Molecular Signals Stoking Stem Cell Development Identified
Scientists explain that stem cells work by repairing damaged cells, at times renewing normal ones. However, not much is known about where they originate from or how the embryo develops. A team of scientists at The Rockefeller University have found a method to stimulate developing cells so that they can become stem cells. This would help to clarify the communication between cells, even as it illuminates the potential treatments for skin cancer.
"While adult stem cells are increasingly well-characterized, we know little about their origins. Here, we show that in the skin, stem cell progenitors of the hair follicle are specified as soon as the cells within the single-layered embryonic epidermis begin to divide downward to form an embryonic hair bud," Elaine Fuchs, who co-authored the research, said in a press release. "This timing was much earlier than previously thought, and gives us new insights into the establishment of these very special cells."
Earlier, scientists found that stem cells could be "instructed" to remain so, or change into a different kind of cell type. However, the origin of these instructive cells remains unknown. With the help of a mouse hair follicle, Fuchs and her team probed the cell divisions in the process of formation, and found that for every division, one daughter cell stayed in the same position, even as the others shifted to a new layer, which clarified that stem cells might be existing before even the "instructive cells".
The Fuchs team examined the two daughter cells in separate situations to cross-check what signals controlled their fate. The environments of the daughter cells showed low levels of WNT signalling in embryonic development, but the environment in which they stayed on exhibited high levels of WNT signaling.
The WNT levels tend to impact the response of cells to SHH signalling. Hence, in just low-WNT environments, cells respond to SHH signaling, stoking the cells to turn into stem cells.
"These cells must leave home, they must leave the environment with high WNT signaling, to become stem cells," said Tamara Ouspenskaia, first author of the study. "We observed that SHH, which actually comes from the cells with high WNT signaling, is essential in helping the cells leave. So in order for this escapee cell to become a stem cell, it needs to receive an SHH signal from its sister cell at home telling it 'you're the stem cell.'"
The study was published in the Jan.14,2016 issue of Cell.