Factors Affecting Cryopreservation of Porcine Oocytes

Effects of two combinations of cryoprotectants on the in vitro developmental capacity of vitrified immature porcine oocytes

“…Although the reasons for these differences are unclear, the results suggest that the higher permeability of PG better protects oocytes compared with DMSO in terms of fertilization efficiency. As in previous studies [10,13,46], our results indicate that regardless of CPA combination, vitrified oocytes exhibit a reduced ability to develop to the blastocyst stage after IVF compared with controls.…”

“…The meiotic stage highly influences the ability of porcine oocytes to be vitrified, and metaphase II (MII) oocytes are traditionally preferred for vitrification. Although the survival of oocytes matured in vitro after vitrification is relatively high, their fertilization and developmental competence are seriously compromised [9,10]. Previous investigations have revealed a failure in male pronuclear formation in vitrified MII oocytes after fertilization [11].…”

“…In addition, vitrification at this stage may avoid spindle damage [10], which is one of the most common alterations observed in vitrified MII oocytes [12]. Although live offspring have been obtained from vitrified immature oocytes [13], the total yield of blastocyst stage embryos remains very low.…”

Comparison of cytoskeletal integrity, fertilization and developmental competence of oocytes vitrified before or after in vitro maturation in a porcine model

“…Cytoskeletal elements are known to regulate several events during fertilization in mammalian oocytes such as sperm penetration and 2PB extrusion [25,26]. In accordance, high frequencies of fertilization anomalies have been recorded in porcine oocytes vitrified at the MII stage [21,24]. In this respect, cryopreservation of immature oocytes followed by in vitro maturation (IVM) might be advantageous.…”

“…There has been some debate regarding the optimum nuclear stage for cryopreservation of mammalian oocytes. In pigs, it has been confirmed that mature (MII stage) oocytes have higher survival ability during cryopreservation than immature oocytes [21]. On the other hand, cryopreservation of matured mammalian oocytes has been associated with damage of the meiotic spindle and actin microfilaments [2,3,11,19], causing the failure of second polar body (2PB) extrusion and the possible generation of embryos with abnormal numbers of chromosomes [2,6,7].…”