Stem cells were put to use yet again, but this time to partially restore hearing in those with age related hearing loss or presbycusis. Researchers of Third Military Medical University in Chongqing, China recently used embryonic neural stem cells (NSCs) to grow auditory neurons that have degenerated over time.
Hearing loss is usually the result of damaged/lost hair cells in the ear or degenerated auditory neurons who’s function was to interpret the signals from hair cells for the brain. This study focused on maturing new auditory neurons from NSCs to restore hearing.
C57BL/6J mice, those that would rapidly develop hearing loss similar to human presbycusis, age 2 months and 10 months were used in this study. The older group represented late stage presbycusis while the younger group represented normal hearing. Embryonic NSCs were transplanted from mice embryos into both groups of mice and were evaluated weekly for maturation and similarity to normal auditory neurons.
2 weeks after implantation the age group showed returned auditory function. Before transplantation, the aged group could not detect sounds below about 80dB; however, post-transplantation sounds could be detected at the lower threshold of 60dB. These restorative effects diminished at the four week mark. The young group of mice had an unchanged pre/post transplant auditory threshold of 40dB. Additionally, the rate of cell survival and apoptosis, cell suicide, was measured pre/post-transplant in both groups. The aged group showed high survival of transplanted NSCs and lower rate of apoptosis (25% down to 15%, P<0.05). The young group, acting as a control, showed no significant change in cell survival or apoptotic rate pre/post-transplant.
The transplanted neural stem cells were able to restore hearing in the presbycusis afflicted mice although temporary. With further research, perhaps this regenerative therapy could be used to restore auditory function permanently.
Hongmiao Ren, Jichuan Chen, Yinan Wang, Shichang Zhang, Bo Zhang. Intracerebral neural stem cell transplantation improved the auditory of mice with presbycusis. International Journal of Clinical and Experimental Pathology, 2013.