The Use of Primary Spiral Ganglion Cells in Studying Glutamate Receptor Function and Excitotoxicity in the Cochlea

Sensorineural hearing loss (SNHL) can result from genetic mutations, excessive noise exposure, ototoxic drugs, and aging. Glutamate excitotoxicity is one of the underlying mechanisms of SNHL. However, the specific roles of different glutamate receptor subtypes in normal signaling and excitotoxic damage remain unclear. Addressing these questions requires relevant experimental models. This review compares existing protocols for the isolation and cultivation of primary spiral ganglion cells. It also evaluates the utility of this model for studying glutamatergic transmission and glutamate-induced excitotoxicity. A literature search was conducted in PubMed, Scopus, Google Scholar, and Web of Science. We identified 16 relevant English-language articles published since 1990, when the model was first used to study glutamatergic signaling. Our analysis reveals significant heterogeneity in spiral ganglion cell isolation protocols and culture conditions. We highlight major differences in glutamate concentrations and exposure times used to model excitotoxicity. The most significant limitation of this model is the loss of the native microenvironment of auditory neurons, including their dendritic and axonal contacts. Nevertheless, primary spiral ganglion cells serve as a suitable in vitro model for investigating auditory neuron function and pathology. The number of neurons and neurite length serve as reliable indicators of otoprotective effects under conditions of glutamate excitotoxicity. Based on an analysis of the key stages of primary SGC culture establishment, this study proposes approaches to overcome limitations and improve the practice of using this model. A better understanding of the function of glutamate receptors of SGNs and the mechanisms behind glutamate excitotoxicity could help us to develop new treatments for SNHL. This review serves as a practical guide for researchers implementing or optimizing primary SGC cultures.