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Effects of methodological and embryological parameters on survival and developmental potential of human embryos after cryopreservation

woensdag, 29 maart, 2006 - 17:00
Campus: Brussels Health Campus
Faculteit: Medicine and Pharmacy
auditorium P. Brouwer
Etienne Van Den Abbeel
doctoraatsverdediging

At the end of the 1980s it was clear that the results
of human embryo cryopreservation were
suboptimal, and that cryopreservation programmes
needed optimisation. What were the causes for the
low efficiency of human embryo cryopreservation?
Our research aimed to contribute in the elucidation
of this important question. More specifically we
aimed to develop a better understanding of the
causes of the damage sustained by human
embryos after cryopreservation and assess the
consequences of the damage for the viability of the
embryo. Therefore we studied methodological and
embryological parameters of human embryo
cryopreservation. We also used a mouse model to
gain more insight into the methodological
parameters.

Our research findings indicate that: (1) for a cohort
of cleavage-stage human embryos as they present
themselves into daily practice, controlled-rate
freezing with a long dimethylsulphoxide protocol is
better than with a short 1,2-propanediol protocol;
(2) rapid cooling by direct plunging into liquid
nitrogen is not an efficient procedure for human
embryo cryopreservation; (3) cellular loss in human
embryos after freezing and thawing impairs their
viability; (4) selective transfer of cryopreserved
human embryos with further cleavage after thawing
increases delivery and implantation rates and (5)
cryopreservation of sequentially cultured human
blastocysts does not improve substantially the
efficiency of human embryo cryopreservation
programmes despite a better selection of the
embryos to be frozen. The research findings of this
thesis contribute to a better understanding of
causes and consequences of damage to human
embryos after cryopreservation.