Effects of oxygen tension and supplements to the culture medium on activation and development of bovine follicles in vitro

Oocyte development in bovine primordial follicles is promoted by activin and FSH within a two-step serum-free culture system

“…Although major milestones in bovine follicle growth have been realised in vitro, i.e. primordial follicle activation (Wandji et al 1996, Fortune et al 1998, Gigli et al 2006, Yang & Fortune 2006, preantral follicle growth (Wandji et al 1996, Hulshof et al 1997 In vitro day 12…”

“…Katska & Ryńska 1998, Gutierrez et al 2000, Saha et al 2000, Thomas et al 2001, oocyte-cumulus cell complex development (Ralph et al 1995, Hirao et al 2004, and oocyte maturation and fertilisation (Hirao et al 2004), gaps still exist and a complete system capable of supporting the development of immature follicles through to oocyte competency is yet to be defined. It is not known exactly how long it takes for primordial follicles to reach the secondary stage in vivo; however, previous studies have observed a significant reduction in the primordial follicle population with a concomitant increase in the later stages of development in bovine cortical strips grown over 7 (Wandji et al 1996, Gigli et al 2006, 10 (Yang & Fortune 2006 and 20 days (Fortune et al 1998) in vitro, with primordial activation being observed as early as the second day of culture (Fortune et al 1998). In this study, the mean diameter of follicles dissected from cortical fragments cultured for 6 days was 111G1.46 mm, considerably larger than 40 mm, the limit for exclusion from the experiment and smaller than the minimum diameter required for antral formation (Webb et al 1999), indicating that secondary follicles that were present entered the growth phase in vitro from the quiescent pool, and that subsequent antral cavity formation occurred in vitro.…”

“…Individual culture of primordial follicles is technically demanding , Oktay et al 1997; however, initiation of growth and early development in vitro have been achieved in human (Hovatta et al 1997, Telfer et al 2008) and large animal (Wandji et al 1996, 1997, Braw-Tal & Yossefi 1997, Yang & Fortune 2006 follicles within small pieces of ovarian cortex. Previous studies using primate and bovine models have demonstrated a reduction in the primordial population and a corresponding increase in the growing follicle population within gonadotrophin-free cultures of ovarian cortex with activated follicles reaching the secondary stage of development (Wandji et al 1996, 1997, Braw-Tal & Yossefi 1997, Gigli et al 2006, Yang & Fortune 2006. In vitro growth of follicles within cortical pieces can be successfully supported for extended periods of time (Hovatta et al 1997, Louhio et al 2000, Zhang et al 2004, Segino et al 2005, Fabbri et al 2007; however, it is recognised that to achieve advanced development, follicles require to be released from the presumed inhibitory stromal environment , Telfer et al 2008.…”

The effects of different concentrations of sodium selenite on the in vitro maturation of preantral follicles in serum-free and serum supplemented media

“…The high levels of free radicals cause cells damage and loss of their function [12]. Moreover, in vivo cells are protected by defense systems or antioxidants that remove these agents to prevent oxidative damage [13][14][15][16][17].…”

The earliest stages of follicular development: Follicle formation and activation

“…When cortical pieces were cultured with 0, 2.5, 5, or 10% fetal bovine serum (FBS) in the presence of 0, half-strength, or full-strength ITS+, the combinations most effective at increasing the numbers of secondary follicles were half-strength ITS+ with 5% or 10% FBS (Gigli et al 2006). Because there is evidence that androgens stimulate preantral follicular growth in mice and in rhesus monkeys (Murray et al 1998;Vendola et al 1998;Vendola et al 1999;Wang et al 2001), we cultured bovine cortical pieces with testosterone for 10 days.…”