Maintenance of the inner cell mass in XXXX blastocysts from fragmented embryos.

@entity1 @entity1949 @entity413 @entity2121
The degree of @entity1949 during early cleavage is universally used as an indicator of embryo quality during @entity1 in vitro fertilization treatment. @entity1949 has been associated with reduced blastocyst formation and implantation. We examined the relationship between early @entity1949 and subsequent allocation of cells to the trophectoderm and inner cell mass in the @entity1 blastocyst. We retrospectively analyzed data from 363 monospermic @entity1 embryos that exhibited varying degrees of @entity1949 on Day 2. Embryos were cultured from Day 2 to Day 6 in Earle balanced salt solution with 1 mM @entity413 and human serum albumin. Rates of development and blastocyst formation were measured. The number of cells in the trophectoderm and inner cell mass and the incidence of apoptosis were assessed following differential labeling with polynucleotide-specific fluorochromes. Increasing @entity1949 resulted in reduced blastocyst formation and lower blastocyst cell numbers. For minimal and moderate levels of @entity1949 , the reduction in cell numbers was confined largely to the trophectoderm and a steady number of inner cell mass cells was maintained. However, with extensive @entity1949 of more than 25%, cell numbers in both lineages were reduced in the few embryos that formed blastocysts. Apoptotic nuclei were present in both the trophectoderm and inner cell mass, with the lowest incidence in blastocysts that had developed from embryos with minor (5-10%) @entity1949 . @entity2121 , higher levels of apoptosis were seen in embryos of excellent morphology, suggesting a possible role in regulation of cell number.
