Single Fraction and Hypofractionated Radiation Cause Cochlear Damage, Hearing Loss, and Reduced Viability of Merlin-Deficient Schwann Cells

Christine T. Dinh, Si Chen, Aida Nourbakhsh, Kyle Padgett, Perry Johnson, Stefania Goncalves, Olena Bracho, Esperanza Bas, Jorge Bohorquez, Paula V. Monje, Cristina Fernandez-Valle, Nagy Elsayyad, Xuezhong Liu, Scott M. Welford, Fred Telischi

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Vestibular schwannomas (VS) are benign intracranial tumors caused by loss of function of the merlin tumor suppressor. We tested three hypotheses related to radiation, hearing loss (HL), and VS cell survival: (1) radiation causes HL by injuring auditory hair cells (AHC), (2) fractionation reduces radiation-induced HL, and (3) single fraction and equivalent appropriately dosed multi-fractions are equally effective at controlling VS growth. We investigated the effects of single fraction and hypofractionated radiation on hearing thresholds in rats, cell death pathways in rat cochleae, and viability of human merlin-deficient Schwann cells (MD-SC). Methods: Adult rats received cochlear irradiation with single fraction (0 to 18 Gray [Gy]) or hypofractionated radiation. Auditory brainstem response (ABR) testing was performed for 24 weeks. AHC viabilities were determined using immunohistochemistry. Neonatal rat cochleae were harvested after irradiation, and gene- and cell-based assays were conducted. MD-SCs were irradiated, and viability assays and immunofluorescence for DNA damage and cell cycle markers were performed. Results: Radiation caused dose-dependent and progressive HL in rats and AHC losses by promoting expression of apoptosis-associated genes and proteins. When compared to 12 Gy single fraction, hypofractionation caused smaller ABR threshold and pure tone average shifts and was more effective at reducing MD-SC viability. Conclusions: Investigations into the mechanisms of radiation ototoxicity and VS radiobiology will help determine optimal radiation regimens and identify potential therapies to mitigate radiation-induced HL and improve VS tumor control.

Original languageEnglish
Article number2818
JournalCancers
Volume15
Issue number10
DOIs
StatePublished - May 2023

Bibliographical note

Publisher Copyright:
© 2023 by the authors.

Keywords

  • Schwann
  • apoptosis
  • auditory hair cell
  • cell death
  • hearing
  • hearing loss
  • hypofractionation
  • radiation
  • vestibular schwannoma

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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