Year 2

During the past reporting period, we have treated two different lines of human embryonic stem cells with a growth factor, BMP4, and differentiated them (i.e., made them change their character) down the pathway towards becoming a precursor of the human placenta. We have found that these cells initially lose their stem cell characteristics and change their appearance from stem cells to trophoblast (placental) cells. In addition, we conducted a study over 12 days in which these cells exhibited these changes, and we looked at not only their appearance, but also all the genes that they express, using whole genome array technology. We found that they lose their stemness and acquire genes important for commitment to be placental cells. Furthermore, we investigated the cellular pathways that are involved, and these are very fundamental for differentiating these cells to the placental phenotype (i.e., appearance and gene signature). Also, we are investigating whether another cell line has similar characteristics, and we are comparing all the genes expressed in the trophoectomer shell surrounding a human embryo (blastocyst) with the gene profiles in the trophoblast cells derived from human embryonic stem cells. Furthermore, we have studied the effects of products secreted by these cells on the first cells that the blastocyst encounters when it attaches to the mother’s lining of the uterus during the process of implantation. We have used a human endometrial epithelial cell line, to see if there are any effects, since we do not know if the levels of secreted products can indeed result in a response from the mother’s uterus. We found an interesting array of factors that are regulated, and we are now poised to study human endometrial epithelial cells (not a cell line), since we know that a response occurs in these pilot studies with a cell line. The ultimate goal is to define proteins secreted by human blastocysts and predict which blastocysts have a profile that is consistent with an ability to attach to the mother’s uterus and then begin the process of implantation.