Cryopreservation of human and rabbit oocytes and one-cell embryos: a comparison of DMSO and propanediol.
The aim of this study was to improve the cryopreservation of human oocytes and pronuclear embryos. One-step and multiple-step addition of dimethyl sulphoxide (DMSO) and 1,2-propanediol (PROH) and three different freezing protocols with intermediate temperatures of -35, -70 and -110 degrees C were investigated. This work was performed using rabbit oocytes as well as human oocytes and one-cell embryos from the routine IVF programme. Also, human polyploid pronucleate oocytes were used in controlled prospective studies of morphological intactness and development in vitro. Rabbit oocytes survived best (113/126) when PROH was added in one step and controlled freezing stopped at -110 degrees C. But the development was better (141/187) if DMSO was added in multiple steps and the oocytes were cooled to -70 degrees C before being plunged into liquid nitrogen. The mode of addition of the cryoprotectant influenced development only if slow freezing was stopped at -35 degrees C (51 versus 34%). Using PROH, the development after thawing was also better if cooling was stopped at -35 degrees C (51 versus 37%) and DMSO was superior to PROH when the oocytes were cooled slowly to -110 degrees C (66 versus 37%). In the human, significantly more pronucleated than unfertilized oocytes developed after freezing (92 versus 50%). The best results were achieved with pronuclear embryos using 1.5 M PROH and cooling to -110 degrees C, when 91.7% of the surviving oocytes developed further. This is a marked improvement of the development rate and comparable to embryo freezing.
Siebzehnruebl
E R
ER
Department of Obstetrics and Gynaecology, University of Erlangen, FRG.
Todorow
S
S
van Uem
J
J
Koch
R
R
Wildt
L
L
Lang
N
N
D000818:Animals; D003451:Cryoprotective Agents; D004121:Dimethyl Sulfoxide; D004622:Embryo, Mammalian; D005615:Freezing; D006801:Humans; D009865:Oocytes; D011309:Preservation, Biological; D019946:Propylene Glycol; D011409:Propylene Glycols; D011817:Rabbits
D003451:Cryoprotective Agents; D011409:Propylene Glycols; D019946:Propylene Glycol; D004121:Dimethyl Sulfoxide