Teicoplanin is a glycopeptide antibiotic used to treat severe staphylococcal infections. It has been claimed that teicoplanin possesses ototoxic potential, although its toxic effects on cochlear hair cells (HCs) remain unknown. The TP53-induced glycolysis and apoptosis regulator (TIGAR) plays a crucial role in promoting cell survival. Prior research has demonstrated that TIGAR protects spiral ganglion neurons against cisplatin damage. However, the significance of TIGAR in damage to mammalian HCs has not yet been investigated. In this study, firstly, we discovered that teicoplanin caused dose-dependent cell death in vitro in both HEI-OC1 cells and cochlear HCs. Next, we discovered that HCs and HEI-OC1 cells treated with teicoplanin exhibited a dramatically decrease in TIGAR expression. To investigate the involvement of TIGAR in inner ear injury caused by teicoplanin, the expression of TIGAR was either upregulated via recombinant adenovirus or downregulated by shRNA in HEI-OC1 cells. Overexpression of TIGAR increased cell viability, decreased apoptosis, and decreased intracellular reactive oxygen species (ROS) level, whereas downregulation of TIGAR decreased cell viability, exacerbated apoptosis, and elevated ROS level following teicoplanin injury. Finally, antioxidant therapy with N-acetyl-L-cysteine decreased ROS level, prevented cell death, and restored p38/phosphorylation-p38 expression levels in HEI-OC1 cells injured by teicoplanin. This study demonstrates that TIGAR may be a promising novel target for the prevention of teicoplanin-induced ototoxicity.

The degeneration of cochlea spiral ganglion neurons (SGNs) results in irreversible sensorineural hearing loss due to the fact that SGNs lack regenerative ability. Cochlear glial cells (GCs) possess limited capacity for neural differentiation. However, the identity of these progenitor cells has been elusive. Here, we identified a distinct subpopulation of cochlear GCs that express Frizzled 10 (FZD10+), which may be the predominant type of GCs responsible for self-proliferation and neuronal differentiation in the neonatal and adult cochlea. Wnt signaling activation significantly promoted the capacity of FZD10 + GCs as neural stem cells, both in vitro and in vivo, and enhanced the neural excitability of the newly induced-neurons. Single-cell RNA sequencing analysis of the proliferated and differentiated FZD10 + GCs revealed that a cluster of neurogenesis-like cells possess characteristics of auditory neurons, suggesting they may be immature SGNs, with multiple signaling pathways, related regulatory genes, and three transcription factors (Pou3f4, Maf and Foxp1) highly expressed in them. Overall, this study identified FZD10 + GCs play a vital role in neurogenesis in the mouse cochlea, and demonstrated the essential function of the Wnt signaling in SGNs regeneration, as well as probed the underlying mechanisms that may be involved in this process.

Teicoplanin, a glycopeptide antibiotic, is used for the treatment of severe staphylococcal infections. Teicoplanin is reported to have an ototoxic potential but its toxic effects on cochlea hair cells (HCs) remains unclear. TP53-induced glycolysis and apoptosis regulator (TIGAR) plays a key role to promote cell survival, our previous study shown that TIGAR protected inner ear spiral ganglion neuron against cisplatin injury. However, the role of TIGAR in mammalian HCs damage has not been explored yet. In this study, firstly, we found that teicoplanin induced significant cell loss of both HEI-OC1 cells and cochlea HCs in a dose-dependent manner in vitro. Next, we discovered that the expression of TIGAR was significantly decreased after teicoplanin treatment in HCs and HEI-OC1 cells. To explore the role of TIGAR in inner ear after teicoplanin damage, the expression of TIGAR was upregulated via recombinant adenovirus or knocked down by shRNA in HEI-OC1 cells, respectively. We found that the overexpression of TIGAR increased cell viability, decreased apoptosis and reduced intracellular reactive oxygen species (ROS) level after teicoplanin injury, whereas downregulation of TIGAR by shRNA decreased cell viability, exacerbated apoptosis and elevated ROS level. Finally, antioxidant treatment with N-acetyl-L-cysteine lowered ROS level, rescued cell loss as well as restored p38/phosphorylation-p38 expression levels induced by TIGAR deficiency in HEI-OC1 cells after teicoplanin injury. This study provides evidences that TIGAR might be a new potential target for prevention from the teicoplanin-induced ototoxicity.