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Impact of Staphylococcus Epidermidis Lysates on Middle Ear Epithelial Proinflammatory and Mucogenic Response
  1. Stéphanie Val, PhD*,
  2. Humaira Mubeen, BS*,
  3. Amarel Tomney, MS*,
  4. Saisai Chen*,
  5. Diego Preciado, MD, PhD*†
  1. From the *Sheikh Zayed Center for Pediatric Surgical Innovation, Children’s National Health System; and †Division of Pediatric Otolaryngology, Children’s National Health System, Washington, DC.
  1. Received August 18, 2014, and in revised form October 11, 2014.
  2. Accepted for publication October 29, 2014.
  3. Reprints: Diego Preciado, MD, PhD, Division of Pediatric Otolaryngology/Head and Neck Surgery, Children’s National Medical Center, 111 Michigan Ave NW, Washington, DC 20010. E-mail: dpreciad{at}cnmc.org.
  4. Supported by R01DC012377 from the National Institute on Deafness and Other Communication Disorders. The microscopic analysis in this study was carried out at the Children’s Research Institute (CRI) Light Microscopy and Image Analysis Core supported by CRI and NIH grant P30HD040677.
  5. Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal’s Web site (http://www.jinvestigativemed.com).

Abstract

Background Chronic otitis media with effusion (COME) develops after sustained inflammation and is characterized by secretory middle ear epithelial metaplasia and effusion, most frequently mucoid. Staphylococcus epidermidis, typically considered a commensal organism, is very frequently recovered in chronic middle ear fluid and in middle ear biofilms. Although it has been shown to drive inflammation in sinonasal epithelium, the impact of S. epidermidis on COME is markedly understudied. The goal of this study was to examine the in vitro effects of S. epidermidis lysates on murine and human middle ear epithelial cells.

Methods Staphylococcus epidermidis lysates were generated and used to stimulate submerged and differentiated human and murine epithelial cells (MEECs) for 24 to 48 hours. Quantitative real time-polymerase chain reaction, Western blot, enzyme-linked immunosorbent assay, and immunocytochemistry techniques were performed to interrogate the mucin gene MUC5AC and MUC5B expression and protein production, chemokine response, as well as NF-κB activation. Luciferase reporter assays were performed to further evaluate nuclear factor κB (NF-κB) activation and query specific promoter responses after S. epidermidis exposure.

Results Staphylococcus epidermidis induced a time- and dose-dependent MUC5AC and MUC5B overexpression along with a parallel overexpression of Cxcl2 in mouse MEEC and IL-8 in human MEEC. Further investigations in mMEEC showed a 1.3 to 1.5 induction of the MUC5AC and MUC5B promoters. As potential mechanisms for these responses, induction of an oxidative stress marker, along with early nuclear translocation and activation of NF-κB, was found. Finally, chronic exposure induced marked epithelial thickening of cells differentiated at the air liquid interface.

Conclusions Staphylococcus epidermidis lysates activate a proinflammatory response in MEEC, including mucin gene expression and protein production. Although typically considered a nonpathogenic commensal organism in the ear, these results suggest that they may play a role in the perpetuation of an inflammatory and mucogenic response in COME.

Key Words
  • Staphylococcus epidermidis
  • otitis media
  • metaplasia
  • NF-kB
  • Cxcl2
  • MUC5B
  • MUC5AC

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