NOV 21, 2021 7:19 AM PST

For Blood Stem Cells, Size Matters

WRITTEN BY: Carmen Leitch

The size of cells can vary widely from one species to another; the cells of phytoplankton are about one micron while frog oocytes can reach one millimeter. Even within one organism, there can be huge differences; human neurons can be huge compared to red blood cells, for example. But most specific cell types have to maintain a particular size, which ensures that they function efficiently. For example, blood cells have to be really small so they can fit into capillaries, while neurons may have to link distant regions, like the brain and peripheral organs. Thus, it's important for cells to control their size, which is linked to the regulation of growth and division.

Aged cells that have stopped dividing, called senescent cells, are known to get larger. When cells divide, they may pick up mutations in their DNA. Those mutations can be identified and repaired by the cell, but that process interrupts division and delays it, during which time cells have been observed getting bigger. MIT researchers wanted to know if this was linked to a decline in cell function. They have now learned more about how and why blood stem cells remain so small. The findings have been reported in Science Advances.

In this study, if the investigators caused DNA damage in blood stem cells, they found that the cells got larger and lost their normal function, which is to replenish red blood cells in a process called hematopoiesis.. If that genetic damage was induced but the blood stem cells were also prevented from getting larger with a chemical, the small, but damaged cells could still function normally, and they were able to generate new blood cells unlike cells that had gotten larger.

In another set of experiments, a mutation was introduced that made the blood stem cells too big. Those cells stopped performing normally. But they weren't worn out; when the mutation was corrected, the cells returned to their normal size, and they began to behave normally again.

“This is striking evidence supporting the model that size is important for functionality of stem cells,” said lead study author Jette Lengefeld, PhD, a former MIT postdoc now at the University of Helsinki. “When we damage the stem cells’ DNA but keep them small during the damage, they retain their functionality. And if we reduce the size of large stem cells, we can restore their function.”

Blood stem cells also seem to get bigger as they grow older, which helps explain why they begin to decline as they age. Cellular enlargement is a part of aging, the researchers suggested, and it may be possible to delay the onset of diseases that are related to aging by targeting cell size.

In a mouse model, the researchers used a chemical to prevent the blood stem cells from getting larger. The cells stayed small even in mice that were three years old, and continued to function normally as young stem cells would. That chemical, called rapamycin, could have beneficial effects in people, suggested Lengefeld.

“If we find drugs that are specific in making large blood stem cells smaller again, we can test whether this improves the health of people who suffer from problems with their blood system, like anemia and a reduced immune system, or maybe even help people with leukemia,” she added.

Image credit: Pixabay

This work was confirmed in a intestinal organoid model; old stem cells were less able to grow functional organoids compared to young stem cells.

“That suggested that this relationship between cell size and function is conserved in stem cells, and that cellular size is a marker of stem cell function,” Lengefeld said.

Sources: Massachusetts Institute of Technology, Science Advances

About the Author
BS
Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
MAY 19, 2022
Neuroscience
Fruits and Vegetables May Reduce ADHD Symptoms in Children
MAY 19, 2022
Fruits and Vegetables May Reduce ADHD Symptoms in Children
Diets rich in fruits and vegetables may help reduce inattention issues in children with Attention deficit hyperactivity ...
JUN 10, 2022
Immunology
Is Autoimmunity Related to Schizophrenia?
JUN 10, 2022
Is Autoimmunity Related to Schizophrenia?
Schizophrenia is estimated to impact around 24 million people, which is about 1 in 300 people worldwide. This poorly und ...
JUN 12, 2022
Cell & Molecular Biology
Self-Healing, Synthetic Skin is Grown Directly on a Robotic Finger
JUN 12, 2022
Self-Healing, Synthetic Skin is Grown Directly on a Robotic Finger
With robotics and tissue culture skills, scientists have engineered a type of synthetic skin tissue that they successful ...
JUN 25, 2022
Immunology
A Link Between Hair Growth and the Immune System is Revealed
JUN 25, 2022
A Link Between Hair Growth and the Immune System is Revealed
Salk Institute researchers studying alopecia have learned more about the link between immunity and hair growth.
JUN 30, 2022
Cell & Molecular Biology
Zika- and Dengue-Infected Humans are More Attractive to Mosquitoes
JUN 30, 2022
Zika- and Dengue-Infected Humans are More Attractive to Mosquitoes
Researchers have found that when people have a Zika or dengue virus infection, they release a molecule that can attract ...
JUL 01, 2022
Clinical & Molecular DX
Could Temperature Fight Obesity? Study in Mice Suggests Cold Exposure Could
JUL 01, 2022
Could Temperature Fight Obesity? Study in Mice Suggests Cold Exposure Could
Mammals, including humans, have at least two different types of fat tissue. White fat is the tissue where energy is prim ...
Loading Comments...