Control of growth and development of preantral follicle: insights from in vitro culture

Abstract

The regulation of folliculogenesis involves a complex interaction among endocrine, paracrine and autocrine factors. The mechanisms involved in the initiation of the growth of the primordial follicle, i.e., follicular activation and the further growth of primary follicles up to the pre-ovulatory stage, are not well understood at this time. The present review focuses on the regulation and development of early stage (primordial, primary, and secondary) folliculogenesis highlighting the mechanisms of primordial follicle activation, growth of primary and secondary follicles and finally transition from secondary to tertiary follicles. We also discuss the importance of in vitro follicle culture for the understanding of folliculogenesis during the preantral phase. Studies suggest that follicular development from primordial to early antral stages is primarily controlled by intra-ovarian ligands but it can also be influenced by many extra-ovarian factors. The control of early folliculogenesis is, therefore, extremely complex because several ligands act through distinct signaling pathways that form sophisticated information networks responding to multiple, often opposing, stimuli. The balance among different stimuli determines follicular survival or death as well as quiescence or activation (growth). The distribution of the ligands and their corresponding receptors varies among follicular compartments and species, and significant changes in gene expression pattern among follicular categories have been reported. Knowing that follicular requirements during early folliculogenesis can be stage-specific and speciesspecific, in vitro culture studies offer an alternative to evaluate single and combined factors during a specific period of follicular development. Herewith we summarize the main findings obtained in vitro together with the mechanisms regulating folliculogenesis.

Advances in in vitro folliculogenesis in domestic ruminants

“…Folliculogenesis is the physiological process of activation, growth, and maturation of the ovarian follicle. The regulation of folliculogenesis involves a complex interaction among endocrine, paracrine and autocrine factors which in turn affects steroidogenesis, angiogenesis, basement membrane turnover, follicular atresia, oocyte growth, and maturation as well as the proliferation and differentiation of follicular cells (Figueiredo et al, 2018). In the ovary, the distribution of the regulating factors (ligands and their corresponding receptors) varies among follicular compartments (oocyte, granulosa, and theca cells) and significant changes in gene expression pattern among follicular categories (Yoon et al, 2006) have been reported.…”

“…In the ovary, the distribution of the regulating factors (ligands and their corresponding receptors) varies among follicular compartments (oocyte, granulosa, and theca cells) and significant changes in gene expression pattern among follicular categories (Yoon et al, 2006) have been reported. The control of folliculogenesis is extremely complex because the regulating factors act by binding to different types of receptors that activate distinct signaling pathways and, sometimes different ligands share the same receptors (Figueiredo et al, 2018). DOI: 10.21451/1984 In vitro folliculogenesis in ruminants.…”

“…Folliculogenesis during the preantral follicle phase can be divided into three steps: (i) the activation (recruitment) of primordial follicles, i.e., transition from primordial (quiescent follicle) to growing follicles (intermediate and primary follicle); (ii) development of primary and secondary follicles; (iii) transition from preantral to antral follicle. In general, it has been stated that the growth of primordial follicles up to the early antral stage is pituitary independent, being probably controlled by autocrine/paracrine mechanisms and modulated by gonadotrophins (for review see Figueiredo et al 2018). With the understanding of the factors involved in the early folliculogenesis, it will be possible to optimize the use of the large oocyte ovarian reserve in ARTs in humans as well as in other mammalian species.…”

“…Applied research helps to overcome severe infertility either in male or female, as well as to increase the genetic selection rate of highly producing animals (Tan et al, 2017). Among the ARTs that aim to optimize the use in the future of the large ovarian oocyte reserve it is important to highlight the in vitro follicle culture (IVFC) (Green and Shikanov, 2016;Figueiredo et al, 2018). This technique represents an outstanding tool to enhance our understanding of the control of folliculogenesis and to allow the future use of a large number of immature oocytes enclosed in PFs in ARTs in humans as well as in others mammalian species.…”

Prevalência De Curetagens Uterinas No Instituto Da Mulher Dona Lindu No Ano De 2014 – Manaus – Am, Brasil.

“…-PADILHA et al, 2012;GUPTA et al, 2008); iii) TCM-199 (Meio de Cultura de (ROSSETO et al, 2010) e McCoy (MCLAUGHLIN et al, 2010, dentre outros. Estes meios comerciais têm custos elevados que limitam para alguns grupos de pesquisa, a realização de procedimentos de cultivo in vitro objetivando o uso de biotécnicas reprodutivas (FIGUEIREDO et al, 2019(FIGUEIREDO et al, , 2018(FIGUEIREDO et al, , 2011SILVA et al, 2015;CHEN et al, 2010;TELFER et al, 2000).…”