Influence of hyaluronic acid synthesis and cumulus mucification on bovine oocyte in vitro maturation, fertilisation and embryo development

Abstract

During cumulus-oocyte complex (COC) maturation, cumulus expansion involves the deposition of mucoelastic compounds, especially hyaluronic acid, synthesised from glucose via the hexosamine biosynthesis pathway. The aim of the present study was to determine the effects of uridine monophosphate (UMP) and 6-diazo-5-oxo-L-norleucine (DON), inhibitors of hyaluronic acid synthesis, during bovine oocyte in vitro maturation (IVM) on cumulus expansion, glucose uptake, protein synthesis, cumulus cell number, meiotic maturation, cleavage rate and subsequent embryo development. A further aim of the study was to examine the effect of hyaluronic acid on sperm capacitation and acrosome reaction in relation to the capacity of COCs to be fertilised in vitro. A low correlation between glucose uptake and degree of cumulus expansion was observed. Total and partial inhibition of cumulus expansion was observed with DON and UMP, respectively, and was accompanied by a decrease in glucose uptake with DON. Total protein content and cumulus cell number per COC increased during IVM, but was unaffected by the presence of DON or UMP, as was oocyte meiotic maturation. Rates of cleavage and blastocyst development decreased in oocytes matured with DON and UMP, although this inhibition was reversed when the in vitro fertilisation (IVF) medium contained heparin. Hyaluronic acid induced capacitation and the acrosome reaction, and in IVF medium prevented the inhibition of cleavage and blastocyst development by DON in a similar fashion to heparin. Hyaluronic acid synthesis during cumulus mucification contributes to the penetration and fertilisation of bovine oocytes, most likely by facilitating the processes of capacitation and acrosome reaction. Mucification during IVM is independent of cumulus cell proliferation, COC protein content, oocyte meiotic maturation and subsequent developmental competence once fertilised.

Bone morphogenetic protein 15 and fibroblast growth factor 10 enhance cumulus expansion, glucose uptake, and expression of genes in the ovulatory cascade during in vitro maturation of bovine cumulus–oocyte complexes

“…Interestingly, in our study, BMP15 and FGF10 increased expression of mRNA encoding GFPT1 and GFPT2, key enzymes involved in directing glucose metabolism down the hexosamine pathway. In a previous study, the inhibition of GFPT activity attenuated cumulus expansion in bovine COCs (Gutnisky et al 2007). Conversely, in our study, increased GFPT expression could probably result in greater amounts of precursor for hyaluronic acid synthesis, especially in the presence of increased HAS2 and therefore enhanced cumulus expansion.…”

Impact of linoleic acid on bovine oocyte maturation and embryo development

“…At least in pigs, volumetric expansion of the COCs correlates with the outcome of oocyte maturation (Qian et al 2003), where hyaluronan, through the effect on its receptor CD44, regulates the disruption of gap junctions in the COCs and concurrently controls the incidence of meiotic resumption (Sato & Yokoo 2005). However, in cattle, inhibition of cumulus cell expansion was shown to be independent from nuclear maturation, but essential for fertilization and subsequent cleavage and blastocyst development (Gutnisky et al 2007). Thus, inhibition of cumulus cell expansion observed in the study presented here may contribute to the reduced developmental potential of these oocytes.…”

The pivotal role of glucose metabolism in determining oocyte developmental competence

“…Supplementing IVM with glucosamine resulted in a significant decrease in glucose consumption and less incorporation of radio-labelled glucose in the ECM of COCs after FSH stimulation (Sutton-McDowall et al 2004), indicating a flux of glucose through the HBP. Furthermore, inhibition of HBP using the GFPT inhibitor 6-diazo-5-oxo-L-norleucine results in decreased cumulus expansion and glucose uptake by COCs (Gutnisky et al 2007). Hence, the increased rate of glucose consumption by COCs towards the end of IVM is to generate matrix via the HBP.…”