p16INK4a in Cochlear Hair Cell Regeneration.

描述（由申请人提供）：听力损失主要是由内耳耳蜗中的感觉毛细胞（HC）损伤引起的。人类和其他哺乳动物不能替代受损的HC;然而，鸡、鱼和两栖动物可以通过邻近支持细胞（SC）的增殖和转分化来替代受损的HC（Conwin和Oberholtzer，1997年）。有趣的是，肿瘤抑制基因p16 INK 4a在具有再生HC能力的非哺乳动物脊椎动物中不存在（Kim等人，2003; Gil and Peters，2006）.在哺乳动物中，p16 INK 4a作为细胞周期蛋白依赖性激酶抑制剂，使细胞保持静止状态。其表达由年龄以及促有丝分裂信号传导诱导（Zindy等人，1997年）。还已知p16 INK 4a在成体细胞（包括神经元）的体内再生能力中起关键作用（Janzen等人，2006; Molofsky等人，2006年）。通常认为，受损的HC释放导致SC重新进入细胞周期的信号。在非哺乳类脊椎动物中，这导致HC再生;然而，在哺乳动物中，我们预测这种有丝分裂活性诱导p16 INK 4a的表达，使SC保持静止状态，从而防止HC再生。有没有可能通过使p16 INK 4a失活来赋予小鼠鸡再生HC的能力？为了实现这一目标，我们提出了以下中心假设：哺乳动物中p16 INK 4a的失活将允许SC：（1）对由抗生素或基因消融损伤的HC释放的信号做出反应，（2）重新进入细胞周期和（3）再生HC。为了验证这一假设，我们提出了以下具体目标：具体目标1：确定由氨基糖苷类抗生素庆大霉素引起的HC损伤后p161 NK 4a缺失小鼠中SC的再生能力。具体目标二：为了确定p16 INK 4a基因敲除小鼠在出生后HC中视网膜母细胞瘤蛋白急性失活引起HC损伤后SC的再生能力。虽然哺乳动物不能自发地再生HC，但类似于非哺乳动物脊椎动物中发生的HC再生过程可以通过耳蜗SC的遗传和/或治疗操作来诱导。这项建议是朝着最终目标迈出的第一步，即恢复那些暴露于耳毒性药物、噪音或其他环境因素的人的听力。此外，由出生后HC中视网膜母细胞瘤蛋白的急性失活诱导的HC损伤是该领域的技术突破。

DESCRIPTION (provided by applicant): Hearing loss is primarily caused by damage to sensory hair cells (HC) in the cochlea of the inner ear. Humans and other mammals cannot replace damaged HCs; however, chicken, fish and amphibians can, by proliferation and transdifferentiation of neighboring supporting cells (SC) (Conwin and Oberholtzer, 1997). Interestingly, the tumor suppressor gene, p16INK4a, is absent in non-mammalian vertebrates that have the capacity to regenerate HCs (Kim et al., 2003; Gil and Peters, 2006). In mammals, p16INK4a acts as a cyclin-dependent kinase inhibitor that keeps cells in a quiescent state. Its expression is induced by age as well as mitogenic signaling (Zindy et al., 1997). p16INK4a is also known to play a critical role in the in vivo regenerative ability of adult cells, including neurons (Janzen et al., 2006; Molofsky et al., 2006). It is commonly thought that damaged HCs release signals that cause SCs to reenter the cell cycle. In non-mammalian vertebrates this results in HC regeneration; however, in mammals, we predict that this mitotic activity induces the expression of p16INK4a which keeps SCs in a quiescent state and thus prevents HC regeneration. Is it possible to give a mouse, the chicken's ability to regenerate HCs by inactivating p16INK4a? To achieve this goal, we propose the following central hypothesis: Inactivation of p16INK4a in mammals will allow SCs: (1) to respond to signals released from HCs damaged by antibiotics or genetic ablation, (2) to reenter the cell cycle and (3) to regenerate HCs. To test this hypothesis, we propose the following specific aims: Specific Aim 1: To determine the regenerative capacity of SCs in p161NK4a-null mice after HC damage caused by the aminoglycoside antibiotic, gentamicin. Specific Aim 2: To determine the regenerative capacity of SCs in p16INK4a-null mice after HC damage caused by acute inactivation of the retinoblastoma protein in postnatal HCs. Although mammals cannot spontaneously regenerate HCs, a process of HC regeneration similar to what occurs in non-mammalian vertebrates could be induced by genetic and/or therapeutic manipulations of cochlear SCs. This proposal is the first step toward the final goal of restoring hearing in those exposed to ototoxic drugs, loud noise or other environmental agents. In addition, HC damage induced by acute inactivation of the retinoblastoma protein in postnatal HCs is a technological breakthrough for the field.