New stem cell type expands R&D, regenerative medicine possibilities

Human embryonic stem cells
While embryonic stem cells (pictured) and induced pluripotent stem cells are able to differentiate into many types of cells, they do not have the ability to become any type of cell.

Embryonic stem stem cells can develop into many different types of cell and could one day lead to regenerative treatments for various diseases. But they have limitations—taken from a fertilized egg about five days old, these stem cells have lost the ability to develop into all cell types.

What if we could take stem cells from an earlier stage of embryonic development? Scientists from the Wellcome Trust Sanger Institute have done just that.

"The earliest cell is like a blank piece of paper, in theory it should have the greatest development potential,” said Pentao Liu, an affiliate faculty member of the Wellcome Trust-MRC Stem Cell Institute, University of Cambridge, in a statement.

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The Wellcome team, led by Liu, developed a new method of culturing cells from the earliest stage of development, when the fertilized egg has divided into four or eight cells. At this point, it is believed to still be "totipotent," or able to differentiate into any cell type. In contrast, embryonic stem cells are derived from blastocysts, which are made up of about 100 cells.

The researchers cultured the stem cells in conditions that blocked key development signals and pathways. These stem cells, dubbed Expanded Potential Stem Cells (EPSCs), maintained totipotency. The team was also able to take embryonic stem cells and induced pluripotent stem cells and reprogram them to become EPSCs—essentially turning back the clock on development. The findings appear in Nature.

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Regenerative medicine holds promise in a number of different areas, including growing new skin from a burn patient’s own cells instead of using skin grafts. A team from the Salk Institute created embryos with both pig and human DNA, with the eventual goal of growing transplantable tissue and organs. While the scientists did not allow the hybrid embryos to fully develop, their invention could be useful in drug development and regenerative medicine.

The ability of Wellcome Trust's EPSCs to develop into any kind of cell not only expands research opportunities, but it also opens the door to potential regenerative treatments.

"EPSCs provide a platform to study early embryo cells in detail at the molecular level to understand development, not only in mouse, but ultimately in future in humans,” said first author Jian Yang of the Wellcome Trust Sanger Institute. “This new method of producing stem cells could be enormously helpful for studying development, more efficiently generating functional human cells, and researching treatments for pregnancy problems such as pre-eclampsia and miscarriages."