Zinc supplementation alleviates endoplasmic reticulum stress during porcine oocyte in vitro maturation by upregulating zinc transporters

Abstract

Endoplasmic reticulum (ER) stress is a major contributor to embryonic development failure. Mammalian oocytes have a high risk of exposure to cellular stress during in vitro embryo production. We investigated the effects of zinc supplementation during in vitro maturation under ER stress. We evaluated cumulus expansion, embryonic development derived by parthenogenetic activation, reactive oxygen species, protein expression of X‐box binding protein 1 (XBP1), and expression of genes related to ER stress. Supplementation with 1 μg/ml zinc significantly increased the nuclear maturation of oocytes, cleavage and blastocyst formation rates, and total blastocyst cell number (p < .05). Under ER stress, zinc significantly reduced protein expression of XBP1, and increased cleavage and blastocyst rates (p < .05). Concomitantly, zinc supplementation upregulated the expression of zinc transporters (SLC39A14 and SLC39A10), PTGS2, and downregulated ER stress‐related genes (sXBP1, uXBP1, ATF4, and PTPN1/PTP1B), and caspase 3. These results suggest that zinc supplementation alleviates ER stress by providing essential metal‐ion transporters for oocyte maturation and subsequent embryonic development.

MicroRNA-210 Regulates Endoplasmic Reticulum Stress and Apoptosis in Porcine Embryos

“…XBP1 is commonly used as a marker of ER stress, both in vivo and in vitro [ 49 , 50 ]. In line with the present study, zinc treatment during IVM reported significantly reduced expression levels of XBP1 in matured porcine oocytes; improved blastocyst formation rates; and significantly decreased gene expression of Caspase 3 and ER stress-related genes such as XBP1 , binding protein ( BiP ), PTPN1 , and ATF4 [ 51 ]. The increase of XBP1 is suggestive of an activation of the ER stress response through the Inositol-requiring transmembrane kinase endoribonuclease-1α ( IRE1α ), one of the UPR branches.…”

“…In cases of severe ER stress, apoptotic cell death was induced by phosphorylated e IF2α , which further triggers ATF4 , which induces apoptosis [ 60 ]. Our previous study showed that a reduction of ER stress-related genes and Caspase 3 resulted in improved in vitro embryo development [ 51 ]. These results revealed that miR-210 is involved in alleviating apoptosis by decreasing ATF4 and Caspase 3 .…”

Adiponectin Improves In Vitro Development of Cloned Porcine Embryos by Reducing Endoplasmic Reticulum Stress and Apoptosis

“…Ovaries were obtained from Landrace prepubertal gilts at a local pig abattoir and placed at 32–37 °C in 0.9% normal saline solution. Oocyte collection and IVM were performed as previously explained [ 33 , 35 , 42 , 43 ]. In brief, Oocytes were collected from follicles (3–6 mm) utilizing a 10-mL syringe.…”

“…In brief, oocytes were denuded with 0.1% hyaluronidase in TALP-HEPES medium and stained with 5 μg/mL Hoechst-33342 in TALP-HEPES for 10 min. Oocytes with dark homogenous ooplasm with polar body were selected for SNCT [ 33 ]. Furthermore, the first polar body and elemental Metaphase II (MII) chromosome were enucleated using an aspiration glass pipette.…”

“…Due to the low capacity of pig embryo development from the cleavage stage until the blastocyst stage compared to its in vivo counterparts [ 31 ], researchers have been attempting to improve these techniques and subsequently improve the in vitro production of embryos [ 32 ]. Recent studies on the establishment of chemically defined media, utilization of the ‘zona hardening’ technique [ 32 ], and improvement of maturation rates [ 33 , 34 ] have proved successful. Moreover, various treatments to improve embryo development, such as zebularine [ 35 ], adiponectin [ 21 ], quisinostat [ 36 ], suberoylanilide hydroxamic acid [ 37 ], LAQ824 [ 38 ], melatonin [ 29 ], and spermine [ 39 ] have been reported.…”