Control of Oocyte Growth and Development by Intercellular Communication Within the Follicular Niche

Abstract

In the mammalian ovary, each oocyte grows and develops within its own structural and developmental niche-the follicle. Together with the female germ cell in the follicle are somatic granulosa cells, specialized companion cells that surround the oocyte and provide support to it, and an outer layer of thecal cells that serve crucial roles including steroid synthesis. These follicular compartments function as a single physiological unit whose purpose is to produce a healthy egg, which upon ovulation can be fertilized and give rise to a healthy embryo, thus enabling the female germ cell to fulfill its reproductive potential. Beginning from the initial stage of follicle formation and until terminal differentiation at ovulation, oocyte and follicle growth depend absolutely on cooperation between the different cellular compartments. This cooperation synchronizes the initiation of oocyte growth with follicle activation. During growth, it enables metabolic support for the follicle-enclosed oocyte and allows the follicle to fulfill its steroidogenic potential. Near the end of the growth period, intra-follicular interactions prevent the precocious meiotic resumption of the oocyte and ensure its nuclear differentiation. Finally, cooperation enables the events of ovulation, including meiotic maturation of the oocyte and expansion of the cumulus granulosa cells. In this chapter, we discuss the cellular interactions that enable the growing follicle to produce a healthy oocyte, focusing on the communication between the germ cell and the surrounding granulosa cells.

Comparison of vaginal microbial community structure of beef cattle between luteal phase and follicular phase

“…Notably, Metagenomic analysis was used to find that the most abundant genera in Nellore Cattle (beef cattle) is Aeribacillus, Bacteroides, Clostridium, Ruminococcus, Rikenella, Alistipes, Bacillus, Eubacterium and Prevotella spp. which comprised of 30-40% of total bacteria in the vaginal microflora (El-Hayek et al 2016). In agreement with previous studies, streptococcus spp., E. coliand lactobacillus spp.were also found in the vagina of beef cattle.…”

Decellularized human ovarian scaffold based on a sodium lauryl ester sulfate (SLES)-treated protocol, as a natural three-dimensional scaffold for construction of bioengineered ovaries

“…On the other hand, close interactions between the oocyte and the surrounding somatic cells are required for the follicle formation; proliferation and differentiation of granulosa cells; and steroid hormone production. Thus, an impaired oocyte-granulosa cell complex would lead to defective folliculogenesis and steroidogenesis [ 47 – 50 ]. Also, the ovarian ECM has various impacts on the oocyte maturation and granulose cell secretion [ 29 ].…”

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“…PCOS is positively correlated with insulin resistance. Testosterone levels were markedly higher in the PCOS group rats than in vehicle control group rats, presumably because insulin resistance might block the conversion of androgen substrates to estradiol 10 . Androgens are synthesized in theca cells and then transported to the granulosa cells where P450 aromatase converts the androgens to estrone and estradiol 11 .…”