Replacement of inner cell mass in mouse

The intra- or inter-strain reconstituted blastocysts were produced by replacing the inner cell mass of Kunming mouse blastocysts with that of Kunming or C57BL/6 mouse strain blastocysts. A total of 192 intra-strain reconstituted blastocysts were transferred into 17 pseudopregnant Kunming mice, and 2 reconstituted embryos were developed into term: while 115 inter-strain reconstituted blastocysts were produced, analysis of the reconstituted blastocysts showed that the morphology and cytoskeleton srtucture of the blastocysts were not different from those of normal blastocysts, however, no viable offspring was obtained after embryo transfer for these inter-strain reconstituted blastocysts. The results demonstrated that the intra-strain reconstituted blastocysts could normally develop into term, whereas the inter-strain reconstituted blastocysts possessed less developmental potential as the intra-strain reconstituted blastocysts. This study may give light to solve the problem of low implantation rate and placenta abnormality in mammal cloning.