Autophagy and apoptosis have a complex interplay in the early embryo development. The development of spiral ganglion neurons (SGNs) in addition to Corti’s organ in the mammalian cochlea remains crucial in the first two-week postnatal period. To investigate the roles of apoptosis and autophagy in the development of SGNs, light microscopy was used to observe the morphological changes of SGNs. The number of SGNs was decreased from P1 to P7 and plateaued from P10 to P14. Immunohistochemistry results revealed positive expression of cleaved-caspase3, bcl-2, microtubule-associated protein light chain 3-II (LC3-II), Beclin1, and sequestosome 1 (SQSTM1/P62) in SGNs. The apoptotic bodies and autophagosomes and autolysosomes were also identified by transmission electron microscopy at P1 and P7. Real-time PCR and western blotting results revealed that the apoptotic activity peaked at P7 and the autophagy activity was gradually upregulated along with the development. Taken together, our results for the first time showed that autophagy and apoptosis in SGNs play distinct roles during specific developmental phases in a time-dependent manner.

中文翻译：

---

大鼠螺旋神经节神经元出生后发育过程中凋亡和自噬相关蛋白和基因的不同表达模式

自噬和细胞凋亡在早期胚胎发育中具有复杂的相互作用。除了哺乳动物耳蜗中的 Corti 器官外，螺旋神经节神经元 (SGN) 的发育在出生后的前两周仍然至关重要。为了研究细胞凋亡和自噬在 SGNs 发展中的作用，使用光学显微镜观察 SGNs 的形态变化。SGN 的数量从 P1 减少到 P7，并从 P10 稳定到 P14。免疫组织化学结果显示，在 SGN 中，cleaved-caspase3、bcl-2、微管相关蛋白轻链 3-II (LC3-II)、Beclin1 和 sequestosome 1 (SQSTM1/P62) 呈阳性表达。在 P1 和 P7 通过透射电子显微镜也鉴定了凋亡小体和自噬体和自溶酶体。实时荧光定量 PCR 和蛋白质印迹结果显示细胞凋亡活性在 P7 达到峰值，自噬活性随着发育而逐渐上调。总之，我们的结果首次表明，SGNs 中的自噬和凋亡在特定发育阶段以时间依赖性方式发挥着不同的作用。