Developmental clock compromises human twin model created by embryo splitting.
OBJECTIVE
Is the quality of the human embryos generated by twinning in vitro comparable to the quality of the embryos created by fertilization?


CONCLUSIONS
Our data suggest that the human twin embryos created in vitro are unsuitable not only for clinical use but also for research purposes.


BACKGROUND
Pregnancy from in vitro generated monozygotic twins by embryo splitting or twinning leads to live birth of healthy animals. Similar strategies, however, have been less successful in primates. Recent reports suggest that the splitting of human embryos might result in viable, morphologically adequate blastocysts, although the qualitative analyses of the embryos created in such a way have been very limited.


METHODS
This study was a comparative analysis of embryos generated by twinning in vitro and the embryos created by in vitro fertilization.


METHODS
We analysed morphokinetics and developmental competence of 176 twin embryos created by splitting of 88 human embryos from either early (2-5 blastomeres, n = 43) or late (6-10 blastomeres, n = 45) cleavage stages. We compared the data with morphometrics of embryos created by in vitro fertilization and resulting in pregnancy and live birth upon single blastocyst transfer (n = 42).


RESULTS
The morphokinetic data suggested that the human preimplantation development is subjected to a strict temporal control. Due to a 'developmental clock', the size of twin embryos was proportionate to the number of cells used for their creation. Furthermore, the first fate decision was somewhat delayed; the inner cell mass (ICM) became distinguishable later in the twin than in the normal blastocysts obtained through fertilization. If an ICM was present at all, it was small and of poor quality. The majority of the cells in the twin embryos expressed ICM and trophectoderm markers simultaneously.


CONCLUSIONS
We created monozygotic twins by blastomere separation from cleavage stage embryos. Embryo twinning by blastocyst bisection may circumvent limitations set by the developmental clock.


CONCLUSIONS
Taken together, our data suggest that the human twin embryos created in vitro are unsuitable not only for clinical use but also for research purposes.
Division of Women's Health, Faculty of Life Sciences and Medicine, King's College London and Assisted Conception Unit, Guys' Hospital, London SE1 9RT, UK.
Laila
L
Noli
Division of Women's Health, Faculty of Life Sciences and Medicine, King's College London and Assisted Conception Unit, Guys' Hospital, London SE1 9RT, UK.
Yaser
Y
Dajani
GENERA, Centre for Reproductive Medicine, Clinica Valle Giulia, Rome 00197, Italy GENETYX, Molecular Genetics Laboratory, Via Fermi 1, Marostica 36063, Italy.
Antonio
A
Capalbo
Division of Women's Health, Faculty of Life Sciences and Medicine, King's College London and Assisted Conception Unit, Guys' Hospital, London SE1 9RT, UK.
Jean
J
Bvumbe
GENERA, Centre for Reproductive Medicine, Clinica Valle Giulia, Rome 00197, Italy GENETYX, Molecular Genetics Laboratory, Via Fermi 1, Marostica 36063, Italy.
Laura
L
Rienzi
GENERA, Centre for Reproductive Medicine, Clinica Valle Giulia, Rome 00197, Italy GENETYX, Molecular Genetics Laboratory, Via Fermi 1, Marostica 36063, Italy.
Filippo Maria
FM
Ubaldi
Genetics Laboratories, Guy's Hospital, London, UK.
Caroline
C
Ogilvie
Division of Women's Health, Faculty of Life Sciences and Medicine, King's College London and Assisted Conception Unit, Guys' Hospital, London SE1 9RT, UK.
Yacoub
Y
Khalaf
Division of Women's Health, Faculty of Life Sciences and Medicine, King's College London and Assisted Conception Unit, Guys' Hospital, London SE1 9RT, UK dusko.ilic@kcl.ac.uk.
Dusko
D
Ilic
D001755:Blastocyst / Q000166:cytology*; D001757:Blastomeres / Q000166:cytology*; D004624:Embryo Transfer / Q000379:methods*; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D014430:Twins, Monozygotic
blastocyst; cleavage stage human embryos; developmental clock; embryo splitting; monozygotic twins; morphokinetics