Common 677C-->T mutation of the 5,10-methylenetetrahydrofolate reductase gene affects follicular estradiol synthesis.

OBJECTIVE: To investigate the influence of the 5,10-methylenetetrahydrofolate reductase 677C-->T mutation on the E(2) synthesis in human granulosa cells (GCs).
DESIGN: In vitro cell culture study.
SETTING: Research laboratory of a university hospital. PATIENT(S): Follicular fluids (n = 139) and GCs (n = 66) were obtained from patients undergoing controlled ovarian hyperstimulation for IVF with or without ICSI. INTERVENTION(S): Granulosa cells were cultured for a total of 5 days. On day 3, the cells either were stimulated with recombinant (r-) FSH or r-LH (80 IU/L for 48 h) or were sham stimulated. MAIN OUTCOME MEASURE(S): Estradiol and protein content were measured in the pooled follicular fluids of each individual. At the end of each GC-culturing period, the concentrations of E(2) were measured in the supernatants of triplicate cultures by immunoassays. The 5,10-methylenetetrahydrofolate reductase 677C-->T genotype was determined by RFLP analysis. RESULT(S): The E(2)-protein ratio of homozygous T/T carriers was significantly lower compared with that of homozygous C/C individuals. Furthermore, basal and r-FSH- as well as r-LH-stimulated E(2) synthesis of GC obtained from homozygous T/T patients was significantly reduced, compared with GC from heterozygous C/T and homozygous C/C subjects. CONCLUSION(S): Decreased E(2) in follicular fluid and decreased E(2) synthesis of GC from homozygous T/T individuals suggest that reduced follicular E(2) is a result of impaired E(2) production of human GC.