The research group, led by Erika Matunis, Ph.D., a professor of cell biology at the Johns Hopkins University School of Medicine, has been using the fruit fly as a model living system in which to study stem cells in their natural state.
Most stem cell research is done on cells grown in the laboratory, but in real life, stem cells reside in tissues, where they are sequestered in tiny spaces known as niches.
Adult stem cells keep dividing throughout life to make various kinds of cells, like new blood cells and germ cells.
group studies such niches in fruit fly testes, the sperm-producing organs shaped like a coiled tube whose end houses a niche.
In the niche are three kinds of cells: germ line stem cells, which divide to produce sperm; somatic cyst stem cells, which make a kind of cell that helps the sperm-producing cells out; and hub cells, which make signals that keep the other two kinds of cells going.
The hub cells are not stem cells; they have settled on their final form, incapable of dividing further or changing their function -- or so everyone thought.
However, in a bid to figure out what happens when the somatic cyst stem cells are killed off, Matunis
suggested that graduate student Phylis Hétié figure out how to best do away with them, thinking the task would be straightforward.
This was a surprise, Matunis
says, and left a puzzle: Where were the new somatic stem cells coming from?
"We thought some of them looked a little bit weird," Matunis
Sometimes, the new cells made molecules that only hub cells normally make.
As the researchers looked closer, they realized that the damaged and recovered testes were making new niches.
Instead of just one pocket of stem cells, a damaged testis might have two or three.
The researchers don't know how the new niches are formed, but speculate that the original niche gets bigger as the new cells divide, then splits.
The group is doing more experiments aimed at "explaining the basics of how niches work in general," Matunis
says the research may be useful for understanding cancer, because a lot of cancer involves cancer stem cells, also known as tumor-initiating cells.
Many tumors seem to have stem cells inside them that divide to keep the tumor going.
Knowing how tumor niches support the continued growth and division of stem cells might one day offer new targets for controlling such growth.
In the study, the damage was caused deliberately, but the research suggests one way that natural damage might scatter stem cells around the body.
"We're very curious to unravel the signals that are changing when we damage this niche and it undergoes these unexpected behaviors," Matunis
Phylis Hétié, Margaret de Cuevas, Erika Matunis