Intracytoplasmic sperm injection and embryo development of human oocytes cryopreserved using 1,2-propanediol

Abstract

This study reports the subsequent embryo development of cryopreserved mature human oocytes following insemination or intracytoplasmic sperm injection (ICSI). Metaphase II oocytes were cryopreserved using a slow freezing-rapid thawing procedure employing the cryoprotectant 1,2-propanediol. The study was conducted at two centres. The normal insemination of cryopreserved oocytes was undertaken in one centre, and ICSI of cryopreserved oocytes in the other. Both methods resulted in a 50% normal fertilization rate. A low rate of abnormal fertilization was observed in the inseminated group of oocytes (5%) compared with 21% for the ICSI oocytes; this was not significantly different. Embryo development was assessed daily for 7 days. All normal fertilized cryopreserved oocytes in both groups cleaved on day 2, with a similar appearance to in-vitro fertilization and ICSI embryos. In the normal inseminated oocytes, there was a significant decrease in the number of embryos cleaving on day 3 (33%) compared with the development of ICSI oocytes, with a subsequent gradual reduction over days 4 and 5 (22 and 11% respectively) resulting in one early blastocyst on day 7 (11%). In contrast, all ICSI-generated embryos continued to cleave on day 3, with a gradual reduction over subsequent days (day 4, 86%; day 5, 57%; day 6, 43%; day 7, 29%). By day 7, two of the blastocysts had started to hatch, resulting in a 66% hatching rate of blastocysts formed from ICSI of cryopreserved oocytes. This is the first study to show normal development to the hatching blastocyst stage following ICSI of cryopreserved human oocytes.

Qualitative and morphometric analysis of the ultrastructure of human oocytes cryopreserved by two alternative slow cooling protocols

“…By using epifluorescence microscopy, Gook et al [37] showed that the staining specific for CG was not decreased in cryopreserved material in comparison to fresh controls. They also demonstrated that that fertilization could be achieved for frozen-thawed oocytes through standard IVF [28]. More recently, the successful use of standard IVF has been reported by other authors [38].…”

“…In fact, after approximately 20 years of efforts in basic and clinical research [1,2,4,14,15,[27][28][29][30][31], oocyte cryopreservation has been described to achieve high standards of clinical efficiency [3,6,7,32]. Objective clinical evidence is emerging at a relatively slow pace, because IVF centres that routinely cryopreserve oocytes are still few and, consequently, current data are too small or dishomogeneous to draw definitive conclusions.…”

Live birth following transfer of a cryopreserved embryo generated from a cryopreserved oocyte and a cryopreserved sperm: Case report

“…The resurgence of interest in human oocyte cryopreservation as a consequence of a number of reports suggesting that it may be a safe option in appropriate circumstances [1][2][3][4] has led to its clinical application and reports of a number of live births [5][6][7][8][9][10]. Although this approach has been adopted as an adjunct to routine IVF practice in Italy, this is predominantly a consequence of legal developments which resulted in the prohibition of the alternative, and more widepread, option of embryo cryopreservation.…”

Oocyte cryopreservation: is it time to remove its experimental label?

“…Early concerns regarding damage to the meiotic spindle [3], loss of cortical granules leading to lowered fertilization rates [4,5] and the low success rates of oocyte freezing/thawing as compared to the relative success of embryo cryopreservation caused a wavering of interest until the 1990s. Then, a series of studies indicating that reasonable oocyte thaw survival [6], fertilization [7,8], embryos with normal karyotype [8][9][10], and viable blastocyst development [11] could be achieved led to renewed interest in OC technology. Reports demonstrating live births following application of OC appeared soon after [12,13].…”

“…In addition, although depolymerization of the oocyte's meiotic spindle is known to occur, a number of studies have now shown that the spindle reforms in the majority of oocytes after thawing [24][25][26][27][28][29]. The advent of ICSI for insemination has overcome any concern regarding potential premature cortical granule reaction [11]. Work from several Italian groups (where oocyte cryopreservation has often been used because of legal restrictions on embryo cryopreservation) has been instrumental in establishing OC as a clinically valid procedure [30,31].…”