In vitro production of ruminant embryos has become
routine and is increasingly available as a commercial service to dairy, meat
and wool producers. However, the efficiency of producing viable embryos and
the development of such embryos after transfer to recipients are perceived to
be inferior to that which occurs in vivo. The present
review outlines the biochemical and morphological similarities and differences
between embryos produced In vitro and those produced in
vivo. Some measures of metabolism are not markedly different between
In vitro- and in vivo-derived
blastocysts. However, at a cellular and subcellular level, differences in
metabolism, morphology and ultrastructure have been described, as has
susceptibility to manipulation and cryopreservation. Most importantly are the
differences in lambing and calving rates and the reports of abnormal fetal
development from embryos produced In vitro. These latter
observations are of major concern, as they suggest that the
In vitro environment may affect subsequent developmental
physiology. At the extreme, these effects may not be expressed until adult
life. Further efforts to improve the efficiency of
In vitro embryo production must be accompanied by a
commitment to assess the long-term consequences of these procedures.
Extra keyword: development.
Hematopoietic stem cell development requires transient Wnt/β-catenin activity