Today's journal article
Rahman MT, Mostaert BJ, Eckard P, Fatima SM, Scheperle R, Razu I, Hunger B, Olszewski RT, Gu S, Garcia CL, Khan NA, Bennion DM, Oleson J, Kirk JR, Enke YL, Gay RD, Morell RJ, Hirose K, Hoa M, Claussen AD, Hansen MR.
- Dexamethasone-eluting cochlear implants reduce inflammation and foreign body response in human and murine cochleae.
- Sci Rep. 2025 Aug 20;15(1):30615. doi: 10.1038/s41598-025-10739-y.
- PMID: 40836064; PMCID: PMC12368128.
- Available online at: https://www.nature.com/articles/s41598-025-10739-y
Why I picked this article
One of the ongoing challenges in cochlear implant surgery is the foreign body response that follows electrode insertion. When the body detects the implant as a foreign object, it can trigger inflammation and scarring inside the cochlea. This can increase electrode impedance, meaning the device needs more electrical power to deliver sound signals effectively, potentially affecting patient outcomes. It is thought that the foreign body response is mediated by macrophages and inflammatory proteins.
Conversely, if we can suppress the inflammation following the cochlear implant surgery, it could improve the long-term performance of the cochlear implant. This has led to the use of steroids to suppress the immune response pre- and post-surgery, which has been effective. To take it further, cochlear implant companies have been working on a different approach: "drug-eluting cochlear implants" that come with steroids embedded and are released directly to the cochlear region adjacent to the cochlear implant.
This study explores whether drug-eluting cochlear implants with dexamethasone, a corticosteroid with strong anti-inflammatory properties (a dexamethasone-eluting CI, or Dex-CI), can reduce this response in the long term.
Some of the research findings
Animal model:
- Dual reporter mice (CX3CR1+/GFP Thy1+/YFP) were used — these allow visualization of both macrophages (immune cells) and neurons.
Mice received one of the following in their left ear:
- Dex-CI (implant with dexamethasone embedded),
- Standard-CI (no drug), or
- Dex-local (standard implant + dexamethasone injection into the middle ear, simulating current clinical practice).
- The right ear remained unoperated as a control.
Human data:
- Electrical impedance was measured over time (as a reflection of inflammation and tissue resistance).
- The inflammatory response was assessed through imaging and histology.
- Parallel impedance measurements were taken in human patients implanted with either Dex-CI or standard CIs.
Finding:
- Dex-CI implants significantly reduced inflammation and electrode impedance over time in mice.
- The reduction was sustained long-term, indicating that continuous local steroid release helps prevent chronic inflammatory encapsulation of the electrode.
- Dex-local (injected steroid) showed only short-term benefits, with impedance and inflammation returning to higher levels over time.
- In the human participants, the same trend was observed: those implanted with Dex-CI had lower electrode impedances compared to standard devices.
Haruna's takeaway
This is very important data, and it is very exciting to see some early results from the clinical trial that has been included. The parallel combination of mouse-based study and human data allows the mechanism of action or effect on macrophage can be analysed in the mouse model. Quite important so I intend to re-visit this publication for more detail to be covered in this journal club again.
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This is Haruna's 46/100 of the 100-day challenge to post a science blog article every day! I love inner ear biology & cochlear physiology.