According to researchers from Baylor College of Medicine (BCM), hematopoietic stem cells from bone marrow divide faster in females than males. The faster generation of cells is driven by the hormone estrogen. Dr. Daisuke Nakada, assistant professor of molecular and human genetics at Baylor and a corresponding author of the report, notes, “I think this changes how we think about hematopoietic stem cells and gender, and reveals a new area of biology that these stem cells are involved.” The second corresponding author is Dr. Sean J. Morrison of the University of Texas Southwestern Medical Center in Dallas.
Nakada and colleagues have looked at the rate at which hematopoietic stems cells divide in mice and found there was a difference in female mice versus male mice. Hematopoietic stem cells are precursor cells which form other blood cells in bone marrow. Nakada notes, “No one had expected a sex difference in the blood system at the stem cell level. In short, the blood system stem cells in female mice divided at a higher rate than did those in males.”
The researchers gave male and female mice estradiol and discovered that the rate of cell division increased in both males and females. They also found that removing the ovaries of female mice decreased the rate of hematopoietic stem cells division to that of the male. Additionally, castration of male mice had no effect.
Increasing levels of estrogen in pregnant female mice increased cell division in hematopoietic stem cells as well as frequency and production of red blood cells in the spleen. The hematopoietic stem cells also expressed high levels of estrogen receptor alpha as compared to differentiated blood cells. Deletion of the estrogen receptor in hematopoietic stem cells decreased the rate of cell division in females but not in males. Moreover, receptor deletion during pregnancy decreased the rates of stem cell division and frequency as well as formation of red blood cells in the spleen. Nakada notes, “This is a totally new field”. Researchers have studied the system that protects the developing fetus attack by the mother’s immune system, whether this involves hematopoietic stem cells is unclear at this time.
Nakada plans on continuing studies to detail how estrogen and pregnancy affects hematopoietic stem cell function. He suggests that this information may help improve hematopoietic stem cell transplantation or avoid maternal and prenatal complications.