Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Embryo’s Heartbeat Drives Blood Stem Cell Formation

Biologists have long wondered why the embryonic heart begins beating so early, before the tissues actually need to be infused with blood.

Two groups of researchers from Children’s Hospital Boston, Brigham and Women’s Hospital, and the Harvard Stem Cell Institute (HSCI) -– presenting multiple lines of evidence from zebrafish, mice and mouse embryonic stem cells -– provide an intriguing answer: A beating heart and blood flow are necessary for development of the blood system, which relies on mechanical stresses to cue its formation.

Their studies, published online by the journals Cell and Nature, respectively, on May 13, together offer clues that may help in treating blood diseases such as leukemia, immune deficiency and sickle cell anemia, suggesting new ways scientists can make the types of blood cells a patient needs. This would help patients who require marrow or cord blood transplants, who do not have a perfect donor match.

One team, led by Leonard Zon, MD, 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. Publishing in Cell, Zon and colleagues discovered that compounds that modulate blood flow had a potent impact on the expression of a master regulator of blood formation, known as Runx1, which is also a recognized marker for the blood stem cells that give rise to all the cell types in the blood system.

Confirming this observation, a strain of mutant embryos that lacked a heartbeat and blood circulation exhibited severely reduced numbers of blood stem cells. Further work 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.

Zon and colleagues went on to demonstrate that nitric oxide production was coupled to the initiation of blood stem cell formation across vertebrate species. Suppression of nitric oxide production in mice, by either genetic or chemical means, similarly reduced the number of functional Runx1-expressing blood stem cells.

“Nitric oxide appears to be a critical signal to start the process of blood stem cell production,” says Zon, who is also affiliated with the HSCI. “This finding connects the change in blood flow with the production of new blood cells.”

The second team, publishing in Nature, was led by George Q. Daley, MD, PhD, director of the Stem Cell Transplantation Program at Children’s Hospital Boston, and Guillermo García-Cardeña, director of the Laboratory for Systems Biology of the Center for Excellence in Vascular Biology at Brigham and Women's Hospital, along with scientists from the Indiana University School of Medicine. Intrigued by the appearance of blood progenitors in the wall of the developing aorta soon after the heart starts beating, they investigated the effects of mechanical stimulation on blood formation in cultured mouse embryonic stem cells.

They 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. Shear stress also increased formation of colonies of progenitor cells that give rise to specific lineages of blood cells (red cells, lymphocytes, etc.). These findings demonstrate that biomechanical forces promote blood formation.

Daley, García-Cardeña and colleagues also studied mouse embryos with a mutation that prevented initiation of the heartbeat. These embryos had a sharp reduction in progenitor blood cell colonies, along with reduced expression of genetic markers of blood stem cells. When specific cells from the mutant embryos were exposed in vitro to shear stress, markers of blood stem cells and numbers of blood cell colonies were restored.

Finally, the team showed that when nitric oxide production was inhibited, in both cell cultures and live mouse embryos, the effects of shear stress on blood progenitor colony formation were reduced.

“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,” says Daley, who is also affiliated with the HSCI.

“These observations reveal an unexpected role for biomechanical forces in embryonic development,” adds García-Cardeña. “Our work highlights a critical link between the formation of the cardiovascular and hematopoietic systems.”

The authors of the two papers speculate that drugs that mimic the effects of embryonic blood flow on blood precursor cells, or molecules involved in nitric oxide signaling, might be therapeutically beneficial for patients with blood diseases. For example, nitric oxide could be used to grow and expand blood stem cells either in the culture dish or in patients after transplantation.

Trista North, PhD, and Wolfram Goessling, MD, PhD, now principal faculty at HSCI and assistant professors at Beth Israel Deaconess Medical Center and Brigham and Women’s Hospital, respectively, were first authors on the Cell paper. Luigi Adamo, MD, of Brigham and Women’s Hospital and Olaia Naveiras, MD, PhD of Children’s Hospital Boston and Brigham and Women’s Hospital were first authors on the Nature paper. The studies were supported by the National Institutes of Health, the NIH Director’s Pioneer Award, the Burroughs Wellcome Fund Clinical Scientist Award in Translational Research and the Howard Hughes Medical Institute (Zon and Daley are HHMI investigators).

Children's Hospital Boston is home to the world's largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since 1869. More than 500 scientists, including eight members of the National Academy of Sciences, 11 members of the Institute of Medicine and 12 members of the Howard Hughes Medical Institute comprise Children's research community. Founded as a 20-bed hospital for children, Children's Hospital Boston today is a 397-bed comprehensive center for pediatric and adolescent health care grounded in the values of excellence in patient care and sensitivity to the complex needs and diversity of children and families. Children's also is the primary pediatric teaching affiliate of Harvard Medical School.

Brigham and Women’s Hospital is an international leader in basic, clinical and translational research on human diseases, involving more than 860 physician-investigators and renowned biomedical scientists and faculty.

The Harvard Stem Cell Institute is a scientific collaborative established to fulfill the promise of stem cell biology as the basis for cures and treatments for a wide range of chronic medical conditions.

Bess Andrews | Newswise Science News
Further information:

More articles from Life Sciences:

nachricht Molecular doorstop could be key to new tuberculosis drugs
20.03.2018 | Rockefeller University

nachricht Modified biomaterials self-assemble on temperature cues
20.03.2018 | Duke University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Physicists made crystal lattice from polaritons

20.03.2018 | Physics and Astronomy

Mars' oceans formed early, possibly aided by massive volcanic eruptions

20.03.2018 | Physics and Astronomy

Thawing permafrost produces more methane than expected

20.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>