Embryo's heartbeat triggers blood stem cell formation

Washington, May 14 (ANI): In a breakthrough study, researchers have found that heartbeat and blood circulation play key role in the formation of blood cells in embryos.

The finding might provide an answer to why embryonic heart begins beating so early even before the tissues actually need to be infused with blood.

Researchers hope that clues about how blood forms could provide new strategies for treating blood diseases such as leukemia, immune deficiency and sickle cell anaemia.

During the study, Dr Leonard Zon, of the Division of Hematology/Oncology at Children's and Director of its Stem Cell research program used zebrafish, whose transparent embryos allow direct observation of embryonic development.

They found that compounds that modulate blood flow had a potent impact on the expression of a master regulator of blood formation, known as Runx1.

The study, appearing in journal Cell, showed that nitric oxide, whose production is increased in the presence of blood flow, is the key biochemical regulator.

Increasing nitric oxide production restored blood stem cell production in the mutant fish embryos, while inhibiting nitric oxide production led to reduced stem cell number.

"Nitric oxide appears to be a critical signal to start the process of blood stem cell production," said Zon.

"This finding connects the change in blood flow with the production of new blood cells," he added.

Another study published in Nature, showed that blood flow also triggers blood-forming or hematopoietic stem cell production in mouse embryos.

The researchers showed that shear stress - the frictional force of fluid flow on the surface of cells lining the embryonic aorta - increases the expression of master regulators of blood formation, including Runx1, and of genetic markers found in blood stem cells.

It also increased formation of colonies of progenitor cells that give rise to specific lineages of blood cells.

This showed that biomechanical forces promote blood formation.

"In learning how the heartbeat stimulates blood formation in embryos, we've taken a leap forward in understanding how to direct blood formation from embryonic stem cells in the petri dish," said lead researcher Dr George Q.

Daley, director of the Stem Cell Transplantation Program at Children's Hospital Boston. (ANI)