Search

The expression of integrin molecules α1β1, α4β1 and αVβ3 within endometrial tissue has been proposed as a marker of uterine receptivity during the implantation window. The present investigation examines by flow cytometric analysis the concentrations of α1, α4, αV and β3 integrin subunits in endometrial stromal (ESC) and epithelial cells (EEC) in two groups of women throughout the menstrual cycle: normal fertile women (n = 27) and women with unexplained infertility (n = 26). Integrin concentrations in endometrial cells were calculated in relative fluorescence units against a negative cellular control. The assessment of integrin subunits detected the protein in ESC and EEC from the late proliferative to the late secretory phase. In both groups of women, the α1 was the highest integrin expressed in ESC and EEC throughout the menstrual cycle. All women exhibited low concentrations of α4-EEC at the time of the implantation window. Infertile women expressed lower concentrations of the α4-ESC during the proliferative and early secretory phase while lower concentrations of the α1-ESC were seen during the late secretory phase. Interestingly, the infertile women expressed lower concentrations of β3-EEC in the early, mid-secretory and late secretory phases (P < 0.05). Infertile women also expressed lower concentrations of α1-EEC and αV-EEC during the late secretory phase (P < 0.05). It can be concluded that the quantitative determination of β3-EEC by flow cytometry confirmed its potential feature as a marker of endometrial receptivity at the time of the implantation window. In addition, the defective expression of the α1-ESC found in the late secretory phase might be associated with the poor fertility outcome of women with unexplained infertility.

The expression of integrin molecules alpha1beta1, alpha4beta1 and alphaVbeta3 within endometrial tissue has been proposed as a marker of uterine receptivity during the implantation window. The present investigation examines by flow cytometric analysis the concentrations of alpha1, alpha4, alphaV and beta3 integrin subunits in endometrial stromal (ESC) and epithelial cells (EEC) in two groups of women throughout the menstrual cycle: normal fertile women (n = 27) and women with unexplained infertility (n = 26). Integrin concentrations in endometrial cells were calculated in relative fluorescence units against a negative cellular control. The assessment of integrin subunits detected the protein in ESC and EEC from the late proliferative to the late secretory phase. In both groups of women, the alpha1 was the highest integrin expressed in ESC and EEC throughout the menstrual cycle. All women exhibited low concentrations of alpha4-EEC at the time of the implantation window. Infertile women expressed lower concentrations of the alpha4-ESC during the proliferative and early secretory phase while lower concentrations of the alpha1-ESC were seen during the late secretory phase. Interestingly, the infertile women expressed lower concentrations of beta3-EEC in the early, mid-secretory and late secretory phases (P < 0.05). Infertile women also expressed lower concentrations of alpha1-EEC and alphaV-EEC during the late secretory phase (P < 0.05). It can be concluded that the quantitative determination of beta3-EEC by flow cytometry confirmed its potential feature as a marker of endometrial receptivity at the time of the implantation window. In addition, the defective expression of the alpha1-ESC found in the late secretory phase might be associated with the poor fertility outcome of women with unexplained infertility.

It has been reported that the mammalian corpus luteum is composed mainly of two subpopulations of luteal cells (large and small) of different morphology and function. The aims of this study were first to characterize cytologically the human corpus luteum throughout the luteal phase, and second to establish the in-vitro steroidogenic capacity of a well-defined human mid-luteal cell system. The results show that the most predominant (> 70%) cell shape, is polyhedric, and the number of cells per unit area is significantly different in the early, mid- and late corpus luteum (P < 0.005). Moreover, small cells (< 22 microns) were most common (56.8%) in all tissues analysed. On the other hand, both subpopulations synthesized progesterone, oestradiol and testosterone, although a significantly greater production of basal steroids was observed in large luteal cells (P < 0.05). Nevertheless, the response of small cells to human chorionic gonadotrophin (HCG) was significantly greater (P < 0.05) than that of large cells, in agreement with the preferential specific binding obtained for [125I]HCG to the small cell subpopulation. In summary, these results indicate that the human corpus luteum possesses distinct cell types, which may be related to endocrine function and its control.

