The microenvironment surrounding the stem cells is called as niche [21]. It has a significant role in the maintenance of stem cells and enables them to keep proliferate and differentiate into mature cells. However, the niche for inner ear stem cells is unknown. It is necessary to elucidate the regulatory mechanisms of inner ear stem cells, clarify what keeps the inner ear stem cells in quiescent condition, and identify the reason for the decrease in the number of inner ear stem cells with maturation. If these questions are addressed to activate inner ear stem cells in vivo, it will be a great step in regeneration therapy.
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