Scientists at Cold Spring Harbor Laboratory have led a team of researchers that has found stem cells in the pituitary gland of mice which allow the gland to grow even after birth.
They also found that these stem cells are different from the majority of adult stem cells that trigger the initial growth of this important organ.
The results of the study also suggest a novel way that can be taken up by the pituitary gland in both adolescents and adults, to traumatic stress or to normal life changes like pregnancy.
Earlier, Grigori Enikolopov, Ph.D., an associate professor at Cold Spring Harbor Laboratory (CSHL), had known that a gene called Nestin was active in neural stem cells and they had genetically engineered mice so that the same conditions that activate Nestin in a particular cell also make it glow green under ultraviolet light. After that many such teams have used these special mice to help find adult stem cells in hair follicles, liver, muscle, and other tissues.
The pituitary gland in humans is about the size of a pea and sits at the base of the brain, where it secretes hormones that regulate various processes throughout the body. However, in mice, the gland develops in the embryo, but then has a second growth spurt.
Anatoli Gleiberman, Ph.D., a researcher in the lab of pituitary expert M. Geoff Rosenfeld at the University of California, San Diego, in collaboration with Grigori Enikolopov, aimed to look for pituitary stem cells.
They used the Nestin-tracking mice to identify candidate cells in the anterior pituitary, the section of the organ that secretes hormones and later they used other techniques to show that these are true stem cells.
Enikolopov said: "There are six main lineages in the adult pituitaryand we can demonstrate that one adult stem cell can generate all six lineages," with each cell type secreting a different hormone.
However, these cells differ from most adult stem cells.
"In most cases that we know, cells that become stem cells of the adult have been also contributing to embryonic development and continue to serve as stem cells in the adult," said Enikolopov.
The researchers showed that adult stem cells in the pituitary did not help construct the embryonic organ. They suggested that their research indicates that the adult mouse pituitary includes two similar, but not identical, types of hormone-producing cells: some that grew in the developing embryo, and some that appeared later.
They even hypothesised that having two sets of cells may let the organ respond differently to changing body conditions.
Dr. Enikolopov mentioned that hormones strongly influence human neuropsychiatric phenomena, including stress and depression that are his main research focus, saying "all are mediated through the pituitary," so changes that happen during the later growth of the gland could have lasting effects.
The study, titled, "Genetic approaches identify adult pituitary stem cells" appeared in a recent edition of the Proceedings of the National Academy of Sciences.