Growth of mouse pups derived from biopsied blastocysts

To test the hypothesis that removal of cells from the pre-embryo affects intrauterine growth, as reflected in birth weight or growth to weaning.

ICR Swiss albino and C57Bl/6 mice served as embryo donors to provide two strains of distinct coat colors. Alternate strains were assigned to control treatment or blastocyst biopsy of trophectoderm. Embryos from both treatments were transferred to a different uterine horn within each pseudopregnant recipient. A total of 412 embryos (206 controls and 206 biopsied blastocysts) were transferred to 26 recipients, which resulted in the birth of 122 pups.

There was no significant difference (P > .1) in birth weight or growth to weaning, defined as [[(weaning weight-birth weight)/birth weight)] x 100], between male and female pups. There was a significant difference (P < .01) between pups derived from ICR (birth weight 1.9 +/- 0.02 g; growth to weaning 544 +/- 14%; n = 72) versus C57Bl/6 (birth weight 1.43 +/- 0.03 g; growth to weaning 460 +/- 14%; n = 50) embryos. However, there was no significant difference (P > .1) in birth weight or growth to weaning for pups derived from biopsied embryos (birth weight 1.70 +/- 0.03 g; growth to weaning 502 +/- 14%; mean +/- standard error of the mean; n = 67) or control embryos (birth weight 1.71 +/- 0.05 g; growth to weaning 520 +/- 17%; n = 55).

These data support the null hypothesis that embryo biopsy does not result in reduced birth weight or altered subsequent growth to weaning.