A lack of commensal microbiota influences the male reproductive tract intergenerationally in mice. A lack of commensal microbiota influences the male reproductive tract intergenerationally in mice

The microbiome encompasses the array of microorganisms inhabiting various niches in the body and is necessary for numerous physiological processes, including normal metabolism and a functioning immune system. Not only does the absence of a microbiome in mice impact the exposed animals but also inherited phenotypes in successive generations of progeny, suggesting that the absence of a microbiome impacts the germline and gametes. Indeed, recent research has identified a role of the gut microbiome in contributing to male fertility, in both healthy and disease states. While this link is beginning to be established, the impact of the microbiome on the male reproductive tract remains understudied. Here, we utilized a germ-free mouse model to examine the influence of the absence of microbes on the male reproductive tract. In contrast to mice with an established microbiome, germ-free mice display decreased testicular weight and the prevalence of an epididymitis-like inflammation phenotype. These histopathological changes are accompanied by transcriptomic dysregulation in the reproductive tract of germ-free mice, particularly in the cauda epididymis. Moreover, such transcriptomic changes are transmitted to the next generation with high correlation of gene expression in the cauda epididymis between germ-free mice and their conventionalized (microbiome-restored) male offspring, when compared to control mice. Ultimately, our findings identify the reproductive sequalae of males without a functional microbiome and additionally in their conventionalized offspring, suggesting that the paternal microbiota is an underappreciated contributor to male reproductive function. Overall design: To investigate the influence of microbiota on the male reproductive tract we collected testis from specific pathogen free control mice (SPF) and germ-free mice (GF) (n = 3-4) and caput and cauda epididymis tissue from SPF, GF and male offspring from GF x SPF parents for RNA-seq. We also investigated the role of T and B cells in directing gene expression changes by performing RNA-seq on caput and cauda epididymal tissue from Rag2 knockout male mice.

微生物组（microbiome）指定植于机体各类微生态位的微生物群落，是诸多生理过程——包括正常代谢与免疫系统正常运作——不可或缺的核心组分。小鼠体内微生物组的缺失不仅会影响无菌环境暴露个体的生理状态，还会引发子代的遗传表型异常，这提示微生物组缺失会对生殖细胞系与配子产生调控影响。近期研究确证了肠道微生物组在健康与疾病状态下对雄性生育能力的关键作用。尽管这一关联已初步得到验证，但微生物组对雄性生殖道的整体影响仍未得到充分研究。本研究采用无菌小鼠（germ-free, GF）模型，旨在探究微生物组缺失对雄性生殖道的调控效应。与定植有正常微生物组的小鼠相比，无菌小鼠的睾丸重量显著降低，且呈现出类似附睾炎（epididymitis）的炎症表型。此类组织病理学变化伴随无菌小鼠生殖道内的转录组失调（transcriptomic dysregulation），尤以附睾尾（cauda epididymis）最为显著。进一步研究发现，此类转录组变化可传递至子代：与对照小鼠相比，无菌小鼠与其菌群定植恢复（conventionalized，即microbiome-restored）雄性后代的附睾尾基因表达呈现高度相关性。本研究最终明确了无功能性微生物组雄性个体的生殖后遗症，同时揭示了其菌群定植恢复后代的相关表型特征，提示父代微生物组是雄性生殖功能中一个长期被忽视的重要调控因素。整体实验设计：为探究微生物组对雄性生殖道的影响，我们收集了无特定病原体（specific pathogen free, SPF）对照小鼠与无菌小鼠的睾丸样本（每组n=3~4），并采集了SPF小鼠、无菌小鼠以及无菌小鼠与SPF小鼠亲代所产雄性后代的附睾头（caput epididymis）与附睾尾组织样本用于RNA测序。此外，我们通过对Rag2基因敲除（Rag2 knockout）雄性小鼠的附睾头与附睾尾组织进行RNA测序，进一步探究了T细胞与B细胞对基因表达变化的调控作用