This content is adapted from an article on www.sciencecodex.com, December 7, 2015.
To maintain healthy skin and to heal wounds requires an exact number of cells to divide in order to replace those shed from the skin surface. While too many cell divisions can cause cancer, too few can lead to ulcers. A short burst of cell production to fill the gap in the skin is needed for wound healing.
Recent research shows all dividing cells have the potential to maintain and heal skin, which challenges the idea of how only rare stem cells matter, thus creating what is known as "dice games."
The techniques of cells
Research showed watching human skin cells dividing in real time proved how the cells repair in two forms: maintenance and wounds.
- Maintenance technique: Between production and shedding, the odds are balanced with a half-and-half chance of a daughter cell dividing or stopping division and transferring to the skin’s surface, which keeps the skin balanced.
- Wound technique: On the other hand, cells will temporarily switch into repair mode if located next to a wound. The cells can then produce dividing cells up to nine times more to repair the injury quicker.
"This research demonstrates that dividing human skin cells can switch their behavior between these two modes of maintenance or repair, challenging the longstanding view that skin renewal and healing relies on a special population of stem cells," said Phil Jones, Ph.D., senior group leader at the Wellcome Trust Sanger Institute and MRC Cancer Unit, University of Cambridge.
Switching methods
Researchers took live movies of more than 3,000 dividing human skin cells to examine skin turnover. The results showed, while in repair mode, single cells expanded exponentially until they produced multi-layered sheets of cells. Afterward, the behavior switched to maintenance mode.
"By scratching sheets of cells in the balanced mode and observing cells next to the scrape, we saw that they changed into wound-healing mode until the scratch was closed again," said Joanna Fowler, Ph.D., an author of the paper from the Sanger Institute. "The cells could switch backward and forward between the two states as required, proving that the behaviors were reversible."
Significance of cells
Sheets of skin can be grown from skin patches in a laboratory and can save lives of patients with serious burns or ulcers, which if not treated can become fatal.
The cells switch from maintenance to wound behavior based on whether they are surrounded by other cells.
The cells switch from maintenance to wound behavior based on whether they are surrounded by other cells. Once cells become surrounded by other cells, they flip back.
The investigators found differences in gene expression between wound healing and balanced populations of cells.
"These findings have great implications for understanding cancer, where cells have too many dividing daughters,” said Phil Jones, Ph.D., senior group leader, FMedSci at Sanger Institute.
Jones added: "Mutations could change the rules of the game and load the dice in favor of dividing cells, leading to cancer. The knowledge that all dividing skin cells are the same but can switch their behavior will help us understand how DNA changes associated with cancer alter cell behavior."
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