Regulation of Mammalian Cochlear Regeneration by BMP4

描述（申请人提供）：感音神经性耳聋影响近一半的50岁以上成年人。感觉神经性耳聋主要是由耳蜗机械感觉细胞（感觉毛细胞）的累积损失引起的，这些细胞在胚胎发育过程中分化并且没有被替换。相比之下，成年的非哺乳脊椎动物可以再生失去的感觉毛细胞，但是在这些动物中允许再生的信号是未知的。我们希望利用一种新的体外系统来研究可能调节出生后哺乳动物耳蜗感觉毛细胞分化的信号。在该系统中，小鼠胚胎耳蜗上皮细胞能够存活、增殖并分化为感觉毛细胞。我们在这里作为初步数据显示，纯化的新生儿支持细胞有能力重新进入细胞周期，并在该试验中表达感觉毛细胞标记物。通过反复试验，我们已经确定BMP4是支持细胞进入细胞周期的潜在负调节因子。这一数据之所以重要，有两个原因：首先，BMP4在鸟类和小鼠的耳蜗中都有表达，尽管在不同的种群中；第二，BMP4在再生的鸟类耳蜗中下调，但在哺乳动物中可能没有下调。因此，我们的模型提供了一个简单且可验证的假设，解释为什么鸟类可以再生，而哺乳动物却不能。我们拟通过实验来确定BMP4抑制增殖的机制，BMP4是否也在感觉毛细胞分化中发挥作用，以及干扰BMP4信号通路是否可以促进体外哺乳动物耳蜗再生。随着年龄的增长，人们会失去听力，因为内耳的振动感应细胞会死亡。鸟类会自然地再生它们的振动感应细胞，我们认为这个过程是由一种叫做BMP4的分子调节的。我们想通过改变小鼠内耳器官培养物中BMP4的活性来验证这一想法。

DESCRIPTION (provided by applicant): Sensorineural deafness affects nearly half of adults over the age of 50. Primarily, sensorineural deafness is caused by the accumulated loss of mechanosensory cells in the cochlea, the sensory hair cells, which differentiate during embryogenesis and are not replaced. Adult non-mammalian vertebrates, in contrast, can regenerate lost sensory hair cells, but the signals that permit regeneration in these animals are unknown. We wish to investigate signals that may regulate sensory hair cell differentiation in the post-natal mammalian cochlea, using a novel in vitro system. In this system mouse embryonic cochlear epithelial cells can survive, proliferate, and differentiate into sensory hair cells. We show here as preliminary data that purified neonatal supporting cells have the ability to re-enter the cell cycle and express sensory hair cell markers in this assay. Through trial and error, we have identified BMP4 as a potential negative regulator of cell cycle entry by supporting cells. This data is important for two reasons: first, BMP4 is expressed in the cochleae of both birds and mice, although in different populations; second, BMP4 is down-regulated in the regenerating avian cochlea, but probably not in mammals. Thus, our model provides a simple and testable hypothesis for why birds might regenerate, but mammals do not. We propose experiments to determine the mechanism by which BMP4 might inhibit proliferation, whether BMP4 also plays a role in sensory hair cell differentiation, and whether interfering with the BMP4 signaling pathway might promote regeneration in the mammalian cochlea in vitro. People lose their hearing as they get older because the vibration-sensing cells in their inner ears die. Birds naturally regenerate their vibration-sensing cells, and we think this process is regulated by a molecule called BMP4. We want to test this idea by changing BMP4 activity in cultures of mouse inner ear organs.