Intraspecific blastocyst reconstitution in mice using giant trophectodermal vesicles produced by multiple embryo aggregation

Giant trophectodermal (TE) vesicles, produced by aggregating multiple embryos, were evaluated as a means of enhancing the viability of reconstituted murine blastocysts. Previous studies have indicated that the development of chimeric conceptuses produced by multiple embryo aggregation is impaired, thus the initial objective here was to examine how this is affected by 1) differences in developmental rates of individual embryos comprising the aggregates, 2) lengths of in vitro culture, and 3) incompatibilities between maternal hosts and chimeric fetal allografts. The results indicate that the viability of aggregates was influenced by embryo genotype and length of in vitro culture. The average number of B6D2-F1 x BL/6 offspring resulting from aggregates cultured for 0.7 day was not significantly different (p greater than 0.05) from that obtained from either embryo singletons cultured for 0.7 and 1.7 days (2.9 +/- 0.3 and 3.9 +/- 0.4, respectively) or from nonmanipulated controls (3.2 +/- 0.2 and 4.3 +/- 0.3, respectively). Blastocyst reconstitution studies were then conducted using giant TE vesicles from B6D2-F1 x BL/6 mice and inner cell masses from C3H mice. The average number of C3H offspring produced (2.7 +/- 0.1) was not significantly different (p greater than 0.05) from that of B6D2-F1 x BL/6 embryo aggregates (3.2 +/- 0.6) or of nonmanipulated controls (4.3 +/- 0.3). The results demonstrate that giant TE vesicles can be effectively used for intraspecific blastocyst reconstitution in mice.