Characterisation of vitamin D-related molecules and calcium-sensing receptor in human Fallopian tube during the menstrual cycle and in ectopic pregnancy.

This is a prospective observational study that measures the expression of vitamin D (VD) metabolising and signalling molecules and Ca2+ sensing receptor (CaSR) in human Fallopian tube (FT) during the menstrual cycle and ectopic pregnancy (EP). Fresh FTs were obtained during total abdominal hysterectomy at the follicular (n = 16) and midluteal (n = 16) phases. Specimens from remote and implantation sites as well as trophoblastic tissues were also freshly collected from each FT with EP (n = 10). All women had normal serum VD and ionised Ca2+. The expression of VD synthesising (CYP27B1) and catalysing (CYP24A1) enzymes, binding protein (VDBP), receptor (VDR), retinoid X receptor (RXR) and CaSR was measured by immunohistochemistry and quantitative RT-PCR. All molecules, except VDBP, were significantly increased (P < 0.05) in midluteal compared with follicular samples. Remote EP sites showed significantly (P < 0.05) lower expression of CYP27B1, CYP24A1, VDR and RXR and a higher expression of VDBP and CaSR (P < 0.05) compared with midluteal samples. Significant differences were observed by immunohistochemistry between implantation and remote sites from EP for all molecules, which were also localised in the trophoblastic tissues. In conclusion, VD and calcium are under cycle-dependent regulations within human FT and they appear to play a role in tubal biology through paracrine/autocrine mode of signalling. Furthermore, EP was associated with alterations in the expression of all the studied molecules by the tubal epithelium. Further studies are needed to explore the roles of VD in tubal biology and pathogenesis of EP.