Altered steroidogenic pattern of human granulosa-lutein cells in relation to cumulus cell culture morphology

It has been reported that human cumulus-oocyte complexes (COC) retrieved at a stimulated cycle manifest an asynchrony between oocyte meiotic maturation and cumulus mucification. However, when mature COC were subdivided into subtypes marked by the culture morphology of their cumulus cells following 3 days' culture, successful fertilization and cleavage were approximately 1.5-fold lower in mature COC yielding cumulus cells aggregated into clumps (type A and B COC) than in mature COC yielding homogeneously spread cells (type C-D COC). To determine whether the existing relationship between cumulus culture morphology and oocyte functionality in the various COC types (A-D) could be extended to another follicular compartment—the granulosa-lutein (G-L) cells—basal steroid secretion by the corresponding G-L cells was evaluated within 5 days of culture. Over the first 3 days of culture, secretion of progesterone was 3-fold lower and secretion of testosterone (T) was 2.5-fold higher in cultures of G-L cells from follicles yielding type A COC than in type C-D COC. During days 4 and 5 of culture, G-L cells were incubated with or without 10⁻⁷M 3β-hydroxy-5-pregnen-20-one (pregnenolone), dehydroepiandrosterone (DHA), 4-androstene-3,17-dione (androstenedione), or T. The pattern of progesterone level noted over the first 3 days of culture was not altered in the presence of pregnanolone, DHA, androstenedione, or T. Addition of pregnenolone, DHA, androstenedione, or T increased T level 2.5-, 5.6-, 7.3-, and 17.7-fold, respectively, in cultures of G-L cells from follicles yielding type A COC, but did not significantly alter T level in cultures of G-L cells from follicles yielding type C-D COC. In cultures of G-L cells from follicles yielding type A COC, addition of androgens unsaturated at position 4 preferentially increased oestradiol-17β (E₂) level, whereas in cultures of G-L cells of type C-D COC, DHA and androstenedione preferentially increased E₂ level. Taken together, the asynchrony between oocyte and cumulus activity could be diminished when the activity of various follicular cell compartments is evaluated according to cumulus culture morphology rather than cumulus expansion and mucification. The present study suggests that follicles yielding mature COC represent a non-homogeneous population in which G-L cells from follicles yielding type A-B COC manifest a less luteinized state than those from follicles yielding type C-D COC.