Middlesex Professor Tunes into Hearing Regeneration

Frank Stellabotte, Ph.D., professor of biochemistry and biotechnology at CT State Middlesex, carried out a research project at the Biological Imaging Facility of the Bronner Lab, California Institute of Technology, during his sabbatical last fall. The project seeks to understand the way cells of the inner ear are regenerated in species that, unlike humans, can recover from hearing loss.

Dr. Stellabotte

Frank Stellabotte, Ph.D.

Specifically, Dr. Stellabotte researched hearing in zebrafish. According to an article in Animal Frontiers journal, zebrafish are a unique model animal for biomedical research, including studies of biological processes and human diseases. Zebrafish are available at pet stores and were selected to become a genetic model because of their extraordinary ability to generate eggs.

Dr. Stellabotte’s research was prompted by statistics cited by the Hearing Health Foundation, which states nearly 50 million Americans experience hearing loss. Ringing in the ears, or tinnitus, affects 20% of Americans and hearing loss occurs in 90% of those cases.

“Hearing loss is currently a significant issue and is expected to impact a larger percentage of the population in the future,” Dr. Stellabotte noted in his April presentation to the CT State Middlesex campus.

“The cells responsible for hearing, called sensory hair cells, regenerate in zebrafish and do not regenerate in humans,” he explained. “The inner ear development is easily observable in zebrafish. The clear eggs and clear body development allow this to be visualized. The sensory hair cells can be labeled with a red dye.” (video of zebrafish at Middlesex)

This diagram shows the similarities between the zebrafish inner ear structure and the inner ear in mammals:

zebrafish and mouse ears

The parts of the inner ear with an auditory function are highlighted in blue. The sensory hair cells of mammals are found in a structure called the cochlea (c), whereas fish possess an auditory saccule (s) and lagena (l). The utricle (u) and semicircular canals (ssc) are used for balance in both fishes and mammals.

“All vertebrate ears use the same cells for hearing (sensory hair cells), and it is these cells that are lost with exposure to noise and some medications. Support cells are cells that are next to hair cells not responsible for hearing,” said Dr. Stellabotte.

The sensory hair cells in zebrafish regenerate in one of two ways. First by trans-differentiation, where the support cell becomes a sensory hair cell directly, and secondly, through asymmetric cell division, where the support cells divides and gives rise to an additional support cell and a sensory hair cell.

“We can actually see this regeneration in zebrafish inner ears,” said Dr. Stellabotte, who used a confocal microscope to watch cells as the regenerate after ablation with a laser.

Dr. Stellabotte and Caltech lab colleague Miyuki Suzuki, Ph.D., also developed a technique to study developmental processes in salamanders. Dr. Stellabotte hopes to return to Caltech to continue these studies in various species of salamanders. Salamanders are widely studied because of their regenerative ability.

“Axolotyls are salamanders that exhibit amazing healing and regenerative capacities,” he said. “Studying the ear of salamanders can help us understand how the change from aquatic to terrestrial habitats affects the ear morphology—what roles have shifted from the inner ear to the middle ear.” This transition from water to land is one of the most interesting transitions in the history of vertebrate evolution. The questions how and when this transition from water to land occurred is quite possibly the most highly debated topic in the study of evolution.

Dr. Stellabotte also attended the Society of Integrative and Comparative Biology annual conference in Seattle as well as the Bioscience LA conference on biomanufacturing. At Middlesex, he teaches Molecular Genetics, Biochemistry and Biotechnology courses. Students can earn the biotechnology associate of science degree, which is designed to prepare them with a comprehensive background and laboratory technical skills for the purpose of immediate entry into laboratory positions.

Dr. Stellabotte is also exploring a possible new degree program in biomanufacturing and industry trends such as fermentation science. He hopes to provide CT State students with training opportunities at one or more of the 115 operational beer breweries in the state.

June 2024
Written by Thea Moritz