Effects of various calcium transporters on mitochondrial Ca²⁺ changes and oocyte maturation

Abstract

Ca 2+ participates in many important cellular processes, but the underlying mechanisms are still poorly understood, especially during oocyte maturation. First, we confirmed that calcium in the culture medium was essential for oocyte maturation.Next, various inhibitors of Ca 2+ channels were applied to investigate their roles in mitochondrial Ca 2+ changes and oocyte maturation. Our results showed that Trmp7, Orai, T-type Ca 2+ channels and Na + /Ca 2+ exchanger complex (NCLX) were important for oocyte maturation. Trmp7 inhibition delayed germinal vesicle breakdown. Orai and NCLX inhibition significantly weakened the distribution of mitochondrial Ca 2+ around the nucleus compared to the Ctrl group. Interestingly, even T-type Ca 2+ channels-specific inhibitor Mibefradil blocked germinal vesicle breakdown; mitochondrial Ca 2+ surrounding the nucleus still was maintained at a high level without spindle formation. Two calcium transporter inhibitors, Thapsigargin and Ruthenium Red, which have been confirmed to inhibit oocyte activation, did not significantly affect oocyte maturation. Increasing the knowledge of calcium transport may provide a basis to build on for improving oocyte in vitro maturation in human assisted reproduction clinics. K E Y W O R D S assisted reproductive technology (ART), Ca 2+ transport, oocyte maturation | INTRODUCTIONCurrently, at least one in ten couples suffers from infertility, half of which is due to female problems (Chow et al., 2016). Oocyte quality in obese, diabetic and aging women is low, affecting the development of preimplantation embryos and also pregnancy

Reproductive Consequences of Electrolyte Disturbances in Domestic Animals

“…Maintaining the acid-base balance in body fluids is essential for maintaining whole-body homeostasis, and many deviations indicate disorders [ 113 ]. Female fertility disorders are correlated with electrolyte concentration [ 66 ]. The composition of the follicular fluid changes as the follicle grows.…”

“…In addition, oocyte mitochondria contain calcium channels that are important in regulating calcium influx and influx. Damage to the mitochondria in oocytes has been shown to reduce female fertility due to the lack of activation of oocytes [ 66 ].…”

“…This then leads to the activation of the anaphase-promoting complex (APC), which contributes to the termination of the meiosis [ 61 ]. In research conducted by Wang et al [ 66 ], the effect of various calcium transporters inhibitors, including erastin, and a T-type calcium channel inhibitor, on mouse oocyte were tested. It was established that the Ca 2+ in the Chatot-Ziomek-Bavister (CZB) culture medium is an essential factor for the maturation of oocytes.…”

“…It has been shown that calcium channels are important in this process, and their inhibitor blocks the disintegration of germinal vesicles. It was also shown that oocytes cultured on the CZB medium without calcium, died within two hours of the disintegration of the germinal vesicle, indicating the need for calcium in the environment [ 66 ]. Oocytes can fertilize after an activation process, in which sperm is involved.…”

NAT10 Maintains OGA mRNA Stability Through ac4C Modification in Regulating Oocyte Maturation

“…Among them, Trpc7 is involved in the regulation of calcium ion transmembrane transport and cytoplasmic calcium ion concentration, which are critical for oocyte maturation and activation (38,39). Rsph6a and Trpc7 were possible downstream genes modulated by NAT10-mediated ac4C on OGA mRNA, and their dysregulation could result in impaired oocyte maturation.…”