piRNA在生殖系统中的功能研究进展

piRNA(Piwi-interacting RNA)是2006年发现的一种新的小RNA,长度约24到30个核苷酸,其作用与Dicer酶无关,与Piwi蛋白家族成员相结合才能发挥作用。目前研究piRNA的功能都基本限定在生殖细胞中,近来研究表明piRNA对于生殖细胞功能的很多环节有巨大的影响,而且对生殖支持细胞的影响的研究也有了进展。本文就piRNA在生殖系统中的功能的研究进展作一综述。     

非编码RNA与哺乳动物生殖细胞生长发育

基因转录后调控是表观遗传学的主要内容,是指通过DNA层面的修饰使原来拥有相同基因型的不同组织或细胞呈现出不同的表型和功能。非编码RNA作为此表观遗传调控的主要执行者之一,能够在转录水平调控蛋白质丰度,在生殖系统中更是发挥了基础调节者的作用。广义的非编码RNA包含了rRNA、tRNA、微小RNA（miRNA）、小干扰RNA（siRNA）、Piwi蛋白相互作用的RNA（piRNA）和长链非编码RNA（lncRNA）等。由于rRNA、tRNA已被人们较为熟知,文章主要选取miRNA、siRNA、piRNA等非编码RNA,针对其近期的研究进展,阐述该类非编码RNA在哺乳动物生殖细胞中的表达以及对生殖细胞发生、成熟的影响及作用机制。与此同时,还对另一类非编码RNA——lncRNA做基本的介绍。     

PIWI蛋白相互作用RNA与生殖功能的关系

PIWI蛋白相互作用RNA(PIWI-interacting RNA,piRNA)是长度大约有24～31个核苷酸的非编码RNA,特异性表达于动物的生殖细胞中。piRNA的生成过程可分为细胞核内的转录以及细胞质内的后期加工两部分。piRNA可以在PIWI家族蛋白的协助下发挥沉默转座子基因和调控mRNA等功能,并可进一步调控生殖功能。在雄性生殖功能中,piRNA可以在PIWI家族蛋白的协助下通过控制组蛋白泛素连接酶RNF8、谷胱甘肽过氧化物酶5等蛋白的表达调控精子发生,引起无精子症、少精子症和弱精子症等影响雄性生殖功能的疾病。在piRNA最初的研究中,学者普遍认为piRNA在雌性生殖方面作用不大,但是近年对金黄地鼠的研究发现piRNA/PIWI复合物在雌性生殖功能的调控过程中也发挥着重要作用。综述piRNA的产生及其与生殖功能的相关性。     

非编码RNA在生殖调节中的研究进展

非编码RNA（ncRNAs）在高等生物体内大量存在,组成十分复杂的生物调控网络,是目前生物医学领域的研究热点。小干扰RNA（siRNA）、微小RNA（miRNA）和PIWI相互作用RNA（piRNA）作为细胞内基因调控网络的重要成员影响细胞的各种生命活动。近年研究表明,ncRNA通过沉默转座元件和调控编码基因等方式在生殖细胞发育、分化、凋亡及激素合成的调控过程中发挥重要作用,ncRNA的异常表达与多囊卵巢综合征（PCOS）和卵巢功能早衰（POF）等生殖疾病密切相关。综述ncRNA在卵泡和胚胎发育以及精子生成等方面的作用及其研究进展。     

小RNA在精子发生中的研究进展

<正>近20年来人们在动物、植物及病毒等生物中发现了一系列小分子非编码RNA,包括miRNA[1]、piRNA[2]和siRNA[3]。与其相关的Argonaut家族蛋白分为2个亚家族:Ago亚家族和Piwi亚家族。精子发生是指由精原细胞经初级精母细胞、次级精母细胞、精细胞至成熟精子形成的过程。整个过程分     

哺乳动物精子RNAs的研究进展

精子RNA量少，但种类多。由于生物技术的发展，多种精子RNA的功能和机制被阐明。微小RNA（miRNAs）和mRNA影响精子形成过程中的染色体固缩、鞭毛结构与动力；与Piwi蛋白相作用的RNA（piRNAs）抑制反转录转座子活性、维持基因组稳定，但作用有限。受精和早期胚胎发育过程中，mRNA调节细胞能量通路、影响配子功能（如核质运输和有丝分裂）；miRNAs和内源性小片段干扰RNA（endo-siRNAs）的缺失会使胚胎早期发育产生异常；部分miRNAs前体（pri-mir-RNAs）以前体形式运输，在受精后激活，调节胚胎干细胞多能性；长链非编码RNA（lncRNAs）可调控胚胎基因组的表达与沉默。实验证明，精子RNA[转运RNA来源的小RNA（tsRNAs）、miRNAs、piRNAs]可作为一种稳定的跨代表观遗传标记，通过修饰、改造遗传物质的高级结构，重塑获得性表型并稳定地传递给子代。     

