% of albinos showing EPs below 100 mV versus only 18% of pigmented mice. The clearest anatomical correlate of this EP difference was significantly reduced strial thickness in the albinos that was highly correlated with loss of marginal cells. Combined with findings in human temporal bones, plus recent work in BALB/c mice and gerbils, the present findings point to a common etiology in strial presbycusis whereby EP reduction is principally linked to marginal cell loss or dysfunction. For any individual, genetic background, environmental influences, and stochastic events may work together to determine whether marginal cell density or function falls below some critical level, and thus whether EP decline occurs. SN - 1878-5891 UR - https://www.unboundmedicine.com/medline/citation/19141317/Absence_of_strial_melanin_coincides_with_age_associated_marginal_cell_loss_and_endocochlear_potential_decline_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0378-5955(08)00284-0 DB - PRIME DP - Unbound Medicine ER -