Ruohola-Baker added that stem cells hold high hope in regenerative medicine: tapping into the ways cells repair the body to create therapies to fix or replace injured tissues. She mentioned that it is thought that most, if not all, adult tissues contain stem cells.
Through self-renewing division," she explained, "stem cells replenish the stem cell pool. They also produce progeny that change into other, specialized cells. Importantly, stem cells have the capacity to divide throughout the life of an organism. They do so through regulated external stimuli that may initiate from stem cells. This regulation of cell division needs to be tightly controlled." Too little division results in poor maintenance of tissues, while too much can result in tumors or other malignancies.
Her lab used the germline stem cell niche, found in the ovaries of fruit flies, as a model system. The production of fruit fly eggs depends on the presence of a renewable source of stem cells in the ovary of the adult fruit fly.
Inside the fruit fly ovary are structures called germarium which contain tiny cradles made of cap cells that nurture stem cells. Each such cradle contains two to three stem cells preparing to become fly eggs that are cuddled in a niche composed of three to six cap cells. Cap cells adhere to stem cells and this close contact may allow cap cells to play critical roles in communicating with stem cells.
The research team looked at a kind of signaling that usually depends on direct contact between cells, called the Notch pathway. The Notch protein is like a trigger poking out of a cell that can activate a mechanism inside the cell. When this trigger is pulled by proteins, called Delta and Serrate, from another cell, proteins are freed inside the cell to travel to the cell nucleus and turn on various genes.
According to Ruohula-Baker, the Notch pathway plays an important role in many stem-cell niches, including tho
Source:University of Washington