Treating hearing loss with sound. In Russian we say klin klinom: driving a wedge out with a wedge. The problem itself becomes the cure.
Every gene therapy vector needs a promoter: a switch that tells the cell when to make the protein. Standard approach is always-on. Ours: put the gene behind a switch that responds to sound. Hair cells already have this machinery. Sound bends stereocilia, calcium floods in, a signaling cascade fires. We hijack it. Sound in = gene on. Silence = gene off. The child wears the hearing aid he already has. No special frequencies. Just everyday sounds.
Does the protein vanish at night? No. Stereocilin has a half-life of ~30 days. It takes ~13 hours of hearing aid use to hit 50% of normal levels. Sleep doesn't reset anything.
This is a computational hypothesis. Each individual component is proven (NFAT promoters, MET channel biophysics, mini-STRC packaging). Nobody has combined them for inner ear gene therapy yet.
Words are cheap. We built a mathematical model to check whether this cascade actually produces enough protein. Five differential equations, every parameter from published literature, four scenarios tested. The question: does a hearing-aid-wearing child produce therapeutic levels of stereocilin through sound alone?
With a realistic hearing aid schedule (16 hours ON at 70 dB, 8 hours sleep), the model predicts 29,571 stereocilin molecules per OHC after 72 hours (target: 15,000). In silence, only 1,023 molecules accumulate (6.8%). This gives a 29-fold dynamic range between sound-activated and silent states. The 50% therapeutic threshold is reached in just 13 hours of hearing aid use. The system self-regulates: protein saturates at the available binding sites on stereocilia, preventing overexpression.
| Parameter | Value | Source |
|---|---|---|
| MET channel conductance | 150 pS | Beurg et al. 2006 |
| Channels per bundle | 134 | Fettiplace 2017 |
| Endolymphatic potential | +80 mV | Standard |
| Calcineurin Kd (Ca²⁺) | 500 nM | Stemmer & Klee 1994 |
| NFAT nuclear import t½ | ~2 min | Tomida et al. 2003 |
| Promoter fold induction | up to 62x | Wu et al. 2023 |
| Promoter leakage | Zero (3 weeks) | Wu et al. 2023 |
| Apical compartment volume | 0.05 pL | Lumpkin & Bhatt 2001 |
How fragile is the result? We varied each parameter by ±50% to find what matters most. If the model breaks when one number changes, that parameter needs the most careful experimental measurement.
Transcription and translation rates dominate (sensitivity 1.50). This means the most important experiment is characterizing the 6xNFAT promoter strength specifically in hair cells. Channel count and calcineurin affinity matter less: the system is robust to biological variation in these parameters.
The complete ODE model is available as a Python script. Dependencies: numpy, scipy. Run it yourself to reproduce these results or modify parameters.
View on GitHub: ode_model.py