Cathepsin B activity is related to the quality of bovine cumulus oocyte complexes and its inhibition can improve their developmental competence

Abstract

Recently, the quantity of cathepsin transcripts in cumulus cells was found to be associated with low-developmental competence of bovine oocytes. In the present study, we investigated (1) the relation between cathepsin B activity and the quality of in vitro-matured cumulus-oocyte complexes (IVM COCs) and denuded oocytes and (2) the effect of a cathepsin B inhibitor (E-64) on embryo development and quality. The activity of cathepsin B was evaluated in IVM COCs and denuded oocytes. After maturation of COCs with or without E-64, followed by in vitro fertilization, zygotes were cultured for 8 days. Cleavage and blastocyst rates were evaluated on days 2 and 8, respectively. Quality of embryos was evaluated by differential staining of day 8 blastocysts. TUNEL staining was conducted on IVM COCs and blastocysts. Cathepsin B activity was clearly detected in the low-quality oocytes, and in the cumulus cells of both high- and low-quality oocytes. This latter activity was diminished by addition of E-64. The presence of E-64 during IVM also significantly increased both the blastocyst rate and the total cell number, and improved blastocyst quality associated with a significant increase of trophoectoderm cells. TUNEL staining revealed that inhibition of cathepsin B significantly decreased the number of apoptotic nuclei in both the cumulus cell layer of matured oocytes and blastocysts. These results indicate that cathepsin B activity can be a useful marker of oocyte quality. Furthermore, inhibition of cathepsin B greatly improves the developmental competence of bovine oocytes and increases the number of high-quality embryos.

Cathepsin B activity has a crucial role in the developmental competence of bovine cumulus–oocyte complexes exposed to heat shock during in vitro maturation

“…Bettegowda et al (2008) first reported that cumulus cells of low developmental competence oocytes showed higher expression of cathepsin B mRNA than those of high developmental competence oocytes (Bettegowda et al 2008). Moreover, our previous studies clearly showed that cathepsin B activity is inversely correlated with the quality of bovine COCs and embryos by the higher activity and protein expression of cathepsin B in poor-quality in vitro matured oocytes and embryos than in good-quality ones (Balboula et al 2010a(Balboula et al , 2010b. Furthermore, cathepsin B was found to impair the oocyte and embryo developmental competence by possible stimulation of the apoptotic pathway (Balboula et al 2010a(Balboula et al , 2010b.…”

“…Moreover, our previous studies clearly showed that cathepsin B activity is inversely correlated with the quality of bovine COCs and embryos by the higher activity and protein expression of cathepsin B in poor-quality in vitro matured oocytes and embryos than in good-quality ones (Balboula et al 2010a(Balboula et al , 2010b. Furthermore, cathepsin B was found to impair the oocyte and embryo developmental competence by possible stimulation of the apoptotic pathway (Balboula et al 2010a(Balboula et al , 2010b. In this study, the significant decrease in TUNEL apoptosis in heat-shocked bovine COCs after the addition of cathepsin B inhibitor (E-64) to the IVM medium clearly showed that cathepsin B has one of the key roles in inducing apoptosis during heat shock of bovine COCs.…”

“…Furthermore, cathepsin B increases in poor-quality bovine oocytes and embryos, which is associated with low developmental competence, than in good-quality ones. Supplementation of the IVM medium with cathepsin B inhibitor (E-64) improved the developmental competence of bovine COCs possibly by regulation of the apoptotic pathway (Bettegowda et al 2008, Balboula et al 2010a, 2010b. However, there is no available data about the possible role of cathepsin B during oocyte maturation and subsequent development under heat shock condition.…”

Cathepsin B inhibitor improves developmental competency and cryo-tolerance of in vitro ovine embryos

“…Furthermore, expression of cathepsin B is higher in poor quality bovine oocytes as compared to good-quality ones [22]. In this regard, Balboula et al showed that addition of 1 μM E-64 during in vitro maturation (IVM), improves quality of COCs and their developmental competency.…”

“…On the other hand, Min et al (2014) reported that treatment during IVC with E-64 (0.1 and 0.5 μM) significantly improves developmental rates without any noticeable effect on cleavage rate [24]. Unlike the former study which assessed role of cathepsin B inhibition during IVM, other research groups showed that addition of E-64 during in vitro culture (IVC) also improves rate and quality of derived blastocysts [7, 22, 24, 34]. Both these studies concluded that addition of E-64 to IVC medium has no effect on early cleavage rates.…”