Luteal leukocytes are modulators of the steroidogenic process of human mid-luteal cells

Abstract

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.

Effect of nitric oxide on the expression of insulin-like growth factors and the insulin-like growth factor binding proteins throughout the lifespan of the human corpus luteum

“…Among these molecules, NO has been suggested as a regulator of human corpus luteum function (Vega et al, 1998(Vega et al, , 2000Johnson et al, 1999). The NO-NO synthase system is expressed throughout the lifespan of the human corpus luteum eliciting an anti-steroidogenic effect Expression of IGFs and IGFBPs in the human corpus luteum 869 Explants from human corpora lutea of different ages (three early corpora lutea, n = 8 slices; five mid-corpora lutea, n = 12 slices; and four late corpora lutea, n = 10 slices) were incubated in supplemented Hank's (L-Arg free) medium for 4 h and the concentration of proteins in the incubation media was determined by specific immunoassays.…”

“…When NO synthase activity was inhibited by N G -monomethyl-Larginine L-NMMA (a competitive inhibitor of NO synthase), steroid production was enhanced, indicating an inhibitory effect of endogenous NO on luteal steroidogenesis. Furthermore, when dispersed luteal cells were coincubated with L-Arginine and L-NMMA, no differences in steroid production were observed (Vega et al, 1998(Vega et al, , 2000Johnson et al, 1999). However, IGFs and IGFBPs have been considered to elicit a regulatory role in the function of the corpus luteum (Parmer et al, 1991;Davis et al, 1996;Niswender et al, 2000).…”

“…Nitric oxide (NO) is produced in most tissues and may regulate different physiological functions, some of which are associated with reproductive processes (Norman and Cameron, 1996). Endothelial and inducible NO synthases are expressed in the human corpus luteum throughout its lifespan (Vega et al, 1998). As has been described in other tissues (Dimmeler and Zeiher, 1997), NO has an antisteroidogenic action (Johnson et al, 1999) and induces apoptosis in the human corpus luteum (Vega et al, 2000).…”

“…Some of these products act as intraovarian regulators of the menstrual cycle (Remohi et al, 1996;Castro et al, 1998), for example the insulin-like growth factors, IGF-I and -II (Remohi et al, 1996). The biological actions of IGF-I and -II, which include proliferation and cellular differentiation, are regulated by six binding proteins named IGFBP-1 to -6 (Feld and Hirschberg et al, 1996).…”

Regulatory T Cells in the Corpus Luteum—New Players in Fertility Control?

“…Its rapid generation from the remnants of the follicle after each ovulation involves an array of cell lineages in an extraordinary process of proliferation, differentiation, and neovascularization unparalleled in any other tissue in the body. Immune cells, including macrophages, neutrophils, and dendritic cells, are abundant in the developing CL [1,2] and are thought to facilitate tissue remodeling events as well as control of steroidogenic function [3][4][5]. At luteolysis, the number of leukocytes increases even further, and a role in apoptosis and clearance of regressing tissue is proposed [6].…”