Fertilization of human oocytes following cryopreservation; normal karyotypes and absence of stray chromosomes

Abstract

Survival following cryopreservation of fresh and aged human oocytes by the propanediol (PROH) procedure was observed in 51 and 73% of oocytes respectively, immediately after thawing. This survival was reduced in both types of oocytes at the time of insemination (3-4 h) to 41% in fresh and 61% in aged oocytes. Insemination of the cryopreserved and control oocytes with spermatozoa from one donor resulted in total fertilization rates similar to our in-vitro fertilization (IVF) rate for non-male factor patients. The normal fertilization rate for fresh cryopreserved oocytes was slightly lower (46%) than the rate for IVF oocytes (59%) (P < 0.05), while the abnormal fertilization rates were not significantly different (16 and 15% respectively). In contrast, a reduction in the normal fertilization rate was observed for the aged cryopreserved oocytes (13%) compared to the IVF rate (P < 0.001). Associated with this was an increase in the abnormal fertilization rate for the aged cryopreserved oocytes, which was significantly higher (47%) than the IVF rate (15%) (P < 0.001). Significant differences in the total and normal fertilization rates were observed between cryopreserved oocytes obtained from cohorts with < or = 27 (total: 84%, normal: 68%) and > 27 oocytes (total: 55%, normal: 33%) (P < 0.05). Fertilized oocytes and oocytes with abnormal or absent spindles were examined for chromosomal loss and no stray chromosomes were observed in any of these cryopreserved oocytes (n = 137). In the cryopreserved oocytes which had undergone normal fertilization, four scorable karyotypes were achieved and in all of these two sets of 23 chromosomes were observed.

High Survival Rate of Bovine Oocytes Matured In Vitro Following Vitrification

“…It has been reported that there is no increase in the rates of aneuploidy or abnormal karyotype in onecell rabbit embryos [64] and mature mouse or human oocytes [65,66] when they were treated with PROH as a cryoprotectant. However, PROH is not effective for cryopreservation of mouse and human oocytes when a slow freezing procedure is u s e d b e c a u s e o f a h i g h i n c i d e n c e o f parthenogenetic activation found after freezingthawing with 1.5 M of PROH [60,67,68].…”

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].…”