New Stem Cell Research for Hearing Impairment

Author: Dr. Karen
Published: 2009/01/11
Category Topic: Regenerative Medicine - Academic Publications

Page Content: Synopsis - Introduction - Main

Synopsis: Transforming stem cells into sensory nerve cells called neurons for hearing impairments.

Introduction

Main Content

Stem cells occur naturally in the human body. They are not blood cells, nerve cells, brain cells or any other kind of cell. In fact, they have no identity by themselves, at least not yet.

They can, however, develop into different types of cells, replacing cells that have been damaged or are somehow, defective. They have the ability to clone themselves and make more stem cells.

Adult stem cells, which exist in mature body tissue and organs, continuously renew their numbers as needed throughout an individual's life, replacing damaged cells as needed. It is this fact that caused researchers to wonder if these stem cells could correct hearing loss.

When the outer ear captures the sound waves traveling through the air and then directs it into the ear canal it is said that hearing occurs. This is where you find the tympanic membrane (ear drum) and the three smallest bones in the human body namely, the stirrup, hammer and anvil. You will also find the cochlea, a snail-shaped organ that contains delicate, hair-like nerve fibers that translate sound waves into electrical impulses that are, in turn, transmitted to the brain. The hair-like nerve fibers are very delicate and can be damaged or impaired very easily due to age, disease, exposure to loud noise and other medical and non-medical conditions. Hearing-loss, most often permanent in nature, is the result of the damage to these nerves.

With this in mind, a group of researchers from the Indiana University School of Medicine under the instruction of Dr. Eri Hashino, Ph. D., set out to find out if they could transform cell nerves into sensory nerve cells, called neurons. To do this, they took stem nerves from the bone marrow of lab mice and transformed it into cells that had numerous characteristics similar to neurons. Neurons transmit sound from the outside world to the brain where the sound is processed and interpreted. These results suggest the possibility to re-grow and replace damaged neurons with the stem cells taken from bone marrow. Dr. Hashino stated that their interest in the marrow cells was due to their potential use in autologous cell-based therapy (using stem cells from a patient as a part of that patient's treatment). They were ideal for use as the bone marrow cells are easily collected and can be kept alive in the laboratory until needed.

Around the same time of Dr. Hashino's experiments, additional research was conducted in Tokyo. These studies revealed that the bone marrow stem cells injected into a damaged ear can speed hearing recovery after partial hearing loss. It showed that some re-growth of cochlear fibrocytes is possible after these cells have been damaged. However, only partial recovery was observed over a period of weeks, but patients who experience traumatic hearing loss tend to permanently lose their ability to hear high frequency sounds.

Research on the practical use of a patient's stem cells to restore or improve hearing is just beginning.

Animal studies indicate the potential to regenerate the nerves that convert sound waves into electrical impulses that are subsequently delivered to the brain for processing.

Today, the future looks bright for restoring the sense of hearing to those who have lost or are losing it.

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