Our previous study has demonstrated that bicarbonate in the uterine fluid plays an indispensable role in sperm capacitation. However, the cellular mechanisms underlying the formation of bicarbonate-rich uterine fluid and the regulatory mechanism remained largely unknown. In this study, the expression profiles of bicarbonate transport/production proteins, the cystic fibrosis transmembrane conductance regulator (CFTR), SLC26A6, carbonic anhydrase 2 (CAR2, CA2) and CAR12 (CA12), throughout the estrous cycle, were examined in the mouse uterus by western blot. The results showed that the maximum expression levels of the proteins examined were observed at estrus. Luminal surface pH measurements showed that the resting uterine surface pH at estrus was significantly higher than that at diestrus, which could be reduced significantly by CFTR blocker, diphenylamine-2,2′-dicarboxylic acid, SLC26A6 inhibitor, 4′,4′-diisothiocyanostilbene-2′,2′-disulfonic acid, and CA inhibitor, acetazolamide. In ovariectomized mice and primary culture of endometrial epithelial cells, estrogen could upregulate CFTR, SLC26A6, CAR2, and CAR12 expression with a corresponding increase in the bicarbonate-dependent short-circuit current (I sc) and endometrial surface pH. The present results have demonstrated dynamic changes in uterine bicarbonate secretion and expression of the proteins involved in bicarbonate secretion during the estrous cycle and suggested a novel role of estrogen in regulating uterine bicarbonate transport, which may be important for successful reproduction.
Qiong He, Hui Chen, Connie Hau Yan Wong, Lai Ling Tsang and Hsiao Chang Chan
Hui Chen, Jing Hui Guo, Xiao Hu Zhang and Hsiao Chang Chan
Polycystic ovarian syndrome (PCOS) is one of the most frequent causes of female infertility, featured by abnormal hormone profile, chronic oligo/anovulation, and presence of multiple cystic follicles in the ovary. However, the mechanism underlying the abnormal folliculogenesis remains obscure. We have previously demonstrated that CFTR, a cAMP-dependent Cl− and HCO3 − conducting anion channel, is expressed in the granulosa cells and its expression is downregulated in PCOS rat models and human patients. In this study, we aimed to investigate the possible involvement of downregulation of CFTR in the impaired follicle development in PCOS using two rat PCOS models and primary culture of granulosa cells. Our results indicated that the downregulation of CFTR in the cystic follicles was accompanied by reduced expression of proliferating cell nuclear antigen (PCNA), in rat PCOS models. In addition, knockdown or inhibition of CFTR in granulosa cell culture resulted in reduced cell viability and downregulation of PCNA. We further demonstrated that CFTR regulated both basal and FSH-stimulated granulosa cell proliferation through the HCO3 −/sAC/PKA pathway leading to ERK phosphorylation and its downstream target cyclin D2 (Ccnd2) upregulation. Reduced ERK phosphorylation and CCND2 were found in ovaries of rat PCOS model compared with the control. This study suggests that CFTR is required for normal follicle development and that its downregulation in PCOS may inhibit granulosa cell proliferation, resulting in abnormal follicle development in PCOS.
Xiao Sun, Ye Chun Ruan, Jinghui Guo, Hui Chen, Lai Ling Tsang, Xiaohu Zhang, Xiaohua Jiang and Hsiao Chang Chan
In our previous study, we have demonstrated that the epithelial sodium channel (ENaC) mediates the embryo-derived signals leading to the activation of CREB and upregulation of cyclooxygenase type 2 (COX2) required for embryo implantation. This study aims to investigate whether microRNAs (miRNAs) are involved in the ENaC-induced upregulation of COX2 during embryo implantation. The results show that the levels of miR-101 and miR-199a-3p, two COX2 targeting miRNAs, are reduced by ENaC activation, and increased by ENaC inhibition or knock-down of ENaC subunit (ENaCα) in human endometrial surface epithelial (HES) cells or in mouse uteri during implantation. Phosphorylation of CREB is induced by the activation of ENaC, and blocked by ENaC inhibition or knockdown in HES cells. Knockdown of ENaCα or CREB in HES cells or in mouse uterus in vivo results in increases in miR-101 and miR-199a-3p, accompanied with decreases in COX2 protein levels and reduction in implantation rate. The downregulation of COX2 caused by knockdown of ENaC or CREB can be recovered by the inhibitors of miR-101 or miR-199a-3p in HES cells. These results reveal a novel molecular mechanism modulating COX2 expression during embryo implantation via ENaC-dependent CREB activation and COX2-targeting miRNAs.
Ruiying Diao, Kin Lam Fok, Li Zhao, Hao Chen, Hui Tang, Jing Chen, Aiping Zheng, Xiaohu Zhang, Yaoting Gui, Hsiao Chang Chan and Zhiming Cai
Sperm quality declines with aging; however, the underlying molecular mechanism remains elusive. The cystic fibrosis transmembrane conductance regulator (CFTR) has been shown to play an essential role in fertilizing capacity of sperm and male fertility. This study aimed to investigate the involvement of age-dependent CFTR downregulation in lowering sperm quality in old age. Two hundred and one healthy fertile men of three age groups (20–40 years, n=64; 40–60 years, n=61; and >60 years, n=76) were recruited. Expression of CFTR was determined by RT-PCR, western blot, and immunofluorescence staining. Collected sperm were treated with CFTR inhibitor or potentiator. Sperm quality was assessed by motility and bicarbonate-induced capacitation. The results showed that the expression of CFTR on the equatorial segment and neck region of sperm was significantly decreased in an age-dependent manner. Reduction of CFTR expression in sperm from old men was correlated with lowered forward motility and decreased HCO3 − sensitivity required for sperm capacitation. Activation of CFTR by genistein partially rescued the decreased forward motility in sperm from old men. Decreased CFTR expression in sperm was also found to be associated with lowered sperm quality in aging mice. These results suggest that age-dependent downregulation of CFTR in sperm leads to lowered sperm quality in old age sperm. CFTR may be a pontential target for rescuing sperm motility as well as a fertility indicator in old age men.
Huijuan Liao, Yan Chen, Yulong Li, Shaolong Xue, Mingfeng Liu, Ziyuan Lin, Yanyan Liu, Hsiao Chang Chan, Xiaohu Zhang and Huaqin Sun
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene affect fertility in both sexes. However, the involvement of CFTR in regulating germ cell development remains largely unknown. Here, we used zebrafish model to investigate the role of CFTR in primordial germ cells (PGCs) development. We generated a cftr frameshift mutant zebrafish line using CRISPR/Cas9 technique and investigated the migration of PGCs during early embryo development. Our results showed that loss of Cftr impairs the migration of PGCs from dome stages onward. The migration of PGCs was also perturbed by treatment of CFTRinh-172, a gating-speciﬁc CFTR channel inhibitor. Moreover, defected PGCs migration in cftr mutant embryos can be partially rescued by injection of WT but not other channel-defective mutant cftr mRNAs. Finally, we observed the elevation of cxcr4b, cxcl12a, rgs14a and ca15b, key factors involved in zebrafish PGCs migration, in cftr-mutant zebrafish embryos. Taken together, the present study revealed an important role of CFTR acting as an ion channel in regulating PGCs migration during early embryogenesis. Defect of which may impair germ cell development through elevation of key factors involved in cell motility and response to chemotactic gradient in PGCs.