Scientists Discover Emergency Response System For Blood Formation

New blood cell formation takes place in the bone marrow. But, when there is hematopoietic stress, blood formation occurs in the spleen.

The body’s response during times of emergency when it needs more blood cells has been identified by scientists at the Children's Medical Center Research Institute at UT Southwestern (CRI).//

In a study published in Nature, researchers report that when tissue damage occurs, in times of excessive bleeding, or during pregnancy, a secondary, emergency blood-formation system is activated in the spleen.

Hematopoietic Stem Cells, the New Target for Myeloproliferative Disorders
A new therapeutic target for certain kinds of myeloproliferative disease has been discovered by the Stem Cell Physiopathology group at the CNIC.

‘The blood forming stem cells in the bone marrow migrate to the spleen during hematopoietic stress to maintain normal blood count.’

"Hematopoietic, or blood-forming, stem cells reside mainly in the bone marrow, and most new blood cell formation occurs within the bone marrow under normal circumstances. But when there is hematopoietic stress, blood cell formation expands to the spleen," said Dr. Sean Morrison, CRI Director and Mary McDermott Cook Chair in Pediatric Genetics at UT Southwestern Medical Center.

"Blood-forming stem cells migrate from the bone marrow to the spleen, which becomes a hematopoietic organ where blood formation then occurs."

Normally, there are very few blood-forming stem cells in the spleen. But the cells that create the supporting environment for these stem cells are present in the spleen, ready to respond during times of hematopoietic stress and to receive an influx of blood-forming stem cells from the bone marrow.

New Method of Converting IPSCs into Hematopoietic Stem Cells for Disease Modeling Identified
Researchers have identified a new way through which induced pluripotent stem cells (iPSCs) can be converted into hematopoietic stem cells.

In characterizing the microenvironment, or niche, which supports blood formation in the spleen, the CRI research team used mouse models to examine the expression patterns of two known niche cell factors, stem cell factor (SCF) and CXCL12.

The researchers found that the blood-forming microenvironment in the spleen is found near sinusoidal blood vessels and is created by endothelial cells and perivascular stromal cells - just like the microenvironment in the bone marrow.

Functionally Younger Makeover of Aged Hematopoietic Stem Cells
Aged hematopoietic stem cells has been rejuvenated to be functionally younger, offering intriguing clues into how medicine may soon avert some of the ailments of old age, aver researchers.

"Under emergency conditions, the endothelial cells and perivascular stromal cells that reside in the spleen are induced to proliferate, so they can sustain all the new blood-forming stem cells that migrate into the spleen," said Dr. Morrison, who is also a CPRIT Scholar in Cancer Research and a Howard Hughes Medical Institute Investigator.

"We determined that this process in the spleen is physiologically important for responding to hematopoietic stress; without it, the mice we studied could not maintain normal blood cell counts during pregnancy or quickly regenerate blood cell counts after bleeding or chemotherapy."

Autologous Hematopoietic Cell Transplant (HCT) Sends Multiple Sclerosis into Remission
For patients with relapsing-remitting multiple sclerosis, high-dose immunosuppressive therapy with autologous hematopoietic cell transplant is related with remission and improvement.

Based on this new information about the spleen's emergency backup role for blood cell formation, therapeutic interventions could be developed in the future to enhance blood formation following chemotherapy or bone marrow transplantation and thus accelerate the recovery of blood cell counts.

Source-Eurekalert