Effects of Particulate Matter Exposure on the Eustachian Tube and Middle Ear Mucosa of Rats

Hyun Min Lee; Youn-Suk Son; Hyang-Sook Kim; Joo-Young Kim; Seok-Hyun Kim; Jung Hee Lee; Sung-Won Choi; Se-Joon Oh; Soo-Keun Kong; Moo Jin Baek; Il-Woo Lee

doi:10.21053/ceo.2023.00227

Effects of Particulate Matter Exposure on the Eustachian Tube and Middle Ear Mucosa of Rats

Clin Exp Otorhinolaryngol. 2023 Aug;16(3):225-235. doi: 10.21053/ceo.2023.00227. Epub 2023 May 18.

Authors

Hyun Min Lee^{1

2}, Youn-Suk Son³, Hyang-Sook Kim², Joo-Young Kim², Seok-Hyun Kim^{1

2}, Jung Hee Lee⁴, Sung-Won Choi⁵, Se-Joon Oh⁵, Soo-Keun Kong⁵, Moo Jin Baek⁶, Il-Woo Lee^{1

2}

Affiliations

¹ Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University College of Medicine, Pusan National University Yangsan Hospital, Yangsan, Korea.
² The Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, Korea.
³ Department of Environmental Engineering, Pukyong National University, Busan, Korea.
⁴ Department of Pathology, Pusan National University Yangsan Hospital, Yangsan, Korea.
⁵ Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University College of Medicine, Pusan National University Hospital, Busan, Korea.
⁶ Department of Otorhinolaryngology, Inje University College of Medicine, Haeundae Paik Hospital, Busan, Korea.

Abstract

Objectives: Particulate matter (PM) is a risk factor for various diseases. Recent studies have established an association between otitis media (OM) and PM exposure. To confirm this relationship, we developed a novel exposure model designed to control the concentration of PM, and we observed the effects of PM exposure on the Eustachian tube (ET) and middle ear mucosa of rats.

Methods: Forty healthy, 10-week-old, male Sprague-Dawley rats were divided into 3-day, 7-day, 14-day exposure, and control groups (each, n=10). The rats were exposed to incense smoke as the PM source for 3 hours per day. After exposure, bilateral ETs and mastoid bullae were harvested, and histopathological findings were compared using microscopy and transmission electron microscopy (TEM). The expression levels of interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and vascular endothelial growth factor (VEGF) in the middle ear mucosa of each group were compared using real-time reverse transcription polymerase chain reaction (RT-PCR).

Results: In the ET mucosa of the exposure group, the goblet cell count significantly increased after PM exposure (P=0.032). In the middle ear mucosa, subepithelial space thickening, increased angio-capillary tissue, and inflammatory cell infiltration were observed. Moreover, the thickness of the middle ear mucosa in the exposure groups increased compared to the control group (P<0.01). The TEM findings showed PM particles on the surface of the ET and middle ear mucosa, and RT-PCR revealed that messenger RNA (mRNA) expression of IL-1β significantly increased in the 3-day and 7-day exposure groups compared to the control group (P=0.035). VEGF expression significantly increased in the 7-day exposure group compared to the control and 3-day exposure groups (P<0.01).

Conclusion: The ET and middle ear mucosa of rats showed histopathologic changes after acute exposure to PM that directly reached the ET and middle ear mucosa. Therefore, acute exposure to PM may play a role in the development of OM.

Keywords: Eustachian Tube; Incense; Middle Ear; Otitis Media; Particulate Matter; Rats.