Huang TQ, Lee MS, Oh EH, Kalinec F, Zhang BT, Seo JS, Park WY. (2008). Characterization of biological effect of 1763 MHz radiofrequency exposure on auditory hair cells. Int J Radiat Biol 84(11): 909-915.
Hair cells in the inner ear are sensory neurons for auditory and vestibular functions. Damage to the auditory hair cells can result in hearing and vestibular impairment. Because auditory cells can be exposed to mobile phone radiofrequency (RF) fields, it is important to know whether any biological alteration in the auditory hair cells can occur after such exposure.
The objective of the study was to characterize cellular response to 1763 MHz RF exposure in HEI-OC1 immortalized mouse auditory hair cells. These cells express several molecular markers that are characteristics of the organ of Corti sensory cells.
Cells were exposed to 1763 MHz RF at a specific absorption rate (SAR) of 20 W/kg in a code division multiple access (CDMA) exposure chamber for 24 and 48 hours. Changes in cell cycle, DNA damage, stress response, and gene expression were all assessed. Cells exposed to RF were compared to sham-exposed cells. Sham exposures were carried out in the same kind of chamber but with no antenna.
To investigate the possible effect of RF exposure on the cell cycle, cells were separated into four phases: sub-G0/G1, G1, S, and G2/M. DNA damage was evaluated by measuring two comet assay parameters: olive tail moment and tail length. Because RF exposure can be considered as an environmental stressor, stress response was evaluated by monitoring stress biomarkers, such as heat shock proteins (HSP) and mitogen-activated protein kinases (MAPK). Microarrays were used to identify any possible alteration in gene expression.
No significant differences were observed in the overall patterns of the cell cycle phases between sham- and RF-exposed cells. Based on the two studied comet assay parameters, there was no evidence of DNA damage even after RF exposure for 48 hours. There were also no detected changes in the expression of HSP or in the phosphorylation of MAPK. Full genome expression mouse microarray found that only 29 genes (0.09% of the total number of genes examined) were changed by more than 1.5 fold after RF exposure.
According to the review by Vijayalaxmi and Obe (2004), 58% of published study on RF exposure did not provide any indication of increased damage to genetic material, 23% of investigations reported an increase in such damage, and 19% of the studies were inconclusive. The high exposure conditions (SAR of 20 W/kg for up to 48 hours) in the present study could not induce any measurable DNA damage in HEI-OC1 auditory cells.
Concerning the altered gene expression, the authors believe that, because the number of altered genes is so small and because there was no consistent group of functional gene categories, these may be false positive findings.
Based on the results of this study, there was no evidence of induction of cellular responses, including alterations in cell cycle distribution, gene expression, stress response and DNA damage after 1763 MHz RF exposure even at SAR as high as 20 W/kg in HEI-OC1 auditory hair cells.