22 January 2013

Bacteria’s Hidden Weapon Could Pave Way for Stem Cell Treatments

A discovery about the way in which bugs spread throughout the body could help to develop stem cell treatments. Researchers from the Medical Research Council (MRC) Centre for Regenerative Medicine, at the University of Edinburgh, have found that leprosy bacteria are able to change the make-up of supporting cells of the nervous system, called Schwann cells, so that they take on the properties of stem cells.

Because stem cells can develop into any of the different cell types in the body – including liver and brain cells – mimicking this process could aid research into a range of degenerative conditions and could help scientists develop new tools for regenerative medicine.

Scientists made the discovery studying bacteria that cause leprosy, an infectious neurodegenerative disease. The study, carried out in mice, found that in the early stages of infection, the bacteria were able to protect themselves from the body’s immune system by hiding in Schwann cells. Once the infection was fully established, the bacteria were able to convert the Schwann cells to become like stem cells.

Like certain stem cells in the body, they have the potential to become other cell types, for instance muscle cells. This enabled the bacteria to spread to tissues in the body. Because these stem cells are generated by normal body cells immune system does not recognise them as foreign and thus they can spread the infection without being attacked, and thus more effectively.

The bacteria-generated stem cells also have another unexpected characteristic. They can secrete specialised proteins – called chemokines – that attract immune cells, which in turn pick up the bacteria and spread the infection. Scientists believe these mechanisms, used by leprosy bacteria, could exist in other infectious diseases. The study is published in the journal Cell.

Professor Anura Rambukkana, of the MRC Centre for Regenerative Medicine at the University of Edinburgh, who led the research, said:

“Bacterial infections can completely change a cell’s make up, which could have a wide-range of implications, including in stem cell research. We have found a new weapon in a bacteria’s armoury that enables them to spread effectively in the body by converting infected cells to stem cells. Greater understanding of how this occurs could help research to diagnose bacterial infectious diseases, such as leprosy, much earlier.

“This is very intriguing as it is the first time that we have seen that functional adult tissue cells can be reprogrammed into stem cells by natural bacterial infection, which also does not carry the risk of creating tumorous 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.”

Dr Rob Buckle, Head of Regenerative Medicine at the MRC, added:

“This ground-breaking new research shows that bacteria are able to sneak under the radar of the immune system by hijacking a naturally occurring mechanism to ‘reprogramme’ cells in order to make them look and behave like stem cells. This discovery is important not just for our understanding and treatment of bacterial disease, but for the rapidly progressing field of regenerative medicine. 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.”

Professor Rambukkana, who is Chair of Regeneration Biology at the MRC Centre for Regenerative Medicine, is also a member of the University’s Centre for Neuroregeneration and Infectious Diseases. The study, carried out in Professor Rambukkana’s laboratories at the University of Edinburgh and the Rockefeller University, was funded by the US National Institutes of Health.

The paper, ‘Reprogramming Adult Schwann Cells to Stem Cell-like Cells by Leprosy Bacilli Promotes Dissemination of Infection’, by T Masaki et al, is published in Cell.