Li Shuai, Garcia Marleny, Gewiss Rachel L, Winuthayanon Wipawee
School of Molecular Biosciences, College of Veterinary Medicine, Washington State University, Pullman, Washington, United States of America.
PLoS Genet. 2017 Apr 17;13(4):e1006743. doi: 10.1371/journal.pgen.1006743. eCollection 2017 Apr.
Semen liquefaction changes semen from a gel-like to watery consistency and is required for sperm to gain mobility and swim to the fertilization site in the Fallopian tubes. Kallikrein-related peptidases 3 (KLK3) and other kallikrein-related peptidases from male prostate glands are responsible for semen liquefaction by cleaving gel-forming proteins (semenogelin and collagen). In a physiological context, the liquefaction process occurs within the female reproductive tract. How seminal proteins interact with the female reproductive environment is still largely unexplored. We previously reported that conditional genetic ablation of Esr1 (estrogen receptor α) in the epithelial cells of the female reproductive tract (Wnt7aCre/+;Esr1f/f) causes female infertility, partly due to a drastic reduction in the number of motile sperm entering the oviduct. In this study, we found that post-ejaculated semen from fertile wild-type males was solidified and the sperm were entrapped in Wnt7aCre/+;Esr1f/f uteri, compared to the watery semen (liquefied) found in Esr1f/f controls. In addition, semenogelin and collagen were not degraded in Wnt7aCre/+;Esr1f/f uteri. Amongst multiple gene families aberrantly expressed in the absence of epithelial ESR1, we have identified that a lack of Klks in the uterus is a potential cause for the liquefaction defect. Pharmacological inhibition of KLKs in the uterus replicated the phenotype observed in Wnt7aCre/+;Esr1f/f uteri, suggesting that loss of uterine and seminal KLK function causes this liquefaction defect. In human cervical cell culture, expression of several KLKs and their inhibitors (SPINKs) was regulated by estrogen in an ESR1-dependent manner. Our study demonstrates that estrogen/ESR1 signaling in the female reproductive tract plays an indispensable role in normal semen liquefaction, providing fundamental evidence that exposure of post-ejaculated semen to the suboptimal microenvironment in the female reproductive tract leads to faulty liquefaction and subsequently causes a fertility defect.
精液液化可使精液从凝胶状变为水样，这是精子获得运动能力并游向输卵管受精部位所必需的。来自男性前列腺的激肽释放酶相关肽酶3（KLK3）和其他激肽释放酶相关肽酶通过切割形成凝胶的蛋白质（精液凝胶蛋白和胶原蛋白）来负责精液液化。在生理情况下，液化过程发生在女性生殖道内。精液蛋白如何与女性生殖环境相互作用在很大程度上仍未得到探索。我们之前报道，雌性生殖道上皮细胞中Esr1（雌激素受体α）的条件性基因敲除（Wnt7aCre/+;Esr1f/f）会导致雌性不育，部分原因是进入输卵管的活动精子数量大幅减少。在本研究中，我们发现，与Esr1f/f对照组中呈水样的精液（已液化）相比，可育野生型雄性射精后的精液在Wnt7aCre/+;Esr1f/f子宫中凝固，精子被困其中。此外，精液凝胶蛋白和胶原蛋白在Wnt7aCre/+;Esr1f/f子宫中未被降解。在缺乏上皮ESR1时异常表达的多个基因家族中，我们已确定子宫中缺乏激肽释放酶相关肽酶是液化缺陷的一个潜在原因。子宫中激肽释放酶相关肽酶的药理学抑制复制了在Wnt7aCre/+;Esr1f/f子宫中观察到的表型，表明子宫和精液中激肽释放酶相关肽酶功能的丧失导致了这种液化缺陷。在人宫颈细胞培养中，几种激肽释放酶相关肽酶及其抑制剂（丝氨酸蛋白酶抑制剂Kazal型1家族成员，SPINKs）的表达以ESR1依赖的方式受雌激素调节。我们的研究表明，雌性生殖道中的雌激素/ESR1信号在正常精液液化中起不可或缺的作用，提供了基本证据，即射精后的精液暴露于雌性生殖道中次优的微环境会导致液化异常，进而导致生育缺陷。
