President's Distinguished Lecture II

Janet Rossant, CC, PhD, FRS, FRSC
The Hospital for Sick Children and Department of Medical Genetics
University of Toronto
Toronto, ON Canada

Saturday, March 14
8:00 a.m. - 9:00 a.m.

President's Distinguished Lecture II: Modeling Early Placental Development – Can Pluripotent Stem Cells Do the Trick?

In vitro model systems to study placental development have focused on the use of either primary tissue or stably established trophoblast stem cell lines. In the mouse, we have worked with trophoblast stem cells derived from either the blastocyst or the early postimplantation stages to study the molecular underpinning of the establishment of the early maternal-trophoblast interface. Others have used trophoblast stem cells combined with embryonic stem cells to generate models of the key interactions that pattern the pre- and early postimplantation embryo. Recent derivation of human trophoblast stem cells has opened up new vistas of exploring similar questions relevant to the critical early phases of implantation and villus formation in humans.

It has been suggested that extended potential embryonic stem cells may be a key resource to study all these events because they have been reported to be able to generate trophoblast as well as embryonic lineages in vitro. We have explored these claims and find that, while such cells show some molecular properties reminiscent of trophoblast, they do not make functional trophoblast contributions to chimeras. Continued exploration of embryo/placental models in mouse or human should make use of bona fide trophoblast stem cells wherever possible.

The ethical and regulatory implications of generating human embryo models with both trophoblast and embryonic components needs to be considered but the scientific value of such systems is increasingly clear.