piRNA在双酚A促进前列腺癌细胞侵袭和迁移中的作用机制研究

目的研究PIWI蛋白相互作用RNA(piRNA)在双酚A(BPA)促进前列腺癌细胞侵袭和迁移中的作用机制。方法利用癌症基因组图谱(TCGA)数据, 分析并筛选在前列腺癌组织中表达显著升高的piRNA。使用不同浓度BPA对前列腺癌PC-3细胞进行12、24和48 h染毒, 结合CCK-8实验确定20%抑制浓度(IC20), 并使用实时荧光定量PCR检测BPA染毒前后piRNA表达水平的改变。随后利用比较毒理基因组学数据库(CTD)筛选受BPA调控且与前列腺癌相关的靶基因, 经双荧光素酶报告基因实验验证piRNA与靶基因的靶向调控关系, 并通过Western blotting检测piRNA靶基因的表达水平, 并进行细胞侵袭和迁移实验探究piRNA及其拮抗剂对PC-3细胞恶性表型的影响。结果 160 μmol/L BPA处理PC-3细胞piR-sno48表达水平升高幅度较大(P<0.05)。转染piR-sno48拮抗剂可导致内源性piR-sno48表达下降及其靶基因GSTP1表达水平升高(P<0.05), 但是BPA染毒的细胞中GSTP1表达未见明显改变(P>0.05)。双...     

端粒酶生物学作用及活性调节

自Blackbum等在二十世纪八十年代先后发现了端粒、端粒酶以后，对它的研究已成为肿瘤学、毒理学、生殖遗传学等研究领域的热门课题。现已证明：端粒酶是一种由RNA和蛋白质组成的核糖核蛋白复合体，具有逆转录酶活性。它在正常组织细胞中不表达，仅在生殖细胞、干细胞、肿瘤细胞中表达。许多研究表明，端粒酶与细胞增殖、细胞衰老和生殖功能的稳定关系密切，因此近十多年来，     

哺乳动物RNA干扰中的小干扰RNA表达载体

载体表达小干扰RNA的方法因便宜，稳定，操作方便的优点，在哺乳动物RNA干扰研究中有非常大的潜力和优势。本文对当前哺乳动物RNA干扰研究中的小干扰RNA表达用载体作一综述。小干扰RNA载体表达方法的广泛应用，将对功能基因组研究以及抗病毒和肿瘤的基因治疗产生深远的影响。     

“贪杯”损害生殖功能

﹃贪杯﹄损害生殖功能沈尔安研究证实，酒所含的酒精能毒害包括生殖细胞在内的一切细胞，对男女生殖系统都有影响。动物实验证明，酒精可使实验动物的睾丸组织发生改变，导致曲细精管变细，生精上皮变黄，破坏睾丸酮的合成。长期和大量饮酒对生殖细胞损害严重，有资料报道...     

Serum levels of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) in relation to markers of reproductive function in young males from the general Swedish population

A time-related deterioration in male reproductive function caused by exposure to endocrine disrupters, including persistent organochlorines (POCs), has been hypothesized. In animal studies, POCs were found to have adverse effects on male reproductive function. However, little is known about the impact of POC exposure on reproductive parameters in men. In a study of 305 young Swedish men 18-21 years old from the general population, we correlated lipid-adjusted serum levels of 2,2',4,4',5,5' -hexachlorobiphenyl (CB-153)--an index substance for POC exposure--to markers of male reproductive function: testis size assessed by ultrasound, sperm concentration, total sperm count, sperm motility assessed manually and with a computer-aided sperm analyzer (CASA), and serum levels of follicle-stimulating hormone, inhibin B, testosterone, sexual hormone-binding globulin (SHBG), luteinizing hormone, and estradiol. We found weak but statistically significant, negative correlations between CB-153 levels and both the testosterone:SHBG ratio (r = -0.25, p < 0.001)--a measure of the biologically active free testosterone fraction--and CASA sperm motility (r = -0.13, p = 0.02). No statistically significant association with other seminal, hormonal, or clinical markers of male reproductive function was found. In previous studies of more highly POC-exposed groups of adult men, the correlation between POC exposure, including CB-153, and free testosterone levels was not statistically significant. The present study gives some tentative support for weak negative effects of CB-153 exposure on sperm motility and free testosterone levels in young men, but further semen studies on more highly exposed groups may give more firm conclusions on the hazard for male reproductive function from dietary POC exposure.     

