Table 1.

Therapeutic Genes Used for Inner Ear Gene Therapy

Gene	Main target	Protective effect
Neurotrophic factors	Hair cells, neurons	Comprehensive protection, such as antiapoptosis, antioxidation, and modulation of neuronal physiological and biochemical activities
1. Neurotrophin family
2. Glial cell line-derived neurotrophic factor family
3. Ciliary neurotrophic factor family
4. Fibroblast growth factor family
5. Other neurotrophically acting factors such as epidermal growth factor (EGF), transforming growth factor (TGF), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), and hepatocyte growth factor (HGF)
Otospiralin	Nonsensory epithelial cells of the inner ear	Maintaining normal structure and function of the fibrocytes and other nonsensory epithelial cells in inner ear
Antiapoptotic agents	Hair cells, neurons, other inner ear cells	Antiapoptosis
XIAP, IAPs, and Bcl-2 family
Connexins	Gap junctions in inner ear	Maintaining normal structure and function of the gap junction of the inner ear
Such as Cx26 (GJB2), Cx30 (GJB6), Cx31 (GJB3), and Cx43 (GJA1)
Atonal-related factors or bHLH transcription factors	Supporting cells of the organ or Corti and its adjacent nonsensory epithelial cells	Inducing a phenotypic trans-differentiation from nonsensory cells to the hair cells
Such as Math1, Cath1, Xath1, and Hath1

bHLH, basic helix–loop–helix; IAP, inhibitor of apoptosis; XIAP, X-linked IAP.