How regrowing tiny hairs could restore hearing loss

Man getting fitted with hearing aids

Hearing loss is something that affect tens of millions of Americans. Usually people notice those changes as they get older but the damage can be done years before that through the use of some prescription drugs or exposure to loud noise (I knew I shouldn’t have sat in the 6th row of that Led Zeppelin concert!)

Now researchers at the University of Southern California (USC) have identified the mechanism that appears to stop cells that are crucial to hearing from regenerating.

In a news release Dr. Neil Segil says this could, in theory, help reverse some hearing loss.  “Permanent hearing loss affects more than 60 percent of the population that reaches retirement age. Our study suggests new gene engineering approaches that could be used to channel some of the same regenerative capability present in embryonic inner ear cells.”

The inner ear has two types of cells that are crucial for hearing; “hair cells” are sensory receptors and these help the brain detect sounds, and support cells that play, as the name implies, an important structural and supporting role for the hair cells.

In people, once the hair cells are damaged that’s it, you can’t repair or replace them and the resulting hearing loss is permanent. But mice, in the first few days of life, have ability to turn some of their support cells into hair cells, thus repairing any damage. So Segil and the team set out to identify how mice were able to do that and see if those lessons could be applied to people.

They identified specific proteins that played a key role in turning genes on and off, regulating if and when the support cells could turn into hair cells. They found that one molecule, H3K4mel, was particularly important in activating the correct genetic changes need to turn the support cells into hair cells. But in mice, levels of H3K4mel disappeared quickly after birth, so the team found a drug that helped preserve the molecule, meaning the support cells retained the ability to turn into hair cells.

Now, obviously because this was just done in mice there’s a lot more work that needs to be done to see if it can also work in people, but Segil says it’s certainly an encouraging and intriguing start.

“Our study raises the possibility of using therapeutic drugs, gene editing, or other strategies to make epigenetic modifications that tap into the latent regenerative capacity of inner ear cells as a way to restore hearing. Similar epigenetic modifications may also prove useful in other non-regenerating tissues, such as the retina, kidney, lung, and heart.”

The study is published in the journal Developmental Cell

CIRM has funded several projects targeting hearing loss. You can find them here.

The Most Important Gift of All

Photo courtesy American Hospital Association

There are many players who have a key role in helping make a stem cell therapy work. The scientists who develop the therapy, the medical team who deliver it and funders like CIRM who provide the money to make this all happen. But vital as they are, in some therapies there is another, even more important group; the people who donate life-saving organs and tissues for transplant and research.

Organ and tissue donation saves lives, increases knowledge of diseases, and allow for the development of novel medications to treat them. When individuals or their families authorize donation for transplant or medical research, they allow their loved ones to build a long-lasting legacy of hope that could not be accomplished in any other way.

Four of CIRM’s clinical trials involve organ donations – three kidney transplant programs (you can read about those here, here and here) and one targeting type 1 diabetes.

Dr. Nikole Neidlinger, the Chief Medical Officer with Donor Network West – the federally designated organ and tissue recovery organization for Northern California and Nevada – says it is important to recognize the critical contribution made in a time of grief and crisis by the families of deceased donors. 

“For many families who donate, a loved one has died, and they are in shock. Even so, they are willing to say yes to giving others a second chance at life and to help others to advance science. Without them, none of this would be possible. It’s the ultimate act of generosity and compassion.”

The latest CIRM-funded clinical trial involving donated tissue is with Dr. Peter Stock and his team at UCSF. They are working on a treatment for type 1 diabetes (T1D), where the body’s immune system destroys its own pancreatic beta cells. These cells are necessary to produce insulin, which regulates blood sugar levels in the body.

In the past people have tried transplanting beta cells, from donated pancreatic islets, into patients with type 1 diabetes to try and reverse the course of the disease. However, this requires islets from multiple donors and the shortage of organ and tissue donors makes this difficult to do.

Dr. Stock’s clinical trial at UCSF aims to address these limitations.  He is going to transplant both pancreatic islets and parathyroid glands, from the same donor, into T1 patients. It’s hoped this combination approach will increase beta cell survival, potentially boosting long-term insulin production and removing the need for multiple donors.  And because the transplant is placed in the patient’s forearm, it makes it easier to monitor the effectiveness and accessibility of the islet transplants. Of equal importance, the development of this site will facilitate the transplantation of stem cell derived beta cells, which are very close to clinical application.

“As a transplant surgeon, it is an absolute privilege to be able to witness the life-saving organ transplants made possible by the selfless generosity of the donor families. It is hard to imagine how families have the will to think about helping others at a time of their greatest grief. It is this willingness to help others that restores my faith in humanity”

Donor Network West plays a vital role in this process. In 2018 alone, the organization recovered 702 donor samples for research. Thanks to the generosity of the donors/donor families, the donor network has been able to provide parathyroid and pancreas tissue essential to make this clinical trial a success”

“One organ donor can save the lives of up to eight people and a tissue donor can heal more than 75 others,” says Dr. Neidlinger. “For families, the knowledge that they are transforming someone’s life, and possibly preventing another family from experiencing this same loss, can serve as a silver lining during their time of sorrow. .”

Organs that can be donated

Kidney (x2), Heart, Lungs (x2), Liver, Pancreas, Intestine

Tissue that can be donated

Corneas, Heart valves, Skin, Bone, Tendons, Cartilage, Veins

Currently, there are over 113,000 people in the U.S. waiting for an organ transplant, of which 84 % are in need of kidneys.  Sadly, 22 people die every day waiting for an organ transplant that does not come in time. The prospect of an effective treatment for type 1 diabetes means hope for thousands of people living with the chronic condition.