Cervical fluid pH, electrolytes and osmolarity changes and expression of ion transporters (ENaC, CFTR and AQP) in cervix of women with primary unexplained infertility.

Background: Unexplained infertility could arise from a defect in the cervix. However, the contribution of abnormal cervical fluid microenvironment to this problem still needs to be identified. Therefore, this study identifies the changes in the cervical fluid microenvironment, i.e., pH, electrolytes and osmolarity as well as expression of ion transporters in the cervix including ENaC, CFTR and AQP in fertile women and in women suffering from primary unexplained infertility.

Methods: Fertile women and women with unexplained infertility but having regular 28-day menstrual cycles were chosen in this study, Day-22 serum progesterone levels were determined. In the meantime, serum FSH and LH levels were determined on day 2 while, cervical flushing was performed at day 14 to analyse changes in the cervical fluid pH, osmolarity, Na and Cl levels. Meanwhile, cells retrieved from cervical fluid were subjected to mRNA expression and protein distribution analysis for CFTR, AQP and ENaC by qPCR and immunofluorescence, respectively.

Results: No significant changes in serum progesterone, FSH and LH levels were observed between the two groups. However, cervical fluid pH, osmolarity, Na and Cl levels were significantly lower in primary unexplained infertile group when compared to fertile group. Expression of CFTR and AQP (AQP 1, AQP 2, AQP 5 and AQP 7) in endocervical cells was lower and expression of β-ENaC was higher in primary unexplained infertile women (p < 0.05 when compared to fertile group).

Conclusions: Alterations in the cervical fluid microenvironment linked to the defective ion transporter expression in the cervix might contribute towards the unfavourable condition that accounts for unexplained infertility in women.