The concentration-dependent effect of progesterone on follicle growth in the mouse ovary

Abstract

Follicle growth in the mammalian ovary is coordinately controlled by multiple factors to sustain periodic ovulation. In this study, we investigated the role of progesterone on follicle growth in the mouse ovary. As the concentration of progesterone changes during the estrus cycle, we cultured the sliced mouse ovary in a medium containing 10 ng/ml, 100 ng/ml, and 1 μg/ml progesterone. Progesterone promoted the growth of primordial to primary follicles at 100 ng/ml, while it suppressed the growth of secondary follicles at 1 μg/ml. Follicles at other developmental stages in the cultured ovary were unaffected with different concentrations of progesterone. The number of ovulated oocytes increased in the medium containing 100 ng/ml progesterone but decreased in the presence of 1 μg/ml progesterone. Follicles expressed two types of progesterone receptors, progesterone receptor (PGR) and PGR membrane component 1 (PGRMC1). While PGR shows transient expression on granulosa cells of Graafian follicles, PGRMC1 expresses in granulosa cells of developing follicles. These results suggest that progesterone controls the growth of developing follicles through PGRMC1. Our study shows that the effect of progesterone on ovulation and follicle growth in mouse ovary is dependent on the concentration of progesterone and the follicle stage.

Keywords: Follicle growth; Ovary culture; Progesterone; Progesterone receptor membrane component 1 (PGRMC1).

Fig. 1.

Images of the cultured ovaries. Images of cultured ovaries of culture day 1 and culture day 14 are presented. Except the cultured ovary containing 1 μg/ml P₄, each cultured ovary ovulated some oocytes before culture day 14. Scale bar: 200 μm.

Fig. 2.

Tracking follicle growth in the cultured ovary. Change in the average follicle area within the cultured ovary. Panels A, B and C: area of primordial-primary follicles. Panels D, E and F: area of secondary follicles. Panels G, H and I: area of antral follicles. Panels A, D and G: control and follicles treated with 10 ng/ml P₄. Panels B, E and H: control and follicles treated with 100 ng/ml P₄. Panels C, F and I: control and follicles treated with 1 μg/ml P₄. Black circles and lines, control; black squares and dash lines, follicles treated with P₄. Data are presented as the mean ± SD. * P < 0.05; ** P < 0.01.

Fig. 3.

The number of ovulated oocytes during the culture period. Black bars, control; gray bars, ovaries treated with P₄. C: control, P₄: progesterone. 10 ng/ml, 100 ng/ml, and 1 μg/ml: concentrations of P₄. Data are presented as the mean ± SD. * P < 0.05.

Fig. 4.

The concentration of 17β-estradiol in the cultured ovaries and the culture medium. Comparison of the concentration of 17β-estradiol between normal culture condition and treatment group with P₄. 12 h and 24 h indicate the time of treatment with DMSO (control) or P₄. Black bar: control group, gray bar: treatment group with P₄. There was no significant difference between each control and treatment group. Data are presented as the mean ± SD.

Fig. 5.

Immunohistochemistry of PGRMC1 in mouse ovary. Panels A and B, C and D, and E and F are images of adjacent mouse ovary sections. Panels A, C and D: stained with anti-PGRMC1 antibody. Panels B, D and F: stained with rabbit IgG. Panel A: arrows, primordial follicles expressing PGRMC1 in granulosa cells; arrowheads, primordial follicles without PGRMC1 expression. Panel C: arrows, primary follicles expressing PGRMC1 in granulosa cells; Panel D: arrows, same follicles indicated in panel C. Panel E and F: * secondary follicle; ** antral follicle expressing PGRMC1 in granulosa cells. Scale bar: 50 μm.

Fig. 6.

The concentration of P₄ in the serum of mouse during estrus cycle and pregnancy. The change in the concentration of P₄ in the serum of mouse during estrus cycle. The concentration of P₄ at metestrus and diestrus was undetected in this experiment; therefore, the concentration at these stages was presented as 0 ng/ml in this graph. There was no significant difference between proestrus, estrus, and pregnant day 7. There was significant difference between metestrus/diestrus and other stages (P < 0.01). Data are presented as the mean ± SD.