Sampling strategies for prospective studies of menstrual function

Little information is available about optimal sampling strategies for prospective studies of menstrual function. Sample size and study duration for menstrual studies have often been driven as much by feasibility and cost as by statistical principles, with follow-up lasting 6 months to 2 years and sample size ranging from 100 to 500 women. Whether these studies are sufficiently powered to address common study objectives has not been adequately evaluated, and sample size estimates rarely account for the repeated nature of menstrual cycle data. Using data from the Tremin Trust (a study of menstrual function across the reproductive life span initiated in Minneapolis, Minnesota, in 1935 with data collected through 1977), the authors determined sampling strategies for assessing differences in mean cycle length between two exposure groups and for assessing change in mean cycle length across the reproductive life span. Following a larger number of women for 1-2 years is optimal for studies of host and environmental exposures that alter menstrual function. In contrast, following fewer women for an extended period of time, for example, 4-5 years, is optimal when studying how menstrual patterns vary across the reproductive life span in different populations.     

Epidemiology of male reproductive function: a field searching for tools

BACKGROUND: An increase in the frequency of disorders of the male human reproductive organs has been described over recent decades. Neither its causes nor its consequences on fecundity, the ability of the couples to produce a live child, are clearly known. This lack of knowledge may partly be due to methodological difficulties specific to reproductive epidemiology. METHODS: We discuss the relevance and limits of some markers of the male aspects of human reproduction, focusing on semen parameters and fecundability, a measure of the probability of pregnancy. RESULTS: Semen parameters are associated with fecundability, although they have a relatively low sensitivity to detect couples with low fecundability. The study of semen parameters proved central to describe the influence of environmental factors on the male side of reproductive function. The main limitation of semen studies is low participation rates and the possible selection biases ensuing. Fecundability can be estimated by collecting waiting time to pregnancy. Its assessment in retrospective studies often excludes the least fecund, those couples remaining childless, which entails a bias and a decrease in statistical power. The prospective approach and an approach relying on the enrollment of a cross-sectional sample of the couples currently trying to obtain a pregnancy (current duration approach) do not have these limitations. Although it has never been used, the assessment of fecundability using the current duration approach is promising both for aetiologic research and monitoring. CONCLUSION: Most of the potential markers of male reproductive function are not assessed in the general population of France, with the exception of the incidence rate of testis cancer, which is currently increasing. We present some alternatives for a monitoring system of reproductive function.     

Male reproductive health in relation to occupational exposure to endocrine disrupting and other potent chemicals, a review of the epidemiologic literature

The line of research focusing on the human, especially male, reproductive system in relation to occupational exposure has diversified since the infiltration of the concept of endocrine disrupting chemicals (EDC), early in the 1990s. The main stream, until then, was the study of reproductive toxicity caused by single albeit relatively heavy exposures to chemicals of limited range (conventional scheme). The new and increasingly important stem is the search for a wider range of chemicals with endocrine disrupting potential, and health effects due to multiple low-dose exposures of potent chemicals (new scheme). There are also studies having aspects of both the conventional and new schemes. For studies with the new scheme, progress has been made in areas such as adherence to standardized techniques in evaluating male reproductive function and more sensitive study designs. Indeed, some studies have suggested the presence of EDCs in the occupational setting. However, epidemiological findings are still constrained by difficulties in the identification of occupationally-exposed populations and evaluation of exposure. There is thus a need for convergence of knowledge and a widening of the scope of epidemiological research targeting occupationally exposed populations under a carefully-designed protocol.     

Reproductive toxicity of metals in men

A combination of genetic, environmental and lifestyle factors contributes to adverse effects on the reproductive health in men. Metals are pervasive in food, water, air, tobacco smoke, and alcoholic beverages. Experimental studies suggest that many metals have adverse effects on the male reproductive function. However, information about reproductive effects of human exposure to metals is scarce and/or inconsistent. This review summarises the information from epidemiological studies of the effects of metal exposure on reproductive function in men. Factors capable of affecting these relationships were identified and discussed. A particular attention is given to the studies considering influence of concomitant exposure to various metals. These studies have generally confirmed that even moderate- to low-level exposure to lead affects certain reproductive parameters, and that exposure to cadmium affects the prostate function and serum testosterone levels. Adverse effects of mercury, manganese, chromium and arsenic on semen quality and altered serum hormone are less well documented. There is no clear evidence that boron exposure may impair reproductive health in men. Only a few studies have investigated reproductive effects of concomitant exposure to several metals and controlled for potential confounders. Future studies should consider the contribution of combined exposure to various metals and/or other factors that may influence individual susceptibility to reproductive health impairment in men.     

