Regenerative Medicine to Restore Human Hearing? Hope for the Future.

Note: Beware of scams. While this research looks promising and is advancing quickly, there are currently no FDA-approved cochlear hair cell regenerative therapies available.

Regenerative Medicine is an extremely complicated yet dynamic field of research. By using the body’s own healing capacity, the goal is to regenerate (replace or repair) damaged human cells and tissues. Scientists are actively working on Regenerative Medicine interventions that could help restore hearing in humans. But what options are available to do just that?

Coaxing a shut-down repair system back into action?

Sensori-neural hearing loss is the result of injuries to the human inner ear hearing (hair) cells and to the hearing nerve. In mammals, which includes humans, the damage is permanent, no matter what the cause(s) might be. However, in non-mammals, such as birds, neighboring “supporting” cells jump into action. They start the spontaneous process of repairing or replacing damaged and dead inner ear hair cells, which reconnect to the hearing nerve. Ultimately, normal hearing is restored.

Unfortunately, human cochlear (inner ear) supporting cells lose their capability of acting as fix & replace crews. The system shuts down around birth. But why? Can these disabled human supporting cells be reactivated? How? Are human-specific genetics involved? Those are some of the fundamental questions that keep challenging researchers.

To “wake up” the dormant cochlear supporting cells, scientists have developed some highly complicated chemical compounds, often referred to as hearing regeneration drugs. When injected into the ears, these designer-style drugs target chemical pathways and genes and systems that are known to be involved in the shut-down of human supporting cells’ repair capabilities. The science behind it all boggles the mind. While  human trials have shown promise, overall results were disappointing. Further progress must be made to produce consistent outcomes.

Regenerative stem cell therapy

Stem Cell research to restore human hearing has been in the spotlight for some time. Turning stem cells into new inner ear hearing and nerve cells could offer a reasonable chance for a cure of permanent human hearing loss. But what are stem cells?

Stem cells are often called body “master cells” waiting to be assigned a task. When given cues with specific genetic, chemical and physical instructions, they can self-renew or duplicate themselves. Or they can differentiate and change into any kind of body cell, such as skin, blood, liver, kidney etc. The goal is to convince them to become new inner-ear hair cells and hearing nerve cells. Yet, there are still serious obstacles to overcome.

Adult Body Cell Rewind?  Or Back to the Future?

Stem cells can be obtained from outside donors, such as cord blood, which brings with it the risk of rejection by the body. So, how about using the patient’s own body cells and rewinding them, so-to-speak. This would minimize or eliminate the risk of rejection. Can that be done? Isn’t it true that stem cell specialization is permanent and irreversible? Once an adult skin cell, always an adult skin cell? However, this was found not to be true, a discovery that opens a whole new field of stem cell research and hope.

In 2012, the Nobel Prize in Physiology or Medicine  went to two scientists who proved that adult body cells can be genetically “reprogrammed” into becoming again “generic” stem cells, ready for a new assignment. Given the correct codes and cues, they can differentiate all over. Might such reprogrammed body cells be instructed to become hearing cells and nerve cells? Technically, yes but there are other practical issues.

The reprogramming process itself is still very complicated with its own safety issues. One of the challenges is to avoid run-away cell division. Also, reprogramming and growing the cells happens in the lab. The next task is to find safe and effective ways for transplanting the newly grown cells into the ears. But will they work? Will they indeed restore lost hearing? Will they function the way their dead or dying forebears did?

Although progress is being made, any regenerative techniques must be safe and produce consistent outcomes. Then, after successful trials, the FDA must approve the therapies. Meanwhile people already wonder how much will this cost, if the ear hair cell “restoration” is permanent and if insurance will cover it? We don’t know that yet. Only the future will tell.

Save the hearing we have

While Regenerative Medicine to restore human hearing offers hope for the future, this is neither a quick nor an easy fix. Given time, regenerative research advances could offer a reasonable chance for a cure of human hearing loss. Meanwhile, the best we can do for ourselves is to get into damage-control mode and preserve the hearing that we have right now. .