The differential capacity for steroid synthesis of human luteal cell subpopulations was investigated in a well defined cell culture system. Corpora lutea were enzymatically dissociated, and the two cell types were obtained by a discontinuous Percoll gradient. Both cell types were cultured for 24 h with dibutyryl cAMP (1 mM), oestradiol (2.5 microM) and testosterone (1 microM). Steroid production was measured in the culture media and aromatase activity for both cell type subpopulations was also determined. Basal production of progesterone, oestradiol and testosterone was significantly greater in large cells than that in small cells (P < 0.05). Nevertheless, a greater response of small cells to several in-vitro treatments was observed. Thus, synthesis of progesterone, oestradiol and testosterone was significantly stimulated in these cells (P < 0.05) by dibutyryl cAMP. Interestingly, a 3.3-fold increase of progesterone production was also observed in the large luteal cell subpopulation. When oestradiol was added to the culture media, a 36% decrease of progesterone production (P < 0.05) by small cells was obtained, while progesterone synthesis by large cells was not significantly affected. Testosterone treatment of cells enhanced oestradiol production by both cell subtypes (P < 0.05), although the stimulatory action was greater in the small cell cultures (5.9-fold). These data indicate that the steroidogenic activity of the small cell subpopulation is highly dependent on endocrine and paracrine stimulatory mechanisms, while large cells possess a greater intrinsic steroidogenic capacity.

Flow cytometry analysis of luteal cells revealed that an important proportion of these cells are leukocytes. The percentage of leukocytes was higher in the early (42 +/- 4) and late (35 +/- 3) luteal phases than in the mid-luteal (24 +/- 2) phase. However, the proportion of macrophages did not differ between the luteal stages. The flow cytometric properties correlated with cellular size and granularity were not reliable as discriminators of luteal cell subpopulations. Therefore, to assess the contribution of luteal leukocytes, these cells were completely removed from luteal cell suspensions (total cells), by a negative selection procedure (immunomagnetic separation). The functional role of leukocytes in mid-luteal steroidogenesis was assessed, in total as well as leukocyte-depleted cells. Progesterone production was found to have increased 2.2-fold in leukocyte-depleted cell cultures, in comparison with total cells under basal conditions. However, the response to human chorionic gonadotrophin (HCG) was 36% lower under the latter conditions. Oestradiol production was not significantly modified under basal or HCG-treated conditions. In leukocyte-depleted cells, the concentration of interleukin (IL)-1beta decreased 5-fold in comparison with total cell cultures, suggesting that leukocytes are the principal source of IL-1beta. In summary, the results of the present investigation suggest functional interactions between the immune system and steroidogenic cells of the human corpus luteum.

The differential capacity for steroid synthesis of human luteal cell subpopulatlons was investigated in a well defmed cell culture system. Corpora lutea were enzymatically dissociated, and the two cell types were obtained by a discontinous Percoll gradient. Both cell types were cultured for 24 h with dibutyryl cAMP (1 mM), oestradlol (2.5 μM) and testosterone (1 μM). Steroid production was measured in the culture media and aromatase activity for both cell type subpopulatlons was also determined. Basal production of progesterone, oestradlol and testosterone was significantly greater in large cells than that in small cells (P<0.05). Nevertheless, a greater response of small cells to several in-vitro treatments was observed. Thus, synthesis of progesterone, oestradiol and testosterone was significantly stimulated in these cells (P<0.05) by dibutyryl cAMP. interestingly, a 3.3-fold increase of progesterone production was also observed in the large luteal cell subpopulation. When oestradiol was added to the culture media, a 36% decrease of progesterone production (P<0.05) by small cells was obtained, while progesterone synthesis by large cells was not significantly affected. Testosterone treatment of cells enhanced oestradiol production by both cell subtypes (P<0.05), although the sthnulatory action was greater in the small cell cultures (5.9-fold). These data indicate that the steroidogenic activity of the small cell subpopulatlon is highly dependent on endocrine and paracrine stimulatory mechanisms, while large cells possess a greater intrinsic steroidogemc capacity.