Identifying environmental risk to male reproductive function by occupational sperm studies: logistics and design options.

Malfunction of the male reproductive system might be a sensitive marker of environmental hazards, the effects of which may extend beyond reproductive function. The testis is more vulnerable to heat and ionising radiation than any other organ of the body and several xenobiotics are known to disrupt spermatogenesis after low level exposure. Studies of environmental impact on human health are often most informative and accurate when carried out in the workplace where exposures can be high and easy to document. Semen analysis provides readily obtainable information on testicular function. The main advantages in comparison with functional measures such as fertility rates and time taken to conceive are the possibilities to examine men independently of marriage and pregnancy, to find changes of fecundity with different exposures within the same person and to detect adverse effects when no alteration of fertility is yet taking place. In the implementation of an occupational sperm study considerable attention must be paid to logistic issues. A mobile laboratory unit for initial semen preparation and processing may in some situations increase worker compliance and the quality of sperm cell motility. The cross sectional design which has been used in almost all male reproductive studies so far has several severe limitations including selection bias because of differential participation, difficulties in defining a suitable reference group, and lack of information about the time dimension of the cause-effect relation. The longitudinal design deals adequately with most of these constraints. Semen samples are collected before, during, and possibly after exposure to the risk factor of interest and causal inferences are based upon change of semen variables within a man over time rather than upon differences between men. The logistics of the longitudinal study may benefit from pre-employment health examinations to enrol newly hired workers and require fewer participants to obtain comparable statistical power. In conclusion, andrological methods and epidemiological designs are available for the implementation of valid studies concerned with environmental impact on human testicular function. Occupational sperm studies should probably not be the first choice when the objective is initial screening of environmental impact on fertility but should be implemented when their is a need to corroborate or refuse earlier evidence that specific exposures have impact on testicular function.     

Women's reproductive health: some recent developments in occupational epidemiology.

Epidemiological research on occupational hazards and reproductive health is an expanding and strongly developing area. This article focuses on some recent areas of occupational reproductive epidemiology that are or seem to be important for the future. Interest in the research on fertility has increased during the past decade, and time to pregnancy has proved to be a useful measure of fertility. The research on menstrual function or early fetal loss is still limited, and further research is desirable. It is important to chart the advantages and disadvantages of various methods for measuring these outcomes. Recently developed methods of exposure assessment provide new possibilities to improve the validity of exposure data. Biological exposure markers can also provide useful dosimeters for reproductive studies. Research on the reproductive effects of job stress and individual susceptibility to reproductive toxicants is also gaining in importance.     

The Use of Probiotics for Management and Improvement of Reproductive Eubiosis and Function

Reproductive tract dysbiosis, due to the action of pathogens and/or unhealthy lifestyle, has been related to many reproductive diseases and disorders in mammalian species. Classically, such a problem has been confronted by the administration of antibiotics. Despite their effectiveness for controlling disease, treatments with antibiotics may negatively affect the fertility of males and females and, mainly, may induce antibiotic resistance. Accordingly, safer alternatives for maintaining reproductive system eubiosis, such as probiotics, are required. The present review summarizes the current knowledge on the biodiversity of the microbiota at the reproductive tract, possible changes in the case of dysbiosis, and their relationships with adequate reproductive health and functioning in both females and males. Afterwards, mechanisms of action and benefits of different probiotics are weighed since the biological activities of probiotics may provide a promising alternative to antibiotics for maintaining and restoring reproductive eubiosis and function. However, at present, it is still necessary for further research to focus on: (a) identifying mechanisms by which probiotics can affect reproductive processes; (b) the safety of probiotics to the host, specifically when consumed during sensitive reproductive windows such as pregnancy; and (c) the hazards instructions and regulatory rules required for marketing these biological-based therapies with sufficient safety. Thus, in this review, to draw a comprehensive overview with a relatively low number of clinical studies in this field, we showed the findings of studies performed either on human or animal models. This review strategy may help provide concrete facts on the eligible probiotic strains, probiotics colonization and transfer route, and prophylactic and/or therapeutic effects of different probiotic strains.