BACKGROUND: Presbycusis is an age-related condition characterized by symmetrical bilateral hearing loss that progresses to total deafness in severe cases. Mesenchymal stem cells demonstrate strong therapeutic and regenerative potential, making it worthwhile to explore optimal transplantation pathways for improving age-related hearing loss.
METHODS: Rats were injected with D-galactose to establish an animal model simulating aging. Adipose-derived stem cells were injected intravenously and into the auditory cortex. The hearing of rats was assessed indirectly through the establishment of an acoustic fear conditioned reflex and directly evaluated by the auditory brainstem response. Gabaergic neurons in the auditory cortex were detected using indirect immunofluorescence, and apoptosis was detected using the terminal uridine nick-end labeling method.
RESULTS: In comparison with the control group, rats in the model B group exhibited a poor association between sound and electrical stimulation. Similar results were observed in the group injected intravenously with adipose-derived stem cells (group C). However, acoustical fear conditioning was more effectively established in the auditory cortex injection group (group D). Auditory brainstem response analysis revealed a significantly lower hearing threshold in group D compared with group B, indicating a more pronounced hearing recovery in rats receiving auditory cortex injections, whereas intravenous stem cell injection had no discernible effect. In group D, there was a substantial increase in the number of GABAergic neurons, a slight decrease in apoptotic cells, and a significant decrease in apoptotic GABAergic neurons.
CONCLUSIONS: The injection of adipose-derived stem cells into the auditory cortex is able to ameliorate deafness in rats with simulated aging, which may be effected mainly by increasing the number of GABAergic neurons.
