Bacteria have the ability to convert the host tissue cells that they infect to become like stem cells that can then differentiate into virtually any other type of cell, thereby enabling the bugs to spread to other parts of the body.
Researchers at the University of Edinburgh made this remarkable discovery while studying mice infected with bacteria that cause leprosy, an infectious disease that attacks the nerve system.
They propose the finding will help stem cell researchers use similar mechanisms to develop new stem cell treatments for degenerative conditions.
They write about their findings in the 17 January issue of the journal Cell.
Senior researcher Anura Rambukana, Chair of Regeneration Biology at Edinburgh, says in a press statement:
“Bacterial infections can completely change a cell’s make up, which could have a wide-range of implications, including in stem cell research.”
While studying what happens when the leprosy bacterium infects mice, Rambukana and colleagues found that in the early stages of infection, the bug protects itself from the host immune system by hiding in Schwann cells, the cells that support and protect the nerve cells that carry signals.
But once the infection is established, the bacterium then sets about reprogramming the Schwann cells to become like stem cells.
This is how the disease sets in and causes nerve damage: once the Schwann cells are reprogrammed into stem cells they lose their ability to protect nerve cells, which in turn prevents nerve signals travelling to the brain.
Like typical stem cells, the converted cells then have the potential to differentiate into other cell types, such as muscle cells. This helps the bacterium spread from the nerve system to other tissue.
The researchers were also surprised to find that the bacterium is able to fool the immune system into helping it spread: by secreting proteins called chemokines that summon immune cells, which then pick up the bacterium and spread the infection.
They believe these mechanisms used by the leprosy bacterium could also exist in other infectious diseases.
Rambukkana says:
“Greater understanding of how this occurs could help research to diagnose bacterial infectious diseases, such as leprosy, much earlier.”
Rambukkana says they are intrigued by their discovery because it is the first time they’ve seen functioning adult tissue being reprogrammed into stem cells by a natural bacterial infection. This is of interest to stem cell researchers because such a process does not carry the risk of creating tumors, which is a real risk when scientists try to programme cells to become pluripotent stem cells.
“Potentially you could use the bacteria to change the flexibility of cells, turning them into stem cells and then use the standard antibiotics to kill the bacteria completely so that the cells could then be transplanted safely to tissue that has been damaged by degenerative disease,” suggests Rambukkana.
Rob Buckle, Head of Regenerative Medicine at the Medical Research Council, says:
“In future, this knowledge may help scientists to improve the safety and utility of lab-produced pluripotent stem cells and help drive the development of new regenerative therapies for a range of human diseases, which are currently impossible to treat.”
The research was funded by the US National Institutes of Health.
Written by Catharine Paddock PhD