We know that most of the blood in our body is made from hematopoietic stem cells (blood stem cells).
However, research results suggest that this myth in the scientific community may not be true.
A completely different group of blood progenitor cells that do not differentiate from previously known hematopoietic stem cells has been found in a mouse model.
In other words, contrary to what has been known so far, it means that there is not one type of ‘mother cell’ that makes blood, but two.
As a result of the mouse experiment, in human terms, almost all of the blood from fetal to adolescence was made from newly discovered progenitor cells.
Scientists are trying to determine whether these ’embryonic pluripotent progenitor cells’ (eMPPs) found in mice function the same in humans.
If so, the findings could be significant enough to rewrite biology textbooks, the team stressed.
In particular, it is said to be of great help in treating blood cancer in children, bone marrow transplantation, and strengthening immunity in old age.
The results of this study conducted by scientists at Boston Children’s Hospital in the United States were published as a paper in the journal Nature on the 15th (local time).
The Boston Children’s Hospital, a major educational hospital at Harvard Medical School, is considered one of the best children’s hospitals in the United States.
The research team manipulated the gene of a mouse model using the cell ‘barcoding technique’ developed several years ago.
A unique gene sequence (base sequence) is inserted into mouse embryonic cells using the ‘gene translocation enzyme’ used for CRISPR gene editing.
In this way, the same sequence was inserted into the DNA of all cells differentiated from these embryonic cells, so it was possible to trace the origin of blood cells by type.
Professor Fernando Camargo of the Stem Cell Research Center at Harvard Medical School, who is the corresponding author of the paper, said, “There was no such technology in the past, and no one suspected that all blood cells are derived from stem cells. will,” he said.
Lymphocytes such as T cells and B cells, which play an important role in the immune response, are fundamentally different from what was previously thought.
In fact, most lymphocytes are not derived from blood stem cells, but from newly discovered eMPPs.
The researchers noted a decrease in eMPPs in mice equivalent to middle-aged humans. It seemed to be a hypothesis that explains why the immune system weakens with age.
In a similar vein, attention was focused on why eMPPs were given when they reached middle age.
It was thought that if the eMPPs were properly manipulated, the immune system could be rejuvenated.
The team also proposed several theoretically possible methods.
For example, prolonging the lifespan of eMPPs using growth factors or immune signaling substances, or making blood stem cells similar to eMPPs through gene therapy, can be considered.
This discovery also raises hopeful prospects for a new treatment for blood cancer.
First, the research team believes that myeloid leukemia and lymphocytic leukemia may have different roots.
Myeloid leukemia, which is common in the elderly, originates from blood stem cells, but lymphocytic leukemia, which occurs more frequently in children, is likely to result from eMPPs.
The research team is examining the impact of leukemia-causing gene mutations on mouse hematopoietic stem cells and eMPPs, respectively.
I wonder if the discovery of another blood stem cell will revolutionize bone marrow transplantation.
When the scientists transplanted bone marrow into mice, they found that eMPPs survived only a few weeks before dying.
If gene therapy can induce long-term grafting of eMPPs, a much more effective bone marrow transplant will be possible.
“EMPPs are more common in young bone marrow donors than blood stem cells,” said Professor Camargo.