NYSCF Innovator Explores Interactions Between Blood Stem Cells And Their Niches

Our bodies need to produce about one hundred billion new blood cells a day to maintain proper circulation. We do this through a process called hematopoiesis, in which hematopoietic (blood) stem cells differentiate to create new platelets, red blood cells, T-cells, etc.

A new study from NYSCF — Druckenmiller Fellow Alumna Sandra Pinho, PhD, and collaborators at the Albert Einstein College of Medicine examined the structures in which hematopoiesis takes place and how these structures interact with blood stem cells.

We know that hematopoiesis takes place in the bone marrow—specifically, in little environments called “stem cell niches”. But while some studies have suggested that blood stem cells are distributed relatively evenly across niches, others suggest that different niches hold and regulate certain types of blood stem cells.

Some blood stem cells are lineage-biased, meaning they are more likely to become one type of blood cell than another, and the researchers were interested in studying whether these lineage-biased cells were regulated by different niches. To do this, they marked blood stem cells biased to either become lymphoid or myeloid cells with a protein called von Willebrand factor and then observed the cell’s behavior within the bone marrow of mice.

What they found was that each of these lineage-biased blood stem cells occupies a different niche. Myeloid-biased cells are located in niches occupied by megakaryocytes (bone marrow cells that make platelets), and lymphoid-biased cells are located in niches occupied by arterioles (a branch of an artery that leads into capillaries).

The team also found that, in some cases, the niches regulated how the blood stem cells differentiate. By removing megakaryocytes from their niches, the myeloid-biased cells lost their myeloid preference, instead differentiating into equal proportions of myeloid and lymphoid cells. But deletion of arteriolar cells from their niches did not have an effect on the lymphoid-biased cells, which still differentiated into mostly lymphoid cells.

This study helps scientists further understand the behavior of blood stem cells and how niches influence their fate. For more information, check out the paper in Developmental Cell.