MicroRNA profiling in male rat germ cells after chronic cyclophosphamide treatment

Although numerous miRNAs have been identified in the testis, their roles in regulating the highly specific events that occur in the different germ cell types throughout spermatogenesis remain largely unknown. Furthermore, whether male germ cell miRNA expression is altered in response to or as a consequence of exposure to a toxic agent is unknown. Here we examine miRNA expression profiles in pachytene spermatocytes and round spermatids obtained from control rats and from rats treated with a chronic low dose of cyclophosphamide, a male germ cell toxicant. We observed that pachytene spermatocytes and round spermatids display vastly different miRNA expression profiles, reflecting their different developmental stages and possibly influencing the cellular response to toxic insult. Chronic low dose cyclophosphamide treatment altered the miRNA profiles in both pachytene spermatocytes and round spermatids. Target prediction analyses revealed that miRNAs altered by cyclophosphamide treatment may be involved in the response to cellular stress and damage. However, many are also involved in processes that are crucial for proper germ cell development. This study suggests that pachytene spermatocytes and round spermatids display distinct miRNA profiles that can be altered by cyclophosphamide treatment. The observed changes may be part of a response and repair mechanism to cyclophosphamide-induced damage or a dysregulation that disrupts normal germ cell development.尽管目前已在睾丸中鉴定出诸多微小RNA（miRNA），但在整个精子发生过程中，它们调控不同生殖细胞类型所发生的高度特异性事件的具体作用，仍尚未完全明确。此外，雄性生殖细胞的miRNA表达是否会响应有毒物质暴露而发生改变，或是此类暴露所导致的结果，目前仍未可知。本研究针对对照组大鼠及经慢性低剂量环磷酰胺（一种雄性生殖细胞毒物）处理的大鼠，分离获取其粗线期精母细胞与圆形精子细胞，对二者的miRNA表达谱展开分析。研究发现，粗线期精母细胞与圆形精子细胞的miRNA表达谱存在显著差异，这一差异反映了二者所处的发育阶段不同，也可能影响细胞对毒性损伤的应答反应。慢性低剂量环磷酰胺处理，可使粗线期精母细胞与圆形精子细胞的miRNA表达谱发生改变。靶基因预测分析显示，经环磷酰胺处理后表达发生改变的miRNA，可能参与细胞应激与损伤的应答过程；但其中诸多miRNA同时也参与对生殖细胞正常发育至关重要的生物学过程。本研究表明，粗线期精母细胞与圆形精子细胞具有各自独特的miRNA表达谱，且此类表达谱可因环磷酰胺处理而发生改变。本次研究观测到的表达变化，可能是机体针对环磷酰胺诱导的损伤所启动的应答与修复机制的一部分，也可能是扰乱生殖细胞正常发育的表达失调现象。