The day when a profoundly deaf patient's own bone marrow cellscould be used to let him or her hear the world is nearer, thanks to work by a team at the Indiana University School of Medicine.

In the laboratory, the IUSM group, led by Eri Hashino, associateprofessor and Ruth C. Holton Scholar in Department of Otolaryngology-Headand Neck Surgery, transformed stem cells taken from adult bonemarrow into cells with many of the characteristics of sensorynerve cells, or neurons, found in the ear. The cells used inthe research are called marrow stromal cells, a type of stemcell from which fat, bone, and cartilage normally develop.

Their results suggest that these adult stem cells could be usedto treat deaf patients in the future, says Hashino.

“We were interested in marrow stromal cells because of theirpotential for use in autologous cell-based therapy,” Hashinosays, referring to cell transplantation in which a patient'sown cells are used in treatment. The cells can be collected safelyand easily and kept alive in the laboratory until needed, sheadds.

Other researchers had previously shown that the marrow stromalcells could be induced to transform into neuronal cells, butit wasn't clear whether, or how, the cells could be further transformedinto useful specialized neurons.

In a two-step process, Hashino and her colleagues first cultivatedmouse marrow stromal cells with chemicals known to encouragestems cells to change into primitive neurons. The bone marrowcells took the shape and other characteristics of neurons. Next,they exposed the cells to two molecules that are secreted fromtissues of the ear during embryonic development. Together, thetwo molecules, known as Sonic hedgehog (a gene identified in1978 and named for the Sega Genesis game character) and retinoicacid, caused the marrow stromal cells to further develop intocells with many characteristics, such as the presence of specificgenes and proteins, of auditory neurons.

Hashino and her colleagues are beginning new experiments totest the feasibility of marrow stromal cell transplantation tostimulate the growth of nerve cells that are often missing fromthe inner ears of patients with profound hearing loss.

“Sonic hedgehog and retinoic acid are molecules found in embryonictissues but not in adult tissues,” Hashino explains. “This suggeststhat treating marrow-derived stem cells with these moleculesbefore transplantation might greatly enhance the possibilitythat the process would result in development of specific sensoryneurons.”

This study was published in the March 29 issue of Proceedings of the National Academy of Sciences . Hashino's research is funded by the National Institutes of Health-National Institute on Deafness and Other Communication Disorders.