Gene Expression Changes in Chinchilla Cochlea from Noise-Induced Temporary Threshold Shift.

Acoustic overstimulation produces many anatomical, biochemical and physiological changes in the inner ear. However, the changes in gene expression that underlie these biological changes are poorly understood. Our approach to investigating this problem is to use gene microarrays to measure the changes in gene expression in the chinchilla inner ear following a 3 h or 6 h noise exposure (95 dB SPL, 707-1414 Hz). This noise exposure causes a temporary threshold shift (~40 dB) and a temporary reduction in distortion product otoacoustic emissions (DPOAE), but no permanent hearing loss or hair cell loss. Here, we present data showing (1) the suitability of mouse and human complementary DNA (cDNA) clones for detecting chinchilla cochlear gene transcripts, and (2) the change in cochlear gene transcripts in noise exposed chinchillas. Chinchilla cochlear transcript probes exhibited strong and discrete signals on both mouse and human cDNA filter arrays. Since the strongest hybridization occurred with mouse clones, mouse cDNA microarrays were used to study noise-induced changes in gene expression. Chinchilla cDNA probes were differentially labelled with Cy3 (control) or Cy5 (noise exposed) by random primed synthesis, hybridized to 8750 mouse cDNAs arrayed on microscope slides and analysed by laser fluorescent microscopy. Several classes of genes exhibited time-dependent up regulation of transcription, including those involved in protein synthesis, metabolism, cytoskeletal proteins, and calcium binding proteins. The results are discussed in relationship to previous studies showing noise-induced changes in structural proteins, calcium binding proteins, metabolic enzymes and membrane bound vesicles.