Caldwell, Matthew, 2018-2019

Matthew Caldwell
Matthew
Caldwell

"Deriving Human Trophoblast Stem Cells from Human Embryonic Cells and by the Process of Forward Programing"

Host Mentor: Roger Pendersen, Ph.D.
Institute for Stem Cell Biology and Regenerative Medicine
Stanford University

The study of human placental development has proven difficult, largely due to the inability of researchers to derive self-renewing trophoblast stem cells that retain the full differentiative potential of native placental trophoblast. Current studies are mostly done through mouse models or the culture of primary trophoblast cells. These methods of studying placental development are not ideal for understanding human placental development due to the differences between humans and mice and the limited proliferative and differentiative potential of available human primary trophoblast cells. Recently, a protocol for the establishment of human trophoblast stem cells has been developed by a research group in Japan that studies placental development. However, their protocol requires placental tissues samples that are difficult to obtain. Our goal is to show that the overexpression of trophoblast specific transcription factors in human pluripotent stem cells will induce efficient differentiation into trophoblast stem cells. To identify these transcription factors, we analyzed publicly available cytotrophoblast RNA sequencing data sets and H1 human embryonic stem cell RNA sequencing data sets. Using these data sets, we looked at the differential gene expression of the cytotrophoblast data sets compared with the embryonic stem cell data set to identify what genes are highly expressed in cytotrophoblast versus embryonic stem cells, looking specifically for genes coding for transcription factors. From this list, we selected transcription factor candidates that were confirmed in the literature to play an essential role in trophoblast development. We placed the candidate genes into lentiviral transgenes for over-expression in human pluripotent stem cells. This approach using over-expression of lineage specific transcription factors in human pluripotent stem cells to drive differentiation to target cell types is known as forward programming. We hypothesize that forward programming will circumvent the current limitations to inducing differentiation of human pluripotent stem cells into trophoblast cells using cytokines and will avoid ethical and practical difficulties of obtaining primary trophoblast stem cells from placental tissues. In this way, we expect to generate a system that provides researchers with a steady supply of trophoblast stem cells, which are vital for studying the earliest stages of human development.