Endocrine Abstracts

There is evidence from animal studies that 1,25-dihydroxyvitamin D3 (1,25-(OH)₂D3) is essential for normal reproductive function. Vitamin D deficient rats have reduced fertility, and VDR null mutant mice demonstrate impaired folliculogenesis. We have recently demonstrated that 1,25(OH)₂D3 suppressed the production of oestradiol (E2) independently of progesterone (P) in luteinised, but not in non-luteinised human granulosa cells, suggesting that 1,25(OH)₂D3 may have a role in modulating luteinisation. VDR have previously been detected on rat granulosa cells and on human ovarian cancer cell lines.

The aim of this study was to determine whether VDR were present on normal human ovarian cells. Luteinised granulosa cells were prepared from IVF procedures and cultured in chamber slides in McCoys 5A medium. After 48 hours culture, the cells were washed and fixed in 4% paraformaldehyde. Immunocytochemistry was then performed with negative controls, using rat monoclonal antibody to VDR and an avidin-biotin-peroxidase system. Freshly dissected corpora lutea (CL) were fixed overnight in 4% paraformaldehyde, and then transferred to 70% ethanol, prior to wax embedding. Sections of 5 micrometers were cut and mounted onto slides. After dewaxing, immunohistochemistry was performed as above. Results demonstrated the presence of the VDR on luteinised granulosa cells with a nuclear staining pattern. VDR were also demonstrated on cells of the CL.

In summary, we have demonstrated the presence of VDR on luteinised granulosa and corpora lutea cells from the normal human ovary for the first time. In conclusion, it is likely that 1,25(OH)₂D3 is acting directly via VDR to modulate steroidogenesis in luteinised granulosa cells.