Observations on the in vitro formation, development and differentiation of trilaminar vesicles formed from enzymatically dispersed porcine blastocysts

The formation of trophoblastic vesicles and their use as a model for cell-to-cell interactions in the embryonic development of the mouse have been extensively studied both in vitro and in vivo . In this report, we describe the formation of trilaminar vesicles in vitro from enzymatically dispersed porcine blastocysts. Trilaminar vesicles were generated from single cell suspensions of enzymatically dispersed porcine blastocysts recovered 12 through 15 days post-breeding. Blastocysts at 10 and 11 days of development failed to form TV. No preference for self-aggregation was apparent as evident by the formation of vesicles containing cells from two different blastocysts origins. Two distinct morphological types of vesicles were formed: vesicles that displayed complete homogeneity in cell density and vesicles that had a small area of greater cell density resembling the embryonic disc. Some TV displayed localized areas of nucleated eosinophilic cells within the mesenchymal layer of the trilaminar membrane. In rare instances (2%) TV displayed contractility associated with a raised area of cells on the outer surface of the membrane. The cells comprising this contractile region were positive for Ca(++)-activated myofibriliary ATPase acitivity. Transfer of TV to the uterine horn of a gilt failed to delay a return to estrus. Transfer of TV to the uterine horn of pseudopregnant rabbits induced a localized inflammation and infiltration of leukocytes three days after transfer but no inflammation was evident at 9 or 16 days post-transfer.