Luteinizing hormone stimulates ingression of mural granulosa cells within the mouse preovulatory follicle

Abstract

Luteinizing hormone (LH) induces ovulation by initiating signaling by the mural granulosa cells that surround a mammalian oocyte in an ovarian follicle. However, much remains unknown about how LH activation of its receptor (LHR) modifies the structure of the follicle such that the oocyte is released and the follicle remnants are transformed into the corpus luteum. The present study shows that the preovulatory surge of LH stimulates LHR-expressing granulosa cells, initially located almost entirely in the outer layers of the mural granulosa, to rapidly extend inwards, intercalating between other cells. The proportion of LHR-expressing cell bodies in the inner half of the mural wall increases until the time of ovulation, with no change in the total number of cells expressing the receptor. Many of the initially flask-shaped cells appear to detach from the basal lamina, acquiring a rounder shape with multiple filipodia. Following the ingression of the LHR-expressing cells, but still hours before ovulation, the follicular wall develops numerous invaginations and constrictions. LH stimulation of granulosa cell ingression may contribute to changes in the follicular structure that enable ovulation.

Phosphatases modified by LH signaling in ovarian follicles: testing their role in regulating the NPR2 guanylyl cyclase

“…SSH1 dephosphorylates and activates proteins in the cofilin/actin depolymerizing factor family (CFL1, CFL2, DSTN) (44), and is of high interest because LH signaling decreases cofilin phosphorylation in isolated granulosa cells, causing an increase in motility (45). Granulosa cell motility increases in intact ovarian follicles after the preovulatory surge of LH and may contribute to the ovulatory process (46).…”