BACKGROUND The best-known role of spermatozoa is to fertilize the oocyte and to transmit the paternal genome to offspring. These highly specialized cells have a unique structure consisting of all the elements absolutely necessary to each stage of fertilization and to embryonic development. Mature spermatozoa are made up of a head with the nucleus, a neck, and a flagellum that allows motility and that contains a midpiece with a mitochondrial helix. Mitochondria are central to cellular energy production but they also have various other functions. Although mitochondria are recognized as essential to spermatozoa, their exact pathophysiological role and their functioning are complex. Available literature relative to mitochondria in spermatozoa is dense and contradictory in some cases. Furthermore, mitochondria are only indirectly involved in cytoplasmic heredity as their DNA, the paternal mitochondrial DNA, is not transmitted to descendants. OBJECTIVE AND RATIONAL This review aims to summarize available literature on mitochondria in spermatozoa, and, in particular, that with respect to humans, with the perspective of better understanding the anomalies that could be implicated in male infertility. SEARCH METHODS PubMed was used to search the MEDLINE database for peer-reviewed original articles and reviews pertaining to human spermatozoa and mitochondria. Searches were performed using keywords belonging to three groups: ‘mitochondria’ or ‘mitochondrial DNA’, ‘spermatozoa’ or ‘sperm’ and ‘reactive oxygen species’ or ‘calcium’ or ‘apoptosis’ or signaling pathways’. These keywords were combined with other relevant search phrases. References from these articles were used to obtain additional articles. OUTCOMES Mitochondria are central to the metabolism of spermatozoa and they are implicated in energy production, redox equilibrium and calcium regulation, as well as apoptotic pathways, all of which are necessary for flagellar motility, capacitation, acrosome reaction and gametic fusion. In numerous cases, alterations in one of the aforementioned functions could be linked to a decline in sperm quality and/or infertility. The link between the mitochondrial genome and the quality of spermatozoa appears to be more complex. Although the quantity of mtDNA, and the existence of large-scale deletions therein, are inversely correlated to sperm quality, the effects of mutations seem to be heterogeneous and particularly related to their pathogenicity. WIDER IMPLICATIONS The importance of the role of mitochondria in reproduction, and particularly in gamete quality, has recently emerged following numerous publications. Better understanding of male infertility is of great interest in the current context where a significant decline in sperm quality has been observed.

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线粒体：它们在精子和男性不育中的作用

背景 精子最广为人知的作用是使卵母细胞受精并将父本基因组传递给后代。这些高度特化的细胞具有独特的结构，由每个受精阶段和胚胎发育绝对必需的所有元素组成。成熟的精子由一个带有核的头部、一个颈部和一个允许运动的鞭毛组成，其中包含一个带有线粒体螺旋的中段。线粒体是细胞能量产生的核心，但它们也具有各种其他功能。尽管线粒体被认为是精子所必需的，但它们的确切病理生理作用和功能是复杂的。在某些情况下，与精子中的线粒体相关的现有文献非常密集且相互矛盾。此外，线粒体仅间接参与细胞质遗传，因为它们的 DNA，即父系线粒体 DNA，不会传递给后代。目的和合理性 本综述旨在总结关于精子中线粒体的现有文献，特别是关于人类的文献，以更好地了解可能与男性不育有关的异常情况。搜索方法 PubMed 用于在 MEDLINE 数据库中搜索与人类精子和线粒体有关的经过同行评审的原创文章和评论。使用属于三组的关键字进行搜索：“线粒体”或“线粒体 DNA”、“精子”或“精子”和“活性氧”或“钙”或“细胞凋亡”或信号通路”。这些关键字与其他相关的搜索词组相结合。这些文章的参考文献被用来获得更多的文章。结果 线粒体是精子代谢的核心，它们与能量产生、氧化还原平衡和钙调节以及凋亡途径有关，所有这些都是鞭毛运动、获能、顶体反应和配子融合所必需的。在许多情况下，上述功能之一的改变可能与精子质量下降和/或不育有关。线粒体基因组与精子质量之间的联系似乎更为复杂。尽管 mtDNA 的数量以及其中是否存在大规模缺失与精子质量呈负相关，但突变的影响似乎是异质的，尤其与它们的致病性有关。更广泛的影响 线粒体在繁殖中的作用，特别是在配子质量中的重要性，最近在大量出版物之后出现。在目前观察到精子质量显着下降的情况下，更好地了解男性不育症非常重要。