Da. Gook et al., INTRACYTOPLASMIC SPERM INJECTION AND EMBRYO DEVELOPMENT OF HUMAN OOCYTES CRYOPRESERVED USING 1,2-PROPANEDIOL, Human reproduction, 10(10), 1995, pp. 2637-2641
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-pro
panediol. The study was conducted at two centres. The normal inseminat
ion of cryopreserved oocytes was undertaken in one centre, and ICSI of
cryopreserved oocytes in the other. Both methods resulted in a 50% no
rmal fertilization rate. A low rate of abnormal fertilization was obse
rved in the inseminated group of oocytes (5%) compared with 21% for th
e ICSI oocytes; this was not significantly different. Embryo developme
nt 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 ooc
ytes, there was a significant decrease in the number of embryos cleavi
ng on day 3 (33%) compared with the development of ICSI oocytes, with
a subsequent gradual reduction over days 4 and 5 (22 and 11% respectiv
ely) resulting in one early blastocyst on day 7 (11%). In contrast, al
l 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%; da
y 7, 29%). By day 7, two of the blastocysts had started to hatch, resu
lting in a 66% hatching rate of blastocysts formed from ICSI of cryopr
eserved oocytes. This is the first study to show normal development to
the hatching blastocyst stage following ICSI of cryopreserved human o
ocytes.