Analyses of apoptosis and DNA damage in bovine cumulus cells afterin vitromaturation with different copper concentrations: consequences on early embryo development

Abstract

The aim of this study was to investigate the influence of copper (Cu) during in vitro maturation (IVM) on apoptosis and DNA integrity of cumulus cells (CC); and oocyte viability. Also, the role of CC in the transport of Cu during IVM was evaluated on oocyte developmental capacity. Damage of DNA was higher in CC matured without Cu (0 µg/dl Cu, P < 0.01) with respect to cells treated with Cu for cumulus-oocyte complexes (COCs) exposed to 0, 20, 40, or 60 µg/dl Cu). The percentage of apoptotic cells was higher in CC matured without Cu than in CC matured with Cu. Cumulus expansion and viability of CC did not show differences in COC treated with 0, 20, 40, or 60 µg/dl Cu during IVM. After in vitro fertilization (IVF), cleavage rates were higher in COC and DO + CC (denuded oocytes + CC) with or without Cu than in DO. Independently of CC presence (COC, DO + CC or DO) the blastocyst rates were higher when 60 µg/dl Cu was added to IVM medium compared to medium alone. These results indicate that Cu supplementation to IVM medium: (i) decreased DNA damage and apoptosis in CC; (ii) did not modify oocyte viability and cumulus expansion; and (iii) improved subsequent embryo development up to blastocyst stage regardless of CC presence during IVM.

Impacts of Bovine Trace Mineral Supplementation on Maternal and Offspring Production and Health

“…Copper also appears to play a role in female gamete viability, as several reports on its effects on oocyte and embryo development exist. In vitro work found Cu supplementation had no effect on bovine oocyte maturation [24], however, cumulus cell apoptosis was reduced in bovine cumulus-oocyte complexes exposed to Cu during the maturation stage of development [25]. Moreover, Picco and colleagues [26] reported that Cu supplementation during in vitro maturation (IVM) decreased cumulus cell DNA damage.…”

High copper concentrations produce genotoxicity and cytotoxicity in bovine cumulus cells

“…Even though, we previously demonstrated that Badequate( 60 μg/dL) Cu concentration added to IVM medium decreased DNA damage and apoptosis in bovine cumulus cells (Rosa et al 2016), we observed an increase of necrotic cell percentages when Cu was added at high concentrations to the culture medium in concordance with other authors (Aston et al 2000;Krumschnabel et al 2005). Cu excess might interact in a non-specific manner with several macromolecules either by modifying their conformation or by causing sitespecific damage that result in a disruption of vital cellular processes which further lead to apoptotic and necrotic cell death (Didenko et al 2003;Krumschnabel et al 2005;Rana 2008;Cao et al 2012;Kuku et al 2016;Philipp et al 2016).…”

Oocyte Selection for in Vitro Embryo Production in Livestock Species: Non-Invasive Approaches for the New Challenges of Oocyte Competence

“…Although the expansion of cumulus cells has been described as the basis for oocyte maturation [71] and early reports supported the idea that quantity and quality of the expanded cumulus mass were correlated with developmental capacity [72], its usefulness as an indicator of developmental potential in bovine seems to be modest [73]. For instance, studies by Anchordoquy et al [74], Dovolou et al [75] and Rosa et al [76] reported that, under different experimental conditions, the cumulus expansion index was not indicative of blastocyst yield or quality. Similarly, another study indicated that inhibition of cumulus expansion by enzymatic hyaluronidase degradation did not affect cleavage or blastocyst development [77].…”