Intraovarian regulation of gonadotropin-dependent folliculogenesis depends on notch receptor signaling pathways not involving Delta-like ligand 4 (Dll4)

Abstract

BackgroundIn-situ hybridisation studies demonstrate that Notch receptors and ligands are expressed in granulosa cells (GCs) and in the theca layer vasculature of growing follicles. Notch signaling involves cell-to-cell interaction mediated by transmembrane receptors and ligands. This signaling pathway may represent a novel intraovarian regulator of gonadotropin-dependent follicular development to the preovulatory stage. We hypothesized that blocking Notch pathways would disrupt follicular maturation in the mouse ovary.MethodsHypophysectomized CD21 female mice were administered pregnant mare serum gonadotropin (PMSG) for 3 days to stimulate follicular development. In one experiment, a pan-notch inhibitor, compound E, was initiated 2 days prior to and throughout stimulation (n = 10), while in a second experiment, a humanized phage Dll4 blocking antibody, YW152F, was used (n = 5). After sacrifice, ovarian histology, serum estradiol levels and uterine weights were compared to controls. The ovarian morphology was evaluated with hematoxylin/eosin staining and immunohistochemistry was performed for Notch1, Notch2, Notch3, Notch4, Jagged1, Dll4, platelet endothelial cell adhesion molecule (PECAM) and alpha-smooth muscle actin (α-SMA) detection.ResultsWe localized specific Notch ligands and receptors in the following structures: Dll4 is specific to theca layer endothelial cells (ECs); Notch1/Notch4 and Jagged1 are expressed in theca layer ECs and vascular smooth muscle cells (VSMCs), whereas Notch3 is restricted to VSMCs; Notch2 is expressed mostly on GCs of small follicles. Administration of a pan-Notch inhibitor, compound E, inhibits follicular development to the preovulatory stage (8.5 preovulatory follicles in treatment vs. 3.4 preovulatory follicles in control, p < 0.01; average number per ovary) with significant secondary effects on ovarian and uterine weight and estradiol secretion in a setting of uninhibited vascular proliferation, but disorganized appearance of ECs and VSMCs. Inhibition of endothelial Notch1 function through the inactivation of its ligand Dll4 with the blocking antibody YW152F induces mild disorganisation of follicular vasculature, but has no significant effect on gonadotropin-dependent folliculogenesis.ConclusionsOur experiments suggest that the complete blockage of the Notch signaling pathway with compound E impairs folliculogenesis and induces disruption of gonadotropin stimulated angiogenesis. It seems the mechanism involves Notch1 and Notch3, specifically, causing the improper assembly of ECs and VSMCs in the theca layer, although the potential role of non-angiogenic Notch signaling, such as Jagged2 to Notch2 in GCs, remains to be elucidated.

A link between Notch and progesterone maintains the functionality of the rat corpus luteum

“…Notch signaling pathway with the administration of an inhibitor of the g-secretase complex or DLL4 blocking antibody alters follicular development and induces a disruption of the VEGF-dependent luteal angiogenesis (Garcia-Pascual et al 2013, Jovanovic et al 2013. The present data demonstrate a decrease in progesterone production when CLs obtained from pregnant or superovulated rats were incubated with DAPT, a g-secretase inhibitor.…”

“…In addition, corpora lutea (CL) from marmosets treated with a neutralizing antibody against DLL4 during the periovulatory period exhibit increased vascular density, but smaller size, with involution of luteal cells, increased cell death, and suppressed plasma progesterone concentrations (Fraser et al 2012). Recently, Jovanovic et al (2013) have demonstrated that the in vivo inhibition of the Notch signaling pathway in mice impairs folliculogenesis and induces the disruption of gonadotropin-stimulated angiogenesis. We have previously demonstrated that Notch1, Notch4 and DLL4 are expressed in small and large luteal cells of CL from pregnant rats and have shown evidences that Notch signaling promotes both luteal cell viability and steroidogenesis.…”

“…Notch proteins and ligands have been localized in granulosa, luteal, and vascular cells of the rodent ovary (Johnson et al 2001, Vorontchikhina et al 2005, Jovanovic et al 2013. In addition, corpora lutea (CL) from marmosets treated with a neutralizing antibody against DLL4 during the periovulatory period exhibit increased vascular density, but smaller size, with involution of luteal cells, increased cell death, and suppressed plasma progesterone concentrations (Fraser et al 2012).…”

Notch signaling pathway in cumulus cells can be a novel marker to identify poor and normal responder IVF patients

“…Their results suggest that Notch is a novel intraovarian regulator that regulates folliculogenesis through vascular and nonvascular mechanisms [29].…”

The role of TGF superfamily gene expression in the regulation of folliculogenesis and oogenesis in mammals: a review

“…In all mammalian species, the proper course of folliculogenesis and oogenesis is the main factor that influences the growth and development of cumulus-oocytes complexes, the maturation of oocytes to reach the MII stage and subsequently monospermic fertilisation (Chaves et al 2012;Songsasen et al 2012;Jovanovic et al 2013;Linke et al 2013;Sobinoff et al 2013). Developing from the preantral into the antral stage, the follicle is finally morphologically modified to three separate populations of somatic cell: theca cells, granulosa cells and cumulus oophorus (Figure 1).…”